root/trunk/src/cast.c

// Copyright (c) 1999-2010 by Digital Mars
// All Rights Reserved
// written by Walter Bright
// http://www.digitalmars.com
// License for redistribution is by either the Artistic License
// in artistic.txt, or the GNU General Public License in gnu.txt.
// See the included readme.txt for details.

#include <stdio.h>
#include <assert.h>

#include "rmem.h"

#include "expression.h"
#include "mtype.h"
#include "utf.h"
#include "declaration.h"
#include "aggregate.h"

/* ==================== implicitCast ====================== */

/**************************************
 * Do an implicit cast.
 * Issue error if it can't be done.
 */

Expression *Expression::implicitCastTo(Scope *sc, Type *t)
{
    //printf("Expression::implicitCastTo(%s of type %s) => %s\n", toChars(), type->toChars(), t->toChars());

    MATCH match = implicitConvTo(t);
    if (match)
    {   TY tyfrom = type->toBasetype()->ty;
        TY tyto = t->toBasetype()->ty;
#if DMDV1
        if (global.params.warnings &&
            Type::impcnvWarn[tyfrom][tyto] &&
            op != TOKint64)
        {
            Expression *e = optimize(WANTflags | WANTvalue);

            if (e->op == TOKint64)
                return e->implicitCastTo(sc, t);
            if (tyfrom == Tint32 &&
                (op == TOKadd || op == TOKmin ||
                 op == TOKand || op == TOKor || op == TOKxor)
               )
            {
                /* This is really only a semi-kludge fix,
                 * we really should look at the operands of op
                 * and see if they are narrower types.
                 * For example, b=b|b and b=b|7 and s=b+b should be allowed,
                 * but b=b|i should be an error.
                 */
                ;
            }
            else
            {
                warning("implicit conversion of expression (%s) of type %s to %s can cause loss of data",
                    toChars(), type->toChars(), t->toChars());
            }
        }
#endif
#if DMDV2
        if (match == MATCHconst && t == type->constOf())
        {
            Expression *e = copy();
            e->type = t;
            return e;
        }
#endif
        return castTo(sc, t);
    }

    Expression *e = optimize(WANTflags | WANTvalue);
    if (e != this)
        return e->implicitCastTo(sc, t);

#if 0
printf("ty = %d\n", type->ty);
print();
type->print();
printf("to:\n");
t->print();
printf("%p %p type: %s to: %s\n", type->deco, t->deco, type->deco, t->deco);
//printf("%p %p %p\n", type->nextOf()->arrayOf(), type, t);
fflush(stdout);
#endif
    if (t->ty != Terror && type->ty != Terror)
    {
        if (!t->deco)
        {   /* Can happen with:
             *    enum E { One }
             *    class A
             *    { static void fork(EDG dg) { dg(E.One); }
             *      alias void delegate(E) EDG;
             *    }
             * Should eventually make it work.
             */
            error("forward reference to type %s", t->toChars());
        }
        else if (t->reliesOnTident())
            error("forward reference to type %s", t->reliesOnTident()->toChars());

        error("cannot implicitly convert expression (%s) of type %s to %s",
            toChars(), type->toChars(), t->toChars());
    }
    return new ErrorExp();
}

Expression *StringExp::implicitCastTo(Scope *sc, Type *t)
{
    //printf("StringExp::implicitCastTo(%s of type %s) => %s\n", toChars(), type->toChars(), t->toChars());
    unsigned char committed = this->committed;
    Expression *e = Expression::implicitCastTo(sc, t);
    if (e->op == TOKstring)
    {
        // Retain polysemous nature if it started out that way
        ((StringExp *)e)->committed = committed;
    }
    return e;
}

Expression *ErrorExp::implicitCastTo(Scope *sc, Type *t)
{
    return this;
}

/*******************************************
 * Return !=0 if we can implicitly convert this to type t.
 * Don't do the actual cast.
 */

MATCH Expression::implicitConvTo(Type *t)
{
#if 0
    printf("Expression::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    //static int nest; if (++nest == 10) halt();
    if (!type)
    {   error("%s is not an expression", toChars());
        type = Type::terror;
    }
    Expression *e = optimize(WANTvalue | WANTflags);
    if (e->type == t)
        return MATCHexact;
    if (e != this)
    {   //printf("\toptimized to %s of type %s\n", e->toChars(), e->type->toChars());
        return e->implicitConvTo(t);
    }
    MATCH match = type->implicitConvTo(t);
    if (match != MATCHnomatch)
        return match;

    /* See if we can do integral narrowing conversions
     */
    if (type->isintegral() && t->isintegral() &&
        type->isTypeBasic() && t->isTypeBasic())
    {   IntRange ir = getIntRange();
        if (ir.imax <= t->sizemask())
            return MATCHconvert;
    }

#if 0
    Type *tb = t->toBasetype();
    if (tb->ty == Tdelegate)
    {   TypeDelegate *td = (TypeDelegate *)tb;
        TypeFunction *tf = (TypeFunction *)td->nextOf();

        if (!tf->varargs &&
            !(tf->arguments && tf->arguments->dim)
           )
        {
            match = type->implicitConvTo(tf->nextOf());
            if (match)
                return match;
            if (tf->nextOf()->toBasetype()->ty == Tvoid)
                return MATCHconvert;
        }
    }
#endif
    return MATCHnomatch;
}


MATCH IntegerExp::implicitConvTo(Type *t)
{
#if 0
    printf("IntegerExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH m = type->implicitConvTo(t);
    if (m >= MATCHconst)
        return m;

    TY ty = type->toBasetype()->ty;
    TY toty = t->toBasetype()->ty;

    if (m == MATCHnomatch && t->ty == Tenum)
        goto Lno;

    switch (ty)
    {
        case Tbit:
        case Tbool:
            value &= 1;
            ty = Tint32;
            break;

        case Tint8:
            value = (signed char)value;
            ty = Tint32;
            break;

        case Tchar:
        case Tuns8:
            value &= 0xFF;
            ty = Tint32;
            break;

        case Tint16:
            value = (short)value;
            ty = Tint32;
            break;

        case Tuns16:
        case Twchar:
            value &= 0xFFFF;
            ty = Tint32;
            break;

        case Tint32:
            value = (int)value;
            break;

        case Tuns32:
        case Tdchar:
            value &= 0xFFFFFFFF;
            ty = Tuns32;
            break;

        default:
            break;
    }

    // Only allow conversion if no change in value
    switch (toty)
    {
        case Tbit:
        case Tbool:
            if ((value & 1) != value)
                goto Lno;
            goto Lyes;

        case Tint8:
            if ((signed char)value != value)
                goto Lno;
            goto Lyes;

        case Tchar:
        case Tuns8:
            //printf("value = %llu %llu\n", (dinteger_t)(unsigned char)value, value);
            if ((unsigned char)value != value)
                goto Lno;
            goto Lyes;

        case Tint16:
            if ((short)value != value)
                goto Lno;
            goto Lyes;

        case Tuns16:
            if ((unsigned short)value != value)
                goto Lno;
            goto Lyes;

        case Tint32:
            if (ty == Tuns32)
            {
            }
            else if ((int)value != value)
                goto Lno;
            goto Lyes;

        case Tuns32:
            if (ty == Tint32)
            {
            }
            else if ((unsigned)value != value)
                goto Lno;
            goto Lyes;

        case Tdchar:
            if (value > 0x10FFFFUL)
                goto Lno;
            goto Lyes;

        case Twchar:
            if ((unsigned short)value != value)
                goto Lno;
            goto Lyes;

