[go] errors: optimize Is type checks
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Chencheng Jiang (Gerrit)
Jun 23, 2026, 3:42:49 PM (4 days ago) Jun 23
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Chencheng Jiang has uploaded the change for review![]( "Open in Gerrit")
Commit message
errors: optimize Is type checks
Reduce the dynamic type checks performed while walking an error tree. Instead of checking for Is before switching on Unwrap, handle the Is+Unwrap combinations directly in the type switch.
This preserves the existing order: compare comparable targets, call Is if present, then traverse Unwrap. Add tests for errors that implement both Is and Unwrap.
Also add reflectlite.TypeComparable so Is can test target comparability without constructing a reflectlite.Type interface just to call Comparable.
Add benchmarks for direct, wrapped, joined, and uncomparable-target cases.
On linux/amd64, Intel i7-14700KF, go1.27-devel:
name old time/op new time/op delta
IsDirectHit-20 2.627ns 2.451ns -6.72%
IsDirectMiss-20 3.754ns 3.018ns -19.59%
IsWrappedHit-20 19.23ns 17.54ns -8.76%
IsWrappedMiss-20 20.89ns 18.41ns -11.85%
IsJoinHit-20 27.76ns 23.80ns -14.28%
IsJoinMiss-20 33.74ns 26.40ns -21.75%
IsUncomparableTarget-20 5.657ns 5.426ns -4.07%
geomean 11.12ns 9.711ns -12.65%
Change-Id: I660499828a3d28a2ebf485e5fb7be624f2eee378
Change diff
diff --git a/src/errors/wrap.go b/src/errors/wrap.go
index e4a5ca3..aef3749 100644
--- a/src/errors/wrap.go
+++ b/src/errors/wrap.go
@@ -4,9 +4,7 @@
package errors
-import (
- "internal/reflectlite"
-)
+import "internal/reflectlite"
// Unwrap returns the result of calling the Unwrap method on err, if err's
// type contains an Unwrap method returning error.
@@ -47,7 +45,7 @@
return err == target
}
- isComparable := reflectlite.TypeOf(target).Comparable()
+ isComparable := reflectlite.TypeComparable(target)
return is(err, target, isComparable)
}
@@ -56,10 +54,33 @@
if targetComparable && err == target {
return true
}
- if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {
- return true
- }
switch x := err.(type) {
+ case interface {
+ Is(error) bool
+ Unwrap() error
+ }:
+ if x.Is(target) {
+ return true
+ }
+ err = x.Unwrap()
+ if err == nil {
+ return false
+ }
+ case interface {
+ Is(error) bool
+ Unwrap() []error
+ }:
+ if x.Is(target) {
+ return true
+ }
+ for _, err := range x.Unwrap() {
+ if is(err, target, targetComparable) {
+ return true
+ }
+ }
+ return false
+ case interface{ Is(error) bool }:
+ return x.Is(target)
case interface{ Unwrap() error }:
err = x.Unwrap()
if err == nil {
diff --git a/src/errors/wrap_test.go b/src/errors/wrap_test.go
index 81c795a..6f0cfc3 100644
--- a/src/errors/wrap_test.go
+++ b/src/errors/wrap_test.go
@@ -23,6 +23,12 @@
poser := &poser{"either 1 or 3", func(err error) bool {
return err == err1 || err == err3
}}
+ poserWrap := poserWrapped{err: err1, f: func(err error) bool {
+ return err == err3
+ }}
+ poserMulti := poserMultiErr{errs: []error{err1}, f: func(err error) bool {
+ return err == err3
+ }}
testCases := []struct {
err error
@@ -42,6 +48,10 @@
{poser, err3, true},
{poser, erra, false},
{poser, errb, false},
+ {poserWrap, err1, true},
+ {poserWrap, err3, true},
+ {poserMulti, err1, true},
+ {poserMulti, err3, true},
{errorUncomparable{}, errorUncomparable{}, true},
{errorUncomparable{}, &errorUncomparable{}, false},
{&errorUncomparable{}, errorUncomparable{}, true},
@@ -92,6 +102,24 @@
return true
}
+type poserWrapped struct {
+ err error
+ f func(error) bool
+}
+
+func (p poserWrapped) Error() string { return "poserWrapped" }
+func (p poserWrapped) Is(err error) bool { return p.f(err) }
+func (p poserWrapped) Unwrap() error { return p.err }
+
+type poserMultiErr struct {
+ errs []error
+ f func(error) bool
+}
+
+func (p poserMultiErr) Error() string { return "poserMultiErr" }
+func (p poserMultiErr) Is(err error) bool { return p.f(err) }
