diagnose export of incomplete type

R=ken
OCL=17253
CL=17253

src/cmd/gc/export.c

@@ -125,6 +125,13 @@ dumpexporttype(Sym *s)
 	Bprint(bout, "\t");
 	if(s->export != 0)
 		Bprint(bout, "export ");
+	switch (s->otype->etype) {
+	case TFORW:
+	case TFORWSTRUCT:
+	case TFORWINTER:
+		yyerror("export of incomplete type %T", s->otype);
+		return;
+	}
 	Bprint(bout, "type %lS %l#T\n",  s, s->otype);
 }
 

test/export.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// errchk $G $D/$F.go
+
+package main
+
+export type A struct		// ERROR "incomplete"
+export type B interface	// ERROR "incomplete"
+
+export type C struct
+export type D interface
+
+type C struct { }
+type D interface { }