[Issue 4389] ICE(constfold.c, expression.c), or wrong code: string~=dchar in CTFE

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4389



--- Comment #6 from Don <clugdbug at yahoo.com.au> 2011-01-19 23:59:47 PST ---
Fails on D1 because dchar, wchar implicitly convert to char, even if they don't
fit.

PATCH: expression.c, CatAssignExp::semantic(), line 8574. The two 'else'
clauses need to be swapped,
so that we check for an array~char before we check for implicit conversion.


    {   // Append array
        e2 = e2->castTo(sc, e1->type);
        type = e1->type;
        e = this;
    }
----------- SWAP THIS SECTION WITH THE NEXT ONE
    else if ((tb1->ty == Tarray) &&
        e2->implicitConvTo(tb1next)
       )
    {   // Append element
        e2 = e2->castTo(sc, tb1next);
        type = e1->type;
        e = this;
    }
-------
    else if (tb1->ty == Tarray &&
        (tb1next->ty == Tchar || tb1next->ty == Twchar) &&
        e2->implicitConvTo(Type::tdchar)
       )
    {   // Append dchar to char[] or wchar[]
        e2 = e2->castTo(sc, Type::tdchar);
        type = e1->type;
        e = this;

        /* Do not allow appending wchar to char[] because if wchar happens
         * to be a surrogate pair, nothing good can result.
         */
    }
-----------
    else
    {
        if (tb1 != Type::terror && tb2 != Type::terror)
            error("cannot append type %s to type %s", tb2->toChars(),
tb1->toChars());
        e = new ErrorExp();
    }

ALTERNATE PATCH:
Incidentally, if dchar->char is disallowed, all DMD tests still pass. But this
would probably cause existing valid code to break, so probably the first
solution is better.

mtype.c,  line 1570, MATCH TypeBasic::implicitConvTo(Type *to)
+       if ((ty == Tdchar || ty == Twchar) && to->ty == Tchar)
+            return MATCHnomatch;
+       if (ty == Tdchar && to->ty == Twchar)
+           return MATCHnomatch;
    }
    else if (flags & TFLAGSfloating)
    {
        // Disallow implicit conversion of floating point to integer
        if (tob->flags & TFLAGSintegral)
            return MATCHnomatch;

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