/**
 * Compiler implementation of the
 * $(LINK2 http://www.dlang.org, D programming language).
 *
 * Copyright:   Copyright (c) 1999-2017 by Digital Mars, All Rights Reserved
 * Authors:     $(LINK2 http://www.digitalmars.com, Walter Bright)
 * License:     $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 * Source:      $(DMDSRC _mtype.d)
 */

module ddmd.mtype;

import core.checkedint;
import core.stdc.stdarg;
import core.stdc.stdio;
import core.stdc.stdlib;
import core.stdc.string;

import ddmd.access;
import ddmd.aggregate;
import ddmd.aliasthis;
import ddmd.arrayop;
import ddmd.arraytypes;
import ddmd.gluelayer;
import ddmd.complex;
import ddmd.dcast;
import ddmd.dclass;
import ddmd.declaration;
import ddmd.denum;
import ddmd.dimport;
import ddmd.dmangle;
import ddmd.dscope;
import ddmd.dstruct;
import ddmd.dsymbol;
import ddmd.dtemplate;
import ddmd.errors;
import ddmd.expression;
import ddmd.func;
import ddmd.globals;
import ddmd.hdrgen;
import ddmd.id;
import ddmd.identifier;
import ddmd.imphint;
import ddmd.init;
import ddmd.opover;
import ddmd.root.ctfloat;
import ddmd.root.outbuffer;
import ddmd.root.rmem;
import ddmd.root.rootobject;
import ddmd.root.stringtable;
import ddmd.sideeffect;
import ddmd.target;
import ddmd.tokens;
import ddmd.visitor;

enum LOGDOTEXP = 0;         // log ::dotExp()
enum LOGDEFAULTINIT = 0;    // log ::defaultInit()

extern (C++) __gshared int Tsize_t = Tuns32;
extern (C++) __gshared int Tptrdiff_t = Tint32;

enum SIZE_INVALID = (~cast(d_uns64)0);   // error return from size() functions


/***************************
 * Return !=0 if modfrom can be implicitly converted to modto
 */
bool MODimplicitConv(MOD modfrom, MOD modto) pure nothrow @nogc @safe
{
    if (modfrom == modto)
        return true;

    //printf("MODimplicitConv(from = %x, to = %x)\n", modfrom, modto);
    auto X(T, U)(T m, U n)
    {
        return ((m << 4) | n);
    }

    switch (X(modfrom & ~MODshared, modto & ~MODshared))
    {
    case X(0, MODconst):
    case X(MODwild, MODconst):
    case X(MODwild, MODwildconst):
    case X(MODwildconst, MODconst):
        return (modfrom & MODshared) == (modto & MODshared);

    case X(MODimmutable, MODconst):
    case X(MODimmutable, MODwildconst):
        return true;
    default:
        return false;
    }
}

/***************************
 * Return MATCHexact or MATCHconst if a method of type '() modfrom' can call a method of type '() modto'.
 */
MATCH MODmethodConv(MOD modfrom, MOD modto) pure nothrow @nogc @safe
{
    if (modfrom == modto)
        return MATCHexact;
    if (MODimplicitConv(modfrom, modto))
        return MATCHconst;

    auto X(T, U)(T m, U n)
    {
        return ((m << 4) | n);
    }

    switch (X(modfrom, modto))
    {
    case X(0, MODwild):
    case X(MODimmutable, MODwild):
    case X(MODconst, MODwild):
    case X(MODwildconst, MODwild):
    case X(MODshared, MODshared | MODwild):
    case X(MODshared | MODimmutable, MODshared | MODwild):
    case X(MODshared | MODconst, MODshared | MODwild):
    case X(MODshared | MODwildconst, MODshared | MODwild):
        return MATCHconst;

    default:
        return MATCHnomatch;
    }
}

/***************************
 * Merge mod bits to form common mod.
 */
MOD MODmerge(MOD mod1, MOD mod2) pure nothrow @nogc @safe
{
    if (mod1 == mod2)
        return mod1;

    //printf("MODmerge(1 = %x, 2 = %x)\n", mod1, mod2);
    MOD result = 0;
    if ((mod1 | mod2) & MODshared)
    {
        // If either type is shared, the result will be shared
        result |= MODshared;
        mod1 &= ~MODshared;
        mod2 &= ~MODshared;
    }
    if (mod1 == 0 || mod1 == MODmutable || mod1 == MODconst || mod2 == 0 || mod2 == MODmutable || mod2 == MODconst)
    {
        // If either type is mutable or const, the result will be const.
        result |= MODconst;
    }
    else
    {
        // MODimmutable vs MODwild
        // MODimmutable vs MODwildconst
        //      MODwild vs MODwildconst
        assert(mod1 & MODwild || mod2 & MODwild);
        result |= MODwildconst;
    }
    return result;
}

/*********************************
 * Store modifier name into buf.
 */
void MODtoBuffer(OutBuffer* buf, MOD mod)
{
    switch (mod)
    {
    case 0:
        break;

    case MODimmutable:
        buf.writestring(Token.toString(TOKimmutable));
        break;

    case MODshared:
        buf.writestring(Token.toString(TOKshared));
        break;

    case MODshared | MODconst:
        buf.writestring(Token.toString(TOKshared));
        buf.writeByte(' ');
        goto case; /+ fall through +/
    case MODconst:
        buf.writestring(Token.toString(TOKconst));
        break;

    case MODshared | MODwild:
        buf.writestring(Token.toString(TOKshared));
        buf.writeByte(' ');
        goto case; /+ fall through +/
    case MODwild:
        buf.writestring(Token.toString(TOKwild));
        break;

    case MODshared | MODwildconst:
        buf.writestring(Token.toString(TOKshared));
        buf.writeByte(' ');
        goto case; /+ fall through +/
    case MODwildconst:
        buf.writestring(Token.toString(TOKwild));
        buf.writeByte(' ');
        buf.writestring(Token.toString(TOKconst));
        break;

    default:
        assert(0);
    }
}

/*********************************
 * Return modifier name.
 */
char* MODtoChars(MOD mod)
{
    OutBuffer buf;
    buf.reserve(16);
    MODtoBuffer(&buf, mod);
    return buf.extractString();
}

/************************************
 * Convert MODxxxx to STCxxx
 */
StorageClass ModToStc(uint mod) pure nothrow @nogc @safe
{
    StorageClass stc = 0;
    if (mod & MODimmutable)
        stc |= STCimmutable;
    if (mod & MODconst)
        stc |= STCconst;
    if (mod & MODwild)
        stc |= STCwild;
    if (mod & MODshared)
        stc |= STCshared;
    return stc;
}

/************************************
 * Strip all parameter's idenfiers and their default arguments for merging types.
 * If some of parameter types or return type are function pointer, delegate, or
 * the types which contains either, then strip also from them.
 */
private Type stripDefaultArgs(Type t)
{
    static Parameters* stripParams(Parameters* parameters)
    {
        Parameters* params = parameters;
        if (params && params.dim > 0)
        {
            foreach (i; 0 .. params.dim)
            {
                Parameter p = (*params)[i];
                Type ta = stripDefaultArgs(p.type);
                if (ta != p.type || p.defaultArg || p.ident)
                {
                    if (params == parameters)
                    {
                        params = new Parameters();
                        params.setDim(parameters.dim);
                        foreach (j; 0 .. params.dim)
                            (*params)[j] = (*parameters)[j];
                    }
                    (*params)[i] = new Parameter(p.storageClass, ta, null, null);
                }
            }
        }
        return params;
    }

    if (t is null)
        return t;

    if (t.ty == Tfunction)
    {
        TypeFunction tf = cast(TypeFunction)t;
        Type tret = stripDefaultArgs(tf.next);
        Parameters* params = stripParams(tf.parameters);
        if (tret == tf.next && params == tf.parameters)
            goto Lnot;
        tf = cast(TypeFunction)tf.copy();
        tf.parameters = params;
        tf.next = tret;
        //printf("strip %s\n   <- %s\n", tf.toChars(), t.toChars());
        t = tf;
    }
    else if (t.ty == Ttuple)
    {
        TypeTuple tt = cast(TypeTuple)t;
        Parameters* args = stripParams(tt.arguments);
        if (args == tt.arguments)
            goto Lnot;
        t = t.copy();
        (cast(TypeTuple)t).arguments = args;
    }
    else if (t.ty == Tenum)
    {
        // TypeEnum::nextOf() may be != NULL, but it's not necessary here.
        goto Lnot;
    }
    else
    {
        Type tn = t.nextOf();
        Type n = stripDefaultArgs(tn);
        if (n == tn)
            goto Lnot;
        t = t.copy();
        (cast(TypeNext)t).next = n;
    }
    //printf("strip %s\n", t.toChars());
Lnot:
    return t;
}

enum TFLAGSintegral     = 1;
enum TFLAGSfloating     = 2;
enum TFLAGSunsigned     = 4;
enum TFLAGSreal         = 8;
enum TFLAGSimaginary    = 0x10;
enum TFLAGScomplex      = 0x20;

private Expression semanticLength(Scope* sc, TupleDeclaration tup, Expression exp)
{
    ScopeDsymbol sym = new ArrayScopeSymbol(sc, tup);
    sym.parent = sc.scopesym;

    sc = sc.push(sym);
    sc = sc.startCTFE();
    exp = exp.semantic(sc);
    sc = sc.endCTFE();
    sc.pop();

    return exp;
}

/**************************
 * This evaluates exp while setting length to be the number
 * of elements in the tuple t.
 */
private Expression semanticLength(Scope* sc, Type t, Expression exp)
{
    if (t.ty == Ttuple)
    {
        ScopeDsymbol sym = new ArrayScopeSymbol(sc, cast(TypeTuple)t);
        sym.parent = sc.scopesym;
        sc = sc.push(sym);
        sc = sc.startCTFE();
        exp = exp.semantic(sc);
        sc = sc.endCTFE();
        sc.pop();
    }
    else
    {
        sc = sc.startCTFE();
        exp = exp.semantic(sc);
        sc = sc.endCTFE();
    }
    return exp;
}

enum ENUMTY : int
{
    Tarray,     // slice array, aka T[]
    Tsarray,    // static array, aka T[dimension]
    Taarray,    // associative array, aka T[type]
    Tpointer,
    Treference,
    Tfunction,
    Tident,
    Tclass,
    Tstruct,
    Tenum,

    Tdelegate,
    Tnone,
    Tvoid,
    Tint8,
    Tuns8,
    Tint16,
    Tuns16,
    Tint32,
    Tuns32,
    Tint64,

    Tuns64,
    Tfloat32,
    Tfloat64,
    Tfloat80,
    Timaginary32,
    Timaginary64,
    Timaginary80,
    Tcomplex32,
    Tcomplex64,
    Tcomplex80,

    Tbool,
    Tchar,
    Twchar,
    Tdchar,
    Terror,
    Tinstance,
    Ttypeof,
    Ttuple,
    Tslice,
    Treturn,

    Tnull,
    Tvector,
    Tint128,
    Tuns128,
    TMAX,
}

alias Tarray = ENUMTY.Tarray;
alias Tsarray = ENUMTY.Tsarray;
alias Taarray = ENUMTY.Taarray;
alias Tpointer = ENUMTY.Tpointer;
alias Treference = ENUMTY.Treference;
alias Tfunction = ENUMTY.Tfunction;
alias Tident = ENUMTY.Tident;
alias Tclass = ENUMTY.Tclass;
alias Tstruct = ENUMTY.Tstruct;
alias Tenum = ENUMTY.Tenum;
alias Tdelegate = ENUMTY.Tdelegate;
alias Tnone = ENUMTY.Tnone;
alias Tvoid = ENUMTY.Tvoid;
alias Tint8 = ENUMTY.Tint8;
alias Tuns8 = ENUMTY.Tuns8;
alias Tint16 = ENUMTY.Tint16;
alias Tuns16 = ENUMTY.Tuns16;
alias Tint32 = ENUMTY.Tint32;
alias Tuns32 = ENUMTY.Tuns32;
alias Tint64 = ENUMTY.Tint64;
alias Tuns64 = ENUMTY.Tuns64;
alias Tfloat32 = ENUMTY.Tfloat32;
alias Tfloat64 = ENUMTY.Tfloat64;
alias Tfloat80 = ENUMTY.Tfloat80;
alias Timaginary32 = ENUMTY.Timaginary32;
alias Timaginary64 = ENUMTY.Timaginary64;
alias Timaginary80 = ENUMTY.Timaginary80;
alias Tcomplex32 = ENUMTY.Tcomplex32;
alias Tcomplex64 = ENUMTY.Tcomplex64;
alias Tcomplex80 = ENUMTY.Tcomplex80;
alias Tbool = ENUMTY.Tbool;
alias Tchar = ENUMTY.Tchar;
alias Twchar = ENUMTY.Twchar;
alias Tdchar = ENUMTY.Tdchar;
alias Terror = ENUMTY.Terror;
alias Tinstance = ENUMTY.Tinstance;
alias Ttypeof = ENUMTY.Ttypeof;
alias Ttuple = ENUMTY.Ttuple;
alias Tslice = ENUMTY.Tslice;
alias Treturn = ENUMTY.Treturn;
alias Tnull = ENUMTY.Tnull;
alias Tvector = ENUMTY.Tvector;
alias Tint128 = ENUMTY.Tint128;
alias Tuns128 = ENUMTY.Tuns128;
alias TMAX = ENUMTY.TMAX;

alias TY = ubyte;

enum MODFlags : int
{
    MODconst        = 1,    // type is const
    MODimmutable    = 4,    // type is immutable
    MODshared       = 2,    // type is shared
    MODwild         = 8,    // type is wild
    MODwildconst    = (MODwild | MODconst), // type is wild const
    MODmutable      = 0x10, // type is mutable (only used in wildcard matching)
}

alias MODconst = MODFlags.MODconst;
alias MODimmutable = MODFlags.MODimmutable;
alias MODshared = MODFlags.MODshared;
alias MODwild = MODFlags.MODwild;
alias MODwildconst = MODFlags.MODwildconst;
alias MODmutable = MODFlags.MODmutable;

alias MOD = ubyte;

/***********************************************************
 */
extern (C++) abstract class Type : RootObject
{
    TY ty;
    MOD mod; // modifiers MODxxxx
    char* deco;

    /* These are cached values that are lazily evaluated by constOf(), immutableOf(), etc.
     * They should not be referenced by anybody but mtype.c.
     * They can be NULL if not lazily evaluated yet.
     * Note that there is no "shared immutable", because that is just immutable
     * Naked == no MOD bits
     */
    Type cto;       // MODconst                 ? naked version of this type : const version
    Type ito;       // MODimmutable             ? naked version of this type : immutable version
    Type sto;       // MODshared                ? naked version of this type : shared mutable version
    Type scto;      // MODshared | MODconst     ? naked version of this type : shared const version
    Type wto;       // MODwild                  ? naked version of this type : wild version
    Type wcto;      // MODwildconst             ? naked version of this type : wild const version
    Type swto;      // MODshared | MODwild      ? naked version of this type : shared wild version
    Type swcto;     // MODshared | MODwildconst ? naked version of this type : shared wild const version

    Type pto;       // merged pointer to this type
    Type rto;       // reference to this type
    Type arrayof;   // array of this type

    TypeInfoDeclaration vtinfo;     // TypeInfo object for this Type

    type* ctype;                    // for back end

    extern (C++) static __gshared Type tvoid;
    extern (C++) static __gshared Type tint8;
    extern (C++) static __gshared Type tuns8;
    extern (C++) static __gshared Type tint16;
    extern (C++) static __gshared Type tuns16;
    extern (C++) static __gshared Type tint32;
    extern (C++) static __gshared Type tuns32;
    extern (C++) static __gshared Type tint64;
    extern (C++) static __gshared Type tuns64;
    extern (C++) static __gshared Type tint128;
    extern (C++) static __gshared Type tuns128;
    extern (C++) static __gshared Type tfloat32;
    extern (C++) static __gshared Type tfloat64;
    extern (C++) static __gshared Type tfloat80;
    extern (C++) static __gshared Type timaginary32;
    extern (C++) static __gshared Type timaginary64;
    extern (C++) static __gshared Type timaginary80;
    extern (C++) static __gshared Type tcomplex32;
    extern (C++) static __gshared Type tcomplex64;
    extern (C++) static __gshared Type tcomplex80;
    extern (C++) static __gshared Type tbool;
    extern (C++) static __gshared Type tchar;
    extern (C++) static __gshared Type twchar;
    extern (C++) static __gshared Type tdchar;

    // Some special types
    extern (C++) static __gshared Type tshiftcnt;
    extern (C++) static __gshared Type tvoidptr;    // void*
    extern (C++) static __gshared Type tstring;     // immutable(char)[]
    extern (C++) static __gshared Type twstring;    // immutable(wchar)[]
    extern (C++) static __gshared Type tdstring;    // immutable(dchar)[]
    extern (C++) static __gshared Type tvalist;     // va_list alias
    extern (C++) static __gshared Type terror;      // for error recovery
    extern (C++) static __gshared Type tnull;       // for null type

    extern (C++) static __gshared Type tsize_t;     // matches size_t alias
    extern (C++) static __gshared Type tptrdiff_t;  // matches ptrdiff_t alias
    extern (C++) static __gshared Type thash_t;     // matches hash_t alias

    extern (C++) static __gshared ClassDeclaration dtypeinfo;
    extern (C++) static __gshared ClassDeclaration typeinfoclass;
    extern (C++) static __gshared ClassDeclaration typeinfointerface;
    extern (C++) static __gshared ClassDeclaration typeinfostruct;
    extern (C++) static __gshared ClassDeclaration typeinfopointer;
    extern (C++) static __gshared ClassDeclaration typeinfoarray;
    extern (C++) static __gshared ClassDeclaration typeinfostaticarray;
    extern (C++) static __gshared ClassDeclaration typeinfoassociativearray;
    extern (C++) static __gshared ClassDeclaration typeinfovector;
    extern (C++) static __gshared ClassDeclaration typeinfoenum;
    extern (C++) static __gshared ClassDeclaration typeinfofunction;
    extern (C++) static __gshared ClassDeclaration typeinfodelegate;
    extern (C++) static __gshared ClassDeclaration typeinfotypelist;
    extern (C++) static __gshared ClassDeclaration typeinfoconst;
    extern (C++) static __gshared ClassDeclaration typeinfoinvariant;
    extern (C++) static __gshared ClassDeclaration typeinfoshared;
    extern (C++) static __gshared ClassDeclaration typeinfowild;

    extern (C++) static __gshared TemplateDeclaration rtinfo;

    extern (C++) static __gshared Type[TMAX] basic;
    extern (C++) static __gshared StringTable stringtable;

    extern (C++) static __gshared ubyte[TMAX] sizeTy = ()
        {
            ubyte[TMAX] sizeTy = __traits(classInstanceSize, TypeBasic);
            sizeTy[Tsarray] = __traits(classInstanceSize, TypeSArray);
            sizeTy[Tarray] = __traits(classInstanceSize, TypeDArray);
            sizeTy[Taarray] = __traits(classInstanceSize, TypeAArray);
            sizeTy[Tpointer] = __traits(classInstanceSize, TypePointer);
            sizeTy[Treference] = __traits(classInstanceSize, TypeReference);
            sizeTy[Tfunction] = __traits(classInstanceSize, TypeFunction);
            sizeTy[Tdelegate] = __traits(classInstanceSize, TypeDelegate);
            sizeTy[Tident] = __traits(classInstanceSize, TypeIdentifier);
            sizeTy[Tinstance] = __traits(classInstanceSize, TypeInstance);
            sizeTy[Ttypeof] = __traits(classInstanceSize, TypeTypeof);
            sizeTy[Tenum] = __traits(classInstanceSize, TypeEnum);
            sizeTy[Tstruct] = __traits(classInstanceSize, TypeStruct);
            sizeTy[Tclass] = __traits(classInstanceSize, TypeClass);
            sizeTy[Ttuple] = __traits(classInstanceSize, TypeTuple);
            sizeTy[Tslice] = __traits(classInstanceSize, TypeSlice);
            sizeTy[Treturn] = __traits(classInstanceSize, TypeReturn);
            sizeTy[Terror] = __traits(classInstanceSize, TypeError);
            sizeTy[Tnull] = __traits(classInstanceSize, TypeNull);
            sizeTy[Tvector] = __traits(classInstanceSize, TypeVector);
            return sizeTy;
        }();

    final extern (D) this(TY ty)
    {
        this.ty = ty;
    }

    const(char)* kind() const
    {
        assert(false); // should be overridden
    }

    final Type copy()
    {
        Type t = cast(Type)mem.xmalloc(sizeTy[ty]);
        memcpy(cast(void*)t, cast(void*)this, sizeTy[ty]);
        return t;
    }

    Type syntaxCopy()
    {
        print();
        fprintf(stderr, "ty = %d\n", ty);
        assert(0);
    }

    override bool equals(RootObject o)
    {
        Type t = cast(Type)o;
        //printf("Type::equals(%s, %s)\n", toChars(), t.toChars());
        // deco strings are unique
        // and semantic() has been run
        if (this == o || ((t && deco == t.deco) && deco !is null))
        {
            //printf("deco = '%s', t.deco = '%s'\n", deco, t.deco);
            return true;
        }
        //if (deco && t && t.deco) printf("deco = '%s', t.deco = '%s'\n", deco, t.deco);
        return false;
    }

    final bool equivalent(Type t)
    {
        return immutableOf().equals(t.immutableOf());
    }

    // kludge for template.isType()
    override final DYNCAST dyncast() const
    {
        return DYNCAST.type;
    }

    /*******************************
     * Covariant means that 'this' can substitute for 't',
     * i.e. a pure function is a match for an impure type.
     * Params:
     *      t = type 'this' is covariant with
     *      pstc = if not null, store STCxxxx which would make it covariant
     *      fix17349 = enable fix https://issues.dlang.org/show_bug.cgi?id=17349
     * Returns:
     *      0       types are distinct
     *      1       this is covariant with t
     *      2       arguments match as far as overloading goes,
     *              but types are not covariant
     *      3       cannot determine covariance because of forward references
     *      *pstc   STCxxxx which would make it covariant
     */
    final int covariant(Type t, StorageClass* pstc = null, bool fix17349 = true)
    {
        version (none)
        {
            printf("Type::covariant(t = %s) %s\n", t.toChars(), toChars());
            printf("deco = %p, %p\n", deco, t.deco);
            //    printf("ty = %d\n", next.ty);
            printf("mod = %x, %x\n", mod, t.mod);
        }
        if (pstc)
            *pstc = 0;
        StorageClass stc = 0;

        bool notcovariant = false;

        TypeFunction t1;
        TypeFunction t2;

        if (equals(t))
            return 1; // covariant

        if (ty != Tfunction || t.ty != Tfunction)
            goto Ldistinct;

        t1 = cast(TypeFunction)this;
        t2 = cast(TypeFunction)t;

        if (t1.varargs != t2.varargs)
            goto Ldistinct;

        if (t1.parameters && t2.parameters)
        {
            size_t dim = Parameter.dim(t1.parameters);
            if (dim != Parameter.dim(t2.parameters))
                goto Ldistinct;

            for (size_t i = 0; i < dim; i++)
            {
                Parameter fparam1 = Parameter.getNth(t1.parameters, i);
                Parameter fparam2 = Parameter.getNth(t2.parameters, i);

                if (!fparam1.type.equals(fparam2.type))
                {
                    if (!fix17349)
                        goto Ldistinct;
                    Type tp1 = fparam1.type;
                    Type tp2 = fparam2.type;
                    if (tp1.ty == tp2.ty)
                    {
                        if (tp1.ty == Tclass)
                        {
                            if ((cast(TypeClass)tp1).sym == (cast(TypeClass)tp2).sym && MODimplicitConv(tp2.mod, tp1.mod))
                                goto Lcov;
                        }
                        else if (tp1.ty == Tstruct)
                        {
                            if ((cast(TypeStruct)tp1).sym == (cast(TypeStruct)tp2).sym && MODimplicitConv(tp2.mod, tp1.mod))
                                goto Lcov;
                        }
                        else if (tp1.ty == Tpointer)
                        {
                            if (tp2.implicitConvTo(tp1))
                                goto Lcov;
                        }
                        else if (tp1.ty == Tarray)
                        {
                            if (tp2.implicitConvTo(tp1))
                                goto Lcov;
                        }
                        else if (tp1.ty == Tdelegate)
                        {
                            if (tp1.implicitConvTo(tp2))
                                goto Lcov;
                        }
                    }
                    goto Ldistinct;
                }
            Lcov:
                notcovariant |= !fparam1.isCovariant(t1.isref, fparam2);
            }
        }
        else if (t1.parameters != t2.parameters)
        {
            size_t dim1 = !t1.parameters ? 0 : t1.parameters.dim;
            size_t dim2 = !t2.parameters ? 0 : t2.parameters.dim;
            if (dim1 || dim2)
                goto Ldistinct;
        }

        // The argument lists match
        if (notcovariant)
            goto Lnotcovariant;
        if (t1.linkage != t2.linkage)
            goto Lnotcovariant;

        {
            // Return types
            Type t1n = t1.next;
            Type t2n = t2.next;

            if (!t1n || !t2n) // happens with return type inference
                goto Lnotcovariant;

            if (t1n.equals(t2n))
                goto Lcovariant;
            if (t1n.ty == Tclass && t2n.ty == Tclass)
            {
                /* If same class type, but t2n is const, then it's
                 * covariant. Do this test first because it can work on
                 * forward references.
                 */
                if ((cast(TypeClass)t1n).sym == (cast(TypeClass)t2n).sym && MODimplicitConv(t1n.mod, t2n.mod))
                    goto Lcovariant;

                // If t1n is forward referenced:
                ClassDeclaration cd = (cast(TypeClass)t1n).sym;
                if (cd.semanticRun < PASSsemanticdone)
                    cd.semantic(null);
                if (!cd.isBaseInfoComplete())
                {
                    return 3; // forward references
                }
            }
            if (t1n.ty == Tstruct && t2n.ty == Tstruct)
            {
                if ((cast(TypeStruct)t1n).sym == (cast(TypeStruct)t2n).sym && MODimplicitConv(t1n.mod, t2n.mod))
                    goto Lcovariant;
            }
            else if (t1n.ty == t2n.ty && t1n.implicitConvTo(t2n))
                goto Lcovariant;
            else if (t1n.ty == Tnull && t1n.implicitConvTo(t2n) && t1n.size() == t2n.size())
                goto Lcovariant;
        }
        goto Lnotcovariant;

    Lcovariant:
        if (t1.isref != t2.isref)
            goto Lnotcovariant;

        if (!t1.isref && (t1.isscope || t2.isscope))
        {
            StorageClass stc1 = t1.isscope ? STCscope : 0;
            StorageClass stc2 = t2.isscope ? STCscope : 0;
            if (t1.isreturn)
            {
                stc1 |= STCreturn;
                if (!t1.isscope)
                    stc1 |= STCref;
            }
            if (t2.isreturn)
            {
                stc2 |= STCreturn;
                if (!t2.isscope)
                    stc2 |= STCref;
            }
            if (!Parameter.isCovariantScope(t1.isref, stc1, stc2))
                goto Lnotcovariant;
        }

        // We can subtract 'return ref' from 'this', but cannot add it
        else if (t1.isreturn && !t2.isreturn)
            goto Lnotcovariant;

        /* Can convert mutable to const
         */
        if (!MODimplicitConv(t2.mod, t1.mod))
        {
            version (none)
            {
                //stop attribute inference with const
                // If adding 'const' will make it covariant
                if (MODimplicitConv(t2.mod, MODmerge(t1.mod, MODconst)))
                    stc |= STCconst;
                else
                    goto Lnotcovariant;
            }
            else
            {
                goto Ldistinct;
            }
        }

        /* Can convert pure to impure, nothrow to throw, and nogc to gc
         */
        if (!t1.purity && t2.purity)
            stc |= STCpure;

        if (!t1.isnothrow && t2.isnothrow)
            stc |= STCnothrow;

        if (!t1.isnogc && t2.isnogc)
            stc |= STCnogc;

        /* Can convert safe/trusted to system
         */
        if (t1.trust <= TRUSTsystem && t2.trust >= TRUSTtrusted)
        {
            // Should we infer trusted or safe? Go with safe.
            stc |= STCsafe;
        }

        if (stc)
        {
            if (pstc)
                *pstc = stc;
            goto Lnotcovariant;
        }

        //printf("\tcovaraint: 1\n");
        return 1;

    Ldistinct:
        //printf("\tcovaraint: 0\n");
        return 0;

    Lnotcovariant:
        //printf("\tcovaraint: 2\n");
        return 2;
    }

    /********************************
     * For pretty-printing a type.
     */
    final override const(char)* toChars()
    {
        OutBuffer buf;
        buf.reserve(16);
        HdrGenState hgs;
        hgs.fullQual = (ty == Tclass && !mod);

        .toCBuffer(this, &buf, null, &hgs);
        return buf.extractString();
    }

    final char* toPrettyChars(bool QualifyTypes = false)
    {
        OutBuffer buf;
        buf.reserve(16);
        HdrGenState hgs;
        hgs.fullQual = QualifyTypes;

        .toCBuffer(this, &buf, null, &hgs);
        return buf.extractString();
    }

    static void _init()
    {
        stringtable._init(14000);

        // Set basic types
        static __gshared TY* basetab =
        [
            Tvoid,
            Tint8,
            Tuns8,
            Tint16,
            Tuns16,
            Tint32,
            Tuns32,
            Tint64,
            Tuns64,
            Tint128,
            Tuns128,
            Tfloat32,
            Tfloat64,
            Tfloat80,
            Timaginary32,
            Timaginary64,
            Timaginary80,
            Tcomplex32,
            Tcomplex64,
            Tcomplex80,
            Tbool,
            Tchar,
            Twchar,
            Tdchar,
            Terror
        ];

        for (size_t i = 0; basetab[i] != Terror; i++)
        {
            Type t = new TypeBasic(basetab[i]);
            t = t.merge();
            basic[basetab[i]] = t;
        }
        basic[Terror] = new TypeError();

        tvoid = basic[Tvoid];
        tint8 = basic[Tint8];
        tuns8 = basic[Tuns8];
        tint16 = basic[Tint16];
        tuns16 = basic[Tuns16];
        tint32 = basic[Tint32];
        tuns32 = basic[Tuns32];
        tint64 = basic[Tint64];
        tuns64 = basic[Tuns64];
        tint128 = basic[Tint128];
        tuns128 = basic[Tuns128];
        tfloat32 = basic[Tfloat32];
        tfloat64 = basic[Tfloat64];
        tfloat80 = basic[Tfloat80];

        timaginary32 = basic[Timaginary32];
        timaginary64 = basic[Timaginary64];
        timaginary80 = basic[Timaginary80];

        tcomplex32 = basic[Tcomplex32];
        tcomplex64 = basic[Tcomplex64];
        tcomplex80 = basic[Tcomplex80];

        tbool = basic[Tbool];
        tchar = basic[Tchar];
        twchar = basic[Twchar];
        tdchar = basic[Tdchar];

        tshiftcnt = tint32;
        terror = basic[Terror];
        tnull = basic[Tnull];
        tnull = new TypeNull();
        tnull.deco = tnull.merge().deco;

        tvoidptr = tvoid.pointerTo();
        tstring = tchar.immutableOf().arrayOf();
        twstring = twchar.immutableOf().arrayOf();
        tdstring = tdchar.immutableOf().arrayOf();
        tvalist = Target.va_listType();

        if (global.params.isLP64)
        {
            Tsize_t = Tuns64;
            Tptrdiff_t = Tint64;
        }
        else
        {
            Tsize_t = Tuns32;
            Tptrdiff_t = Tint32;
        }

        tsize_t = basic[Tsize_t];
        tptrdiff_t = basic[Tptrdiff_t];
        thash_t = tsize_t;
    }

    final d_uns64 size()
    {
        return size(Loc());
    }

    d_uns64 size(Loc loc)
    {
        error(loc, "no size for type %s", toChars());
        return SIZE_INVALID;
    }

    uint alignsize()
    {
        return cast(uint)size(Loc());
    }

    Type semantic(Loc loc, Scope* sc)
    {
        if (ty == Tint128 || ty == Tuns128)
        {
            error(loc, "cent and ucent types not implemented");
            return terror;
        }

        return merge();
    }

    final Type trySemantic(Loc loc, Scope* sc)
    {
        //printf("+trySemantic(%s) %d\n", toChars(), global.errors);
        uint errors = global.startGagging();
        Type t = semantic(loc, sc);
        if (global.endGagging(errors) || t.ty == Terror) // if any errors happened
        {
            t = null;
        }
        //printf("-trySemantic(%s) %d\n", toChars(), global.errors);
        return t;
    }

