all: apply modernisers

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/finalise.go

@@ -58,8 +58,7 @@ func (k *outcome) finalise(
 	supp := make([]string, len(config.Groups))
 	for i, name := range config.Groups {
 		if gid, err := k.lookupGroupId(name); err != nil {
-			var unknownGroupError user.UnknownGroupError
-			if errors.As(err, &unknownGroupError) {
+			if unknownGroupError, ok := errors.AsType[user.UnknownGroupError](err); ok {
 				return newWithMessageError(fmt.Sprintf("unknown group %q", name), unknownGroupError)
 			} else {
 				return &hst.AppError{Step: "look up group by name", Err: err, Msg: err.Error()}

internal/outcome/hsu.go

@@ -51,18 +51,16 @@ func (h *Hsu) ID() (int, error) {
 		cmd.Stderr = os.Stderr // pass through fatal messages
 		cmd.Env = make([]string, 0)
 		cmd.Dir = fhs.Root
-		var (
-			p         []byte
-			exitError *exec.ExitError
-		)
-
+		var p []byte
 		const step = "obtain uid from hsu"
 		if p, h.idErr = h.k.cmdOutput(cmd); h.idErr == nil {
 			h.id, h.idErr = strconv.Atoi(string(p))
 			if h.idErr != nil {
 				h.idErr = &hst.AppError{Step: step, Err: h.idErr, Msg: "invalid uid string from hsu"}
 			}
-		} else if errors.As(h.idErr, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
+		} else if exitError, ok := errors.AsType[*exec.ExitError](h.idErr); ok &&
+			exitError != nil &&
+			exitError.ExitCode() == 1 {
 			// hsu prints an error message in this case
 			h.idErr = &hst.AppError{Step: step, Err: ErrHsuAccess}
 		} else if errors.Is(h.idErr, os.ErrNotExist) {

internal/outcome/process.go

@@ -328,11 +328,11 @@ func (k *outcome) main(msg message.Msg, identifierFd int) {
 				}
 
 				if err := k.sys.Revert((*system.Criteria)(&ec)); err != nil {
-					var joinError interface {
+					joinError, ok := errors.AsType[interface {
 						Unwrap() []error
 						error
-					}
-					if !errors.As(err, &joinError) || joinError == nil {
+					}](err)
+					if !ok || joinError == nil {
 						perror(err, "revert system setup")
 					} else {
 						for _, v := range joinError.Unwrap() {

internal/outcome/shim.go

@@ -390,8 +390,8 @@ func shimEntrypoint(k syscallDispatcher) {
 	if err := k.containerWait(z); err != nil {
 		sp.destroy()
 
-		var exitError *exec.ExitError
-		if !errors.As(err, &exitError) {
+		exitError, ok := errors.AsType[*exec.ExitError](err)
+		if !ok {
 			if errors.Is(err, context.Canceled) {
 				k.exit(hst.ExitCancel)
 			}