// Compiler implementation of the D programming language
// Copyright (c) 1999-2015 by Digital Mars
// All Rights Reserved
// written by Walter Bright
// http://www.digitalmars.com
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt

module ddmd.delegatize;

import ddmd.apply;
import ddmd.declaration;
import ddmd.dscope;
import ddmd.expression;
import ddmd.func;
import ddmd.globals;
import ddmd.mtype;
import ddmd.statement;
import ddmd.tokens;
import ddmd.visitor;

extern (C++) Expression toDelegate(Expression e, Type t, Scope* sc)
{
    //printf("Expression::toDelegate(t = %s) %s\n", t->toChars(), e->toChars());
    Loc loc = e.loc;
    auto tf = new TypeFunction(null, t, 0, LINKd);
    if (t.hasWild())
        tf.mod = MODwild;
    auto fld = new FuncLiteralDeclaration(loc, loc, tf, TOKdelegate, null);
    sc = sc.push();
    sc.parent = fld; // set current function to be the delegate
    lambdaSetParent(e, sc);
    bool r = lambdaCheckForNestedRef(e, sc);
    sc = sc.pop();
    if (r)
        return new ErrorExp();
    Statement s;
    if (t.ty == Tvoid)
        s = new ExpStatement(loc, e);
    else
        s = new ReturnStatement(loc, e);
    fld.fbody = s;
    e = new FuncExp(loc, fld);
    e = e.semantic(sc);
    return e;
}

/******************************************
 * Patch the parent of declarations to be the new function literal.
 */
extern (C++) void lambdaSetParent(Expression e, Scope* sc)
{
    extern (C++) final class LambdaSetParent : StoppableVisitor
    {
        alias visit = super.visit;
        Scope* sc;

    public:
        extern (D) this(Scope* sc)
        {
            this.sc = sc;
        }

        override void visit(Expression)
        {
        }

        override void visit(DeclarationExp e)
        {
            e.declaration.parent = sc.parent;
        }

        override void visit(IndexExp e)
        {
            if (e.lengthVar)
            {
                //printf("lengthVar\n");
                e.lengthVar.parent = sc.parent;
            }
        }

        override void visit(SliceExp e)
        {
            if (e.lengthVar)
            {
                //printf("lengthVar\n");
                e.lengthVar.parent = sc.parent;
            }
        }
    }

    scope LambdaSetParent lsp = new LambdaSetParent(sc);
    walkPostorder(e, lsp);
}

/*******************************************
 * Look for references to variables in a scope enclosing the new function literal.
 * Returns true if error occurs.
 */
extern (C++) bool lambdaCheckForNestedRef(Expression e, Scope* sc)
{
    extern (C++) final class LambdaCheckForNestedRef : StoppableVisitor
    {
        alias visit = super.visit;
    public:
        Scope* sc;
        bool result;

        extern (D) this(Scope* sc)
        {
            this.sc = sc;
        }

        override void visit(Expression)
        {
        }

        override void visit(SymOffExp e)
        {
            VarDeclaration v = e.var.isVarDeclaration();
            if (v)
                result = v.checkNestedReference(sc, Loc());
        }

        override void visit(VarExp e)
        {
            VarDeclaration v = e.var.isVarDeclaration();
            if (v)
                result = v.checkNestedReference(sc, Loc());
        }

        override void visit(ThisExp e)
        {
            if (e.var)
                result = e.var.checkNestedReference(sc, Loc());
        }

        override void visit(DeclarationExp e)
        {
            VarDeclaration v = e.declaration.isVarDeclaration();
            if (v)
            {
                result = v.checkNestedReference(sc, Loc());
                if (result)
                    return;
                /* Some expressions cause the frontend to create a temporary.
                 * For example, structs with cpctors replace the original
                 * expression e with:
                 *  __cpcttmp = __cpcttmp.cpctor(e);
                 *
                 * In this instance, we need to ensure that the original
                 * expression e does not have any nested references by
                 * checking the declaration initializer too.
                 */
                if (v._init && v._init.isExpInitializer())
                {
                    Expression ie = v._init.toExpression();
                    result = lambdaCheckForNestedRef(ie, sc);
                }
            }
        }
    }

    scope LambdaCheckForNestedRef v = new LambdaCheckForNestedRef(sc);
    walkPostorder(e, v);
    return v.result;
}