    /************************************
     */
    final Type merge()
    {
        if (ty == Terror)
            return this;
        if (ty == Ttypeof)
            return this;
        if (ty == Tident)
            return this;
        if (ty == Tinstance)
            return this;
        if (ty == Taarray && !(cast(TypeAArray)this).index.merge().deco)
            return this;
        if (ty != Tenum && nextOf() && !nextOf().deco)
            return this;

        //printf("merge(%s)\n", toChars());
        Type t = this;
        assert(t);
        if (!deco)
        {
            OutBuffer buf;
            buf.reserve(32);

            mangleToBuffer(this, &buf);

            StringValue* sv = stringtable.update(cast(char*)buf.data, buf.offset);
            if (sv.ptrvalue)
            {
                t = cast(Type)sv.ptrvalue;
                debug
                {
                    if (!t.deco)
                        printf("t = %s\n", t.toChars());
                }
                assert(t.deco);
                //printf("old value, deco = '%s' %p\n", t.deco, t.deco);
            }
            else
            {
                sv.ptrvalue = cast(char*)(t = stripDefaultArgs(t));
                deco = t.deco = cast(char*)sv.toDchars();
                //printf("new value, deco = '%s' %p\n", t.deco, t.deco);
            }
        }
        return t;
    }

    /*************************************
     * This version does a merge even if the deco is already computed.
     * Necessary for types that have a deco, but are not merged.
     */
    final Type merge2()
    {
        //printf("merge2(%s)\n", toChars());
        Type t = this;
        assert(t);
        if (!t.deco)
            return t.merge();

        StringValue* sv = stringtable.lookup(t.deco, strlen(t.deco));
        if (sv && sv.ptrvalue)
        {
            t = cast(Type)sv.ptrvalue;
            assert(t.deco);
        }
        else
            assert(0);
        return t;
    }

    /*********************************
     * Store this type's modifier name into buf.
     */
    final void modToBuffer(OutBuffer* buf)
    {
        if (mod)
        {
            buf.writeByte(' ');
            MODtoBuffer(buf, mod);
        }
    }

    /*********************************
     * Return this type's modifier name.
     */
    final char* modToChars()
    {
        OutBuffer buf;
        buf.reserve(16);
        modToBuffer(&buf);
        return buf.extractString();
    }

    /** For each active modifier (MODconst, MODimmutable, etc) call fp with a
     void* for the work param and a string representation of the attribute. */
    final int modifiersApply(void* param, int function(void*, const(char)*) fp)
    {
        immutable ubyte[4] modsArr = [MODconst, MODimmutable, MODwild, MODshared];

        foreach (modsarr; modsArr)
        {
            if (mod & modsarr)
            {
                if (int res = fp(param, MODtoChars(modsarr)))
                    return res;
            }
        }

        return 0;
    }

    bool isintegral()
    {
        return false;
    }

    // real, imaginary, or complex
    bool isfloating()
    {
        return false;
    }

    bool isreal()
    {
        return false;
    }

    bool isimaginary()
    {
        return false;
    }

    bool iscomplex()
    {
        return false;
    }

    bool isscalar()
    {
        return false;
    }

    bool isunsigned()
    {
        return false;
    }

    bool isscope()
    {
        return false;
    }

    bool isString()
    {
        return false;
    }

    /**************************
     * When T is mutable,
     * Given:
     *      T a, b;
     * Can we bitwise assign:
     *      a = b;
     * ?
     */
    bool isAssignable()
    {
        return true;
    }

    /**************************
     * Returns true if T can be converted to boolean value.
     */
    bool isBoolean()
    {
        return isscalar();
    }

    /*********************************
     * Check type to see if it is based on a deprecated symbol.
     */
    void checkDeprecated(Loc loc, Scope* sc)
    {
        Dsymbol s = toDsymbol(sc);
        if (s)
            s.checkDeprecated(loc, sc);
    }

    final bool isConst() const
    {
        return (mod & MODconst) != 0;
    }

    final bool isImmutable() const
    {
        return (mod & MODimmutable) != 0;
    }

    final bool isMutable() const
    {
        return (mod & (MODconst | MODimmutable | MODwild)) == 0;
    }

    final bool isShared() const
    {
        return (mod & MODshared) != 0;
    }

    final bool isSharedConst() const
    {
        return (mod & (MODshared | MODconst)) == (MODshared | MODconst);
    }

    final bool isWild() const
    {
        return (mod & MODwild) != 0;
    }

    final bool isWildConst() const
    {
        return (mod & MODwildconst) == MODwildconst;
    }

    final bool isSharedWild() const
    {
        return (mod & (MODshared | MODwild)) == (MODshared | MODwild);
    }

    final bool isNaked() const
    {
        return mod == 0;
    }

    /********************************
     * Return a copy of this type with all attributes null-initialized.
     * Useful for creating a type with different modifiers.
     */
    final Type nullAttributes()
    {
        uint sz = sizeTy[ty];
        Type t = cast(Type)mem.xmalloc(sz);
        memcpy(cast(void*)t, cast(void*)this, sz);
        // t.mod = NULL;  // leave mod unchanged
        t.deco = null;
        t.arrayof = null;
        t.pto = null;
        t.rto = null;
        t.cto = null;
        t.ito = null;
        t.sto = null;
        t.scto = null;
        t.wto = null;
        t.wcto = null;
        t.swto = null;
        t.swcto = null;
        t.vtinfo = null;
        t.ctype = null;
        if (t.ty == Tstruct)
            (cast(TypeStruct)t).att = RECfwdref;
        if (t.ty == Tclass)
            (cast(TypeClass)t).att = RECfwdref;
        return t;
    }

    /********************************
     * Convert to 'const'.
     */
    final Type constOf()
    {
        //printf("Type::constOf() %p %s\n", this, toChars());
        if (mod == MODconst)
            return this;
        if (cto)
        {
            assert(cto.mod == MODconst);
            return cto;
        }
        Type t = makeConst();
        t = t.merge();
        t.fixTo(this);
        //printf("-Type::constOf() %p %s\n", t, t.toChars());
        return t;
    }

    /********************************
     * Convert to 'immutable'.
     */
    final Type immutableOf()
    {
        //printf("Type::immutableOf() %p %s\n", this, toChars());
        if (isImmutable())
            return this;
        if (ito)
        {
            assert(ito.isImmutable());
            return ito;
        }
        Type t = makeImmutable();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p\n", t);
        return t;
    }

    /********************************
     * Make type mutable.
     */
    final Type mutableOf()
    {
        //printf("Type::mutableOf() %p, %s\n", this, toChars());
        Type t = this;
        if (isImmutable())
        {
            t = ito; // immutable => naked
            assert(!t || (t.isMutable() && !t.isShared()));
        }
        else if (isConst())
        {
            if (isShared())
            {
                if (isWild())
                    t = swcto; // shared wild const -> shared
                else
                    t = sto; // shared const => shared
            }
            else
            {
                if (isWild())
                    t = wcto; // wild const -> naked
                else
                    t = cto; // const => naked
            }
            assert(!t || t.isMutable());
        }
        else if (isWild())
        {
            if (isShared())
                t = sto; // shared wild => shared
            else
                t = wto; // wild => naked
            assert(!t || t.isMutable());
        }
        if (!t)
        {
            t = makeMutable();
            t = t.merge();
            t.fixTo(this);
        }
        else
            t = t.merge();
        assert(t.isMutable());
        return t;
    }

    final Type sharedOf()
    {
        //printf("Type::sharedOf() %p, %s\n", this, toChars());
        if (mod == MODshared)
            return this;
        if (sto)
        {
            assert(sto.mod == MODshared);
            return sto;
        }
        Type t = makeShared();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p\n", t);
        return t;
    }

    final Type sharedConstOf()
    {
        //printf("Type::sharedConstOf() %p, %s\n", this, toChars());
        if (mod == (MODshared | MODconst))
            return this;
        if (scto)
        {
            assert(scto.mod == (MODshared | MODconst));
            return scto;
        }
        Type t = makeSharedConst();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p\n", t);
        return t;
    }

    /********************************
     * Make type unshared.
     *      0            => 0
     *      const        => const
     *      immutable    => immutable
     *      shared       => 0
     *      shared const => const
     *      wild         => wild
     *      wild const   => wild const
     *      shared wild  => wild
     *      shared wild const => wild const
     */
    final Type unSharedOf()
    {
        //printf("Type::unSharedOf() %p, %s\n", this, toChars());
        Type t = this;

        if (isShared())
        {
            if (isWild())
            {
                if (isConst())
                    t = wcto; // shared wild const => wild const
                else
                    t = wto; // shared wild => wild
            }
            else
            {
                if (isConst())
                    t = cto; // shared const => const
                else
                    t = sto; // shared => naked
            }
            assert(!t || !t.isShared());
        }

        if (!t)
        {
            t = this.nullAttributes();
            t.mod = mod & ~MODshared;
            t.ctype = ctype;
            t = t.merge();
            t.fixTo(this);
        }
        else
            t = t.merge();
        assert(!t.isShared());
        return t;
    }

    /********************************
     * Convert to 'wild'.
     */
    final Type wildOf()
    {
        //printf("Type::wildOf() %p %s\n", this, toChars());
        if (mod == MODwild)
            return this;
        if (wto)
        {
            assert(wto.mod == MODwild);
            return wto;
        }
        Type t = makeWild();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p %s\n", t, t.toChars());
        return t;
    }

    final Type wildConstOf()
    {
        //printf("Type::wildConstOf() %p %s\n", this, toChars());
        if (mod == MODwildconst)
            return this;
        if (wcto)
        {
            assert(wcto.mod == MODwildconst);
            return wcto;
        }
        Type t = makeWildConst();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p %s\n", t, t.toChars());
        return t;
    }

    final Type sharedWildOf()
    {
        //printf("Type::sharedWildOf() %p, %s\n", this, toChars());
        if (mod == (MODshared | MODwild))
            return this;
        if (swto)
        {
            assert(swto.mod == (MODshared | MODwild));
            return swto;
        }
        Type t = makeSharedWild();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p %s\n", t, t.toChars());
        return t;
    }

    final Type sharedWildConstOf()
    {
        //printf("Type::sharedWildConstOf() %p, %s\n", this, toChars());
        if (mod == (MODshared | MODwildconst))
            return this;
        if (swcto)
        {
            assert(swcto.mod == (MODshared | MODwildconst));
            return swcto;
        }
        Type t = makeSharedWildConst();
        t = t.merge();
        t.fixTo(this);
        //printf("\t%p %s\n", t, t.toChars());
        return t;
    }

    /**********************************
     * For our new type 'this', which is type-constructed from t,
     * fill in the cto, ito, sto, scto, wto shortcuts.
     */
    final void fixTo(Type t)
    {
        // If fixing this: immutable(T*) by t: immutable(T)*,
        // cache t to this.xto won't break transitivity.
        Type mto = null;
        Type tn = nextOf();
        if (!tn || ty != Tsarray && tn.mod == t.nextOf().mod)
        {
            switch (t.mod)
            {
            case 0:
                mto = t;
                break;

            case MODconst:
                cto = t;
                break;

            case MODwild:
                wto = t;
                break;

            case MODwildconst:
                wcto = t;
                break;

            case MODshared:
                sto = t;
                break;

            case MODshared | MODconst:
                scto = t;
                break;

            case MODshared | MODwild:
                swto = t;
                break;

            case MODshared | MODwildconst:
                swcto = t;
                break;

            case MODimmutable:
                ito = t;
                break;

            default:
                break;
            }
        }
        assert(mod != t.mod);

        auto X(T, U)(T m, U n)
        {
            return ((m << 4) | n);
        }

        switch (mod)
        {
        case 0:
            break;

        case MODconst:
            cto = mto;
            t.cto = this;
            break;

        case MODwild:
            wto = mto;
            t.wto = this;
            break;

        case MODwildconst:
            wcto = mto;
            t.wcto = this;
            break;

        case MODshared:
            sto = mto;
            t.sto = this;
            break;

        case MODshared | MODconst:
            scto = mto;
            t.scto = this;
            break;

        case MODshared | MODwild:
            swto = mto;
            t.swto = this;
            break;

        case MODshared | MODwildconst:
            swcto = mto;
            t.swcto = this;
            break;

        case MODimmutable:
            t.ito = this;
            if (t.cto)
                t.cto.ito = this;
            if (t.sto)
                t.sto.ito = this;
            if (t.scto)
                t.scto.ito = this;
            if (t.wto)
                t.wto.ito = this;
            if (t.wcto)
                t.wcto.ito = this;
            if (t.swto)
                t.swto.ito = this;
            if (t.swcto)
                t.swcto.ito = this;
            break;

        default:
            assert(0);
        }

        check();
        t.check();
        //printf("fixTo: %s, %s\n", toChars(), t.toChars());
    }

    /***************************
     * Look for bugs in constructing types.
     */
    final void check()
    {
        switch (mod)
        {
        case 0:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODconst:
            if (cto)
                assert(cto.mod == 0);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODwild:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == 0);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODwildconst:
            assert(!cto || cto.mod == MODconst);
            assert(!ito || ito.mod == MODimmutable);
            assert(!sto || sto.mod == MODshared);
            assert(!scto || scto.mod == (MODshared | MODconst));
            assert(!wto || wto.mod == MODwild);
            assert(!wcto || wcto.mod == 0);
            assert(!swto || swto.mod == (MODshared | MODwild));
            assert(!swcto || swcto.mod == (MODshared | MODwildconst));
            break;

        case MODshared:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == 0);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODshared | MODconst:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == 0);
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODshared | MODwild:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == MODimmutable);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == 0);
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        case MODshared | MODwildconst:
            assert(!cto || cto.mod == MODconst);
            assert(!ito || ito.mod == MODimmutable);
            assert(!sto || sto.mod == MODshared);
            assert(!scto || scto.mod == (MODshared | MODconst));
            assert(!wto || wto.mod == MODwild);
            assert(!wcto || wcto.mod == MODwildconst);
            assert(!swto || swto.mod == (MODshared | MODwild));
            assert(!swcto || swcto.mod == 0);
            break;

        case MODimmutable:
            if (cto)
                assert(cto.mod == MODconst);
            if (ito)
                assert(ito.mod == 0);
            if (sto)
                assert(sto.mod == MODshared);
            if (scto)
                assert(scto.mod == (MODshared | MODconst));
            if (wto)
                assert(wto.mod == MODwild);
            if (wcto)
                assert(wcto.mod == MODwildconst);
            if (swto)
                assert(swto.mod == (MODshared | MODwild));
            if (swcto)
                assert(swcto.mod == (MODshared | MODwildconst));
            break;

        default:
            assert(0);
        }

        Type tn = nextOf();
        if (tn && ty != Tfunction && tn.ty != Tfunction && ty != Tenum)
        {
            // Verify transitivity
            switch (mod)
            {
            case 0:
            case MODconst:
            case MODwild:
            case MODwildconst:
            case MODshared:
            case MODshared | MODconst:
            case MODshared | MODwild:
            case MODshared | MODwildconst:
            case MODimmutable:
                assert(tn.mod == MODimmutable || (tn.mod & mod) == mod);
                break;

            default:
                assert(0);
            }
            tn.check();
        }
    }

    /*************************************
     * Apply STCxxxx bits to existing type.
     * Use *before* semantic analysis is run.
     */
    final Type addSTC(StorageClass stc)
    {
        Type t = this;
        if (t.isImmutable())
        {
        }
        else if (stc & STCimmutable)
        {
            t = t.makeImmutable();
        }
        else
        {
            if ((stc & STCshared) && !t.isShared())
            {
                if (t.isWild())
                {
                    if (t.isConst())
                        t = t.makeSharedWildConst();
                    else
                        t = t.makeSharedWild();
                }
                else
                {
                    if (t.isConst())
                        t = t.makeSharedConst();
                    else
                        t = t.makeShared();
                }
            }
            if ((stc & STCconst) && !t.isConst())
            {
                if (t.isShared())
                {
                    if (t.isWild())
                        t = t.makeSharedWildConst();
                    else
                        t = t.makeSharedConst();
                }
                else
                {
                    if (t.isWild())
                        t = t.makeWildConst();
                    else
                        t = t.makeConst();
                }
            }
            if ((stc & STCwild) && !t.isWild())
            {
                if (t.isShared())
                {
                    if (t.isConst())
                        t = t.makeSharedWildConst();
                    else
                        t = t.makeSharedWild();
                }
                else
                {
                    if (t.isConst())
                        t = t.makeWildConst();
                    else
                        t = t.makeWild();
                }
            }
        }
        return t;
    }

    /************************************
     * Apply MODxxxx bits to existing type.
     */
    final Type castMod(MOD mod)
    {
        Type t;
        switch (mod)
        {
        case 0:
            t = unSharedOf().mutableOf();
            break;

        case MODconst:
            t = unSharedOf().constOf();
            break;

        case MODwild:
            t = unSharedOf().wildOf();
            break;

        case MODwildconst:
            t = unSharedOf().wildConstOf();
            break;

        case MODshared:
            t = mutableOf().sharedOf();
            break;

        case MODshared | MODconst:
            t = sharedConstOf();
            break;

        case MODshared | MODwild:
            t = sharedWildOf();
            break;

        case MODshared | MODwildconst:
            t = sharedWildConstOf();
            break;

        case MODimmutable:
            t = immutableOf();
            break;

        default:
            assert(0);
        }
        return t;
    }

    /************************************
     * Add MODxxxx bits to existing type.
     * We're adding, not replacing, so adding const to
     * a shared type => "shared const"
     */
    final Type addMod(MOD mod)
    {
        /* Add anything to immutable, and it remains immutable
         */
        Type t = this;
        if (!t.isImmutable())
        {
            //printf("addMod(%x) %s\n", mod, toChars());
            switch (mod)
            {
            case 0:
                break;

            case MODconst:
                if (isShared())
                {
                    if (isWild())
                        t = sharedWildConstOf();
                    else
                        t = sharedConstOf();
                }
                else
                {
                    if (isWild())
                        t = wildConstOf();
                    else
                        t = constOf();
                }
                break;

            case MODwild:
                if (isShared())
                {
                    if (isConst())
                        t = sharedWildConstOf();
                    else
                        t = sharedWildOf();
                }
                else
                {
                    if (isConst())
                        t = wildConstOf();
                    else
                        t = wildOf();
                }
                break;

            case MODwildconst:
                if (isShared())
                    t = sharedWildConstOf();
                else
                    t = wildConstOf();
                break;

            case MODshared:
                if (isWild())
                {
                    if (isConst())
                        t = sharedWildConstOf();
                    else
                        t = sharedWildOf();
                }
                else
                {
                    if (isConst())
                        t = sharedConstOf();
                    else
                        t = sharedOf();
                }
                break;

            case MODshared | MODconst:
                if (isWild())
                    t = sharedWildConstOf();
                else
                    t = sharedConstOf();
                break;

            case MODshared | MODwild:
                if (isConst())
                    t = sharedWildConstOf();
                else
                    t = sharedWildOf();
                break;

            case MODshared | MODwildconst:
                t = sharedWildConstOf();
                break;

            case MODimmutable:
                t = immutableOf();
                break;

            default:
                assert(0);
            }
        }
        return t;
    }

    /************************************
     * Add storage class modifiers to type.
     */
    Type addStorageClass(StorageClass stc)
    {
        /* Just translate to MOD bits and let addMod() do the work
         */
        MOD mod = 0;
        if (stc & STCimmutable)
            mod = MODimmutable;
        else
        {
            if (stc & (STCconst | STCin))
                mod |= MODconst;
            if (stc & STCwild)
                mod |= MODwild;
            if (stc & STCshared)
                mod |= MODshared;
        }
        return addMod(mod);
    }

    final Type pointerTo()
    {
        if (ty == Terror)
            return this;
        if (!pto)
        {
            Type t = new TypePointer(this);
            if (ty == Tfunction)
            {
                t.deco = t.merge().deco;
                pto = t;
            }
            else
                pto = t.merge();
        }
        return pto;
    }

    final Type referenceTo()
    {
        if (ty == Terror)
            return this;
        if (!rto)
        {
            Type t = new TypeReference(this);
            rto = t.merge();
        }
        return rto;
    }

    final Type arrayOf()
    {
        if (ty == Terror)
            return this;
        if (!arrayof)
        {
            Type t = new TypeDArray(this);
            arrayof = t.merge();
        }
        return arrayof;
    }

    // Make corresponding static array type without semantic
    final Type sarrayOf(dinteger_t dim)
    {
        assert(deco);
        Type t = new TypeSArray(this, new IntegerExp(Loc(), dim, Type.tsize_t));
        // according to TypeSArray::semantic()
        t = t.addMod(mod);
        t = t.merge();
        return t;
    }

    final Type aliasthisOf()
    {
        auto ad = isAggregate(this);
        if (!ad || !ad.aliasthis)
            return null;

        auto s = ad.aliasthis;
        if (s.isAliasDeclaration())
            s = s.toAlias();

        if (s.isTupleDeclaration())
            return null;

        if (auto vd = s.isVarDeclaration())
        {
            auto t = vd.type;
            if (vd.needThis())
                t = t.addMod(this.mod);
            return t;
        }
        if (auto fd = s.isFuncDeclaration())
        {
            fd = resolveFuncCall(Loc(), null, fd, null, this, null, 1);
            if (!fd || fd.errors || !fd.functionSemantic())
                return Type.terror;

            auto t = fd.type.nextOf();
            if (!t) // issue 14185
                return Type.terror;
            t = t.substWildTo(mod == 0 ? MODmutable : mod);
            return t;
        }
        if (auto d = s.isDeclaration())
        {
            assert(d.type);
            return d.type;
        }
        if (auto ed = s.isEnumDeclaration())
        {
            return ed.type;
        }
        if (auto td = s.isTemplateDeclaration())
        {
            assert(td._scope);
            auto fd = resolveFuncCall(Loc(), null, td, null, this, null, 1);
            if (!fd || fd.errors || !fd.functionSemantic())
                return Type.terror;

            auto t = fd.type.nextOf();
            if (!t)
                return Type.terror;
            t = t.substWildTo(mod == 0 ? MODmutable : mod);
            return t;
        }

        //printf("%s\n", s.kind());
        return null;
    }

    final bool checkAliasThisRec()
    {
        Type tb = toBasetype();
        AliasThisRec* pflag;
        if (tb.ty == Tstruct)
            pflag = &(cast(TypeStruct)tb).att;
        else if (tb.ty == Tclass)
            pflag = &(cast(TypeClass)tb).att;
        else
            return false;

        AliasThisRec flag = cast(AliasThisRec)(*pflag & RECtypeMask);
        if (flag == RECfwdref)
        {
            Type att = aliasthisOf();
            flag = att && att.implicitConvTo(this) ? RECyes : RECno;
        }
        *pflag = cast(AliasThisRec)(flag | (*pflag & ~RECtypeMask));
        return flag == RECyes;
    }

    Type makeConst()
    {
        //printf("Type::makeConst() %p, %s\n", this, toChars());
        if (cto)
            return cto;
        Type t = this.nullAttributes();
        t.mod = MODconst;
        //printf("-Type::makeConst() %p, %s\n", t, toChars());
        return t;
    }

    Type makeImmutable()
    {
        if (ito)
            return ito;
        Type t = this.nullAttributes();
        t.mod = MODimmutable;
        return t;
    }

    Type makeShared()
    {
        if (sto)
            return sto;
        Type t = this.nullAttributes();
        t.mod = MODshared;
        return t;
    }

    Type makeSharedConst()
    {
        if (scto)
            return scto;
        Type t = this.nullAttributes();
        t.mod = MODshared | MODconst;
        return t;
    }

    Type makeWild()
    {
        if (wto)
            return wto;
        Type t = this.nullAttributes();
        t.mod = MODwild;
        return t;
    }

    Type makeWildConst()
    {
        if (wcto)
            return wcto;
        Type t = this.nullAttributes();
        t.mod = MODwildconst;
        return t;
    }

    Type makeSharedWild()
    {
        if (swto)
            return swto;
        Type t = this.nullAttributes();
        t.mod = MODshared | MODwild;
        return t;
    }

    Type makeSharedWildConst()
    {
        if (swcto)
            return swcto;
        Type t = this.nullAttributes();
        t.mod = MODshared | MODwildconst;
        return t;
    }

    Type makeMutable()
    {
        Type t = this.nullAttributes();
        t.mod = mod & MODshared;
        return t;
    }

    Dsymbol toDsymbol(Scope* sc)
    {
        return null;
    }

    /*******************************
     * If this is a shell around another type,
     * get that other type.
     */
    Type toBasetype()
    {
        return this;
    }

    bool isBaseOf(Type t, int* poffset)
    {
        return 0; // assume not
    }

    /********************************
     * Determine if 'this' can be implicitly converted
     * to type 'to'.
     * Returns:
     *      MATCHnomatch, MATCHconvert, MATCHconst, MATCHexact
     */
    MATCH implicitConvTo(Type to)
    {
        //printf("Type::implicitConvTo(this=%p, to=%p)\n", this, to);
        //printf("from: %s\n", toChars());
        //printf("to  : %s\n", to.toChars());
        if (this.equals(to))
            return MATCHexact;
        return MATCHnomatch;
    }

    /*******************************
     * Determine if converting 'this' to 'to' is an identity operation,
     * a conversion to const operation, or the types aren't the same.
     * Returns:
     *      MATCHexact      'this' == 'to'
     *      MATCHconst      'to' is const
     *      MATCHnomatch    conversion to mutable or invariant
     */
    MATCH constConv(Type to)
    {
        //printf("Type::constConv(this = %s, to = %s)\n", toChars(), to.toChars());
        if (equals(to))
            return MATCHexact;
        if (ty == to.ty && MODimplicitConv(mod, to.mod))
            return MATCHconst;
        return MATCHnomatch;
    }

    /***************************************
     * Return MOD bits matching this type to wild parameter type (tprm).
     */
    ubyte deduceWild(Type t, bool isRef)
    {
        //printf("Type::deduceWild this = '%s', tprm = '%s'\n", toChars(), tprm.toChars());
        if (t.isWild())
        {
            if (isImmutable())
                return MODimmutable;
            else if (isWildConst())
            {
                if (t.isWildConst())
                    return MODwild;
                else
                    return MODwildconst;
            }
            else if (isWild())
                return MODwild;
            else if (isConst())
                return MODconst;
            else if (isMutable())
                return MODmutable;
            else
                assert(0);
        }
        return 0;
    }

    Type substWildTo(uint mod)
    {
        //printf("+Type::substWildTo this = %s, mod = x%x\n", toChars(), mod);
        Type t;

        if (Type tn = nextOf())
        {
            // substitution has no effect on function pointer type.
            if (ty == Tpointer && tn.ty == Tfunction)
            {
                t = this;
                goto L1;
            }

            t = tn.substWildTo(mod);
            if (t == tn)
                t = this;
            else
            {
                if (ty == Tpointer)
                    t = t.pointerTo();
                else if (ty == Tarray)
                    t = t.arrayOf();
                else if (ty == Tsarray)
                    t = new TypeSArray(t, (cast(TypeSArray)this).dim.syntaxCopy());
                else if (ty == Taarray)
                {
                    t = new TypeAArray(t, (cast(TypeAArray)this).index.syntaxCopy());
                    (cast(TypeAArray)t).sc = (cast(TypeAArray)this).sc; // duplicate scope
                }
                else if (ty == Tdelegate)
                {
                    t = new TypeDelegate(t);
                }
                else
                    assert(0);

                t = t.merge();
            }
        }
        else
            t = this;

    L1:
        if (isWild())
        {
            if (mod == MODimmutable)
            {
                t = t.immutableOf();
            }
            else if (mod == MODwildconst)
            {
                t = t.wildConstOf();
            }
            else if (mod == MODwild)
            {
                if (isWildConst())
                    t = t.wildConstOf();
                else
                    t = t.wildOf();
            }
            else if (mod == MODconst)
            {
                t = t.constOf();
            }
            else
            {
                if (isWildConst())
                    t = t.constOf();
                else
                    t = t.mutableOf();
            }
        }
        if (isConst())
            t = t.addMod(MODconst);
        if (isShared())
            t = t.addMod(MODshared);

        //printf("-Type::substWildTo t = %s\n", t.toChars());
        return t;
    }

    final Type unqualify(uint m)
    {
        Type t = mutableOf().unSharedOf();

        Type tn = ty == Tenum ? null : nextOf();
        if (tn && tn.ty != Tfunction)
        {
            Type utn = tn.unqualify(m);
            if (utn != tn)
            {
                if (ty == Tpointer)
                    t = utn.pointerTo();
                else if (ty == Tarray)
                    t = utn.arrayOf();
                else if (ty == Tsarray)
                    t = new TypeSArray(utn, (cast(TypeSArray)this).dim);
                else if (ty == Taarray)
                {
                    t = new TypeAArray(utn, (cast(TypeAArray)this).index);
                    (cast(TypeAArray)t).sc = (cast(TypeAArray)this).sc; // duplicate scope
                }
                else
                    assert(0);

                t = t.merge();
            }
        }
        t = t.addMod(mod & ~m);
        return t;
    }

    /**************************
     * Return type with the top level of it being mutable.
     */
    Type toHeadMutable()
    {
        if (!mod)
            return this;
        return mutableOf();
    }

    ClassDeclaration isClassHandle()
    {
        return null;
    }

    /***************************************
     * Calculate built-in properties which just the type is necessary.
     *
     * If flag & 1, don't report "not a property" error and just return NULL.
     */
    Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        Expression e;
        static if (LOGDOTEXP)
        {
            printf("Type::getProperty(type = '%s', ident = '%s')\n", toChars(), ident.toChars());
        }
        if (ident == Id.__sizeof)
        {
            d_uns64 sz = size(loc);
            if (sz == SIZE_INVALID)
                return new ErrorExp();
            e = new IntegerExp(loc, sz, Type.tsize_t);
        }
        else if (ident == Id.__xalignof)
        {
            e = new IntegerExp(loc, alignsize(), Type.tsize_t);
        }
        else if (ident == Id._init)
        {
            Type tb = toBasetype();
            e = defaultInitLiteral(loc);
            if (tb.ty == Tstruct && tb.needsNested())
            {
                StructLiteralExp se = cast(StructLiteralExp)e;
                se.useStaticInit = true;
            }
        }
        else if (ident == Id._mangleof)
        {
            if (!deco)
            {
                error(loc, "forward reference of type %s.mangleof", toChars());
                e = new ErrorExp();
            }
            else
            {
                e = new StringExp(loc, deco);
                Scope sc;
                e = e.semantic(&sc);
            }
        }
        else if (ident == Id.stringof)
        {
            const s = toChars();
            e = new StringExp(loc, cast(char*)s);
            Scope sc;
            e = e.semantic(&sc);
        }
        else if (flag && this != Type.terror)
        {
            return null;
        }
        else
        {
            Dsymbol s = null;
            if (ty == Tstruct || ty == Tclass || ty == Tenum)
                s = toDsymbol(null);
            if (s)
                s = s.search_correct(ident);
            if (this != Type.terror)
            {
                if (s)
                    error(loc, "no property '%s' for type '%s', did you mean '%s'?", ident.toChars(), toChars(), s.toChars());
                else
                    error(loc, "no property '%s' for type '%s'", ident.toChars(), toChars());
            }
            e = new ErrorExp();
        }
        return e;
    }

