Rollup merge of #65849 - popzxc:document-librustc_lexer, r=petrochenkov
librustc_lexer: Enhance documentation This PR enhances documentation state of the `librustc_lexer` (as initiative caused by [rustc-guide#474](https://github.com/rust-lang/rustc-guide/issues/474)), by adding: - Module documentation. - Doc-comments (and a bit of usual comments) in non-obvious (as for me) places. r? @petrochenkov cc @Centril
This commit is contained in:
commit
575058f3d7
3 changed files with 280 additions and 79 deletions
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@ -1,5 +1,9 @@
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use std::str::Chars;
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/// Peekable iterator over a char sequence.
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///
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/// Next characters can be peeked via `nth_char` method,
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/// and position can be shifted forward via `bump` method.
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pub(crate) struct Cursor<'a> {
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initial_len: usize,
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chars: Chars<'a>,
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@ -18,7 +22,9 @@ impl<'a> Cursor<'a> {
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prev: EOF_CHAR,
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}
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}
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/// For debug assertions only
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/// Returns the last eaten symbol (or '\0' in release builds).
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pub(crate) fn prev(&self) -> char {
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#[cfg(debug_assertions)]
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{
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@ -30,19 +36,30 @@ impl<'a> Cursor<'a> {
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'\0'
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}
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}
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/// Returns nth character relative to the current cursor position.
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/// If requested position doesn't exist, `EOF_CHAR` is returned.
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/// However, getting `EOF_CHAR` doesn't always mean actual end of file,
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/// it should be checked with `is_eof` method.
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pub(crate) fn nth_char(&self, n: usize) -> char {
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self.chars().nth(n).unwrap_or(EOF_CHAR)
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}
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/// Checks if there is nothing more to consume.
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pub(crate) fn is_eof(&self) -> bool {
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self.chars.as_str().is_empty()
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}
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/// Returns amount of already consumed symbols.
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pub(crate) fn len_consumed(&self) -> usize {
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self.initial_len - self.chars.as_str().len()
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}
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/// Returns an iterator over the remaining characters.
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/// Returns a `Chars` iterator over the remaining characters.
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fn chars(&self) -> Chars<'a> {
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self.chars.clone()
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}
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/// Moves to the next character.
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pub(crate) fn bump(&mut self) -> Option<char> {
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let c = self.chars.next()?;
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@ -1,3 +1,16 @@
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//! Low-level Rust lexer.
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//!
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//! Tokens produced by this lexer are not yet ready for parsing the Rust syntax,
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//! for that see `libsyntax::parse::lexer`, which converts this basic token stream
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//! into wide tokens used by actual parser.
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//!
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//! The purpose of this crate is to convert raw sources into a labeled sequence
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//! of well-known token types, so building an actual Rust token stream will
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//! be easier.
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//!
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//! Main entity of this crate is [`TokenKind`] enum which represents common
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//! lexeme types.
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// We want to be able to build this crate with a stable compiler, so no
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// `#![feature]` attributes should be added.
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@ -6,78 +19,144 @@ pub mod unescape;
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use crate::cursor::{Cursor, EOF_CHAR};
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/// Parsed token.
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/// It doesn't contain information about data that has been parsed,
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/// only the type of the token and its size.
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pub struct Token {
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pub kind: TokenKind,
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pub len: usize,
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}
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum TokenKind {
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LineComment,
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BlockComment { terminated: bool },
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Whitespace,
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Ident,
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RawIdent,
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Literal { kind: LiteralKind, suffix_start: usize },
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Lifetime { starts_with_number: bool },
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Semi,
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Comma,
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Dot,
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OpenParen,
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CloseParen,
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OpenBrace,
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CloseBrace,
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OpenBracket,
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CloseBracket,
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At,
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Pound,
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Tilde,
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Question,
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Colon,
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Dollar,
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Eq,
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Not,
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Lt,
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Gt,
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Minus,
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And,
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Or,
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Plus,
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Star,
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Slash,
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Caret,
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Percent,
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Unknown,
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}
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use self::TokenKind::*;
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum LiteralKind {
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Int { base: Base, empty_int: bool },
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Float { base: Base, empty_exponent: bool },
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Char { terminated: bool },
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Byte { terminated: bool },
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Str { terminated: bool },
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ByteStr { terminated: bool },
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RawStr { n_hashes: usize, started: bool, terminated: bool },
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RawByteStr { n_hashes: usize, started: bool, terminated: bool },
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}
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use self::LiteralKind::*;
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum Base {
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Binary,
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Octal,
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Hexadecimal,
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Decimal,
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}
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impl Token {
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fn new(kind: TokenKind, len: usize) -> Token {
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Token { kind, len }
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}
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}
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/// Enum represening common lexeme types.
