[Bug c++/54336] New: [c++0x] diagnostics for functions with arg-dependent return types have bad signatures

[luto at mit dot edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54336

             Bug #: 54336
           Summary: [c++0x] diagnostics for functions with arg-dependent
                    return types have bad signatures
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: l...@mit.edu


This code:

template<typename T> auto func(T x) -> decltype(x.method())
{
  static_assert(false, "test");
}

fails to compile with:

decltype_return.cc: In function 'decltype (x.method()) func(T)':
decltype_return.cc:3:3: error: static assertion failed: test
   static_assert(false, "test");
   ^

What's 'decltype (x.method()) func(T)'?  x isn't defined.  'auto func(T x) ->
decltype(x.method())' or even 'decltype (x.method()) func (T x)' would be
better.