Replace shouldSkipSystemError with map lookup

contains.go

@@ -45,21 +45,8 @@ func Contains(fs Stater, p, prefix string) (bool, error) {
 			}
 			// Ignore some syscall.Errnos.
 			if errno, ok := err.(syscall.Errno); ok {
-				switch errno {
-				case syscall.ELOOP:
+				if _, ignore := ignoreErrnoInContains[errno]; ignore {
 					goto TryParent
-				case syscall.EMLINK:
-					goto TryParent
-				case syscall.ENAMETOOLONG:
-					goto TryParent
-				case syscall.ENOENT:
-					goto TryParent
-				case syscall.EOVERFLOW:
-					goto TryParent
-				default:
-					if shouldSkipSystemError(errno) {
-						goto TryParent
-					}
 				}
 			}
 			return false, err

posix.go

@@ -7,11 +7,15 @@ import "syscall"
 // HostOSFS is the host-specific OSFS.
 var HostOSFS = OSFS
 
+var ignoreErrnoInContains = map[syscall.Errno]struct{}{
+	syscall.ELOOP:        {},
+	syscall.EMLINK:       {},
+	syscall.ENAMETOOLONG: {},
+	syscall.ENOENT:       {},
+	syscall.EOVERFLOW:    {},
+}
+
 // relativizePath, on POSIX systems, just returns path.
 func relativizePath(path string) string {
 	return path
 }
-
-func shouldSkipSystemError(err syscall.Errno) bool {
-	return false
-}

windows.go

@@ -12,6 +12,15 @@ import (
 // HostOSFS is the host-specific OSFS.
 var HostOSFS = WindowsOSFS{}
 
+var ignoreErrnoInContains = map[syscall.Errno]struct{}{
+	syscall.ELOOP:                       {},
+	syscall.EMLINK:                      {},
+	syscall.ENAMETOOLONG:                {},
+	syscall.ENOENT:                      {},
+	syscall.EOVERFLOW:                   {},
+	windows.ERROR_CANT_RESOLVE_FILENAME: {},
+}
+
 // relativizePath, on Windows, strips any leading volume name from path and
 // replaces backslashes with slashes.
 func relativizePath(path string) string {
@@ -20,7 +29,3 @@ func relativizePath(path string) string {
 	}
 	return filepath.ToSlash(path)
 }
-
-func shouldSkipSystemError(err syscall.Errno) bool {
-	return err == windows.ERROR_CANT_RESOLVE_FILENAME
-}