Replace OptionalPath.valid flag by checking the path itself.

Test: m nothing
Change-Id: Iaf7655e4676d2beeb7c7ac3bcba11a7dad4a01a3

android/paths.go

@@ -263,27 +263,23 @@ func ResPathWithName(ctx ModuleOutPathContext, p Path, name string) ModuleResPat
 
 // OptionalPath is a container that may or may not contain a valid Path.
 type OptionalPath struct {
-	valid bool
-	path  Path
+	path Path // nil if invalid.
 }
 
 // OptionalPathForPath returns an OptionalPath containing the path.
 func OptionalPathForPath(path Path) OptionalPath {
-	if path == nil {
-		return OptionalPath{}
-	}
-	return OptionalPath{valid: true, path: path}
+	return OptionalPath{path: path}
 }
 
 // Valid returns whether there is a valid path
 func (p OptionalPath) Valid() bool {
-	return p.valid
+	return p.path != nil
 }
 
 // Path returns the Path embedded in this OptionalPath. You must be sure that
 // there is a valid path, since this method will panic if there is not.
 func (p OptionalPath) Path() Path {
-	if !p.valid {
+	if p.path == nil {
 		panic("Requesting an invalid path")
 	}
 	return p.path
@@ -294,7 +290,7 @@ func (p OptionalPath) Path() Path {
 // It returns nil if this is not valid, or a single length slice containing the Path embedded in
 // this OptionalPath.
 func (p OptionalPath) AsPaths() Paths {
-	if !p.valid {
+	if p.path == nil {
 		return nil
 	}
 	return Paths{p.path}
@@ -303,7 +299,7 @@ func (p OptionalPath) AsPaths() Paths {
 // RelativeToTop returns an OptionalPath with the path that was embedded having been replaced by the
 // result of calling Path.RelativeToTop on it.
 func (p OptionalPath) RelativeToTop() OptionalPath {
-	if !p.valid {
+	if p.path == nil {
 		return p
 	}
 	p.path = p.path.RelativeToTop()
@@ -312,7 +308,7 @@ func (p OptionalPath) RelativeToTop() OptionalPath {
 
 // String returns the string version of the Path, or "" if it isn't valid.
 func (p OptionalPath) String() string {
-	if p.valid {
+	if p.path != nil {
 		return p.path.String()
 	} else {
 		return ""