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Diffstat (limited to 'crates/ra_syntax/src/parser_impl/event.rs')
-rw-r--r-- | crates/ra_syntax/src/parser_impl/event.rs | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/crates/ra_syntax/src/parser_impl/event.rs b/crates/ra_syntax/src/parser_impl/event.rs new file mode 100644 index 000000000..9fd56b996 --- /dev/null +++ b/crates/ra_syntax/src/parser_impl/event.rs | |||
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1 | //! This module provides a way to construct a `File`. | ||
2 | //! It is intended to be completely decoupled from the | ||
3 | //! parser, so as to allow to evolve the tree representation | ||
4 | //! and the parser algorithm independently. | ||
5 | //! | ||
6 | //! The `Sink` trait is the bridge between the parser and the | ||
7 | //! tree builder: the parser produces a stream of events like | ||
8 | //! `start node`, `finish node`, and `FileBuilder` converts | ||
9 | //! this stream to a real tree. | ||
10 | use std::mem; | ||
11 | use { | ||
12 | lexer::Token, | ||
13 | parser_impl::Sink, | ||
14 | SyntaxKind::{self, TOMBSTONE}, | ||
15 | }; | ||
16 | |||
17 | |||
18 | /// `Parser` produces a flat list of `Event`s. | ||
19 | /// They are converted to a tree-structure in | ||
20 | /// a separate pass, via `TreeBuilder`. | ||
21 | #[derive(Debug)] | ||
22 | pub(crate) enum Event { | ||
23 | /// This event signifies the start of the node. | ||
24 | /// It should be either abandoned (in which case the | ||
25 | /// `kind` is `TOMBSTONE`, and the event is ignored), | ||
26 | /// or completed via a `Finish` event. | ||
27 | /// | ||
28 | /// All tokens between a `Start` and a `Finish` would | ||
29 | /// become the children of the respective node. | ||
30 | /// | ||
31 | /// For left-recursive syntactic constructs, the parser produces | ||
32 | /// a child node before it sees a parent. `forward_parent` | ||
33 | /// exists to allow to tweak parent-child relationships. | ||
34 | /// | ||
35 | /// Consider this path | ||
36 | /// | ||
37 | /// foo::bar | ||
38 | /// | ||
39 | /// The events for it would look like this: | ||
40 | /// | ||
41 | /// | ||
42 | /// START(PATH) IDENT('foo') FINISH START(PATH) COLONCOLON IDENT('bar') FINISH | ||
43 | /// | /\ | ||
44 | /// | | | ||
45 | /// +------forward-parent------+ | ||
46 | /// | ||
47 | /// And the tree would look like this | ||
48 | /// | ||
49 | /// +--PATH---------+ | ||
50 | /// | | | | ||
51 | /// | | | | ||
52 | /// | '::' 'bar' | ||
53 | /// | | ||
54 | /// PATH | ||
55 | /// | | ||
56 | /// 'foo' | ||
57 | /// | ||
58 | /// See also `CompletedMarker::precede`. | ||
59 | Start { | ||
60 | kind: SyntaxKind, | ||
61 | forward_parent: Option<u32>, | ||
62 | }, | ||
63 | |||
64 | /// Complete the previous `Start` event | ||
65 | Finish, | ||
66 | |||
67 | /// Produce a single leaf-element. | ||
68 | /// `n_raw_tokens` is used to glue complex contextual tokens. | ||
69 | /// For example, lexer tokenizes `>>` as `>`, `>`, and | ||
70 | /// `n_raw_tokens = 2` is used to produced a single `>>`. | ||
71 | Token { | ||
72 | kind: SyntaxKind, | ||
73 | n_raw_tokens: u8, | ||
74 | }, | ||
75 | |||
76 | Error { | ||
77 | msg: String, | ||
78 | }, | ||
79 | } | ||
80 | |||
81 | |||
82 | pub(super) fn process<'a, S: Sink<'a>>(builder: &mut S, tokens: &[Token], mut events: Vec<Event>) { | ||
83 | fn tombstone() -> Event { | ||
84 | Event::Start { kind: TOMBSTONE, forward_parent: None } | ||
85 | } | ||
86 | let eat_ws = |idx: &mut usize, builder: &mut S| { | ||
87 | while let Some(token) = tokens.get(*idx) { | ||
88 | if !token.kind.is_trivia() { | ||
89 | break; | ||
90 | } | ||
91 | builder.leaf(token.kind, token.len); | ||
92 | *idx += 1 | ||
93 | } | ||
94 | }; | ||
95 | |||
96 | let events: &mut [Event] = &mut events; | ||
97 | let mut depth = 0; | ||
98 | let mut forward_parents = Vec::new(); | ||
99 | let mut next_tok_idx = 0; | ||
100 | for i in 0..events.len() { | ||
101 | match mem::replace(&mut events[i], tombstone()) { | ||
102 | Event::Start { | ||
103 | kind: TOMBSTONE, .. | ||
104 | } => (), | ||
105 | |||
106 | Event::Start { kind, forward_parent } => { | ||
107 | forward_parents.push(kind); | ||
108 | let mut idx = i; | ||
109 | let mut fp = forward_parent; | ||
110 | while let Some(fwd) = fp { | ||
111 | idx += fwd as usize; | ||
112 | fp = match mem::replace(&mut events[idx], tombstone()) { | ||
113 | Event::Start { | ||
114 | kind, | ||
115 | forward_parent, | ||
116 | } => { | ||
117 | forward_parents.push(kind); | ||
118 | forward_parent | ||
119 | }, | ||
120 | _ => unreachable!(), | ||
121 | }; | ||
122 | } | ||
123 | for kind in forward_parents.drain(..).rev() { | ||
124 | if depth > 0 { | ||
125 | eat_ws(&mut next_tok_idx, builder); | ||
126 | } | ||
127 | depth += 1; | ||
128 | builder.start_internal(kind); | ||
129 | } | ||
130 | } | ||
131 | Event::Finish => { | ||
132 | depth -= 1; | ||
133 | if depth == 0 { | ||
134 | eat_ws(&mut next_tok_idx, builder); | ||
135 | } | ||
136 | |||
137 | builder.finish_internal(); | ||
138 | } | ||
139 | Event::Token { | ||
140 | kind, | ||
141 | mut n_raw_tokens, | ||
142 | } => { | ||
143 | eat_ws(&mut next_tok_idx, builder); | ||
144 | let mut len = 0.into(); | ||
145 | for _ in 0..n_raw_tokens { | ||
146 | len += tokens[next_tok_idx].len; | ||
147 | next_tok_idx += 1; | ||
148 | } | ||
149 | builder.leaf(kind, len); | ||
150 | } | ||
151 | Event::Error { msg } => builder.error(msg), | ||
152 | } | ||
153 | } | ||
154 | } | ||