PR c++/96437: ICE-on-invalid-code error recovery.

This patch fixes PR c++/96437 which is an ICE-on-invalid-code regression
affecting mainline.

2022-03-08  Roger Sayle  <roger@nextmovesoftware.com>

gcc/cp/ChangeLog
	PR c++/96437
	* parser.cc (synthesize_implicit_template_parm): Check that
	TREE_VALUE (new_parm) isn't error_mark_node before setting its
	DECL_VIRTUAL_P.

gcc/testsuite/ChangeLog
	PR c++/96437
	* g++.dg/cpp2a/pr96437.C: New test case.

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index dc2d39a..9153c74 100644 (file)
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -48218,7 +48218,8 @@ synthesize_implicit_template_parm  (cp_parser *parser, tree constr)
      function template is equivalent to an explicit template.
 
      Note that DECL_ARTIFICIAL is used elsewhere for template parameters.  */
-  DECL_VIRTUAL_P (TREE_VALUE (new_parm)) = true;
+  if (TREE_VALUE (new_parm) != error_mark_node)
+    DECL_VIRTUAL_P (TREE_VALUE (new_parm)) = true;
 
   // Chain the new parameter to the list of implicit parameters.
   if (parser->implicit_template_parms)

diff --git a/gcc/testsuite/g++.dg/cpp2a/pr96437.C b/gcc/testsuite/g++.dg/cpp2a/pr96437.C
new file mode 100644 (file)
index 0000000..79d481e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/pr96437.C
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-excess-errors "" } */
+
+template <()> void A(auto){}