all: remove os.ErrTimeout

It is unclear whether the current definition of os.IsTimeout is
desirable or not. Drop ErrTimeout for now so we can consider adding it
(or some other error) in a future release with a corrected definition.

Fixes #33411

Change-Id: I8b880da7d22afc343a08339eb5f0efd1075ecafe
Reviewed-on: https://go-review.googlesource.com/c/go/+/188758
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

19 files changed, 8 insertions, 150 deletions

diff --git a/api/go1.13.txt b/api/go1.13.txt
index a8e39ce8ea..d964d64019 100644
--- a/api/go1.13.txt
+++ b/api/go1.13.txt
@@ -209,8 +209,6 @@ pkg net/http, type Transport struct, ForceAttemptHTTP2 bool
 pkg net/http, type Transport struct, ReadBufferSize int
 pkg net/http, type Transport struct, WriteBufferSize int
 pkg net, method (*DNSConfigError) Unwrap() error
-pkg net, method (*DNSError) Is(error) bool
-pkg net, method (*OpError) Is(error) bool
 pkg net, method (*OpError) Unwrap() error
 pkg net, type DNSError struct, IsNotFound bool
 pkg net, type ListenConfig struct, KeepAlive time.Duration
@@ -237,7 +235,6 @@ pkg os (netbsd-arm64), const O_SYNC = 128
 pkg os (netbsd-arm64), const O_TRUNC = 1024
 pkg os (netbsd-arm64), const PathListSeparator = 58
 pkg os (netbsd-arm64), const PathSeparator = 47
-pkg os, var ErrTimeout error
 pkg path/filepath (netbsd-arm64-cgo), const ListSeparator = 58
 pkg path/filepath (netbsd-arm64-cgo), const Separator = 47
 pkg path/filepath (netbsd-arm64), const ListSeparator = 58
diff --git a/src/context/context.go b/src/context/context.go
index b400396513..62590850a6 100644
--- a/src/context/context.go
+++ b/src/context/context.go
@@ -49,7 +49,6 @@ package context
 
 import (
 	"errors"
-	"internal/oserror"
 	"internal/reflectlite"
 	"sync"
 	"time"
@@ -163,9 +162,6 @@ type deadlineExceededError struct{}
 func (deadlineExceededError) Error() string   { return "context deadline exceeded" }
 func (deadlineExceededError) Timeout() bool   { return true }
 func (deadlineExceededError) Temporary() bool { return true }
-func (deadlineExceededError) Is(target error) bool {
-	return target == oserror.ErrTimeout
-}
 
 // An emptyCtx is never canceled, has no values, and has no deadline. It is not
 // struct{}, since vars of this type must have distinct addresses.
diff --git a/src/context/context_test.go b/src/context/context_test.go
index 9991c5b09c..0e69e2f6fd 100644
--- a/src/context/context_test.go
+++ b/src/context/context_test.go
@@ -5,10 +5,8 @@
 package context
 
