cmd/go/internal/lockedfile/internal/filelock: use errors.ErrUnsupported

All platform specific errors are now covered by errors.ErrUnsupported.

Updates #41198

Change-Id: Ia9c0cad7c493305835bd5a1f349446cec409f686
Reviewed-on: https://go-review.googlesource.com/c/go/+/476917
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>

src/cmd/go/internal/lockedfile/internal/filelock/filelock.go

@@ -10,7 +10,6 @@ package filelock
 import (
 	"errors"
 	"io/fs"
-	"os"
 )
 
 // A File provides the minimal set of methods required to lock an open file.
@@ -78,22 +77,7 @@ func (lt lockType) String() string {
 
 // IsNotSupported returns a boolean indicating whether the error is known to
 // report that a function is not supported (possibly for a specific input).
-// It is satisfied by ErrNotSupported as well as some syscall errors.
+// It is satisfied by errors.ErrUnsupported as well as some syscall errors.
 func IsNotSupported(err error) bool {
-	return isNotSupported(underlyingError(err))
-}
-
-var ErrNotSupported = errors.New("operation not supported")
-
-// underlyingError returns the underlying error for known os error types.
-func underlyingError(err error) error {
-	switch err := err.(type) {
-	case *fs.PathError:
-		return err.Err
-	case *os.LinkError:
-		return err.Err
-	case *os.SyscallError:
-		return err.Err
-	}
-	return err
+	return errors.Is(err, errors.ErrUnsupported)
 }

src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go

@@ -208,7 +208,3 @@ func setlkw(fd uintptr, lt lockType) error {
 		}
 	}
 }
-
-func isNotSupported(err error) bool {
-	return err == syscall.ENOSYS || err == syscall.ENOTSUP || err == syscall.EOPNOTSUPP || err == ErrNotSupported
-}

src/cmd/go/internal/lockedfile/internal/filelock/filelock_other.go

@@ -6,7 +6,10 @@
 
 package filelock
 
-import "io/fs"
+import (
+	"errors"
+	"io/fs"
+)
 
 type lockType int8
 
@@ -19,7 +22,7 @@ func lock(f File, lt lockType) error {
 	return &fs.PathError{
 		Op:   lt.String(),
 		Path: f.Name(),
-		Err:  ErrNotSupported,
+		Err:  errors.ErrUnsupported,
 	}
 }
 
@@ -27,10 +30,6 @@ func unlock(f File) error {
 	return &fs.PathError{
 		Op:   "Unlock",
 		Path: f.Name(),
-		Err:  ErrNotSupported,
+		Err:  errors.ErrUnsupported,
 	}
 }
-
-func isNotSupported(err error) bool {
-	return err == ErrNotSupported
-}

src/cmd/go/internal/lockedfile/internal/filelock/filelock_unix.go

@@ -38,7 +38,3 @@ func lock(f File, lt lockType) (err error) {
 func unlock(f File) error {
 	return lock(f, syscall.LOCK_UN)
 }
-
-func isNotSupported(err error) bool {
-	return err == syscall.ENOSYS || err == syscall.ENOTSUP || err == syscall.EOPNOTSUPP || err == ErrNotSupported
-}

src/cmd/go/internal/lockedfile/internal/filelock/filelock_windows.go

@@ -55,12 +55,3 @@ func unlock(f File) error {
 	}
 	return nil
 }
-
-func isNotSupported(err error) bool {
-	switch err {
-	case windows.ERROR_NOT_SUPPORTED, windows.ERROR_CALL_NOT_IMPLEMENTED, ErrNotSupported:
-		return true
-	default:
-		return false
-	}
-}