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

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

lexer/error.go

@@ -25,17 +25,27 @@ 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:
-		s = append(s, fmt.Sprintf("%s:%v:%v", err.Filename, err.Line, err.Column))
+		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)
+		}
 	case err.Filename != "":
-		s = append(s, err.Filename)
+		prefix = err.Filename
+	}
+
+	if prefix != "" {
+		s = append(s, prefix)
 	}
 
 	if err.Err != nil {
@@ -46,6 +56,10 @@ 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 +64,29 @@ func (p *Position) StepLine() {
 	p.Line++
 	p.Column = 1
 }
+
+// Next returns a new Position one rune forward
+// on the line
+func (p Position) Next() Position {
+	if p.Line == 0 {
+		p.Reset()
+	}
+
+	return Position{
+		Line:   p.Line,
+		Column: p.Column + 1,
+	}
+}
+
+// NextLine returns a new Position at the begining of the next
+// line.
+func (p Position) NextLine() Position {
+	if p.Line == 0 {
+		p.Reset()
+	}
+
+	return Position{
+		Line:   p.Line + 1,
+		Column: 1,
+	}
+}