301 lines
11 KiB
Rust
301 lines
11 KiB
Rust
//! Lexing `&str` into a sequence of Rust tokens.
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//!
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//! Note that strictly speaking the parser in this crate is not required to work
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//! on tokens which originated from text. Macros, eg, can synthesize tokens out
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//! of thin air. So, ideally, lexer should be an orthogonal crate. It is however
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//! convenient to include a text-based lexer here!
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//!
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//! Note that these tokens, unlike the tokens we feed into the parser, do
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//! include info about comments and whitespace.
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use std::ops;
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use crate::{
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SyntaxKind::{self, *},
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T,
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};
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pub struct LexedStr<'a> {
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text: &'a str,
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kind: Vec<SyntaxKind>,
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start: Vec<u32>,
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error: Vec<LexError>,
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}
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struct LexError {
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msg: String,
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token: u32,
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}
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impl<'a> LexedStr<'a> {
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pub fn new(text: &'a str) -> LexedStr<'a> {
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let mut conv = Converter::new(text);
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if let Some(shebang_len) = rustc_lexer::strip_shebang(text) {
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conv.res.push(SHEBANG, conv.offset);
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conv.offset = shebang_len;
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};
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for token in rustc_lexer::tokenize(&text[conv.offset..]) {
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let token_text = &text[conv.offset..][..token.len];
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conv.extend_token(&token.kind, token_text);
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}
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conv.finalize_with_eof()
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}
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pub fn single_token(text: &'a str) -> Option<(SyntaxKind, Option<String>)> {
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if text.is_empty() {
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return None;
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}
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let token = rustc_lexer::first_token(text);
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if token.len != text.len() {
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return None;
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}
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let mut conv = Converter::new(text);
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conv.extend_token(&token.kind, text);
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match &*conv.res.kind {
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[kind] => Some((*kind, conv.res.error.pop().map(|it| it.msg))),
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_ => None,
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}
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}
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pub fn as_str(&self) -> &str {
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self.text
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}
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pub fn len(&self) -> usize {
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self.kind.len() - 1
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}
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pub fn is_empty(&self) -> bool {
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self.len() == 0
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}
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pub fn kind(&self, i: usize) -> SyntaxKind {
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assert!(i < self.len());
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self.kind[i]
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}
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pub fn text(&self, i: usize) -> &str {
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self.range_text(i..i + 1)
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}
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pub fn range_text(&self, r: ops::Range<usize>) -> &str {
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assert!(r.start < r.end && r.end <= self.len());
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let lo = self.start[r.start] as usize;
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let hi = self.start[r.end] as usize;
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&self.text[lo..hi]
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}
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// Naming is hard.
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pub fn text_range(&self, i: usize) -> ops::Range<usize> {
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assert!(i < self.len());
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let lo = self.start[i] as usize;
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let hi = self.start[i + 1] as usize;
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lo..hi
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}
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pub fn text_start(&self, i: usize) -> usize {
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assert!(i <= self.len());
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self.start[i] as usize
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}
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pub fn text_len(&self, i: usize) -> usize {
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assert!(i < self.len());
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let r = self.text_range(i);
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r.end - r.start
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}
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pub fn error(&self, i: usize) -> Option<&str> {
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assert!(i < self.len());
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let err = self.error.binary_search_by_key(&(i as u32), |i| i.token).ok()?;
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Some(self.error[err].msg.as_str())
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}
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pub fn errors(&self) -> impl Iterator<Item = (usize, &str)> + '_ {
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self.error.iter().map(|it| (it.token as usize, it.msg.as_str()))
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}
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fn push(&mut self, kind: SyntaxKind, offset: usize) {
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self.kind.push(kind);
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self.start.push(offset as u32);
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}
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}
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struct Converter<'a> {
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res: LexedStr<'a>,
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offset: usize,
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}
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impl<'a> Converter<'a> {
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fn new(text: &'a str) -> Self {
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Self {
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res: LexedStr { text, kind: Vec::new(), start: Vec::new(), error: Vec::new() },
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offset: 0,
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}
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}
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fn finalize_with_eof(mut self) -> LexedStr<'a> {
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self.res.push(EOF, self.offset);
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self.res
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}
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fn push(&mut self, kind: SyntaxKind, len: usize, err: Option<&str>) {
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self.res.push(kind, self.offset);
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self.offset += len;
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if let Some(err) = err {
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let token = self.res.len() as u32;
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let msg = err.to_string();
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self.res.error.push(LexError { msg, token });
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}
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}
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fn extend_token(&mut self, kind: &rustc_lexer::TokenKind, token_text: &str) {
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// A note on an intended tradeoff:
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// We drop some useful information here (see patterns with double dots `..`)
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// Storing that info in `SyntaxKind` is not possible due to its layout requirements of
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// being `u16` that come from `rowan::SyntaxKind`.
