xerrors: fix Is panics if target is uncomparable

Analogous change to golang.org/cl/175260 Fixes golang/go#31841 Change-Id: I93bf093e8d5c13269fe7164a3a1b6956450998e5 Reviewed-on: https://go-review.googlesource.com/c/xerrors/+/174980 Reviewed-by: Brad Fitzpatrick <[email protected]> Reviewed-by: Damien Neil <[email protected]> Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>
golang · May 6, 2019 · 3850056 · 3850056
1 parent 1f06c39
commit 3850056
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 1 deletion.
diff --git a/wrap.go b/wrap.go
@@ -51,8 +51,10 @@ func Is(err, target error) bool {
 	if target == nil {
 		return err == target
 	}
+
+	isComparable := target == nil || reflect.TypeOf(target).Comparable()
 	for {
-		if err == target {
+		if isComparable && err == target {
 			return true
 		}
 		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {

diff --git a/wrap_test.go b/wrap_test.go
@@ -47,6 +47,12 @@ func TestIs(t *testing.T) {
 		{poser, errb, false},
 		{poser, erro, false},
 		{poser, errco, false},
+		{errorUncomparable{}, errorUncomparable{}, true},
+		{errorUncomparable{}, &errorUncomparable{}, false},
+		{&errorUncomparable{}, errorUncomparable{}, true},
+		{&errorUncomparable{}, &errorUncomparable{}, false},
+		{errorUncomparable{}, err1, false},
+		{&errorUncomparable{}, err1, false},
 	}
 	for _, tc := range testCases {
 		t.Run("", func(t *testing.T) {
@@ -237,3 +243,16 @@ type errWrap struct{ error }
 func (errWrap) Error() string { return "wrapped" }
 
 func (errWrap) Unwrap() error { return nil }
+
+type errorUncomparable struct {
+	f []string
+}
+
+func (errorUncomparable) Error() string {
+	return "uncomparable error"
+}
+
+func (errorUncomparable) Is(target error) bool {
+	_, ok := target.(errorUncomparable)
+	return ok
+}