        case Tfloat32:
        {
            volatile float f;
            if (type->isunsigned())
            {
                f = (float)value;
                if (f != value)
                    goto Lno;
            }
            else
            {
                f = (float)(long long)value;
                if (f != (long long)value)
                    goto Lno;
            }
            goto Lyes;
        }

        case Tfloat64:
        {
            volatile double f;
            if (type->isunsigned())
            {
                f = (double)value;
                if (f != value)
                    goto Lno;
            }
            else
            {
                f = (double)(long long)value;
                if (f != (long long)value)
                    goto Lno;
            }
            goto Lyes;
        }

        case Tfloat80:
        {
            volatile long double f;
            if (type->isunsigned())
            {
                f = (long double)value;
                if (f != value)
                    goto Lno;
            }
            else
            {
                f = (long double)(long long)value;
                if (f != (long long)value)
                    goto Lno;
            }
            goto Lyes;
        }

        case Tpointer:
//printf("type = %s\n", type->toBasetype()->toChars());
//printf("t = %s\n", t->toBasetype()->toChars());
            if (ty == Tpointer &&
                type->toBasetype()->nextOf()->ty == t->toBasetype()->nextOf()->ty)
            {   /* Allow things like:
                 *      const char* P = cast(char *)3;
                 *      char* q = P;
                 */
                goto Lyes;
            }
            break;
    }
    return Expression::implicitConvTo(t);

Lyes:
    //printf("MATCHconvert\n");
    return MATCHconvert;

Lno:
    //printf("MATCHnomatch\n");
    return MATCHnomatch;
}

MATCH NullExp::implicitConvTo(Type *t)
{
#if 0
    printf("NullExp::implicitConvTo(this=%s, type=%s, t=%s, committed = %d)\n",
        toChars(), type->toChars(), t->toChars(), committed);
#endif
    if (this->type->equals(t))
        return MATCHexact;

    /* Allow implicit conversions from invariant to mutable|const,
     * and mutable to invariant. It works because, after all, a null
     * doesn't actually point to anything.
     */
    if (t->invariantOf()->equals(type->invariantOf()))
        return MATCHconst;

    // NULL implicitly converts to any pointer type or dynamic array
    if (type->ty == Tpointer && type->nextOf()->ty == Tvoid)
    {
        if (t->ty == Ttypedef)
            t = ((TypeTypedef *)t)->sym->basetype;
        if (t->ty == Tpointer || t->ty == Tarray ||
            t->ty == Taarray  || t->ty == Tclass ||
            t->ty == Tdelegate)
            return committed ? MATCHconvert : MATCHexact;
    }
    return Expression::implicitConvTo(t);
}

#if DMDV2
MATCH StructLiteralExp::implicitConvTo(Type *t)
{
#if 0
    printf("StructLiteralExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH m = Expression::implicitConvTo(t);
    if (m != MATCHnomatch)
        return m;
    if (type->ty == t->ty && type->ty == Tstruct &&
        ((TypeStruct *)type)->sym == ((TypeStruct *)t)->sym)
    {
        m = MATCHconst;
        for (int i = 0; i < elements->dim; i++)
        {   Expression *e = (Expression *)elements->data[i];
            Type *te = e->type;
            te = te->castMod(t->mod);
            MATCH m2 = e->implicitConvTo(te);
            //printf("\t%s => %s, match = %d\n", e->toChars(), te->toChars(), m2);
            if (m2 < m)
                m = m2;
        }
    }
    return m;
}
#endif

MATCH StringExp::implicitConvTo(Type *t)
{   MATCH m;

#if 0
    printf("StringExp::implicitConvTo(this=%s, committed=%d, type=%s, t=%s)\n",
        toChars(), committed, type->toChars(), t->toChars());
#endif
    if (!committed && t->ty == Tpointer && t->nextOf()->ty == Tvoid)
    {
        return MATCHnomatch;
    }
    if (type->ty == Tsarray || type->ty == Tarray || type->ty == Tpointer)
    {
        TY tyn = type->nextOf()->ty;
        if (tyn == Tchar || tyn == Twchar || tyn == Tdchar)
        {   Type *tn;
            MATCH m;

            switch (t->ty)
            {
                case Tsarray:
                    if (type->ty == Tsarray)
                    {
                        if (((TypeSArray *)type)->dim->toInteger() !=
                            ((TypeSArray *)t)->dim->toInteger())
                            return MATCHnomatch;
                        TY tynto = t->nextOf()->ty;
                        if (tynto == tyn)
                            return MATCHexact;
                        if (!committed && (tynto == Tchar || tynto == Twchar || tynto == Tdchar))
                            return MATCHexact;
                    }
                    else if (type->ty == Tarray)
                    {
                        if (length() >
                            ((TypeSArray *)t)->dim->toInteger())
                            return MATCHnomatch;
                        TY tynto = t->nextOf()->ty;
                        if (tynto == tyn)
                            return MATCHexact;
                        if (!committed && (tynto == Tchar || tynto == Twchar || tynto == Tdchar))
                            return MATCHexact;
                    }
                case Tarray:
                case Tpointer:
                    tn = t->nextOf();
                    m = MATCHexact;
                    if (type->nextOf()->mod != tn->mod)
                    {   if (!tn->isConst())
                            return MATCHnomatch;
                        m = MATCHconst;
                    }
                    switch (tn->ty)
                    {
                        case Tchar:
                        case Twchar:
                        case Tdchar:
                            if (!committed)
                                return m;
                            break;
                    }
                    break;
            }
        }
    }
    return Expression::implicitConvTo(t);
#if 0
    m = (MATCH)type->implicitConvTo(t);
    if (m)
    {
        return m;
    }

    return MATCHnomatch;
#endif
}

MATCH ArrayLiteralExp::implicitConvTo(Type *t)
{   MATCH result = MATCHexact;

#if 0
    printf("ArrayLiteralExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    Type *typeb = type->toBasetype();
    Type *tb = t->toBasetype();
    if ((tb->ty == Tarray || tb->ty == Tsarray) &&
        (typeb->ty == Tarray || typeb->ty == Tsarray))
    {
        if (tb->ty == Tsarray)
        {   TypeSArray *tsa = (TypeSArray *)tb;
            if (elements->dim != tsa->dim->toInteger())
                result = MATCHnomatch;
        }

        for (int i = 0; i < elements->dim; i++)
        {   Expression *e = (Expression *)elements->data[i];
            MATCH m = (MATCH)e->implicitConvTo(tb->nextOf());
            if (m < result)
                result = m;                     // remember worst match
            if (result == MATCHnomatch)
                break;                          // no need to check for worse
        }
        return result;
    }
    else
        return Expression::implicitConvTo(t);
}

MATCH AssocArrayLiteralExp::implicitConvTo(Type *t)
{   MATCH result = MATCHexact;

    Type *typeb = type->toBasetype();
    Type *tb = t->toBasetype();
    if (tb->ty == Taarray && typeb->ty == Taarray)
    {
        for (size_t i = 0; i < keys->dim; i++)
        {   Expression *e = (Expression *)keys->data[i];
            MATCH m = (MATCH)e->implicitConvTo(((TypeAArray *)tb)->index);
            if (m < result)
                result = m;                     // remember worst match
            if (result == MATCHnomatch)
                break;                          // no need to check for worse
            e = (Expression *)values->data[i];
            m = (MATCH)e->implicitConvTo(tb->nextOf());
            if (m < result)
                result = m;                     // remember worst match
            if (result == MATCHnomatch)
                break;                          // no need to check for worse
        }
        return result;
    }
    else
        return Expression::implicitConvTo(t);
}