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let mut err = "";
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let syntax_kind = {
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match kind {
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rustc_lexer::TokenKind::LineComment { doc_style: _ } => COMMENT,
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rustc_lexer::TokenKind::BlockComment { doc_style: _, terminated } => {
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if !terminated {
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err = "Missing trailing `*/` symbols to terminate the block comment";
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}
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COMMENT
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}
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rustc_lexer::TokenKind::Whitespace => WHITESPACE,
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rustc_lexer::TokenKind::Ident if token_text == "_" => UNDERSCORE,
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rustc_lexer::TokenKind::Ident => {
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SyntaxKind::from_keyword(token_text).unwrap_or(IDENT)
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}
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rustc_lexer::TokenKind::RawIdent => IDENT,
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rustc_lexer::TokenKind::Literal { kind, .. } => {
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self.extend_literal(token_text.len(), kind);
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return;
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}
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rustc_lexer::TokenKind::Lifetime { starts_with_number } => {
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if *starts_with_number {
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err = "Lifetime name cannot start with a number";
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}
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LIFETIME_IDENT
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}
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rustc_lexer::TokenKind::Semi => T![;],
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rustc_lexer::TokenKind::Comma => T![,],
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rustc_lexer::TokenKind::Dot => T![.],
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rustc_lexer::TokenKind::OpenParen => T!['('],
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rustc_lexer::TokenKind::CloseParen => T![')'],
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rustc_lexer::TokenKind::OpenBrace => T!['{'],
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rustc_lexer::TokenKind::CloseBrace => T!['}'],
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rustc_lexer::TokenKind::OpenBracket => T!['['],
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rustc_lexer::TokenKind::CloseBracket => T![']'],
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rustc_lexer::TokenKind::At => T![@],
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rustc_lexer::TokenKind::Pound => T![#],
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rustc_lexer::TokenKind::Tilde => T![~],
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rustc_lexer::TokenKind::Question => T![?],
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rustc_lexer::TokenKind::Colon => T![:],
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rustc_lexer::TokenKind::Dollar => T![$],
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rustc_lexer::TokenKind::Eq => T![=],
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rustc_lexer::TokenKind::Bang => T![!],
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rustc_lexer::TokenKind::Lt => T![<],
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rustc_lexer::TokenKind::Gt => T![>],
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rustc_lexer::TokenKind::Minus => T![-],
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rustc_lexer::TokenKind::And => T![&],
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rustc_lexer::TokenKind::Or => T![|],
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rustc_lexer::TokenKind::Plus => T![+],
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rustc_lexer::TokenKind::Star => T![*],
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rustc_lexer::TokenKind::Slash => T![/],
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rustc_lexer::TokenKind::Caret => T![^],
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rustc_lexer::TokenKind::Percent => T![%],
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rustc_lexer::TokenKind::Unknown => ERROR,
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}
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};
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let err = if err.is_empty() { None } else { Some(err) };
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self.push(syntax_kind, token_text.len(), err);
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}
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fn extend_literal(&mut self, len: usize, kind: &rustc_lexer::LiteralKind) {
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let mut err = "";
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let syntax_kind = match *kind {
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rustc_lexer::LiteralKind::Int { empty_int, base: _ } => {
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if empty_int {
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err = "Missing digits after the integer base prefix";
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}
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INT_NUMBER
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}
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rustc_lexer::LiteralKind::Float { empty_exponent, base: _ } => {
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if empty_exponent {
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err = "Missing digits after the exponent symbol";
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}
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FLOAT_NUMBER
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}
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rustc_lexer::LiteralKind::Char { terminated } => {
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if !terminated {
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err = "Missing trailing `'` symbol to terminate the character literal";
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}
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CHAR
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}
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rustc_lexer::LiteralKind::Byte { terminated } => {
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if !terminated {
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err = "Missing trailing `'` symbol to terminate the byte literal";
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}
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BYTE
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}
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rustc_lexer::LiteralKind::Str { terminated } => {
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if !terminated {
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err = "Missing trailing `\"` symbol to terminate the string literal";
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}
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STRING
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}
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rustc_lexer::LiteralKind::ByteStr { terminated } => {
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if !terminated {
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err = "Missing trailing `\"` symbol to terminate the byte string literal";
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}
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BYTE_STRING
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}
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rustc_lexer::LiteralKind::RawStr { err: raw_str_err, .. } => {
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if let Some(raw_str_err) = raw_str_err {
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err = match raw_str_err {
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rustc_lexer::RawStrError::InvalidStarter { .. } => "Missing `\"` symbol after `#` symbols to begin the raw string literal",
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rustc_lexer::RawStrError::NoTerminator { expected, found, .. } => if expected == found {
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"Missing trailing `\"` to terminate the raw string literal"
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} else {
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"Missing trailing `\"` with `#` symbols to terminate the raw string literal"
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},
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rustc_lexer::RawStrError::TooManyDelimiters { .. } => "Too many `#` symbols: raw strings may be delimited by up to 65535 `#` symbols",
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};
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};
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STRING
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}
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rustc_lexer::LiteralKind::RawByteStr { err: raw_str_err, .. } => {
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if let Some(raw_str_err) = raw_str_err {
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err = match raw_str_err {
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rustc_lexer::RawStrError::InvalidStarter { .. } => "Missing `\"` symbol after `#` symbols to begin the raw byte string literal",
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rustc_lexer::RawStrError::NoTerminator { expected, found, .. } => if expected == found {
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"Missing trailing `\"` to terminate the raw byte string literal"
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} else {
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"Missing trailing `\"` with `#` symbols to terminate the raw byte string literal"
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},
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rustc_lexer::RawStrError::TooManyDelimiters { .. } => "Too many `#` symbols: raw byte strings may be delimited by up to 65535 `#` symbols",
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};
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};
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BYTE_STRING
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}
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};
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let err = if err.is_empty() { None } else { Some(err) };
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self.push(syntax_kind, len, err);
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}
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}
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