I think g++ incorrectly rejects the following code when compiled with
-std=c++0x:

  template <typename> struct X {};
  X<decltype(1 > 2)> x;
    // t.cpp:2: error: template argument 1 is invalid
    // t.cpp:2: error: invalid type in declaration before ‘;’ token

For comparison, here is very similar code that is accepted:

  template <int> struct Y {};
  Y<sizeof(1 > 2)> y;

Hence, I suspect it is a problem with decltype.


-- 
           Summary: [c++0x] misinterpreted closing angle bracket in decltype
                    operand
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gcc-bugzilla at contacts dot eelis dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37875