    /****************
     * dotExp() bit flags
     */
    enum DotExpFlag
    {
        gag     = 1,    // don't report "not a property" error and just return null
        noDeref = 2,    // the use of the expression will not attempt a dereference
    }

    /***************************************
     * Access the members of the object e. This type is same as e.type.
     * Params:
     *  flag = DotExpFlag bit flags
     * Returns:
     *  resulting expression with e.ident resolved
     */
    Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        VarDeclaration v = null;
        static if (LOGDOTEXP)
        {
            printf("Type::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        Expression ex = e;
        while (ex.op == TOKcomma)
            ex = (cast(CommaExp)ex).e2;
        if (ex.op == TOKdotvar)
        {
            DotVarExp dv = cast(DotVarExp)ex;
            v = dv.var.isVarDeclaration();
        }
        else if (ex.op == TOKvar)
        {
            VarExp ve = cast(VarExp)ex;
            v = ve.var.isVarDeclaration();
        }
        if (v)
        {
            if (ident == Id.offsetof)
            {
                if (v.isField())
                {
                    auto ad = v.toParent().isAggregateDeclaration();
                    ad.size(e.loc);
                    if (ad.sizeok != SIZEOKdone)
                        return new ErrorExp();
                    e = new IntegerExp(e.loc, v.offset, Type.tsize_t);
                    return e;
                }
            }
            else if (ident == Id._init)
            {
                Type tb = toBasetype();
                e = defaultInitLiteral(e.loc);
                if (tb.ty == Tstruct && tb.needsNested())
                {
                    StructLiteralExp se = cast(StructLiteralExp)e;
                    se.useStaticInit = true;
                }
                goto Lreturn;
            }
        }
        if (ident == Id.stringof)
        {
            /* https://issues.dlang.org/show_bug.cgi?id=3796
             * this should demangle e.type.deco rather than
             * pretty-printing the type.
             */
            const s = e.toChars();
            e = new StringExp(e.loc, cast(char*)s);
        }
        else
            e = getProperty(e.loc, ident, flag & DotExpFlag.gag);

    Lreturn:
        if (e)
            e = e.semantic(sc);
        return e;
    }

    /************************************
     * Return alignment to use for this type.
     */
    structalign_t alignment()
    {
        return STRUCTALIGN_DEFAULT;
    }

    /***************************************
     * Figures out what to do with an undefined member reference
     * for classes and structs.
     *
     * If flag & 1, don't report "not a property" error and just return NULL.
     */
    final Expression noMember(Scope* sc, Expression e, Identifier ident, int flag)
    {
        assert(ty == Tstruct || ty == Tclass);
        auto sym = toDsymbol(sc).isAggregateDeclaration();
        assert(sym);
        if (ident != Id.__sizeof &&
            ident != Id.__xalignof &&
            ident != Id._init &&
            ident != Id._mangleof &&
            ident != Id.stringof &&
            ident != Id.offsetof &&
            // https://issues.dlang.org/show_bug.cgi?id=15045
            // Don't forward special built-in member functions.
            ident != Id.ctor &&
            ident != Id.dtor &&
            ident != Id.__xdtor &&
            ident != Id.postblit &&
            ident != Id.__xpostblit)
        {
            /* Look for overloaded opDot() to see if we should forward request
             * to it.
             */
            if (auto fd = search_function(sym, Id.opDot))
            {
                /* Rewrite e.ident as:
                 *  e.opDot().ident
                 */
                e = build_overload(e.loc, sc, e, null, fd);
                e = new DotIdExp(e.loc, e, ident);
                return e.semantic(sc);
            }

            /* Look for overloaded opDispatch to see if we should forward request
             * to it.
             */
            if (auto fd = search_function(sym, Id.opDispatch))
            {
                /* Rewrite e.ident as:
                 *  e.opDispatch!("ident")
                 */
                TemplateDeclaration td = fd.isTemplateDeclaration();
                if (!td)
                {
                    fd.error("must be a template opDispatch(string s), not a %s", fd.kind());
                    return new ErrorExp();
                }
                auto se = new StringExp(e.loc, cast(char*)ident.toChars());
                auto tiargs = new Objects();
                tiargs.push(se);
                auto dti = new DotTemplateInstanceExp(e.loc, e, Id.opDispatch, tiargs);
                dti.ti.tempdecl = td;
                /* opDispatch, which doesn't need IFTI,  may occur instantiate error.
                 * It should be gagged if flag & 1.
                 * e.g.
                 *  template opDispatch(name) if (isValid!name) { ... }
                 */
                uint errors = flag & 1 ? global.startGagging() : 0;
                e = dti.semanticY(sc, 0);
                if (flag & 1 && global.endGagging(errors))
                    e = null;
                return e;
            }

            /* See if we should forward to the alias this.
             */
            if (sym.aliasthis)
            {
                /* Rewrite e.ident as:
                 *  e.aliasthis.ident
                 */
                e = resolveAliasThis(sc, e);
                auto die = new DotIdExp(e.loc, e, ident);
                return die.semanticY(sc, flag & 1);
            }
        }
        return Type.dotExp(sc, e, ident, flag);
    }

    Expression defaultInit(Loc loc = Loc())
    {
        static if (LOGDEFAULTINIT)
        {
            printf("Type::defaultInit() '%s'\n", toChars());
        }
        return null;
    }

    /***************************************
     * Use when we prefer the default initializer to be a literal,
     * rather than a global immutable variable.
     */
    Expression defaultInitLiteral(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("Type::defaultInitLiteral() '%s'\n", toChars());
        }
        return defaultInit(loc);
    }

    // if initializer is 0
    bool isZeroInit(Loc loc = Loc())
    {
        return false; // assume not
    }

    final Identifier getTypeInfoIdent()
    {
        // _init_10TypeInfo_%s
        OutBuffer buf;
        buf.reserve(32);
        mangleToBuffer(this, &buf);

        const slice = buf.peekSlice();

        // Allocate buffer on stack, fail over to using malloc()
        char[128] namebuf;
        const namelen = 19 + size_t.sizeof * 3 + slice.length + 1;
        auto name = namelen <= namebuf.length ? namebuf.ptr : cast(char*)malloc(namelen);
        assert(name);

        const length = sprintf(name, "_D%lluTypeInfo_%.*s6__initZ",
                cast(ulong)(9 + slice.length), cast(int)slice.length, slice.ptr);
        //printf("%p %s, deco = %s, name = %s\n", this, toChars(), deco, name);
        assert(0 < length && length < namelen); // don't overflow the buffer

        int off = 0;
        static if (!IN_GCC)
        {
            if (global.params.isOSX || global.params.isWindows && !global.params.is64bit)
                ++off; // C mangling will add '_' back in
        }
        auto id = Identifier.idPool(name + off, length - off);

        if (name != namebuf.ptr)
            free(name);
        return id;
    }

    /***************************************
     * Resolve 'this' type to either type, symbol, or expression.
     * If errors happened, resolved to Type.terror.
     */
    void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        //printf("Type::resolve() %s, %d\n", toChars(), ty);
        Type t = semantic(loc, sc);
        *pt = t;
        *pe = null;
        *ps = null;
    }

    /***************************************
     * Normalize `e` as the result of Type.resolve() process.
     */
    final void resolveExp(Expression e, Type *pt, Expression *pe, Dsymbol* ps)
    {
        *pt = null;
        *pe = null;
        *ps = null;

        Dsymbol s;
        switch (e.op)
        {
            case TOKerror:
                *pt = Type.terror;
                return;

            case TOKtype:
                *pt = e.type;
                return;

            case TOKvar:
                s = (cast(VarExp)e).var;
                if (s.isVarDeclaration())
                    goto default;
                //if (s.isOverDeclaration())
                //    todo;
                break;

            case TOKtemplate:
                // TemplateDeclaration
                s = (cast(TemplateExp)e).td;
                break;

            case TOKscope:
                s = (cast(ScopeExp)e).sds;
                // TemplateDeclaration, TemplateInstance, Import, Package, Module
                break;

            case TOKfunction:
                s = getDsymbol(e);
                break;

            //case TOKthis:
            //case TOKsuper:

            //case TOKtuple:

            //case TOKoverloadset:

            //case TOKdotvar:
            //case TOKdottd:
            //case TOKdotti:
            //case TOKdottype:
            //case TOKdotid:

            default:
                *pe = e;
                return;
        }

        *ps = s;
    }

    /***************************************
     * Return !=0 if the type or any of its subtypes is wild.
     */
    int hasWild() const
    {
        return mod & MODwild;
    }

    /********************************
     * We've mistakenly parsed this as a type.
     * Redo it as an Expression.
     * NULL if cannot.
     */
    Expression toExpression()
    {
        return null;
    }

    /***************************************
     * Return !=0 if type has pointers that need to
     * be scanned by the GC during a collection cycle.
     */
    bool hasPointers()
    {
        //printf("Type::hasPointers() %s, %d\n", toChars(), ty);
        return false;
    }

    /*************************************
     * Detect if type has pointer fields that are initialized to void.
     * Local stack variables with such void fields can remain uninitialized,
     * leading to pointer bugs.
     * Returns:
     *  true if so
     */
    bool hasVoidInitPointers()
    {
        return false;
    }

    /*************************************
     * If this is a type of something, return that something.
     */
    Type nextOf()
    {
        return null;
    }

    /*************************************
     * If this is a type of static array, return its base element type.
     */
    final Type baseElemOf()
    {
        Type t = toBasetype();
        while (t.ty == Tsarray)
            t = (cast(TypeSArray)t).next.toBasetype();
        return t;
    }

    /****************************************
     * Return the mask that an integral type will
     * fit into.
     */
    final uinteger_t sizemask()
    {
        uinteger_t m;
        switch (toBasetype().ty)
        {
        case Tbool:
            m = 1;
            break;
        case Tchar:
        case Tint8:
        case Tuns8:
            m = 0xFF;
            break;
        case Twchar:
        case Tint16:
        case Tuns16:
            m = 0xFFFFU;
            break;
        case Tdchar:
        case Tint32:
        case Tuns32:
            m = 0xFFFFFFFFU;
            break;
        case Tint64:
        case Tuns64:
            m = 0xFFFFFFFFFFFFFFFFUL;
            break;
        default:
            assert(0);
        }
        return m;
    }

    /********************************
     * true if when type goes out of scope, it needs a destructor applied.
     * Only applies to value types, not ref types.
     */
    bool needsDestruction()
    {
        return false;
    }

    /*********************************
     *
     */
    bool needsNested()
    {
        return false;
    }

    /*************************************
     * https://issues.dlang.org/show_bug.cgi?id=14488
     * Check if the inner most base type is complex or imaginary.
     * Should only give alerts when set to emit transitional messages.
     */
    final void checkComplexTransition(Loc loc)
    {
        Type t = baseElemOf();
        while (t.ty == Tpointer || t.ty == Tarray)
            t = t.nextOf().baseElemOf();

        if (t.isimaginary() || t.iscomplex())
        {
            const(char)* p = loc.toChars();
            Type rt;
            switch (t.ty)
            {
            case Tcomplex32:
            case Timaginary32:
                rt = Type.tfloat32;
                break;

            case Tcomplex64:
            case Timaginary64:
                rt = Type.tfloat64;
                break;

            case Tcomplex80:
            case Timaginary80:
                rt = Type.tfloat80;
                break;

            default:
                assert(0);
            }
            if (t.iscomplex())
            {
                fprintf(global.stdmsg, "%s: use of complex type '%s' is scheduled for deprecation, use 'std.complex.Complex!(%s)' instead\n", p ? p : "", toChars(), rt.toChars());
            }
            else
            {
                fprintf(global.stdmsg, "%s: use of imaginary type '%s' is scheduled for deprecation, use '%s' instead\n", p ? p : "", toChars(), rt.toChars());
            }
        }
    }

    static void error(Loc loc, const(char)* format, ...)
    {
        va_list ap;
        va_start(ap, format);
        .verror(loc, format, ap);
        va_end(ap);
    }

    static void warning(Loc loc, const(char)* format, ...)
    {
        va_list ap;
        va_start(ap, format);
        .vwarning(loc, format, ap);
        va_end(ap);
    }

    // For eliminating dynamic_cast
    TypeBasic isTypeBasic()
    {
        return null;
    }

    void accept(Visitor v)
    {
        v.visit(this);
    }

    final TypeFunction toTypeFunction()
    {
        if (ty != Tfunction)
            assert(0);
        return cast(TypeFunction)this;
    }
}

/***********************************************************
 */
extern (C++) final class TypeError : Type
{
    extern (D) this()
    {
        super(Terror);
    }

    override Type syntaxCopy()
    {
        // No semantic analysis done, no need to copy
        return this;
    }

    override d_uns64 size(Loc loc)
    {
        return SIZE_INVALID;
    }

    override Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        return new ErrorExp();
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        return new ErrorExp();
    }

    override Expression defaultInit(Loc loc)
    {
        return new ErrorExp();
    }

    override Expression defaultInitLiteral(Loc loc)
    {
        return new ErrorExp();
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) abstract class TypeNext : Type
{
    Type next;

    final extern (D) this(TY ty, Type next)
    {
        super(ty);
        this.next = next;
    }

    override final void checkDeprecated(Loc loc, Scope* sc)
    {
        Type.checkDeprecated(loc, sc);
        if (next) // next can be NULL if TypeFunction and auto return type
            next.checkDeprecated(loc, sc);
    }

    override final int hasWild() const
    {
        if (ty == Tfunction)
            return 0;
        if (ty == Tdelegate)
            return Type.hasWild();
        return mod & MODwild || (next && next.hasWild());
    }

    /*******************************
     * For TypeFunction, nextOf() can return NULL if the function return
     * type is meant to be inferred, and semantic() hasn't yet ben run
     * on the function. After semantic(), it must no longer be NULL.
     */
    override final Type nextOf()
    {
        return next;
    }

    override final Type makeConst()
    {
        //printf("TypeNext::makeConst() %p, %s\n", this, toChars());
        if (cto)
        {
            assert(cto.mod == MODconst);
            return cto;
        }
        TypeNext t = cast(TypeNext)Type.makeConst();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isShared())
            {
                if (next.isWild())
                    t.next = next.sharedWildConstOf();
                else
                    t.next = next.sharedConstOf();
            }
            else
            {
                if (next.isWild())
                    t.next = next.wildConstOf();
                else
                    t.next = next.constOf();
            }
        }
        //printf("TypeNext::makeConst() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeImmutable()
    {
        //printf("TypeNext::makeImmutable() %s\n", toChars());
        if (ito)
        {
            assert(ito.isImmutable());
            return ito;
        }
        TypeNext t = cast(TypeNext)Type.makeImmutable();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            t.next = next.immutableOf();
        }
        return t;
    }

    override final Type makeShared()
    {
        //printf("TypeNext::makeShared() %s\n", toChars());
        if (sto)
        {
            assert(sto.mod == MODshared);
            return sto;
        }
        TypeNext t = cast(TypeNext)Type.makeShared();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isWild())
            {
                if (next.isConst())
                    t.next = next.sharedWildConstOf();
                else
                    t.next = next.sharedWildOf();
            }
            else
            {
                if (next.isConst())
                    t.next = next.sharedConstOf();
                else
                    t.next = next.sharedOf();
            }
        }
        //printf("TypeNext::makeShared() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeSharedConst()
    {
        //printf("TypeNext::makeSharedConst() %s\n", toChars());
        if (scto)
        {
            assert(scto.mod == (MODshared | MODconst));
            return scto;
        }
        TypeNext t = cast(TypeNext)Type.makeSharedConst();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isWild())
                t.next = next.sharedWildConstOf();
            else
                t.next = next.sharedConstOf();
        }
        //printf("TypeNext::makeSharedConst() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeWild()
    {
        //printf("TypeNext::makeWild() %s\n", toChars());
        if (wto)
        {
            assert(wto.mod == MODwild);
            return wto;
        }
        TypeNext t = cast(TypeNext)Type.makeWild();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isShared())
            {
                if (next.isConst())
                    t.next = next.sharedWildConstOf();
                else
                    t.next = next.sharedWildOf();
            }
            else
            {
                if (next.isConst())
                    t.next = next.wildConstOf();
                else
                    t.next = next.wildOf();
            }
        }
        //printf("TypeNext::makeWild() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeWildConst()
    {
        //printf("TypeNext::makeWildConst() %s\n", toChars());
        if (wcto)
        {
            assert(wcto.mod == MODwildconst);
            return wcto;
        }
        TypeNext t = cast(TypeNext)Type.makeWildConst();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isShared())
                t.next = next.sharedWildConstOf();
            else
                t.next = next.wildConstOf();
        }
        //printf("TypeNext::makeWildConst() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeSharedWild()
    {
        //printf("TypeNext::makeSharedWild() %s\n", toChars());
        if (swto)
        {
            assert(swto.isSharedWild());
            return swto;
        }
        TypeNext t = cast(TypeNext)Type.makeSharedWild();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            if (next.isConst())
                t.next = next.sharedWildConstOf();
            else
                t.next = next.sharedWildOf();
        }
        //printf("TypeNext::makeSharedWild() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeSharedWildConst()
    {
        //printf("TypeNext::makeSharedWildConst() %s\n", toChars());
        if (swcto)
        {
            assert(swcto.mod == (MODshared | MODwildconst));
            return swcto;
        }
        TypeNext t = cast(TypeNext)Type.makeSharedWildConst();
        if (ty != Tfunction && next.ty != Tfunction && !next.isImmutable())
        {
            t.next = next.sharedWildConstOf();
        }
        //printf("TypeNext::makeSharedWildConst() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override final Type makeMutable()
    {
        //printf("TypeNext::makeMutable() %p, %s\n", this, toChars());
        TypeNext t = cast(TypeNext)Type.makeMutable();
        if (ty == Tsarray)
        {
            t.next = next.mutableOf();
        }
        //printf("TypeNext::makeMutable() returns %p, %s\n", t, t.toChars());
        return t;
    }

    override MATCH constConv(Type to)
    {
        //printf("TypeNext::constConv from = %s, to = %s\n", toChars(), to.toChars());
        if (equals(to))
            return MATCHexact;

        if (!(ty == to.ty && MODimplicitConv(mod, to.mod)))
            return MATCHnomatch;

        Type tn = to.nextOf();
        if (!(tn && next.ty == tn.ty))
            return MATCHnomatch;

        MATCH m;
        if (to.isConst()) // whole tail const conversion
        {
            // Recursive shared level check
            m = next.constConv(tn);
            if (m == MATCHexact)
                m = MATCHconst;
        }
        else
        {
            //printf("\tnext => %s, to.next => %s\n", next.toChars(), tn.toChars());
            m = next.equals(tn) ? MATCHconst : MATCHnomatch;
        }
        return m;
    }

    override final ubyte deduceWild(Type t, bool isRef)
    {
        if (ty == Tfunction)
            return 0;

        ubyte wm;

        Type tn = t.nextOf();
        if (!isRef && (ty == Tarray || ty == Tpointer) && tn)
        {
            wm = next.deduceWild(tn, true);
            if (!wm)
                wm = Type.deduceWild(t, true);
        }
        else
        {
            wm = Type.deduceWild(t, isRef);
            if (!wm && tn)
                wm = next.deduceWild(tn, true);
        }

        return wm;
    }

    final void transitive()
    {
        /* Invoke transitivity of type attributes
         */
        next = next.addMod(mod);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeBasic : Type
{
    const(char)* dstring;
    uint flags;

    extern (D) this(TY ty)
    {
        super(ty);
        const(char)* d;
        uint flags = 0;
        switch (ty)
        {
        case Tvoid:
            d = Token.toChars(TOKvoid);
            break;

        case Tint8:
            d = Token.toChars(TOKint8);
            flags |= TFLAGSintegral;
            break;

        case Tuns8:
            d = Token.toChars(TOKuns8);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tint16:
            d = Token.toChars(TOKint16);
            flags |= TFLAGSintegral;
            break;

        case Tuns16:
            d = Token.toChars(TOKuns16);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tint32:
            d = Token.toChars(TOKint32);
            flags |= TFLAGSintegral;
            break;

        case Tuns32:
            d = Token.toChars(TOKuns32);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tfloat32:
            d = Token.toChars(TOKfloat32);
            flags |= TFLAGSfloating | TFLAGSreal;
            break;

        case Tint64:
            d = Token.toChars(TOKint64);
            flags |= TFLAGSintegral;
            break;

        case Tuns64:
            d = Token.toChars(TOKuns64);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tint128:
            d = Token.toChars(TOKint128);
            flags |= TFLAGSintegral;
            break;

        case Tuns128:
            d = Token.toChars(TOKuns128);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tfloat64:
            d = Token.toChars(TOKfloat64);
            flags |= TFLAGSfloating | TFLAGSreal;
            break;

        case Tfloat80:
            d = Token.toChars(TOKfloat80);
            flags |= TFLAGSfloating | TFLAGSreal;
            break;

        case Timaginary32:
            d = Token.toChars(TOKimaginary32);
            flags |= TFLAGSfloating | TFLAGSimaginary;
            break;

        case Timaginary64:
            d = Token.toChars(TOKimaginary64);
            flags |= TFLAGSfloating | TFLAGSimaginary;
            break;

        case Timaginary80:
            d = Token.toChars(TOKimaginary80);
            flags |= TFLAGSfloating | TFLAGSimaginary;
            break;

        case Tcomplex32:
            d = Token.toChars(TOKcomplex32);
            flags |= TFLAGSfloating | TFLAGScomplex;
            break;

        case Tcomplex64:
            d = Token.toChars(TOKcomplex64);
            flags |= TFLAGSfloating | TFLAGScomplex;
            break;

        case Tcomplex80:
            d = Token.toChars(TOKcomplex80);
            flags |= TFLAGSfloating | TFLAGScomplex;
            break;

        case Tbool:
            d = "bool";
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tchar:
            d = Token.toChars(TOKchar);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Twchar:
            d = Token.toChars(TOKwchar);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        case Tdchar:
            d = Token.toChars(TOKdchar);
            flags |= TFLAGSintegral | TFLAGSunsigned;
            break;

        default:
            assert(0);
        }
        this.dstring = d;
        this.flags = flags;
        merge();
    }

    override const(char)* kind() const
    {
        return dstring;
    }

    override Type syntaxCopy()
    {
        // No semantic analysis done on basic types, no need to copy
        return this;
    }

    override d_uns64 size(Loc loc) const
    {
        uint size;
        //printf("TypeBasic::size()\n");
        switch (ty)
        {
        case Tint8:
        case Tuns8:
            size = 1;
            break;

        case Tint16:
        case Tuns16:
            size = 2;
            break;

        case Tint32:
        case Tuns32:
        case Tfloat32:
        case Timaginary32:
            size = 4;
            break;

        case Tint64:
        case Tuns64:
        case Tfloat64:
        case Timaginary64:
            size = 8;
            break;

        case Tfloat80:
        case Timaginary80:
            size = Target.realsize;
            break;

        case Tcomplex32:
            size = 8;
            break;

        case Tcomplex64:
        case Tint128:
        case Tuns128:
            size = 16;
            break;

        case Tcomplex80:
            size = Target.realsize * 2;
            break;

        case Tvoid:
            //size = Type::size();      // error message
            size = 1;
            break;

        case Tbool:
            size = 1;
            break;

        case Tchar:
            size = 1;
            break;

        case Twchar:
            size = 2;
            break;

        case Tdchar:
            size = 4;
            break;

        default:
            assert(0);
        }
        //printf("TypeBasic::size() = %d\n", size);
        return size;
    }

    override uint alignsize()
    {
        return Target.alignsize(this);
    }

    override Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        Expression e;
        dinteger_t ivalue;
        real_t fvalue = 0;
        //printf("TypeBasic::getProperty('%s')\n", ident.toChars());
        if (ident == Id.max)
        {
            switch (ty)
            {
            case Tint8:
                ivalue = 0x7F;
                goto Livalue;
            case Tuns8:
                ivalue = 0xFF;
                goto Livalue;
            case Tint16:
                ivalue = 0x7FFFU;
                goto Livalue;
            case Tuns16:
                ivalue = 0xFFFFU;
                goto Livalue;
            case Tint32:
                ivalue = 0x7FFFFFFFU;
                goto Livalue;
            case Tuns32:
                ivalue = 0xFFFFFFFFU;
                goto Livalue;
            case Tint64:
                ivalue = 0x7FFFFFFFFFFFFFFFL;
                goto Livalue;
            case Tuns64:
                ivalue = 0xFFFFFFFFFFFFFFFFUL;
                goto Livalue;
            case Tbool:
                ivalue = 1;
                goto Livalue;
            case Tchar:
                ivalue = 0xFF;
                goto Livalue;
            case Twchar:
                ivalue = 0xFFFFU;
                goto Livalue;
            case Tdchar:
                ivalue = 0x10FFFFU;
                goto Livalue;
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                fvalue = Target.FloatProperties.max;
                goto Lfvalue;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                fvalue = Target.DoubleProperties.max;
                goto Lfvalue;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                fvalue = Target.RealProperties.max;
                goto Lfvalue;
            default:
                break;
            }
        }
        else if (ident == Id.min)
        {
            switch (ty)
            {
            case Tint8:
                ivalue = -128;
                goto Livalue;
            case Tuns8:
                ivalue = 0;
                goto Livalue;
            case Tint16:
                ivalue = -32768;
                goto Livalue;
            case Tuns16:
                ivalue = 0;
                goto Livalue;
            case Tint32:
                ivalue = -2147483647 - 1;
                goto Livalue;
            case Tuns32:
                ivalue = 0;
                goto Livalue;
            case Tint64:
                ivalue = (-9223372036854775807L - 1L);
                goto Livalue;
            case Tuns64:
                ivalue = 0;
                goto Livalue;
            case Tbool:
                ivalue = 0;
                goto Livalue;
            case Tchar:
                ivalue = 0;
                goto Livalue;
            case Twchar:
                ivalue = 0;
                goto Livalue;
            case Tdchar:
                ivalue = 0;
                goto Livalue;
            default:
                break;
            }
        }
        else if (ident == Id.min_normal)
        {
        Lmin_normal:
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                fvalue = Target.FloatProperties.min_normal;
                goto Lfvalue;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                fvalue = Target.DoubleProperties.min_normal;
                goto Lfvalue;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                fvalue = Target.RealProperties.min_normal;
                goto Lfvalue;
            default:
                break;
            }
        }
        else if (ident == Id.nan)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Tcomplex64:
            case Tcomplex80:
            case Timaginary32:
            case Timaginary64:
            case Timaginary80:
            case Tfloat32:
            case Tfloat64:
            case Tfloat80:
                fvalue = Target.RealProperties.nan;
                goto Lfvalue;
            default:
                break;
            }
        }
        else if (ident == Id.infinity)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Tcomplex64:
            case Tcomplex80:
            case Timaginary32:
            case Timaginary64:
            case Timaginary80:
            case Tfloat32:
            case Tfloat64:
            case Tfloat80:
                fvalue = Target.RealProperties.infinity;
                goto Lfvalue;
            default:
                break;
            }
        }
        else if (ident == Id.dig)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.dig;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.dig;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.dig;
                goto Lint;
            default:
                break;
            }
        }
        else if (ident == Id.epsilon)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                fvalue = Target.FloatProperties.epsilon;
                goto Lfvalue;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                fvalue = Target.DoubleProperties.epsilon;
                goto Lfvalue;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                fvalue = Target.RealProperties.epsilon;
                goto Lfvalue;
            default:
                break;
            }
        }
        else if (ident == Id.mant_dig)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.mant_dig;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.mant_dig;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.mant_dig;
                goto Lint;
            default:
                break;
            }
        }
        else if (ident == Id.max_10_exp)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.max_10_exp;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.max_10_exp;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.max_10_exp;
                goto Lint;
            default:
                break;
            }
        }
        else if (ident == Id.max_exp)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.max_exp;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.max_exp;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.max_exp;
                goto Lint;
            default:
                break;
            }
        }
        else if (ident == Id.min_10_exp)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.min_10_exp;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.min_10_exp;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.min_10_exp;
                goto Lint;
            default:
                break;
            }
        }
        else if (ident == Id.min_exp)
        {
            switch (ty)
            {
            case Tcomplex32:
            case Timaginary32:
            case Tfloat32:
                ivalue = Target.FloatProperties.min_exp;
                goto Lint;
            case Tcomplex64:
            case Timaginary64:
            case Tfloat64:
                ivalue = Target.DoubleProperties.min_exp;
                goto Lint;
            case Tcomplex80:
            case Timaginary80:
            case Tfloat80:
                ivalue = Target.RealProperties.min_exp;
                goto Lint;
            default:
                break;
            }
        }
        return Type.getProperty(loc, ident, flag);

    Livalue:
        e = new IntegerExp(loc, ivalue, this);
        return e;

    Lfvalue:
        if (isreal() || isimaginary())
            e = new RealExp(loc, fvalue, this);
        else
        {
            const cvalue = complex_t(fvalue, fvalue);
            //for (int i = 0; i < 20; i++)
            //    printf("%02x ", ((unsigned char *)&cvalue)[i]);
            //printf("\n");
            e = new ComplexExp(loc, cvalue, this);
        }
        return e;

