https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93698
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:03c344ad180e094140be514a5e7cbaf95b5dcd2e commit r10-8214-g03c344ad180e094140be514a5e7cbaf95b5dcd2e Author: Patrick Palka <ppa...@redhat.com> Date: Fri May 29 14:17:02 2020 -0400 c++: lambdas inside constraints [PR92652] When parsing a constraint-expression, a requires-clause or a requires-expression, we temporarily increment processing_template_decl so that we always obtain template trees which we could later reduce via substitution even when not inside a template. But incrementing processing_template_decl when we're already inside a template has the unintended side effect of shifting up the template parameter levels of a lambda defined inside one of these constructs, which leads to confusion later during substitution into the lambda. This patch fixes this issue by incrementing processing_template_decl during parsing of these constructs only if it is 0. gcc/cp/ChangeLog: PR c++/92652 PR c++/93698 PR c++/94128 * parser.c (cp_parser_requires_clause_expression): Temporarily increment processing_template_decl only if it is 0. (cp_parser_constraint_expression): Likewise. (cp_parser_requires_expression): Likewise. gcc/testsuite/ChangeLog: PR c++/92652 PR c++/93698 PR c++/94128 * g++.dg/cpp2a/concepts-lambda8.C: New test. * g++.dg/cpp2a/concepts-lambda9.C: New test. * g++.dg/cpp2a/concepts-lambda10.C: New test. (cherry picked from commit 020d86db8896f088435830595640e6fc21bc64ad)
