From a915c29a7d63ccb88cfded75ba1c8c4919845e98 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 9 Mar 2023 17:01:48 -0500
Subject: [PATCH] c++: constrained lambda error-recovery [PR108972]

Better not to ICE after various valid errors.

	PR c++/108972

gcc/cp/ChangeLog:

	* lambda.cc (compare_lambda_template_head): Check more
	for error_mark_node.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-lambda3.C: Run at lower std levels,
	but expect errors.
---
 gcc/cp/lambda.cc                              | 4 ++++
 gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/lambda.cc b/gcc/cp/lambda.cc
index c752622816d..212990a21bf 100644
--- a/gcc/cp/lambda.cc
+++ b/gcc/cp/lambda.cc
@@ -1537,6 +1537,8 @@ compare_lambda_template_head (tree tmpl_a, tree tmpl_b)
 	  if (parm_a == error_mark_node)
 	    return false;
 	  parm_a = TREE_VALUE (parm_a);
+	  if (parm_a == error_mark_node)
+	    return false;
 	  if (DECL_VIRTUAL_P (parm_a))
 	    parm_a = NULL_TREE;
 	}
@@ -1548,6 +1550,8 @@ compare_lambda_template_head (tree tmpl_a, tree tmpl_b)
 	  if (parm_b == error_mark_node)
 	    return false;
 	  parm_b = TREE_VALUE (parm_b);
+	  if (parm_b == error_mark_node)
+	    return false;
 	  if (DECL_VIRTUAL_P (parm_b))
 	    parm_b = NULL_TREE;
 	}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C
index 291e451ca1a..b18e6b62aa4 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C
@@ -1,4 +1,5 @@
-// { dg-do run { target c++20 } }
+// { dg-do run }
+// { dg-excess-errors "" { target { ! concepts } } } (PR108972)
 
 template<typename T>
 concept C1 = __is_same_as(T, int)
@@ -61,4 +62,3 @@ int main(int, char**)
 
   return 0;
 }
-
-- 
2.11.4.GIT