Merge pull request 'lexer: introduce Position.Add()' (#13)

Reviewed-on: #13

lexer/error.go

@@ -25,17 +25,29 @@ type Error struct {
 	Column   int
 
 	Content string
+	Hint    string
 	Err     error
 }
 
+func (err Error) prefix() string {
+	switch {
+	case err.Line > 0 || err.Column > 0:
+		if err.Filename != "" {
+			return fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column)
+		}
+
+		return fmt.Sprintf("%v:%v", err.Line, err.Column)
+	default:
+		return err.Filename
+	}
+}
+
 func (err Error) Error() string {
 	var s []string
 
-	switch {
-	case err.Line > 0 || err.Column > 0:
-		s = append(s, fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column))
-	case err.Filename != "":
-		s = append(s, err.Filename)
+	prefix := err.prefix()
+	if prefix != "" {
+		s = append(s, prefix)
 	}
 
 	if err.Err != nil {
@@ -46,6 +58,10 @@ 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, ": ")
 }
 

lexer/position.go

@@ -64,3 +64,23 @@ func (p *Position) StepLine() {
 	p.Line++
 	p.Column = 1
 }
+
+// Add adds a relative position considering
+// potential new lines
+func (p *Position) Add(rel Position) {
+	if p.Line == 0 {
+		p.Reset()
+	}
+
+	switch {
+	case rel.Line == 0:
+		// nothing
+	case rel.Line > 1:
+		// includes new lines
+		p.Line += rel.Line - 1
+		p.Column = rel.Column
+	default:
+		// same line
+		p.Column += rel.Column - 1
+	}
+}