MATCH AddrExp::implicitConvTo(Type *t)
{
#if 0
    printf("AddrExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH result;

    result = type->implicitConvTo(t);
    //printf("\tresult = %d\n", result);

    if (result == MATCHnomatch)
    {
        // Look for pointers to functions where the functions are overloaded.

        t = t->toBasetype();

        if (e1->op == TOKoverloadset &&
            (t->ty == Tpointer || t->ty == Tdelegate) && t->nextOf()->ty == Tfunction)
        {   OverExp *eo = (OverExp *)e1;
            FuncDeclaration *f = NULL;
            for (int i = 0; i < eo->vars->a.dim; i++)
            {   Dsymbol *s = (Dsymbol *)eo->vars->a.data[i];
                FuncDeclaration *f2 = s->isFuncDeclaration();
                assert(f2);
                if (f2->overloadExactMatch(t->nextOf()))
                {   if (f)
                        /* Error if match in more than one overload set,
                         * even if one is a 'better' match than the other.
                         */
                        ScopeDsymbol::multiplyDefined(loc, f, f2);
                    else
                        f = f2;
                    result = MATCHexact;
                }
            }
        }

        if (type->ty == Tpointer && type->nextOf()->ty == Tfunction &&
            t->ty == Tpointer && t->nextOf()->ty == Tfunction &&
            e1->op == TOKvar)
        {
            /* I don't think this can ever happen -
             * it should have been
             * converted to a SymOffExp.
             */
            assert(0);
            VarExp *ve = (VarExp *)e1;
            FuncDeclaration *f = ve->var->isFuncDeclaration();
            if (f && f->overloadExactMatch(t->nextOf()))
                result = MATCHexact;
        }
    }
    //printf("\tresult = %d\n", result);
    return result;
}

MATCH SymOffExp::implicitConvTo(Type *t)
{
#if 0
    printf("SymOffExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH result;

    result = type->implicitConvTo(t);
    //printf("\tresult = %d\n", result);

    if (result == MATCHnomatch)
    {
        // Look for pointers to functions where the functions are overloaded.
        FuncDeclaration *f;

        t = t->toBasetype();
        if (type->ty == Tpointer && type->nextOf()->ty == Tfunction &&
            (t->ty == Tpointer || t->ty == Tdelegate) && t->nextOf()->ty == Tfunction)
        {
            f = var->isFuncDeclaration();
            if (f)
            {   f = f->overloadExactMatch(t->nextOf());
                if (f)
                {   if ((t->ty == Tdelegate && (f->needThis() || f->isNested())) ||
                        (t->ty == Tpointer && !(f->needThis() || f->isNested())))
                    {
                        result = MATCHexact;
                    }
                }
            }
        }
    }
    //printf("\tresult = %d\n", result);
    return result;
}

MATCH DelegateExp::implicitConvTo(Type *t)
{
#if 0
    printf("DelegateExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH result;

    result = type->implicitConvTo(t);

    if (result == MATCHnomatch)
    {
        // Look for pointers to functions where the functions are overloaded.
        FuncDeclaration *f;

        t = t->toBasetype();
        if (type->ty == Tdelegate && type->nextOf()->ty == Tfunction &&
            t->ty == Tdelegate && t->nextOf()->ty == Tfunction)
        {
            if (func && func->overloadExactMatch(t->nextOf()))
                result = MATCHexact;
        }
    }
    return result;
}

MATCH OrExp::implicitConvTo(Type *t)
{
    MATCH result = Expression::implicitConvTo(t);

    if (result == MATCHnomatch)
    {
        MATCH m1 = e1->implicitConvTo(t);
        MATCH m2 = e2->implicitConvTo(t);

        // Pick the worst match
        result = (m1 < m2) ? m1 : m2;
    }
    return result;
}

MATCH XorExp::implicitConvTo(Type *t)
{
    MATCH result = Expression::implicitConvTo(t);

    if (result == MATCHnomatch)
    {
        MATCH m1 = e1->implicitConvTo(t);
        MATCH m2 = e2->implicitConvTo(t);

        // Pick the worst match
        result = (m1 < m2) ? m1 : m2;
    }
    return result;
}

MATCH CondExp::implicitConvTo(Type *t)
{
    MATCH m1 = e1->implicitConvTo(t);
    MATCH m2 = e2->implicitConvTo(t);
    //printf("CondExp: m1 %d m2 %d\n", m1, m2);

    // Pick the worst match
    return (m1 < m2) ? m1 : m2;
}

MATCH CommaExp::implicitConvTo(Type *t)
{
    return e2->implicitConvTo(t);
}

MATCH CastExp::implicitConvTo(Type *t)
{
#if 0
    printf("CastExp::implicitConvTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    MATCH result;

    result = type->implicitConvTo(t);

    if (result == MATCHnomatch)
    {
        if (t->isintegral() &&
            e1->type->isintegral() &&
            e1->implicitConvTo(t) != MATCHnomatch)
            result = MATCHconvert;
        else
            result = Expression::implicitConvTo(t);
    }
    return result;
}

/* ==================== castTo ====================== */

/**************************************
 * Do an explicit cast.
 */

Expression *Expression::castTo(Scope *sc, Type *t)
{
    //printf("Expression::castTo(this=%s, t=%s)\n", toChars(), t->toChars());
#if 0
    printf("Expression::castTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    if (type == t)
        return this;
    Expression *e = this;
    Type *tb = t->toBasetype();
    Type *typeb = type->toBasetype();
    if (tb != typeb)
    {
        // Do (type *) cast of (type [dim])
        if (tb->ty == Tpointer &&
            typeb->ty == Tsarray
           )
        {
            //printf("Converting [dim] to *\n");

            if (typeb->size(loc) == 0)
                e = new NullExp(loc);
            else
                e = new AddrExp(loc, e);
        }
#if 0
        else if (tb->ty == Tdelegate && type->ty != Tdelegate)
        {
            TypeDelegate *td = (TypeDelegate *)tb;
            TypeFunction *tf = (TypeFunction *)td->nextOf();
            return toDelegate(sc, tf->nextOf());
        }
#endif
        else
        {
            if (typeb->ty == Tstruct)
            {   TypeStruct *ts = (TypeStruct *)typeb;
                if (!(tb->ty == Tstruct && ts->sym == ((TypeStruct *)tb)->sym) &&
                    ts->sym->aliasthis)
                {   /* Forward the cast to our alias this member, rewrite to:
                     *   cast(to)e1.aliasthis
                     */
                    Expression *e1 = new DotIdExp(loc, this, ts->sym->aliasthis->ident);
                    Expression *e = new CastExp(loc, e1, tb);
                    e = e->semantic(sc);
                    return e;
                }
            }
            else if (typeb->ty == Tclass)
            {   TypeClass *ts = (TypeClass *)typeb;
                if (ts->sym->aliasthis)
                {
                    if (tb->ty == Tclass)
                    {
                        ClassDeclaration *cdfrom = typeb->isClassHandle();
                        ClassDeclaration *cdto   = tb->isClassHandle();
                        int offset;
                        if (cdto->isBaseOf(cdfrom, &offset))
                             goto L1;
                    }
                    /* Forward the cast to our alias this member, rewrite to:
                     *   cast(to)e1.aliasthis
                     */
                    Expression *e1 = new DotIdExp(loc, this, ts->sym->aliasthis->ident);
                    Expression *e = new CastExp(loc, e1, tb);
                    e = e->semantic(sc);
                    return e;
                }
             L1: ;
            }
            e = new CastExp(loc, e, tb);
        }
    }
    else
    {
        e = e->copy();  // because of COW for assignment to e->type
    }
    assert(e != this);
    e->type = t;
    //printf("Returning: %s\n", e->toChars());
    return e;
}


