[Bug c++/50034] [4.7 regression] Overload selection failure within class template

["jason at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50034

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
           Keywords|                            |rejects-valid
   Last reconfirmed|                            |2011-08-12
                 CC|jason at redhat dot com     |jason at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1
            Summary|Overload selection failure  |[4.7 regression] Overload
                   |within class template       |selection failure within
                   |                            |class template
   Target Milestone|---                         |4.7.0

--- Comment #1 from Jason Merrill <jason at gcc dot gnu.org> 2011-08-12 04:50:06 UTC ---
In this testcase, you're calling selector with an 'abstract' argument.  5.2.2/7
says,

The lvalue-to-rvalue (4.1), array-to-pointer (4.2), and function-to-pointer
(4.3) standard conversions are performed on the argument expression.

4.1/2 says,

When an lvalue-to-rvalue conversion occurs in an unevaluated operand or a
subexpression thereof (Clause 5) the value contained in the referenced object
is not accessed. Otherwise, if the glvalue has a class type, the conversion
copy-initializes a temporary of type T from the glvalue and the result of the
conversion is a prvalue for the temporary.

Hmm, having different semantics for lvalue-rvalue conversion depending on
whether the expression is evaluated is surprising, but that does seem to be
what the standard says.  Alrighty then.