reflect.DeepEquals: channels of the same underlying type can be equal.

nevkontakte · nevkontakte · commit b66fa5779288 · 2023-11-01T20:58:11.000Z
According to the Go spec, channels are equal if they have been created by the same call to make(). Prior to this change reflect.DeepEqual() would return false when comparing two channels, one of this is a named type (e.g. `type ch chan string`) and was created by type conversion from the other one. After this change, DeepEquals behavior becomes consistent with the == operator. Upstream has a similar bug: golang/go#63886.
diff --git a/compiler/natives/src/reflect/reflect.go b/compiler/natives/src/reflect/reflect.go
@@ -1639,7 +1639,7 @@ func DeepEqual(a1, a2 interface{}) bool {
 	if i1 == i2 {
 		return true
 	}
-	if i1 == nil || i2 == nil || i1.Get("constructor") != i2.Get("constructor") {
+	if i1 == nil || i2 == nil {
 		return false
 	}
 	return deepValueEqualJs(ValueOf(a1), ValueOf(a2), nil)
@@ -1649,6 +1649,11 @@ func deepValueEqualJs(v1, v2 Value, visited [][2]unsafe.Pointer) bool {
 	if !v1.IsValid() || !v2.IsValid() {
 		return !v1.IsValid() && !v2.IsValid()
 	}
+
+	if v1.Kind() == Chan && v2.Kind() == Chan {
+		return v1.object() == v2.object()
+	}
+
 	if v1.Type() != v2.Type() {
 		return false
 	}
diff --git a/tests/misc_test.go b/tests/misc_test.go
@@ -959,3 +959,31 @@ func TestFileSetSize(t *testing.T) {
 		t.Errorf("Got: unsafe.Sizeof(token.FileSet{}) %v, Want: %v", n2, n1)
 	}
 }
+
+func TestChanEquality(t *testing.T) {
+	type ch chan string
+
+	ch1 := make(chan string)
+	ch2 := make(ch)
+	ch3 := ch(ch1)
+
+	t.Run("equal", func(t *testing.T) {
+		if ch1 != ch3 {
+			t.Errorf("Got: ch1 != ch3. Want: channels created by the same call to make are equal.")
+		}
+		if runtime.Compiler != "gopherjs" {
+			t.Skip("https://github.com/golang/go/issues/63886")
+		}
+		if !reflect.DeepEqual(ch1, ch3) {
+			t.Errorf("Got: reflect.DeepEqual(ch1, ch3) == false. Want: channels created by the same call to make are equal.")
+		}
+	})
+	t.Run("not equal", func(t *testing.T) {
+		if ch1 == ch2 {
+			t.Errorf("Got: ch1 == ch2. Want: channels created by different calls to make are not equal.")
+		}
+		if reflect.DeepEqual(ch1, ch2) {
+			t.Errorf("Got: reflect.DeepEqual(ch1, ch2) == true. Want: channels created by different calls to make are not equal.")
+		}
+	})
+}

Original file line number	Diff line number	Diff line change
`@@ -1639,7 +1639,7 @@ func DeepEqual(a1, a2 interface{}) bool {`
`1639`	`1639`	`if i1 == i2 {`
`1640`	`1640`	`return true`
`1641`	`1641`	`}`
`1642`		`- if i1 == nil \|\| i2 == nil \|\| i1.Get("constructor") != i2.Get("constructor") {`
	`1642`	`+ if i1 == nil \|\| i2 == nil {`
`1643`	`1643`	`return false`
`1644`	`1644`	`}`
`1645`	`1645`	`return deepValueEqualJs(ValueOf(a1), ValueOf(a2), nil)`
`@@ -1649,6 +1649,11 @@ func deepValueEqualJs(v1, v2 Value, visited [][2]unsafe.Pointer) bool {`
`1649`	`1649`	`if !v1.IsValid() \|\| !v2.IsValid() {`
`1650`	`1650`	`return !v1.IsValid() && !v2.IsValid()`
`1651`	`1651`	`}`
	`1652`	`+`
	`1653`	`+ if v1.Kind() == Chan && v2.Kind() == Chan {`
	`1654`	`+ return v1.object() == v2.object()`
	`1655`	`+ }`
	`1656`	`+`
`1652`	`1657`	`if v1.Type() != v2.Type() {`
`1653`	`1658`	`return false`
`1654`	`1659`	`}`