Expression *RealExp::castTo(Scope *sc, Type *t)
{   Expression *e = this;
    if (type != t)
    {
        if ((type->isreal() && t->isreal()) ||
            (type->isimaginary() && t->isimaginary())
           )
        {   e = copy();
            e->type = t;
        }
        else
            e = Expression::castTo(sc, t);
    }
    return e;
}


Expression *ComplexExp::castTo(Scope *sc, Type *t)
{   Expression *e = this;
    if (type != t)
    {
        if (type->iscomplex() && t->iscomplex())
        {   e = copy();
            e->type = t;
        }
        else
            e = Expression::castTo(sc, t);
    }
    return e;
}


Expression *NullExp::castTo(Scope *sc, Type *t)
{   NullExp *e;
    Type *tb;

    //printf("NullExp::castTo(t = %p)\n", t);
    if (type == t)
    {
        committed = 1;
        return this;
    }
    e = (NullExp *)copy();
    e->committed = 1;
    tb = t->toBasetype();
    e->type = type->toBasetype();
    if (tb != e->type)
    {
        // NULL implicitly converts to any pointer type or dynamic array
        if (e->type->ty == Tpointer && e->type->nextOf()->ty == Tvoid &&
            (tb->ty == Tpointer || tb->ty == Tarray || tb->ty == Taarray ||
             tb->ty == Tdelegate))
        {
#if 0
            if (tb->ty == Tdelegate)
            {   TypeDelegate *td = (TypeDelegate *)tb;
                TypeFunction *tf = (TypeFunction *)td->nextOf();

                if (!tf->varargs &&
                    !(tf->arguments && tf->arguments->dim)
                   )
                {
                    return Expression::castTo(sc, t);
                }
            }
#endif
        }
        else
        {
            return e->Expression::castTo(sc, t);
        }
    }
    e->type = t;
    return e;
}

Expression *StringExp::castTo(Scope *sc, Type *t)
{
    /* This follows copy-on-write; any changes to 'this'
     * will result in a copy.
     * The this->string member is considered immutable.
     */
    int copied = 0;

    //printf("StringExp::castTo(t = %s), '%s' committed = %d\n", t->toChars(), toChars(), committed);

    if (!committed && t->ty == Tpointer && t->nextOf()->ty == Tvoid)
    {
        error("cannot convert string literal to void*");
        return new ErrorExp();
    }

    StringExp *se = this;
    if (!committed)
    {   se = (StringExp *)copy();
        se->committed = 1;
        copied = 1;
    }

    if (type == t)
    {
        return se;
    }

    Type *tb = t->toBasetype();
    //printf("\ttype = %s\n", type->toChars());
    if (tb->ty == Tdelegate && type->toBasetype()->ty != Tdelegate)
        return Expression::castTo(sc, t);

    Type *typeb = type->toBasetype();
    if (typeb == tb)
    {
        if (!copied)
        {   se = (StringExp *)copy();
            copied = 1;
        }
        se->type = t;
        return se;
    }

    if (committed && tb->ty == Tsarray && typeb->ty == Tarray)
    {
        se = (StringExp *)copy();
        se->sz = tb->nextOf()->size();
        se->len = (len * sz) / se->sz;
        se->committed = 1;
        se->type = t;
        return se;
    }

    if (tb->ty != Tsarray && tb->ty != Tarray && tb->ty != Tpointer)
    {   if (!copied)
        {   se = (StringExp *)copy();
            copied = 1;
        }
        goto Lcast;
    }
    if (typeb->ty != Tsarray && typeb->ty != Tarray && typeb->ty != Tpointer)
    {   if (!copied)
        {   se = (StringExp *)copy();
            copied = 1;
        }
        goto Lcast;
    }

    if (typeb->nextOf()->size() == tb->nextOf()->size())
    {
        if (!copied)
        {   se = (StringExp *)copy();
            copied = 1;
        }
        if (tb->ty == Tsarray)
            goto L2;    // handle possible change in static array dimension
        se->type = t;
        return se;
    }

    if (committed)
        goto Lcast;

#define X(tf,tt)        ((tf) * 256 + (tt))
    {
    OutBuffer buffer;
    size_t newlen = 0;
    int tfty = typeb->nextOf()->toBasetype()->ty;
    int ttty = tb->nextOf()->toBasetype()->ty;
    switch (X(tfty, ttty))
    {
        case X(Tchar, Tchar):
        case X(Twchar,Twchar):
        case X(Tdchar,Tdchar):
            break;

        case X(Tchar, Twchar):
            for (size_t u = 0; u < len;)
            {   unsigned c;
                const char *p = utf_decodeChar((unsigned char *)se->string, len, &u, &c);
                if (p)
                    error("%s", p);
                else
                    buffer.writeUTF16(c);
            }
            newlen = buffer.offset / 2;
            buffer.writeUTF16(0);
            goto L1;

        case X(Tchar, Tdchar):
            for (size_t u = 0; u < len;)
            {   unsigned c;
                const char *p = utf_decodeChar((unsigned char *)se->string, len, &u, &c);
                if (p)
                    error("%s", p);
                buffer.write4(c);
                newlen++;
            }
            buffer.write4(0);
            goto L1;

        case X(Twchar,Tchar):
            for (size_t u = 0; u < len;)
            {   unsigned c;
                const char *p = utf_decodeWchar((unsigned short *)se->string, len, &u, &c);
                if (p)
                    error("%s", p);
                else
                    buffer.writeUTF8(c);
            }
            newlen = buffer.offset;
            buffer.writeUTF8(0);
            goto L1;

        case X(Twchar,Tdchar):
            for (size_t u = 0; u < len;)
            {   unsigned c;
                const char *p = utf_decodeWchar((unsigned short *)se->string, len, &u, &c);
                if (p)
                    error("%s", p);
                buffer.write4(c);
                newlen++;
            }
            buffer.write4(0);
            goto L1;

        case X(Tdchar,Tchar):
            for (size_t u = 0; u < len; u++)
            {
                unsigned c = ((unsigned *)se->string)[u];
                if (!utf_isValidDchar(c))
                    error("invalid UCS-32 char \\U%08x", c);
                else
                    buffer.writeUTF8(c);
                newlen++;
            }
            newlen = buffer.offset;
            buffer.writeUTF8(0);
            goto L1;

        case X(Tdchar,Twchar):
            for (size_t u = 0; u < len; u++)
            {
                unsigned c = ((unsigned *)se->string)[u];
                if (!utf_isValidDchar(c))
                    error("invalid UCS-32 char \\U%08x", c);
                else
                    buffer.writeUTF16(c);
                newlen++;
            }
            newlen = buffer.offset / 2;
            buffer.writeUTF16(0);
            goto L1;

        L1:
            if (!copied)
            {   se = (StringExp *)copy();
                copied = 1;
            }
            se->string = buffer.extractData();
            se->len = newlen;
            se->sz = tb->nextOf()->size();
            break;

        default:
            assert(typeb->nextOf()->size() != tb->nextOf()->size());
            goto Lcast;
    }
    }
#undef X
L2:
    assert(copied);

    // See if need to truncate or extend the literal
    if (tb->ty == Tsarray)
    {
        int dim2 = ((TypeSArray *)tb)->dim->toInteger();

