[Bug c++/78301] noexcept() operator rejects sibling method call without object

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78301

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And std::declval<a*>()->inner() doesn't work either:

ne.cc:5:59: error: invalid use of incomplete type ‘struct a’
  void outer() const noexcept( noexcept( std::declval<a*>()->inner() ) ) {
                                                           ^~
ne.cc:3:8: note: definition of ‘struct a’ is not complete until the closing
brace
 struct a {
        ^

Which is PR 66256.