1 files changed, 104 insertions, 0 deletions
diff --git a/libgo/go/encoding/json/encode_test.go b/libgo/go/encoding/json/encode_test.go
index be74c99..5be0a99 100644
--- a/libgo/go/encoding/json/encode_test.go
+++ b/libgo/go/encoding/json/encode_test.go
@@ -206,3 +206,107 @@ func TestAnonymousNonstruct(t *testing.T) {
 		t.Errorf("got %q, want %q", got, want)
 	}
 }
+
+type BugA struct {
+	S string
+}
+
+type BugB struct {
+	BugA
+	S string
+}
+
+type BugC struct {
+	S string
+}
+
+// Legal Go: We never use the repeated embedded field (S).
+type BugX struct {
+	A int
+	BugA
+	BugB
+}
+
+// Issue 5245.
+func TestEmbeddedBug(t *testing.T) {
+	v := BugB{
+		BugA{"A"},
+		"B",
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"B"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+	// Now check that the duplicate field, S, does not appear.
+	x := BugX{
+		A: 23,
+	}
+	b, err = Marshal(x)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want = `{"A":23}`
+	got = string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+type BugD struct { // Same as BugA after tagging.
+	XXX string `json:"S"`
+}
+
+// BugD's tagged S field should dominate BugA's.
+type BugY struct {
+	BugA
+	BugD
+}
+
+// Test that a field with a tag dominates untagged fields.
+func TestTaggedFieldDominates(t *testing.T) {
+	v := BugY{
+		BugA{"BugA"},
+		BugD{"BugD"},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"BugD"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+// There are no tags here, so S should not appear.
+type BugZ struct {
+	BugA
+	BugC
+	BugY // Contains a tagged S field through BugD; should not dominate.
+}
+
+func TestDuplicatedFieldDisappears(t *testing.T) {
+	v := BugZ{
+		BugA{"BugA"},
+		BugC{"BugC"},
+		BugY{
+			BugA{"nested BugA"},
+			BugD{"nested BugD"},
+		},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}