On 6/2/26 2:57 PM, Patrick Palka wrote:
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
OK for trunk/16?
-- >8 --
Here the nonsensical constraint-expression f() == 42 isn't getting
rejected ahead of time ultimately because we pass no_toplevel_fold_p=true
to cp_parser_binary_expression which makes it use build_min instead of
build_x_binary_op to avoid undesirable folding/canonicalization for sake
of OpenMP for loop parsing (r145014). But this certainly doesn't happen
during templated parsing, and constraint-expressions are always
templated, so we might as well pass no_toplevel_fold_p=false here.
In this testcase the concept is never checked for satisfaction. In the
testcase in the PR there is a similarly nonsensical concept that is
used, and is diagnosed at that point. So this patch is about diagnosing
more IFNDR code, yes?
With that clarification to the commit message, OK for trunk but not 16.
PR c++/125490
gcc/cp/ChangeLog:
that is used
* parser.cc (cp_parser_constraint_expression): Pass
no_toplevel_fold_p=false instead of =true to
cp_parser_binary_expression.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-pr125490.C: New test.
---
gcc/cp/parser.cc | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-pr125490.C | 10 ++++++++++
2 files changed, 11 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr125490.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index b5c8c62118cc..c1797191b833 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -34761,7 +34761,7 @@ cp_parser_constraint_expression (cp_parser *parser)
{
processing_constraint_expression_sentinel parsing_constraint;
++processing_template_decl;
- cp_expr expr = cp_parser_binary_expression (parser, false, true,
+ cp_expr expr = cp_parser_binary_expression (parser, false, false,
PREC_NOT_OPERATOR, NULL);
--processing_template_decl;
if (check_for_bare_parameter_packs (expr))
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-pr125490.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-pr125490.C
new file mode 100644
index 000000000000..a33416b232d1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-pr125490.C
@@ -0,0 +1,10 @@
+// PR c++/125490
+// { dg-do compile { target c++20 } }
+
+void f();
+
+template<class T>
+concept C = f() == 42; // { dg-error "invalid operands" }
+
+template<class T>
+concept D = requires { requires f() == 42; }; // { dg-error "invalid operands"
}
