http://d.puremagic.com/issues/show_bug.cgi?id=10498

           Summary: `__traits(compiles, ...)` affect program behaviour
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: verylonglogin.reg@gmail.com


--- Comment #0 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2013-06-29 11:50:51 MSD ---
`{ T; }` delegate makes `static assert` fail:
---
template triggerIssue()
{ enum triggerIssue = __traits(compiles, { T; }); }

template PackedGenericTuple(Args...)
{
    alias Args Tuple;
    enum e = triggerIssue!();
}

struct S { }

template T()
{
    alias T = PackedGenericTuple!S;
}

void main()
{
    alias t = T!();
    static assert(is(t.Tuple[0])); // Fails
}
---

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Denis Shelomovskij <verylonglogin.reg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |regression


--- Comment #1 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2013-06-29 11:56:14 MSD ---
Another situation:
---
template triggerIssue(A...)
{ enum triggerIssue = __traits(compiles, { auto a = A[0]; }); }

template PackedGenericTuple(Args...)
{
    alias Args Tuple;
    enum e = triggerIssue!Args;
}

template T()
{
    struct S{} // The fact `S` is in `T` causes the problem
    alias T = PackedGenericTuple!S;
}

void main()
{
    alias t = T!();
    static assert(is(t.Tuple[0]));
}
---

The second one is reduced (no sure if correct) from regression failure.

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #2 from Kenji Hara <k.hara.pg@gmail.com> 2013-06-30 02:30:16 PDT ---
Compiler fix for the first case. https://github.com/D-Programming-Language/dmd/pull/2280

I'm not sure the second case is really a regression. If not, it should be filed as a separate issue.

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--- Comment #3 from Kenji Hara <k.hara.pg@gmail.com> 2013-06-30 03:28:36 PDT ---
(In reply to comment #2)
> Compiler fix for the first case. https://github.com/D-Programming-Language/dmd/pull/2280
> 
> I'm not sure the second case is really a regression. If not, it should be filed as a separate issue.

OK, indeed the second case would have the same root cause with the first. I updated the PR to fix the both cases.

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--- Comment #4 from github-bugzilla@puremagic.com 2013-07-08 03:54:15 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/abbbbc419d0c792a04f715fcd8c60831764dc294 fix Issue 10498 - `__traits(compiles, ...)` affect program behaviour

https://github.com/D-Programming-Language/dmd/commit/6c6765783609e06ef9634f16f6d6a2035da8ec8f Merge pull request #2280 from 9rnsr/fix10498

[REG2.061] Issue 10498 - `__traits(compiles, ...)` affect program behaviour

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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