Method parse_if_expr

src/parser.rs:420–457

(&mut self)

    }

    fn parse_if_expr(&mut self) -> Option<Expr> {
        if !self.expect_peek(Token::LeftParen) {
            return None;
        }

        self.next_token();

        let expr: Expr = match self.parse_expr(Precedence::Lowest) {
            Some(e) => e,
            None => return None,
        };

        if !self.expect_peek(Token::RightParen) || !self.expect_peek(Token::LeftBrace) {
            return None;
        }

        let cons: Vec<Statement> = self.parse_block_statement();
        let mut alternative: Option<Vec<Statement>> = None;
        if self.peek_token(&Token::Else) {
            self.next_token();

            if self.peek_token(&Token::If) {
                self.next_token();
                let else_if = self.parse_if_expr();
                alternative = Some(vec![Statement::Expression(else_if.unwrap())]);
            } else if !self.expect_peek(Token::LeftBrace) {
                return None;
            } else {
                alternative = Some(self.parse_block_statement())
            };
        }

        Some(Expr::If {
            cond: Box::new(expr),
            then: Box::new(cons),
            else_: alternative,
        })
    }

    fn parse_fn_expr(&mut self) -> Option<Expr> {
        if !self.expect_peek(Token::LeftParen) {