reflect: unnamed interface types have no name

Fixes #15468

Change-Id: I8723171f87774a98d5e80e7832ebb96dd1fbea74
Reviewed-on: https://go-review.googlesource.com/22524Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

src/reflect/all_test.go

@@ -5659,20 +5659,25 @@ type nameTest struct {
 }
 
 var nameTests = []nameTest{
-	{int32(0), "int32"},
-	{D1{}, "D1"},
-	{[]D1{}, ""},
-	{(chan D1)(nil), ""},
-	{(func() D1)(nil), ""},
-	{(<-chan D1)(nil), ""},
-	{(chan<- D1)(nil), ""},
-	{TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678(0), "TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678"},
+	{(*int32)(nil), "int32"},
+	{(*D1)(nil), "D1"},
+	{(*[]D1)(nil), ""},
+	{(*chan D1)(nil), ""},
+	{(*func() D1)(nil), ""},
+	{(*<-chan D1)(nil), ""},
+	{(*chan<- D1)(nil), ""},
+	{(*interface{})(nil), ""},
+	{(*interface {
+		F()
+	})(nil), ""},
+	{(*TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678)(nil), "TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678"},
 }
 
 func TestNames(t *testing.T) {
 	for _, test := range nameTests {
-		if got := TypeOf(test.v).Name(); got != test.want {
-			t.Errorf("%T Name()=%q, want %q", test.v, got, test.want)
+		typ := TypeOf(test.v).Elem()
+		if got := typ.Name(); got != test.want {
+			t.Errorf("%v Name()=%q, want %q", typ, got, test.want)
 		}
 	}
 }

src/reflect/type.go

@@ -867,6 +867,9 @@ func (t *rtype) Name() string {
 	if hasPrefix(s, "func(") {
 		return ""
 	}
+	if hasPrefix(s, "interface {") {
+		return ""
+	}
 	switch s[0] {
 	case '[', '*', '<':
 		return ""

src/runtime/type.go

@@ -132,6 +132,9 @@ func (t *_type) name() string {
 	if hasPrefix(s, "func(") {
 		return ""
 	}
+	if hasPrefix(s, "interface {") {
+		return ""
+	}
 	switch s[0] {
 	case '[', '*', '<':
 		return ""