rust/crates/parser/src/shortcuts.rs

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//! Shortcuts that span lexer/parser abstraction.
//!
//! The way Rust works, parser doesn't necessary parse text, and you might
//! tokenize text without parsing it further. So, it makes sense to keep
//! abstract token parsing, and string tokenization as completely separate
//! layers.
//!
//! However, often you do pares text into syntax trees and the glue code for
//! that needs to live somewhere. Rather than putting it to lexer or parser, we
//! use a separate shortcuts module for that.
use std::mem;
use crate::{
LexedStr, Step,
SyntaxKind::{self, *},
};
#[derive(Debug)]
pub enum StrStep<'a> {
Token { kind: SyntaxKind, text: &'a str },
Enter { kind: SyntaxKind },
Exit,
Error { msg: &'a str, pos: usize },
}
impl<'a> LexedStr<'a> {
pub fn to_input(&self) -> crate::Input {
let mut res = crate::Input::default();
let mut was_joint = false;
for i in 0..self.len() {
let kind = self.kind(i);
if kind.is_trivia() {
was_joint = false
} else {
if kind == SyntaxKind::IDENT {
let token_text = self.text(i);
let contextual_kw = SyntaxKind::from_contextual_keyword(token_text)
.unwrap_or(SyntaxKind::IDENT);
res.push_ident(contextual_kw);
} else {
if was_joint {
res.was_joint();
}
res.push(kind);
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// Tag the token as joint if it is float with a fractional part
// we use this jointness to inform the parser about what token split
// event to emit when we encounter a float literal in a field access
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if kind == SyntaxKind::FLOAT_NUMBER && !self.text(i).ends_with('.') {
res.was_joint();
}
}
was_joint = true;
}
}
res
}
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/// NB: only valid to call with Output from Reparser/TopLevelEntry.
pub fn intersperse_trivia(
&self,
output: &crate::Output,
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sink: &mut dyn FnMut(StrStep<'_>),
) -> bool {
let mut builder = Builder { lexed: self, pos: 0, state: State::PendingEnter, sink };
for event in output.iter() {
match event {
Step::Token { kind, n_input_tokens: n_raw_tokens } => {
builder.token(kind, n_raw_tokens)
}
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Step::FloatSplit { ends_in_dot: has_pseudo_dot } => {
builder.float_split(has_pseudo_dot)
}
Step::Enter { kind } => builder.enter(kind),
Step::Exit => builder.exit(),
Step::Error { msg } => {
let text_pos = builder.lexed.text_start(builder.pos);
(builder.sink)(StrStep::Error { msg, pos: text_pos });
}
}
}
match mem::replace(&mut builder.state, State::Normal) {
State::PendingExit => {
builder.eat_trivias();
(builder.sink)(StrStep::Exit);
}
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State::PendingEnter | State::Normal => unreachable!(),
}
// is_eof?
builder.pos == builder.lexed.len()
}
}
struct Builder<'a, 'b> {
lexed: &'a LexedStr<'a>,
pos: usize,
state: State,
sink: &'b mut dyn FnMut(StrStep<'_>),
}
enum State {
PendingEnter,
Normal,
PendingExit,
}
impl Builder<'_, '_> {
fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
match mem::replace(&mut self.state, State::Normal) {
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State::PendingEnter => unreachable!(),
State::PendingExit => (self.sink)(StrStep::Exit),
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State::Normal => (),
}
self.eat_trivias();
self.do_token(kind, n_tokens as usize);
}
fn float_split(&mut self, has_pseudo_dot: bool) {
match mem::replace(&mut self.state, State::Normal) {
State::PendingEnter => unreachable!(),
State::PendingExit => (self.sink)(StrStep::Exit),
State::Normal => (),
}
self.eat_trivias();
self.do_float_split(has_pseudo_dot);
}
fn enter(&mut self, kind: SyntaxKind) {
match mem::replace(&mut self.state, State::Normal) {
State::PendingEnter => {
(self.sink)(StrStep::Enter { kind });
// No need to attach trivias to previous node: there is no
// previous node.
