[Bug c++/104620] FAIL: g++.dg/cpp23/consteval-if2.C -std=gnu++20 (test for errors)

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104620

--- Comment #9 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:647537adefb34041cc2d44585252fd765cc0daae

commit r12-7802-g647537adefb34041cc2d44585252fd765cc0daae
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Mar 24 11:42:31 2022 -0400

    c++: missing SFINAE for non-constant consteval calls [PR104620]

    Here we weren't respecting SFINAE when evaluating a call to a consteval
    function, which caused us to reject the new testcase below.  This patch
    fixes this by making build_over_call use the SFINAE-friendly version of
    cxx_constant_value.

    This change causes us to no longer diagnose ahead of time a couple of
    non-constant non-dependent consteval calls in consteval-if2.C with
    -fchecking=2.  These errors were apparently coming from the call to
    fold_non_dependent_expr in build_non_dependent_expr (for the RHS of the +=)
    despite complain=tf_none being passed.  Now that build_over_call respects
    the value of complain during constant evaluation of a consteval call,
    the errors are gone.

    That the errors are also gone without -fchecking=2 is a regression caused
    by r12-7264-gc19f317a78c0e4 and is the subject of PR104620.  As described
    in comment #5, I think it's basically an accident that we were diagnosing
    these two calls correctly before r12-7264, so perhaps we can live without
    these errors for GCC 12.  Thus this patch just XFAILs the two tests.

            PR c++/104620

    gcc/cp/ChangeLog:

            * call.cc (build_over_call): Use cxx_constant_value_sfinae
            instead of cxx_constant_value to evaluate a consteval call.
            * constexpr.cc (cxx_constant_value_sfinae): Add decl parameter
            and pass it to cxx_eval_outermost_constant_expr.
            * cp-tree.h (cxx_constant_value_sfinae): Add decl parameter.
            * pt.cc (fold_targs_r): Pass NULL_TREE as decl parameter to
            cxx_constant_value_sfinae.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp23/consteval-if2.C: XFAIL two dg-error tests where
            the argument to the non-constant non-dependent consteval call is
            wrapped by NON_DEPENDENT_EXPR.
            * g++.dg/cpp2a/consteval30.C: New test.