    Lint:
        e = new IntegerExp(loc, ivalue, Type.tint32);
        return e;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeBasic::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        Type t;
        if (ident == Id.re)
        {
            switch (ty)
            {
            case Tcomplex32:
                t = tfloat32;
                goto L1;

            case Tcomplex64:
                t = tfloat64;
                goto L1;

            case Tcomplex80:
                t = tfloat80;
                goto L1;
            L1:
                e = e.castTo(sc, t);
                break;

            case Tfloat32:
            case Tfloat64:
            case Tfloat80:
                break;

            case Timaginary32:
                t = tfloat32;
                goto L2;

            case Timaginary64:
                t = tfloat64;
                goto L2;

            case Timaginary80:
                t = tfloat80;
                goto L2;
            L2:
                e = new RealExp(e.loc, CTFloat.zero, t);
                break;

            default:
                e = Type.getProperty(e.loc, ident, flag);
                break;
            }
        }
        else if (ident == Id.im)
        {
            Type t2;
            switch (ty)
            {
            case Tcomplex32:
                t = timaginary32;
                t2 = tfloat32;
                goto L3;

            case Tcomplex64:
                t = timaginary64;
                t2 = tfloat64;
                goto L3;

            case Tcomplex80:
                t = timaginary80;
                t2 = tfloat80;
                goto L3;
            L3:
                e = e.castTo(sc, t);
                e.type = t2;
                break;

            case Timaginary32:
                t = tfloat32;
                goto L4;

            case Timaginary64:
                t = tfloat64;
                goto L4;

            case Timaginary80:
                t = tfloat80;
                goto L4;
            L4:
                e = e.copy();
                e.type = t;
                break;

            case Tfloat32:
            case Tfloat64:
            case Tfloat80:
                e = new RealExp(e.loc, CTFloat.zero, this);
                break;

            default:
                e = Type.getProperty(e.loc, ident, flag);
                break;
            }
        }
        else
        {
            return Type.dotExp(sc, e, ident, flag);
        }
        if (!(flag & 1) || e)
            e = e.semantic(sc);
        return e;
    }

    override bool isintegral()
    {
        //printf("TypeBasic::isintegral('%s') x%x\n", toChars(), flags);
        return (flags & TFLAGSintegral) != 0;
    }

    override bool isfloating() const
    {
        return (flags & TFLAGSfloating) != 0;
    }

    override bool isreal() const
    {
        return (flags & TFLAGSreal) != 0;
    }

    override bool isimaginary() const
    {
        return (flags & TFLAGSimaginary) != 0;
    }

    override bool iscomplex() const
    {
        return (flags & TFLAGScomplex) != 0;
    }

    override bool isscalar() const
    {
        return (flags & (TFLAGSintegral | TFLAGSfloating)) != 0;
    }

    override bool isunsigned() const
    {
        return (flags & TFLAGSunsigned) != 0;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeBasic::implicitConvTo(%s) from %s\n", to.toChars(), toChars());
        if (this == to)
            return MATCHexact;

        if (ty == to.ty)
        {
            if (mod == to.mod)
                return MATCHexact;
            else if (MODimplicitConv(mod, to.mod))
                return MATCHconst;
            else if (!((mod ^ to.mod) & MODshared)) // for wild matching
                return MATCHconst;
            else
                return MATCHconvert;
        }

        if (ty == Tvoid || to.ty == Tvoid)
            return MATCHnomatch;
        if (to.ty == Tbool)
            return MATCHnomatch;

        TypeBasic tob;
        if (to.ty == Tvector && to.deco)
        {
            TypeVector tv = cast(TypeVector)to;
            tob = tv.elementType();
        }
        else
            tob = to.isTypeBasic();
        if (!tob)
            return MATCHnomatch;

        if (flags & TFLAGSintegral)
        {
            // Disallow implicit conversion of integers to imaginary or complex
            if (tob.flags & (TFLAGSimaginary | TFLAGScomplex))
                return MATCHnomatch;

            // If converting from integral to integral
            if (tob.flags & TFLAGSintegral)
            {
                d_uns64 sz = size(Loc());
                d_uns64 tosz = tob.size(Loc());

                /* Can't convert to smaller size
                 */
                if (sz > tosz)
                    return MATCHnomatch;
                /* Can't change sign if same size
                 */
                //if (sz == tosz && (flags ^ tob.flags) & TFLAGSunsigned)
                //    return MATCHnomatch;
            }
        }
        else if (flags & TFLAGSfloating)
        {
            // Disallow implicit conversion of floating point to integer
            if (tob.flags & TFLAGSintegral)
                return MATCHnomatch;

            assert(tob.flags & TFLAGSfloating || to.ty == Tvector);

            // Disallow implicit conversion from complex to non-complex
            if (flags & TFLAGScomplex && !(tob.flags & TFLAGScomplex))
                return MATCHnomatch;

            // Disallow implicit conversion of real or imaginary to complex
            if (flags & (TFLAGSreal | TFLAGSimaginary) && tob.flags & TFLAGScomplex)
                return MATCHnomatch;

            // Disallow implicit conversion to-from real and imaginary
            if ((flags & (TFLAGSreal | TFLAGSimaginary)) != (tob.flags & (TFLAGSreal | TFLAGSimaginary)))
                return MATCHnomatch;
        }
        return MATCHconvert;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeBasic::defaultInit() '%s'\n", toChars());
        }
        dinteger_t value = 0;

        switch (ty)
        {
        case Tchar:
            value = 0xFF;
            break;

        case Twchar:
        case Tdchar:
            value = 0xFFFF;
            break;

        case Timaginary32:
        case Timaginary64:
        case Timaginary80:
        case Tfloat32:
        case Tfloat64:
        case Tfloat80:
            return new RealExp(loc, Target.RealProperties.snan, this);

        case Tcomplex32:
        case Tcomplex64:
        case Tcomplex80:
            {
                // Can't use fvalue + I*fvalue (the im part becomes a quiet NaN).
                const cvalue = complex_t(Target.RealProperties.snan, Target.RealProperties.snan);
                return new ComplexExp(loc, cvalue, this);
            }

        case Tvoid:
            error(loc, "void does not have a default initializer");
            return new ErrorExp();

        default:
            break;
        }
        return new IntegerExp(loc, value, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        switch (ty)
        {
        case Tchar:
        case Twchar:
        case Tdchar:
        case Timaginary32:
        case Timaginary64:
        case Timaginary80:
        case Tfloat32:
        case Tfloat64:
        case Tfloat80:
        case Tcomplex32:
        case Tcomplex64:
        case Tcomplex80:
            return false; // no
        default:
            return true; // yes
        }
    }

    // For eliminating dynamic_cast
    override TypeBasic isTypeBasic()
    {
        return this;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 * The basetype must be one of:
 *   byte[16],ubyte[16],short[8],ushort[8],int[4],uint[4],long[2],ulong[2],float[4],double[2]
 * For AVX:
 *   byte[32],ubyte[32],short[16],ushort[16],int[8],uint[8],long[4],ulong[4],float[8],double[4]
 */
extern (C++) final class TypeVector : Type
{
    Type basetype;

    extern (D) this(Loc loc, Type basetype)
    {
        super(Tvector);
        this.basetype = basetype;
    }

    override const(char)* kind() const
    {
        return "vector";
    }

    override Type syntaxCopy()
    {
        return new TypeVector(Loc(), basetype.syntaxCopy());
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        uint errors = global.errors;
        basetype = basetype.semantic(loc, sc);
        if (errors != global.errors)
            return terror;
        basetype = basetype.toBasetype().mutableOf();
        if (basetype.ty != Tsarray)
        {
            error(loc, "T in __vector(T) must be a static array, not %s", basetype.toChars());
            return terror;
        }
        TypeSArray t = cast(TypeSArray)basetype;
        int sz = cast(int)t.size(loc);
        switch (Target.isVectorTypeSupported(sz, t.nextOf()))
        {
        case 0:
            // valid
            break;
        case 1:
            // no support at all
            error(loc, "SIMD vector types not supported on this platform");
            return terror;
        case 2:
            // invalid size
            error(loc, "%d byte vector type %s is not supported on this platform", sz, toChars());
            return terror;
        case 3:
            // invalid base type
            error(loc, "vector type %s is not supported on this platform", toChars());
            return terror;
        default:
            assert(0);
        }
        return merge();
    }

    override d_uns64 size(Loc loc)
    {
        return basetype.size();
    }

    override uint alignsize()
    {
        return cast(uint)basetype.size();
    }

    override Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        return Type.getProperty(loc, ident, flag);
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeVector::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        if (ident == Id.ptr && e.op == TOKcall)
        {
            /* The trouble with TOKcall is the return ABI for float[4] is different from
             * __vector(float[4]), and a type paint won't do.
             */
            e = new AddrExp(e.loc, e);
            e = e.semantic(sc);
            e = e.castTo(sc, basetype.nextOf().pointerTo());
            return e;
        }
        if (ident == Id.array)
        {
            //e = e.castTo(sc, basetype);
            // Keep lvalue-ness
            e = e.copy();
            e.type = basetype;
            return e;
        }
        if (ident == Id._init || ident == Id.offsetof || ident == Id.stringof || ident == Id.__xalignof)
        {
            // init should return a new VectorExp
            // https://issues.dlang.org/show_bug.cgi?id=12776
            // offsetof does not work on a cast expression, so use e directly
            // stringof should not add a cast to the output
            return Type.dotExp(sc, e, ident, flag);
        }
        return basetype.dotExp(sc, e.castTo(sc, basetype), ident, flag);
    }

    override bool isintegral()
    {
        //printf("TypeVector::isintegral('%s') x%x\n", toChars(), flags);
        return basetype.nextOf().isintegral();
    }

    override bool isfloating()
    {
        return basetype.nextOf().isfloating();
    }

    override bool isscalar()
    {
        return basetype.nextOf().isscalar();
    }

    override bool isunsigned()
    {
        return basetype.nextOf().isunsigned();
    }

    override bool isBoolean() const
    {
        return false;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeVector::implicitConvTo(%s) from %s\n", to.toChars(), toChars());
        if (this == to)
            return MATCHexact;
        if (ty == to.ty)
            return MATCHconvert;
        return MATCHnomatch;
    }

    override Expression defaultInit(Loc loc)
    {
        //printf("TypeVector::defaultInit()\n");
        assert(basetype.ty == Tsarray);
        Expression e = basetype.defaultInit(loc);
        auto ve = new VectorExp(loc, e, this);
        ve.type = this;
        ve.dim = cast(int)(basetype.size(loc) / elementType().size(loc));
        return ve;
    }

    override Expression defaultInitLiteral(Loc loc)
    {
        //printf("TypeVector::defaultInitLiteral()\n");
        assert(basetype.ty == Tsarray);
        Expression e = basetype.defaultInitLiteral(loc);
        auto ve = new VectorExp(loc, e, this);
        ve.type = this;
        ve.dim = cast(int)(basetype.size(loc) / elementType().size(loc));
        return ve;
    }

    TypeBasic elementType()
    {
        assert(basetype.ty == Tsarray);
        TypeSArray t = cast(TypeSArray)basetype;
        TypeBasic tb = t.nextOf().isTypeBasic();
        assert(tb);
        return tb;
    }

    override bool isZeroInit(Loc loc)
    {
        return basetype.isZeroInit(loc);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) class TypeArray : TypeNext
{
    final extern (D) this(TY ty, Type next)
    {
        super(ty, next);
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        Type n = this.next.toBasetype(); // uncover any typedef's
        static if (LOGDOTEXP)
        {
            printf("TypeArray::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }

        e = Type.dotExp(sc, e, ident, flag);

        if (!(flag & 1) || e)
            e = e.semantic(sc);
        return e;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 * Static array, one with a fixed dimension
 */
extern (C++) final class TypeSArray : TypeArray
{
    Expression dim;

    extern (D) this(Type t, Expression dim)
    {
        super(Tsarray, t);
        //printf("TypeSArray(%s)\n", dim.toChars());
        this.dim = dim;
    }

    override const(char)* kind() const
    {
        return "sarray";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        Expression e = dim.syntaxCopy();
        t = new TypeSArray(t, e);
        t.mod = mod;
        return t;
    }

    override d_uns64 size(Loc loc)
    {
        //printf("TypeSArray::size()\n");
        dinteger_t sz;
        if (!dim)
            return Type.size(loc);
        sz = dim.toInteger();
        {
            bool overflow = false;
            sz = mulu(next.size(), sz, overflow);
            if (overflow)
                goto Loverflow;
        }
        if (sz > uint.max)
            goto Loverflow;
        return sz;

    Loverflow:
        error(loc, "static array %s size overflowed to %lld", toChars(), cast(long)sz);
        return SIZE_INVALID;
    }

    override uint alignsize()
    {
        return next.alignsize();
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeSArray::semantic() %s\n", toChars());

        static Type errorReturn()
        {
            return Type.terror;
        }

        Type t;
        Expression e;
        Dsymbol s;
        next.resolve(loc, sc, &e, &t, &s);

        if (auto tup = s ? s.isTupleDeclaration() : null)
        {
            dim = semanticLength(sc, tup, dim);
            dim = dim.ctfeInterpret();
            if (dim.op == TOKerror)
                return errorReturn();
            uinteger_t d = dim.toUInteger();
            if (d >= tup.objects.dim)
            {
                error(loc, "tuple index %llu exceeds %u", d, tup.objects.dim);
                return errorReturn();
            }

            RootObject o = (*tup.objects)[cast(size_t)d];
            if (o.dyncast() != DYNCAST.type)
            {
                error(loc, "%s is not a type", toChars());
                return errorReturn();
            }
            t = (cast(Type)o).addMod(this.mod);
            return t;
        }

        Type tn = next.semantic(loc, sc);
        if (tn.ty == Terror)
            return errorReturn();

        Type tbn = tn.toBasetype();
        if (dim)
        {
            uint errors = global.errors;
            dim = semanticLength(sc, tbn, dim);
            if (errors != global.errors)
                return errorReturn();

            dim = dim.optimize(WANTvalue);
            dim = dim.ctfeInterpret();
            if (dim.op == TOKerror)
                return errorReturn();
            errors = global.errors;
            dinteger_t d1 = dim.toInteger();
            if (errors != global.errors)
                return errorReturn();

            dim = dim.implicitCastTo(sc, tsize_t);
            dim = dim.optimize(WANTvalue);
            if (dim.op == TOKerror)
                return errorReturn();
            errors = global.errors;
            dinteger_t d2 = dim.toInteger();
            if (errors != global.errors)
                return errorReturn();

            if (dim.op == TOKerror)
                return errorReturn();

            if (d1 != d2)
            {
            Loverflow:
                error(loc, "%s size %llu * %llu exceeds 0x%llx size limit for static array",
                        toChars(), cast(ulong)tbn.size(loc), cast(ulong)d1, Target.maxStaticDataSize);
                return errorReturn();
            }
            Type tbx = tbn.baseElemOf();
            if (tbx.ty == Tstruct && !(cast(TypeStruct)tbx).sym.members || tbx.ty == Tenum && !(cast(TypeEnum)tbx).sym.members)
            {
                /* To avoid meaningless error message, skip the total size limit check
                 * when the bottom of element type is opaque.
                 */
            }
            else if (tbn.isintegral() || tbn.isfloating() || tbn.ty == Tpointer || tbn.ty == Tarray || tbn.ty == Tsarray || tbn.ty == Taarray || (tbn.ty == Tstruct && ((cast(TypeStruct)tbn).sym.sizeok == SIZEOKdone)) || tbn.ty == Tclass)
            {
                /* Only do this for types that don't need to have semantic()
                 * run on them for the size, since they may be forward referenced.
                 */
                bool overflow = false;
                if (mulu(tbn.size(loc), d2, overflow) >= Target.maxStaticDataSize || overflow)
                    goto Loverflow;
            }
        }
        switch (tbn.ty)
        {
        case Ttuple:
            {
                // Index the tuple to get the type
                assert(dim);
                TypeTuple tt = cast(TypeTuple)tbn;
                uinteger_t d = dim.toUInteger();
                if (d >= tt.arguments.dim)
                {
                    error(loc, "tuple index %llu exceeds %u", d, tt.arguments.dim);
                    return errorReturn();
                }
                Type telem = (*tt.arguments)[cast(size_t)d].type;
                return telem.addMod(this.mod);
            }
        case Tfunction:
        case Tnone:
            error(loc, "can't have array of %s", tbn.toChars());
            return errorReturn();
        default:
            break;
        }
        if (tbn.isscope())
        {
            error(loc, "cannot have array of scope %s", tbn.toChars());
            return errorReturn();
        }

        /* Ensure things like const(immutable(T)[3]) become immutable(T[3])
         * and const(T)[3] become const(T[3])
         */
        next = tn;
        transitive();
        t = addMod(tn.mod);

        return t.merge();
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        //printf("TypeSArray::resolve() %s\n", toChars());
        next.resolve(loc, sc, pe, pt, ps, intypeid);
        //printf("s = %p, e = %p, t = %p\n", *ps, *pe, *pt);
        if (*pe)
        {
            // It's really an index expression
            if (Dsymbol s = getDsymbol(*pe))
                *pe = new DsymbolExp(loc, s);
            *pe = new ArrayExp(loc, *pe, dim);
        }
        else if (*ps)
        {
            Dsymbol s = *ps;
            if (auto tup = s.isTupleDeclaration())
            {
                dim = semanticLength(sc, tup, dim);
                dim = dim.ctfeInterpret();
                if (dim.op == TOKerror)
                {
                    *ps = null;
                    *pt = Type.terror;
                    return;
                }
                uinteger_t d = dim.toUInteger();
                if (d >= tup.objects.dim)
                {
                    error(loc, "tuple index %llu exceeds length %u", d, tup.objects.dim);
                    *ps = null;
                    *pt = Type.terror;
                    return;
                }

                RootObject o = (*tup.objects)[cast(size_t)d];
                if (o.dyncast() == DYNCAST.dsymbol)
                {
                    *ps = cast(Dsymbol)o;
                    return;
                }
                if (o.dyncast() == DYNCAST.expression)
                {
                    Expression e = cast(Expression)o;
                    if (e.op == TOKdsymbol)
                    {
                        *ps = (cast(DsymbolExp)e).s;
                        *pe = null;
                    }
                    else
                    {
                        *ps = null;
                        *pe = e;
                    }
                    return;
                }
                if (o.dyncast() == DYNCAST.type)
                {
                    *ps = null;
                    *pt = (cast(Type)o).addMod(this.mod);
                    return;
                }

                /* Create a new TupleDeclaration which
                 * is a slice [d..d+1] out of the old one.
                 * Do it this way because TemplateInstance::semanticTiargs()
                 * can handle unresolved Objects this way.
                 */
                auto objects = new Objects();
                objects.setDim(1);
                (*objects)[0] = o;
                *ps = new TupleDeclaration(loc, tup.ident, objects);
            }
            else
                goto Ldefault;
        }
        else
        {
            if ((*pt).ty != Terror)
                next = *pt; // prevent re-running semantic() on 'next'
        Ldefault:
            Type.resolve(loc, sc, pe, pt, ps, intypeid);
        }
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeSArray::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        if (ident == Id.length)
        {
            Loc oldLoc = e.loc;
            e = dim.copy();
            e.loc = oldLoc;
        }
        else if (ident == Id.ptr)
        {
            if (e.op == TOKtype)
            {
                e.error("%s is not an expression", e.toChars());
                return new ErrorExp();
            }
            else if (!(flag & DotExpFlag.noDeref) && sc.func && !sc.intypeof && sc.func.setUnsafe())
            {
                // MAINTENANCE: turn into error in 2.073
                e.deprecation("%s.ptr cannot be used in @safe code, use &%s[0] instead", e.toChars(), e.toChars());
                // return new ErrorExp();
            }
            e = e.castTo(sc, e.type.nextOf().pointerTo());
        }
        else
        {
            e = TypeArray.dotExp(sc, e, ident, flag);
        }
        if (!(flag & 1) || e)
            e = e.semantic(sc);
        return e;
    }

    override bool isString()
    {
        TY nty = next.toBasetype().ty;
        return nty == Tchar || nty == Twchar || nty == Tdchar;
    }

    override bool isZeroInit(Loc loc)
    {
        return next.isZeroInit(loc);
    }

    override structalign_t alignment()
    {
        return next.alignment();
    }

    override MATCH constConv(Type to)
    {
        if (to.ty == Tsarray)
        {
            TypeSArray tsa = cast(TypeSArray)to;
            if (!dim.equals(tsa.dim))
                return MATCHnomatch;
        }
        return TypeNext.constConv(to);
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeSArray::implicitConvTo(to = %s) this = %s\n", to.toChars(), toChars());
        if (to.ty == Tarray)
        {
            TypeDArray ta = cast(TypeDArray)to;
            if (!MODimplicitConv(next.mod, ta.next.mod))
                return MATCHnomatch;

            /* Allow conversion to void[]
             */
            if (ta.next.ty == Tvoid)
            {
                return MATCHconvert;
            }

            MATCH m = next.constConv(ta.next);
            if (m > MATCHnomatch)
            {
                return MATCHconvert;
            }
            return MATCHnomatch;
        }
        if (to.ty == Tsarray)
        {
            if (this == to)
                return MATCHexact;

            TypeSArray tsa = cast(TypeSArray)to;
            if (dim.equals(tsa.dim))
            {
                /* Since static arrays are value types, allow
                 * conversions from const elements to non-const
                 * ones, just like we allow conversion from const int
                 * to int.
                 */
                MATCH m = next.implicitConvTo(tsa.next);
                if (m >= MATCHconst)
                {
                    if (mod != to.mod)
                        m = MATCHconst;
                    return m;
                }
            }
        }
        return MATCHnomatch;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeSArray::defaultInit() '%s'\n", toChars());
        }
        if (next.ty == Tvoid)
            return tuns8.defaultInit(loc);
        else
            return next.defaultInit(loc);
    }

    override Expression defaultInitLiteral(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeSArray::defaultInitLiteral() '%s'\n", toChars());
        }
        size_t d = cast(size_t)dim.toInteger();
        Expression elementinit;
        if (next.ty == Tvoid)
            elementinit = tuns8.defaultInitLiteral(loc);
        else
            elementinit = next.defaultInitLiteral(loc);
        auto elements = new Expressions();
        elements.setDim(d);
        for (size_t i = 0; i < d; i++)
            (*elements)[i] = null;
        auto ae = new ArrayLiteralExp(Loc(), elementinit, elements);
        ae.type = this;
        return ae;
    }

    override Expression toExpression()
    {
        Expression e = next.toExpression();
        if (e)
            e = new ArrayExp(dim.loc, e, dim);
        return e;
    }

    override bool hasPointers()
    {
        /* Don't want to do this, because:
         *    struct S { T* array[0]; }
         * may be a variable length struct.
         */
        //if (dim.toInteger() == 0)
        //    return false;

        if (next.ty == Tvoid)
        {
            // Arrays of void contain arbitrary data, which may include pointers
            return true;
        }
        else
            return next.hasPointers();
    }

    override bool needsDestruction()
    {
        return next.needsDestruction();
    }

    /*********************************
     *
     */
    override bool needsNested()
    {
        return next.needsNested();
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 * Dynamic array, no dimension
 */
extern (C++) final class TypeDArray : TypeArray
{
    extern (D) this(Type t)
    {
        super(Tarray, t);
        //printf("TypeDArray(t = %p)\n", t);
    }

    override const(char)* kind() const
    {
        return "darray";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        if (t == next)
            t = this;
        else
        {
            t = new TypeDArray(t);
            t.mod = mod;
        }
        return t;
    }

    override d_uns64 size(Loc loc) const
    {
        //printf("TypeDArray::size()\n");
        return Target.ptrsize * 2;
    }

    override uint alignsize() const
    {
        // A DArray consists of two ptr-sized values, so align it on pointer size
        // boundary
        return Target.ptrsize;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        Type tn = next.semantic(loc, sc);
        Type tbn = tn.toBasetype();
        switch (tbn.ty)
        {
        case Ttuple:
            return tbn;
        case Tfunction:
        case Tnone:
            error(loc, "can't have array of %s", tbn.toChars());
            return Type.terror;
        case Terror:
            return Type.terror;
        default:
            break;
        }
        if (tn.isscope())
        {
            error(loc, "cannot have array of scope %s", tn.toChars());
            return Type.terror;
        }
        next = tn;
        transitive();
        return merge();
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        //printf("TypeDArray::resolve() %s\n", toChars());
        next.resolve(loc, sc, pe, pt, ps, intypeid);
        //printf("s = %p, e = %p, t = %p\n", *ps, *pe, *pt);
        if (*pe)
        {
            // It's really a slice expression
            if (Dsymbol s = getDsymbol(*pe))
                *pe = new DsymbolExp(loc, s);
            *pe = new ArrayExp(loc, *pe);
        }
        else if (*ps)
        {
            if (auto tup = (*ps).isTupleDeclaration())
            {
                // keep *ps
            }
            else
                goto Ldefault;
        }
        else
        {
            if ((*pt).ty != Terror)
                next = *pt; // prevent re-running semantic() on 'next'
        Ldefault:
            Type.resolve(loc, sc, pe, pt, ps, intypeid);
        }
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeDArray::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        if (e.op == TOKtype && (ident == Id.length || ident == Id.ptr))
        {
            e.error("%s is not an expression", e.toChars());
            return new ErrorExp();
        }
        if (ident == Id.length)
        {
            if (e.op == TOKstring)
            {
                StringExp se = cast(StringExp)e;
                return new IntegerExp(se.loc, se.len, Type.tsize_t);
            }
            if (e.op == TOKnull)
                return new IntegerExp(e.loc, 0, Type.tsize_t);
            if (checkNonAssignmentArrayOp(e))
                return new ErrorExp();
            e = new ArrayLengthExp(e.loc, e);
            e.type = Type.tsize_t;
            return e;
        }
        else if (ident == Id.ptr)
        {
            if (!(flag & DotExpFlag.noDeref) && sc.func && !sc.intypeof && sc.func.setUnsafe())
            {
                // MAINTENANCE: turn into error in 2.073
                e.deprecation("%s.ptr cannot be used in @safe code, use &%s[0] instead", e.toChars(), e.toChars());
                // return new ErrorExp();
            }
            e = e.castTo(sc, next.pointerTo());
            return e;
        }
        else
        {
            e = TypeArray.dotExp(sc, e, ident, flag);
        }
        return e;
    }

    override bool isString()
    {
        TY nty = next.toBasetype().ty;
        return nty == Tchar || nty == Twchar || nty == Tdchar;
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override bool isBoolean() const
    {
        return true;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeDArray::implicitConvTo(to = %s) this = %s\n", to.toChars(), toChars());
        if (equals(to))
            return MATCHexact;

        if (to.ty == Tarray)
        {
            TypeDArray ta = cast(TypeDArray)to;

            if (!MODimplicitConv(next.mod, ta.next.mod))
                return MATCHnomatch; // not const-compatible

            /* Allow conversion to void[]
             */
            if (next.ty != Tvoid && ta.next.ty == Tvoid)
            {
                return MATCHconvert;
            }

            MATCH m = next.constConv(ta.next);
            if (m > MATCHnomatch)
            {
                if (m == MATCHexact && mod != to.mod)
                    m = MATCHconst;
                return m;
            }
        }
        return Type.implicitConvTo(to);
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeDArray::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool hasPointers() const
    {
        return true;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeAArray : TypeArray
{
    Type index;     // key type
    Loc loc;
    Scope* sc;

    extern (D) this(Type t, Type index)
    {
        super(Taarray, t);
        this.index = index;
    }

    static TypeAArray create(Type t, Type index)
    {
        return new TypeAArray(t, index);
    }

    override const(char)* kind() const
    {
        return "aarray";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        Type ti = index.syntaxCopy();
        if (t == next && ti == index)
            t = this;
        else
        {
            t = new TypeAArray(t, ti);
            t.mod = mod;
        }
        return t;
    }

    override d_uns64 size(Loc loc)
    {
        return Target.ptrsize;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeAArray::semantic() %s index.ty = %d\n", toChars(), index.ty);
        if (deco)
            return this;

        this.loc = loc;
        this.sc = sc;
        if (sc)
            sc.setNoFree();

        // Deal with the case where we thought the index was a type, but
        // in reality it was an expression.
        if (index.ty == Tident || index.ty == Tinstance || index.ty == Tsarray || index.ty == Ttypeof || index.ty == Treturn)
        {
            Expression e;
            Type t;
            Dsymbol s;
            index.resolve(loc, sc, &e, &t, &s);
            if (e)
            {
                // It was an expression -
                // Rewrite as a static array
                auto tsa = new TypeSArray(next, e);
                return tsa.semantic(loc, sc);
            }
            else if (t)
                index = t.semantic(loc, sc);
            else
            {
                index.error(loc, "index is not a type or an expression");
                return Type.terror;
            }
        }
        else
            index = index.semantic(loc, sc);
        index = index.merge2();

        if (index.nextOf() && !index.nextOf().isImmutable())
        {
            index = index.constOf().mutableOf();
            version (none)
            {
                printf("index is %p %s\n", index, index.toChars());
                index.check();
                printf("index.mod = x%x\n", index.mod);
                printf("index.ito = x%x\n", index.ito);
                if (index.ito)
                {
                    printf("index.ito.mod = x%x\n", index.ito.mod);
                    printf("index.ito.ito = x%x\n", index.ito.ito);
                }
            }
        }

        switch (index.toBasetype().ty)
        {
        case Tfunction:
        case Tvoid:
        case Tnone:
        case Ttuple:
            error(loc, "can't have associative array key of %s", index.toBasetype().toChars());
            goto case Terror;
        case Terror:
            return Type.terror;
        default:
            break;
        }
        Type tbase = index.baseElemOf();
        while (tbase.ty == Tarray)
            tbase = tbase.nextOf().baseElemOf();
        if (tbase.ty == Tstruct)
        {
            /* AA's need typeid(index).equals() and getHash(). Issue error if not correctly set up.
             */
            StructDeclaration sd = (cast(TypeStruct)tbase).sym;
            if (sd.semanticRun < PASSsemanticdone)
                sd.semantic(null);

            // duplicate a part of StructDeclaration::semanticTypeInfoMembers
            //printf("AA = %s, key: xeq = %p, xerreq = %p xhash = %p\n", toChars(), sd.xeq, sd.xerreq, sd.xhash);
            if (sd.xeq && sd.xeq._scope && sd.xeq.semanticRun < PASSsemantic3done)
            {
                uint errors = global.startGagging();
                sd.xeq.semantic3(sd.xeq._scope);
                if (global.endGagging(errors))
                    sd.xeq = sd.xerreq;
            }

            //printf("AA = %s, key: xeq = %p, xhash = %p\n", toChars(), sd.xeq, sd.xhash);
            const(char)* s = (index.toBasetype().ty != Tstruct) ? "bottom of " : "";
            if (!sd.xeq)
            {
                // If sd.xhash != NULL:
                //   sd or its fields have user-defined toHash.
                //   AA assumes that its result is consistent with bitwise equality.
                // else:
                //   bitwise equality & hashing
            }
            else if (sd.xeq == sd.xerreq)
            {
                if (search_function(sd, Id.eq))
                {
                    error(loc, "%sAA key type %s does not have 'bool opEquals(ref const %s) const'", s, sd.toChars(), sd.toChars());
                }
                else
                {
                    error(loc, "%sAA key type %s does not support const equality", s, sd.toChars());
                }
                return Type.terror;
            }
            else if (!sd.xhash)
            {
                if (search_function(sd, Id.eq))
                {
                    error(loc, "%sAA key type %s should have 'size_t toHash() const nothrow @safe' if opEquals defined", s, sd.toChars());
                }
                else
                {
                    error(loc, "%sAA key type %s supports const equality but doesn't support const hashing", s, sd.toChars());
                }
                return Type.terror;
            }
            else
            {
                // defined equality & hashing
                assert(sd.xeq && sd.xhash);

