[Bug c++/81270] [concepts] ill-formed code with a constrained variable declaration with multiple declarators with different deduced types not rejected

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81270

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-10-15
     Ever confirmed|0                           |1
      Known to fail|                            |10.0

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Still accepted by current trunk.

Also accepted when modernised to C++2a syntax:

template<typename> concept C = true;
C auto v1 = 1, v2 = nullptr;  // Ill-formed.
// Following code to demonstrate that the types of v1 and v2 are deduced
// to different types.
template<typename, typename> struct is_same {
  static constexpr bool value = false;
};
template<typename T> struct is_same<T,T> {
  static constexpr bool value = true;
};
static_assert(is_same<decltype(v1),int>::value);
static_assert(is_same<decltype(v2),decltype(nullptr)>::value);