gcc/testsuite/g++.dg/cpp0x/pr33839.C

// { dg-options -std=c++0x }
template<int> struct A;

void foo()
{
  __decltype A<0>; // { dg-error "invalid declarator|expected" }
  __decltype (A<0>); // { dg-error "must be an expression" }
}