rowan 0.16.1

Library for generic lossless syntax trees
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152

//! Example that takes the input
//! 1 + 2 * 3 + 4
//! and builds the tree
//! - Marker(Root)
//!   - Marker(Operation)
//!     - Marker(Operation)
//!       - "1" Token(Number)
//!       - "+" Token(Add)
//!       - Marker(Operation)
//!         - "2" Token(Number)
//!         - "*" Token(Mul)
//!         - "3" Token(Number)
//!     - "+" Token(Add)
//!     - "4" Token(Number)

use rowan::{GreenNodeBuilder, NodeOrToken};
use std::iter::Peekable;

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(non_camel_case_types)]
#[repr(u16)]
enum SyntaxKind {
    WHITESPACE = 0,

    ADD,
    SUB,
    MUL,
    DIV,

    NUMBER,
    ERROR,
    OPERATION,
    ROOT,
}
use SyntaxKind::*;

impl From<SyntaxKind> for rowan::SyntaxKind {
    fn from(kind: SyntaxKind) -> Self {
        Self(kind as u16)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
enum Lang {}
impl rowan::Language for Lang {
    type Kind = SyntaxKind;
    fn kind_from_raw(raw: rowan::SyntaxKind) -> Self::Kind {
        assert!(raw.0 <= ROOT as u16);
        unsafe { std::mem::transmute::<u16, SyntaxKind>(raw.0) }
    }
    fn kind_to_raw(kind: Self::Kind) -> rowan::SyntaxKind {
        kind.into()
    }
}

type SyntaxNode = rowan::SyntaxNode<Lang>;
#[allow(unused)]
type SyntaxToken = rowan::SyntaxToken<Lang>;
#[allow(unused)]
type SyntaxElement = rowan::NodeOrToken<SyntaxNode, SyntaxToken>;

struct Parser<I: Iterator<Item = (SyntaxKind, String)>> {
    builder: GreenNodeBuilder<'static>,
    iter: Peekable<I>,
}
impl<I: Iterator<Item = (SyntaxKind, String)>> Parser<I> {
    fn peek(&mut self) -> Option<SyntaxKind> {
        while self.iter.peek().map(|&(t, _)| t == WHITESPACE).unwrap_or(false) {
            self.bump();
        }
        self.iter.peek().map(|&(t, _)| t)
    }
    fn bump(&mut self) {
        if let Some((token, string)) = self.iter.next() {
            self.builder.token(token.into(), string.as_str());
        }
    }
    fn parse_val(&mut self) {
        match self.peek() {
            Some(NUMBER) => self.bump(),
            _ => {
                self.builder.start_node(ERROR.into());
                self.bump();
                self.builder.finish_node();
            }
        }
    }
    fn handle_operation(&mut self, tokens: &[SyntaxKind], next: fn(&mut Self)) {
        let checkpoint = self.builder.checkpoint();
        next(self);
        while self.peek().map(|t| tokens.contains(&t)).unwrap_or(false) {
            self.builder.start_node_at(checkpoint, OPERATION.into());
            self.bump();
            next(self);
            self.builder.finish_node();
        }
    }
    fn parse_mul(&mut self) {
        self.handle_operation(&[MUL, DIV], Self::parse_val)
    }
    fn parse_add(&mut self) {
        self.handle_operation(&[ADD, SUB], Self::parse_mul)
    }
    fn parse(mut self) -> SyntaxNode {
        self.builder.start_node(ROOT.into());
        self.parse_add();
        self.builder.finish_node();

        SyntaxNode::new_root(self.builder.finish())
    }
}

fn print(indent: usize, element: SyntaxElement) {
    let kind: SyntaxKind = element.kind();
    print!("{:indent$}", "", indent = indent);
    match element {
        NodeOrToken::Node(node) => {
            println!("- {:?}", kind);
            for child in node.children_with_tokens() {
                print(indent + 2, child);
            }
        }

        NodeOrToken::Token(token) => println!("- {:?} {:?}", token.text(), kind),
    }
}

fn main() {
    let ast = Parser {
        builder: GreenNodeBuilder::new(),
        iter: vec![
            // 1 + 2 * 3 + 4
            (NUMBER, "1".into()),
            (WHITESPACE, " ".into()),
            (ADD, "+".into()),
            (WHITESPACE, " ".into()),
            (NUMBER, "2".into()),
            (WHITESPACE, " ".into()),
            (MUL, "*".into()),
            (WHITESPACE, " ".into()),
            (NUMBER, "3".into()),
            (WHITESPACE, " ".into()),
            (ADD, "+".into()),
            (WHITESPACE, " ".into()),
            (NUMBER, "4".into()),
        ]
        .into_iter()
        .peekable(),
    }
    .parse();
    print(0, ast.into());
}