fix segfault printing errors. add test case and improve messages.

Fixes #338.

R=rsc
CC=golang-dev
https://golang.org/cl/163083

src/pkg/rpc/server.go

@@ -214,28 +214,28 @@ func (server *serverType) register(rcvr interface{}) os.Error {
 		}
 		argType, ok := mtype.In(1).(*reflect.PtrType);
 		if !ok {
-			log.Stderr(mname, "arg type not a pointer:", argType.String());
+			log.Stderr(mname, "arg type not a pointer:", mtype.In(1));
 			continue;
 		}
 		if _, ok := argType.Elem().(*reflect.StructType); !ok {
-			log.Stderr(mname, "arg type not a pointer to a struct:", argType.String());
+			log.Stderr(mname, "arg type not a pointer to a struct:", argType);
 			continue;
 		}
 		replyType, ok := mtype.In(2).(*reflect.PtrType);
 		if !ok {
-			log.Stderr(mname, "reply type not a pointer:", replyType.String());
+			log.Stderr(mname, "reply type not a pointer:", mtype.In(2));
 			continue;
 		}
 		if _, ok := replyType.Elem().(*reflect.StructType); !ok {
-			log.Stderr(mname, "reply type not a pointer to a struct:", replyType.String());
+			log.Stderr(mname, "reply type not a pointer to a struct:", replyType);
 			continue;
 		}
 		if !isPublic(argType.Elem().Name()) {
-			log.Stderr(mname, "argument type not public:", argType.String());
+			log.Stderr(mname, "argument type not public:", argType);
 			continue;
 		}
 		if !isPublic(replyType.Elem().Name()) {
-			log.Stderr(mname, "reply type not public:", replyType.String());
+			log.Stderr(mname, "reply type not public:", replyType);
 			continue;
 		}
 		// Method needs one out: os.Error.

src/pkg/rpc/server_test.go

@@ -216,3 +216,38 @@ func TestCheckBadType(t *testing.T) {
 		t.Error("expected error about type; got", err)
 	}
 }
+
+type Bad int
+type local struct{}
+
+func (t *Bad) ArgNotPointer(args Args, reply *Reply) os.Error {
+	return nil
+}
+
+func (t *Bad) ArgNotPointerToStruct(args *int, reply *Reply) os.Error {
+	return nil
+}
+
+func (t *Bad) ReplyNotPointer(args *Args, reply Reply) os.Error {
+	return nil
+}
+
+func (t *Bad) ReplyNotPointerToStruct(args *Args, reply *int) os.Error {
+	return nil
+}
+
+func (t *Bad) ArgNotPublic(args *local, reply *Reply) os.Error {
+	return nil
+}
+
+func (t *Bad) ReplyNotPublic(args *Args, reply *local) os.Error {
+	return nil
+}
+
+// Check that registration handles lots of bad methods and a type with no suitable methods.
+func TestRegistrationError(t *testing.T) {
+	err := Register(new(Bad));
+	if err == nil {
+		t.Errorf("expected error registering bad type")
+	}
+}