        //printf("dim from = %d, to = %d\n", se->len, dim2);

        // Changing dimensions
        if (dim2 != se->len)
        {
            // Copy when changing the string literal
            unsigned newsz = se->sz;
            void *s;
            int d;

            d = (dim2 < se->len) ? dim2 : se->len;
            s = (unsigned char *)mem.malloc((dim2 + 1) * newsz);
            memcpy(s, se->string, d * newsz);
            // Extend with 0, add terminating 0
            memset((char *)s + d * newsz, 0, (dim2 + 1 - d) * newsz);
            se->string = s;
            se->len = dim2;
        }
    }
    se->type = t;
    return se;

Lcast:
    Expression *e = new CastExp(loc, se, t);
    e->type = t;        // so semantic() won't be run on e
    return e;
}

Expression *AddrExp::castTo(Scope *sc, Type *t)
{
    Type *tb;

#if 0
    printf("AddrExp::castTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    Expression *e = this;

    tb = t->toBasetype();
    type = type->toBasetype();
    if (tb != type)
    {
        // Look for pointers to functions where the functions are overloaded.

        if (e1->op == TOKoverloadset &&
            (t->ty == Tpointer || t->ty == Tdelegate) && t->nextOf()->ty == Tfunction)
        {   OverExp *eo = (OverExp *)e1;
            FuncDeclaration *f = NULL;
            for (int i = 0; i < eo->vars->a.dim; i++)
            {   Dsymbol *s = (Dsymbol *)eo->vars->a.data[i];
                FuncDeclaration *f2 = s->isFuncDeclaration();
                assert(f2);
                if (f2->overloadExactMatch(t->nextOf()))
                {   if (f)
                        /* Error if match in more than one overload set,
                         * even if one is a 'better' match than the other.
                         */
                        ScopeDsymbol::multiplyDefined(loc, f, f2);
                    else
                        f = f2;
                }
            }
            if (f)
            {   f->tookAddressOf++;
                SymOffExp *se = new SymOffExp(loc, f, 0, 0);
                se->semantic(sc);
                // Let SymOffExp::castTo() do the heavy lifting
                return se->castTo(sc, t);
            }
        }


        if (type->ty == Tpointer && type->nextOf()->ty == Tfunction &&
            tb->ty == Tpointer && tb->nextOf()->ty == Tfunction &&
            e1->op == TOKvar)
        {
            VarExp *ve = (VarExp *)e1;
            FuncDeclaration *f = ve->var->isFuncDeclaration();
            if (f)
            {
                assert(0);      // should be SymOffExp instead
                f = f->overloadExactMatch(tb->nextOf());
                if (f)
                {
                    e = new VarExp(loc, f);
                    e->type = f->type;
                    e = new AddrExp(loc, e);
                    e->type = t;
                    return e;
                }
            }
        }
        e = Expression::castTo(sc, t);
    }
    e->type = t;
    return e;
}


Expression *TupleExp::castTo(Scope *sc, Type *t)
{   TupleExp *e = (TupleExp *)copy();
    e->exps = (Expressions *)exps->copy();
    for (size_t i = 0; i < e->exps->dim; i++)
    {   Expression *ex = (Expression *)e->exps->data[i];
        ex = ex->castTo(sc, t);
        e->exps->data[i] = (void *)ex;
    }
    return e;
}


Expression *ArrayLiteralExp::castTo(Scope *sc, Type *t)
{
#if 0
    printf("ArrayLiteralExp::castTo(this=%s, type=%s, => %s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    if (type == t)
        return this;
    ArrayLiteralExp *e = this;
    Type *typeb = type->toBasetype();
    Type *tb = t->toBasetype();
    if ((tb->ty == Tarray || tb->ty == Tsarray) &&
        (typeb->ty == Tarray || typeb->ty == Tsarray) &&
        // Not trying to convert non-void[] to void[]
        !(tb->nextOf()->toBasetype()->ty == Tvoid && typeb->nextOf()->toBasetype()->ty != Tvoid))
    {
        if (tb->ty == Tsarray)
        {   TypeSArray *tsa = (TypeSArray *)tb;
            if (elements->dim != tsa->dim->toInteger())
                goto L1;
        }

        e = (ArrayLiteralExp *)copy();
        e->elements = (Expressions *)elements->copy();
        for (int i = 0; i < elements->dim; i++)
        {   Expression *ex = (Expression *)elements->data[i];
            ex = ex->castTo(sc, tb->nextOf());
            e->elements->data[i] = (void *)ex;
        }
        e->type = t;
        return e;
    }
    if (tb->ty == Tpointer && typeb->ty == Tsarray)
    {
        Type *tp = typeb->nextOf()->pointerTo();
        if (!tp->equals(e->type))
        {   e = (ArrayLiteralExp *)copy();
            e->type = tp;
        }
    }
L1:
    return e->Expression::castTo(sc, t);
}

Expression *AssocArrayLiteralExp::castTo(Scope *sc, Type *t)
{
    if (type == t)
        return this;
    AssocArrayLiteralExp *e = this;
    Type *typeb = type->toBasetype();
    Type *tb = t->toBasetype();
    if (tb->ty == Taarray && typeb->ty == Taarray &&
        tb->nextOf()->toBasetype()->ty != Tvoid)
    {
        e = (AssocArrayLiteralExp *)copy();
        e->keys = (Expressions *)keys->copy();
        e->values = (Expressions *)values->copy();
        assert(keys->dim == values->dim);
        for (size_t i = 0; i < keys->dim; i++)
        {   Expression *ex = (Expression *)values->data[i];
            ex = ex->castTo(sc, tb->nextOf());
            e->values->data[i] = (void *)ex;

            ex = (Expression *)keys->data[i];
            ex = ex->castTo(sc, ((TypeAArray *)tb)->index);
            e->keys->data[i] = (void *)ex;
        }
        e->type = t;
        return e;
    }
L1:
    return e->Expression::castTo(sc, t);
}

Expression *SymOffExp::castTo(Scope *sc, Type *t)
{
#if 0
    printf("SymOffExp::castTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    if (type == t && hasOverloads == 0)
        return this;
    Expression *e;
    Type *tb = t->toBasetype();
    Type *typeb = type->toBasetype();
    if (tb != typeb)
    {
        // Look for pointers to functions where the functions are overloaded.
        FuncDeclaration *f;

        if (hasOverloads &&
            typeb->ty == Tpointer && typeb->nextOf()->ty == Tfunction &&
            (tb->ty == Tpointer || tb->ty == Tdelegate) && tb->nextOf()->ty == Tfunction)
        {
            f = var->isFuncDeclaration();
            if (f)
            {
                f = f->overloadExactMatch(tb->nextOf());
                if (f)
                {
                    if (tb->ty == Tdelegate)
                    {
                        if (f->needThis() && hasThis(sc))
                        {
                            e = new DelegateExp(loc, new ThisExp(loc), f);
                            e = e->semantic(sc);
                        }
                        else if (f->isNested())
                        {
                            e = new DelegateExp(loc, new IntegerExp(0), f);
                            e = e->semantic(sc);
                        }
                        else if (f->needThis())
                        {   error("no 'this' to create delegate for %s", f->toChars());
                            return new ErrorExp();
                        }
                        else
                        {   error("cannot cast from function pointer to delegate");
                            return new ErrorExp();
                        }
                    }
                    else
                    {
                        e = new SymOffExp(loc, f, 0);
                        e->type = t;
                    }
#if DMDV2
                    f->tookAddressOf++;
#endif
                    return e;
                }
            }
        }
        e = Expression::castTo(sc, t);
    }
    else
    {   e = copy();
        e->type = t;
        ((SymOffExp *)e)->hasOverloads = 0;
    }
    return e;
}