 import (
-	"errors"
 	"fmt"
 	"math/rand"
-	"os"
 	"runtime"
 	"strings"
 	"sync"
@@ -649,7 +647,4 @@ func XTestDeadlineExceededSupportsTimeout(t testingT) {
 	if !i.Timeout() {
 		t.Fatal("wrong value for timeout")
 	}
-	if !errors.Is(DeadlineExceeded, os.ErrTimeout) {
-		t.Fatal("errors.Is(DeadlineExceeded, os.ErrTimeout) = false, want true")
-	}
 }
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index bd866ee738..fb862459c8 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -250,7 +250,7 @@ var pkgDeps = map[string][]string{
 	"compress/gzip":                  {"L4", "compress/flate"},
 	"compress/lzw":                   {"L4"},
 	"compress/zlib":                  {"L4", "compress/flate"},
-	"context":                        {"errors", "internal/oserror", "internal/reflectlite", "sync", "time"},
+	"context":                        {"errors", "internal/reflectlite", "sync", "time"},
 	"database/sql":                   {"L4", "container/list", "context", "database/sql/driver", "database/sql/internal"},
 	"database/sql/driver":            {"L4", "context", "time", "database/sql/internal"},
 	"debug/dwarf":                    {"L4"},
diff --git a/src/internal/oserror/errors.go b/src/internal/oserror/errors.go
index 8fccc95482..28a1ab32d3 100644
--- a/src/internal/oserror/errors.go
+++ b/src/internal/oserror/errors.go
@@ -15,32 +15,4 @@ var (
 	ErrExist      = errors.New("file already exists")
 	ErrNotExist   = errors.New("file does not exist")
 	ErrClosed     = errors.New("file already closed")
-	ErrTimeout    = timeoutError{}
 )
-
-type timeoutError struct{}
-
-func (timeoutError) Error() string { return "deadline exceeded" }
-func (timeoutError) Timeout() bool { return true }
-
-type temporaryError struct{}
-
-func (temporaryError) Error() string   { return "temporary error" }
-func (temporaryError) Temporary() bool { return true }
-
-// IsTimeout reports whether err indicates a timeout.
-func IsTimeout(err error) bool {
-	for err != nil {
-		if err == ErrTimeout {
-			return true
-		}
-		if x, ok := err.(interface{ Timeout() bool }); ok {
-			return x.Timeout()
-		}
-		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(ErrTimeout) {
-			return true
-		}
-		err = errors.Unwrap(err)
-	}
-	return false
-}
diff --git a/src/internal/oserror/errors_test.go b/src/internal/oserror/errors_test.go
deleted file mode 100644
index bf3e057ccf..0000000000
--- a/src/internal/oserror/errors_test.go
+++ /dev/null
@@ -1,43 +0,0 @@
-package oserror_test
-
-import (
-	"errors"
-	"fmt"
-	"internal/oserror"
-	"os"
-	"testing"
-)
-
-type ttError struct {
-	timeout bool
-}
-
-func (e ttError) Error() string {
-	return fmt.Sprintf("ttError{timeout:%v}", e.timeout)
-}
-func (e ttError) Timeout() bool { return e.timeout }
-
-type isError struct {
-	err error
-}
-
-func (e isError) Error() string        { return fmt.Sprintf("isError(%v)", e.err) }
-func (e isError) Is(target error) bool { return e.err == target }
-
-func TestIsTimeout(t *testing.T) {
-	for _, test := range []struct {
-		want bool
-		err  error
-	}{
-		{true, ttError{timeout: true}},
-		{true, isError{os.ErrTimeout}},
-		{true, os.ErrTimeout},
-		{true, fmt.Errorf("wrap: %w", os.ErrTimeout)},
-		{false, ttError{timeout: false}},
-		{false, errors.New("error")},
-	} {
-		if got, want := oserror.IsTimeout(test.err), test.want; got != want {
-			t.Errorf("IsTimeout(err) = %v, want %v\n%+v", got, want, test.err)
-		}
-	}
-}
diff --git a/src/internal/poll/fd.go b/src/internal/poll/fd.go
index 5009e2671b..c0de50c1b4 100644
--- a/src/internal/poll/fd.go
+++ b/src/internal/poll/fd.go
@@ -11,7 +11,6 @@ package poll
 
 import (
 	"errors"
-	"internal/oserror"
 )
 
 // ErrNetClosing is returned when a network descriptor is used after
@@ -47,10 +46,6 @@ func (e *TimeoutError) Error() string   { return "i/o timeout" }
 func (e *TimeoutError) Timeout() bool   { return true }
 func (e *TimeoutError) Temporary() bool { return true }
 
-func (e *TimeoutError) Is(target error) bool {
-	return target == oserror.ErrTimeout
-}
-
 // ErrNotPollable is returned when the file or socket is not suitable
 // for event notification.
 var ErrNotPollable = errors.New("not pollable")
diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
index c31cbfd814..69c99fe7db 100644
--- a/src/net/cgo_unix.go
+++ b/src/net/cgo_unix.go
@@ -24,7 +24,6 @@ import "C"
 
 import (
 	"context"
-	"os"
 	"syscall"
 	"unsafe"
 )
@@ -38,14 +37,6 @@ func (eai addrinfoErrno) Error() string   { return C.GoString(C.gai_strerror(C.i
 func (eai addrinfoErrno) Temporary() bool { return eai == C.EAI_AGAIN }
 func (eai addrinfoErrno) Timeout() bool   { return false }
 
