rust/src/parser/event.rs
Aleksey Kladov ac932df22a reformat
2018-02-09 22:55:50 +03:00

150 lines
4.6 KiB
Rust

use {ErrorMsg, File, FileBuilder, Sink, SyntaxKind, TextUnit, Token};
use syntax_kinds::TOMBSTONE;
use super::is_insignificant;
/// `Parser` produces a flat list of `Event`s.
/// They are converted to a tree-structure in
/// a separate pass, via `TreeBuilder`.
#[derive(Debug)]
pub(crate) enum Event {
/// This event signifies the start of the node.
/// It should be either abandoned (in which case the
/// `kind` is `TOMBSTONE`, and the event is ignored),
/// or completed via a `Finish` event.
///
/// All tokens between a `Start` and a `Finish` would
/// become the children of the respective node.
///
/// For left-recursive syntactic constructs, the parser produces
/// a child node before it sees a parent. `forward_parent`
/// exists to allow to tweak parent-child relationships.
///
/// Consider this path
///
/// foo::bar
///
/// The events for it would look like this:
///
///
/// START(PATH) IDENT('foo') FINISH START(PATH) COLONCOLON IDENT('bar') FINISH
/// | /\
/// | |
/// +------forward-parent------+
///
/// And the tree would look like this
///
/// +--PATH---------+
/// | | |
/// | | |
/// | '::' 'bar'
/// |
/// PATH
/// |
/// 'foo'
///
/// See also `CompleteMarker::precede`.
Start {
kind: SyntaxKind,
forward_parent: Option<u32>,
},
/// Complete the previous `Start` event
Finish,
/// Produce a single leaf-element.
/// `n_raw_tokens` is used to glue complex contextual tokens.
/// For example, lexer tokenizes `>>` as `>`, `>`, and
/// `n_raw_tokens = 2` is used to produced a single `>>`.
Token {
kind: SyntaxKind,
n_raw_tokens: u8,
},
Error {
message: String,
},
}
pub(super) fn to_file(text: String, tokens: &[Token], events: Vec<Event>) -> File {
let mut builder = FileBuilder::new(text);
let mut idx = 0;
let mut holes = Vec::new();
let mut forward_parents = Vec::new();
for (i, event) in events.iter().enumerate() {
if holes.last() == Some(&i) {
holes.pop();
continue;
}
match event {
&Event::Start {
kind: TOMBSTONE, ..
} => (),
&Event::Start { .. } => {
forward_parents.clear();
let mut idx = i;
loop {
let (kind, fwd) = match events[idx] {
Event::Start {
kind,
forward_parent,
} => (kind, forward_parent),
_ => unreachable!(),
};
forward_parents.push((idx, kind));
if let Some(fwd) = fwd {
idx += fwd as usize;
} else {
break;
}
}
for &(idx, kind) in forward_parents.iter().into_iter().rev() {
builder.start_internal(kind);
holes.push(idx);
}
holes.pop();
}
&Event::Finish => {
while idx < tokens.len() {
let token = tokens[idx];
if is_insignificant(token.kind) {
idx += 1;
builder.leaf(token.kind, token.len);
} else {
break;
}
}
builder.finish_internal()
}
&Event::Token {
kind,
mut n_raw_tokens,
} => {
// FIXME: currently, we attach whitespace to some random node
// this should be done in a sensible manner instead
loop {
let token = tokens[idx];
if !is_insignificant(token.kind) {
break;
}
builder.leaf(token.kind, token.len);
idx += 1
}
let mut len = TextUnit::new(0);
for _ in 0..n_raw_tokens {
len += tokens[idx].len;
idx += 1;
}
builder.leaf(kind, len);
}
&Event::Error { ref message } => builder.error(ErrorMsg {
message: message.clone(),
}),
}
}
builder.finish()
}