rsexpr/
parser.rs

1use std::{unreachable, vec};
2
3use crate::{lex::Token, Error, ParenKind, Sexpr, Sexprs};
4
5pub(crate) struct Parser<'src> {
6    iter: vec::IntoIter<Token<'src>>,
7    curr_tok: Option<Token<'src>>,
8    errors: Vec<Error>,
9}
10
11impl<'src> Parser<'src> {
12    pub fn parse(tokens: Vec<Token<'src>>) -> (Sexprs<'src>, Vec<Error>) {
13        let mut iter = tokens.into_iter();
14        let mut parser = Self {
15            curr_tok: iter.next(),
16            iter,
17            errors: vec![],
18        };
19
20        let mut sexprs = Sexprs::new();
21        while let Some(sexpr) = parser.sexpr() {
22            sexprs.push(sexpr);
23        }
24
25        if let Some(tok) = parser.curr_tok {
26            let paren_kind = match tok {
27                Token::RParen => ParenKind::Round,
28                Token::RBrack => ParenKind::Square,
29                _ => unreachable!("`sexpr` function only returns `None` for above token types"),
30            };
31            parser.errors.push(Error::ExtraClosingParen(paren_kind));
32        }
33
34        (sexprs, parser.errors)
35    }
36
37    fn next(&mut self) {
38        self.curr_tok = self.iter.next();
39    }
40
41    fn expect_closing(&mut self, expected: ParenKind) {
42        match &self.curr_tok {
43            Some(tok) if tok == &Token::from(&expected) => self.next(),
44            Some(_) | None => self.errors.push(Error::MissingClosingParen(expected)),
45        }
46    }
47
48    fn sexpr(&mut self) -> Option<Sexpr<'src>> {
49        match self.curr_tok.take()? {
50            Token::LParen => Some(self.list()),
51            Token::LBrack => Some(self.group()),
52            Token::String(string) => {
53                self.next();
54                Some(Sexpr::String(string))
55            }
56            Token::Atom(atom) => {
57                self.next();
58                Some(Sexpr::Atom(atom))
59            }
60            #[cfg(feature = "comments")]
61            Token::Comment(comment) => {
62                self.next();
63                Some(Sexpr::Comment(comment))
64            }
65            tok @ (Token::RParen | Token::RBrack) => {
66                self.curr_tok = Some(tok);
67                None
68            }
69        }
70    }
71
72    fn list(&mut self) -> Sexpr<'src> {
73        self.next(); // skip opening paren
74
75        let mut children = Sexprs::new();
76        while let Some(child) = self.sexpr() {
77            children.push(child);
78        }
79
80        self.expect_closing(ParenKind::Round);
81
82        Sexpr::List(children)
83    }
84
85    fn group(&mut self) -> Sexpr<'src> {
86        self.next(); // skip opening bracket
87
88        let mut children = Sexprs::new();
89        while let Some(child) = self.sexpr() {
90            children.push(child);
91        }
92
93        self.expect_closing(ParenKind::Square);
94
95        Sexpr::Group(children)
96    }
97}
98
99#[cfg(test)]
100mod tests {
101    use super::*;
102
103    #[test]
104    fn nesting() {
105        assert_eq!(
106            Parser::parse(vec![
107                Token::LParen,
108                Token::LParen,
109                Token::LBrack,
110                Token::LParen,
111                Token::RParen,
112                Token::RBrack,
113                Token::RParen,
114                Token::RParen
115            ])
116            .0,
117            vec![Sexpr::List(
118                vec![Sexpr::List(
119                    vec![Sexpr::Group(vec![Sexpr::List(vec![].into())].into())].into()
120                )]
121                .into()
122            )]
123            .into(),
124        );
125    }
126
127    #[test]
128    #[cfg(feature = "comments")]
129    fn comments() {
130        assert_eq!(
131            Parser::parse(vec![Token::Comment(b"; comment")]).0,
132            vec![Sexpr::Comment(b"; comment")].into(),
133        );
134        assert_eq!(
135            Parser::parse(vec![
136                Token::LParen,
137                Token::Comment(b"; comment"),
138                Token::Atom(b"atom"),
139                Token::RParen,
140            ])
141            .0,
142            vec![Sexpr::List(
143                vec![Sexpr::Comment(b"; comment"), Sexpr::Atom(b"atom"),].into()
144            )]
145            .into(),
146        );
147    }
148}
rsexpr/parser.rs

rsexpr/
parser.rs