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum TokenKind {
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// Multi-char tokens:
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/// "// comment"
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LineComment,
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/// "/* block comment */"
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/// Block comments can be recursive, so the sequence like "/* /* */"
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/// will not be considered terminated and will result in a parsing error.
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BlockComment { terminated: bool },
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/// Any whitespace characters sequence.
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Whitespace,
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/// "ident" or "continue"
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/// At this step keywords are also considered identifiers.
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Ident,
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/// "r#ident"
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RawIdent,
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/// "12_u8", "1.0e-40", "b"123"". See `LiteralKind` for more details.
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Literal { kind: LiteralKind, suffix_start: usize },
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/// "'a"
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Lifetime { starts_with_number: bool },
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// One-char tokens:
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/// ";"
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Semi,
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/// ","
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Comma,
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/// "."
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Dot,
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/// "("
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OpenParen,
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/// ")"
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CloseParen,
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/// "{"
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OpenBrace,
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/// "}"
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CloseBrace,
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/// "["
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OpenBracket,
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/// "]"
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CloseBracket,
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/// "@"
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At,
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/// "#"
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Pound,
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/// "~"
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Tilde,
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/// "?"
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Question,
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/// ":"
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Colon,
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/// "$"
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Dollar,
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/// "="
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Eq,
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/// "!"
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Not,
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/// "<"
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Lt,
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/// ">"
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Gt,
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/// "-"
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Minus,
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/// "&"
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And,
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/// "|"
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Or,
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/// "+"
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Plus,
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/// "*"
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Star,
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/// "/"
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Slash,
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/// "^"
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Caret,
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/// "%"
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Percent,
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/// Unknown token, not expected by the lexer, e.g. "№"
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Unknown,
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}
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use self::TokenKind::*;
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum LiteralKind {
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/// "12_u8", "0o100", "0b120i99"
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Int { base: Base, empty_int: bool },
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/// "12.34f32", "0b100.100"
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Float { base: Base, empty_exponent: bool },
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/// "'a'", "'\\'", "'''", "';"
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Char { terminated: bool },
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/// "b'a'", "b'\\'", "b'''", "b';"
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Byte { terminated: bool },
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/// ""abc"", ""abc"
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Str { terminated: bool },
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/// "b"abc"", "b"abc"
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ByteStr { terminated: bool },
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/// "r"abc"", "r#"abc"#", "r####"ab"###"c"####", "r#"a"
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RawStr { n_hashes: usize, started: bool, terminated: bool },
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/// "br"abc"", "br#"abc"#", "br####"ab"###"c"####", "br#"a"
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RawByteStr { n_hashes: usize, started: bool, terminated: bool },
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}
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use self::LiteralKind::*;
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/// Base of numeric literal encoding according to its prefix.
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#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
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pub enum Base {
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/// Literal starts with "0b".
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Binary,
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/// Literal starts with "0o".
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Octal,
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/// Literal starts with "0x".
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Hexadecimal,
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/// Literal doesn't contain a prefix.
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Decimal,
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}
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/// `rustc` allows files to have a shebang, e.g. "#!/usr/bin/rustrun",
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/// but shebang isn't a part of rust syntax, so this function
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/// skips the line if it starts with a shebang ("#!").
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/// Line won't be skipped if it represents a valid Rust syntax
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/// (e.g. "#![deny(missing_docs)]").
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pub fn strip_shebang(input: &str) -> Option<usize> {
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debug_assert!(!input.is_empty());
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if !input.starts_with("#!") || input.starts_with("#![") {
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@ -86,11 +165,13 @@ pub fn strip_shebang(input: &str) -> Option<usize> {
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Some(input.find('\n').unwrap_or(input.len()))
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}
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/// Parses the first token from the provided input string.
