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digitalmars.D.bugs - [Issue 8257] New: __traits(compiles) gives compile error

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8257

           Summary: __traits(compiles) gives compile error
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: wfunction hotmail.com


--- Comment #0 from wfunction hotmail.com 2012-06-16 19:11:34 PDT ---
struct S { static void g() { } }
    auto f(string m)() { return &__traits(getMember, S.init, m); }

    // Error: delegates are only for non-static functions
    static if (__traits(compiles, f!"g"())) { }


Marked as critical since there's no real workaround (that I'm aware of)...

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Jun 16 2012
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8257


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au


--- Comment #1 from Don <clugdbug yahoo.com.au> 2012-10-19 04:14:25 PDT ---
The error is not coming from __traits(compiles), it happens while generating
the obj file.
If you compile with dmd -c -o-
then no error occurs.

The error message itself should I think be regarded as an internal compiler
error.
Here's the root cause.

struct S { static void g() { } static int w;}
void main()
{
     S s;
     auto k = &s.g;
     pragma(msg, typeof(&s.g));
}
This compiles with -c -o-

According to the pragma, &s.g is a delegate. But, since g is a static function,
it cannot be a valid delegate. The error is detected only at the glue layer.

I believe that &s.g should be a function pointer, and s should be ignored,
since already:
int *x = &s.w; // accepted, s is ignored
s.g();         // accepted, s is ignored.

This would mean the __traits in the original code would continue to return
true, but the function f!"g"() would actually be valid and would return a
function pointer, not a delegate.

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Oct 19 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8257



--- Comment #2 from github-bugzilla puremagic.com 2012-10-20 20:27:21 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/95d00b2f0ae25d74e0091d17d5537232b8339fd4
Fix issue 8257 __traits(compiles) gives compile error

& v.staticfunc is a function pointer, not a delegate.
Change it into (v, &typeof(v).staticfunc)

https://github.com/D-Programming-Language/dmd/commit/349edf2f8fa130d49ce2361aad2ffa03f6cd55a7
Merge pull request #1194 from donc/bug8257_delegate_nonstatic

8257 x.staticfunc() is a function pointer, not a delegate

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Oct 20 2012
prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
            Version|D2                          |D1 & D2
         Resolution|                            |FIXED


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