reflect: fix stack overflow panic when using haveIdenticalUnderlyingType

haveIdenticalUnderlyingType raises stack overflow when compares
self-referential structs having same structure in different packages.

Change-Id: I7c79ab988edcffadcf7e0730a50b4d31b136bb6a
GitHub-Last-Rev: 4d4217f0c1
GitHub-Pull-Request: golang/go#45543
Reviewed-on: https://go-review.googlesource.com/c/go/+/309729
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/reflect/all_test.go

@@ -15,6 +15,8 @@ import (
 	"math/rand"
 	"os"
 	. "reflect"
+	"reflect/internal/example1"
+	"reflect/internal/example2"
 	"runtime"
 	"sort"
 	"strconv"
@@ -3808,6 +3810,16 @@ type Empty struct{}
 type MyStruct struct {
 	x int `some:"tag"`
 }
+type MyStruct1 struct {
+	x struct {
+		int `some:"bar"`
+	}
+}
+type MyStruct2 struct {
+	x struct {
+		int `some:"foo"`
+	}
+}
 type MyString string
 type MyBytes []byte
 type MyRunes []int32
@@ -4158,6 +4170,9 @@ var convertTests = []struct {
 		x int `some:"bar"`
 	}{}), V(MyStruct{})},
 
+	{V(MyStruct1{}), V(MyStruct2{})},
+	{V(MyStruct2{}), V(MyStruct1{})},
+
 	// can convert *byte and *MyByte
 	{V((*byte)(nil)), V((*MyByte)(nil))},
 	{V((*MyByte)(nil)), V((*byte)(nil))},
@@ -7231,3 +7246,13 @@ func iterateToString(it *MapIter) string {
 	sort.Strings(got)
 	return "[" + strings.Join(got, ", ") + "]"
 }
+
+func TestConvertibleTo(t *testing.T) {
+	t1 := ValueOf(example1.MyStruct{}).Type()
+	t2 := ValueOf(example2.MyStruct{}).Type()
+
+	// Shouldn't raise stack overflow
+	if t1.ConvertibleTo(t2) {
+		t.Fatalf("(%s).ConvertibleTo(%s) = true, want false", t1, t2)
+	}
+}

src/reflect/internal/example1/example.go

@@ -0,0 +1,6 @@
+package example1
+
+type MyStruct struct {
+	MyStructs []MyStruct
+	MyStruct  *MyStruct
+}

src/reflect/internal/example2/example.go

@@ -0,0 +1,6 @@
+package example2
+
+type MyStruct struct {
+	MyStructs []MyStruct
+	MyStruct  *MyStruct
+}

src/reflect/type.go

@@ -1599,7 +1599,7 @@ func haveIdenticalType(T, V Type, cmpTags bool) bool {
 		return T == V
 	}
 
-	if T.Name() != V.Name() || T.Kind() != V.Kind() {
+	if T.Name() != V.Name() || T.Kind() != V.Kind() || T.PkgPath() != V.PkgPath() {
 		return false
 	}