Add unary expressions

Adds parsing of unary plus to the parser.

src/main.rs

@@ -121,6 +121,7 @@ struct Parser<'a> {
 enum Expr<'a> {
 	Literal(&'a str),
 	// Paren(Box<Expr<'a>>),
+	Unary(Token<'a>, Box<Expr<'a>>),
 	Binary(Token<'a>, Box<Expr<'a>>, Box<Expr<'a>>),
 }
 
@@ -177,8 +178,19 @@ impl<'a> Parser<'a> {
 		};
 	}
 
+	fn parse_unary_expr(&mut self) -> Option<Expr<'a>> {
+		return match self.peek()? {
+			token @ Token::Plus => {
+				self.bump();
+				let expr = self.parse_unary_expr()?;
+				Some(Expr::Unary(token, box expr))
+			},
+			_ => self.parse_primary_expr(),
+		};
+	}
+
 	pub fn parse_expr(&mut self, min_precedence: usize) -> Option<Expr<'a>> {
-		let mut lhs = self.parse_primary_expr()?;
+		let mut lhs = self.parse_unary_expr()?;
 
 		loop {
 			let token = self.peek()?;
@@ -199,9 +211,10 @@ impl<'a> Parser<'a> {
 }
 
 fn main() {
+	let inline_source = "3 + +5 * +7;";
 	// let inline_source = "3 + 5 * 7;";
 	// let inline_source = "(3 + 5) + 7;";
-	let inline_source = "3 + (5 + (7 + 11));";
+	// let inline_source = "3 + (5 + (7 + 11));";
 	let mut source = Source::new(inline_source);
 	let mut parser = Parser::new(&mut source);
 	eprintln!("{:?}", parser.parse_expr(0));