http://d.puremagic.com/issues/show_bug.cgi?id=6602

           Summary: Invalid template instantiations »leaked« by
                    is(typeof())/__traits(compiles, …)/Type::trySemantic
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Mac OS X
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: code@klickverbot.at


--- Comment #0 from klickverbot <code@klickverbot.at> 2011-09-04 21:29:25 PDT ---
Okay, turns out that the »collateral regression« the fix for bug 6220 caused in
my code ([1]) really is a fundamental problem with how DMD handles template
instantiations in the face of error gagging, in this case because is(typeof())
is used (same for __traits(compiles, …)):

---
template A(T) {
  B!(T).Result result;
}

template B(U) {
  static assert(is(U == int));
  alias bool Result;
}

pragma(msg, is(typeof(A!short)));
---

The static assert in B!() should just cause is(typeof()) to evaluate to false,
but B!short is also added to the module member list, causing compilation to
fail because of !is(short == int).

I am working on a fix, but need an issue number to reference.


[1] https://github.com/D-Programming-Language/dmd/commit/60f4ec88decbcd00e765ab392bf8be8f526ed1ab#commitcomment-535706

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--- Comment #1 from klickverbot <code@klickverbot.at> 2011-09-04 22:25:58 PDT ---
Wish I had discovered that earlier, not just from a bugzilla reference in the DMD source after I tracked the problem down: A very similar bug has already been reported, issue 4302. However, the fix proposed there (which got committed in e66a3a5) only hides the issue for static if conditionals, while it can also appear if trySemantic() is attempted outside them, see above.

I think the correct solution for the problem is to remove the template instance from the member list of the enclosing scope again if instantiation failed while errors were gagged:

https://github.com/D-Programming-Language/dmd/pull/364

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klickverbot <code@klickverbot.at> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


--- Comment #2 from klickverbot <code@klickverbot.at> 2011-09-04 22:52:33 PDT ---
(I realize that A!short would never have a type, even if B!short could be instantiated, but this is not important here.)

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klickverbot <code@klickverbot.at> changed:

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


--- Comment #3 from klickverbot <code@klickverbot.at> 2011-09-05 14:25:16 PDT ---
https://github.com/D-Programming-Language/dmd/commit/3da0a36698b9cc424dbc8f6e7b2786768ae50f84

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klickverbot <code@klickverbot.at> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |schveiguy@yahoo.com


--- Comment #4 from klickverbot <code@klickverbot.at> 2011-09-05 14:31:14 PDT ---
*** Issue 6385 has been marked as a duplicate of this issue. ***

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla@digitalmars.com


--- Comment #5 from Walter Bright <bugzilla@digitalmars.com> 2011-09-05 16:50:52 PDT ---
https://github.com/D-Programming-Language/dmd/commit/3da0a36698b9cc424dbc8f6e7b2786768ae50f84

https://github.com/D-Programming-Language/dmd/commit/5c236d7583f05d10aa55126e16abd00b6e4ff458

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