return;
}
State::PendingExit => (self.sink)(StrStep::Exit),
State::Normal => (),
}
let n_trivias =
(self.pos..self.lexed.len()).take_while(|&it| self.lexed.kind(it).is_trivia()).count();
let leading_trivias = self.pos..self.pos + n_trivias;
let n_attached_trivias = n_attached_trivias(
kind,
leading_trivias.rev().map(|it| (self.lexed.kind(it), self.lexed.text(it))),
);
self.eat_n_trivias(n_trivias - n_attached_trivias);
(self.sink)(StrStep::Enter { kind });
self.eat_n_trivias(n_attached_trivias);
}
fn exit(&mut self) {
match mem::replace(&mut self.state, State::PendingExit) {
State::PendingEnter => unreachable!(),
State::PendingExit => (self.sink)(StrStep::Exit),
State::Normal => (),
}
}
fn eat_trivias(&mut self) {
while self.pos < self.lexed.len() {
let kind = self.lexed.kind(self.pos);
if !kind.is_trivia() {
break;
}
self.do_token(kind, 1);
}
}
fn eat_n_trivias(&mut self, n: usize) {
for _ in 0..n {
let kind = self.lexed.kind(self.pos);
assert!(kind.is_trivia());
self.do_token(kind, 1);
}
}
fn do_token(&mut self, kind: SyntaxKind, n_tokens: usize) {
let text = &self.lexed.range_text(self.pos..self.pos + n_tokens);
self.pos += n_tokens;
(self.sink)(StrStep::Token { kind, text });
}
fn do_float_split(&mut self, has_pseudo_dot: bool) {
let text = &self.lexed.range_text(self.pos..self.pos + 1);
self.pos += 1;
match text.split_once('.') {
Some((left, right)) => {
assert!(!left.is_empty());
(self.sink)(StrStep::Enter { kind: SyntaxKind::NAME_REF });
(self.sink)(StrStep::Token { kind: SyntaxKind::INT_NUMBER, text: left });
(self.sink)(StrStep::Exit);
// here we move the exit up, the original exit has been deleted in process
(self.sink)(StrStep::Exit);
(self.sink)(StrStep::Token { kind: SyntaxKind::DOT, text: "." });
if has_pseudo_dot {
assert!(right.is_empty(), "{left}.{right}");
self.state = State::Normal;
} else {
(self.sink)(StrStep::Enter { kind: SyntaxKind::NAME_REF });
(self.sink)(StrStep::Token { kind: SyntaxKind::INT_NUMBER, text: right });
(self.sink)(StrStep::Exit);
// the parser creates an unbalanced start node, we are required to close it here
self.state = State::PendingExit;
}
}
None => unreachable!(),
}
}
}
fn n_attached_trivias<'a>(
kind: SyntaxKind,
trivias: impl Iterator<Item = (SyntaxKind, &'a str)>,
) -> usize {
match kind {
CONST | ENUM | FN | IMPL | MACRO_CALL | MACRO_DEF | MACRO_RULES | MODULE | RECORD_FIELD
| STATIC | STRUCT | TRAIT | TUPLE_FIELD | TYPE_ALIAS | UNION | USE | VARIANT => {
let mut res = 0;
let mut trivias = trivias.enumerate().peekable();
while let Some((i, (kind, text))) = trivias.next() {
match kind {
WHITESPACE if text.contains("\n\n") => {
// we check whether the next token is a doc-comment
// and skip the whitespace in this case
if let Some((COMMENT, peek_text)) = trivias.peek().map(|(_, pair)| pair) {
if is_outer(peek_text) {
continue;
}
}
break;
}
COMMENT => {
if is_inner(text) {
break;
}
res = i + 1;
}
_ => (),
}
}
res
}
_ => 0,
}
}
fn is_outer(text: &str) -> bool {
if text.starts_with("////") || text.starts_with("/***") {
return false;
}
text.starts_with("///") || text.starts_with("/**")
}
fn is_inner(text: &str) -> bool {
text.starts_with("//!") || text.starts_with("/*!")
}