• d-bugmail puremagic.com (28/28) Oct 07 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6784
• d-bugmail puremagic.com (26/26) Jan 31 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6784
• d-bugmail puremagic.com (10/10) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6784
• d-bugmail puremagic.com (21/21) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=6784

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6784

           Summary: Compile-time constant assigned with a runtime value
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



This program compiles with no errors (DMD 2.056head), but I think it's wrong
because the compile-time constant y gets assigned with a runtime value:


struct Foo {
    immutable uint x;
    void foo() {
        enum uint y = x;
    }
}
void main(string[] args) {
    auto f = Foo(args.length);
}

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6784


yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yebblies gmail.com
           Platform|x86                         |All
            Version|D2                          |D1 & D2
         AssignedTo|nobody puremagic.com        |clugdbug yahoo.com.au
         OS/Version|Windows                     |All



Related to Issue 2414.

What differs here is that
enum uint y = x

Is translated to 
enum uint y = this.x

And DotIdExp::optimize does not turn this into a constant value, and there is
no error when it fails when called with result & WANTinterpret.

Unfortunately adding an error causes problems with other code, presumably
because DotIdExp::optimize is use from other places like CallExp::optimize that
expect it to just try and finish without errors.

Reassigning to Don as he fixed 2414 and understands the
constfolding/interpreter code a lot better than I do.

Probably applies to D1/const variables too.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6784




The error message should only happen when result & WANTinterpret.


aren't converted into function calls.
Rather than add another hack for this, it's probably better to wait for bug
5590 to be pulled in.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6784




FWIW, this patch in optimize.c, DotVarExp::optimize() fixes the bug. But, the
exclusion of TOKassocarrayliteral is just a hack.


    if (e && e->op == TOKstructliteral)
    {   StructLiteralExp *sle = (StructLiteralExp *)e;
        VarDeclaration *vf = var->isVarDeclaration();
        if (vf)
        {
            Expression *e = sle->getField(type, vf->offset);
            if (e && e != EXP_CANT_INTERPRET)
                return e;
        }
    }
+   else if (result & WANTinterpret && (!e || e->op != TOKassocarrayliteral))
+        error("%s cannot be evaluated at compile time", e1->toChars());

    return this;
}

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