[Bug c++/97297] typename wrongly required in out-of-class member function definitions

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97297

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:85307b4e938d42201d6c232f5d9259f91133a303

commit r11-3688-g85307b4e938d42201d6c232f5d9259f91133a303
Author: Marek Polacek <polacek@redhat.com>
Date:   Mon Oct 5 17:48:19 2020 -0400

    c++: typename in out-of-class member function definitions [PR97297]

    I was notified that our P0634R3 (Down with typename) implementation has
    a flaw: when we have an out-of-class member function definition, we
    still required 'typename' for its parameters.  For example here:

      template <typename T> struct S {
        int simple(T::type);
      };
      template <typename T>
      int S<T>::simple(/* typename */T::type) { return 0; }

    the 'typename' isn't necessary per [temp.res]/5.2.4.  We have a qualified
    name here ("S<T>::simple") so we know it's already been declared so we
    can look it up to see if it's a function template or a variable
    template.

    In this case, the P0634R3 code in cp_parser_direct_declarator wasn't
    looking into uninstantiated templates and didn't find the member
    function 'simple' -- cp_parser_lookup_name returned a SCOPE_REF which
    means that the qualifying scope was dependent.  With this fix, we find
    the BASELINK for 'simple', don't clear CP_PARSER_FLAGS_TYPENAME_OPTIONAL
    from the flags, and the typename is implicitly assumed.

    gcc/cp/ChangeLog:

            PR c++/97297
            * parser.c (cp_parser_direct_declarator): When checking if a
            name is a function template declaration for the P0634R3 case,
            look in uninstantiated templates too.

    gcc/testsuite/ChangeLog:

            PR c++/97297
            * g++.dg/cpp2a/typename18.C: New test.