                /* xeq and xhash may be implicitly defined by compiler. For example:
                 *   struct S { int[] arr; }
                 * With 'arr' field equality and hashing, compiler will implicitly
                 * generate functions for xopEquals and xtoHash in TypeInfo_Struct.
                 */
            }
        }
        else if (tbase.ty == Tclass && !(cast(TypeClass)tbase).sym.isInterfaceDeclaration())
        {
            ClassDeclaration cd = (cast(TypeClass)tbase).sym;
            if (cd.semanticRun < PASSsemanticdone)
                cd.semantic(null);

            if (!ClassDeclaration.object)
            {
                error(Loc(), "missing or corrupt object.d");
                fatal();
            }

            static __gshared FuncDeclaration feq = null;
            static __gshared FuncDeclaration fcmp = null;
            static __gshared FuncDeclaration fhash = null;
            if (!feq)
                feq = search_function(ClassDeclaration.object, Id.eq).isFuncDeclaration();
            if (!fcmp)
                fcmp = search_function(ClassDeclaration.object, Id.cmp).isFuncDeclaration();
            if (!fhash)
                fhash = search_function(ClassDeclaration.object, Id.tohash).isFuncDeclaration();
            assert(fcmp && feq && fhash);

            if (feq.vtblIndex < cd.vtbl.dim && cd.vtbl[feq.vtblIndex] == feq)
            {
                version (all)
                {
                    if (fcmp.vtblIndex < cd.vtbl.dim && cd.vtbl[fcmp.vtblIndex] != fcmp)
                    {
                        const(char)* s = (index.toBasetype().ty != Tclass) ? "bottom of " : "";
                        error(loc, "%sAA key type %s now requires equality rather than comparison", s, cd.toChars());
                        errorSupplemental(loc, "Please override Object.opEquals and toHash.");
                    }
                }
            }
        }
        next = next.semantic(loc, sc).merge2();
        transitive();

        switch (next.toBasetype().ty)
        {
        case Tfunction:
        case Tvoid:
        case Tnone:
        case Ttuple:
            error(loc, "can't have associative array of %s", next.toChars());
            goto case Terror;
        case Terror:
            return Type.terror;
        default:
            break;
        }
        if (next.isscope())
        {
            error(loc, "cannot have array of scope %s", next.toChars());
            return Type.terror;
        }
        return merge();
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        //printf("TypeAArray::resolve() %s\n", toChars());
        // Deal with the case where we thought the index was a type, but
        // in reality it was an expression.
        if (index.ty == Tident || index.ty == Tinstance || index.ty == Tsarray)
        {
            Expression e;
            Type t;
            Dsymbol s;
            index.resolve(loc, sc, &e, &t, &s, intypeid);
            if (e)
            {
                // It was an expression -
                // Rewrite as a static array
                auto tsa = new TypeSArray(next, e);
                tsa.mod = this.mod; // just copy mod field so tsa's semantic is not yet done
                return tsa.resolve(loc, sc, pe, pt, ps, intypeid);
            }
            else if (t)
                index = t;
            else
                index.error(loc, "index is not a type or an expression");
        }
        Type.resolve(loc, sc, pe, pt, ps, intypeid);
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeAArray::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        if (ident == Id.length)
        {
            static __gshared FuncDeclaration fd_aaLen = null;
            if (fd_aaLen is null)
            {
                auto fparams = new Parameters();
                fparams.push(new Parameter(STCin, this, null, null));
                fd_aaLen = FuncDeclaration.genCfunc(fparams, Type.tsize_t, Id.aaLen);
                TypeFunction tf = fd_aaLen.type.toTypeFunction();
                tf.purity = PUREconst;
                tf.isnothrow = true;
                tf.isnogc = false;
            }
            Expression ev = new VarExp(e.loc, fd_aaLen, false);
            e = new CallExp(e.loc, ev, e);
            e.type = fd_aaLen.type.toTypeFunction().next;
        }
        else
            e = Type.dotExp(sc, e, ident, flag);
        return e;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeAArray::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override bool isBoolean() const
    {
        return true;
    }

    override Expression toExpression()
    {
        Expression e = next.toExpression();
        if (e)
        {
            Expression ei = index.toExpression();
            if (ei)
                return new ArrayExp(loc, e, ei);
        }
        return null;
    }

    override bool hasPointers() const
    {
        return true;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeAArray::implicitConvTo(to = %s) this = %s\n", to.toChars(), toChars());
        if (equals(to))
            return MATCHexact;

        if (to.ty == Taarray)
        {
            TypeAArray ta = cast(TypeAArray)to;

            if (!MODimplicitConv(next.mod, ta.next.mod))
                return MATCHnomatch; // not const-compatible

            if (!MODimplicitConv(index.mod, ta.index.mod))
                return MATCHnomatch; // not const-compatible

            MATCH m = next.constConv(ta.next);
            MATCH mi = index.constConv(ta.index);
            if (m > MATCHnomatch && mi > MATCHnomatch)
            {
                return MODimplicitConv(mod, to.mod) ? MATCHconst : MATCHnomatch;
            }
        }
        return Type.implicitConvTo(to);
    }

    override MATCH constConv(Type to)
    {
        if (to.ty == Taarray)
        {
            TypeAArray taa = cast(TypeAArray)to;
            MATCH mindex = index.constConv(taa.index);
            MATCH mkey = next.constConv(taa.next);
            // Pick the worst match
            return mkey < mindex ? mkey : mindex;
        }
        return Type.constConv(to);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypePointer : TypeNext
{
    extern (D) this(Type t)
    {
        super(Tpointer, t);
    }

    override const(char)* kind() const
    {
        return "pointer";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        if (t == next)
            t = this;
        else
        {
            t = new TypePointer(t);
            t.mod = mod;
        }
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypePointer::semantic() %s\n", toChars());
        if (deco)
            return this;
        Type n = next.semantic(loc, sc);
        switch (n.toBasetype().ty)
        {
        case Ttuple:
            error(loc, "can't have pointer to %s", n.toChars());
            goto case Terror;
        case Terror:
            return Type.terror;
        default:
            break;
        }
        if (n != next)
        {
            deco = null;
        }
        next = n;
        if (next.ty != Tfunction)
        {
            transitive();
            return merge();
        }
        version (none)
        {
            return merge();
        }
        else
        {
            deco = merge().deco;
            /* Don't return merge(), because arg identifiers and default args
             * can be different
             * even though the types match
             */
            return this;
        }
    }

    override d_uns64 size(Loc loc) const
    {
        return Target.ptrsize;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypePointer::implicitConvTo(to = %s) %s\n", to.toChars(), toChars());
        if (equals(to))
            return MATCHexact;

        if (next.ty == Tfunction)
        {
            if (to.ty == Tpointer)
            {
                TypePointer tp = cast(TypePointer)to;
                if (tp.next.ty == Tfunction)
                {
                    if (next.equals(tp.next))
                        return MATCHconst;

                    if (next.covariant(tp.next) == 1)
                    {
                        Type tret = this.next.nextOf();
                        Type toret = tp.next.nextOf();
                        if (tret.ty == Tclass && toret.ty == Tclass)
                        {
                            /* https://issues.dlang.org/show_bug.cgi?id=10219
                             * Check covariant interface return with offset tweaking.
                             * interface I {}
                             * class C : Object, I {}
                             * I function() dg = function C() {}    // should be error
                             */
                            int offset = 0;
                            if (toret.isBaseOf(tret, &offset) && offset != 0)
                                return MATCHnomatch;
                        }
                        return MATCHconvert;
                    }
                }
                else if (tp.next.ty == Tvoid)
                {
                    // Allow conversions to void*
                    return MATCHconvert;
                }
            }
            return MATCHnomatch;
        }
        else if (to.ty == Tpointer)
        {
            TypePointer tp = cast(TypePointer)to;
            assert(tp.next);

            if (!MODimplicitConv(next.mod, tp.next.mod))
                return MATCHnomatch; // not const-compatible

            /* Alloc conversion to void*
             */
            if (next.ty != Tvoid && tp.next.ty == Tvoid)
            {
                return MATCHconvert;
            }

            MATCH m = next.constConv(tp.next);
            if (m > MATCHnomatch)
            {
                if (m == MATCHexact && mod != to.mod)
                    m = MATCHconst;
                return m;
            }
        }
        return MATCHnomatch;
    }

    override MATCH constConv(Type to)
    {
        if (next.ty == Tfunction)
        {
            if (to.nextOf() && next.equals((cast(TypeNext)to).next))
                return Type.constConv(to);
            else
                return MATCHnomatch;
        }
        return TypeNext.constConv(to);
    }

    override bool isscalar() const
    {
        return true;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypePointer::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override bool hasPointers() const
    {
        return true;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeReference : TypeNext
{
    extern (D) this(Type t)
    {
        super(Treference, t);
        // BUG: what about references to static arrays?
    }

    override const(char)* kind() const
    {
        return "reference";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        if (t == next)
            t = this;
        else
        {
            t = new TypeReference(t);
            t.mod = mod;
        }
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeReference::semantic()\n");
        Type n = next.semantic(loc, sc);
        if (n != next)
            deco = null;
        next = n;
        transitive();
        return merge();
    }

    override d_uns64 size(Loc loc) const
    {
        return Target.ptrsize;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeReference::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        // References just forward things along
        return next.dotExp(sc, e, ident, flag);
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeReference::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

enum RET : int
{
    RETregs         = 1,    // returned in registers
    RETstack        = 2,    // returned on stack
}

alias RETregs = RET.RETregs;
alias RETstack = RET.RETstack;

enum TRUST : int
{
    TRUSTdefault    = 0,
    TRUSTsystem     = 1,    // @system (same as TRUSTdefault)
    TRUSTtrusted    = 2,    // @trusted
    TRUSTsafe       = 3,    // @safe
}

alias TRUSTdefault = TRUST.TRUSTdefault;
alias TRUSTsystem = TRUST.TRUSTsystem;
alias TRUSTtrusted = TRUST.TRUSTtrusted;
alias TRUSTsafe = TRUST.TRUSTsafe;

enum TRUSTformat : int
{
    TRUSTformatDefault,     // do not emit @system when trust == TRUSTdefault
    TRUSTformatSystem,      // emit @system when trust == TRUSTdefault
}

alias TRUSTformatDefault = TRUSTformat.TRUSTformatDefault;
alias TRUSTformatSystem = TRUSTformat.TRUSTformatSystem;

enum PURE : int
{
    PUREimpure      = 0,    // not pure at all
    PUREfwdref      = 1,    // it's pure, but not known which level yet
    PUREweak        = 2,    // no mutable globals are read or written
    PUREconst       = 3,    // parameters are values or const
    PUREstrong      = 4,    // parameters are values or immutable
}

alias PUREimpure = PURE.PUREimpure;
alias PUREfwdref = PURE.PUREfwdref;
alias PUREweak = PURE.PUREweak;
alias PUREconst = PURE.PUREconst;
alias PUREstrong = PURE.PUREstrong;

/***********************************************************
 */
extern (C++) final class TypeFunction : TypeNext
{
    // .next is the return type

    Parameters* parameters;     // function parameters
    int varargs;                // 1: T t, ...) style for variable number of arguments
                                // 2: T t ...) style for variable number of arguments
    bool isnothrow;             // true: nothrow
    bool isnogc;                // true: is @nogc
    bool isproperty;            // can be called without parentheses
    bool isref;                 // true: returns a reference
    bool isreturn;              // true: 'this' is returned by ref
    bool isscope;               // true: 'this' is scope
    bool isscopeinferred;       // true: 'this' is scope from inference
    LINK linkage;               // calling convention
    TRUST trust;                // level of trust
    PURE purity = PUREimpure;
    ubyte iswild;               // bit0: inout on params, bit1: inout on qualifier
    Expressions* fargs;         // function arguments
    int inuse;

    extern (D) this(Parameters* parameters, Type treturn, int varargs, LINK linkage, StorageClass stc = 0)
    {
        super(Tfunction, treturn);
        //if (!treturn) *(char*)0=0;
        //    assert(treturn);
        assert(0 <= varargs && varargs <= 2);
        this.parameters = parameters;
        this.varargs = varargs;
        this.linkage = linkage;

        if (stc & STCpure)
            this.purity = PUREfwdref;
        if (stc & STCnothrow)
            this.isnothrow = true;
        if (stc & STCnogc)
            this.isnogc = true;
        if (stc & STCproperty)
            this.isproperty = true;

        if (stc & STCref)
            this.isref = true;
        if (stc & STCreturn)
            this.isreturn = true;
        if (stc & STCscope)
            this.isscope = true;
        if (stc & STCscopeinferred)
            this.isscopeinferred = true;

        this.trust = TRUSTdefault;
        if (stc & STCsafe)
            this.trust = TRUSTsafe;
        if (stc & STCsystem)
            this.trust = TRUSTsystem;
        if (stc & STCtrusted)
            this.trust = TRUSTtrusted;
    }

    static TypeFunction create(Parameters* parameters, Type treturn, int varargs, LINK linkage, StorageClass stc = 0)
    {
        return new TypeFunction(parameters, treturn, varargs, linkage, stc);
    }

    override const(char)* kind() const
    {
        return "function";
    }

    override Type syntaxCopy()
    {
        Type treturn = next ? next.syntaxCopy() : null;
        Parameters* params = Parameter.arraySyntaxCopy(parameters);
        auto t = new TypeFunction(params, treturn, varargs, linkage);
        t.mod = mod;
        t.isnothrow = isnothrow;
        t.isnogc = isnogc;
        t.purity = purity;
        t.isproperty = isproperty;
        t.isref = isref;
        t.isreturn = isreturn;
        t.isscope = isscope;
        t.isscopeinferred = isscopeinferred;
        t.iswild = iswild;
        t.trust = trust;
        t.fargs = fargs;
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        if (deco) // if semantic() already run
        {
            //printf("already done\n");
            return this;
        }
        //printf("TypeFunction::semantic() this = %p\n", this);
        //printf("TypeFunction::semantic() %s, sc.stc = %llx, fargs = %p\n", toChars(), sc.stc, fargs);

        bool errors = false;

        /* Copy in order to not mess up original.
         * This can produce redundant copies if inferring return type,
         * as semantic() will get called again on this.
         */
        TypeFunction tf = copy().toTypeFunction();
        if (parameters)
        {
            tf.parameters = parameters.copy();
            for (size_t i = 0; i < parameters.dim; i++)
            {
                Parameter p = cast(Parameter)mem.xmalloc(__traits(classInstanceSize, Parameter));
                memcpy(cast(void*)p, cast(void*)(*parameters)[i], __traits(classInstanceSize, Parameter));
                (*tf.parameters)[i] = p;
            }
        }

        if (sc.stc & STCpure)
            tf.purity = PUREfwdref;
        if (sc.stc & STCnothrow)
            tf.isnothrow = true;
        if (sc.stc & STCnogc)
            tf.isnogc = true;
        if (sc.stc & STCref)
            tf.isref = true;
        if (sc.stc & STCreturn)
            tf.isreturn = true;
        if (sc.stc & STCscope)
            tf.isscope = true;
        if (sc.stc & STCscopeinferred)
            tf.isscopeinferred = true;

//        if (tf.isreturn && !tf.isref)
//            tf.isscope = true;                                  // return by itself means 'return scope'

        if (tf.trust == TRUSTdefault)
        {
            if (sc.stc & STCsafe)
                tf.trust = TRUSTsafe;
            else if (sc.stc & STCsystem)
                tf.trust = TRUSTsystem;
            else if (sc.stc & STCtrusted)
                tf.trust = TRUSTtrusted;
        }

        if (sc.stc & STCproperty)
            tf.isproperty = true;

        tf.linkage = sc.linkage;
        version (none)
        {
            /* If the parent is @safe, then this function defaults to safe
             * too.
             * If the parent's @safe-ty is inferred, then this function's @safe-ty needs
             * to be inferred first.
             */
            if (tf.trust == TRUSTdefault)
                for (Dsymbol p = sc.func; p; p = p.toParent2())
                {
                    FuncDeclaration fd = p.isFuncDeclaration();
                    if (fd)
                    {
                        if (fd.isSafeBypassingInference())
                            tf.trust = TRUSTsafe; // default to @safe
                        break;
                    }
                }
        }

        bool wildreturn = false;
        if (tf.next)
        {
            sc = sc.push();
            sc.stc &= ~(STC_TYPECTOR | STC_FUNCATTR);
            tf.next = tf.next.semantic(loc, sc);
            sc = sc.pop();
            errors |= tf.checkRetType(loc);
            if (tf.next.isscope() && !(sc.flags & SCOPEctor))
            {
                error(loc, "functions cannot return scope %s", tf.next.toChars());
                errors = true;
            }
            if (tf.next.hasWild())
                wildreturn = true;

            if (tf.isreturn && !tf.isref && !tf.next.hasPointers())
            {
                error(loc, "function type '%s' has 'return' but does not return any indirections", tf.toChars());
            }
        }

        ubyte wildparams = 0;
        if (tf.parameters)
        {
            /* Create a scope for evaluating the default arguments for the parameters
             */
            Scope* argsc = sc.push();
            argsc.stc = 0; // don't inherit storage class
            argsc.protection = Prot(PROTpublic);
            argsc.func = null;

            size_t dim = Parameter.dim(tf.parameters);
            for (size_t i = 0; i < dim; i++)
            {
                Parameter fparam = Parameter.getNth(tf.parameters, i);
                tf.inuse++;
                fparam.type = fparam.type.semantic(loc, argsc);
                if (tf.inuse == 1)
                    tf.inuse--;
                if (fparam.type.ty == Terror)
                {
                    errors = true;
                    continue;
                }

                fparam.type = fparam.type.addStorageClass(fparam.storageClass);

                if (fparam.storageClass & (STCauto | STCalias | STCstatic))
                {
                    if (!fparam.type)
                        continue;
                }

                Type t = fparam.type.toBasetype();

                if (t.ty == Tfunction)
                {
                    error(loc, "cannot have parameter of function type %s", fparam.type.toChars());
                    errors = true;
                }
                else if (!(fparam.storageClass & (STCref | STCout)) &&
                         (t.ty == Tstruct || t.ty == Tsarray || t.ty == Tenum))
                {
                    Type tb2 = t.baseElemOf();
                    if (tb2.ty == Tstruct && !(cast(TypeStruct)tb2).sym.members ||
                        tb2.ty == Tenum && !(cast(TypeEnum)tb2).sym.memtype)
                    {
                        error(loc, "cannot have parameter of opaque type %s by value", fparam.type.toChars());
                        errors = true;
                    }
                }
                else if (!(fparam.storageClass & STClazy) && t.ty == Tvoid)
                {
                    error(loc, "cannot have parameter of type %s", fparam.type.toChars());
                    errors = true;
                }

                if ((fparam.storageClass & (STCref | STCwild)) == (STCref | STCwild))
                {
                    // 'ref inout' implies 'return'
                    fparam.storageClass |= STCreturn;
                }

                if (fparam.storageClass & STCreturn)
                {
                    if (fparam.storageClass & (STCref | STCout))
                    {
                        // Disabled for the moment awaiting improvement to allow return by ref
                        // to be transformed into return by scope.
                        if (0 && !tf.isref)
                        {
                            auto stc = fparam.storageClass & (STCref | STCout);
                            error(loc, "parameter %s is 'return %s' but function does not return by ref",
                                fparam.ident ? fparam.ident.toChars() : "",
                                stcToChars(stc));
                            errors = true;
                        }
                    }
                    else
                    {
                        fparam.storageClass |= STCscope;        // 'return' implies 'scope'
                        if (tf.isref)
                        {
                        }
                        else if (tf.next && !tf.next.hasPointers())
                        {
                            error(loc, "parameter %s is 'return' but function does not return any indirections",
                                fparam.ident ? fparam.ident.toChars() : "");
                            errors = true;
                        }
                    }
                }

                if (fparam.storageClass & (STCref | STClazy))
                {
                }
                else if (fparam.storageClass & STCout)
                {
                    if (ubyte m = fparam.type.mod & (MODimmutable | MODconst | MODwild))
                    {
                        error(loc, "cannot have %s out parameter of type %s", MODtoChars(m), t.toChars());
                        errors = true;
                    }
                    else
                    {
                        Type tv = t;
                        while (tv.ty == Tsarray)
                            tv = tv.nextOf().toBasetype();
                        if (tv.ty == Tstruct && (cast(TypeStruct)tv).sym.noDefaultCtor)
                        {
                            error(loc, "cannot have out parameter of type %s because the default construction is disabled", fparam.type.toChars());
                            errors = true;
                        }
                    }
                }

                if (fparam.storageClass & STCscope && !fparam.type.hasPointers() && fparam.type.ty != Ttuple)
                {
                    fparam.storageClass &= ~STCscope;
                    if (!(fparam.storageClass & STCref))
                        fparam.storageClass &= ~STCreturn;
                }

                if (t.hasWild())
                {
                    wildparams |= 1;
                    //if (tf.next && !wildreturn)
                    //    error(loc, "inout on parameter means inout must be on return type as well (if from D1 code, replace with 'ref')");
                }

                if (fparam.defaultArg)
                {
                    Expression e = fparam.defaultArg;
                    if (fparam.storageClass & (STCref | STCout))
                    {
                        e = e.semantic(argsc);
                        e = resolveProperties(argsc, e);
                    }
                    else
                    {
                        e = inferType(e, fparam.type);
                        Initializer iz = new ExpInitializer(e.loc, e);
                        iz = iz.semantic(argsc, fparam.type, INITnointerpret);
                        e = iz.toExpression();
                    }
                    if (e.op == TOKfunction) // https://issues.dlang.org/show_bug.cgi?id=4820
                    {
                        FuncExp fe = cast(FuncExp)e;
                        // Replace function literal with a function symbol,
                        // since default arg expression must be copied when used
                        // and copying the literal itself is wrong.
                        e = new VarExp(e.loc, fe.fd, false);
                        e = new AddrExp(e.loc, e);
                        e = e.semantic(argsc);
                    }
                    e = e.implicitCastTo(argsc, fparam.type);

                    // default arg must be an lvalue
                    if (fparam.storageClass & (STCout | STCref))
                        e = e.toLvalue(argsc, e);

                    fparam.defaultArg = e;
                    if (e.op == TOKerror)
                        errors = true;
                }

                /* If fparam after semantic() turns out to be a tuple, the number of parameters may
                 * change.
                 */
                if (t.ty == Ttuple)
                {
                    /* TypeFunction::parameter also is used as the storage of
                     * Parameter objects for FuncDeclaration. So we should copy
                     * the elements of TypeTuple::arguments to avoid unintended
                     * sharing of Parameter object among other functions.
                     */
                    TypeTuple tt = cast(TypeTuple)t;
                    if (tt.arguments && tt.arguments.dim)
                    {
                        /* Propagate additional storage class from tuple parameters to their
                         * element-parameters.
                         * Make a copy, as original may be referenced elsewhere.
                         */
                        size_t tdim = tt.arguments.dim;
                        auto newparams = new Parameters();
                        newparams.setDim(tdim);
                        for (size_t j = 0; j < tdim; j++)
                        {
                            Parameter narg = (*tt.arguments)[j];

                            // https://issues.dlang.org/show_bug.cgi?id=12744
                            // If the storage classes of narg
                            // conflict with the ones in fparam, it's ignored.
                            StorageClass stc  = fparam.storageClass | narg.storageClass;
                            StorageClass stc1 = fparam.storageClass & (STCref | STCout | STClazy);
                            StorageClass stc2 =   narg.storageClass & (STCref | STCout | STClazy);
                            if (stc1 && stc2 && stc1 != stc2)
                            {
                                OutBuffer buf1;  stcToBuffer(&buf1, stc1 | ((stc1 & STCref) ? (fparam.storageClass & STCauto) : 0));
                                OutBuffer buf2;  stcToBuffer(&buf2, stc2);

                                error(loc, "incompatible parameter storage classes '%s' and '%s'",
                                    buf1.peekString(), buf2.peekString());
                                errors = true;
                                stc = stc1 | (stc & ~(STCref | STCout | STClazy));
                            }

                            (*newparams)[j] = new Parameter(
                                stc, narg.type, narg.ident, narg.defaultArg);
                        }
                        fparam.type = new TypeTuple(newparams);
                    }
                    fparam.storageClass = 0;

                    /* Reset number of parameters, and back up one to do this fparam again,
                     * now that it is a tuple
                     */
                    dim = Parameter.dim(tf.parameters);
                    i--;
                    continue;
                }

                /* Resolve "auto ref" storage class to be either ref or value,
                 * based on the argument matching the parameter
                 */
                if (fparam.storageClass & STCauto)
                {
                    if (fargs && i < fargs.dim && (fparam.storageClass & STCref))
                    {
                        Expression farg = (*fargs)[i];
                        if (farg.isLvalue())
                        {
                            // ref parameter
                        }
                        else
                            fparam.storageClass &= ~STCref; // value parameter
                        fparam.storageClass &= ~STCauto;    // https://issues.dlang.org/show_bug.cgi?id=14656
                        fparam.storageClass |= STCautoref;
                    }
                    else
                    {
                        error(loc, "'auto' can only be used as part of 'auto ref' for template function parameters");
                        errors = true;
                    }
                }

                // Remove redundant storage classes for type, they are already applied
                fparam.storageClass &= ~(STC_TYPECTOR | STCin);
            }
            argsc.pop();
        }
        if (tf.isWild())
            wildparams |= 2;

        if (wildreturn && !wildparams)
        {
            error(loc, "inout on return means inout must be on a parameter as well for %s", toChars());
            errors = true;
        }
        tf.iswild = wildparams;

        if (tf.inuse)
        {
            error(loc, "recursive type");
            tf.inuse = 0;
            errors = true;
        }

        if (tf.isproperty && (tf.varargs || Parameter.dim(tf.parameters) > 2))
        {
            error(loc, "properties can only have zero, one, or two parameter");
            errors = true;
        }

        if (tf.varargs == 1 && tf.linkage != LINKd && Parameter.dim(tf.parameters) == 0)
        {
            error(loc, "variadic functions with non-D linkage must have at least one parameter");
            errors = true;
        }

        if (errors)
            return terror;

        if (tf.next)
            tf.deco = tf.merge().deco;

        /* Don't return merge(), because arg identifiers and default args
         * can be different
         * even though the types match
         */
        return tf;
    }

    /********************************************
     * Set 'purity' field of 'this'.
     * Do this lazily, as the parameter types might be forward referenced.
     */
    void purityLevel()
    {
        TypeFunction tf = this;
        if (tf.purity != PUREfwdref)
            return;

        /* Determine purity level based on mutability of t
         * and whether it is a 'ref' type or not.
         */
        static PURE purityOfType(bool isref, Type t)
        {
            if (isref)
            {
                if (t.mod & MODimmutable)
                    return PUREstrong;
                if (t.mod & (MODconst | MODwild))
                    return PUREconst;
                return PUREweak;
            }

            t = t.baseElemOf();

            if (!t.hasPointers() || t.mod & MODimmutable)
                return PUREstrong;

            /* Accept immutable(T)[] and immutable(T)* as being strongly pure
             */
            if (t.ty == Tarray || t.ty == Tpointer)
            {
                Type tn = t.nextOf().toBasetype();
                if (tn.mod & MODimmutable)
                    return PUREstrong;
                if (tn.mod & (MODconst | MODwild))
                    return PUREconst;
            }

            /* The rest of this is too strict; fix later.
             * For example, the only pointer members of a struct may be immutable,
             * which would maintain strong purity.
             * (Just like for dynamic arrays and pointers above.)
             */
            if (t.mod & (MODconst | MODwild))
                return PUREconst;

            /* Should catch delegates and function pointers, and fold in their purity
             */
            return PUREweak;
        }

        purity = PUREstrong; // assume strong until something weakens it

        /* Evaluate what kind of purity based on the modifiers for the parameters
         */
        const dim = Parameter.dim(tf.parameters);
    Lloop: foreach (i; 0 .. dim)
        {
            Parameter fparam = Parameter.getNth(tf.parameters, i);
            Type t = fparam.type;
            if (!t)
                continue;

            if (fparam.storageClass & (STClazy | STCout))
            {
                purity = PUREweak;
                break;
            }
            switch (purityOfType((fparam.storageClass & STCref) != 0, t))
            {
                case PUREweak:
                    purity = PUREweak;
                    break Lloop; // since PUREweak, no need to check further

                case PUREconst:
                    purity = PUREconst;
                    continue;

                case PUREstrong:
                    continue;

                default:
                    assert(0);
            }
        }

        if (purity > PUREweak && tf.nextOf())
        {
            /* Adjust purity based on mutability of return type.
             * https://issues.dlang.org/show_bug.cgi?id=15862
             */
            const purity2 = purityOfType(tf.isref, tf.nextOf());
            if (purity2 < purity)
                purity = purity2;
        }
        tf.purity = purity;
    }

    /********************************************
     * Return true if there are lazy parameters.
     */
    bool hasLazyParameters()
    {
        size_t dim = Parameter.dim(parameters);
        for (size_t i = 0; i < dim; i++)
        {
            Parameter fparam = Parameter.getNth(parameters, i);
            if (fparam.storageClass & STClazy)
                return true;
        }
        return false;
    }

    /***************************
     * Examine function signature for parameter p and see if
     * the value of p can 'escape' the scope of the function.
     * This is useful to minimize the needed annotations for the parameters.
     * Params:
     *  p = parameter to this function
     * Returns:
     *  true if escapes via assignment to global or through a parameter
     */
    bool parameterEscapes(Parameter p)
    {
        /* Scope parameters do not escape.
         * Allow 'lazy' to imply 'scope' -
         * lazy parameters can be passed along
         * as lazy parameters to the next function, but that isn't
         * escaping.
         */
        if (parameterStorageClass(p) & (STCscope | STClazy))
            return false;
        return true;
    }


    /************************************
     * Take the specified storage class for p,
     * and use the function signature to infer whether
     * STCscope and STCreturn should be OR'd in.
     * (This will not affect the name mangling.)
     * Params:
     *  p = one of the parameters to 'this'
     * Returns:
     *  storage class with STCscope or STCreturn OR'd in
     */
    final StorageClass parameterStorageClass(Parameter p)
    {
        //printf("parameterStorageClass(p: %s)\n", p.toChars());
        auto stc = p.storageClass;
        if (!global.params.vsafe)
            return stc;

        if (stc & (STCscope | STCreturn | STClazy) || purity == PUREimpure)
            return stc;

        /* If haven't inferred the return type yet, can't infer storage classes
         */
        if (!nextOf())
            return stc;

        purityLevel();

        // See if p can escape via any of the other parameters
        if (purity == PUREweak)
        {
            const dim = Parameter.dim(parameters);
            foreach (const i; 0 .. dim)
            {
                Parameter fparam = Parameter.getNth(parameters, i);
                if (fparam == p)
                    continue;
                Type t = fparam.type;
                if (!t)
                    continue;
                t = t.baseElemOf();
                if (t.isMutable() && t.hasPointers())
                {
                    if (fparam.storageClass & (STCref | STCout))
                    {
                    }
                    else if (t.ty == Tarray || t.ty == Tpointer)
                    {
                        Type tn = t.nextOf().toBasetype();
                        if (!(tn.isMutable() && tn.hasPointers()))
                            continue;
                    }
                    return stc;
                }
            }
        }

        stc |= STCscope;

        /* Inferring STCreturn here has false positives
         * for pure functions, producing spurious error messages
         * about escaping references.
         * Give up on it for now.
         */
        version (none)
        {
            Type tret = nextOf().toBasetype();
            if (isref || tret.hasPointers())
            {
                /* The result has references, so p could be escaping
                 * that way.
                 */
                stc |= STCreturn;
            }
        }

        return stc;
    }

    override Type addStorageClass(StorageClass stc)
    {
        //printf("addStorageClass(%llx) %d\n", stc, (stc & STCscope) != 0);
        TypeFunction t = Type.addStorageClass(stc).toTypeFunction();
        if ((stc & STCpure && !t.purity) ||
            (stc & STCnothrow && !t.isnothrow) ||
            (stc & STCnogc && !t.isnogc) ||
            (stc & STCscope && !t.isscope) ||
            (stc & STCsafe && t.trust < TRUSTtrusted))
        {
            // Klunky to change these
            auto tf = new TypeFunction(t.parameters, t.next, t.varargs, t.linkage, 0);
            tf.mod = t.mod;
            tf.fargs = fargs;
            tf.purity = t.purity;
            tf.isnothrow = t.isnothrow;
            tf.isnogc = t.isnogc;
            tf.isproperty = t.isproperty;
            tf.isref = t.isref;
            tf.isreturn = t.isreturn;
            tf.isscope = t.isscope;
            tf.isscopeinferred = t.isscopeinferred;
            tf.trust = t.trust;
            tf.iswild = t.iswild;

            if (stc & STCpure)
                tf.purity = PUREfwdref;
            if (stc & STCnothrow)
                tf.isnothrow = true;
            if (stc & STCnogc)
                tf.isnogc = true;
            if (stc & STCsafe)
                tf.trust = TRUSTsafe;
            if (stc & STCscope)
            {
                tf.isscope = true;
                if (stc & STCscopeinferred)
                    tf.isscopeinferred = true;
            }

            tf.deco = tf.merge().deco;
            t = tf;
        }
        return t;
    }

    /** For each active attribute (ref/const/nogc/etc) call fp with a void* for the
     work param and a string representation of the attribute. */
    int attributesApply(void* param, int function(void*, const(char)*) fp, TRUSTformat trustFormat = TRUSTformatDefault)
    {
        int res = 0;
        if (purity)
            res = fp(param, "pure");
        if (res)
            return res;

        if (isnothrow)
            res = fp(param, "nothrow");
        if (res)
            return res;

        if (isnogc)
            res = fp(param, "@nogc");
        if (res)
            return res;

        if (isproperty)
            res = fp(param, "@property");
        if (res)
            return res;

        if (isref)
            res = fp(param, "ref");
        if (res)
            return res;

        if (isreturn)
            res = fp(param, "return");
        if (res)
            return res;

        if (isscope && !isscopeinferred)
            res = fp(param, "scope");
        if (res)
            return res;

