gob: fix trivial bug in map marshaling.

Forgot to send key/value types.

R=rsc
CC=golang-dev, hmc2you
https://golang.org/cl/4434058

src/pkg/gob/encoder.go

@@ -116,6 +116,9 @@ func (enc *Encoder) sendActualType(w io.Writer, state *encoderState, ut *userTyp
 		}
 	case reflect.Array, reflect.Slice:
 		enc.sendType(w, state, st.Elem())
+	case reflect.Map:
+		enc.sendType(w, state, st.Key())
+		enc.sendType(w, state, st.Elem())
 	}
 	return true
 }

src/pkg/gob/encoder_test.go

@@ -514,3 +514,38 @@ func TestNestedInterfaces(t *testing.T) {
 		t.Fatalf("final value %d; expected %d", inner.A, 7)
 	}
 }
+
+// The bugs keep coming. We forgot to send map subtypes before the map.
+
+type Bug1Elem struct {
+	Name string
+	Id   int
+}
+
+type Bug1StructMap map[string]Bug1Elem
+
+func bug1EncDec(in Bug1StructMap, out *Bug1StructMap) os.Error {
+	return nil
+}
+
+func TestMapBug1(t *testing.T) {
+	in := make(Bug1StructMap)
+	in["val1"] = Bug1Elem{"elem1", 1}
+	in["val2"] = Bug1Elem{"elem2", 2}
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(in)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	dec := NewDecoder(b)
+	out := make(Bug1StructMap)
+	err = dec.Decode(&out)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if !reflect.DeepEqual(in, out) {
+		t.Errorf("mismatch: %v %v", in, out)
+	}
+}