c++: Redeclaration of implicit operator== [PR94583]

c++: Redeclaration of implicit operator== [PR94583]

My last patch rejected a namespace-scope declaration of the
implicitly-declared friend operator== before the class, but redeclaring it
after the class should be OK.

gcc/cp/ChangeLog
2020-04-28  Jason Merrill  <jason@redhat.com>

	PR c++/94583
	* decl.c (use_eh_spec_block): Check nothrow type after
	DECL_DEFAULTED_FN.
	* pt.c (maybe_instantiate_noexcept): Call synthesize_method for
	DECL_MAYBE_DELETED fns here.
	* decl2.c (mark_used): Not here.
	* method.c (get_defaulted_eh_spec): Reject DECL_MAYBE_DELETED here.