1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443
use super::{ForceCollect, Parser, PathStyle, Restrictions, Trailing};
use crate::errors::{
self, AmbiguousRangePattern, DotDotDotForRemainingFields, DotDotDotRangeToPatternNotAllowed,
DotDotDotRestPattern, EnumPatternInsteadOfIdentifier, ExpectedBindingLeftOfAt,
ExpectedCommaAfterPatternField, GenericArgsInPatRequireTurbofishSyntax,
InclusiveRangeExtraEquals, InclusiveRangeMatchArrow, InclusiveRangeNoEnd, InvalidMutInPattern,
ParenRangeSuggestion, PatternOnWrongSideOfAt, RemoveLet, RepeatedMutInPattern,
SwitchRefBoxOrder, TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg,
TrailingVertNotAllowed, UnexpectedExpressionInPattern, UnexpectedLifetimeInPattern,
UnexpectedParenInRangePat, UnexpectedParenInRangePatSugg,
UnexpectedVertVertBeforeFunctionParam, UnexpectedVertVertInPattern, WrapInParens,
};
use crate::parser::expr::{could_be_unclosed_char_literal, LhsExpr};
use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
use rustc_ast::mut_visit::{noop_visit_pat, MutVisitor};
use rustc_ast::ptr::P;
use rustc_ast::token::{self, BinOpToken, Delimiter, Token};
use rustc_ast::{
self as ast, AttrVec, BindingMode, ByRef, Expr, ExprKind, MacCall, Mutability, Pat, PatField,
PatFieldsRest, PatKind, Path, QSelf, RangeEnd, RangeSyntax,
};
use rustc_ast_pretty::pprust;
use rustc_errors::{Applicability, Diag, PResult};
use rustc_session::errors::ExprParenthesesNeeded;
use rustc_span::source_map::{respan, Spanned};
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{BytePos, ErrorGuaranteed, Span};
use thin_vec::{thin_vec, ThinVec};
#[derive(PartialEq, Copy, Clone)]
pub enum Expected {
ParameterName,
ArgumentName,
Identifier,
BindingPattern,
}
impl Expected {
// FIXME(#100717): migrate users of this to proper localization
fn to_string_or_fallback(expected: Option<Expected>) -> &'static str {
match expected {
Some(Expected::ParameterName) => "parameter name",
Some(Expected::ArgumentName) => "argument name",
Some(Expected::Identifier) => "identifier",
Some(Expected::BindingPattern) => "binding pattern",
None => "pattern",
}
}
}
const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here";
/// Whether or not to recover a `,` when parsing or-patterns.
#[derive(PartialEq, Copy, Clone)]
pub enum RecoverComma {
Yes,
No,
}
/// Whether or not to recover a `:` when parsing patterns that were meant to be paths.
#[derive(PartialEq, Copy, Clone)]
pub enum RecoverColon {
Yes,
No,
}
/// Whether or not to recover a `a, b` when parsing patterns as `(a, b)` or that *and* `a | b`.
#[derive(PartialEq, Copy, Clone)]
pub enum CommaRecoveryMode {
LikelyTuple,
EitherTupleOrPipe,
}
/// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid
/// emitting duplicate diagnostics.
#[derive(Debug, Clone, Copy)]
enum EatOrResult {
/// We recovered from a trailing vert.
TrailingVert,
/// We ate an `|` (or `||` and recovered).
AteOr,
/// We did not eat anything (i.e. the current token is not `|` or `||`).
None,
}
/// The syntax location of a given pattern. Used for diagnostics.
#[derive(Clone, Copy)]
pub enum PatternLocation {
LetBinding,
FunctionParameter,
}
impl<'a> Parser<'a> {
/// Parses a pattern.
///
/// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
/// at the top level. Used when parsing the parameters of lambda expressions,
/// functions, function pointers, and `pat` macro fragments.
pub fn parse_pat_no_top_alt(
&mut self,
expected: Option<Expected>,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, P<Pat>> {
self.parse_pat_with_range_pat(true, expected, syntax_loc)
}
/// Parses a pattern.
///
/// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
/// Used for parsing patterns in all cases when `pat<no_top_alt>` is not used.
///
/// Note that after the FCP in <https://github.com/rust-lang/rust/issues/81415>,
/// a leading vert is allowed in nested or-patterns, too. This allows us to
/// simplify the grammar somewhat.
pub fn parse_pat_allow_top_alt(
&mut self,
expected: Option<Expected>,
rc: RecoverComma,
ra: RecoverColon,
rt: CommaRecoveryMode,
) -> PResult<'a, P<Pat>> {
self.parse_pat_allow_top_alt_inner(expected, rc, ra, rt, None).map(|(pat, _)| pat)
}
/// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true =
/// recovered).
fn parse_pat_allow_top_alt_inner(
&mut self,
expected: Option<Expected>,
rc: RecoverComma,
ra: RecoverColon,
rt: CommaRecoveryMode,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, (P<Pat>, bool)> {
// Keep track of whether we recovered from a trailing vert so that we can avoid duplicated
// suggestions (which bothers rustfix).
//
// Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
let (leading_vert_span, mut trailing_vert) = match self.eat_or_separator(None) {
EatOrResult::AteOr => (Some(self.prev_token.span), false),
EatOrResult::TrailingVert => (None, true),
EatOrResult::None => (None, false),
};
// Parse the first pattern (`p_0`).
let mut first_pat = match self.parse_pat_no_top_alt(expected, syntax_loc) {
Ok(pat) => pat,
Err(err)
if self.token.is_reserved_ident()
&& !self.token.is_keyword(kw::In)
&& !self.token.is_keyword(kw::If) =>
{
err.emit();
self.bump();
self.mk_pat(self.token.span, PatKind::Wild)
}
Err(err) => return Err(err),
};
if rc == RecoverComma::Yes && !first_pat.could_be_never_pattern() {
self.maybe_recover_unexpected_comma(first_pat.span, rt)?;
}
// If the next token is not a `|`,
// this is not an or-pattern and we should exit here.
if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr {
// If we parsed a leading `|` which should be gated,
// then we should really gate the leading `|`.
// This complicated procedure is done purely for diagnostics UX.
// Check if the user wrote `foo:bar` instead of `foo::bar`.
if ra == RecoverColon::Yes {
first_pat = self.maybe_recover_colon_colon_in_pat_typo(first_pat, expected);
}
if let Some(leading_vert_span) = leading_vert_span {
// If there was a leading vert, treat this as an or-pattern. This improves
// diagnostics.
let span = leading_vert_span.to(self.prev_token.span);
return Ok((self.mk_pat(span, PatKind::Or(thin_vec![first_pat])), trailing_vert));
}
return Ok((first_pat, trailing_vert));
}
// Parse the patterns `p_1 | ... | p_n` where `n > 0`.
let lo = leading_vert_span.unwrap_or(first_pat.span);
let mut pats = thin_vec![first_pat];
loop {
match self.eat_or_separator(Some(lo)) {
EatOrResult::AteOr => {}
EatOrResult::None => break,
EatOrResult::TrailingVert => {
trailing_vert = true;
break;
}
}
let pat = self.parse_pat_no_top_alt(expected, syntax_loc).map_err(|mut err| {
err.span_label(lo, WHILE_PARSING_OR_MSG);
err
})?;
if rc == RecoverComma::Yes && !pat.could_be_never_pattern() {
self.maybe_recover_unexpected_comma(pat.span, rt)?;
}
pats.push(pat);
}
let or_pattern_span = lo.to(self.prev_token.span);
Ok((self.mk_pat(or_pattern_span, PatKind::Or(pats)), trailing_vert))
}
/// Parse a pattern and (maybe) a `Colon` in positions where a pattern may be followed by a
/// type annotation (e.g. for `let` bindings or `fn` params).
///
/// Generally, this corresponds to `pat_no_top_alt` followed by an optional `Colon`. It will
/// eat the `Colon` token if one is present.
///
/// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
/// otherwise).
pub(super) fn parse_pat_before_ty(
&mut self,
expected: Option<Expected>,
rc: RecoverComma,
syntax_loc: PatternLocation,
) -> PResult<'a, (P<Pat>, bool)> {
// We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level
// or-patterns so that we can detect when a user tries to use it. This allows us to print a
// better error message.
let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner(
expected,
rc,
RecoverColon::No,
CommaRecoveryMode::LikelyTuple,
Some(syntax_loc),
)?;
let colon = self.eat(&token::Colon);
if let PatKind::Or(pats) = &pat.kind {
let span = pat.span;
let sub = if pats.len() == 1 {
Some(TopLevelOrPatternNotAllowedSugg::RemoveLeadingVert {
span: span.with_hi(span.lo() + BytePos(1)),
})
} else {
Some(TopLevelOrPatternNotAllowedSugg::WrapInParens {
span,
suggestion: WrapInParens { lo: span.shrink_to_lo(), hi: span.shrink_to_hi() },
})
};
let err = self.dcx().create_err(match syntax_loc {
PatternLocation::LetBinding => {
TopLevelOrPatternNotAllowed::LetBinding { span, sub }
}
PatternLocation::FunctionParameter => {
TopLevelOrPatternNotAllowed::FunctionParameter { span, sub }
}
});
if trailing_vert {
err.delay_as_bug();
} else {
err.emit();
}
}
Ok((pat, colon))
}
/// Parse the pattern for a function or function pointer parameter, followed by a colon.
///
/// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
/// otherwise).
pub(super) fn parse_fn_param_pat_colon(&mut self) -> PResult<'a, (P<Pat>, bool)> {
// In order to get good UX, we first recover in the case of a leading vert for an illegal
// top-level or-pat. Normally, this means recovering both `|` and `||`, but in this case,
// a leading `||` probably doesn't indicate an or-pattern attempt, so we handle that
// separately.
if let token::OrOr = self.token.kind {
self.dcx().emit_err(UnexpectedVertVertBeforeFunctionParam { span: self.token.span });
self.bump();
}
self.parse_pat_before_ty(
Some(Expected::ParameterName),
RecoverComma::No,
PatternLocation::FunctionParameter,
)
}
/// Eat the or-pattern `|` separator.
/// If instead a `||` token is encountered, recover and pretend we parsed `|`.
fn eat_or_separator(&mut self, lo: Option<Span>) -> EatOrResult {
if self.recover_trailing_vert(lo) {
EatOrResult::TrailingVert
} else if matches!(self.token.kind, token::OrOr) {
// Found `||`; Recover and pretend we parsed `|`.
self.dcx().emit_err(UnexpectedVertVertInPattern { span: self.token.span, start: lo });
self.bump();
EatOrResult::AteOr
} else if self.eat(&token::BinOp(token::Or)) {
EatOrResult::AteOr
} else {
EatOrResult::None
}
}
/// Recover if `|` or `||` is the current token and we have one of the
/// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us.
///
/// These tokens all indicate that we reached the end of the or-pattern
/// list and can now reliably say that the `|` was an illegal trailing vert.
/// Note that there are more tokens such as `@` for which we know that the `|`
/// is an illegal parse. However, the user's intent is less clear in that case.
fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool {
let is_end_ahead = self.look_ahead(1, |token| {
matches!(
&token.uninterpolate().kind,
token::FatArrow // e.g. `a | => 0,`.
| token::Ident(kw::If, token::IdentIsRaw::No) // e.g. `a | if expr`.
| token::Eq // e.g. `let a | = 0`.
| token::Semi // e.g. `let a |;`.
| token::Colon // e.g. `let a | :`.
| token::Comma // e.g. `let (a |,)`.
| token::CloseDelim(Delimiter::Bracket) // e.g. `let [a | ]`.
| token::CloseDelim(Delimiter::Parenthesis) // e.g. `let (a | )`.
| token::CloseDelim(Delimiter::Brace) // e.g. `let A { f: a | }`.
)
});
match (is_end_ahead, &self.token.kind) {
(true, token::BinOp(token::Or) | token::OrOr) => {
// A `|` or possibly `||` token shouldn't be here. Ban it.
self.dcx().emit_err(TrailingVertNotAllowed {
span: self.token.span,
start: lo,
token: self.token.clone(),
note_double_vert: matches!(self.token.kind, token::OrOr).then_some(()),
});
self.bump();
true
}
_ => false,
}
}
/// Ensures that the last parsed pattern (or pattern range bound) is not followed by a method call or an operator.
///
/// `is_end_bound` indicates whether the last parsed thing was the end bound of a range pattern (see [`parse_pat_range_end`](Self::parse_pat_range_end))
/// in order to say "expected a pattern range bound" instead of "expected a pattern";
/// ```text
/// 0..=1 + 2
/// ^^^^^
/// ```
/// Only the end bound is spanned, and this function have no idea if there were a `..=` before `pat_span`, hence the parameter.
#[must_use = "the pattern must be discarded as `PatKind::Err` if this function returns Some"]
fn maybe_recover_trailing_expr(
&mut self,
pat_span: Span,
is_end_bound: bool,
) -> Option<ErrorGuaranteed> {
if self.prev_token.is_keyword(kw::Underscore) || !self.may_recover() {
// Don't recover anything after an `_` or if recovery is disabled.
return None;
}
// Check for `.hello()`, but allow `.Hello()` to be recovered as `, Hello()` in `parse_seq_to_before_tokens()`.
let has_trailing_method = self.check_noexpect(&token::Dot)
&& self.look_ahead(1, |tok| {
tok.ident()
.and_then(|(ident, _)| ident.name.as_str().chars().next())
.is_some_and(char::is_lowercase)
})
&& self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Parenthesis));
// Check for operators.
// `|` is excluded as it is used in pattern alternatives and lambdas,
// `?` is included for error propagation,
// `[` is included for indexing operations,
// `[]` is excluded as `a[]` isn't an expression and should be recovered as `a, []` (cf. `tests/ui/parser/pat-lt-bracket-7.rs`)
let has_trailing_operator = matches!(self.token.kind, token::BinOp(op) if op != BinOpToken::Or)
|| self.token.kind == token::Question
|| (self.token.kind == token::OpenDelim(Delimiter::Bracket)
&& self.look_ahead(1, |tok| tok.kind != token::CloseDelim(Delimiter::Bracket)));
if !has_trailing_method && !has_trailing_operator {
// Nothing to recover here.
return None;
}
// Let's try to parse an expression to emit a better diagnostic.
let mut snapshot = self.create_snapshot_for_diagnostic();
snapshot.restrictions.insert(Restrictions::IS_PAT);
// Parse `?`, `.f`, `(arg0, arg1, ...)` or `[expr]` until they've all been eaten.
if let Ok(expr) = snapshot
.parse_expr_dot_or_call_with(
AttrVec::new(),
self.mk_expr(pat_span, ExprKind::Dummy), // equivalent to transforming the parsed pattern into an `Expr`
pat_span,
)
.map_err(|err| err.cancel())
{
let non_assoc_span = expr.span;
// Parse an associative expression such as `+ expr`, `% expr`, ...
// Assignements, ranges and `|` are disabled by [`Restrictions::IS_PAT`].
let lhs = LhsExpr::Parsed { expr, starts_statement: false };
if let Ok(expr) = snapshot.parse_expr_assoc_with(0, lhs).map_err(|err| err.cancel()) {
// We got a valid expression.
self.restore_snapshot(snapshot);
self.restrictions.remove(Restrictions::IS_PAT);
let is_bound = is_end_bound
// is_start_bound: either `..` or `)..`
|| self.token.is_range_separator()
|| self.token.kind == token::CloseDelim(Delimiter::Parenthesis)
&& self.look_ahead(1, Token::is_range_separator);
// Check that `parse_expr_assoc_with` didn't eat a rhs.
let is_method_call = has_trailing_method && non_assoc_span == expr.span;
return Some(self.dcx().emit_err(UnexpectedExpressionInPattern {
span: expr.span,
is_bound,
is_method_call,
}));
}
}
// We got a trailing method/operator, but we couldn't parse an expression.
None
}
/// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
/// allowed).
fn parse_pat_with_range_pat(
&mut self,
allow_range_pat: bool,
expected: Option<Expected>,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, P<Pat>> {
maybe_recover_from_interpolated_ty_qpath!(self, true);
maybe_whole!(self, NtPat, |pat| pat);
let mut lo = self.token.span;
if self.token.is_keyword(kw::Let) && self.look_ahead(1, |tok| tok.can_begin_pattern()) {
self.bump();
self.dcx().emit_err(RemoveLet { span: lo });
lo = self.token.span;
}
let pat = if self.check(&token::BinOp(token::And)) || self.token.kind == token::AndAnd {
self.parse_pat_deref(expected)?
} else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
self.parse_pat_tuple_or_parens()?
} else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
// Parse `[pat, pat,...]` as a slice pattern.
let (pats, _) = self.parse_delim_comma_seq(Delimiter::Bracket, |p| {
p.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::No,
CommaRecoveryMode::EitherTupleOrPipe,
)
})?;
PatKind::Slice(pats)
} else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
// A rest pattern `..`.
self.bump(); // `..`
PatKind::Rest
} else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) {
self.recover_dotdotdot_rest_pat(lo)
} else if let Some(form) = self.parse_range_end() {
self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
} else if self.eat(&token::Not) {
// Parse `!`
self.psess.gated_spans.gate(sym::never_patterns, self.prev_token.span);
PatKind::Never
} else if self.eat_keyword(kw::Underscore) {
// Parse `_`
PatKind::Wild
} else if self.eat_keyword(kw::Mut) {
self.parse_pat_ident_mut()?
} else if self.eat_keyword(kw::Ref) {
if self.check_keyword(kw::Box) {
// Suggest `box ref`.
let span = self.prev_token.span.to(self.token.span);
self.bump();
self.dcx().emit_err(SwitchRefBoxOrder { span });
}
// Parse ref ident @ pat / ref mut ident @ pat
let mutbl = self.parse_mutability();
self.parse_pat_ident(BindingMode(ByRef::Yes(mutbl), Mutability::Not), syntax_loc)?
} else if self.eat_keyword(kw::Box) {
self.parse_pat_box()?
} else if self.check_inline_const(0) {
// Parse `const pat`
let const_expr = self.parse_const_block(lo.to(self.token.span), true)?;
if let Some(re) = self.parse_range_end() {
self.parse_pat_range_begin_with(const_expr, re)?
} else {
PatKind::Lit(const_expr)
}
} else if self.is_builtin() {
self.parse_pat_builtin()?
}
// Don't eagerly error on semantically invalid tokens when matching
// declarative macros, as the input to those doesn't have to be
// semantically valid. For attribute/derive proc macros this is not the
// case, so doing the recovery for them is fine.
else if self.can_be_ident_pat()
|| (self.is_lit_bad_ident().is_some() && self.may_recover())
{
// Parse `ident @ pat`
// This can give false positives and parse nullary enums,
// they are dealt with later in resolve.
self.parse_pat_ident(BindingMode::NONE, syntax_loc)?
} else if self.is_start_of_pat_with_path() {
// Parse pattern starting with a path
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Pat)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Pat)?)
};
let span = lo.to(self.prev_token.span);
if qself.is_none() && self.check(&token::Not) {
self.parse_pat_mac_invoc(path)?
} else if let Some(form) = self.parse_range_end() {
let begin = self.mk_expr(span, ExprKind::Path(qself, path));
self.parse_pat_range_begin_with(begin, form)?
} else if self.check(&token::OpenDelim(Delimiter::Brace)) {
self.parse_pat_struct(qself, path)?
} else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
self.parse_pat_tuple_struct(qself, path)?
} else {
match self.maybe_recover_trailing_expr(span, false) {
Some(guar) => PatKind::Err(guar),
None => PatKind::Path(qself, path),
}
}
} else if let Some(lt) = self.token.lifetime()
// In pattern position, we're totally fine with using "next token isn't colon"
// as a heuristic. We could probably just always try to recover if it's a lifetime,
// because we never have `'a: label {}` in a pattern position anyways, but it does
// keep us from suggesting something like `let 'a: Ty = ..` => `let 'a': Ty = ..`
&& could_be_unclosed_char_literal(lt)
&& !self.look_ahead(1, |token| matches!(token.kind, token::Colon))
{
// Recover a `'a` as a `'a'` literal
let lt = self.expect_lifetime();
let (lit, _) =
self.recover_unclosed_char(lt.ident, Parser::mk_token_lit_char, |self_| {
let expected = Expected::to_string_or_fallback(expected);
let msg = format!(
"expected {}, found {}",
expected,
super::token_descr(&self_.token)
);
self_
.dcx()
.struct_span_err(self_.token.span, msg)
.with_span_label(self_.token.span, format!("expected {expected}"))
});
PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit)))
} else {
// Try to parse everything else as literal with optional minus
match self.parse_literal_maybe_minus() {
Ok(begin) => {
let begin = match self.maybe_recover_trailing_expr(begin.span, false) {
Some(guar) => self.mk_expr_err(begin.span, guar),
None => begin,
};
match self.parse_range_end() {
Some(form) => self.parse_pat_range_begin_with(begin, form)?,
None => PatKind::Lit(begin),
}
}
Err(err) => return self.fatal_unexpected_non_pat(err, expected),
}
};
let pat = self.mk_pat(lo.to(self.prev_token.span), pat);
let pat = self.maybe_recover_from_bad_qpath(pat)?;
let pat = self.recover_intersection_pat(pat)?;
if !allow_range_pat {
self.ban_pat_range_if_ambiguous(&pat)
}
Ok(pat)
}
/// Recover from a typoed `...` pattern that was encountered
/// Ref: Issue #70388
fn recover_dotdotdot_rest_pat(&mut self, lo: Span) -> PatKind {
// A typoed rest pattern `...`.
self.bump(); // `...`
// The user probably mistook `...` for a rest pattern `..`.
self.dcx().emit_err(DotDotDotRestPattern {
span: lo,
suggestion: lo.with_lo(lo.hi() - BytePos(1)),
});
PatKind::Rest
}
/// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
///
/// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
/// should already have been parsed by now at this point,
/// if the next token is `@` then we can try to parse the more general form.
///
/// Consult `parse_pat_ident` for the `binding` grammar.
///
/// The notion of intersection patterns are found in
/// e.g. [F#][and] where they are called AND-patterns.
///
/// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching
fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> {
if self.token.kind != token::At {
// Next token is not `@` so it's not going to be an intersection pattern.
return Ok(lhs);
}
// At this point we attempt to parse `@ $pat_rhs` and emit an error.
self.bump(); // `@`
let mut rhs = self.parse_pat_no_top_alt(None, None)?;
let whole_span = lhs.span.to(rhs.span);
if let PatKind::Ident(_, _, sub @ None) = &mut rhs.kind {
// The user inverted the order, so help them fix that.
let lhs_span = lhs.span;
// Move the LHS into the RHS as a subpattern.
// The RHS is now the full pattern.
*sub = Some(lhs);
self.dcx().emit_err(PatternOnWrongSideOfAt {
whole_span,
whole_pat: pprust::pat_to_string(&rhs),
pattern: lhs_span,
binding: rhs.span,
});
} else {
// The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
rhs.kind = PatKind::Wild;
self.dcx().emit_err(ExpectedBindingLeftOfAt {
whole_span,
lhs: lhs.span,
rhs: rhs.span,
});
}
rhs.span = whole_span;
Ok(rhs)
}
/// Ban a range pattern if it has an ambiguous interpretation.
fn ban_pat_range_if_ambiguous(&self, pat: &Pat) {
match pat.kind {
PatKind::Range(
..,
Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. },
) => return,
PatKind::Range(..) => {}
_ => return,
}
self.dcx().emit_err(AmbiguousRangePattern {
span: pat.span,
suggestion: ParenRangeSuggestion {
lo: pat.span.shrink_to_lo(),
hi: pat.span.shrink_to_hi(),
},
});
}
/// Parse `&pat` / `&mut pat`.
fn parse_pat_deref(&mut self, expected: Option<Expected>) -> PResult<'a, PatKind> {
self.expect_and()?;
if let Some(lifetime) = self.token.lifetime() {
self.bump(); // `'a`
self.dcx().emit_err(UnexpectedLifetimeInPattern {
span: self.prev_token.span,
symbol: lifetime.name,
suggestion: self.prev_token.span.until(self.token.span),
});
}
let mutbl = self.parse_mutability();
let subpat = self.parse_pat_with_range_pat(false, expected, None)?;
Ok(PatKind::Ref(subpat, mutbl))
}
/// Parse a tuple or parenthesis pattern.
fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
let open_paren = self.token.span;
let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
p.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::No,
CommaRecoveryMode::LikelyTuple,
)
})?;
// Here, `(pat,)` is a tuple pattern.
// For backward compatibility, `(..)` is a tuple pattern as well.
let paren_pattern =
fields.len() == 1 && !(matches!(trailing_comma, Trailing::Yes) || fields[0].is_rest());
if paren_pattern {
let pat = fields.into_iter().next().unwrap();
let close_paren = self.prev_token.span;
match &pat.kind {
// recover ranges with parentheses around the `(start)..`
PatKind::Lit(begin)
if self.may_recover()
&& let Some(form) = self.parse_range_end() =>
{
self.dcx().emit_err(UnexpectedParenInRangePat {
span: vec![open_paren, close_paren],
sugg: UnexpectedParenInRangePatSugg {
start_span: open_paren,
end_span: close_paren,
},
});
self.parse_pat_range_begin_with(begin.clone(), form)
}
// recover ranges with parentheses around the `(start)..`
PatKind::Err(guar)
if self.may_recover()
&& let Some(form) = self.parse_range_end() =>
{
self.dcx().emit_err(UnexpectedParenInRangePat {
span: vec![open_paren, close_paren],
sugg: UnexpectedParenInRangePatSugg {
start_span: open_paren,
end_span: close_paren,
},
});
self.parse_pat_range_begin_with(self.mk_expr_err(pat.span, *guar), form)
}
// (pat) with optional parentheses
_ => Ok(PatKind::Paren(pat)),
}
} else {
Ok(PatKind::Tuple(fields))
}
}
/// Parse a mutable binding with the `mut` token already eaten.
fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
let mut_span = self.prev_token.span;
self.recover_additional_muts();
let byref = self.parse_byref();
self.recover_additional_muts();
// Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
if let token::Interpolated(nt) = &self.token.kind {
if let token::NtPat(..) = &**nt {
self.expected_ident_found_err().emit();
}
}
// Parse the pattern we hope to be an identifier.
let mut pat = self.parse_pat_no_top_alt(Some(Expected::Identifier), None)?;
// If we don't have `mut $ident (@ pat)?`, error.
if let PatKind::Ident(BindingMode(br @ ByRef::No, m @ Mutability::Not), ..) = &mut pat.kind
{
// Don't recurse into the subpattern.
// `mut` on the outer binding doesn't affect the inner bindings.
*br = byref;
*m = Mutability::Mut;
} else {
// Add `mut` to any binding in the parsed pattern.
let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
self.ban_mut_general_pat(mut_span, &pat, changed_any_binding);
}
if matches!(pat.kind, PatKind::Ident(BindingMode(ByRef::Yes(_), Mutability::Mut), ..)) {
self.psess.gated_spans.gate(sym::mut_ref, pat.span);
}
Ok(pat.into_inner().kind)
}
/// Turn all by-value immutable bindings in a pattern into mutable bindings.
/// Returns `true` if any change was made.
fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
struct AddMut(bool);
impl MutVisitor for AddMut {
fn visit_pat(&mut self, pat: &mut P<Pat>) {
if let PatKind::Ident(BindingMode(ByRef::No, m @ Mutability::Not), ..) =
&mut pat.kind
{
self.0 = true;
*m = Mutability::Mut;
}
noop_visit_pat(pat, self);
}
}
let mut add_mut = AddMut(false);
add_mut.visit_pat(pat);
add_mut.0
}
/// Error on `mut $pat` where `$pat` is not an ident.
fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
self.dcx().emit_err(if changed_any_binding {
InvalidMutInPattern::NestedIdent {
span: lo.to(pat.span),
pat: pprust::pat_to_string(pat),
}
} else {
InvalidMutInPattern::NonIdent { span: lo.until(pat.span) }
});
}
/// Eat any extraneous `mut`s and error + recover if we ate any.
fn recover_additional_muts(&mut self) {
let lo = self.token.span;
while self.eat_keyword(kw::Mut) {}
if lo == self.token.span {
return;
}
self.dcx().emit_err(RepeatedMutInPattern { span: lo.to(self.prev_token.span) });
}
/// Parse macro invocation
fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
self.bump();
let args = self.parse_delim_args()?;
let mac = P(MacCall { path, args });
Ok(PatKind::MacCall(mac))
}
fn fatal_unexpected_non_pat(
&mut self,
err: Diag<'a>,
expected: Option<Expected>,
) -> PResult<'a, P<Pat>> {
err.cancel();
let expected = Expected::to_string_or_fallback(expected);
let msg = format!("expected {}, found {}", expected, super::token_descr(&self.token));
let mut err = self.dcx().struct_span_err(self.token.span, msg);
err.span_label(self.token.span, format!("expected {expected}"));
let sp = self.psess.source_map().start_point(self.token.span);
if let Some(sp) = self.psess.ambiguous_block_expr_parse.borrow().get(&sp) {
err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
}
Err(err)
}
/// Parses the range pattern end form `".." | "..." | "..=" ;`.
fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> {
let re = if self.eat(&token::DotDotDot) {
RangeEnd::Included(RangeSyntax::DotDotDot)
} else if self.eat(&token::DotDotEq) {
RangeEnd::Included(RangeSyntax::DotDotEq)
} else if self.eat(&token::DotDot) {
RangeEnd::Excluded
} else {
return None;
};
Some(respan(self.prev_token.span, re))
}
/// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`.
/// `$begin $form` has already been parsed.
fn parse_pat_range_begin_with(
&mut self,
begin: P<Expr>,
re: Spanned<RangeEnd>,
) -> PResult<'a, PatKind> {
let end = if self.is_pat_range_end_start(0) {
// Parsing e.g. `X..=Y`.
Some(self.parse_pat_range_end()?)
} else {
// Parsing e.g. `X..`.
if let RangeEnd::Included(_) = re.node {
// FIXME(Centril): Consider semantic errors instead in `ast_validation`.
self.inclusive_range_with_incorrect_end();
}
None
};
Ok(PatKind::Range(Some(begin), end, re))
}
pub(super) fn inclusive_range_with_incorrect_end(&mut self) -> ErrorGuaranteed {
let tok = &self.token;
let span = self.prev_token.span;
// If the user typed "..==" instead of "..=", we want to give them
// a specific error message telling them to use "..=".
// If they typed "..=>", suggest they use ".. =>".
// Otherwise, we assume that they meant to type a half open exclusive
// range and give them an error telling them to do that instead.
let no_space = tok.span.lo() == span.hi();
match tok.kind {
token::Eq if no_space => {
let span_with_eq = span.to(tok.span);
// Ensure the user doesn't receive unhelpful unexpected token errors
self.bump();
if self.is_pat_range_end_start(0) {
let _ = self.parse_pat_range_end().map_err(|e| e.cancel());
}
self.dcx().emit_err(InclusiveRangeExtraEquals { span: span_with_eq })
}
token::Gt if no_space => {
let after_pat = span.with_hi(span.hi() - BytePos(1)).shrink_to_hi();
self.dcx().emit_err(InclusiveRangeMatchArrow { span, arrow: tok.span, after_pat })
}
_ => self.dcx().emit_err(InclusiveRangeNoEnd {
span,
suggestion: span.with_lo(span.hi() - BytePos(1)),
}),
}
}
/// Parse a range-to pattern, `..X` or `..=X` where `X` remains to be parsed.
///
/// The form `...X` is prohibited to reduce confusion with the potential
/// expression syntax `...expr` for splatting in expressions.
fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> {
let end = self.parse_pat_range_end()?;
if let RangeEnd::Included(syn @ RangeSyntax::DotDotDot) = &mut re.node {
*syn = RangeSyntax::DotDotEq;
self.dcx().emit_err(DotDotDotRangeToPatternNotAllowed { span: re.span });
}
Ok(PatKind::Range(None, Some(end), re))
}
/// Is the token `dist` away from the current suitable as the start of a range patterns end?
fn is_pat_range_end_start(&self, dist: usize) -> bool {
self.check_inline_const(dist)
|| self.look_ahead(dist, |t| {
t.is_path_start() // e.g. `MY_CONST`;
|| t.kind == token::Dot // e.g. `.5` for recovery;
|| matches!(t.kind, token::Literal(..) | token::BinOp(token::Minus))
|| t.is_bool_lit()
|| t.is_whole_expr()
|| t.is_lifetime() // recover `'a` instead of `'a'`
|| (self.may_recover() // recover leading `(`
&& t.kind == token::OpenDelim(Delimiter::Parenthesis)
&& self.look_ahead(dist + 1, |t| t.kind != token::OpenDelim(Delimiter::Parenthesis))
&& self.is_pat_range_end_start(dist + 1))
})
}
/// Parse a range pattern end bound
fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
// recover leading `(`
let open_paren = (self.may_recover()
&& self.eat_noexpect(&token::OpenDelim(Delimiter::Parenthesis)))
.then_some(self.prev_token.span);
let bound = if self.check_inline_const(0) {
self.parse_const_block(self.token.span, true)
} else if self.check_path() {
let lo = self.token.span;
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Pat)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Pat)?)
};
let hi = self.prev_token.span;
Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path)))
} else {
self.parse_literal_maybe_minus()
}?;
let recovered = self.maybe_recover_trailing_expr(bound.span, true);
// recover trailing `)`
if let Some(open_paren) = open_paren {
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
self.dcx().emit_err(UnexpectedParenInRangePat {
span: vec![open_paren, self.prev_token.span],
sugg: UnexpectedParenInRangePatSugg {
start_span: open_paren,
end_span: self.prev_token.span,
},
});
}
Ok(match recovered {
Some(guar) => self.mk_expr_err(bound.span, guar),
None => bound,
})
}
/// Is this the start of a pattern beginning with a path?
fn is_start_of_pat_with_path(&mut self) -> bool {
self.check_path()
// Just for recovery (see `can_be_ident`).
|| self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
}
/// Would `parse_pat_ident` be appropriate here?
fn can_be_ident_pat(&mut self) -> bool {
self.check_ident()
&& !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
&& !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
// Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
&& !self.token.is_keyword(kw::In)
// Try to do something more complex?
&& self.look_ahead(1, |t| !matches!(t.kind, token::OpenDelim(Delimiter::Parenthesis) // A tuple struct pattern.
| token::OpenDelim(Delimiter::Brace) // A struct pattern.
| token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
| token::PathSep // A tuple / struct variant pattern.
| token::Not)) // A macro expanding to a pattern.
}
/// Parses `ident` or `ident @ pat`.
/// Used by the copy foo and ref foo patterns to give a good
/// error message when parsing mistakes like `ref foo(a, b)`.
fn parse_pat_ident(
&mut self,
binding_annotation: BindingMode,
syntax_loc: Option<PatternLocation>,
) -> PResult<'a, PatKind> {
let ident = self.parse_ident_common(false)?;
if self.may_recover()
&& !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))
&& self.check_noexpect(&token::Lt)
&& self.look_ahead(1, |t| t.can_begin_type())
{
return Err(self.dcx().create_err(GenericArgsInPatRequireTurbofishSyntax {
span: self.token.span,
suggest_turbofish: self.token.span.shrink_to_lo(),
}));
}
let sub = if self.eat(&token::At) {
Some(self.parse_pat_no_top_alt(Some(Expected::BindingPattern), None)?)
} else {
None
};
// Just to be friendly, if they write something like `ref Some(i)`,
// we end up here with `(` as the current token.
// This shortly leads to a parse error. Note that if there is no explicit
// binding mode then we do not end up here, because the lookahead
// will direct us over to `parse_enum_variant()`.
if self.token == token::OpenDelim(Delimiter::Parenthesis) {
return Err(self
.dcx()
.create_err(EnumPatternInsteadOfIdentifier { span: self.prev_token.span }));
}
// Check for method calls after the `ident`,
// but not `ident @ subpat` as `subpat` was already checked and `ident` continues with `@`.
let pat = if sub.is_none()
&& let Some(guar) = self.maybe_recover_trailing_expr(ident.span, false)
{
PatKind::Err(guar)
} else {
PatKind::Ident(binding_annotation, ident, sub)
};
Ok(pat)
}
/// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
fn parse_pat_struct(&mut self, qself: Option<P<QSelf>>, path: Path) -> PResult<'a, PatKind> {
if qself.is_some() {
// Feature gate the use of qualified paths in patterns
self.psess.gated_spans.gate(sym::more_qualified_paths, path.span);
}
self.bump();
let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
e.span_label(path.span, "while parsing the fields for this pattern");
e.emit();
self.recover_stmt();
// When recovering, pretend we had `Foo { .. }`, to avoid cascading errors.
(ThinVec::new(), PatFieldsRest::Rest)
});
self.bump();
Ok(PatKind::Struct(qself, path, fields, etc))
}
/// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
fn parse_pat_tuple_struct(
&mut self,
qself: Option<P<QSelf>>,
path: Path,
) -> PResult<'a, PatKind> {
let (fields, _) = self.parse_paren_comma_seq(|p| {
p.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::No,
CommaRecoveryMode::EitherTupleOrPipe,
)
})?;
if qself.is_some() {
self.psess.gated_spans.gate(sym::more_qualified_paths, path.span);
}
Ok(PatKind::TupleStruct(qself, path, fields))
}
/// Are we sure this could not possibly be the start of a pattern?
///
/// Currently, this only accounts for tokens that can follow identifiers
/// in patterns, but this can be extended as necessary.
fn isnt_pattern_start(&self) -> bool {
[
token::Eq,
token::Colon,
token::Comma,
token::Semi,
token::At,
token::OpenDelim(Delimiter::Brace),
token::CloseDelim(Delimiter::Brace),
token::CloseDelim(Delimiter::Parenthesis),
]
.contains(&self.token.kind)
}
fn parse_pat_builtin(&mut self) -> PResult<'a, PatKind> {
self.parse_builtin(|self_, _lo, ident| {
Ok(match ident.name {
// builtin#deref(PAT)
sym::deref => Some(ast::PatKind::Deref(self_.parse_pat_allow_top_alt(
None,
RecoverComma::Yes,
RecoverColon::Yes,
CommaRecoveryMode::LikelyTuple,
)?)),
_ => None,
})
})
}
/// Parses `box pat`
fn parse_pat_box(&mut self) -> PResult<'a, PatKind> {
let box_span = self.prev_token.span;
if self.isnt_pattern_start() {
let descr = super::token_descr(&self.token);
self.dcx().emit_err(errors::BoxNotPat {
span: self.token.span,
kw: box_span,
lo: box_span.shrink_to_lo(),
descr,
});
// We cannot use `parse_pat_ident()` since it will complain `box`
// is not an identifier.
let sub = if self.eat(&token::At) {
Some(self.parse_pat_no_top_alt(Some(Expected::BindingPattern), None)?)
} else {
None
};
Ok(PatKind::Ident(BindingMode::NONE, Ident::new(kw::Box, box_span), sub))
} else {
let pat = self.parse_pat_with_range_pat(false, None, None)?;
self.psess.gated_spans.gate(sym::box_patterns, box_span.to(self.prev_token.span));
Ok(PatKind::Box(pat))
}
}
/// Parses the fields of a struct-like pattern.
fn parse_pat_fields(&mut self) -> PResult<'a, (ThinVec<PatField>, PatFieldsRest)> {
let mut fields = ThinVec::new();
let mut etc = PatFieldsRest::None;
let mut ate_comma = true;
let mut delayed_err: Option<Diag<'a>> = None;
let mut first_etc_and_maybe_comma_span = None;
let mut last_non_comma_dotdot_span = None;
while self.token != token::CloseDelim(Delimiter::Brace) {
let attrs = match self.parse_outer_attributes() {
Ok(attrs) => attrs,
Err(err) => {
if let Some(delayed) = delayed_err {
delayed.emit();
}
return Err(err);
}
};
let lo = self.token.span;
// check that a comma comes after every field
if !ate_comma {
let mut err =
self.dcx().create_err(ExpectedCommaAfterPatternField { span: self.token.span });
if let Some(delayed) = delayed_err {
delayed.emit();
}
self.recover_misplaced_pattern_modifiers(&fields, &mut err);
return Err(err);
}
ate_comma = false;
if self.check(&token::DotDot)
|| self.check_noexpect(&token::DotDotDot)
|| self.check_keyword(kw::Underscore)
{
etc = PatFieldsRest::Rest;
let mut etc_sp = self.token.span;
if first_etc_and_maybe_comma_span.is_none() {
if let Some(comma_tok) = self
.look_ahead(1, |t| if *t == token::Comma { Some(t.clone()) } else { None })
{
let nw_span = self
.psess
.source_map()
.span_extend_to_line(comma_tok.span)
.trim_start(comma_tok.span.shrink_to_lo())
.map(|s| self.psess.source_map().span_until_non_whitespace(s));
first_etc_and_maybe_comma_span = nw_span.map(|s| etc_sp.to(s));
} else {
first_etc_and_maybe_comma_span =
Some(self.psess.source_map().span_until_non_whitespace(etc_sp));
}
}
self.recover_bad_dot_dot();
self.bump(); // `..` || `...` || `_`
if self.token == token::CloseDelim(Delimiter::Brace) {
break;
}
let token_str = super::token_descr(&self.token);
let msg = format!("expected `}}`, found {token_str}");
let mut err = self.dcx().struct_span_err(self.token.span, msg);
err.span_label(self.token.span, "expected `}`");
let mut comma_sp = None;
if self.token == token::Comma {
// Issue #49257
let nw_span =
self.psess.source_map().span_until_non_whitespace(self.token.span);
etc_sp = etc_sp.to(nw_span);
err.span_label(
etc_sp,
"`..` must be at the end and cannot have a trailing comma",
);
comma_sp = Some(self.token.span);
self.bump();
ate_comma = true;
}
if self.token == token::CloseDelim(Delimiter::Brace) {
// If the struct looks otherwise well formed, recover and continue.
if let Some(sp) = comma_sp {
err.span_suggestion_short(
sp,
"remove this comma",
"",
Applicability::MachineApplicable,
);
}
err.emit();
break;
} else if self.token.is_ident() && ate_comma {
// Accept fields coming after `..,`.
// This way we avoid "pattern missing fields" errors afterwards.
// We delay this error until the end in order to have a span for a
// suggested fix.
if let Some(delayed_err) = delayed_err {
delayed_err.emit();
return Err(err);
} else {
delayed_err = Some(err);
}
} else {
if let Some(err) = delayed_err {
err.emit();
}
return Err(err);
}
}
let field =
self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
let field = match this.parse_pat_field(lo, attrs) {
Ok(field) => Ok(field),
Err(err) => {
if let Some(delayed_err) = delayed_err.take() {
delayed_err.emit();
}
return Err(err);
}
}?;
ate_comma = this.eat(&token::Comma);
last_non_comma_dotdot_span = Some(this.prev_token.span);
// We just ate a comma, so there's no need to capture a trailing token.
Ok((field, false))
})?;
fields.push(field)
}
if let Some(mut err) = delayed_err {
if let Some(first_etc_span) = first_etc_and_maybe_comma_span {
if self.prev_token == token::DotDot {
// We have `.., x, ..`.
err.multipart_suggestion(
"remove the starting `..`",
vec![(first_etc_span, String::new())],
Applicability::MachineApplicable,
);
} else {
if let Some(last_non_comma_dotdot_span) = last_non_comma_dotdot_span {
// We have `.., x`.
err.multipart_suggestion(
"move the `..` to the end of the field list",
vec![
(first_etc_span, String::new()),
(
self.token.span.to(last_non_comma_dotdot_span.shrink_to_hi()),
format!("{} .. }}", if ate_comma { "" } else { "," }),
),
],
Applicability::MachineApplicable,
);
}
}
}
err.emit();
}
Ok((fields, etc))
}
/// If the user writes `S { ref field: name }` instead of `S { field: ref name }`, we suggest
/// the correct code.
fn recover_misplaced_pattern_modifiers(&self, fields: &ThinVec<PatField>, err: &mut Diag<'a>) {
if let Some(last) = fields.iter().last()
&& last.is_shorthand
&& let PatKind::Ident(binding, ident, None) = last.pat.kind
&& binding != BindingMode::NONE
&& self.token == token::Colon
// We found `ref mut? ident:`, try to parse a `name,` or `name }`.
&& let Some(name_span) = self.look_ahead(1, |t| t.is_ident().then(|| t.span))
&& self.look_ahead(2, |t| {
t == &token::Comma || t == &token::CloseDelim(Delimiter::Brace)
})
{
let span = last.pat.span.with_hi(ident.span.lo());
// We have `S { ref field: name }` instead of `S { field: ref name }`
err.multipart_suggestion(
"the pattern modifiers belong after the `:`",
vec![
(span, String::new()),
(name_span.shrink_to_lo(), binding.prefix_str().to_string()),
],
Applicability::MachineApplicable,
);
}
}
/// Recover on `...` or `_` as if it were `..` to avoid further errors.
/// See issue #46718.
fn recover_bad_dot_dot(&self) {
if self.token == token::DotDot {
return;
}
let token_str = pprust::token_to_string(&self.token);
self.dcx().emit_err(DotDotDotForRemainingFields { span: self.token.span, token_str });
}
fn parse_pat_field(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, PatField> {
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let hi;
let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
// Parsing a pattern of the form `fieldname: pat`.
let fieldname = self.parse_field_name()?;
self.bump();
let pat = self.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::No,
CommaRecoveryMode::EitherTupleOrPipe,
)?;
hi = pat.span;
(pat, fieldname, false)
} else {
// Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
let is_box = self.eat_keyword(kw::Box);
let boxed_span = self.token.span;
let mutability = self.parse_mutability();
let by_ref = self.parse_byref();
let fieldname = self.parse_field_name()?;
hi = self.prev_token.span;
let ann = BindingMode(by_ref, mutability);
let fieldpat = self.mk_pat_ident(boxed_span.to(hi), ann, fieldname);
let subpat =
if is_box { self.mk_pat(lo.to(hi), PatKind::Box(fieldpat)) } else { fieldpat };
(subpat, fieldname, true)
};
Ok(PatField {
ident: fieldname,
pat: subpat,
is_shorthand,
attrs,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
is_placeholder: false,
})
}
pub(super) fn mk_pat_ident(&self, span: Span, ann: BindingMode, ident: Ident) -> P<Pat> {
self.mk_pat(span, PatKind::Ident(ann, ident, None))
}
pub(super) fn mk_pat(&self, span: Span, kind: PatKind) -> P<Pat> {
P(Pat { kind, span, id: ast::DUMMY_NODE_ID, tokens: None })
}
}