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pub fn first_token(input: &str) -> Token {
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debug_assert!(!input.is_empty());
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Cursor::new(input).advance_token()
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}
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/// Creates an iterator that produces tokens from the input string.
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pub fn tokenize(mut input: &str) -> impl Iterator<Item = Token> + '_ {
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std::iter::from_fn(move || {
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if input.is_empty() {
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@ -102,10 +183,9 @@ pub fn tokenize(mut input: &str) -> impl Iterator<Item = Token> + '_ {
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})
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}
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// See [UAX #31](http://unicode.org/reports/tr31) for definitions of these
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// classes.
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/// True if `c` is considered a whitespace according to Rust language definition.
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/// See [Rust language reference](https://doc.rust-lang.org/reference/whitespace.html)
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/// for definitions of these classes.
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pub fn is_whitespace(c: char) -> bool {
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// This is Pattern_White_Space.
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//
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@ -137,6 +217,8 @@ pub fn is_whitespace(c: char) -> bool {
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}
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/// True if `c` is valid as a first character of an identifier.
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/// See [Rust language reference](https://doc.rust-lang.org/reference/identifiers.html) for
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/// a formal definition of valid identifier name.
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pub fn is_id_start(c: char) -> bool {
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// This is XID_Start OR '_' (which formally is not a XID_Start).
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// We also add fast-path for ascii idents
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|
@ -147,6 +229,8 @@ pub fn is_id_start(c: char) -> bool {
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}
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/// True if `c` is valid as a non-first character of an identifier.
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/// See [Rust language reference](https://doc.rust-lang.org/reference/identifiers.html) for
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/// a formal definition of valid identifier name.
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pub fn is_id_continue(c: char) -> bool {
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// This is exactly XID_Continue.
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// We also add fast-path for ascii idents
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|
@ -159,15 +243,21 @@ pub fn is_id_continue(c: char) -> bool {
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impl Cursor<'_> {
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/// Parses a token from the input string.
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fn advance_token(&mut self) -> Token {
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let first_char = self.bump().unwrap();
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let token_kind = match first_char {
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// Slash, comment or block comment.
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'/' => match self.nth_char(0) {
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'/' => self.line_comment(),
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'*' => self.block_comment(),
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_ => Slash,
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},
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// Whitespace sequence.
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c if is_whitespace(c) => self.whitespace(),
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// Raw string literal or identifier.
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'r' => match (self.nth_char(0), self.nth_char(1)) {
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('#', c1) if is_id_start(c1) => self.raw_ident(),
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('#', _) | ('"', _) => {
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|
@ -181,6 +271,8 @@ impl Cursor<'_> {
|
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}
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_ => self.ident(),
|
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},
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// Byte literal, byte string literal, raw byte string literal or identifier.
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'b' => match (self.nth_char(0), self.nth_char(1)) {
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('\'', _) => {
|
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self.bump();
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|
@ -214,13 +306,20 @@ impl Cursor<'_> {
|
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}
|
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_ => self.ident(),
|
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},
|
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|
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// Identifier (this should be checked after other variant that can
|
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// start as identifier).
|
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c if is_id_start(c) => self.ident(),
|
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|
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// Numeric literal.
|
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c @ '0'..='9' => {
|
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let literal_kind = self.number(c);
|
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let suffix_start = self.len_consumed();
|
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self.eat_literal_suffix();
|
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TokenKind::Literal { kind: literal_kind, suffix_start }
|
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}
|
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|
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// One-symbol tokens.
|
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';' => Semi,
|
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',' => Comma,
|
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'.' => Dot,
|
||||
|
@ -247,7 +346,11 @@ impl Cursor<'_> {
|
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'*' => Star,
|
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'^' => Caret,
|
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'%' => Percent,
|
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|
||||
// Lifetime or character literal.
|
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'\'' => self.lifetime_or_char(),
|
||||
|
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// String literal.
|
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'"' => {
|
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let terminated = self.double_quoted_string();
|
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let suffix_start = self.len_consumed();
|
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|
@ -291,6 +394,9 @@ impl Cursor<'_> {
|
|||
self.bump();
|
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depth -= 1;
|
||||
if depth == 0 {
|
||||
// This block comment is closed, so for a construction like "/* */ */"
|
||||
// there will be a successfully parsed block comment "/* */"
|
||||
// and " */" will be processed separately.