Expression *DelegateExp::castTo(Scope *sc, Type *t)
{
#if 0
    printf("DelegateExp::castTo(this=%s, type=%s, t=%s)\n",
        toChars(), type->toChars(), t->toChars());
#endif
    static char msg[] = "cannot form delegate due to covariant return type";

    Expression *e = this;
    Type *tb = t->toBasetype();
    Type *typeb = type->toBasetype();
    if (tb != typeb)
    {
        // Look for delegates to functions where the functions are overloaded.
        FuncDeclaration *f;

        if (typeb->ty == Tdelegate && typeb->nextOf()->ty == Tfunction &&
            tb->ty == Tdelegate && tb->nextOf()->ty == Tfunction)
        {
            if (func)
            {
                f = func->overloadExactMatch(tb->nextOf());
                if (f)
                {   int offset;
                    if (f->tintro && f->tintro->nextOf()->isBaseOf(f->type->nextOf(), &offset) && offset)
                        error("%s", msg);
                    f->tookAddressOf++;
                    e = new DelegateExp(loc, e1, f);
                    e->type = t;
                    return e;
                }
                if (func->tintro)
                    error("%s", msg);
            }
        }
        e = Expression::castTo(sc, t);
    }
    else
    {   int offset;

        func->tookAddressOf++;
        if (func->tintro && func->tintro->nextOf()->isBaseOf(func->type->nextOf(), &offset) && offset)
            error("%s", msg);
        e = copy();
        e->type = t;
    }
    return e;
}

Expression *CondExp::castTo(Scope *sc, Type *t)
{
    Expression *e = this;

    if (type != t)
    {
        if (1 || e1->op == TOKstring || e2->op == TOKstring)
        {   e = new CondExp(loc, econd, e1->castTo(sc, t), e2->castTo(sc, t));
            e->type = t;
        }
        else
            e = Expression::castTo(sc, t);
    }
    return e;
}

Expression *CommaExp::castTo(Scope *sc, Type *t)
{
    Expression *e2c = e2->castTo(sc, t);
    Expression *e;

    if (e2c != e2)
    {
        e = new CommaExp(loc, e1, e2c);
        e->type = e2c->type;
    }
    else
    {   e = this;
        e->type = e2->type;
    }
    return e;
}

/* ==================== ====================== */

/****************************************
 * Scale addition/subtraction to/from pointer.
 */

Expression *BinExp::scaleFactor(Scope *sc)
{   d_uns64 stride;
    Type *t1b = e1->type->toBasetype();
    Type *t2b = e2->type->toBasetype();

    if (t1b->ty == Tpointer && t2b->isintegral())
    {   // Need to adjust operator by the stride
        // Replace (ptr + int) with (ptr + (int * stride))
        Type *t = Type::tptrdiff_t;

        stride = t1b->nextOf()->size(loc);
        if (!t->equals(t2b))
            e2 = e2->castTo(sc, t);
        e2 = new MulExp(loc, e2, new IntegerExp(0, stride, t));
        e2->type = t;
        type = e1->type;
    }
    else if (t2b->ty == Tpointer && t1b->isintegral())
    {   // Need to adjust operator by the stride
        // Replace (int + ptr) with (ptr + (int * stride))
        Type *t = Type::tptrdiff_t;
        Expression *e;

        stride = t2b->nextOf()->size(loc);
        if (!t->equals(t1b))
            e = e1->castTo(sc, t);
        else
            e = e1;
        e = new MulExp(loc, e, new IntegerExp(0, stride, t));
        e->type = t;
        type = e2->type;
        e1 = e2;
        e2 = e;
    }
    return this;
}

/**************************************
 * Return true if e is an empty array literal with dimensionality
 * equal to or less than type of other array.
 * [], [[]], [[[]]], etc.
 * I.e., make sure that [1,2] is compatible with [],
 * [[1,2]] is compatible with [[]], etc.
 */
bool isVoidArrayLiteral(Expression *e, Type *other)
{
    while (e->op == TOKarrayliteral && e->type->ty == Tarray
        && (((ArrayLiteralExp *)e)->elements->dim == 1))
    {
        e = (Expression *)((ArrayLiteralExp *)e)->elements->data[0];
        if (other->ty == Tsarray || other->ty == Tarray)
            other = other->nextOf();
        else
            return false;
    }
    if (other->ty != Tsarray && other->ty != Tarray)
        return false;
    Type *t = e->type;
    return (e->op == TOKarrayliteral && t->ty == Tarray &&
        t->nextOf()->ty == Tvoid &&
        ((ArrayLiteralExp *)e)->elements->dim == 0);
}


/**************************************
 * Combine types.
 * Output:
 *      *pt     merged type, if *pt is not NULL
 *      *pe1    rewritten e1
 *      *pe2    rewritten e2
 * Returns:
 *      !=0     success
 *      0       failed
 */

int typeMerge(Scope *sc, Expression *e, Type **pt, Expression **pe1, Expression **pe2)
{
    //printf("typeMerge() %s op %s\n", (*pe1)->toChars(), (*pe2)->toChars());
    //dump(0);

    Expression *e1 = (*pe1)->integralPromotions(sc);
    Expression *e2 = (*pe2)->integralPromotions(sc);

    Type *t1 = e1->type;
    Type *t2 = e2->type;
    assert(t1);
    Type *t = t1;

    //if (t1) printf("\tt1 = %s\n", t1->toChars());
    //if (t2) printf("\tt2 = %s\n", t2->toChars());
#ifdef DEBUG
    if (!t2) printf("\te2 = '%s'\n", e2->toChars());
#endif
    assert(t2);

    Type *t1b = t1->toBasetype();
    Type *t2b = t2->toBasetype();

    TY ty = (TY)Type::impcnvResult[t1b->ty][t2b->ty];
    if (ty != Terror)
    {
        TY ty1 = (TY)Type::impcnvType1[t1b->ty][t2b->ty];
        TY ty2 = (TY)Type::impcnvType2[t1b->ty][t2b->ty];

        if (t1b->ty == ty1)     // if no promotions
        {
            if (t1 == t2)
            {
                t = t1;
                goto Lret;
            }

            if (t1b == t2b)
            {
                t = t1b;
                goto Lret;
            }
        }

        t = Type::basic[ty];

        t1 = Type::basic[ty1];
        t2 = Type::basic[ty2];
        e1 = e1->castTo(sc, t1);
        e2 = e2->castTo(sc, t2);
        //printf("after typeCombine():\n");
        //dump(0);
        //printf("ty = %d, ty1 = %d, ty2 = %d\n", ty, ty1, ty2);
        goto Lret;
    }

    t1 = t1b;
    t2 = t2b;