-func (eai addrinfoErrno) Is(target error) bool {
-	switch target {
-	case os.ErrTimeout:
-		return eai.Timeout()
-	}
-	return false
-}
-
 type portLookupResult struct {
 	port int
 	err  error
diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index e3a1a10cc6..5c1708c832 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -2284,14 +2284,6 @@ func (e *httpError) Error() string   { return e.err }
 func (e *httpError) Timeout() bool   { return e.timeout }
 func (e *httpError) Temporary() bool { return true }
 
-func (e *httpError) Is(target error) bool {
-	switch target {
-	case os.ErrTimeout:
-		return e.timeout
-	}
-	return false
-}
-
 var errTimeout error = &httpError{err: "net/http: timeout awaiting response headers", timeout: true}
 
 // errRequestCanceled is set to be identical to the one from h2 to facilitate
@@ -2626,10 +2618,6 @@ func (tlsHandshakeTimeoutError) Timeout() bool   { return true }
 func (tlsHandshakeTimeoutError) Temporary() bool { return true }
 func (tlsHandshakeTimeoutError) Error() string   { return "net/http: TLS handshake timeout" }
 
-func (tlsHandshakeTimeoutError) Is(target error) bool {
-	return target == os.ErrTimeout
-}
-
 // fakeLocker is a sync.Locker which does nothing. It's used to guard
 // test-only fields when not under test, to avoid runtime atomic
 // overhead.
diff --git a/src/net/net.go b/src/net/net.go
index 54e1ac383a..4ed40237a8 100644
--- a/src/net/net.go
+++ b/src/net/net.go
@@ -516,14 +516,6 @@ func (e *OpError) Temporary() bool {
 	return ok && t.Temporary()
 }
 
-func (e *OpError) Is(target error) bool {
-	switch target {
-	case os.ErrTimeout:
-		return e.Timeout()
-	}
-	return false
-}
-
 // A ParseError is the error type of literal network address parsers.
 type ParseError struct {
 	// Type is the type of string that was expected, such as
@@ -615,14 +607,6 @@ func (e *DNSError) Timeout() bool { return e.IsTimeout }
 // error and return a DNSError for which Temporary returns false.
 func (e *DNSError) Temporary() bool { return e.IsTimeout || e.IsTemporary }
 
-func (e *DNSError) Is(target error) bool {
-	switch target {
-	case os.ErrTimeout:
-		return e.Timeout()
-	}
-	return false
-}
-
 type writerOnly struct {
 	io.Writer
 }
diff --git a/src/net/pipe.go b/src/net/pipe.go
index 5abc4aabe6..9177fc4036 100644
--- a/src/net/pipe.go
+++ b/src/net/pipe.go
@@ -6,7 +6,6 @@ package net
 
 import (
 	"io"
-	"os"
 	"sync"
 	"time"
 )
@@ -85,10 +84,6 @@ func (timeoutError) Error() string   { return "deadline exceeded" }
 func (timeoutError) Timeout() bool   { return true }
 func (timeoutError) Temporary() bool { return true }
 
-func (timeoutError) Is(target error) bool {
-	return target == os.ErrTimeout
-}
-
 type pipeAddr struct{}
 
 func (pipeAddr) Network() string { return "pipe" }
diff --git a/src/net/timeout_test.go b/src/net/timeout_test.go
index 93e46025a2..b4fc2c0198 100644
--- a/src/net/timeout_test.go
+++ b/src/net/timeout_test.go
@@ -7,9 +7,7 @@
 package net
 
 import (
-	"errors"
 	"fmt"
-	"internal/oserror"
 	"internal/poll"
 	"internal/testenv"
 	"io"
@@ -90,9 +88,6 @@ func TestDialTimeout(t *testing.T) {
 			if nerr, ok := err.(Error); !ok || !nerr.Timeout() {
 				t.Fatalf("#%d: %v", i, err)
 			}
-			if !errors.Is(err, oserror.ErrTimeout) {
-				t.Fatalf("#%d: Dial error is not os.ErrTimeout: %v", i, err)
-			}
 		}
 	}
 }
diff --git a/src/net/url/url.go b/src/net/url/url.go
index 3212b9e998..982cfe6c0c 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -13,7 +13,6 @@ package url
 import (
 	"errors"
 	"fmt"
-	"internal/oserror"
 	"sort"
 	"strconv"
 	"strings"
@@ -28,7 +27,13 @@ type Error struct {
 