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
@ -335,6 +441,7 @@ impl Cursor<'_> {
|
|||
debug_assert!('0' <= self.prev() && self.prev() <= '9');
|
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let mut base = Base::Decimal;
|
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if first_digit == '0' {
|
||||
// Attempt to parse encoding base.
|
||||
let has_digits = match self.nth_char(0) {
|
||||
'b' => {
|
||||
base = Base::Binary;
|
||||
|
@ -351,17 +458,21 @@ impl Cursor<'_> {
|
|||
self.bump();
|
||||
self.eat_hexadecimal_digits()
|
||||
}
|
||||
// Not a base prefix.
|
||||
'0'..='9' | '_' | '.' | 'e' | 'E' => {
|
||||
self.eat_decimal_digits();
|
||||
true
|
||||
}
|
||||
// just a 0
|
||||
// Just a 0.
|
||||
_ => return Int { base, empty_int: false },
|
||||
};
|
||||
// Base prefix was provided, but there were no digits
|
||||
// after it, e.g. "0x".
|
||||
if !has_digits {
|
||||
return Int { base, empty_int: true };
|
||||
}
|
||||
} else {
|
||||
// No base prefix, parse number in the usual way.
|
||||
self.eat_decimal_digits();
|
||||
};
|
||||
|
||||
|
@ -400,6 +511,9 @@ impl Cursor<'_> {
|
|||
fn lifetime_or_char(&mut self) -> TokenKind {
|
||||
debug_assert!(self.prev() == '\'');
|
||||
let mut starts_with_number = false;
|
||||
|
||||
// Check if the first symbol after '\'' is a valid identifier
|
||||
// character or a number (not a digit followed by '\'').
|
||||
if (is_id_start(self.nth_char(0))
|
||||
|| self.nth_char(0).is_digit(10) && {
|
||||
starts_with_number = true;
|
||||
|
@ -408,6 +522,8 @@ impl Cursor<'_> {
|
|||
&& self.nth_char(1) != '\''
|
||||
{
|
||||
self.bump();
|
||||
|
||||
// Skip the identifier.
|
||||
while is_id_continue(self.nth_char(0)) {
|
||||
self.bump();
|
||||
}
|
||||
|
@ -420,6 +536,8 @@ impl Cursor<'_> {
|
|||
Lifetime { starts_with_number }
|
||||
};
|
||||
}
|
||||
|
||||
// This is not a lifetime (checked above), parse a char literal.
|
||||
let terminated = self.single_quoted_string();
|
||||
let suffix_start = self.len_consumed();
|
||||
if terminated {
|
||||
|
@ -431,24 +549,32 @@ impl Cursor<'_> {
|
|||
|
||||
fn single_quoted_string(&mut self) -> bool {
|
||||
debug_assert!(self.prev() == '\'');
|
||||
// parse `'''` as a single char literal
|
||||
// Parse `'''` as a single char literal.
|
||||
if self.nth_char(0) == '\'' && self.nth_char(1) == '\'' {
|
||||
self.bump();
|
||||
}
|
||||
// Parse until either quotes are terminated or error is detected.
|
||||
let mut first = true;
|
||||
loop {
|
||||
match self.nth_char(0) {
|
||||
// Probably beginning of the comment, which we don't want to include
|
||||
// to the error report.
|
||||
'/' if !first => break,
|
||||
// Newline without following '\'' means unclosed quote, stop parsing.
|
||||
'\n' if self.nth_char(1) != '\'' => break,
|
||||
// End of file, stop parsing.
|
||||
EOF_CHAR if self.is_eof() => break,
|
||||
// Quotes are terminated, finish parsing.
|
||||
'\'' => {
|
||||
self.bump();
|
||||
return true;
|
||||
}
|
||||
// Escaped slash is considered one character, so bump twice.
|
||||
'\\' => {
|
||||
self.bump();
|
||||
self.bump();
|
||||
}
|
||||
// Skip the character.