Lagain:
    if (t1 == t2)
    {
    }
    else if (t1->ty == Tpointer && t2->ty == Tpointer)
    {
        // Bring pointers to compatible type
        Type *t1n = t1->nextOf();
        Type *t2n = t2->nextOf();

        if (t1n == t2n)
            ;
        else if (t1n->ty == Tvoid)      // pointers to void are always compatible
            t = t2;
        else if (t2n->ty == Tvoid)
            ;
        else if (t1n->mod != t2n->mod)
        {
            t1 = t1n->mutableOf()->constOf()->pointerTo();
            t2 = t2n->mutableOf()->constOf()->pointerTo();
            t = t1;
            goto Lagain;
        }
        else if (t1n->ty == Tclass && t2n->ty == Tclass)
        {   ClassDeclaration *cd1 = t1n->isClassHandle();
            ClassDeclaration *cd2 = t2n->isClassHandle();
            int offset;

            if (cd1->isBaseOf(cd2, &offset))
            {
                if (offset)
                    e2 = e2->castTo(sc, t);
            }
            else if (cd2->isBaseOf(cd1, &offset))
            {
                t = t2;
                if (offset)
                    e1 = e1->castTo(sc, t);
            }
            else
                goto Lincompatible;
        }
        else
            goto Lincompatible;
    }
    else if ((t1->ty == Tsarray || t1->ty == Tarray) &&
             (e2->op == TOKnull && t2->ty == Tpointer && t2->nextOf()->ty == Tvoid ||
              // if e2 is void[]
              e2->op == TOKarrayliteral && t2->ty == Tsarray && t2->nextOf()->ty == Tvoid && ((TypeSArray *)t2)->dim->toInteger() == 0 ||
              isVoidArrayLiteral(e2, t1))
            )
    {   /*  (T[n] op void*)   => T[]
         *  (T[]  op void*)   => T[]
         *  (T[n] op void[0]) => T[]
         *  (T[]  op void[0]) => T[]
         *  (T[n] op void[])  => T[]
         *  (T[]  op void[])  => T[]
         */
        goto Lx1;
    }
    else if ((t2->ty == Tsarray || t2->ty == Tarray) &&
             (e1->op == TOKnull && t1->ty == Tpointer && t1->nextOf()->ty == Tvoid ||
              e1->op == TOKarrayliteral && t1->ty == Tsarray && t1->nextOf()->ty == Tvoid && ((TypeSArray *)t1)->dim->toInteger() == 0 ||
              isVoidArrayLiteral(e1, t2))
            )
    {   /*  (void*   op T[n]) => T[]
         *  (void*   op T[])  => T[]
         *  (void[0] op T[n]) => T[]
         *  (void[0] op T[])  => T[]
         *  (void[]  op T[n]) => T[]
         *  (void[]  op T[])  => T[]
         */
        goto Lx2;
    }
    else if ((t1->ty == Tsarray || t1->ty == Tarray) && t1->implicitConvTo(t2))
    {
        goto Lt2;
    }
    else if ((t2->ty == Tsarray || t2->ty == Tarray) && t2->implicitConvTo(t1))
    {
        goto Lt1;
    }
    /* If one is mutable and the other invariant, then retry
     * with both of them as const
     */
    else if ((t1->ty == Tsarray || t1->ty == Tarray || t1->ty == Tpointer) &&
             (t2->ty == Tsarray || t2->ty == Tarray || t2->ty == Tpointer) &&
             t1->nextOf()->mod != t2->nextOf()->mod
            )
    {   unsigned char mod = MODmerge(t1->nextOf()->mod, t2->nextOf()->mod);

        if (t1->ty == Tpointer)
            t1 = t1->nextOf()->castMod(mod)->pointerTo();
        else
            t1 = t1->nextOf()->castMod(mod)->arrayOf();

        if (t2->ty == Tpointer)
            t2 = t2->nextOf()->castMod(mod)->pointerTo();
        else
            t2 = t2->nextOf()->castMod(mod)->arrayOf();
        t = t1;
        goto Lagain;
    }
    else if (t1->ty == Tclass || t2->ty == Tclass)
    {
        if (t1->mod != t2->mod)
        {   unsigned char mod = MODmerge(t1->mod, t2->mod);
            t1 = t1->castMod(mod);
            t2 = t2->castMod(mod);
            t = t1;
            goto Lagain;
        }

        while (1)
        {
            int i1 = e2->implicitConvTo(t1);
            int i2 = e1->implicitConvTo(t2);

            if (i1 && i2)
            {
                // We have the case of class vs. void*, so pick class
                if (t1->ty == Tpointer)
                    i1 = 0;
                else if (t2->ty == Tpointer)
                    i2 = 0;
            }

            if (i2)
            {
                goto Lt2;
            }
            else if (i1)
            {
                goto Lt1;
            }
            else if (t1->ty == Tclass && t2->ty == Tclass)
            {   TypeClass *tc1 = (TypeClass *)t1;
                TypeClass *tc2 = (TypeClass *)t2;

                /* Pick 'tightest' type
                 */
                ClassDeclaration *cd1 = tc1->sym->baseClass;
                ClassDeclaration *cd2 = tc2->sym->baseClass;

                if (cd1 && cd2)
                {   t1 = cd1->type;
                    t2 = cd2->type;
                }
                else if (cd1)
                    t1 = cd1->type;
                else if (cd2)
                    t2 = cd2->type;
                else
                    goto Lincompatible;
            }
            else
                goto Lincompatible;
        }
    }
    else if (t1->ty == Tstruct && t2->ty == Tstruct)
    {
        if (((TypeStruct *)t1)->sym != ((TypeStruct *)t2)->sym)
            goto Lincompatible;
    }
    else if ((e1->op == TOKstring || e1->op == TOKnull) && e1->implicitConvTo(t2))
    {
        goto Lt2;
    }
    else if ((e2->op == TOKstring || e2->op == TOKnull) && e2->implicitConvTo(t1))
    {
        goto Lt1;
    }
    else if (t1->ty == Tsarray && t2->ty == Tsarray &&
             e2->implicitConvTo(t1->nextOf()->arrayOf()))
    {
     Lx1:
        t = t1->nextOf()->arrayOf();    // T[]
        e1 = e1->castTo(sc, t);
        e2 = e2->castTo(sc, t);
    }
    else if (t1->ty == Tsarray && t2->ty == Tsarray &&
             e1->implicitConvTo(t2->nextOf()->arrayOf()))
    {
     Lx2:
        t = t2->nextOf()->arrayOf();
        e1 = e1->castTo(sc, t);
        e2 = e2->castTo(sc, t);
    }
    else if (t1->isintegral() && t2->isintegral())
    {
        assert(0);
    }
    else if (e1->isArrayOperand() && t1->ty == Tarray &&
             e2->implicitConvTo(t1->nextOf()))
    {   // T[] op T
        e2 = e2->castTo(sc, t1->nextOf());
        t = t1->nextOf()->arrayOf();
    }
    else if (e2->isArrayOperand() && t2->ty == Tarray &&
             e1->implicitConvTo(t2->nextOf()))
    {   // T op T[]
        e1 = e1->castTo(sc, t2->nextOf());
        t = t2->nextOf()->arrayOf();

        //printf("test %s\n", e->toChars());
        e1 = e1->optimize(WANTvalue);
        if (e && e->isCommutative() && e1->isConst())
        {   /* Swap operands to minimize number of functions generated
             */
            //printf("swap %s\n", e->toChars());
            Expression *tmp = e1;
            e1 = e2;
            e2 = tmp;
        }
    }
    else
    {
     Lincompatible:
        return 0;
    }
Lret:
    if (!*pt)
        *pt = t;
    *pe1 = e1;
    *pe2 = e2;
#if 0
    printf("-typeMerge() %s op %s\n", e1->toChars(), e2->toChars());
    if (e1->type) printf("\tt1 = %s\n", e1->type->toChars());
    if (e2->type) printf("\tt2 = %s\n", e2->type->toChars());
    printf("\ttype = %s\n", t->toChars());
#endif
    //dump(0);
    return 1;


Lt1:
    e2 = e2->castTo(sc, t1);
    t = t1;
    goto Lret;