        TRUST trustAttrib = trust;

        if (trustAttrib == TRUSTdefault)
        {
            // Print out "@system" when trust equals TRUSTdefault (if desired).
            if (trustFormat == TRUSTformatSystem)
                trustAttrib = TRUSTsystem;
            else
                return res; // avoid calling with an empty string
        }

        return fp(param, trustToChars(trustAttrib));
    }

    override Type substWildTo(uint)
    {
        if (!iswild && !(mod & MODwild))
            return this;

        // Substitude inout qualifier of function type to mutable or immutable
        // would break type system. Instead substitude inout to the most weak
        // qualifer - const.
        uint m = MODconst;

        assert(next);
        Type tret = next.substWildTo(m);
        Parameters* params = parameters;
        if (mod & MODwild)
            params = parameters.copy();
        for (size_t i = 0; i < params.dim; i++)
        {
            Parameter p = (*params)[i];
            Type t = p.type.substWildTo(m);
            if (t == p.type)
                continue;
            if (params == parameters)
                params = parameters.copy();
            (*params)[i] = new Parameter(p.storageClass, t, null, null);
        }
        if (next == tret && params == parameters)
            return this;

        // Similar to TypeFunction::syntaxCopy;
        auto t = new TypeFunction(params, tret, varargs, linkage);
        t.mod = ((mod & MODwild) ? (mod & ~MODwild) | MODconst : mod);
        t.isnothrow = isnothrow;
        t.isnogc = isnogc;
        t.purity = purity;
        t.isproperty = isproperty;
        t.isref = isref;
        t.isreturn = isreturn;
        t.isscope = isscope;
        t.isscopeinferred = isscopeinferred;
        t.iswild = 0;
        t.trust = trust;
        t.fargs = fargs;
        return t.merge();
    }

    /********************************
     * 'args' are being matched to function 'this'
     * Determine match level.
     * Input:
     *      flag    1       performing a partial ordering match
     * Returns:
     *      MATCHxxxx
     */
    MATCH callMatch(Type tthis, Expressions* args, int flag = 0)
    {
        //printf("TypeFunction::callMatch() %s\n", toChars());
        MATCH match = MATCHexact; // assume exact match
        ubyte wildmatch = 0;

        if (tthis)
        {
            Type t = tthis;
            if (t.toBasetype().ty == Tpointer)
                t = t.toBasetype().nextOf(); // change struct* to struct
            if (t.mod != mod)
            {
                if (MODimplicitConv(t.mod, mod))
                    match = MATCHconst;
                else if ((mod & MODwild) && MODimplicitConv(t.mod, (mod & ~MODwild) | MODconst))
                {
                    match = MATCHconst;
                }
                else
                    return MATCHnomatch;
            }
            if (isWild())
            {
                if (t.isWild())
                    wildmatch |= MODwild;
                else if (t.isConst())
                    wildmatch |= MODconst;
                else if (t.isImmutable())
                    wildmatch |= MODimmutable;
                else
                    wildmatch |= MODmutable;
            }
        }

        size_t nparams = Parameter.dim(parameters);
        size_t nargs = args ? args.dim : 0;
        if (nparams == nargs)
        {
        }
        else if (nargs > nparams)
        {
            if (varargs == 0)
                goto Nomatch;
            // too many args; no match
            match = MATCHconvert; // match ... with a "conversion" match level
        }

        for (size_t u = 0; u < nargs; u++)
        {
            if (u >= nparams)
                break;
            Parameter p = Parameter.getNth(parameters, u);
            Expression arg = (*args)[u];
            assert(arg);
            Type tprm = p.type;
            Type targ = arg.type;

            if (!(p.storageClass & STClazy && tprm.ty == Tvoid && targ.ty != Tvoid))
            {
                bool isRef = (p.storageClass & (STCref | STCout)) != 0;
                wildmatch |= targ.deduceWild(tprm, isRef);
            }
        }
        if (wildmatch)
        {
            /* Calculate wild matching modifier
             */
            if (wildmatch & MODconst || wildmatch & (wildmatch - 1))
                wildmatch = MODconst;
            else if (wildmatch & MODimmutable)
                wildmatch = MODimmutable;
            else if (wildmatch & MODwild)
                wildmatch = MODwild;
            else
            {
                assert(wildmatch & MODmutable);
                wildmatch = MODmutable;
            }
        }

        for (size_t u = 0; u < nparams; u++)
        {
            MATCH m;

            Parameter p = Parameter.getNth(parameters, u);
            assert(p);
            if (u >= nargs)
            {
                if (p.defaultArg)
                    continue;
                goto L1;
                // try typesafe variadics
            }
            {
                Expression arg = (*args)[u];
                assert(arg);
                //printf("arg: %s, type: %s\n", arg.toChars(), arg.type.toChars());

                Type targ = arg.type;
                Type tprm = wildmatch ? p.type.substWildTo(wildmatch) : p.type;

                if (p.storageClass & STClazy && tprm.ty == Tvoid && targ.ty != Tvoid)
                    m = MATCHconvert;
                else
                {
                    //printf("%s of type %s implicitConvTo %s\n", arg.toChars(), targ.toChars(), tprm.toChars());
                    if (flag)
                    {
                        // for partial ordering, value is an irrelevant mockup, just look at the type
                        m = targ.implicitConvTo(tprm);
                    }
                    else
                        m = arg.implicitConvTo(tprm);
                    //printf("match %d\n", m);
                }

                // Non-lvalues do not match ref or out parameters
                if (p.storageClass & (STCref | STCout))
                {
                    // https://issues.dlang.org/show_bug.cgi?id=13783
                    // Don't use toBasetype() to handle enum types.
                    Type ta = targ;
                    Type tp = tprm;
                    //printf("fparam[%d] ta = %s, tp = %s\n", u, ta.toChars(), tp.toChars());

                    if (m && !arg.isLvalue())
                    {
                        if (p.storageClass & STCout)
                            goto Nomatch;

                        if (arg.op == TOKstring && tp.ty == Tsarray)
                        {
                            if (ta.ty != Tsarray)
                            {
                                Type tn = tp.nextOf().castMod(ta.nextOf().mod);
                                dinteger_t dim = (cast(StringExp)arg).len;
                                ta = tn.sarrayOf(dim);
                            }
                        }
                        else if (arg.op == TOKslice && tp.ty == Tsarray)
                        {
                            // Allow conversion from T[lwr .. upr] to ref T[upr-lwr]
                            if (ta.ty != Tsarray)
                            {
                                Type tn = ta.nextOf();
                                dinteger_t dim = (cast(TypeSArray)tp).dim.toUInteger();
                                ta = tn.sarrayOf(dim);
                            }
                        }
                        else
                            goto Nomatch;
                    }

                    /* Find most derived alias this type being matched.
                     * https://issues.dlang.org/show_bug.cgi?id=15674
                     * Allow on both ref and out parameters.
                     */
                    while (1)
                    {
                        Type tat = ta.toBasetype().aliasthisOf();
                        if (!tat || !tat.implicitConvTo(tprm))
                            break;
                        ta = tat;
                    }

                    /* A ref variable should work like a head-const reference.
                     * e.g. disallows:
                     *  ref T      <- an lvalue of const(T) argument
                     *  ref T[dim] <- an lvalue of const(T[dim]) argument
                     */
                    if (!ta.constConv(tp))
                        goto Nomatch;
                }
            }

            /* prefer matching the element type rather than the array
             * type when more arguments are present with T[]...
             */
            if (varargs == 2 && u + 1 == nparams && nargs > nparams)
                goto L1;

            //printf("\tm = %d\n", m);
            if (m == MATCHnomatch) // if no match
            {
            L1:
                if (varargs == 2 && u + 1 == nparams) // if last varargs param
                {
                    Type tb = p.type.toBasetype();
                    TypeSArray tsa;
                    dinteger_t sz;

                    switch (tb.ty)
                    {
                    case Tsarray:
                        tsa = cast(TypeSArray)tb;
                        sz = tsa.dim.toInteger();
                        if (sz != nargs - u)
                            goto Nomatch;
                        goto case Tarray;
                    case Tarray:
                        {
                            TypeArray ta = cast(TypeArray)tb;
                            for (; u < nargs; u++)
                            {
                                Expression arg = (*args)[u];
                                assert(arg);

                                /* If lazy array of delegates,
                                 * convert arg(s) to delegate(s)
                                 */
                                Type tret = p.isLazyArray();
                                if (tret)
                                {
                                    if (ta.next.equals(arg.type))
                                        m = MATCHexact;
                                    else if (tret.toBasetype().ty == Tvoid)
                                        m = MATCHconvert;
                                    else
                                    {
                                        m = arg.implicitConvTo(tret);
                                        if (m == MATCHnomatch)
                                            m = arg.implicitConvTo(ta.next);
                                    }
                                }
                                else
                                    m = arg.implicitConvTo(ta.next);

                                if (m == MATCHnomatch)
                                    goto Nomatch;
                                if (m < match)
                                    match = m;
                            }
                            goto Ldone;
                        }
                    case Tclass:
                        // Should see if there's a constructor match?
                        // Or just leave it ambiguous?
                        goto Ldone;

                    default:
                        goto Nomatch;
                    }
                }
                goto Nomatch;
            }
            if (m < match)
                match = m; // pick worst match
        }

    Ldone:
        //printf("match = %d\n", match);
        return match;

    Nomatch:
        //printf("no match\n");
        return MATCHnomatch;
    }

    bool checkRetType(Loc loc)
    {
        Type tb = next.toBasetype();
        if (tb.ty == Tfunction)
        {
            error(loc, "functions cannot return a function");
            next = Type.terror;
        }
        if (tb.ty == Ttuple)
        {
            error(loc, "functions cannot return a tuple");
            next = Type.terror;
        }
        if (!isref && (tb.ty == Tstruct || tb.ty == Tsarray))
        {
            Type tb2 = tb.baseElemOf();
            if (tb2.ty == Tstruct && !(cast(TypeStruct)tb2).sym.members)
            {
                error(loc, "functions cannot return opaque type %s by value", tb.toChars());
                next = Type.terror;
            }
        }
        if (tb.ty == Terror)
            return true;
        return false;
    }

    override Expression defaultInit(Loc loc) const
    {
        error(loc, "function does not have a default initializer");
        return new ErrorExp();
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeDelegate : TypeNext
{
    // .next is a TypeFunction

    extern (D) this(Type t)
    {
        super(Tfunction, t);
        ty = Tdelegate;
    }

    override const(char)* kind() const
    {
        return "delegate";
    }

    override Type syntaxCopy()
    {
        Type t = next.syntaxCopy();
        if (t == next)
            t = this;
        else
        {
            t = new TypeDelegate(t);
            t.mod = mod;
        }
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeDelegate::semantic() %s\n", toChars());
        if (deco) // if semantic() already run
        {
            //printf("already done\n");
            return this;
        }
        next = next.semantic(loc, sc);
        if (next.ty != Tfunction)
            return terror;

        /* In order to deal with https://issues.dlang.org/show_bug.cgi?id=4028
         * perhaps default arguments should
         * be removed from next before the merge.
         */
        version (none)
        {
            return merge();
        }
        else
        {
            /* Don't return merge(), because arg identifiers and default args
             * can be different
             * even though the types match
             */
            deco = merge().deco;
            return this;
        }
    }

    override Type addStorageClass(StorageClass stc)
    {
        TypeDelegate t = cast(TypeDelegate)Type.addStorageClass(stc);
        if (!global.params.vsafe)
            return t;

        /* The rest is meant to add 'scope' to a delegate declaration if it is of the form:
         *  alias dg_t = void* delegate();
         *  scope dg_t dg = ...;
         */
        if(stc & STCscope)
        {
            auto n = t.next.addStorageClass(STCscope | STCscopeinferred);
            if (n != t.next)
            {
                t.next = n;
                t.deco = t.merge().deco; // mangling supposed to not be changed due to STCscopeinferrred
            }
        }
        return t;
    }

    override d_uns64 size(Loc loc) const
    {
        return Target.ptrsize * 2;
    }

    override uint alignsize() const
    {
        return Target.ptrsize;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeDelegate.implicitConvTo(this=%p, to=%p)\n", this, to);
        //printf("from: %s\n", toChars());
        //printf("to  : %s\n", to.toChars());
        if (this == to)
            return MATCHexact;

        version (all)
        {
            // not allowing covariant conversions because it interferes with overriding
            if (to.ty == Tdelegate && this.nextOf().covariant(to.nextOf()) == 1)
            {
                Type tret = this.next.nextOf();
                Type toret = (cast(TypeDelegate)to).next.nextOf();
                if (tret.ty == Tclass && toret.ty == Tclass)
                {
                    /* https://issues.dlang.org/show_bug.cgi?id=10219
                     * Check covariant interface return with offset tweaking.
                     * interface I {}
                     * class C : Object, I {}
                     * I delegate() dg = delegate C() {}    // should be error
                     */
                    int offset = 0;
                    if (toret.isBaseOf(tret, &offset) && offset != 0)
                        return MATCHnomatch;
                }
                return MATCHconvert;
            }
        }

        return MATCHnomatch;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeDelegate::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override bool isBoolean() const
    {
        return true;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeDelegate::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        if (ident == Id.ptr)
        {
            e = new DelegatePtrExp(e.loc, e);
            e = e.semantic(sc);
        }
        else if (ident == Id.funcptr)
        {
            if (!(flag & DotExpFlag.noDeref) && sc.func && !sc.intypeof && sc.func.setUnsafe())
            {
                e.error("%s.funcptr cannot be used in @safe code", e.toChars());
                return new ErrorExp();
            }
            e = new DelegateFuncptrExp(e.loc, e);
            e = e.semantic(sc);
        }
        else
        {
            e = Type.dotExp(sc, e, ident, flag);
        }
        return e;
    }

    override bool hasPointers() const
    {
        return true;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) abstract class TypeQualified : Type
{
    Loc loc;

    // array of Identifier and TypeInstance,
    // representing ident.ident!tiargs.ident. ... etc.
    Objects idents;

    final extern (D) this(TY ty, Loc loc)
    {
        super(ty);
        this.loc = loc;
    }

    final void syntaxCopyHelper(TypeQualified t)
    {
        //printf("TypeQualified::syntaxCopyHelper(%s) %s\n", t.toChars(), toChars());
        idents.setDim(t.idents.dim);
        for (size_t i = 0; i < idents.dim; i++)
        {
            RootObject id = t.idents[i];
            if (id.dyncast() == DYNCAST.dsymbol)
            {
                TemplateInstance ti = cast(TemplateInstance)id;
                ti = cast(TemplateInstance)ti.syntaxCopy(null);
                id = ti;
            }
            else if (id.dyncast() == DYNCAST.expression)
            {
                Expression e = cast(Expression)id;
                e = e.syntaxCopy();
                id = e;
            }
            else if (id.dyncast() == DYNCAST.type)
            {
                Type tx = cast(Type)id;
                tx = tx.syntaxCopy();
                id = tx;
            }
            idents[i] = id;
        }
    }

    final void addIdent(Identifier ident)
    {
        idents.push(ident);
    }

    final void addInst(TemplateInstance inst)
    {
        idents.push(inst);
    }

    final void addIndex(RootObject e)
    {
        idents.push(e);
    }

    override d_uns64 size(Loc loc)
    {
        error(this.loc, "size of type %s is not known", toChars());
        return SIZE_INVALID;
    }

    /*************************************
     * Resolve a tuple index.
     */
    final void resolveTupleIndex(Loc loc, Scope* sc, Dsymbol s, Expression* pe, Type* pt, Dsymbol* ps, RootObject oindex)
    {
        *pt = null;
        *ps = null;
        *pe = null;

        auto tup = s.isTupleDeclaration();

        auto eindex = isExpression(oindex);
        auto tindex = isType(oindex);
        auto sindex = isDsymbol(oindex);

        if (!tup)
        {
            // It's really an index expression
            if (tindex)
                eindex = new TypeExp(loc, tindex);
            else if (sindex)
                eindex = DsymbolExp.resolve(loc, sc, sindex, false);
            Expression e = new IndexExp(loc, DsymbolExp.resolve(loc, sc, s, false), eindex);
            e = e.semantic(sc);
            resolveExp(e, pt, pe, ps);
            return;
        }

        // Convert oindex to Expression, then try to resolve to constant.
        if (tindex)
            tindex.resolve(loc, sc, &eindex, &tindex, &sindex);
        if (sindex)
            eindex = DsymbolExp.resolve(loc, sc, sindex, false);
        if (!eindex)
        {
            .error(loc, "index is %s not an expression", oindex.toChars());
            *pt = Type.terror;
            return;
        }

        eindex = semanticLength(sc, tup, eindex);
        eindex = eindex.ctfeInterpret();
        if (eindex.op == TOKerror)
        {
            *pt = Type.terror;
            return;
        }
        const(uinteger_t) d = eindex.toUInteger();
        if (d >= tup.objects.dim)
        {
            .error(loc, "tuple index %llu exceeds length %u", d, tup.objects.dim);
            *pt = Type.terror;
            return;
        }

        RootObject o = (*tup.objects)[cast(size_t)d];
        *pt = isType(o);
        *ps = isDsymbol(o);
        *pe = isExpression(o);
        if (*pt)
            *pt = (*pt).semantic(loc, sc);
        if (*pe)
            resolveExp(*pe, pt, pe, ps);
    }

    final Expression toExpressionHelper(Expression e, size_t i = 0)
    {
        //printf("toExpressionHelper(e = %s %s)\n", Token.toChars(e.op), e.toChars());
        for (; i < idents.dim; i++)
        {
            RootObject id = idents[i];
            //printf("\t[%d] e: '%s', id: '%s'\n", i, e.toChars(), id.toChars());

            switch (id.dyncast())
            {
                // ... '. ident'
                case DYNCAST.identifier:
                    e = new DotIdExp(e.loc, e, cast(Identifier)id);
                    break;

                // ... '. name!(tiargs)'
                case DYNCAST.dsymbol:
                    auto ti = (cast(Dsymbol)id).isTemplateInstance();
                    assert(ti);
                    e = new DotTemplateInstanceExp(e.loc, e, ti.name, ti.tiargs);
                    break;

                // ... '[type]'
                case DYNCAST.type:          // https://issues.dlang.org/show_bug.cgi?id=1215
                    e = new ArrayExp(loc, e, new TypeExp(loc, cast(Type)id));
                    break;

                // ... '[expr]'
                case DYNCAST.expression:    // https://issues.dlang.org/show_bug.cgi?id=1215
                    e = new ArrayExp(loc, e, cast(Expression)id);
                    break;

                default:
                    assert(0);
            }
        }
        return e;
    }

    /*************************************
     * Takes an array of Identifiers and figures out if
     * it represents a Type or an Expression.
     * Output:
     *      if expression, *pe is set
     *      if type, *pt is set
     */
    final void resolveHelper(Loc loc, Scope* sc, Dsymbol s, Dsymbol scopesym,
        Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        version (none)
        {
            printf("TypeQualified::resolveHelper(sc = %p, idents = '%s')\n", sc, toChars());
            if (scopesym)
                printf("\tscopesym = '%s'\n", scopesym.toChars());
        }
        *pe = null;
        *pt = null;
        *ps = null;
        if (s)
        {
            //printf("\t1: s = '%s' %p, kind = '%s'\n",s.toChars(), s, s.kind());
            Declaration d = s.isDeclaration();
            if (d && (d.storage_class & STCtemplateparameter))
                s = s.toAlias();
            else
                s.checkDeprecated(loc, sc); // check for deprecated aliases
            s = s.toAlias();
            //printf("\t2: s = '%s' %p, kind = '%s'\n",s.toChars(), s, s.kind());
            for (size_t i = 0; i < idents.dim; i++)
            {
                RootObject id = idents[i];
                if (id.dyncast() == DYNCAST.expression ||
                    id.dyncast() == DYNCAST.type)
                {
                    Type tx;
                    Expression ex;
                    Dsymbol sx;
                    resolveTupleIndex(loc, sc, s, &ex, &tx, &sx, id);
                    if (sx)
                    {
                        s = sx.toAlias();
                        continue;
                    }
                    if (tx)
                        ex = new TypeExp(loc, tx);
                    assert(ex);

                    ex = toExpressionHelper(ex, i + 1);
                    ex = ex.semantic(sc);
                    resolveExp(ex, pt, pe, ps);
                    return;
                }

                Type t = s.getType(); // type symbol, type alias, or type tuple?
                uint errorsave = global.errors;
                Dsymbol sm = s.searchX(loc, sc, id);
                if (sm && !(sc.flags & SCOPEignoresymbolvisibility) && !symbolIsVisible(sc, sm))
                {
                    .deprecation(loc, "%s is not visible from module %s", sm.toPrettyChars(), sc._module.toChars());
                    // sm = null;
                }
                if (global.errors != errorsave)
                {
                    *pt = Type.terror;
                    return;
                }
                //printf("\t3: s = %p %s %s, sm = %p\n", s, s.kind(), s.toChars(), sm);
                if (intypeid && !t && sm && sm.needThis())
                    goto L3;
                if (VarDeclaration v = s.isVarDeclaration())
                {
                    if (v.storage_class & (STCconst | STCimmutable | STCmanifest) ||
                        v.type.isConst() || v.type.isImmutable())
                    {
                        // https://issues.dlang.org/show_bug.cgi?id=13087
                        // this.field is not constant always
                        if (!v.isThisDeclaration())
                            goto L3;
                    }
                }
                if (!sm)
                {
                    if (!t)
                    {
                        if (s.isDeclaration()) // var, func, or tuple declaration?
                        {
                            t = s.isDeclaration().type;
                            if (!t && s.isTupleDeclaration()) // expression tuple?
                                goto L3;
                        }
                        else if (s.isTemplateInstance() ||
                                 s.isImport() || s.isPackage() || s.isModule())
                        {
                            goto L3;
                        }
                    }
                    if (t)
                    {
                        sm = t.toDsymbol(sc);
                        if (sm && id.dyncast() == DYNCAST.identifier)
                        {
                            sm = sm.search(loc, cast(Identifier)id);
                            if (sm)
                                goto L2;
                        }
                    L3:
                        Expression e;
                        VarDeclaration v = s.isVarDeclaration();
                        FuncDeclaration f = s.isFuncDeclaration();
                        if (intypeid || !v && !f)
                            e = DsymbolExp.resolve(loc, sc, s, true);
                        else
                            e = new VarExp(loc, s.isDeclaration(), true);

                        e = toExpressionHelper(e, i);
                        e = e.semantic(sc);
                        resolveExp(e, pt, pe, ps);
                        return;
                    }
                    else
                    {
                        if (id.dyncast() == DYNCAST.dsymbol)
                        {
                            // searchX already handles errors for template instances
                            assert(global.errors);
                        }
                        else
                        {
                            assert(id.dyncast() == DYNCAST.identifier);
                            sm = s.search_correct(cast(Identifier)id);
                            if (sm)
                                error(loc, "identifier '%s' of '%s' is not defined, did you mean %s '%s'?", id.toChars(), toChars(), sm.kind(), sm.toChars());
                            else
                                error(loc, "identifier '%s' of '%s' is not defined", id.toChars(), toChars());
                        }
                        *pe = new ErrorExp();
                    }
                    return;
                }
            L2:
                s = sm.toAlias();
            }

            if (auto em = s.isEnumMember())
            {
                // It's not a type, it's an expression
                *pe = em.getVarExp(loc, sc);
                return;
            }
            if (auto v = s.isVarDeclaration())
            {
                /* This is mostly same with DsymbolExp::semantic(), but we cannot use it
                 * because some variables used in type context need to prevent lowering
                 * to a literal or contextful expression. For example:
                 *
                 *  enum a = 1; alias b = a;
                 *  template X(alias e){ alias v = e; }  alias x = X!(1);
                 *  struct S { int v; alias w = v; }
                 *      // TypeIdentifier 'a', 'e', and 'v' should be TOKvar,
                 *      // because getDsymbol() need to work in AliasDeclaration::semantic().
                 */
                if (!v.type ||
                    !v.type.deco && v.inuse)
                {
                    if (v.inuse) // https://issues.dlang.org/show_bug.cgi?id=9494
                        error(loc, "circular reference to %s '%s'", v.kind(), v.toPrettyChars());
                    else
                        error(loc, "forward reference to %s '%s'", v.kind(), v.toPrettyChars());
                    *pt = Type.terror;
                    return;
                }
                if (v.type.ty == Terror)
                    *pt = Type.terror;
                else
                    *pe = new VarExp(loc, v);
                return;
            }
            if (auto fld = s.isFuncLiteralDeclaration())
            {
                //printf("'%s' is a function literal\n", fld.toChars());
                *pe = new FuncExp(loc, fld);
                *pe = (*pe).semantic(sc);
                return;
            }
            version (none)
            {
                if (FuncDeclaration fd = s.isFuncDeclaration())
                {
                    *pe = new DsymbolExp(loc, fd);
                    return;
                }
            }

        L1:
            Type t = s.getType();
            if (!t)
            {
                // If the symbol is an import, try looking inside the import
                if (Import si = s.isImport())
                {
                    s = si.search(loc, s.ident);
                    if (s && s != si)
                        goto L1;
                    s = si;
                }
                *ps = s;
                return;
            }
            if (t.ty == Tinstance && t != this && !t.deco)
            {
                if (!(cast(TypeInstance)t).tempinst.errors)
                    error(loc, "forward reference to '%s'", t.toChars());
                *pt = Type.terror;
                return;
            }

            if (t.ty == Ttuple)
                *pt = t;
            else
                *pt = t.merge();
        }
        if (!s)
        {
            const(char)* p = mutableOf().unSharedOf().toChars();
            const(char)* n = importHint(p);
            if (n)
                error(loc, "'%s' is not defined, perhaps you need to import %s; ?", p, n);
            else
            {
                auto id = new Identifier(p);
                s = sc.search_correct(id);
                if (s)
                    error(loc, "undefined identifier `%s`, did you mean %s `%s`?", p, s.kind(), s.toChars());
                else
                    error(loc, "undefined identifier `%s`", p);
            }
            *pt = Type.terror;
        }
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeIdentifier : TypeQualified
{
    Identifier ident;

    // The symbol representing this identifier, before alias resolution
    Dsymbol originalSymbol;

    extern (D) this(Loc loc, Identifier ident)
    {
        super(Tident, loc);
        this.ident = ident;
    }

    override const(char)* kind() const
    {
        return "identifier";
    }

    override Type syntaxCopy()
    {
        auto t = new TypeIdentifier(loc, ident);
        t.syntaxCopyHelper(this);
        t.mod = mod;
        return t;
    }

    /*************************************
     * Takes an array of Identifiers and figures out if
     * it represents a Type or an Expression.
     * Output:
     *      if expression, *pe is set
     *      if type, *pt is set
     */
    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        //printf("TypeIdentifier::resolve(sc = %p, idents = '%s')\n", sc, toChars());
        if ((ident.equals(Id._super) || ident.equals(Id.This)) && !hasThis(sc))
        {
            AggregateDeclaration ad = sc.getStructClassScope();
            if (ad)
            {
                ClassDeclaration cd = ad.isClassDeclaration();
                if (cd)
                {
                    if (ident.equals(Id.This))
                        ident = cd.ident;
                    else if (cd.baseClass && ident.equals(Id._super))
                        ident = cd.baseClass.ident;
                }
                else
                {
                    StructDeclaration sd = ad.isStructDeclaration();
                    if (sd && ident.equals(Id.This))
                        ident = sd.ident;
                }
            }
        }
        if (ident == Id.ctfe)
        {
            error(loc, "variable __ctfe cannot be read at compile time");
            *pe = null;
            *ps = null;
            *pt = Type.terror;
            return;
        }

        Dsymbol scopesym;
        Dsymbol s = sc.search(loc, ident, &scopesym);
        resolveHelper(loc, sc, s, scopesym, pe, pt, ps, intypeid);
        if (*pt)
            (*pt) = (*pt).addMod(mod);
    }

    /*****************************************
     * See if type resolves to a symbol, if so,
     * return that symbol.
     */
    override Dsymbol toDsymbol(Scope* sc)
    {
        //printf("TypeIdentifier::toDsymbol('%s')\n", toChars());
        if (!sc)
            return null;

        Type t;
        Expression e;
        Dsymbol s;
        resolve(loc, sc, &e, &t, &s);
        if (t && t.ty != Tident)
            s = t.toDsymbol(sc);
        if (e)
            s = getDsymbol(e);

        return s;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        Type t;
        Expression e;
        Dsymbol s;
        //printf("TypeIdentifier::semantic(%s)\n", toChars());
        resolve(loc, sc, &e, &t, &s);
        if (t)
        {
            //printf("\tit's a type %d, %s, %s\n", t.ty, t.toChars(), t.deco);
            t = t.addMod(mod);
        }
        else
        {
            if (s)
            {
                s.error(loc, "is used as a type");
                //assert(0);
            }
            else
                error(loc, "%s is used as a type", toChars());
            t = terror;
        }
        //t.print();
        return t;
    }

    override Expression toExpression()
    {
        return toExpressionHelper(new IdentifierExp(loc, ident));
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 * Similar to TypeIdentifier, but with a TemplateInstance as the root
 */
extern (C++) final class TypeInstance : TypeQualified
{
    TemplateInstance tempinst;

    extern (D) this(Loc loc, TemplateInstance tempinst)
    {
        super(Tinstance, loc);
        this.tempinst = tempinst;
    }

    override const(char)* kind() const
    {
        return "instance";
    }

    override Type syntaxCopy()
    {
        //printf("TypeInstance::syntaxCopy() %s, %d\n", toChars(), idents.dim);
        auto t = new TypeInstance(loc, cast(TemplateInstance)tempinst.syntaxCopy(null));
        t.syntaxCopyHelper(this);
        t.mod = mod;
        return t;
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        // Note close similarity to TypeIdentifier::resolve()
        *pe = null;
        *pt = null;
        *ps = null;

        //printf("TypeInstance::resolve(sc = %p, tempinst = '%s')\n", sc, tempinst.toChars());
        tempinst.semantic(sc);
        if (!global.gag && tempinst.errors)
        {
            *pt = terror;
            return;
        }

        resolveHelper(loc, sc, tempinst, null, pe, pt, ps, intypeid);
        if (*pt)
            *pt = (*pt).addMod(mod);
        //if (*pt) printf("*pt = %d '%s'\n", (*pt).ty, (*pt).toChars());
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        Type t;
        Expression e;
        Dsymbol s;

