https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52597
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed by r197131
re PR c++/52597 ([C++11] confusing diagnostics for invalid use of
non-static member function in decltype)
PR c++/52597
* typeck.c (invalid_nonstatic_memfn_p): Use get_first_fn. Take tree.
* semantics.c (finish_decltype_type): Check it before type_unknown_p.
* cp-tree.h: Adjust prototype.
