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| author | Matt T. Proud <matt.proud@gmail.com> | 2021-10-19 10:09:06 +0200 |
|---|---|---|
| committer | Damien Neil <dneil@google.com> | 2021-10-19 18:42:57 +0000 |
| commit | 7999fd4710e7f987e86d7b32dd9af31ced4810ba (patch) | |
| tree | 6788142cc71e7dab110b1a307e8ffec3b9581bdb /src/errors | |
| parent | 6c3cd5d2eb7149c9c1ced7d70c3f4157f27c1588 (diff) | |
| download | go-7999fd4710e7f987e86d7b32dd9af31ced4810ba.tar.xz | |
errors: mention Is methods should not call Unwrap
errors.Is internally unwraps the error until the error matches the
target. Because of this, a user-authored Is method on an error type
need not call errors.Unwrap on itself or the target, because that would
make the unwrapping operation O(N^2). It is a subtle detail to remind
authors for resource efficiency reasons.
Change-Id: Ic1ba59a5bdbfe2c7cb51a2cba2537ab6de4a13ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/356789
Reviewed-by: Jean de Klerk <deklerk@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Trust: Jean de Klerk <deklerk@google.com>
Trust: Damien Neil <dneil@google.com>
Run-TryBot: Jean de Klerk <deklerk@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Diffstat (limited to 'src/errors')
| -rw-r--r-- | src/errors/wrap.go | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/errors/wrap.go b/src/errors/wrap.go index 4eb4f9ae37..b73d5a8ce2 100644 --- a/src/errors/wrap.go +++ b/src/errors/wrap.go @@ -35,7 +35,8 @@ func Unwrap(err error) error { // func (m MyError) Is(target error) bool { return target == fs.ErrExist } // // then Is(MyError{}, fs.ErrExist) returns true. See syscall.Errno.Is for -// an example in the standard library. +// 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 { return err == target |