remove xerrors (#292)

Versions older than Go 1.13 are no longer in use. Remove unnecessary
dependencies.

5 files changed, 7 insertions, 31 deletions

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9a50673..a93f058 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x, 1.17.x, 1.18.x]
+        go-version: [1.13.x, 1.14.x, 1.15.x, 1.16.x, 1.17.x, 1.18.x]
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     steps:
diff --git a/cmp/cmpopts/errors_xerrors.go b/cmp/cmpopts/errors_xerrors.go
deleted file mode 100644
index 60b0727..0000000
--- a/cmp/cmpopts/errors_xerrors.go
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright 2021, The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.13
-// +build !go1.13
-
-// TODO(≥go1.13): For support on <go1.13, we use the xerrors package.
-// Drop this file when we no longer support older Go versions.
-
-package cmpopts
-
-import "golang.org/x/xerrors"
-
-func compareErrors(x, y interface{}) bool {
-	xe := x.(error)
-	ye := y.(error)
-	return xerrors.Is(xe, ye) || xerrors.Is(ye, xe)
-}
diff --git a/cmp/cmpopts/util_test.go b/cmp/cmpopts/util_test.go
index b19bcab..c2eaf0b 100644
--- a/cmp/cmpopts/util_test.go
+++ b/cmp/cmpopts/util_test.go
@@ -17,7 +17,6 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
-	"golang.org/x/xerrors"
 )
 
 type (
@@ -531,14 +530,14 @@ func TestOptions(t *testing.T) {
 		reason:    "user-defined EOF is not exactly equal",
 	}, {
 		label:     "EquateErrors",
-		x:         xerrors.Errorf("wrapped: %w", io.EOF),
+		x:         fmt.Errorf("wrapped: %w", io.EOF),
 		y:         io.EOF,
 		opts:      []cmp.Option{EquateErrors()},
 		wantEqual: true,
 		reason:    "wrapped io.EOF is equal according to errors.Is",
 	}, {
 		label:     "EquateErrors",
-		x:         xerrors.Errorf("wrapped: %w", io.EOF),
+		x:         fmt.Errorf("wrapped: %w", io.EOF),
 		y:         io.EOF,
 		wantEqual: false,
 		reason:    "wrapped io.EOF is not equal without EquateErrors option",
@@ -585,14 +584,14 @@ func TestOptions(t *testing.T) {
 		reason:    "user-defined EOF is not exactly equal",
 	}, {
 		label:     "EquateErrors",
-		x:         xerrors.Errorf("wrapped: %w", io.EOF),
+		x:         fmt.Errorf("wrapped: %w", io.EOF),
 		y:         io.EOF,
 		opts:      []cmp.Option{EquateErrors()},
 		wantEqual: true,
 		reason:    "wrapped io.EOF is equal according to errors.Is",
 	}, {
 		label:     "EquateErrors",
-		x:         xerrors.Errorf("wrapped: %w", io.EOF),
+		x:         fmt.Errorf("wrapped: %w", io.EOF),
 		y:         io.EOF,
 		wantEqual: false,
 		reason:    "wrapped io.EOF is not equal without EquateErrors option",
@@ -639,14 +638,14 @@ func TestOptions(t *testing.T) {
 		reason:    "user-defined EOF is not exactly equal",
 	}, {
 		label:     "EquateErrors",
-		x:         struct{ E error }{xerrors.Errorf("wrapped: %w", io.EOF)},
+		x:         struct{ E error }{fmt.Errorf("wrapped: %w", io.EOF)},
 		y:         struct{ E error }{io.EOF},
 		opts:      []cmp.Option{EquateErrors()},
 		wantEqual: true,
 		reason:    "wrapped io.EOF is equal according to errors.Is",
 	}, {
 		label:     "EquateErrors",
-		x:         struct{ E error }{xerrors.Errorf("wrapped: %w", io.EOF)},
+		x:         struct{ E error }{fmt.Errorf("wrapped: %w", io.EOF)},
 		y:         struct{ E error }{io.EOF},
 		wantEqual: false,
 		reason:    "wrapped io.EOF is not equal without EquateErrors option",
diff --git a/go.mod b/go.mod
index 4cdb762..b570017 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,3 @@
 module github.com/google/go-cmp
 
 go 1.11
-
-require golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543
diff --git a/go.sum b/go.sum
deleted file mode 100644
index 3ab73ea..0000000
--- a/go.sum
+++ /dev/null
@@ -1,2 +0,0 @@
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=