|
||||
_ => {
|
||||
self.bump();
|
||||
}
|
||||
|
@ -458,6 +584,8 @@ impl Cursor<'_> {
|
|||
false
|
||||
}
|
||||
|
||||
/// Eats double-quoted string and returns true
|
||||
/// if string is terminated.
|
||||
fn double_quoted_string(&mut self) -> bool {
|
||||
debug_assert!(self.prev() == '"');
|
||||
loop {
|
||||
|
@ -476,8 +604,11 @@ impl Cursor<'_> {
|
|||
}
|
||||
}
|
||||
|
||||
/// Eats the double-quoted string and returns a tuple of
|
||||
/// (amount of the '#' symbols, raw string started, raw string terminated)
|
||||
fn raw_double_quoted_string(&mut self) -> (usize, bool, bool) {
|
||||
debug_assert!(self.prev() == 'r');
|
||||
// Count opening '#' symbols.
|
||||
let n_hashes = {
|
||||
let mut acc: usize = 0;
|
||||
loop {
|
||||
|
@ -489,6 +620,8 @@ impl Cursor<'_> {
|
|||
}
|
||||
};
|
||||
|
||||
// Skip the string itself and check that amount of closing '#'
|
||||
// symbols is equal to the amount of opening ones.
|
||||
loop {
|
||||
match self.bump() {
|
||||
Some('"') => {
|
||||
|
@ -549,6 +682,7 @@ impl Cursor<'_> {
|
|||
if self.eat_decimal_digits() { Ok(()) } else { Err(()) }
|
||||
}
|
||||
|
||||
// Eats the suffix if it's an identifier.
|
||||
fn eat_literal_suffix(&mut self) {
|
||||
if !is_id_start(self.nth_char(0)) {
|
||||
return;
|
||||
|
|
|
@ -7,32 +7,54 @@ use std::ops::Range;
|
|||
#[cfg(test)]
|
||||
mod tests;
|
||||
|
||||
/// Errors that can occur during string unescaping.
|
||||
#[derive(Debug, PartialEq, Eq)]
|
||||
pub enum EscapeError {
|
||||
/// Expected 1 char, but 0 were found.
|
||||
ZeroChars,
|
||||
/// Expected 1 char, but more than 1 were found.
|
||||
MoreThanOneChar,
|
||||
|
||||
/// Escaped '\' character without continuation.
|
||||
LoneSlash,
|
||||
/// Invalid escape characted (e.g. '\z').
|
||||
InvalidEscape,
|
||||
/// Raw '\r' encountered.
|
||||
BareCarriageReturn,
|
||||
/// Raw '\r' encountered in raw string.
|
||||
BareCarriageReturnInRawString,
|
||||
/// Unescaped character that was expected to be escaped (e.g. raw '\t').
|
||||
EscapeOnlyChar,
|
||||
|
||||
/// Numeric character escape is too short (e.g. '\x1').
|
||||
TooShortHexEscape,
|
||||
/// Invalid character in numeric escape (e.g. '\xz')
|
||||
InvalidCharInHexEscape,
|
||||
/// Character code in numeric escape is non-ascii (e.g. '\xFF').
|
||||
OutOfRangeHexEscape,
|
||||
|
||||
/// '\u' not followed by '{'.
|
||||
NoBraceInUnicodeEscape,
|
||||
/// Non-hexadecimal value in '\u{..}'.
|
||||
InvalidCharInUnicodeEscape,
|
||||
/// '\u{}'
|
||||
EmptyUnicodeEscape,
|
||||
/// No closing brace in '\u{..}', e.g. '\u{12'.
|
||||
UnclosedUnicodeEscape,
|
||||
/// '\u{_12}'
|
||||
LeadingUnderscoreUnicodeEscape,
|
||||
/// More than 6 charactes in '\u{..}', e.g. '\u{10FFFF_FF}'
|
||||
OverlongUnicodeEscape,
|
||||
/// Invalid in-bound unicode character code, e.g. '\u{DFFF}'.
|
||||
LoneSurrogateUnicodeEscape,
|
||||
/// Out of bounds unicode character code, e.g. '\u{FFFFFF}'.
