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

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

lexer/position.go

@@ -84,3 +84,29 @@ func (p *Position) Add(rel Position) {
 		p.Column += rel.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 beginning of the next
+// line.
+func (p Position) NextLine() Position {
+	if p.Line == 0 {
+		p.Reset()
+	}
+
+	return Position{
+		Line:   p.Line + 1,
+		Column: 1,
+	}
+}