+func (p poserMultiErr) Unwrap() []error { return p.errs }
+
func TestAs(t *testing.T) {
var errT errorT
var errP *fs.PathError
@@ -367,6 +395,75 @@
}
}
+func BenchmarkIsDirectHit(b *testing.B) {
+ err := errors.New("x")
+ for i := 0; i < b.N; i++ {
+ if !errors.Is(err, err) {
+ b.Fatal("Is failed")
+ }
+ }
+}
+
+func BenchmarkIsDirectMiss(b *testing.B) {
+ err := errors.New("x")
+ target := errors.New("y")
+ for i := 0; i < b.N; i++ {
+ if errors.Is(err, target) {
+ b.Fatal("Is succeeded")
+ }
+ }
+}
+
+func BenchmarkIsWrappedHit(b *testing.B) {
+ target := errors.New("x")
+ err := wrapped{"wrap", wrapped{"wrap", wrapped{"wrap", target}}}
+ for i := 0; i < b.N; i++ {
+ if !errors.Is(err, target) {
+ b.Fatal("Is failed")
+ }
+ }
+}
+
+func BenchmarkIsWrappedMiss(b *testing.B) {
+ target := errors.New("x")
+ err := wrapped{"wrap", wrapped{"wrap", wrapped{"wrap", errors.New("y")}}}
+ for i := 0; i < b.N; i++ {
+ if errors.Is(err, target) {
+ b.Fatal("Is succeeded")
+ }
+ }
+}
+
+func BenchmarkIsJoinHit(b *testing.B) {
+ target := errors.New("x")
+ err := multiErr{errorT{"a"}, multiErr{errorT{"b"}, target}, errorT{"c"}}
+ for i := 0; i < b.N; i++ {
+ if !errors.Is(err, target) {
+ b.Fatal("Is failed")
+ }
+ }
+}
+
+func BenchmarkIsJoinMiss(b *testing.B) {
+ target := errors.New("x")
+ err := multiErr{errorT{"a"}, multiErr{errorT{"b"}, errors.New("y")}, errorT{"c"}}
+ for i := 0; i < b.N; i++ {
+ if errors.Is(err, target) {
+ b.Fatal("Is succeeded")
+ }
+ }
+}
+
+func BenchmarkIsUncomparableTarget(b *testing.B) {
+ err := errorUncomparable{}
+ target := errorUncomparable{}
+ for i := 0; i < b.N; i++ {
+ if !errors.Is(err, target) {
+ b.Fatal("Is failed")
+ }
+ }
+}
+
func BenchmarkAs(b *testing.B) {
err := multiErr{multiErr{multiErr{errors.New("a"), errorT{"a"}}, errorT{"b"}}}
for i := 0; i < b.N; i++ {
diff --git a/src/internal/reflectlite/type.go b/src/internal/reflectlite/type.go
index 88cc50d..1cacbc0 100644
--- a/src/internal/reflectlite/type.go
+++ b/src/internal/reflectlite/type.go
@@ -387,6 +387,12 @@
return toType(abi.TypeOf(i))
}
+// TypeComparable reports whether values of the dynamic type of i are comparable.
+// It is equivalent to TypeOf(i).Comparable() for non-nil i.
+func TypeComparable(i any) bool {
+ return abi.TypeOf(i).Equal != nil
+}
+
func (t rtype) Implements(u Type) bool {
if u == nil {
panic("reflect: nil type passed to Type.Implements")
Change information
Files:
- M src/errors/wrap.go
- M src/errors/wrap_test.go
- M src/internal/reflectlite/type.go
Change size: M
Delta: 3 files changed, 131 insertions(+), 7 deletions(-)
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Chencheng Jiang (Gerrit)
Jun 25, 2026, 5:40:13 PM (2 days ago) Jun 25
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Attention needed from Ian Lance Taylor and Russ Cox
Chencheng Jiang uploaded new patchset![]( "Open in Gerrit")
Chencheng Jiang uploaded patch set #2 to this change.
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Emmanuel Odeke (Gerrit)
Jun 26, 2026, 10:04:24 AM (21 hours ago) Jun 26
to Chencheng Jiang, goph...@pubsubhelper.golang.org, Russ Cox, Ian Lance Taylor, Gopher Robot, golang-co...@googlegroups.com
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Chencheng Jiang (Gerrit)
Jun 26, 2026, 1:31:13 PM (17 hours ago) Jun 26
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Chencheng Jiang added 1 comment![]( "Open in Gerrit")
Patchset-level comments
File-level comment, Patchset 2 (Latest):
Chencheng Jiang . resolved
@emma...@orijtech.com Can you rerun the trybot? I don't think this error is related to my commit.
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Emmanuel Odeke (Gerrit)
Jun 26, 2026, 2:38:38 PM (16 hours ago) Jun 26
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Emmanuel Odeke voted Commit-Queue+1![]( "Open in Gerrit")
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