errors: return early for Is(nil, ...)

If err is nil it wouldn't match any given target error except for nil,
so we can return early to speed up cases where Is is used without a
preceding err != nil check.

Change-Id: Ib33cff50453fe070f06871ce8074694c81ab787b
Reviewed-on: https://go-review.googlesource.com/c/go/+/576015
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

diff --git a/src/errors/wrap.go b/src/errors/wrap.go
index 88ee0a9281f2f13b6e2bcaeb77163a4760497725..57060517b552c73c819c8e416d374a2c01908de7 100644 (file)
--- a/src/errors/wrap.go
+++ b/src/errors/wrap.go
@@ -42,7 +42,7 @@ func Unwrap(err error) error {
 // an example in the standard library. An Is method should only shallowly
 // compare err and the target and not call [Unwrap] on either.
 func Is(err, target error) bool {
-       if target == nil {
+       if err == nil || target == nil {
                return err == target
        }
 

diff --git a/src/errors/wrap_test.go b/src/errors/wrap_test.go
index 0a7bc5d16a1344c87cb7c802cd5c9fb6726dd1c8..58ed95fd9a0fc735e7ffe774304ddea1a5ab9e2a 100644 (file)
--- a/src/errors/wrap_test.go
+++ b/src/errors/wrap_test.go
@@ -30,6 +30,7 @@ func TestIs(t *testing.T) {
                match  bool
        }{
                {nil, nil, true},
+               {nil, err1, false},
                {err1, nil, false},
                {err1, err1, true},
                {erra, err1, true},