[Bug c++/107461] [12 Regression] ambiguity error for friend with templated constexpr argument

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107461

--- Comment #14 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:eda24f6c12b6d3777ff3bf3656187e695a3e8dc2

commit r12-9110-geda24f6c12b6d3777ff3bf3656187e695a3e8dc2
Author: Patrick Palka <ppalka@redhat.com>
Date:   Sun Feb 5 21:35:33 2023 -0500

    c++: equivalence of non-dependent calls [PR107461]

    After r13-5684-g59e0376f607805 the (pruned) callee of a non-dependent
    CALL_EXPR is a bare FUNCTION_DECL rather than ADDR_EXPR of FUNCTION_DECL.
    This innocent change revealed that cp_tree_equal doesn't first check
    dependence of a CALL_EXPR before treating a FUNCTION_DECL callee as a
    dependent name, which leads to us incorrectly accepting the first two
    testcases below and rejecting the third:

     * In the first testcase, cp_tree_equal incorrectly returns true for
       the two non-dependent CALL_EXPRs f(0) and f(0) (whose CALL_EXPR_FN
       are different FUNCTION_DECLs) which causes us to treat #2 as a
       redeclaration of #1.

     * Same issue in the second testcase, for f<int*>() and f<char>().

     * In the third testcase, cp_tree_equal incorrectly returns true for
       f<int>() and f<void(*)(int)>() which causes us to conflate the two
       dependent specializations A<decltype(f<int>()(U()))> and
       A<decltype(f<void(*)(int)>()(U()))>.

    This patch fixes this by making called_fns_equal treat two callees as
    dependent names only if the overall CALL_EXPRs are dependent, via a new
    convenience function call_expr_dependent_name that is like dependent_name
    but also checks dependence of the overall CALL_EXPR.

            PR c++/107461

    gcc/cp/ChangeLog:

            * cp-tree.h (call_expr_dependent_name): Declare.
            * pt.cc (iterative_hash_template_arg) <case CALL_EXPR>: Use
            call_expr_dependent_name instead of dependent_name.
            * tree.cc (call_expr_dependent_name): Define.
            (called_fns_equal): Adjust to take two CALL_EXPRs instead of
            CALL_EXPR_FNs thereof.  Use call_expr_dependent_name instead
            of dependent_name.
            (cp_tree_equal) <case CALL_EXPR>: Adjust call to called_fns_equal.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/overload5.C: New test.
            * g++.dg/cpp0x/overload5a.C: New test.
            * g++.dg/cpp0x/overload6.C: New test.

    (cherry picked from commit 31924665c86d47af6b1f22a74f594f2e1dc0ed2d)