Lt2:
    e1 = e1->castTo(sc, t2);
    t = t2;
    goto Lret;
}

/************************************
 * Bring leaves to common type.
 */

Expression *BinExp::typeCombine(Scope *sc)
{
    Type *t1 = e1->type->toBasetype();
    Type *t2 = e2->type->toBasetype();

    if (op == TOKmin || op == TOKadd)
    {
        // struct+struct, where the structs are the same type, and class+class are errors
        if (t1->ty == Tstruct)
        {
            if (t2->ty == Tstruct &&
                ((TypeStruct *)t1)->sym == ((TypeStruct *)t2)->sym)
                goto Lerror;
        }
        else if (t1->ty == Tclass)
        {
            if (t2->ty == Tclass)
                goto Lerror;
        }
    }

    if (!typeMerge(sc, this, &type, &e1, &e2))
        goto Lerror;
    return this;

Lerror:
    incompatibleTypes();
    type = Type::terror;
    e1 = new ErrorExp();
    e2 = new ErrorExp();
    return new ErrorExp();
}

/***********************************
 * Do integral promotions (convertchk).
 * Don't convert <array of> to <pointer to>
 */

Expression *Expression::integralPromotions(Scope *sc)
{
    Expression *e = this;

    //printf("integralPromotions %s %s\n", e->toChars(), e->type->toChars());
    switch (type->toBasetype()->ty)
    {
        case Tvoid:
            error("void has no value");
            return new ErrorExp();

        case Tint8:
        case Tuns8:
        case Tint16:
        case Tuns16:
        case Tbit:
        case Tbool:
        case Tchar:
        case Twchar:
            e = e->castTo(sc, Type::tint32);
            break;

        case Tdchar:
            e = e->castTo(sc, Type::tuns32);
            break;
    }
    return e;
}

/***********************************
 * See if both types are arrays that can be compared
 * for equality. Return !=0 if so.
 * If they are arrays, but incompatible, issue error.
 * This is to enable comparing things like an immutable
 * array with a mutable one.
 */

int arrayTypeCompatible(Loc loc, Type *t1, Type *t2)
{
    t1 = t1->toBasetype();
    t2 = t2->toBasetype();

    if ((t1->ty == Tarray || t1->ty == Tsarray || t1->ty == Tpointer) &&
        (t2->ty == Tarray || t2->ty == Tsarray || t2->ty == Tpointer))
    {
        if (t1->nextOf()->implicitConvTo(t2->nextOf()) < MATCHconst &&
            t2->nextOf()->implicitConvTo(t1->nextOf()) < MATCHconst &&
            (t1->nextOf()->ty != Tvoid && t2->nextOf()->ty != Tvoid))
        {
            error(loc, "array equality comparison type mismatch, %s vs %s", t1->toChars(), t2->toChars());
        }
        return 1;
    }
    return 0;
}

/***********************************
 * See if both types are arrays that can be compared
 * for equality without any casting. Return !=0 if so.
 * This is to enable comparing things like an immutable
 * array with a mutable one.
 */
int arrayTypeCompatibleWithoutCasting(Loc loc, Type *t1, Type *t2)
{
    t1 = t1->toBasetype();
    t2 = t2->toBasetype();

    if ((t1->ty == Tarray || t1->ty == Tsarray || t1->ty == Tpointer) &&
        t2->ty == t1->ty)
    {
        if (t1->nextOf()->implicitConvTo(t2->nextOf()) >= MATCHconst ||
            t2->nextOf()->implicitConvTo(t1->nextOf()) >= MATCHconst)
            return 1;
    }
    return 0;
}


/******************************************************************/

/* Determine the integral ranges of an expression.
 * This is used to determine if implicit narrowing conversions will
 * be allowed.
 */

uinteger_t getMask(uinteger_t v)
{
    uinteger_t u = 0;
    if (v >= 0x80)
        u = 0xFF;
    while (u < v)
        u = (u << 1) | 1;
    return u;
}

IntRange Expression::getIntRange()
{
    IntRange ir;
    ir.imin = 0;
    if (type->isintegral())
        ir.imax = type->sizemask();
    else
        ir.imax = 0xFFFFFFFFFFFFFFFFULL; // assume the worst
    return ir;
}

IntRange IntegerExp::getIntRange()
{
    IntRange ir;
    ir.imin = value & type->sizemask();
    ir.imax = ir.imin;
    return ir;
}

IntRange CastExp::getIntRange()
{
    IntRange ir;
    ir = e1->getIntRange();
    // Do sign extension
    switch (e1->type->toBasetype()->ty)
    {
        case Tint8:
            if (ir.imax & 0x80)
                ir.imax |= 0xFFFFFFFFFFFFFF00ULL;
            break;
        case Tint16:
            if (ir.imax & 0x8000)
                ir.imax |= 0xFFFFFFFFFFFF0000ULL;
            break;
        case Tint32:
            if (ir.imax & 0x80000000)
                ir.imax |= 0xFFFFFFFF00000000ULL;
            break;
    }
    if (type->isintegral())
    {
        ir.imin &= type->sizemask();
        ir.imax &= type->sizemask();
    }
//printf("CastExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
    return ir;
}

IntRange DivExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    if (!(e1->type->isunsigned() || ir1.imax < 0x8000000000000000ULL) &&
        !(e2->type->isunsigned() || ir2.imax < 0x8000000000000000ULL))
    {
        return Expression::getIntRange();
    }

    if (ir2.imax == 0 || ir2.imin == 0)
        return Expression::getIntRange();

    ir.imin = ir1.imin / ir2.imax;
    ir.imax = ir1.imax / ir2.imin;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("DivExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange AndExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = ir1.imin;
    if (ir2.imin < ir.imin)
        ir.imin = ir2.imin;

    ir.imax = ir1.imax;
    if (ir2.imax > ir.imax)
        ir.imax = ir2.imax;

    uinteger_t u;

    u = getMask(ir1.imax);
    ir.imin &= u;
    ir.imax &= u;

    u = getMask(ir2.imax);
    ir.imin &= u;
    ir.imax &= u;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("AndExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange OrExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = ir1.imin;
    if (ir2.imin < ir.imin)
        ir.imin = ir2.imin;

    ir.imax = ir1.imax;
    if (ir2.imax > ir.imax)
        ir.imax = ir2.imax;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("OrExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange XorExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = ir1.imin;
    if (ir2.imin < ir.imin)
        ir.imin = ir2.imin;

    ir.imax = ir1.imax;
    if (ir2.imax > ir.imax)
        ir.imax = ir2.imax;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("XorExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange ShlExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = getMask(ir1.imin) << ir2.imin;
    ir.imax = getMask(ir1.imax) << ir2.imax;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("ShlExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange ShrExp::getIntRange()
{
    if (!e1->type->isunsigned())
        return Expression::getIntRange();

    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = ir1.imin >> ir2.imax;
    ir.imax = ir1.imax >> ir2.imin;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("ShrExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange UshrExp::getIntRange()
{
    IntRange ir;
    IntRange ir1 = e1->getIntRange();
    IntRange ir2 = e2->getIntRange();

    ir.imin = ir1.imin >> ir2.imax;
    ir.imax = ir1.imax >> ir2.imin;

    ir.imin &= type->sizemask();
    ir.imax &= type->sizemask();

//printf("UshrExp: imin = x%llx, imax = x%llx\n", ir.imin, ir.imax);
//e1->dump(0);

    return ir;
}

IntRange CommaExp::getIntRange()
{
    return e2->getIntRange();
}