[Bug c++/101460] Useless cascade of overload resolution errors for invalid expression

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101460

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

https://gcc.gnu.org/g:a8de832470f78a40a0e2c8de866a471bf74bf0ab

commit r12-3234-ga8de832470f78a40a0e2c8de866a471bf74bf0ab
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Aug 30 09:44:28 2021 -0400

    c++: fold function template args sooner [PR101460]

    As discussed in the PR, we were giving a lot of unnecessary errors for this
    testcase because we didn't try to do constant evaluation until
    convert_nontype_argument, which happens for each of the candidates.  But
    when looking at a template-id as the function operand of a call, we can try
    to fold arguments before we get into overload resolution.

            PR c++/101460

    gcc/cp/ChangeLog:

            * cp-tree.h (cxx_constant_value_sfinae): Declare.
            * constexpr.c (cxx_constant_value_sfinae): New.
            * pt.c (fold_targs_r, maybe_fold_fn_template_args): New.
            (tsubst_copy_and_build) [CALL_EXPR]: Call
            maybe_fold_fn_template_args.

    gcc/testsuite/ChangeLog:

            * g++.dg/template/explicit-args6.C: New test.