        //printf("TypeInstance::semantic(%p, %s)\n", this, toChars());
        {
            uint errors = global.errors;
            resolve(loc, sc, &e, &t, &s);
            // if we had an error evaluating the symbol, suppress further errors
            if (!t && errors != global.errors)
                return terror;
        }

        if (!t)
        {
            if (!e && s && s.errors)
            {
                // if there was an error evaluating the symbol, it might actually
                // be a type. Avoid misleading error messages.
                error(loc, "%s had previous errors", toChars());
            }
            else
                error(loc, "%s is used as a type", toChars());
            t = terror;
        }
        return t;
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        Type t;
        Expression e;
        Dsymbol s;
        //printf("TypeInstance::semantic(%s)\n", toChars());
        resolve(loc, sc, &e, &t, &s);
        if (t && t.ty != Tinstance)
            s = t.toDsymbol(sc);
        return s;
    }

    override Expression toExpression()
    {
        return toExpressionHelper(new ScopeExp(loc, tempinst));
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeTypeof : TypeQualified
{
    Expression exp;
    int inuse;

    extern (D) this(Loc loc, Expression exp)
    {
        super(Ttypeof, loc);
        this.exp = exp;
    }

    override const(char)* kind() const
    {
        return "typeof";
    }

    override Type syntaxCopy()
    {
        //printf("TypeTypeof::syntaxCopy() %s\n", toChars());
        auto t = new TypeTypeof(loc, exp.syntaxCopy());
        t.syntaxCopyHelper(this);
        t.mod = mod;
        return t;
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        //printf("TypeTypeof::toDsymbol('%s')\n", toChars());
        Expression e;
        Type t;
        Dsymbol s;
        resolve(loc, sc, &e, &t, &s);
        return s;
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        *pe = null;
        *pt = null;
        *ps = null;

        //printf("TypeTypeof::resolve(this = %p, sc = %p, idents = '%s')\n", this, sc, toChars());
        //static int nest; if (++nest == 50) *(char*)0=0;
        if (inuse)
        {
            inuse = 2;
            error(loc, "circular typeof definition");
        Lerr:
            *pt = Type.terror;
            inuse--;
            return;
        }
        inuse++;

        /* Currently we cannot evaluate 'exp' in speculative context, because
         * the type implementation may leak to the final execution. Consider:
         *
         * struct S(T) {
         *   string toString() const { return "x"; }
         * }
         * void main() {
         *   alias X = typeof(S!int());
         *   assert(typeid(X).xtoString(null) == "x");
         * }
         */
        Scope* sc2 = sc.push();
        sc2.intypeof = 1;
        auto exp2 = exp.semantic(sc2);
        exp2 = resolvePropertiesOnly(sc2, exp2);
        sc2.pop();

        if (exp2.op == TOKerror)
        {
            if (!global.gag)
                exp = exp2;
            goto Lerr;
        }
        exp = exp2;

        if (exp.op == TOKtype ||
            exp.op == TOKscope)
        {
            if (exp.checkType())
                goto Lerr;

            /* Today, 'typeof(func)' returns void if func is a
             * function template (TemplateExp), or
             * template lambda (FuncExp).
             * It's actually used in Phobos as an idiom, to branch code for
             * template functions.
             */
        }
        if (auto f = exp.op == TOKvar    ? (cast(   VarExp)exp).var.isFuncDeclaration()
                   : exp.op == TOKdotvar ? (cast(DotVarExp)exp).var.isFuncDeclaration() : null)
        {
            if (f.checkForwardRef(loc))
                goto Lerr;
        }
        if (auto f = isFuncAddress(exp))
        {
            if (f.checkForwardRef(loc))
                goto Lerr;
        }

        Type t = exp.type;
        if (!t)
        {
            error(loc, "expression (%s) has no type", exp.toChars());
            goto Lerr;
        }
        if (t.ty == Ttypeof)
        {
            error(loc, "forward reference to %s", toChars());
            goto Lerr;
        }
        if (idents.dim == 0)
            *pt = t;
        else
        {
            if (Dsymbol s = t.toDsymbol(sc))
                resolveHelper(loc, sc, s, null, pe, pt, ps, intypeid);
            else
            {
                auto e = toExpressionHelper(new TypeExp(loc, t));
                e = e.semantic(sc);
                resolveExp(e, pt, pe, ps);
            }
        }
        if (*pt)
            (*pt) = (*pt).addMod(mod);
        inuse--;
        return;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeTypeof::semantic() %s\n", toChars());
        Expression e;
        Type t;
        Dsymbol s;
        resolve(loc, sc, &e, &t, &s);
        if (s && (t = s.getType()) !is null)
            t = t.addMod(mod);
        if (!t)
        {
            error(loc, "%s is used as a type", toChars());
            t = Type.terror;
        }
        return t;
    }

    override d_uns64 size(Loc loc)
    {
        if (exp.type)
            return exp.type.size(loc);
        else
            return TypeQualified.size(loc);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeReturn : TypeQualified
{
    extern (D) this(Loc loc)
    {
        super(Treturn, loc);
    }

    override const(char)* kind() const
    {
        return "return";
    }

    override Type syntaxCopy()
    {
        auto t = new TypeReturn(loc);
        t.syntaxCopyHelper(this);
        t.mod = mod;
        return t;
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        Expression e;
        Type t;
        Dsymbol s;
        resolve(loc, sc, &e, &t, &s);
        return s;
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        *pe = null;
        *pt = null;
        *ps = null;

        //printf("TypeReturn::resolve(sc = %p, idents = '%s')\n", sc, toChars());
        Type t;
        {
            FuncDeclaration func = sc.func;
            if (!func)
            {
                error(loc, "typeof(return) must be inside function");
                goto Lerr;
            }
            if (func.fes)
                func = func.fes.func;
            t = func.type.nextOf();
            if (!t)
            {
                error(loc, "cannot use typeof(return) inside function %s with inferred return type", sc.func.toChars());
                goto Lerr;
            }
        }
        if (idents.dim == 0)
            *pt = t;
        else
        {
            if (Dsymbol s = t.toDsymbol(sc))
                resolveHelper(loc, sc, s, null, pe, pt, ps, intypeid);
            else
            {
                auto e = toExpressionHelper(new TypeExp(loc, t));
                e = e.semantic(sc);
                resolveExp(e, pt, pe, ps);
            }
        }
        if (*pt)
            (*pt) = (*pt).addMod(mod);
        return;

    Lerr:
        *pt = Type.terror;
        return;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeReturn::semantic() %s\n", toChars());
        Expression e;
        Type t;
        Dsymbol s;
        resolve(loc, sc, &e, &t, &s);
        if (s && (t = s.getType()) !is null)
            t = t.addMod(mod);
        if (!t)
        {
            error(loc, "%s is used as a type", toChars());
            t = Type.terror;
        }
        return t;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

// Whether alias this dependency is recursive or not.
enum AliasThisRec : int
{
    RECno           = 0,    // no alias this recursion
    RECyes          = 1,    // alias this has recursive dependency
    RECfwdref       = 2,    // not yet known
    RECtypeMask     = 3,    // mask to read no/yes/fwdref
    RECtracing      = 0x4,  // mark in progress of implicitConvTo/deduceWild
    RECtracingDT    = 0x8,  // mark in progress of deduceType
}

alias RECno = AliasThisRec.RECno;
alias RECyes = AliasThisRec.RECyes;
alias RECfwdref = AliasThisRec.RECfwdref;
alias RECtypeMask = AliasThisRec.RECtypeMask;
alias RECtracing = AliasThisRec.RECtracing;
alias RECtracingDT = AliasThisRec.RECtracingDT;

/***********************************************************
 */
extern (C++) final class TypeStruct : Type
{
    StructDeclaration sym;
    AliasThisRec att = RECfwdref;
    CPPMANGLE cppmangle = CPPMANGLE.def;

    extern (D) this(StructDeclaration sym)
    {
        super(Tstruct);
        this.sym = sym;
    }

    override const(char)* kind() const
    {
        return "struct";
    }

    override d_uns64 size(Loc loc)
    {
        return sym.size(loc);
    }

    override uint alignsize()
    {
        sym.size(Loc()); // give error for forward references
        return sym.alignsize;
    }

    override Type syntaxCopy()
    {
        return this;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeStruct::semantic('%s')\n", sym.toChars());
        if (deco)
        {
            if (sc && sc.cppmangle != CPPMANGLE.def)
            {
                if (this.cppmangle == CPPMANGLE.def)
                    this.cppmangle = sc.cppmangle;
                else
                    assert(this.cppmangle == sc.cppmangle);
            }
            return this;
        }

        /* Don't semantic for sym because it should be deferred until
         * sizeof needed or its members accessed.
         */
        // instead, parent should be set correctly
        assert(sym.parent);

        if (sym.type.ty == Terror)
            return Type.terror;
        if (sc)
            this.cppmangle = sc.cppmangle;
        return merge();
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        return sym;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        Dsymbol s;
        static if (LOGDOTEXP)
        {
            printf("TypeStruct::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        assert(e.op != TOKdot);

        // https://issues.dlang.org/show_bug.cgi?id=14010
        if (ident == Id._mangleof)
            return getProperty(e.loc, ident, flag & 1);

        /* If e.tupleof
         */
        if (ident == Id._tupleof)
        {
            /* Create a TupleExp out of the fields of the struct e:
             * (e.field0, e.field1, e.field2, ...)
             */
            e = e.semantic(sc); // do this before turning on noaccesscheck

            sym.size(e.loc); // do semantic of type

            Expression e0;
            Expression ev = e.op == TOKtype ? null : e;
            if (ev)
                ev = extractSideEffect(sc, "__tup", e0, ev);

            auto exps = new Expressions();
            exps.reserve(sym.fields.dim);
            for (size_t i = 0; i < sym.fields.dim; i++)
            {
                VarDeclaration v = sym.fields[i];
                Expression ex;
                if (ev)
                    ex = new DotVarExp(e.loc, ev, v);
                else
                {
                    ex = new VarExp(e.loc, v);
                    ex.type = ex.type.addMod(e.type.mod);
                }
                exps.push(ex);
            }

            e = new TupleExp(e.loc, e0, exps);
            Scope* sc2 = sc.push();
            sc2.flags = sc.flags | SCOPEnoaccesscheck;
            e = e.semantic(sc2);
            sc2.pop();
            return e;
        }

        Dsymbol searchSym()
        {
            int flags = sc.flags & SCOPEignoresymbolvisibility ? IgnoreSymbolVisibility : 0;
            Dsymbol sold = void;
            if (global.params.bug10378 || global.params.check10378)
            {
                sold = sym.search(e.loc, ident, flags);
                if (!global.params.check10378)
                    return sold;
            }

            auto s = sym.search(e.loc, ident, flags | SearchLocalsOnly);
            if (global.params.check10378)
            {
                alias snew = s;
                if (sold !is snew)
                    Scope.deprecation10378(e.loc, sold, snew);
                if (global.params.bug10378)
                    s = sold;
            }
            return s;
        }

        s = searchSym();
    L1:
        if (!s)
        {
            return noMember(sc, e, ident, flag);
        }
        if (!(sc.flags & SCOPEignoresymbolvisibility) && !symbolIsVisible(sc, s))
        {
            .deprecation(e.loc, "%s is not visible from module %s", s.toPrettyChars(), sc._module.toPrettyChars());
            // return noMember(sc, e, ident, flag);
        }
        if (!s.isFuncDeclaration()) // because of overloading
            s.checkDeprecated(e.loc, sc);
        s = s.toAlias();

        if (auto em = s.isEnumMember())
        {
            return em.getVarExp(e.loc, sc);
        }
        if (auto v = s.isVarDeclaration())
        {
            if (!v.type ||
                !v.type.deco && v.inuse)
            {
                if (v.inuse) // https://issues.dlang.org/show_bug.cgi?id=9494
                    e.error("circular reference to %s '%s'", v.kind(), v.toPrettyChars());
                else
                    e.error("forward reference to %s '%s'", v.kind(), v.toPrettyChars());
                return new ErrorExp();
            }
            if (v.type.ty == Terror)
                return new ErrorExp();

            if ((v.storage_class & STCmanifest) && v._init)
            {
                if (v.inuse)
                {
                    e.error("circular initialization of %s '%s'", v.kind(), v.toPrettyChars());
                    return new ErrorExp();
                }
                checkAccess(e.loc, sc, null, v);
                Expression ve = new VarExp(e.loc, v);
                ve = ve.semantic(sc);
                return ve;
            }
        }

        if (auto t = s.getType())
        {
            return (new TypeExp(e.loc, t)).semantic(sc);
        }

        TemplateMixin tm = s.isTemplateMixin();
        if (tm)
        {
            Expression de = new DotExp(e.loc, e, new ScopeExp(e.loc, tm));
            de.type = e.type;
            return de;
        }

        TemplateDeclaration td = s.isTemplateDeclaration();
        if (td)
        {
            if (e.op == TOKtype)
                e = new TemplateExp(e.loc, td);
            else
                e = new DotTemplateExp(e.loc, e, td);
            e = e.semantic(sc);
            return e;
        }

        TemplateInstance ti = s.isTemplateInstance();
        if (ti)
        {
            if (!ti.semanticRun)
            {
                ti.semantic(sc);
                if (!ti.inst || ti.errors) // if template failed to expand
                    return new ErrorExp();
            }
            s = ti.inst.toAlias();
            if (!s.isTemplateInstance())
                goto L1;
            if (e.op == TOKtype)
                e = new ScopeExp(e.loc, ti);
            else
                e = new DotExp(e.loc, e, new ScopeExp(e.loc, ti));
            return e.semantic(sc);
        }

        if (s.isImport() || s.isModule() || s.isPackage())
        {
            e = DsymbolExp.resolve(e.loc, sc, s, false);
            return e;
        }

        OverloadSet o = s.isOverloadSet();
        if (o)
        {
            auto oe = new OverExp(e.loc, o);
            if (e.op == TOKtype)
                return oe;
            return new DotExp(e.loc, e, oe);
        }

        Declaration d = s.isDeclaration();
        if (!d)
        {
            e.error("%s.%s is not a declaration", e.toChars(), ident.toChars());
            return new ErrorExp();
        }

        if (e.op == TOKtype)
        {
            /* It's:
             *    Struct.d
             */
            if (TupleDeclaration tup = d.isTupleDeclaration())
            {
                e = new TupleExp(e.loc, tup);
                e = e.semantic(sc);
                return e;
            }
            if (d.needThis() && sc.intypeof != 1)
            {
                /* Rewrite as:
                 *  this.d
                 */
                if (hasThis(sc))
                {
                    e = new DotVarExp(e.loc, new ThisExp(e.loc), d);
                    e = e.semantic(sc);
                    return e;
                }
            }
            if (d.semanticRun == PASSinit)
                d.semantic(null);
            checkAccess(e.loc, sc, e, d);
            auto ve = new VarExp(e.loc, d);
            if (d.isVarDeclaration() && d.needThis())
                ve.type = d.type.addMod(e.type.mod);
            return ve;
        }

        bool unreal = e.op == TOKvar && (cast(VarExp)e).var.isField();
        if (d.isDataseg() || unreal && d.isField())
        {
            // (e, d)
            checkAccess(e.loc, sc, e, d);
            Expression ve = new VarExp(e.loc, d);
            e = unreal ? ve : new CommaExp(e.loc, e, ve);
            e = e.semantic(sc);
            return e;
        }

        e = new DotVarExp(e.loc, e, d);
        e = e.semantic(sc);
        return e;
    }

    override structalign_t alignment()
    {
        if (sym.alignment == 0)
            sym.size(sym.loc);
        return sym.alignment;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeStruct::defaultInit() '%s'\n", toChars());
        }
        Declaration d = new SymbolDeclaration(sym.loc, sym);
        assert(d);
        d.type = this;
        d.storage_class |= STCrvalue; // https://issues.dlang.org/show_bug.cgi?id=14398
        return new VarExp(sym.loc, d);
    }

    /***************************************
     * Use when we prefer the default initializer to be a literal,
     * rather than a global immutable variable.
     */
    override Expression defaultInitLiteral(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeStruct::defaultInitLiteral() '%s'\n", toChars());
        }
        sym.size(loc);
        if (sym.sizeok != SIZEOKdone)
            return new ErrorExp();

        auto structelems = new Expressions();
        structelems.setDim(sym.fields.dim - sym.isNested());
        uint offset = 0;
        for (size_t j = 0; j < structelems.dim; j++)
        {
            VarDeclaration vd = sym.fields[j];
            Expression e;
            if (vd.inuse)
            {
                error(loc, "circular reference to '%s'", vd.toPrettyChars());
                return new ErrorExp();
            }
            if (vd.offset < offset || vd.type.size() == 0)
                e = null;
            else if (vd._init)
            {
                if (vd._init.isVoidInitializer())
                    e = null;
                else
                    e = vd.getConstInitializer(false);
            }
            else
                e = vd.type.defaultInitLiteral(loc);
            if (e && e.op == TOKerror)
                return e;
            if (e)
                offset = vd.offset + cast(uint)vd.type.size();
            (*structelems)[j] = e;
        }
        auto structinit = new StructLiteralExp(loc, sym, structelems);

        /* Copy from the initializer symbol for larger symbols,
         * otherwise the literals expressed as code get excessively large.
         */
        if (size(loc) > Target.ptrsize * 4 && !needsNested())
            structinit.useStaticInit = true;

        structinit.type = this;
        return structinit;
    }

    override bool isZeroInit(Loc loc) const
    {
        return sym.zeroInit != 0;
    }

    override bool isAssignable()
    {
        bool assignable = true;
        uint offset = ~0; // dead-store initialize to prevent spurious warning

        /* If any of the fields are const or immutable,
         * then one cannot assign this struct.
         */
        for (size_t i = 0; i < sym.fields.dim; i++)
        {
            VarDeclaration v = sym.fields[i];
            //printf("%s [%d] v = (%s) %s, v.offset = %d, v.parent = %s", sym.toChars(), i, v.kind(), v.toChars(), v.offset, v.parent.kind());
            if (i == 0)
            {
            }
            else if (v.offset == offset)
            {
                /* If any fields of anonymous union are assignable,
                 * then regard union as assignable.
                 * This is to support unsafe things like Rebindable templates.
                 */
                if (assignable)
                    continue;
            }
            else
            {
                if (!assignable)
                    return false;
            }
            assignable = v.type.isMutable() && v.type.isAssignable();
            offset = v.offset;
            //printf(" -> assignable = %d\n", assignable);
        }

        return assignable;
    }

    override bool isBoolean() const
    {
        return false;
    }

    override bool needsDestruction() const
    {
        return sym.dtor !is null;
    }

    override bool needsNested()
    {
        if (sym.isNested())
            return true;

        for (size_t i = 0; i < sym.fields.dim; i++)
        {
            VarDeclaration v = sym.fields[i];
            if (!v.isDataseg() && v.type.needsNested())
                return true;
        }
        return false;
    }

    override bool hasPointers()
    {
        // Probably should cache this information in sym rather than recompute
        StructDeclaration s = sym;

        sym.size(Loc()); // give error for forward references
        foreach (VarDeclaration v; s.fields)
        {
            if (v.storage_class & STCref || v.hasPointers())
                return true;
        }
        return false;
    }

    override bool hasVoidInitPointers()
    {
        // Probably should cache this information in sym rather than recompute
        StructDeclaration s = sym;

        sym.size(Loc()); // give error for forward references
        foreach (VarDeclaration v; s.fields)
        {
            if (v._init && v._init.isVoidInitializer() && v.type.hasPointers())
                return true;
            if (!v._init && v.type.hasVoidInitPointers())
                return true;
        }
        return false;
    }

    override MATCH implicitConvTo(Type to)
    {
        MATCH m;

        //printf("TypeStruct::implicitConvTo(%s => %s)\n", toChars(), to.toChars());
        if (ty == to.ty && sym == (cast(TypeStruct)to).sym)
        {
            m = MATCHexact; // exact match
            if (mod != to.mod)
            {
                m = MATCHconst;
                if (MODimplicitConv(mod, to.mod))
                {
                }
                else
                {
                    /* Check all the fields. If they can all be converted,
                     * allow the conversion.
                     */
                    uint offset = ~0; // dead-store to prevent spurious warning
                    for (size_t i = 0; i < sym.fields.dim; i++)
                    {
                        VarDeclaration v = sym.fields[i];
                        if (i == 0)
                        {
                        }
                        else if (v.offset == offset)
                        {
                            if (m > MATCHnomatch)
                                continue;
                        }
                        else
                        {
                            if (m <= MATCHnomatch)
                                return m;
                        }

                        // 'from' type
                        Type tvf = v.type.addMod(mod);

                        // 'to' type
                        Type tv = v.type.addMod(to.mod);

                        // field match
                        MATCH mf = tvf.implicitConvTo(tv);
                        //printf("\t%s => %s, match = %d\n", v.type.toChars(), tv.toChars(), mf);

                        if (mf <= MATCHnomatch)
                            return mf;
                        if (mf < m) // if field match is worse
                            m = mf;
                        offset = v.offset;
                    }
                }
            }
        }
        else if (sym.aliasthis && !(att & RECtracing))
        {
            att = cast(AliasThisRec)(att | RECtracing);
            m = aliasthisOf().implicitConvTo(to);
            att = cast(AliasThisRec)(att & ~RECtracing);
        }
        else
            m = MATCHnomatch; // no match
        return m;
    }

    override MATCH constConv(Type to)
    {
        if (equals(to))
            return MATCHexact;
        if (ty == to.ty && sym == (cast(TypeStruct)to).sym && MODimplicitConv(mod, to.mod))
            return MATCHconst;
        return MATCHnomatch;
    }

    override ubyte deduceWild(Type t, bool isRef)
    {
        if (ty == t.ty && sym == (cast(TypeStruct)t).sym)
            return Type.deduceWild(t, isRef);

        ubyte wm = 0;

        if (t.hasWild() && sym.aliasthis && !(att & RECtracing))
        {
            att = cast(AliasThisRec)(att | RECtracing);
            wm = aliasthisOf().deduceWild(t, isRef);
            att = cast(AliasThisRec)(att & ~RECtracing);
        }

        return wm;
    }

    override Type toHeadMutable()
    {
        return this;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeEnum : Type
{
    EnumDeclaration sym;

    extern (D) this(EnumDeclaration sym)
    {
        super(Tenum);
        this.sym = sym;
    }

    override const(char)* kind() const
    {
        return "enum";
    }

    override Type syntaxCopy()
    {
        return this;
    }

    override d_uns64 size(Loc loc)
    {
        return sym.getMemtype(loc).size(loc);
    }

    override uint alignsize()
    {
        Type t = sym.getMemtype(Loc());
        if (t.ty == Terror)
            return 4;
        return t.alignsize();
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeEnum::semantic() %s\n", toChars());
        if (deco)
            return this;
        return merge();
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        return sym;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        static if (LOGDOTEXP)
        {
            printf("TypeEnum::dotExp(e = '%s', ident = '%s') '%s'\n", e.toChars(), ident.toChars(), toChars());
        }
        // https://issues.dlang.org/show_bug.cgi?id=14010
        if (ident == Id._mangleof)
            return getProperty(e.loc, ident, flag & 1);

        if (sym.semanticRun < PASSsemanticdone)
            sym.semantic(null);
        if (!sym.members)
        {
            if (!(flag & 1))
            {
                sym.error("is forward referenced when looking for '%s'", ident.toChars());
                e = new ErrorExp();
            }
            else
                e = null;
            return e;
        }

        Dsymbol s = sym.search(e.loc, ident);
        if (!s)
        {
            if (ident == Id.max || ident == Id.min || ident == Id._init)
            {
                return getProperty(e.loc, ident, flag & 1);
            }

            Expression res = sym.getMemtype(Loc()).dotExp(sc, e, ident, 1);
            if (!(flag & 1) && !res)
            {
                if (auto ns = sym.search_correct(ident))
                    e.error("no property '%s' for type '%s'. Did you mean '%s.%s' ?", ident.toChars(), toChars(), toChars(),
                        ns.toChars());
                else
                    e.error("no property '%s' for type '%s'", ident.toChars(),
                        toChars());

                return new ErrorExp();
            }
            return res;
        }
        EnumMember m = s.isEnumMember();
        return m.getVarExp(e.loc, sc);
    }

    override Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        Expression e;
        if (ident == Id.max || ident == Id.min)
        {
            return sym.getMaxMinValue(loc, ident);
        }
        else if (ident == Id._init)
        {
            e = defaultInitLiteral(loc);
        }
        else if (ident == Id.stringof)
        {
            const s = toChars();
            e = new StringExp(loc, cast(char*)s);
            Scope sc;
            e = e.semantic(&sc);
        }
        else if (ident == Id._mangleof)
        {
            e = Type.getProperty(loc, ident, flag);
        }
        else
        {
            e = toBasetype().getProperty(loc, ident, flag);
        }
        return e;
    }

    override bool isintegral()
    {
        return sym.getMemtype(Loc()).isintegral();
    }

    override bool isfloating()
    {
        return sym.getMemtype(Loc()).isfloating();
    }

    override bool isreal()
    {
        return sym.getMemtype(Loc()).isreal();
    }

    override bool isimaginary()
    {
        return sym.getMemtype(Loc()).isimaginary();
    }

    override bool iscomplex()
    {
        return sym.getMemtype(Loc()).iscomplex();
    }

    override bool isscalar()
    {
        return sym.getMemtype(Loc()).isscalar();
    }

    override bool isunsigned()
    {
        return sym.getMemtype(Loc()).isunsigned();
    }

    override bool isBoolean()
    {
        return sym.getMemtype(Loc()).isBoolean();
    }

    override bool isString()
    {
        return sym.getMemtype(Loc()).isString();
    }

    override bool isAssignable()
    {
        return sym.getMemtype(Loc()).isAssignable();
    }

    override bool needsDestruction()
    {
        return sym.getMemtype(Loc()).needsDestruction();
    }

    override bool needsNested()
    {
        return sym.getMemtype(Loc()).needsNested();
    }

    override MATCH implicitConvTo(Type to)
    {
        MATCH m;
        //printf("TypeEnum::implicitConvTo()\n");
        if (ty == to.ty && sym == (cast(TypeEnum)to).sym)
            m = (mod == to.mod) ? MATCHexact : MATCHconst;
        else if (sym.getMemtype(Loc()).implicitConvTo(to))
            m = MATCHconvert; // match with conversions
        else
            m = MATCHnomatch; // no match
        return m;
    }

    override MATCH constConv(Type to)
    {
        if (equals(to))
            return MATCHexact;
        if (ty == to.ty && sym == (cast(TypeEnum)to).sym && MODimplicitConv(mod, to.mod))
            return MATCHconst;
        return MATCHnomatch;
    }

    override Type toBasetype()
    {
        if (!sym.members && !sym.memtype)
            return this;
        auto tb = sym.getMemtype(Loc()).toBasetype();
        return tb.castMod(mod);         // retain modifier bits from 'this'
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeEnum::defaultInit() '%s'\n", toChars());
        }
        // Initialize to first member of enum
        Expression e = sym.getDefaultValue(loc);
        e = e.copy();
        e.loc = loc;
        e.type = this; // to deal with const, immutable, etc., variants
        return e;
    }

    override bool isZeroInit(Loc loc)
    {
        return sym.getDefaultValue(loc).isBool(false);
    }

    override bool hasPointers()
    {
        return sym.getMemtype(Loc()).hasPointers();
    }

    override bool hasVoidInitPointers()
    {
        return sym.getMemtype(Loc()).hasVoidInitPointers();
    }

    override Type nextOf()
    {
        return sym.getMemtype(Loc()).nextOf();
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeClass : Type
{
    ClassDeclaration sym;
    AliasThisRec att = RECfwdref;
    CPPMANGLE cppmangle = CPPMANGLE.def;

    extern (D) this(ClassDeclaration sym)
    {
        super(Tclass);
        this.sym = sym;
    }

    override const(char)* kind() const
    {
        return "class";
    }

    override d_uns64 size(Loc loc) const
    {
        return Target.ptrsize;
    }

    override Type syntaxCopy()
    {
        return this;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeClass::semantic(%s)\n", sym.toChars());
        if (deco)
        {
            if (sc && sc.cppmangle != CPPMANGLE.def)
            {
                if (this.cppmangle == CPPMANGLE.def)
                    this.cppmangle = sc.cppmangle;
                else
                    assert(this.cppmangle == sc.cppmangle);
            }
            return this;
        }

        /* Don't semantic for sym because it should be deferred until
         * sizeof needed or its members accessed.
         */
        // instead, parent should be set correctly
        assert(sym.parent);

        if (sym.type.ty == Terror)
            return Type.terror;
        if (sc)
            this.cppmangle = sc.cppmangle;
        return merge();
    }

    override Dsymbol toDsymbol(Scope* sc)
    {
        return sym;
    }

    override Expression dotExp(Scope* sc, Expression e, Identifier ident, int flag)
    {
        Dsymbol s;
        static if (LOGDOTEXP)
        {
            printf("TypeClass::dotExp(e = '%s', ident = '%s')\n", e.toChars(), ident.toChars());
        }
        assert(e.op != TOKdot);

        // https://issues.dlang.org/show_bug.cgi?id=12543
        if (ident == Id.__sizeof || ident == Id.__xalignof || ident == Id._mangleof)
        {
            return Type.getProperty(e.loc, ident, 0);
        }

        /* If e.tupleof
         */
        if (ident == Id._tupleof)
        {
            /* Create a TupleExp
             */
            e = e.semantic(sc); // do this before turning on noaccesscheck

            sym.size(e.loc); // do semantic of type

            Expression e0;
            Expression ev = e.op == TOKtype ? null : e;
            if (ev)
                ev = extractSideEffect(sc, "__tup", e0, ev);

            auto exps = new Expressions();
            exps.reserve(sym.fields.dim);
            for (size_t i = 0; i < sym.fields.dim; i++)
            {
                VarDeclaration v = sym.fields[i];
                // Don't include hidden 'this' pointer
                if (v.isThisDeclaration())
                    continue;
                Expression ex;
                if (ev)
                    ex = new DotVarExp(e.loc, ev, v);
                else
                {
                    ex = new VarExp(e.loc, v);
                    ex.type = ex.type.addMod(e.type.mod);
                }
                exps.push(ex);
            }

            e = new TupleExp(e.loc, e0, exps);
            Scope* sc2 = sc.push();
            sc2.flags = sc.flags | SCOPEnoaccesscheck;
            e = e.semantic(sc2);
            sc2.pop();
            return e;
        }