|
||||
OutOfRangeUnicodeEscape,
|
||||
|
||||
/// Unicode escape code in byte literal.
|
||||
UnicodeEscapeInByte,
|
||||
/// Non-ascii character in byte literal.
|
||||
NonAsciiCharInByte,
|
||||
/// Non-ascii character in byte string literal.
|
||||
NonAsciiCharInByteString,
|
||||
}
|
||||
|
||||
|
@ -44,15 +66,8 @@ pub fn unescape_char(literal_text: &str) -> Result<char, (usize, EscapeError)> {
|
|||
.map_err(|err| (literal_text.len() - chars.as_str().len(), err))
|
||||
}
|
||||
|
||||
/// Takes a contents of a string literal (without quotes) and produces a
|
||||
/// sequence of escaped characters or errors.
|
||||
pub fn unescape_str<F>(literal_text: &str, callback: &mut F)
|
||||
where
|
||||
F: FnMut(Range<usize>, Result<char, EscapeError>),
|
||||
{
|
||||
unescape_str_or_byte_str(literal_text, Mode::Str, callback)
|
||||
}
|
||||
|
||||
/// Takes a contents of a byte literal (without quotes), and returns an
|
||||
/// unescaped byte or an error.
|
||||
pub fn unescape_byte(literal_text: &str) -> Result<u8, (usize, EscapeError)> {
|
||||
let mut chars = literal_text.chars();
|
||||
unescape_char_or_byte(&mut chars, Mode::Byte)
|
||||
|
@ -62,6 +77,17 @@ pub fn unescape_byte(literal_text: &str) -> Result<u8, (usize, EscapeError)> {
|
|||
|
||||
/// Takes a contents of a string literal (without quotes) and produces a
|
||||
/// sequence of escaped characters or errors.
|
||||
/// Values are returned through invoking of the provided callback.
|
||||
pub fn unescape_str<F>(literal_text: &str, callback: &mut F)
|
||||
where
|
||||
F: FnMut(Range<usize>, Result<char, EscapeError>),
|
||||
{
|
||||
unescape_str_or_byte_str(literal_text, Mode::Str, callback)
|
||||
}
|
||||
|
||||
/// Takes a contents of a byte string literal (without quotes) and produces a
|
||||
/// sequence of bytes or errors.
|
||||
/// Values are returned through invoking of the provided callback.
|
||||
pub fn unescape_byte_str<F>(literal_text: &str, callback: &mut F)
|
||||
where
|
||||
F: FnMut(Range<usize>, Result<u8, EscapeError>),
|
||||
|
@ -71,8 +97,9 @@ where
|
|||
})
|
||||
}
|
||||
|
||||
/// Takes a contents of a string literal (without quotes) and produces a
|
||||
/// Takes a contents of a raw string literal (without quotes) and produces a
|
||||
/// sequence of characters or errors.
|
||||
/// Values are returned through invoking of the provided callback.
|
||||
/// NOTE: Raw strings do not perform any explicit character escaping, here we
|
||||
/// only translate CRLF to LF and produce errors on bare CR.
|
||||
pub fn unescape_raw_str<F>(literal_text: &str, callback: &mut F)
|
||||
|
@ -82,8 +109,9 @@ where
|
|||
unescape_raw_str_or_byte_str(literal_text, Mode::Str, callback)
|
||||
}
|
||||
|
||||
/// Takes a contents of a string literal (without quotes) and produces a
|
||||
/// sequence of characters or errors.
|
||||
/// Takes a contents of a raw byte string literal (without quotes) and produces a
|
||||
/// sequence of bytes or errors.
|
||||
/// Values are returned through invoking of the provided callback.
|
||||
/// NOTE: Raw strings do not perform any explicit character escaping, here we
|
||||
/// only translate CRLF to LF and produce errors on bare CR.
|
||||
pub fn unescape_raw_byte_str<F>(literal_text: &str, callback: &mut F)
|
||||
|
@ -95,6 +123,7 @@ where
|
|||
})
|
||||
}
|
||||
|
||||
/// What kind of literal do we parse.
