container/check: return error backed by string type

The struct turned out not necessary during initial implementation but was not unwrapped into its single string field. This change replaces it with the underlying string and removes the indirection.

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

container/check/absolute.go

@@ -13,15 +13,18 @@ import (
 )
 
 // AbsoluteError is returned by [NewAbs] and holds the invalid pathname.
-type AbsoluteError struct{ Pathname string }
+type AbsoluteError string
 
-func (e *AbsoluteError) Error() string { return fmt.Sprintf("path %q is not absolute", e.Pathname) }
-func (e *AbsoluteError) Is(target error) bool {
-	var ce *AbsoluteError
+func (e AbsoluteError) Error() string {
+	return fmt.Sprintf("path %q is not absolute", string(e))
+}
+
+func (e AbsoluteError) Is(target error) bool {
+	var ce AbsoluteError
 	if !errors.As(target, &ce) {
 		return errors.Is(target, syscall.EINVAL)
 	}
-	return *e == *ce
+	return e == ce
 }
 
 // Absolute holds a pathname checked to be absolute.
@@ -59,7 +62,7 @@ func (a *Absolute) Is(v *Absolute) bool {
 // NewAbs checks pathname and returns a new [Absolute] if pathname is absolute.
 func NewAbs(pathname string) (*Absolute, error) {
 	if !path.IsAbs(pathname) {
-		return nil, &AbsoluteError{pathname}
+		return nil, AbsoluteError(pathname)
 	}
 	return unsafeAbs(pathname), nil
 }
@@ -90,7 +93,7 @@ func (a *Absolute) GobEncode() ([]byte, error) {
 func (a *Absolute) GobDecode(data []byte) error {
 	pathname := string(data)
 	if !path.IsAbs(pathname) {
-		return &AbsoluteError{pathname}
+		return AbsoluteError(pathname)
 	}
 	a.pathname = unique.Make(pathname)
 	return nil
@@ -108,7 +111,7 @@ func (a *Absolute) UnmarshalJSON(data []byte) error {
 		return err
 	}
 	if !path.IsAbs(pathname) {
-		return &AbsoluteError{pathname}
+		return AbsoluteError(pathname)
 	}
 	a.pathname = unique.Make(pathname)
 	return nil