compiler/rustc_attr/src/builtin.rs

   1 //! Parsing and validation of builtin attributes
   2
   3 use rustc_ast::{self as ast, Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem};
   4 use rustc_ast_pretty::pprust;
   5 use rustc_errors::{struct_span_err, Applicability};
   6 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
   7 use rustc_macros::HashStable_Generic;
   8 use rustc_session::parse::{feature_err, ParseSess};
   9 use rustc_session::Session;
  10 use rustc_span::hygiene::Transparency;
  11 use rustc_span::{symbol::sym, symbol::Symbol, Span};
  12 use std::num::NonZeroU32;
  13
  14 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  15     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  16 }
  17
  18 enum AttrError {
  19     MultipleItem(String),
  20     UnknownMetaItem(String, &'static [&'static str]),
  21     MissingSince,
  22     NonIdentFeature,
  23     MissingFeature,
  24     MultipleStabilityLevels,
  25     UnsupportedLiteral(&'static str, /* is_bytestr */ bool),
  26 }
  27
  28 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
  29     let diag = &sess.span_diagnostic;
  30     match error {
  31         AttrError::MultipleItem(item) => {
  32             struct_span_err!(diag, span, E0538, "multiple '{}' items", item).emit();
  33         }
  34         AttrError::UnknownMetaItem(item, expected) => {
  35             let expected = expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
  36             struct_span_err!(diag, span, E0541, "unknown meta item '{}'", item)
  37                 .span_label(span, format!("expected one of {}", expected.join(", ")))
  38                 .emit();
  39         }
  40         AttrError::MissingSince => {
  41             struct_span_err!(diag, span, E0542, "missing 'since'").emit();
  42         }
  43         AttrError::NonIdentFeature => {
  44             struct_span_err!(diag, span, E0546, "'feature' is not an identifier").emit();
  45         }
  46         AttrError::MissingFeature => {
  47             struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
  48         }
  49         AttrError::MultipleStabilityLevels => {
  50             struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
  51         }
  52         AttrError::UnsupportedLiteral(msg, is_bytestr) => {
  53             let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
  54             if is_bytestr {
  55                 if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
  56                     err.span_suggestion(
  57                         span,
  58                         "consider removing the prefix",
  59                         lint_str[1..].to_string(),
  60                         Applicability::MaybeIncorrect,
  61                     );
  62                 }
  63             }
  64             err.emit();
  65         }
  66     }
  67 }
  68
  69 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug)]
  70 pub enum InlineAttr {
  71     None,
  72     Hint,
  73     Always,
  74     Never,
  75 }
  76
  77 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
  78 pub enum InstructionSetAttr {
  79     ArmA32,
  80     ArmT32,
  81 }
  82
  83 #[derive(Clone, Encodable, Decodable, Debug)]
  84 pub enum OptimizeAttr {
  85     None,
  86     Speed,
  87     Size,
  88 }
  89
  90 #[derive(Copy, Clone, PartialEq)]
  91 pub enum UnwindAttr {
  92     Allowed,
  93     Aborts,
  94 }
  95
  96 /// Determine what `#[unwind]` attribute is present in `attrs`, if any.
