[Bug c++/96095] New: decltype((r)) inside of lambda with copy capture gives wrong type

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96095

            Bug ID: 96095
           Summary: decltype((r)) inside of lambda with copy capture gives
                    wrong type
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

Couldn't find a dupe for this one. The example from what is now
[expr.prim.id.unqual]/2 (http://eel.is/c++draft/expr.prim.id.unqual#2) doesn't
have the expected behavior:

template <typename T, typename U>
inline constexpr bool is_same_v = false;

template <typename T>
inline constexpr bool is_same_v<T, T> = true;

void f(float x, float& r) {
    [=] {
        static_assert(is_same_v<decltype(x), float>);
        static_assert(is_same_v<decltype((x)), float const&>);
        static_assert(is_same_v<decltype(r), float&>);
        static_assert(is_same_v<decltype((r)), float const&>); // error
    }();
}

gcc reports decltype((r)) to be float&, not float const& here.