[Bug c++/91428] Please warn on if constexpr (std::is_constant_evaluated())

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91428

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Wed Aug 28 02:03:48 2019
New Revision: 274981

URL: https://gcc.gnu.org/viewcvs?rev=274981&root=gcc&view=rev
Log:
        PR c++/91428 - warn about std::is_constant_evaluated in if constexpr.
        * cp-tree.h (decl_in_std_namespace_p): Declare.
        * semantics.c (is_std_constant_evaluated_p): New.
        (finish_if_stmt_cond): Warn about "std::is_constant_evaluated ()" in
        an if-constexpr.
        * typeck.c (decl_in_std_namespace_p): No longer static.

        * g++.dg/cpp2a/is-constant-evaluated9.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated9.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/semantics.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog