https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101725
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:be45bc283e1821fff463d03d5115cd4db634ed84 commit r11-8853-gbe45bc283e1821fff463d03d5115cd4db634ed84 Author: Patrick Palka <ppa...@redhat.com> Date: Wed Aug 11 16:53:53 2021 -0400 c++: parameterized requires-expr as default argument [PR101725] Here we're rejecting the default template argument requires (T t) { x(t); } because we consider the 't' in the requirement to be a local variable (according to local_variable_p), and we generally forbid local variables from appearing inside default arguments. We can perhaps fix this by giving special treatment to parameters introduced by requires-expressions, but DR 2082 relaxed the restriction about local variables appearing within default arguments to permit them inside unevaluated operands thereof. So this patch just implements DR 2082 which also fixes this PR since a requires-expression is an unevaluated context. PR c++/101725 DR 2082 gcc/cp/ChangeLog: * cp-tree.h (unevaluated_p): Return true for REQUIRES_EXPR. * decl.c (local_variable_p_walkfn): Don't walk into unevaluated operands. * parser.c (cp_parser_primary_expression) <case CPP_NAME>: Never reject uses of local variables in unevaluated contexts. * tree.c (cp_walk_subtrees) <case REQUIRES_EXPR>: Increment cp_unevaluated_operand. Use cp_walk_tree directly instead of WALK_SUBTREE to avoid the goto. Use REQUIRES_EXPR_REQS instead of TREE_OPERAND directly. gcc/testsuite/ChangeLog: * g++.dg/DRs/dr2082.C: New test. * g++.dg/cpp2a/concepts-uneval4.C: New test. (cherry picked from commit 9707d2e5dbb92d2bc990c922461a5a16ae652319)
