Index: testsuite/g++.dg/other/dtor1.C
===================================================================
--- testsuite/g++.dg/other/dtor1.C	(revision 0)
+++ testsuite/g++.dg/other/dtor1.C	(revision 0)
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+// PR C++/30303
+// This used to ICE because we did not return NULL
+// in grokfndecl when an error happened.
+
+struct Ifoo
+{
+virtual ~Ifoo(){}
+};
+struct foo : Ifoo
+{
+ foo(){};
+};
+foo::~foo() // { dg-error "definition of implicitly-declared" }
+{
+delete this;
+}
Index: testsuite/g++.dg/other/ctor1.C
===================================================================
--- testsuite/g++.dg/other/ctor1.C	(revision 0)
+++ testsuite/g++.dg/other/ctor1.C	(revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+// PR C++/30303
+// This used to ICE because we did not return NULL
+// in grokfndecl when an error happened.
+
+class A
+{
+  int i;
+};
+
+A::A() { A(); } /* { dg-error "definition of implicitly-declared" } */
Index: testsuite/g++.dg/other/ctor2.C
===================================================================
--- testsuite/g++.dg/other/ctor2.C	(revision 0)
+++ testsuite/g++.dg/other/ctor2.C	(revision 0)
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+// PR C++/30303
+// This used to ICE because we did not return NULL
+// in grokfndecl when an error happened.
+
+
+class A
+{
+  int i;
+};
+
+void foo()
+{
+  A();
+}
+
+A::A() {} /* { dg-error "definition of implicitly-declared" } */
Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 129297)
+++ cp/decl.c	(working copy)
@@ -6577,7 +6577,10 @@ grokfndecl (tree ctype,
 	       XXX Isn't this done in start_function, too?  */
 	    revert_static_member_fn (decl);
 	  if (DECL_ARTIFICIAL (old_decl))
-	    error ("definition of implicitly-declared %qD", old_decl);
+	    {
+	      error ("definition of implicitly-declared %qD", old_decl);
+	      return NULL_TREE;
+	    }
 
 	  /* Since we've smashed OLD_DECL to its
 	     DECL_TEMPLATE_RESULT, we must do the same to DECL.  */