 func (e *Error) Unwrap() error { return e.Err }
 func (e *Error) Error() string { return e.Op + " " + e.URL + ": " + e.Err.Error() }
-func (e *Error) Timeout() bool { return oserror.IsTimeout(e.Err) }
+
+func (e *Error) Timeout() bool {
+	t, ok := e.Err.(interface {
+		Timeout() bool
+	})
+	return ok && t.Timeout()
+}
 
 func (e *Error) Temporary() bool {
 	t, ok := e.Err.(interface {
diff --git a/src/os/error.go b/src/os/error.go
index 4cf35f2b77..09ba158677 100644
--- a/src/os/error.go
+++ b/src/os/error.go
@@ -22,7 +22,6 @@ var (
 	ErrExist      = errExist()      // "file already exists"
 	ErrNotExist   = errNotExist()   // "file does not exist"
 	ErrClosed     = errClosed()     // "file already closed"
-	ErrTimeout    = errTimeout()    // "deadline exceeded"
 	ErrNoDeadline = errNoDeadline() // "file type does not support deadline"
 )
 
@@ -31,7 +30,6 @@ func errPermission() error { return oserror.ErrPermission }
 func errExist() error      { return oserror.ErrExist }
 func errNotExist() error   { return oserror.ErrNotExist }
 func errClosed() error     { return oserror.ErrClosed }
-func errTimeout() error    { return oserror.ErrTimeout }
 func errNoDeadline() error { return poll.ErrNoDeadline }
 
 type timeout interface {
diff --git a/src/syscall/syscall_js.go b/src/syscall/syscall_js.go
index 6db01c32f1..175fe47fca 100644
--- a/src/syscall/syscall_js.go
+++ b/src/syscall/syscall_js.go
@@ -58,8 +58,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTimeout:
-		return e.Timeout()
 	case oserror.ErrPermission:
 		return e == EACCES || e == EPERM
 	case oserror.ErrExist:
diff --git a/src/syscall/syscall_nacl.go b/src/syscall/syscall_nacl.go
index 33ad8bfab0..e887b1e04e 100644
--- a/src/syscall/syscall_nacl.go
+++ b/src/syscall/syscall_nacl.go
@@ -65,8 +65,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTimeout:
-		return e.Timeout()
 	case oserror.ErrPermission:
 		return e == EACCES || e == EPERM
 	case oserror.ErrExist:
diff --git a/src/syscall/syscall_plan9.go b/src/syscall/syscall_plan9.go
index d1b4bd9bd5..c11f030531 100644
--- a/src/syscall/syscall_plan9.go
+++ b/src/syscall/syscall_plan9.go
@@ -29,8 +29,6 @@ func NewError(s string) error { return ErrorString(s) }
 
 func (e ErrorString) Is(target error) bool {
 	switch target {
-	case oserror.ErrTimeout:
-		return e.Timeout()
 	case oserror.ErrPermission:
 		return checkErrMessageContent(e, "permission denied")
 	case oserror.ErrExist:
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index 4bb7799d53..59c8c34933 100644
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -121,8 +121,6 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTimeout:
-		return e.Timeout()
 	case oserror.ErrPermission:
 		return e == EACCES || e == EPERM
 	case oserror.ErrExist:
diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go
index aa4cfa7243..2e8edc7acc 100644
--- a/src/syscall/syscall_windows.go
+++ b/src/syscall/syscall_windows.go
@@ -115,8 +115,6 @@ const _ERROR_BAD_NETPATH = Errno(53)
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case oserror.ErrTimeout:
-		return e.Timeout()
 	case oserror.ErrPermission:
 		return e == ERROR_ACCESS_DENIED
 	case oserror.ErrExist: