[Bug c++/97399] [9/10/11 Regression] g++ 9.3 cannot compile SFINAE code with separated declaration and definition, g++ 7.3 compiles

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97399

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:a8cef3cba6945730c69e15dcdad726e74b50fe58

commit r11-6878-ga8cef3cba6945730c69e15dcdad726e74b50fe58
Author: Patrick Palka <ppalka@redhat.com>
Date:   Sat Jan 23 00:24:17 2021 -0500

    c++: 'this' injection and static member functions [PR97399]

    In the testcase pr97399.C below, finish_qualified_id_expr at parse time
    adds an implicit 'this->' to the expression tmp::integral<T> (because
    it's type-dependent, and also current_class_ptr is set at this point)
    within the trailing return type.  Later when substituting into this
    trailing return type we crash because we can't resolve the 'this', since
    tsubst_function_type does inject_this_parm only for non-static member
    functions, which tmp::func is not.

    This patch fixes this issue by removing the type-dependence check
    in finish_qualified_id_expr added by r9-5972, and instead relaxes
    shared_member_p to handle dependent USING_DECLs:

    > I think I was wrong in my assertion around Alex's patch that
    > shared_member_p should abort on a dependent USING_DECL; it now seems
    > appropriate for it to return false if we don't know, we just need to
    > adjust the comment to say that.

    And when parsing a friend function declaration, we shouldn't be setting
    current_class_ptr at all, so this patch additionally suppresses
    inject_this_parm in this case.

    Finally, the self-contained change to cp_parser_init_declarator is so
    that we properly communicate static-ness to cp_parser_direct_declarator
    when parsing a member function template.  This lets us reject the
    explicit use of 'this' in the testcase this2.C below.

    gcc/cp/ChangeLog:

            PR c++/97399
            * cp-tree.h (shared_member_p): Adjust declaration.
            * parser.c (cp_parser_init_declarator): If the storage class
            specifier is sc_static, pass true for static_p to
            cp_parser_declarator.
            (cp_parser_direct_declarator): Don't do inject_this_parm when
            the declarator is a friend.
            * search.c (shared_member_p): Change return type to bool and
            adjust function body accordingly.  Return false for a dependent
            USING_DECL instead of aborting.
            * semantics.c (finish_qualified_id_expr): Rely on shared_member_p
            even when type-dependent.

    gcc/testsuite/ChangeLog:

            PR c++/88548
            PR c++/97399
            * g++.dg/cpp0x/this2.C: New test.
            * g++.dg/template/pr97399.C: New test.