https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106784
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:8a7bcf95a82c3dd68bd4bcfbd8432eb970575bc2 commit r13-2822-g8a7bcf95a82c3dd68bd4bcfbd8432eb970575bc2 Author: Marek Polacek <pola...@redhat.com> Date: Tue Sep 20 15:48:52 2022 -0400 c++: Implement __is_{nothrow_,}convertible [PR106784] To improve compile times, the C++ library could use compiler built-ins rather than implementing std::is_convertible (and _nothrow) as class templates. This patch adds the built-ins. We already have __is_constructible and __is_assignable, and the nothrow forms of those. Microsoft (and clang, for compatibility) also provide an alias called __is_convertible_to. I did not add it, but it would be trivial to do so. I noticed that our __is_assignable doesn't implement the "Access checks are performed as if from a context unrelated to either type" requirement, therefore std::is_assignable / __is_assignable give two different results here: class S { operator int(); friend void g(); // #1 }; void g () { // #1 doesn't matter static_assert(std::is_assignable<int&, S>::value, ""); static_assert(__is_assignable(int&, S), ""); } This is not a problem if __is_assignable is not meant to be used by the users. This patch doesn't make libstdc++ use the new built-ins, but I had to rename a class otherwise its name would clash with the new built-in. PR c++/106784 gcc/c-family/ChangeLog: * c-common.cc (c_common_reswords): Add __is_convertible and __is_nothrow_convertible. * c-common.h (enum rid): Add RID_IS_CONVERTIBLE and RID_IS_NOTHROW_CONVERTIBLE. gcc/cp/ChangeLog: * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_CONVERTIBLE and CPTK_IS_NOTHROW_CONVERTIBLE. * cp-objcp-common.cc (names_builtin_p): Handle RID_IS_CONVERTIBLE RID_IS_NOTHROW_CONVERTIBLE. * cp-tree.h (enum cp_trait_kind): Add CPTK_IS_CONVERTIBLE and CPTK_IS_NOTHROW_CONVERTIBLE. (is_convertible): Declare. (is_nothrow_convertible): Likewise. * cxx-pretty-print.cc (pp_cxx_trait_expression): Handle CPTK_IS_CONVERTIBLE and CPTK_IS_NOTHROW_CONVERTIBLE. * method.cc (is_convertible): New. (is_nothrow_convertible): Likewise. * parser.cc (cp_parser_primary_expression): Handle RID_IS_CONVERTIBLE and RID_IS_NOTHROW_CONVERTIBLE. (cp_parser_trait_expr): Likewise. * semantics.cc (trait_expr_value): Handle CPTK_IS_CONVERTIBLE and CPTK_IS_NOTHROW_CONVERTIBLE. (finish_trait_expr): Likewise. libstdc++-v3/ChangeLog: * include/std/type_traits: Rename __is_nothrow_convertible to __is_nothrow_convertible_lib. * testsuite/20_util/is_nothrow_convertible/value_ext.cc: Likewise. gcc/testsuite/ChangeLog: * g++.dg/ext/has-builtin-1.C: Enhance to test __is_convertible and __is_nothrow_convertible. * g++.dg/ext/is_convertible1.C: New test. * g++.dg/ext/is_convertible2.C: New test. * g++.dg/ext/is_nothrow_convertible1.C: New test. * g++.dg/ext/is_nothrow_convertible2.C: New test.
