https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94252
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:a7ea3d2ced786c4544fa625f34f515d89ed074fe commit r10-7441-ga7ea3d2ced786c4544fa625f34f515d89ed074fe Author: Patrick Palka <ppa...@redhat.com> Date: Sat Mar 28 08:56:59 2020 -0400 c++: requires-expression outside of a template is misevaluated [PR94252] This PR shows that a REQUIRES_EXPR outside of a template can sometimes be misevaluated. This happens because the evaluation routine tsubst_requires_expr (and diagnose_requires_expr) assumes the REQUIRES_EXPR's subtrees are templated trees and that therefore it's safe to call tsubst_expr on them. But this assumption isn't valid when we've parsed a REQUIRES_EXPR outside of a template context. In order to make this assumption valid here, this patch sets processing_template_decl to non-zero before parsing the body of a REQUIRES_EXPR so that its subtrees are indeed always templated trees. gcc/cp/ChangeLog: PR c++/94252 * constraint.cc (tsubst_compound_requirement): Always suppress errors from type_deducible_p and expression_convertible_p, as they're not substitution errors. (diagnose_atomic_constraint) <case INTEGER_CST>: Remove this case so that we diagnose INTEGER_CST expressions of non-bool type via the default case. * cp-gimplify.c (cp_genericize_r) <case REQUIRES_EXPR>: New case. * parser.c (cp_parser_requires_expression): Always parse the requirement body as if we're processing a template, by temporarily incrementing processing_template_decl. Afterwards, if we're not actually in a template context, perform semantic processing to diagnose any invalid types and expressions. * pt.c (tsubst_copy_and_build) <case REQUIRES_EXPR>: Remove dead code. * semantics.c (finish_static_assert): Explain an assertion failure when the condition is a REQUIRES_EXPR like we do when it is a concept check. gcc/testsuite/ChangeLog: PR c++/94252 * g++.dg/concepts/diagnostic7.C: New test. * g++.dg/concepts/pr94252.C: New test. * g++.dg/cpp2a/concepts-requires18.C: Adjust to expect an additional diagnostic.