|
||||
#[derive(Debug, Clone, Copy)]
|
||||
pub enum Mode {
|
||||
Char,
|
||||
|
@ -126,6 +155,8 @@ impl Mode {
|
|||
|
||||
fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
|
||||
if first_char != '\\' {
|
||||
// Previous character was not a slash, and we don't expect it to be
|
||||
// an escape-only character.
|
||||
return match first_char {
|
||||
'\t' | '\n' => Err(EscapeError::EscapeOnlyChar),
|
||||
'\r' => Err(EscapeError::BareCarriageReturn),
|
||||
|
@ -133,6 +164,7 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
'"' if mode.in_double_quotes() => Err(EscapeError::EscapeOnlyChar),
|
||||
_ => {
|
||||
if mode.is_bytes() && !first_char.is_ascii() {
|
||||
// Byte literal can't be a non-ascii character.
|
||||
return Err(EscapeError::NonAsciiCharInByte);
|
||||
}
|
||||
Ok(first_char)
|
||||
|
@ -140,6 +172,8 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
};
|
||||
}
|
||||
|
||||
// Previous character is '\\', try to unescape it.
|
||||
|
||||
let second_char = chars.next().ok_or(EscapeError::LoneSlash)?;
|
||||
|
||||
let res = match second_char {
|
||||
|
@ -152,6 +186,8 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
'0' => '\0',
|
||||
|
||||
'x' => {
|
||||
// Parse hexadecimal character code.
|
||||
|
||||
let hi = chars.next().ok_or(EscapeError::TooShortHexEscape)?;
|
||||
let hi = hi.to_digit(16).ok_or(EscapeError::InvalidCharInHexEscape)?;
|
||||
|
||||
|
@ -160,6 +196,7 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
|
||||
let value = hi * 16 + lo;
|
||||
|
||||
// For a byte literal verify that it is within ASCII range.
|
||||
if !mode.is_bytes() && !is_ascii(value) {
|
||||
return Err(EscapeError::OutOfRangeHexEscape);
|
||||
}
|
||||
|
@ -169,10 +206,13 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
}
|
||||
|
||||
'u' => {
|
||||
// We've parsed '\u', now we have to parse '{..}'.
|
||||
|
||||
if chars.next() != Some('{') {
|
||||
return Err(EscapeError::NoBraceInUnicodeEscape);
|
||||
}
|
||||
|
||||
// First characrer must be a hexadecimal digit.
|
||||
let mut n_digits = 1;
|
||||
let mut value: u32 = match chars.next().ok_or(EscapeError::UnclosedUnicodeEscape)? {
|
||||
'_' => return Err(EscapeError::LeadingUnderscoreUnicodeEscape),
|
||||
|
@ -180,6 +220,8 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
c => c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?,
|
||||
};
|
||||
|
||||
// First character is valid, now parse the rest of the number
|
||||
// and closing brace.
|
||||
loop {
|
||||
match chars.next() {
|
||||
None => return Err(EscapeError::UnclosedUnicodeEscape),
|
||||
|
@ -188,6 +230,9 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
if n_digits > 6 {
|
||||
return Err(EscapeError::OverlongUnicodeEscape);
|
||||
}
|
||||
|
||||
// Incorrect syntax has higher priority for error reporting
|
||||
// than unallowed value for a literal.
|
||||
if mode.is_bytes() {
|
||||
return Err(EscapeError::UnicodeEscapeInByte);
|
||||
}
|
||||
|
@ -204,6 +249,7 @@ fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<ch
|
|||
let digit = c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?;
|
||||
n_digits += 1;
|
||||
if n_digits > 6 {
|
||||
// Stop updating value since we're sure that it's is incorrect already.
|
||||
continue;
|
||||
}
|
||||
let digit = digit as u32;
|
||||
|
@ -243,6 +289,10 @@ where
|
|||
let second_char = chars.clone().next();
|
||||
match second_char {
|
||||
Some('\n') => {
|
||||
// Rust language specification requires us to skip whitespaces
|
||||
// if unescaped '\' character is followed by '\n'.
|
||||
// For details see [Rust language reference]
|
||||
// (https://doc.rust-lang.org/reference/tokens.html#string-literals).
|
||||
skip_ascii_whitespace(&mut chars);
|
||||
continue;
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue