compiler/rustc_parse/src/lexer/mod.rs

   1 use crate::lexer::unicode_chars::UNICODE_ARRAY;
   2 use rustc_ast::ast::{self, AttrStyle};
   3 use rustc_ast::token::{self, CommentKind, Delimiter, Token, TokenKind};
   4 use rustc_ast::tokenstream::TokenStream;
   5 use rustc_ast::util::unicode::contains_text_flow_control_chars;
   6 use rustc_errors::{
   7     error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult, StashKey,
   8 };
   9 use rustc_lexer::unescape::{self, Mode};
  10 use rustc_lexer::Cursor;
  11 use rustc_lexer::{Base, DocStyle, RawStrError};
  12 use rustc_session::lint::builtin::{
  13     RUST_2021_PREFIXES_INCOMPATIBLE_SYNTAX, TEXT_DIRECTION_CODEPOINT_IN_COMMENT,
  14 };
  15 use rustc_session::lint::BuiltinLintDiagnostics;
  16 use rustc_session::parse::ParseSess;
  17 use rustc_span::symbol::{sym, Symbol};
  18 use rustc_span::{edition::Edition, BytePos, Pos, Span};
  19
  20 mod tokentrees;
  21 mod unescape_error_reporting;
  22 mod unicode_chars;
  23
  24 use unescape_error_reporting::{emit_unescape_error, escaped_char};
  25
  26 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
  27 //
  28 // This assertion is in this crate, rather than in `rustc_lexer`, because that
  29 // crate cannot depend on `rustc_data_structures`.
  30 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
  31 rustc_data_structures::static_assert_size!(rustc_lexer::Token, 12);
  32
  33 #[derive(Clone, Debug)]
  34 pub struct UnmatchedBrace {
  35     pub expected_delim: Delimiter,
  36     pub found_delim: Option<Delimiter>,
  37     pub found_span: Span,
  38     pub unclosed_span: Option<Span>,
  39     pub candidate_span: Option<Span>,
  40 }
  41
  42 pub(crate) fn parse_token_trees<'a>(
  43     sess: &'a ParseSess,
  44     mut src: &'a str,
  45     mut start_pos: BytePos,
  46     override_span: Option<Span>,
  47 ) -> (PResult<'a, TokenStream>, Vec<UnmatchedBrace>) {
  48     // Skip `#!`, if present.
  49     if let Some(shebang_len) = rustc_lexer::strip_shebang(src) {
  50         src = &src[shebang_len..];
  51         start_pos = start_pos + BytePos::from_usize(shebang_len);
  52     }
  53
  54     let cursor = Cursor::new(src);
  55     let string_reader = StringReader {
  56         sess,
  57         start_pos,
  58         pos: start_pos,
  59         src,
  60         cursor,
  61         override_span,
  62         nbsp_is_whitespace: false,
  63     };
  64     tokentrees::TokenTreesReader::parse_all_token_trees(string_reader)
  65 }
  66
  67 struct StringReader<'a> {
  68     sess: &'a ParseSess,
  69     /// Initial position, read-only.
  70     start_pos: BytePos,
  71     /// The absolute offset within the source_map of the current character.
  72     pos: BytePos,
  73     /// Source text to tokenize.
  74     src: &'a str,
  75     /// Cursor for getting lexer tokens.
  76     cursor: Cursor<'a>,
  77     override_span: Option<Span>,
  78     /// When a "unknown start of token: \u{a0}" has already been emitted earlier
  79     /// in this file, it's safe to treat further occurrences of the non-breaking
  80     /// space character as whitespace.
  81     nbsp_is_whitespace: bool,
  82 }
  83
  84 impl<'a> StringReader<'a> {
  85     fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
  86         self.override_span.unwrap_or_else(|| Span::with_root_ctxt(lo, hi))
  87     }
  88
  89     /// Returns the next token, paired with a bool indicating if the token was
  90     /// preceded by whitespace.
  91     fn next_token(&mut self) -> (Token, bool) {
  92         let mut preceded_by_whitespace = false;
  93         let mut swallow_next_invalid = 0;
  94         // Skip trivial (whitespace & comments) tokens
  95         loop {
  96             let token = self.cursor.advance_token();
  97             let start = self.pos;
  98             self.pos = self.pos + BytePos(token.len);
  99
 100             debug!("next_token: {:?}({:?})", token.kind, self.str_from(start));
 101
 102             // Now "cook" the token, converting the simple `rustc_lexer::TokenKind` enum into a
 103             // rich `rustc_ast::TokenKind`. This turns strings into interned symbols and runs
 104             // additional validation.
 105             let kind = match token.kind {
 106                 rustc_lexer::TokenKind::LineComment { doc_style } => {
 107                     // Skip non-doc comments
 108                     let Some(doc_style) = doc_style else {
 109                         self.lint_unicode_text_flow(start);
 110                         preceded_by_whitespace = true;
 111                         continue;
 112                     };
 113
 114                     // Opening delimiter of the length 3 is not included into the symbol.
 115                     let content_start = start + BytePos(3);
 116                     let content = self.str_from(content_start);
 117                     self.cook_doc_comment(content_start, content, CommentKind::Line, doc_style)
 118                 }
 119                 rustc_lexer::TokenKind::BlockComment { doc_style, terminated } => {
 120                     if !terminated {
 121                         self.report_unterminated_block_comment(start, doc_style);
 122                     }
 123
 124                     // Skip non-doc comments
 125                     let Some(doc_style) = doc_style else {
 126                         self.lint_unicode_text_flow(start);
 127                         preceded_by_whitespace = true;
 128                         continue;
 129                     };
 130
 131                     // Opening delimiter of the length 3 and closing delimiter of the length 2
 132                     // are not included into the symbol.
 133                     let content_start = start + BytePos(3);
 134                     let content_end = self.pos - BytePos(if terminated { 2 } else { 0 });
 135                     let content = self.str_from_to(content_start, content_end);
 136                     self.cook_doc_comment(content_start, content, CommentKind::Block, doc_style)
 137                 }
 138                 rustc_lexer::TokenKind::Whitespace => {
 139                     preceded_by_whitespace = true;
 140                     continue;
 141                 }
 142                 rustc_lexer::TokenKind::Ident => {
 143                     let sym = nfc_normalize(self.str_from(start));
 144                     let span = self.mk_sp(start, self.pos);
 145                     self.sess.symbol_gallery.insert(sym, span);
 146                     token::Ident(sym, false)
 147                 }
 148                 rustc_lexer::TokenKind::RawIdent => {
 149                     let sym = nfc_normalize(self.str_from(start + BytePos(2)));
 150                     let span = self.mk_sp(start, self.pos);
 151                     self.sess.symbol_gallery.insert(sym, span);
 152                     if !sym.can_be_raw() {
 153                         self.err_span(span, &format!("`{}` cannot be a raw identifier", sym));
 154                     }
 155                     self.sess.raw_identifier_spans.borrow_mut().push(span);
 156                     token::Ident(sym, true)
 157                 }
 158                 rustc_lexer::TokenKind::UnknownPrefix => {
 159                     self.report_unknown_prefix(start);
 160                     let sym = nfc_normalize(self.str_from(start));
 161                     let span = self.mk_sp(start, self.pos);
 162                     self.sess.symbol_gallery.insert(sym, span);
 163                     token::Ident(sym, false)
 164                 }
 165                 rustc_lexer::TokenKind::InvalidIdent
 166                     // Do not recover an identifier with emoji if the codepoint is a confusable
 167                     // with a recoverable substitution token, like `➖`.
 168                     if !UNICODE_ARRAY
 169                         .iter()
 170                         .any(|&(c, _, _)| {
 171                             let sym = self.str_from(start);
 172                             sym.chars().count() == 1 && c == sym.chars().next().unwrap()
 173                         }) =>
 174                 {
 175                     let sym = nfc_normalize(self.str_from(start));
 176                     let span = self.mk_sp(start, self.pos);
 177                     self.sess.bad_unicode_identifiers.borrow_mut().entry(sym).or_default()
 178                         .push(span);
 179                     token::Ident(sym, false)
 180                 }
 181                 rustc_lexer::TokenKind::Literal { kind, suffix_start } => {
 182                     let suffix_start = start + BytePos(suffix_start);
 183                     let (kind, symbol) = self.cook_lexer_literal(start, suffix_start, kind);
 184                     let suffix = if suffix_start < self.pos {
 185                         let string = self.str_from(suffix_start);
 186                         if string == "_" {
 187                             self.sess
 188                                 .span_diagnostic
 189                                 .struct_span_err(
 190                                     self.mk_sp(suffix_start, self.pos),
 191                                     "underscore literal suffix is not allowed",
 192                                 )
 193                                 .emit();
 194                             None
 195                         } else {
 196                             Some(Symbol::intern(string))
 197                         }
 198                     } else {
 199                         None
 200                     };
 201                     token::Literal(token::Lit { kind, symbol, suffix })
 202                 }
 203                 rustc_lexer::TokenKind::Lifetime { starts_with_number } => {
 204                     // Include the leading `'` in the real identifier, for macro
 205                     // expansion purposes. See #12512 for the gory details of why
 206                     // this is necessary.
 207                     let lifetime_name = self.str_from(start);
 208                     if starts_with_number {
 209                         let span = self.mk_sp(start, self.pos);
 210                         let mut diag = self.sess.struct_err("lifetimes cannot start with a number");
 211                         diag.set_span(span);
 212                         diag.stash(span, StashKey::LifetimeIsChar);
 213                     }
 214                     let ident = Symbol::intern(lifetime_name);
 215                     token::Lifetime(ident)
 216                 }
 217                 rustc_lexer::TokenKind::Semi => token::Semi,
 218                 rustc_lexer::TokenKind::Comma => token::Comma,
 219                 rustc_lexer::TokenKind::Dot => token::Dot,
 220                 rustc_lexer::TokenKind::OpenParen => token::OpenDelim(Delimiter::Parenthesis),
 221                 rustc_lexer::TokenKind::CloseParen => token::CloseDelim(Delimiter::Parenthesis),
 222                 rustc_lexer::TokenKind::OpenBrace => token::OpenDelim(Delimiter::Brace),
 223                 rustc_lexer::TokenKind::CloseBrace => token::CloseDelim(Delimiter::Brace),
 224                 rustc_lexer::TokenKind::OpenBracket => token::OpenDelim(Delimiter::Bracket),
 225                 rustc_lexer::TokenKind::CloseBracket => token::CloseDelim(Delimiter::Bracket),
 226                 rustc_lexer::TokenKind::At => token::At,
 227                 rustc_lexer::TokenKind::Pound => token::Pound,
 228                 rustc_lexer::TokenKind::Tilde => token::Tilde,
 229                 rustc_lexer::TokenKind::Question => token::Question,
 230                 rustc_lexer::TokenKind::Colon => token::Colon,
 231                 rustc_lexer::TokenKind::Dollar => token::Dollar,
 232                 rustc_lexer::TokenKind::Eq => token::Eq,
 233                 rustc_lexer::TokenKind::Bang => token::Not,
 234                 rustc_lexer::TokenKind::Lt => token::Lt,
 235                 rustc_lexer::TokenKind::Gt => token::Gt,
 236                 rustc_lexer::TokenKind::Minus => token::BinOp(token::Minus),
 237                 rustc_lexer::TokenKind::And => token::BinOp(token::And),
 238                 rustc_lexer::TokenKind::Or => token::BinOp(token::Or),
 239                 rustc_lexer::TokenKind::Plus => token::BinOp(token::Plus),
 240                 rustc_lexer::TokenKind::Star => token::BinOp(token::Star),
 241                 rustc_lexer::TokenKind::Slash => token::BinOp(token::Slash),
 242                 rustc_lexer::TokenKind::Caret => token::BinOp(token::Caret),
 243                 rustc_lexer::TokenKind::Percent => token::BinOp(token::Percent),
 244
 245                 rustc_lexer::TokenKind::Unknown | rustc_lexer::TokenKind::InvalidIdent => {
 246                     // Don't emit diagnostics for sequences of the same invalid token
 247                     if swallow_next_invalid > 0 {
 248                         swallow_next_invalid -= 1;
 249                         continue;
 250                     }
 251                     let mut it = self.str_from_to_end(start).chars();
 252                     let c = it.next().unwrap();
 253                     if c == '\u{00a0}' {
 254                         // If an error has already been reported on non-breaking
 255                         // space characters earlier in the file, treat all
 256                         // subsequent occurrences as whitespace.
 257                         if self.nbsp_is_whitespace {
 258                             preceded_by_whitespace = true;
 259                             continue;
 260                         }
 261                         self.nbsp_is_whitespace = true;
 262                     }
 263                     let repeats = it.take_while(|c1| *c1 == c).count();
 264                     let mut err =
 265                         self.struct_err_span_char(start, self.pos + Pos::from_usize(repeats * c.len_utf8()), "unknown start of token", c);
 266                     // FIXME: the lexer could be used to turn the ASCII version of unicode
 267                     // homoglyphs, instead of keeping a table in `check_for_substitution`into the
 268                     // token. Ideally, this should be inside `rustc_lexer`. However, we should
 269                     // first remove compound tokens like `<<` from `rustc_lexer`, and then add
 270                     // fancier error recovery to it, as there will be less overall work to do this
 271                     // way.
 272                     let token = unicode_chars::check_for_substitution(self, start, c, &mut err, repeats+1);
 273                     if c == '\x00' {
 274                         err.help("source files must contain UTF-8 encoded text, unexpected null bytes might occur when a different encoding is used");
 275                     }
 276                     if repeats > 0 {
 277                         if repeats == 1 {
 278                             err.note(format!("character appears once more"));
 279                         } else {
 280                             err.note(format!("character appears {repeats} more times"));
 281                         }
 282                         swallow_next_invalid = repeats;
 283                     }
 284                     err.emit();
 285                     if let Some(token) = token {
 286                         token
 287                     } else {
 288                         preceded_by_whitespace = true;
 289                         continue;
 290                     }
 291                 }
 292                 rustc_lexer::TokenKind::Eof => token::Eof,
 293             };
 294             let span = self.mk_sp(start, self.pos);
 295             return (Token::new(kind, span), preceded_by_whitespace);
 296         }
 297     }
 298
 299     /// Report a fatal lexical error with a given span.
 300     fn fatal_span(&self, sp: Span, m: &str) -> ! {
 301         self.sess.span_diagnostic.span_fatal(sp, m)
 302     }
 303
 304     /// Report a lexical error with a given span.
 305     fn err_span(&self, sp: Span, m: &str) {
 306         self.sess.span_diagnostic.struct_span_err(sp, m).emit();
 307     }
 308
 309     /// Report a fatal error spanning [`from_pos`, `to_pos`).
 310     fn fatal_span_(&self, from_pos: BytePos, to_pos: BytePos, m: &str) -> ! {
 311         self.fatal_span(self.mk_sp(from_pos, to_pos), m)
 312     }
 313
 314     /// Report a lexical error spanning [`from_pos`, `to_pos`).
 315     fn err_span_(&self, from_pos: BytePos, to_pos: BytePos, m: &str) {
 316         self.err_span(self.mk_sp(from_pos, to_pos), m)
 317     }
 318
 319     fn struct_fatal_span_char(
 320         &self,
 321         from_pos: BytePos,
 322         to_pos: BytePos,
 323         m: &str,
 324         c: char,
 325     ) -> DiagnosticBuilder<'a, !> {
 326         self.sess
 327             .span_diagnostic
 328             .struct_span_fatal(self.mk_sp(from_pos, to_pos), &format!("{}: {}", m, escaped_char(c)))
 329     }
 330
 331     fn struct_err_span_char(
 332         &self,
 333         from_pos: BytePos,
 334         to_pos: BytePos,
 335         m: &str,
 336         c: char,
 337     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
 338         self.sess
 339             .span_diagnostic
 340             .struct_span_err(self.mk_sp(from_pos, to_pos), &format!("{}: {}", m, escaped_char(c)))
 341     }
 342
 343     /// Detect usages of Unicode codepoints changing the direction of the text on screen and loudly
 344     /// complain about it.
 345     fn lint_unicode_text_flow(&self, start: BytePos) {
 346         // Opening delimiter of the length 2 is not included into the comment text.
 347         let content_start = start + BytePos(2);
 348         let content = self.str_from(content_start);
 349         if contains_text_flow_control_chars(content) {
 350             let span = self.mk_sp(start, self.pos);
 351             self.sess.buffer_lint_with_diagnostic(
 352                 &TEXT_DIRECTION_CODEPOINT_IN_COMMENT,
 353                 span,
 354                 ast::CRATE_NODE_ID,
 355                 "unicode codepoint changing visible direction of text present in comment",
 356                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content.to_string()),
 357             );
 358         }
 359     }
 360
 361     fn cook_doc_comment(
 362         &self,
 363         content_start: BytePos,
 364         content: &str,
 365         comment_kind: CommentKind,
 366         doc_style: DocStyle,
 367     ) -> TokenKind {
 368         if content.contains('\r') {
 369             for (idx, _) in content.char_indices().filter(|&(_, c)| c == '\r') {
 370                 self.err_span_(
 371                     content_start + BytePos(idx as u32),
 372                     content_start + BytePos(idx as u32 + 1),
 373                     match comment_kind {
 374                         CommentKind::Line => "bare CR not allowed in doc-comment",
 375                         CommentKind::Block => "bare CR not allowed in block doc-comment",
 376                     },
 377                 );
 378             }
 379         }
 380
 381         let attr_style = match doc_style {
 382             DocStyle::Outer => AttrStyle::Outer,
 383             DocStyle::Inner => AttrStyle::Inner,
 384         };
 385
 386         token::DocComment(comment_kind, attr_style, Symbol::intern(content))
 387     }
 388
 389     fn cook_lexer_literal(
 390         &self,
 391         start: BytePos,
 392         end: BytePos,
 393         kind: rustc_lexer::LiteralKind,
 394     ) -> (token::LitKind, Symbol) {
 395         match kind {
 396             rustc_lexer::LiteralKind::Char { terminated } => {
 397                 if !terminated {
 398                     self.sess.span_diagnostic.span_fatal_with_code(
 399                         self.mk_sp(start, end),
 400                         "unterminated character literal",
 401                         error_code!(E0762),
 402                     )
 403                 }
 404                 self.cook_quoted(token::Char, Mode::Char, start, end, 1, 1) // ' '
 405             }
 406             rustc_lexer::LiteralKind::Byte { terminated } => {
 407                 if !terminated {
 408                     self.sess.span_diagnostic.span_fatal_with_code(
 409                         self.mk_sp(start + BytePos(1), end),
 410                         "unterminated byte constant",
 411                         error_code!(E0763),
 412                     )
 413                 }
 414                 self.cook_quoted(token::Byte, Mode::Byte, start, end, 2, 1) // b' '
 415             }
 416             rustc_lexer::LiteralKind::Str { terminated } => {
 417                 if !terminated {
 418                     self.sess.span_diagnostic.span_fatal_with_code(
 419                         self.mk_sp(start, end),
 420                         "unterminated double quote string",
 421                         error_code!(E0765),
 422                     )
 423                 }
 424                 self.cook_quoted(token::Str, Mode::Str, start, end, 1, 1) // " "
 425             }
 426             rustc_lexer::LiteralKind::ByteStr { terminated } => {
 427                 if !terminated {
 428                     self.sess.span_diagnostic.span_fatal_with_code(
 429                         self.mk_sp(start + BytePos(1), end),
 430                         "unterminated double quote byte string",
 431                         error_code!(E0766),
 432                     )
 433                 }
 434                 self.cook_quoted(token::ByteStr, Mode::ByteStr, start, end, 2, 1) // b" "
 435             }
 436             rustc_lexer::LiteralKind::RawStr { n_hashes } => {
 437                 if let Some(n_hashes) = n_hashes {
 438                     let n = u32::from(n_hashes);
 439                     let kind = token::StrRaw(n_hashes);
 440                     self.cook_quoted(kind, Mode::RawStr, start, end, 2 + n, 1 + n) // r##" "##
 441                 } else {
 442                     self.report_raw_str_error(start, 1);
 443                 }
 444             }
 445             rustc_lexer::LiteralKind::RawByteStr { n_hashes } => {
 446                 if let Some(n_hashes) = n_hashes {
 447                     let n = u32::from(n_hashes);
 448                     let kind = token::ByteStrRaw(n_hashes);
 449                     self.cook_quoted(kind, Mode::RawByteStr, start, end, 3 + n, 1 + n) // br##" "##
 450                 } else {
 451                     self.report_raw_str_error(start, 2);
 452                 }
 453             }
 454             rustc_lexer::LiteralKind::Int { base, empty_int } => {
 455                 if empty_int {
 456                     self.sess
 457                         .span_diagnostic
 458                         .struct_span_err_with_code(
 459                             self.mk_sp(start, end),
 460                             "no valid digits found for number",
 461                             error_code!(E0768),
 462                         )
 463                         .emit();
 464                     (token::Integer, sym::integer(0))
 465                 } else {
 466                     if matches!(base, Base::Binary | Base::Octal) {
 467                         let base = base as u32;
 468                         let s = self.str_from_to(start + BytePos(2), end);
 469                         for (idx, c) in s.char_indices() {
 470                             if c != '_' && c.to_digit(base).is_none() {
 471                                 self.err_span_(
 472                                     start + BytePos::from_usize(2 + idx),
 473                                     start + BytePos::from_usize(2 + idx + c.len_utf8()),
 474                                     &format!("invalid digit for a base {} literal", base),
 475                                 );
 476                             }
 477                         }
 478                     }
 479                     (token::Integer, self.symbol_from_to(start, end))
 480                 }
 481             }
 482             rustc_lexer::LiteralKind::Float { base, empty_exponent } => {
 483                 if empty_exponent {
 484                     self.err_span_(start, self.pos, "expected at least one digit in exponent");
 485                 }
 486                 match base {
 487                     Base::Hexadecimal => {
 488                         self.err_span_(start, end, "hexadecimal float literal is not supported")
 489                     }
 490                     Base::Octal => {
 491                         self.err_span_(start, end, "octal float literal is not supported")
 492                     }
 493                     Base::Binary => {
 494                         self.err_span_(start, end, "binary float literal is not supported")
 495                     }
 496                     _ => {}
 497                 }
 498                 (token::Float, self.symbol_from_to(start, end))
 499             }
 500         }
 501     }
 502
 503     #[inline]
 504     fn src_index(&self, pos: BytePos) -> usize {
 505         (pos - self.start_pos).to_usize()
 506     }
 507
 508     /// Slice of the source text from `start` up to but excluding `self.pos`,
 509     /// meaning the slice does not include the character `self.ch`.
 510     fn str_from(&self, start: BytePos) -> &'a str {
 511         self.str_from_to(start, self.pos)
 512     }
 513
 514     /// As symbol_from, with an explicit endpoint.
 515     fn symbol_from_to(&self, start: BytePos, end: BytePos) -> Symbol {
 516         debug!("taking an ident from {:?} to {:?}", start, end);
 517         Symbol::intern(self.str_from_to(start, end))
 518     }
 519
 520     /// Slice of the source text spanning from `start` up to but excluding `end`.
 521     fn str_from_to(&self, start: BytePos, end: BytePos) -> &'a str {
 522         &self.src[self.src_index(start)..self.src_index(end)]
 523     }
 524
 525     /// Slice of the source text spanning from `start` until the end
 526     fn str_from_to_end(&self, start: BytePos) -> &'a str {
 527         &self.src[self.src_index(start)..]
 528     }
 529
 530     fn report_raw_str_error(&self, start: BytePos, prefix_len: u32) -> ! {
 531         match rustc_lexer::validate_raw_str(self.str_from(start), prefix_len) {
 532             Err(RawStrError::InvalidStarter { bad_char }) => {
 533                 self.report_non_started_raw_string(start, bad_char)
 534             }
 535             Err(RawStrError::NoTerminator { expected, found, possible_terminator_offset }) => self
 536                 .report_unterminated_raw_string(start, expected, possible_terminator_offset, found),
 537             Err(RawStrError::TooManyDelimiters { found }) => {
 538                 self.report_too_many_hashes(start, found)
 539             }
 540             Ok(()) => panic!("no error found for supposedly invalid raw string literal"),
 541         }
 542     }
 543
 544     fn report_non_started_raw_string(&self, start: BytePos, bad_char: char) -> ! {
 545         self.struct_fatal_span_char(
 546             start,
 547             self.pos,
 548             "found invalid character; only `#` is allowed in raw string delimitation",
 549             bad_char,
 550         )
 551         .emit()
 552     }
 553
 554     fn report_unterminated_raw_string(
 555         &self,
 556         start: BytePos,
 557         n_hashes: u32,
 558         possible_offset: Option<u32>,
 559         found_terminators: u32,
 560     ) -> ! {
 561         let mut err = self.sess.span_diagnostic.struct_span_fatal_with_code(
 562             self.mk_sp(start, start),
 563             "unterminated raw string",
 564             error_code!(E0748),
 565         );
 566
 567         err.span_label(self.mk_sp(start, start), "unterminated raw string");
 568
 569         if n_hashes > 0 {
 570             err.note(&format!(
 571                 "this raw string should be terminated with `\"{}`",
 572                 "#".repeat(n_hashes as usize)
 573             ));
 574         }
 575
 576         if let Some(possible_offset) = possible_offset {
 577             let lo = start + BytePos(possible_offset as u32);
 578             let hi = lo + BytePos(found_terminators as u32);
 579             let span = self.mk_sp(lo, hi);
 580             err.span_suggestion(
 581                 span,
 582                 "consider terminating the string here",
 583                 "#".repeat(n_hashes as usize),
 584                 Applicability::MaybeIncorrect,
 585             );
 586         }
 587
 588         err.emit()
 589     }
 590
 591     fn report_unterminated_block_comment(&self, start: BytePos, doc_style: Option<DocStyle>) {
 592         let msg = match doc_style {
 593             Some(_) => "unterminated block doc-comment",
 594             None => "unterminated block comment",
 595         };
 596         let last_bpos = self.pos;
 597         let mut err = self.sess.span_diagnostic.struct_span_fatal_with_code(
 598             self.mk_sp(start, last_bpos),
 599             msg,
 600             error_code!(E0758),
 601         );
 602         let mut nested_block_comment_open_idxs = vec![];
 603         let mut last_nested_block_comment_idxs = None;
 604         let mut content_chars = self.str_from(start).char_indices().peekable();
 605
 606         while let Some((idx, current_char)) = content_chars.next() {
 607             match content_chars.peek() {
 608                 Some((_, '*')) if current_char == '/' => {
 609                     nested_block_comment_open_idxs.push(idx);
 610                 }
 611                 Some((_, '/')) if current_char == '*' => {
 612                     last_nested_block_comment_idxs =
 613                         nested_block_comment_open_idxs.pop().map(|open_idx| (open_idx, idx));
 614                 }
 615                 _ => {}
 616             };
 617         }
 618
 619         if let Some((nested_open_idx, nested_close_idx)) = last_nested_block_comment_idxs {
 620             err.span_label(self.mk_sp(start, start + BytePos(2)), msg)
 621                 .span_label(
 622                     self.mk_sp(
 623                         start + BytePos(nested_open_idx as u32),
 624                         start + BytePos(nested_open_idx as u32 + 2),
 625                     ),
 626                     "...as last nested comment starts here, maybe you want to close this instead?",
 627                 )
 628                 .span_label(
 629                     self.mk_sp(
 630                         start + BytePos(nested_close_idx as u32),
 631                         start + BytePos(nested_close_idx as u32 + 2),
 632                     ),
 633                     "...and last nested comment terminates here.",
 634                 );
 635         }
 636
 637         err.emit();
 638     }
 639
 640     // RFC 3101 introduced the idea of (reserved) prefixes. As of Rust 2021,
 641     // using a (unknown) prefix is an error. In earlier editions, however, they
 642     // only result in a (allowed by default) lint, and are treated as regular
 643     // identifier tokens.
