lexer: introduce Position.Next()/Position.NextLine() factories

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/error.go

@@ -25,27 +25,17 @@ type Error struct {
 	Column   int
 
 	Content string
-	Hint    string
 	Err     error
 }
 
 func (err Error) Error() string {
 	var s []string
-	var prefix string
 
 	switch {
 	case err.Line > 0 || err.Column > 0:
-		if err.Filename != "" {
-			prefix = fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column)
-		} else {
-			prefix = fmt.Sprintf("%v:%v", err.Line, err.Column)
-		}
+		s = append(s, fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column))
 	case err.Filename != "":
-		prefix = err.Filename
-	}
-
-	if prefix != "" {
-		s = append(s, prefix)
+		s = append(s, err.Filename)
 	}
 
 	if err.Err != nil {
@@ -56,10 +46,6 @@ func (err Error) Error() string {
 		s = append(s, fmt.Sprintf("%q", err.Content))
 	}
 
-	if err.Hint != "" {
-		s = append(s, err.Hint)
-	}
-
 	return strings.Join(s, ": ")
 }