From f7272c8a038847cf67e888828e58fc0e00d1f5d5 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Thu, 21 May 2020 10:27:11 -0400
Subject: [PATCH] c++: Improve error-recovery for parms.

If a parameter is erroneous, we currently drop it, leading to "too many
arguments" errors later.  Treating the function as (...) avoids those
errors.

gcc/cp/ChangeLog:

	* decl.c (grokparms): Return NULL_TREE if any parms were erroneous.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/error33.C: Adjust.
---
 gcc/cp/decl.c                        | 18 +++++++++++++-----
 gcc/testsuite/g++.dg/parse/error33.C |  4 ++--
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 024ddc88a4c..a389579ee52 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13961,7 +13961,10 @@ grokparms (tree parmlist, tree *parms)
 	break;
 
       if (! decl || TREE_TYPE (decl) == error_mark_node)
-	continue;
+	{
+	  any_error = 1;
+	  continue;
+	}
 
       type = TREE_TYPE (decl);
       if (VOID_TYPE_P (type))
@@ -14014,7 +14017,8 @@ grokparms (tree parmlist, tree *parms)
 	      TREE_TYPE (decl) = type;
 	    }
 	  else if (abstract_virtuals_error (decl, type))
-	    any_error = 1;  /* Seems like a good idea.  */
+	    /* Ignore any default argument.  */
+	    init = NULL_TREE;
 	  else if (cxx_dialect < cxx17 && INDIRECT_TYPE_P (type))
 	    {
 	      /* Before C++17 DR 393:
@@ -14043,9 +14047,7 @@ grokparms (tree parmlist, tree *parms)
 			 decl, t);
 	    }
 
-	  if (any_error)
-	    init = NULL_TREE;
-	  else if (init && !processing_template_decl)
+	  if (init && !processing_template_decl)
 	    init = check_default_argument (decl, init, tf_warning_or_error);
 	}
 
@@ -14058,6 +14060,12 @@ grokparms (tree parmlist, tree *parms)
   if (parm)
     result = chainon (result, void_list_node);
   *parms = decls;
+  if (any_error)
+    result = NULL_TREE;
+
+  if (any_error)
+    /* We had parm errors, recover by giving the function (...) type.  */
+    result = NULL_TREE;
 
   return result;
 }
diff --git a/gcc/testsuite/g++.dg/parse/error33.C b/gcc/testsuite/g++.dg/parse/error33.C
index 0d25386a879..61b0cc3f2dc 100644
--- a/gcc/testsuite/g++.dg/parse/error33.C
+++ b/gcc/testsuite/g++.dg/parse/error33.C
@@ -8,9 +8,9 @@ struct A
 
 typedef void (A::T)(); /* { dg-error "15:typedef name may not be a nested" } */
 
-void bar(T); /* { dg-message "note: declared here" } */
+void bar(T);
 
 void baz()
 {
-  bar(&A::foo); /* { dg-error "too many arguments" } */
+  bar(&A::foo);
 }
-- 
2.30.2