 644     fn report_unknown_prefix(&self, start: BytePos) {
 645         let prefix_span = self.mk_sp(start, self.pos);
 646         let prefix_str = self.str_from_to(start, self.pos);
 647         let msg = format!("prefix `{}` is unknown", prefix_str);
 648
 649         let expn_data = prefix_span.ctxt().outer_expn_data();
 650
 651         if expn_data.edition >= Edition::Edition2021 {
 652             // In Rust 2021, this is a hard error.
 653             let mut err = self.sess.span_diagnostic.struct_span_err(prefix_span, &msg);
 654             err.span_label(prefix_span, "unknown prefix");
 655             if prefix_str == "rb" {
 656                 err.span_suggestion_verbose(
 657                     prefix_span,
 658                     "use `br` for a raw byte string",
 659                     "br",
 660                     Applicability::MaybeIncorrect,
 661                 );
 662             } else if expn_data.is_root() {
 663                 err.span_suggestion_verbose(
 664                     prefix_span.shrink_to_hi(),
 665                     "consider inserting whitespace here",
 666                     " ",
 667                     Applicability::MaybeIncorrect,
 668                 );
 669             }
 670             err.note("prefixed identifiers and literals are reserved since Rust 2021");
 671             err.emit();
 672         } else {
 673             // Before Rust 2021, only emit a lint for migration.
 674             self.sess.buffer_lint_with_diagnostic(
 675                 &RUST_2021_PREFIXES_INCOMPATIBLE_SYNTAX,
 676                 prefix_span,
 677                 ast::CRATE_NODE_ID,
 678                 &msg,
 679                 BuiltinLintDiagnostics::ReservedPrefix(prefix_span),
 680             );
 681         }
 682     }
 683
 684     fn report_too_many_hashes(&self, start: BytePos, found: u32) -> ! {
 685         self.fatal_span_(
 686             start,
 687             self.pos,
 688             &format!(
 689                 "too many `#` symbols: raw strings may be delimited \
 690                 by up to 255 `#` symbols, but found {}",
 691                 found
 692             ),
 693         )
 694     }
 695
 696     fn cook_quoted(
 697         &self,
 698         kind: token::LitKind,
 699         mode: Mode,
 700         start: BytePos,
 701         end: BytePos,
 702         prefix_len: u32,
 703         postfix_len: u32,
 704     ) -> (token::LitKind, Symbol) {
 705         let mut has_fatal_err = false;
 706         let content_start = start + BytePos(prefix_len);
 707         let content_end = end - BytePos(postfix_len);
 708         let lit_content = self.str_from_to(content_start, content_end);
 709         unescape::unescape_literal(lit_content, mode, &mut |range, result| {
 710             // Here we only check for errors. The actual unescaping is done later.
 711             if let Err(err) = result {
 712                 let span_with_quotes = self.mk_sp(start, end);
 713                 let (start, end) = (range.start as u32, range.end as u32);
 714                 let lo = content_start + BytePos(start);
 715                 let hi = lo + BytePos(end - start);
 716                 let span = self.mk_sp(lo, hi);
 717                 if err.is_fatal() {
 718                     has_fatal_err = true;
 719                 }
 720                 emit_unescape_error(
 721                     &self.sess.span_diagnostic,
 722                     lit_content,
 723                     span_with_quotes,
 724                     span,
 725                     mode,
 726                     range,
 727                     err,
 728                 );
 729             }
 730         });
 731
 732         // We normally exclude the quotes for the symbol, but for errors we
 733         // include it because it results in clearer error messages.
 734         if !has_fatal_err {
 735             (kind, Symbol::intern(lit_content))
 736         } else {
 737             (token::Err, self.symbol_from_to(start, end))
 738         }
 739     }
 740 }
 741
 742 pub fn nfc_normalize(string: &str) -> Symbol {
 743     use unicode_normalization::{is_nfc_quick, IsNormalized, UnicodeNormalization};
 744     match is_nfc_quick(string.chars()) {
 745         IsNormalized::Yes => Symbol::intern(string),
 746         _ => {
 747             let normalized_str: String = string.chars().nfc().collect();
 748             Symbol::intern(&normalized_str)
 749         }
 750     }
 751 }