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use drop_bomb::DropBomb;
use crate::{
parser_impl::ParserImpl,
token_set::TokenSet,
SyntaxKind::{self, ERROR},
};
/// `Parser` struct provides the low-level API for
/// navigating through the stream of tokens and
/// constructing the parse tree. The actual parsing
/// happens in the `grammar` module.
///
/// However, the result of this `Parser` is not a real
/// tree, but rather a flat stream of events of the form
/// "start expression, consume number literal,
/// finish expression". See `Event` docs for more.
pub(crate) struct Parser<'t>(pub(super) ParserImpl<'t>);
impl<'t> Parser<'t> {
/// Returns the kind of the current token.
/// If parser has already reached the end of input,
/// the special `EOF` kind is returned.
pub(crate) fn current(&self) -> SyntaxKind {
self.nth(0)
}
/// Lookahead operation: returns the kind of the next nth
/// token.
pub(crate) fn nth(&self, n: u32) -> SyntaxKind {
self.0.nth(n)
}
/// Checks if the current token is `kind`.
pub(crate) fn at(&self, kind: SyntaxKind) -> bool {
self.current() == kind
}
/// Checks if the current token is in `kinds`.
pub(crate) fn at_ts(&self, kinds: TokenSet) -> bool {
kinds.contains(self.current())
}
pub(crate) fn next2(&self) -> Option<(SyntaxKind, SyntaxKind)> {
self.0.next2()
}
pub(crate) fn next3(&self) -> Option<(SyntaxKind, SyntaxKind, SyntaxKind)> {
self.0.next3()
}
/// Checks if the current token is contextual keyword with text `t`.
pub(crate) fn at_contextual_kw(&self, t: &str) -> bool {
self.0.at_kw(t)
}
/// Starts a new node in the syntax tree. All nodes and tokens
/// consumed between the `start` and the corresponding `Marker::complete`
/// belong to the same node.
pub(crate) fn start(&mut self) -> Marker {
Marker::new(self.0.start())
}
/// Advances the parser by one token unconditionally.
pub(crate) fn bump(&mut self) {
self.0.bump();
}
/// Advances the parser by one token, remapping its kind.
/// This is useful to create contextual keywords from
/// identifiers. For example, the lexer creates an `union`
/// *identifier* token, but the parser remaps it to the
/// `union` keyword, and keyword is what ends up in the
/// final tree.
pub(crate) fn bump_remap(&mut self, kind: SyntaxKind) {
self.0.bump_remap(kind);
}
/// Advances the parser by `n` tokens, remapping its kind.
/// This is useful to create compound tokens from parts. For
/// example, an `<<` token is two consecutive remapped `<` tokens
pub(crate) fn bump_compound(&mut self, kind: SyntaxKind, n: u8) {
self.0.bump_compound(kind, n);
}
/// Emit error with the `message`
/// TODO: this should be much more fancy and support
/// structured errors with spans and notes, like rustc
/// does.
pub(crate) fn error<T: Into<String>>(&mut self, message: T) {
self.0.error(message.into())
}
/// Consume the next token if `kind` matches.
pub(crate) fn eat(&mut self, kind: SyntaxKind) -> bool {
if !self.at(kind) {
return false;
}
self.bump();
true
}
/// Consume the next token if it is `kind` or emit an error
/// otherwise.
pub(crate) fn expect(&mut self, kind: SyntaxKind) -> bool {
if self.eat(kind) {
return true;
}
self.error(format!("expected {:?}", kind));
false
}
/// Create an error node and consume the next token.
pub(crate) fn err_and_bump(&mut self, message: &str) {
self.err_recover(message, TokenSet::empty());
}
/// Create an error node and consume the next token.
pub(crate) fn err_recover(&mut self, message: &str, recovery: TokenSet) {
if self.at(SyntaxKind::L_CURLY) || self.at(SyntaxKind::R_CURLY) || self.at_ts(recovery) {
self.error(message);
} else {
let m = self.start();
self.error(message);
self.bump();
m.complete(self, ERROR);
};
}
}
/// See `Parser::start`.
pub(crate) struct Marker {
pos: u32,
bomb: DropBomb,
}
impl Marker {
fn new(pos: u32) -> Marker {
Marker {
pos,
bomb: DropBomb::new("Marker must be either completed or abandoned"),
}
}
/// Finishes the syntax tree node and assigns `kind` to it,
/// and mark the create a `CompletedMarker` for possible future
/// operation like `.precede()` to deal with forward_parent.
pub(crate) fn complete(mut self, p: &mut Parser, kind: SyntaxKind) -> CompletedMarker {
self.bomb.defuse();
p.0.complete(self.pos, kind);
CompletedMarker::new(self.pos, kind)
}
/// Abandons the syntax tree node. All its children
/// are attached to its parent instead.
pub(crate) fn abandon(mut self, p: &mut Parser) {
self.bomb.defuse();
p.0.abandon(self.pos);
}
}
pub(crate) struct CompletedMarker(u32, SyntaxKind);
impl CompletedMarker {
fn new(pos: u32, kind: SyntaxKind) -> Self {
CompletedMarker(pos, kind)
}
/// This method allows to create a new node which starts
/// *before* the current one. That is, parser could start
/// node `A`, then complete it, and then after parsing the
/// whole `A`, decide that it should have started some node
/// `B` before starting `A`. `precede` allows to do exactly
/// that. See also docs about `forward_parent` in `Event::Start`.
///
/// Given completed events `[START, FINISH]` and its corresponding
/// `CompletedMarker(pos: 0, _)`.
/// Append a new `START` events as `[START, FINISH, NEWSTART]`,
/// then mark `NEWSTART` as `START`'s parent with saving its relative
/// distance to `NEWSTART` into forward_parent(=2 in this case);
pub(crate) fn precede(self, p: &mut Parser) -> Marker {
Marker::new(p.0.precede(self.0))
}
pub(crate) fn kind(&self) -> SyntaxKind {
self.1
}
}
|