        Dsymbol searchSym()
        {
            int flags = sc.flags & SCOPEignoresymbolvisibility ? IgnoreSymbolVisibility : 0;
            Dsymbol sold = void;
            if (global.params.bug10378 || global.params.check10378)
            {
                sold = sym.search(e.loc, ident, flags | IgnoreSymbolVisibility);
                if (!global.params.check10378)
                    return sold;
            }

            auto s = sym.search(e.loc, ident, flags | SearchLocalsOnly);
            if (!s && !(flags & IgnoreSymbolVisibility))
            {
                s = sym.search(e.loc, ident, flags | SearchLocalsOnly | IgnoreSymbolVisibility);
                if (s && !(flags & IgnoreErrors))
                    .deprecation(e.loc, "%s is not visible from class %s", s.toPrettyChars(), sym.toChars());
            }
            if (global.params.check10378)
            {
                alias snew = s;
                if (sold !is snew)
                    Scope.deprecation10378(e.loc, sold, snew);
                if (global.params.bug10378)
                    s = sold;
            }
            return s;
        }

        s = searchSym();
    L1:
        if (!s)
        {
            // See if it's 'this' class or a base class
            if (sym.ident == ident)
            {
                if (e.op == TOKtype)
                    return Type.getProperty(e.loc, ident, 0);
                e = new DotTypeExp(e.loc, e, sym);
                e = e.semantic(sc);
                return e;
            }
            if (auto cbase = sym.searchBase(ident))
            {
                if (e.op == TOKtype)
                    return Type.getProperty(e.loc, ident, 0);
                if (auto ifbase = cbase.isInterfaceDeclaration())
                    e = new CastExp(e.loc, e, ifbase.type);
                else
                    e = new DotTypeExp(e.loc, e, cbase);
                e = e.semantic(sc);
                return e;
            }

            if (ident == Id.classinfo)
            {
                assert(Type.typeinfoclass);
                Type t = Type.typeinfoclass.type;
                if (e.op == TOKtype || e.op == TOKdottype)
                {
                    /* For type.classinfo, we know the classinfo
                     * at compile time.
                     */
                    if (!sym.vclassinfo)
                        sym.vclassinfo = new TypeInfoClassDeclaration(sym.type);
                    e = new VarExp(e.loc, sym.vclassinfo);
                    e = e.addressOf();
                    e.type = t; // do this so we don't get redundant dereference
                }
                else
                {
                    /* For class objects, the classinfo reference is the first
                     * entry in the vtbl[]
                     */
                    e = new PtrExp(e.loc, e);
                    e.type = t.pointerTo();
                    if (sym.isInterfaceDeclaration())
                    {
                        if (sym.isCPPinterface())
                        {
                            /* C++ interface vtbl[]s are different in that the
                             * first entry is always pointer to the first virtual
                             * function, not classinfo.
                             * We can't get a .classinfo for it.
                             */
                            error(e.loc, "no .classinfo for C++ interface objects");
                        }
                        /* For an interface, the first entry in the vtbl[]
                         * is actually a pointer to an instance of struct Interface.
                         * The first member of Interface is the .classinfo,
                         * so add an extra pointer indirection.
                         */
                        e.type = e.type.pointerTo();
                        e = new PtrExp(e.loc, e);
                        e.type = t.pointerTo();
                    }
                    e = new PtrExp(e.loc, e, t);
                }
                return e;
            }

            if (ident == Id.__vptr)
            {
                /* The pointer to the vtbl[]
                 * *cast(immutable(void*)**)e
                 */
                e = e.castTo(sc, tvoidptr.immutableOf().pointerTo().pointerTo());
                e = new PtrExp(e.loc, e);
                e = e.semantic(sc);
                return e;
            }

            if (ident == Id.__monitor)
            {
                /* The handle to the monitor (call it a void*)
                 * *(cast(void**)e + 1)
                 */
                e = e.castTo(sc, tvoidptr.pointerTo());
                e = new AddExp(e.loc, e, new IntegerExp(1));
                e = new PtrExp(e.loc, e);
                e = e.semantic(sc);
                return e;
            }

            if (ident == Id.outer && sym.vthis)
            {
                if (sym.vthis.semanticRun == PASSinit)
                    sym.vthis.semantic(null);

                if (auto cdp = sym.toParent2().isClassDeclaration())
                {
                    auto dve = new DotVarExp(e.loc, e, sym.vthis);
                    dve.type = cdp.type.addMod(e.type.mod);
                    return dve;
                }

                /* https://issues.dlang.org/show_bug.cgi?id=15839
                 * Find closest parent class through nested functions.
                 */
                for (auto p = sym.toParent2(); p; p = p.toParent2())
                {
                    auto fd = p.isFuncDeclaration();
                    if (!fd)
                        break;
                    if (fd.isNested())
                        continue;
                    auto ad = fd.isThis();
                    if (!ad)
                        break;
                    if (auto cdp = ad.isClassDeclaration())
                    {
                        auto ve = new ThisExp(e.loc);

                        ve.var = fd.vthis;
                        const nestedError = fd.vthis.checkNestedReference(sc, e.loc);
                        assert(!nestedError);

                        ve.type = fd.vthis.type.addMod(e.type.mod);
                        return ve;
                    }
                    break;
                }

                // Continue to show enclosing function's frame (stack or closure).
                auto dve = new DotVarExp(e.loc, e, sym.vthis);
                dve.type = sym.vthis.type.addMod(e.type.mod);
                return dve;
            }

            return noMember(sc, e, ident, flag & 1);
        }
        if (!(sc.flags & SCOPEignoresymbolvisibility) && !symbolIsVisible(sc, s))
        {
            .deprecation(e.loc, "%s is not visible from module %s", s.toPrettyChars(), sc._module.toPrettyChars());
            // return noMember(sc, e, ident, flag);
        }
        if (!s.isFuncDeclaration()) // because of overloading
            s.checkDeprecated(e.loc, sc);
        s = s.toAlias();

        if (auto em = s.isEnumMember())
        {
            return em.getVarExp(e.loc, sc);
        }
        if (auto v = s.isVarDeclaration())
        {
            if (!v.type ||
                !v.type.deco && v.inuse)
            {
                if (v.inuse) // https://issues.dlang.org/show_bug.cgi?id=9494
                    e.error("circular reference to %s '%s'", v.kind(), v.toPrettyChars());
                else
                    e.error("forward reference to %s '%s'", v.kind(), v.toPrettyChars());
                return new ErrorExp();
            }
            if (v.type.ty == Terror)
                return new ErrorExp();

            if ((v.storage_class & STCmanifest) && v._init)
            {
                if (v.inuse)
                {
                    e.error("circular initialization of %s '%s'", v.kind(), v.toPrettyChars());
                    return new ErrorExp();
                }
                checkAccess(e.loc, sc, null, v);
                Expression ve = new VarExp(e.loc, v);
                ve = ve.semantic(sc);
                return ve;
            }
        }

        if (auto t = s.getType())
        {
            return (new TypeExp(e.loc, t)).semantic(sc);
        }

        TemplateMixin tm = s.isTemplateMixin();
        if (tm)
        {
            Expression de = new DotExp(e.loc, e, new ScopeExp(e.loc, tm));
            de.type = e.type;
            return de;
        }

        TemplateDeclaration td = s.isTemplateDeclaration();
        if (td)
        {
            if (e.op == TOKtype)
                e = new TemplateExp(e.loc, td);
            else
                e = new DotTemplateExp(e.loc, e, td);
            e = e.semantic(sc);
            return e;
        }

        TemplateInstance ti = s.isTemplateInstance();
        if (ti)
        {
            if (!ti.semanticRun)
            {
                ti.semantic(sc);
                if (!ti.inst || ti.errors) // if template failed to expand
                    return new ErrorExp();
            }
            s = ti.inst.toAlias();
            if (!s.isTemplateInstance())
                goto L1;
            if (e.op == TOKtype)
                e = new ScopeExp(e.loc, ti);
            else
                e = new DotExp(e.loc, e, new ScopeExp(e.loc, ti));
            return e.semantic(sc);
        }

        if (s.isImport() || s.isModule() || s.isPackage())
        {
            e = DsymbolExp.resolve(e.loc, sc, s, false);
            return e;
        }

        OverloadSet o = s.isOverloadSet();
        if (o)
        {
            auto oe = new OverExp(e.loc, o);
            if (e.op == TOKtype)
                return oe;
            return new DotExp(e.loc, e, oe);
        }

        Declaration d = s.isDeclaration();
        if (!d)
        {
            e.error("%s.%s is not a declaration", e.toChars(), ident.toChars());
            return new ErrorExp();
        }

        if (e.op == TOKtype)
        {
            /* It's:
             *    Class.d
             */
            if (TupleDeclaration tup = d.isTupleDeclaration())
            {
                e = new TupleExp(e.loc, tup);
                e = e.semantic(sc);
                return e;
            }
            if (d.needThis() && sc.intypeof != 1)
            {
                /* Rewrite as:
                 *  this.d
                 */
                if (hasThis(sc))
                {
                    // This is almost same as getRightThis() in expression.c
                    Expression e1 = new ThisExp(e.loc);
                    e1 = e1.semantic(sc);
                L2:
                    Type t = e1.type.toBasetype();
                    ClassDeclaration cd = e.type.isClassHandle();
                    ClassDeclaration tcd = t.isClassHandle();
                    if (cd && tcd && (tcd == cd || cd.isBaseOf(tcd, null)))
                    {
                        e = new DotTypeExp(e1.loc, e1, cd);
                        e = new DotVarExp(e.loc, e, d);
                        e = e.semantic(sc);
                        return e;
                    }
                    if (tcd && tcd.isNested())
                    {
                        /* e1 is the 'this' pointer for an inner class: tcd.
                         * Rewrite it as the 'this' pointer for the outer class.
                         */
                        e1 = new DotVarExp(e.loc, e1, tcd.vthis);
                        e1.type = tcd.vthis.type;
                        e1.type = e1.type.addMod(t.mod);
                        // Do not call ensureStaticLinkTo()
                        //e1 = e1.semantic(sc);

                        // Skip up over nested functions, and get the enclosing
                        // class type.
                        int n = 0;
                        for (s = tcd.toParent(); s && s.isFuncDeclaration(); s = s.toParent())
                        {
                            FuncDeclaration f = s.isFuncDeclaration();
                            if (f.vthis)
                            {
                                //printf("rewriting e1 to %s's this\n", f.toChars());
                                n++;
                                e1 = new VarExp(e.loc, f.vthis);
                            }
                            else
                            {
                                e = new VarExp(e.loc, d);
                                return e;
                            }
                        }
                        if (s && s.isClassDeclaration())
                        {
                            e1.type = s.isClassDeclaration().type;
                            e1.type = e1.type.addMod(t.mod);
                            if (n > 1)
                                e1 = e1.semantic(sc);
                        }
                        else
                            e1 = e1.semantic(sc);
                        goto L2;
                    }
                }
            }
            //printf("e = %s, d = %s\n", e.toChars(), d.toChars());
            if (d.semanticRun == PASSinit)
                d.semantic(null);
            checkAccess(e.loc, sc, e, d);
            auto ve = new VarExp(e.loc, d);
            if (d.isVarDeclaration() && d.needThis())
                ve.type = d.type.addMod(e.type.mod);
            return ve;
        }

        bool unreal = e.op == TOKvar && (cast(VarExp)e).var.isField();
        if (d.isDataseg() || unreal && d.isField())
        {
            // (e, d)
            checkAccess(e.loc, sc, e, d);
            Expression ve = new VarExp(e.loc, d);
            e = unreal ? ve : new CommaExp(e.loc, e, ve);
            e = e.semantic(sc);
            return e;
        }

        e = new DotVarExp(e.loc, e, d);
        e = e.semantic(sc);
        return e;
    }

    override ClassDeclaration isClassHandle()
    {
        return sym;
    }

    override bool isBaseOf(Type t, int* poffset)
    {
        if (t && t.ty == Tclass)
        {
            ClassDeclaration cd = (cast(TypeClass)t).sym;
            if (sym.isBaseOf(cd, poffset))
                return true;
        }
        return false;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeClass::implicitConvTo(to = '%s') %s\n", to.toChars(), toChars());
        MATCH m = constConv(to);
        if (m > MATCHnomatch)
            return m;

        ClassDeclaration cdto = to.isClassHandle();
        if (cdto)
        {
            //printf("TypeClass::implicitConvTo(to = '%s') %s, isbase = %d %d\n", to.toChars(), toChars(), cdto.isBaseInfoComplete(), sym.isBaseInfoComplete());
            if (cdto.semanticRun < PASSsemanticdone && !cdto.isBaseInfoComplete())
                cdto.semantic(null);
            if (sym.semanticRun < PASSsemanticdone && !sym.isBaseInfoComplete())
                sym.semantic(null);
            if (cdto.isBaseOf(sym, null) && MODimplicitConv(mod, to.mod))
            {
                //printf("'to' is base\n");
                return MATCHconvert;
            }
        }

        m = MATCHnomatch;
        if (sym.aliasthis && !(att & RECtracing))
        {
            att = cast(AliasThisRec)(att | RECtracing);
            m = aliasthisOf().implicitConvTo(to);
            att = cast(AliasThisRec)(att & ~RECtracing);
        }

        return m;
    }

    override MATCH constConv(Type to)
    {
        if (equals(to))
            return MATCHexact;
        if (ty == to.ty && sym == (cast(TypeClass)to).sym && MODimplicitConv(mod, to.mod))
            return MATCHconst;

        /* Conversion derived to const(base)
         */
        int offset = 0;
        if (to.isBaseOf(this, &offset) && offset == 0 && MODimplicitConv(mod, to.mod))
        {
            // Disallow:
            //  derived to base
            //  inout(derived) to inout(base)
            if (!to.isMutable() && !to.isWild())
                return MATCHconvert;
        }

        return MATCHnomatch;
    }

    override ubyte deduceWild(Type t, bool isRef)
    {
        ClassDeclaration cd = t.isClassHandle();
        if (cd && (sym == cd || cd.isBaseOf(sym, null)))
            return Type.deduceWild(t, isRef);

        ubyte wm = 0;

        if (t.hasWild() && sym.aliasthis && !(att & RECtracing))
        {
            att = cast(AliasThisRec)(att | RECtracing);
            wm = aliasthisOf().deduceWild(t, isRef);
            att = cast(AliasThisRec)(att & ~RECtracing);
        }

        return wm;
    }

    override Type toHeadMutable()
    {
        return this;
    }

    override Expression defaultInit(Loc loc)
    {
        static if (LOGDEFAULTINIT)
        {
            printf("TypeClass::defaultInit() '%s'\n", toChars());
        }
        return new NullExp(loc, this);
    }

    override bool isZeroInit(Loc loc) const
    {
        return true;
    }

    override bool isscope() const
    {
        return sym.isscope;
    }

    override bool isBoolean() const
    {
        return true;
    }

    override bool hasPointers() const
    {
        return true;
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeTuple : Type
{
    Parameters* arguments;  // types making up the tuple

    extern (D) this(Parameters* arguments)
    {
        super(Ttuple);
        //printf("TypeTuple(this = %p)\n", this);
        this.arguments = arguments;
        //printf("TypeTuple() %p, %s\n", this, toChars());
        debug
        {
            if (arguments)
            {
                for (size_t i = 0; i < arguments.dim; i++)
                {
                    Parameter arg = (*arguments)[i];
                    assert(arg && arg.type);
                }
            }
        }
    }

    /****************
     * Form TypeTuple from the types of the expressions.
     * Assume exps[] is already tuple expanded.
     */
    extern (D) this(Expressions* exps)
    {
        super(Ttuple);
        auto arguments = new Parameters();
        if (exps)
        {
            arguments.setDim(exps.dim);
            for (size_t i = 0; i < exps.dim; i++)
            {
                Expression e = (*exps)[i];
                if (e.type.ty == Ttuple)
                    e.error("cannot form tuple of tuples");
                auto arg = new Parameter(STCundefined, e.type, null, null);
                (*arguments)[i] = arg;
            }
        }
        this.arguments = arguments;
        //printf("TypeTuple() %p, %s\n", this, toChars());
    }

    static TypeTuple create(Parameters* arguments)
    {
        return new TypeTuple(arguments);
    }

    /*******************************************
     * Type tuple with 0, 1 or 2 types in it.
     */
    extern (D) this()
    {
        super(Ttuple);
        arguments = new Parameters();
    }

    extern (D) this(Type t1)
    {
        super(Ttuple);
        arguments = new Parameters();
        arguments.push(new Parameter(0, t1, null, null));
    }

    extern (D) this(Type t1, Type t2)
    {
        super(Ttuple);
        arguments = new Parameters();
        arguments.push(new Parameter(0, t1, null, null));
        arguments.push(new Parameter(0, t2, null, null));
    }

    override const(char)* kind() const
    {
        return "tuple";
    }

    override Type syntaxCopy()
    {
        Parameters* args = Parameter.arraySyntaxCopy(arguments);
        Type t = new TypeTuple(args);
        t.mod = mod;
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeTuple::semantic(this = %p)\n", this);
        //printf("TypeTuple::semantic() %p, %s\n", this, toChars());
        if (!deco)
            deco = merge().deco;

        /* Don't return merge(), because a tuple with one type has the
         * same deco as that type.
         */
        return this;
    }

    override bool equals(RootObject o)
    {
        Type t = cast(Type)o;
        //printf("TypeTuple::equals(%s, %s)\n", toChars(), t.toChars());
        if (this == t)
            return true;
        if (t.ty == Ttuple)
        {
            TypeTuple tt = cast(TypeTuple)t;
            if (arguments.dim == tt.arguments.dim)
            {
                for (size_t i = 0; i < tt.arguments.dim; i++)
                {
                    Parameter arg1 = (*arguments)[i];
                    Parameter arg2 = (*tt.arguments)[i];
                    if (!arg1.type.equals(arg2.type))
                        return false;
                }
                return true;
            }
        }
        return false;
    }

    override Expression getProperty(Loc loc, Identifier ident, int flag)
    {
        Expression e;
        static if (LOGDOTEXP)
        {
            printf("TypeTuple::getProperty(type = '%s', ident = '%s')\n", toChars(), ident.toChars());
        }
        if (ident == Id.length)
        {
            e = new IntegerExp(loc, arguments.dim, Type.tsize_t);
        }
        else if (ident == Id._init)
        {
            e = defaultInitLiteral(loc);
        }
        else if (flag)
        {
            e = null;
        }
        else
        {
            error(loc, "no property '%s' for tuple '%s'", ident.toChars(), toChars());
            e = new ErrorExp();
        }
        return e;
    }

    override Expression defaultInit(Loc loc)
    {
        auto exps = new Expressions();
        exps.setDim(arguments.dim);
        for (size_t i = 0; i < arguments.dim; i++)
        {
            Parameter p = (*arguments)[i];
            assert(p.type);
            Expression e = p.type.defaultInitLiteral(loc);
            if (e.op == TOKerror)
                return e;
            (*exps)[i] = e;
        }
        return new TupleExp(loc, exps);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 * This is so we can slice a TypeTuple
 */
extern (C++) final class TypeSlice : TypeNext
{
    Expression lwr;
    Expression upr;

    extern (D) this(Type next, Expression lwr, Expression upr)
    {
        super(Tslice, next);
        //printf("TypeSlice[%s .. %s]\n", lwr.toChars(), upr.toChars());
        this.lwr = lwr;
        this.upr = upr;
    }

    override const(char)* kind() const
    {
        return "slice";
    }

    override Type syntaxCopy()
    {
        Type t = new TypeSlice(next.syntaxCopy(), lwr.syntaxCopy(), upr.syntaxCopy());
        t.mod = mod;
        return t;
    }

    override Type semantic(Loc loc, Scope* sc)
    {
        //printf("TypeSlice::semantic() %s\n", toChars());
        Type tn = next.semantic(loc, sc);
        //printf("next: %s\n", tn.toChars());

        Type tbn = tn.toBasetype();
        if (tbn.ty != Ttuple)
        {
            error(loc, "can only slice tuple types, not %s", tbn.toChars());
            return Type.terror;
        }
        TypeTuple tt = cast(TypeTuple)tbn;

        lwr = semanticLength(sc, tbn, lwr);
        upr = semanticLength(sc, tbn, upr);
        lwr = lwr.ctfeInterpret();
        upr = upr.ctfeInterpret();
        if (lwr.op == TOKerror || upr.op == TOKerror)
            return Type.terror;

        uinteger_t i1 = lwr.toUInteger();
        uinteger_t i2 = upr.toUInteger();
        if (!(i1 <= i2 && i2 <= tt.arguments.dim))
        {
            error(loc, "slice [%llu..%llu] is out of range of [0..%u]", i1, i2, tt.arguments.dim);
            return Type.terror;
        }

        next = tn;
        transitive();

        auto args = new Parameters();
        args.reserve(cast(size_t)(i2 - i1));
        for (size_t i = cast(size_t)i1; i < cast(size_t)i2; i++)
        {
            Parameter arg = (*tt.arguments)[i];
            args.push(arg);
        }
        Type t = new TypeTuple(args);
        return t.semantic(loc, sc);
    }

    override void resolve(Loc loc, Scope* sc, Expression* pe, Type* pt, Dsymbol* ps, bool intypeid = false)
    {
        next.resolve(loc, sc, pe, pt, ps, intypeid);
        if (*pe)
        {
            // It's really a slice expression
            if (Dsymbol s = getDsymbol(*pe))
                *pe = new DsymbolExp(loc, s);
            *pe = new ArrayExp(loc, *pe, new IntervalExp(loc, lwr, upr));
        }
        else if (*ps)
        {
            Dsymbol s = *ps;
            TupleDeclaration td = s.isTupleDeclaration();
            if (td)
            {
                /* It's a slice of a TupleDeclaration
                 */
                ScopeDsymbol sym = new ArrayScopeSymbol(sc, td);
                sym.parent = sc.scopesym;
                sc = sc.push(sym);
                sc = sc.startCTFE();
                lwr = lwr.semantic(sc);
                upr = upr.semantic(sc);
                sc = sc.endCTFE();
                sc = sc.pop();

                lwr = lwr.ctfeInterpret();
                upr = upr.ctfeInterpret();
                uinteger_t i1 = lwr.toUInteger();
                uinteger_t i2 = upr.toUInteger();
                if (!(i1 <= i2 && i2 <= td.objects.dim))
                {
                    error(loc, "slice [%llu..%llu] is out of range of [0..%u]", i1, i2, td.objects.dim);
                    *ps = null;
                    *pt = Type.terror;
                    return;
                }

                if (i1 == 0 && i2 == td.objects.dim)
                {
                    *ps = td;
                    return;
                }

                /* Create a new TupleDeclaration which
                 * is a slice [i1..i2] out of the old one.
                 */
                auto objects = new Objects();
                objects.setDim(cast(size_t)(i2 - i1));
                for (size_t i = 0; i < objects.dim; i++)
                {
                    (*objects)[i] = (*td.objects)[cast(size_t)i1 + i];
                }

                auto tds = new TupleDeclaration(loc, td.ident, objects);
                *ps = tds;
            }
            else
                goto Ldefault;
        }
        else
        {
            if ((*pt).ty != Terror)
                next = *pt; // prevent re-running semantic() on 'next'
        Ldefault:
            Type.resolve(loc, sc, pe, pt, ps, intypeid);
        }
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class TypeNull : Type
{
    extern (D) this()
    {
        //printf("TypeNull %p\n", this);
        super(Tnull);
    }

    override const(char)* kind() const
    {
        return "null";
    }

    override Type syntaxCopy()
    {
        // No semantic analysis done, no need to copy
        return this;
    }

    override MATCH implicitConvTo(Type to)
    {
        //printf("TypeNull::implicitConvTo(this=%p, to=%p)\n", this, to);
        //printf("from: %s\n", toChars());
        //printf("to  : %s\n", to.toChars());
        MATCH m = Type.implicitConvTo(to);
        if (m != MATCHnomatch)
            return m;

        // NULL implicitly converts to any pointer type or dynamic array
        //if (type.ty == Tpointer && type.nextOf().ty == Tvoid)
        {
            Type tb = to.toBasetype();
            if (tb.ty == Tnull || tb.ty == Tpointer || tb.ty == Tarray || tb.ty == Taarray || tb.ty == Tclass || tb.ty == Tdelegate)
                return MATCHconst;
        }

        return MATCHnomatch;
    }

    override bool isBoolean() const
    {
        return true;
    }

    override d_uns64 size(Loc loc) const
    {
        return tvoidptr.size(loc);
    }

    override Expression defaultInit(Loc loc) const
    {
        return new NullExp(Loc(), Type.tnull);
    }

    override void accept(Visitor v)
    {
        v.visit(this);
    }
}

/***********************************************************
 */
extern (C++) final class Parameter : RootObject
{
    StorageClass storageClass;
    Type type;
    Identifier ident;
    Expression defaultArg;

    extern (D) this(StorageClass storageClass, Type type, Identifier ident, Expression defaultArg)
    {
        this.type = type;
        this.ident = ident;
        this.storageClass = storageClass;
        this.defaultArg = defaultArg;
    }

    static Parameter create(StorageClass storageClass, Type type, Identifier ident, Expression defaultArg)
    {
        return new Parameter(storageClass, type, ident, defaultArg);
    }

    Parameter syntaxCopy()
    {
        return new Parameter(storageClass, type ? type.syntaxCopy() : null, ident, defaultArg ? defaultArg.syntaxCopy() : null);
    }

    /****************************************************
     * Determine if parameter is a lazy array of delegates.
     * If so, return the return type of those delegates.
     * If not, return NULL.
     *
     * Returns T if the type is one of the following forms:
     *      T delegate()[]
     *      T delegate()[dim]
     */
    Type isLazyArray()
    {
        Type tb = type.toBasetype();
        if (tb.ty == Tsarray || tb.ty == Tarray)
        {
            Type tel = (cast(TypeArray)tb).next.toBasetype();
            if (tel.ty == Tdelegate)
            {
                TypeDelegate td = cast(TypeDelegate)tel;
                TypeFunction tf = td.next.toTypeFunction();
                if (!tf.varargs && Parameter.dim(tf.parameters) == 0)
                {
                    return tf.next; // return type of delegate
                }
            }
        }
        return null;
    }

    // kludge for template.isType()
    override DYNCAST dyncast() const
    {
        return DYNCAST.parameter;
    }

    void accept(Visitor v)
    {
        v.visit(this);
    }

    static Parameters* arraySyntaxCopy(Parameters* parameters)
    {
        Parameters* params = null;
        if (parameters)
        {
            params = new Parameters();
            params.setDim(parameters.dim);
            for (size_t i = 0; i < params.dim; i++)
                (*params)[i] = (*parameters)[i].syntaxCopy();
        }
        return params;
    }

    /****************************************
     * Determine if parameter list is really a template parameter list
     * (i.e. it has auto or alias parameters)
     */
    extern (D) static int isTPL(Parameters* parameters)
    {
        //printf("Parameter::isTPL()\n");

        int isTPLDg(size_t n, Parameter p)
        {
            if (p.storageClass & (STCalias | STCauto | STCstatic))
                return 1;
            return 0;
        }

        return _foreach(parameters, &isTPLDg);
    }

    /***************************************
     * Determine number of arguments, folding in tuples.
     */
    static size_t dim(Parameters* parameters)
    {
        size_t nargs = 0;

        int dimDg(size_t n, Parameter p)
        {
            ++nargs;
            return 0;
        }

        _foreach(parameters, &dimDg);
        return nargs;
    }

    /***************************************
     * Get nth Parameter, folding in tuples.
     * Returns:
     *      Parameter*      nth Parameter
     *      NULL            not found, *pn gets incremented by the number
     *                      of Parameters
     */
    static Parameter getNth(Parameters* parameters, size_t nth, size_t* pn = null)
    {
        Parameter param;

        int getNthParamDg(size_t n, Parameter p)
        {
            if (n == nth)
            {
                param = p;
                return 1;
            }
            return 0;
        }

        int res = _foreach(parameters, &getNthParamDg);
        return res ? param : null;
    }

    alias ForeachDg = extern (D) int delegate(size_t paramidx, Parameter param);

    /***************************************
     * Expands tuples in args in depth first order. Calls
     * dg(void *ctx, size_t argidx, Parameter *arg) for each Parameter.
     * If dg returns !=0, stops and returns that value else returns 0.
     * Use this function to avoid the O(N + N^2/2) complexity of
     * calculating dim and calling N times getNth.
     */
    extern (D) static int _foreach(Parameters* parameters, scope ForeachDg dg, size_t* pn = null)
    {
        assert(dg);
        if (!parameters)
            return 0;

        size_t n = pn ? *pn : 0; // take over index
        int result = 0;
        foreach (i; 0 .. parameters.dim)
        {
            Parameter p = (*parameters)[i];
            Type t = p.type.toBasetype();

            if (t.ty == Ttuple)
            {
                TypeTuple tu = cast(TypeTuple)t;
                result = _foreach(tu.arguments, dg, &n);
            }
            else
                result = dg(n++, p);

            if (result)
                break;
        }

        if (pn)
            *pn = n; // update index
        return result;
    }

    override const(char)* toChars() const
    {
        return ident ? ident.toChars() : "__anonymous_param";
    }

    /*********************************
     * Compute covariance of parameters `this` and `p`
     * as determined by the storage classes of both.
     * Params:
     *  p = Parameter to compare with
     * Returns:
     *  true = `this` can be used in place of `p`
     *  false = nope
     */
    final bool isCovariant(bool returnByRef, const Parameter p) const pure nothrow @nogc @safe
    {
        enum stc = STCref | STCin | STCout | STClazy;
        if ((this.storageClass & stc) != (p.storageClass & stc))
            return false;
        return isCovariantScope(returnByRef, this.storageClass, p.storageClass);
    }

    static bool isCovariantScope(bool returnByRef, StorageClass from, StorageClass to) pure nothrow @nogc @safe
    {
        if (from == to)
            return true;

        /* Shrinking the representation is necessary because StorageClass is so wide
         * Params:
         *   returnByRef = true if the function returns by ref
         *   stc = storage class of parameter
         */
        static uint buildSR(bool returnByRef, StorageClass stc) pure nothrow @nogc @safe
        {
            uint result;
            final switch (stc & (STCref | STCscope | STCreturn))
            {
                case 0:                    result = SR.None;        break;
                case STCref:               result = SR.Ref;         break;
                case STCscope:             result = SR.Scope;       break;
                case STCreturn | STCref:   result = SR.ReturnRef;   break;
                case STCreturn | STCscope: result = SR.ReturnScope; break;
                case STCref    | STCscope: result = SR.RefScope;    break;
                case STCreturn | STCref | STCscope:
                    result = returnByRef ? SR.ReturnRef_Scope : SR.Ref_ReturnScope;
                    break;
            }
            return result;
        }

        /* result is true if the 'from' can be used as a 'to'
         */

        if ((from ^ to) & STCref)               // differing in 'ref' means no covariance
            return false;

        return covariant[buildSR(returnByRef, from)][buildSR(returnByRef, to)];
    }

    /* Classification of 'scope-return-ref' possibilities
     */
    enum SR
    {
        None,
        Scope,
        ReturnScope,
        Ref,
        ReturnRef,
        RefScope,
        ReturnRef_Scope,
        Ref_ReturnScope,
    }

    static bool[SR.max + 1][SR.max + 1] covariantInit() pure nothrow @nogc @safe
    {
        /* Initialize covariant[][] with this:

             From\To           n   rs  s
             None              X
             ReturnScope       X   X
             Scope             X   X   X

             From\To           r   rr  rs  rr-s r-rs
             Ref               X   X
             ReturnRef             X
             RefScope          X   X   X   X    X
             ReturnRef-Scope       X       X
             Ref-ReturnScope   X   X            X
        */
        bool[SR.max + 1][SR.max + 1] covariant;

        foreach (i; 0 .. SR.max + 1)
        {
            covariant[i][i] = true;
            covariant[SR.RefScope][i] = true;
        }
        covariant[SR.ReturnScope][SR.None]        = true;
        covariant[SR.Scope      ][SR.None]        = true;
        covariant[SR.Scope      ][SR.ReturnScope] = true;

        covariant[SR.Ref            ][SR.ReturnRef] = true;
        covariant[SR.ReturnRef_Scope][SR.ReturnRef] = true;
        covariant[SR.Ref_ReturnScope][SR.Ref      ] = true;
        covariant[SR.Ref_ReturnScope][SR.ReturnRef] = true;

        return covariant;
    }

    extern (D) static immutable bool[SR.max + 1][SR.max + 1] covariant = covariantInit();
}