  97 pub fn find_unwind_attr(sess: &Session, attrs: &[Attribute]) -> Option<UnwindAttr> {
  98     attrs.iter().fold(None, |ia, attr| {
  99         if sess.check_name(attr, sym::unwind) {
 100             if let Some(meta) = attr.meta() {
 101                 if let MetaItemKind::List(items) = meta.kind {
 102                     if items.len() == 1 {
 103                         if items[0].has_name(sym::allowed) {
 104                             return Some(UnwindAttr::Allowed);
 105                         } else if items[0].has_name(sym::aborts) {
 106                             return Some(UnwindAttr::Aborts);
 107                         }
 108                     }
 109
 110                     struct_span_err!(
 111                         sess.diagnostic(),
 112                         attr.span,
 113                         E0633,
 114                         "malformed `unwind` attribute input"
 115                     )
 116                     .span_label(attr.span, "invalid argument")
 117                     .span_suggestions(
 118                         attr.span,
 119                         "the allowed arguments are `allowed` and `aborts`",
 120                         (vec!["allowed", "aborts"])
 121                             .into_iter()
 122                             .map(|s| format!("#[unwind({})]", s)),
 123                         Applicability::MachineApplicable,
 124                     )
 125                     .emit();
 126                 }
 127             }
 128         }
 129
 130         ia
 131     })
 132 }
 133
 134 /// Represents the following attributes:
 135 ///
 136 /// - `#[stable]`
 137 /// - `#[unstable]`
 138 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 139 #[derive(HashStable_Generic)]
 140 pub struct Stability {
 141     pub level: StabilityLevel,
 142     pub feature: Symbol,
 143 }
 144
 145 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 146 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 147 #[derive(HashStable_Generic)]
 148 pub struct ConstStability {
 149     pub level: StabilityLevel,
 150     pub feature: Symbol,
 151     /// whether the function has a `#[rustc_promotable]` attribute
 152     pub promotable: bool,
 153 }
 154
 155 /// The available stability levels.
 156 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 157 #[derive(HashStable_Generic)]
 158 pub enum StabilityLevel {
 159     // Reason for the current stability level and the relevant rust-lang issue
 160     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 161     Stable { since: Symbol },
 162 }
 163
 164 impl StabilityLevel {
 165     pub fn is_unstable(&self) -> bool {
 166         matches!(self, StabilityLevel::Unstable { .. })
 167     }
 168     pub fn is_stable(&self) -> bool {
 169         matches!(self, StabilityLevel::Stable { .. })
 170     }
 171 }
 172
 173 /// Collects stability info from all stability attributes in `attrs`.
 174 /// Returns `None` if no stability attributes are found.
 175 pub fn find_stability(
 176     sess: &Session,
 177     attrs: &[Attribute],
 178     item_sp: Span,
 179 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
 180     find_stability_generic(sess, attrs.iter(), item_sp)
 181 }
 182
 183 fn find_stability_generic<'a, I>(
 184     sess: &Session,
 185     attrs_iter: I,
 186     item_sp: Span,
 187 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
 188 where
 189     I: Iterator<Item = &'a Attribute>,
 190 {
 191     use StabilityLevel::*;
 192
 193     let mut stab: Option<(Stability, Span)> = None;
 194     let mut const_stab: Option<(ConstStability, Span)> = None;
 195     let mut promotable = false;
 196
 197     let diagnostic = &sess.parse_sess.span_diagnostic;
 198
 199     'outer: for attr in attrs_iter {
 200         if ![
 201             sym::rustc_const_unstable,
 202             sym::rustc_const_stable,
 203             sym::unstable,
 204             sym::stable,
 205             sym::rustc_promotable,
 206         ]
 207         .iter()
 208         .any(|&s| attr.has_name(s))
 209         {
 210             continue; // not a stability level
 211         }
 212
 213         sess.mark_attr_used(attr);
 214
 215         let meta = attr.meta();
 216
 217         if attr.has_name(sym::rustc_promotable) {
 218             promotable = true;
 219         }
 220         // attributes with data
 221         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 222             let meta = meta.as_ref().unwrap();
 223             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 224                 if item.is_some() {
 225                     handle_errors(
 226                         &sess.parse_sess,
 227                         meta.span,
 228                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 229                     );
 230                     return false;
 231                 }
 232                 if let Some(v) = meta.value_str() {
 233                     *item = Some(v);
 234                     true
 235                 } else {
 236                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 237                     false
 238                 }
 239             };
 240
 241             let meta_name = meta.name_or_empty();
 242             match meta_name {
 243                 sym::rustc_const_unstable | sym::unstable => {
 244                     if meta_name == sym::unstable && stab.is_some() {
 245                         handle_errors(
 246                             &sess.parse_sess,
 247                             attr.span,
 248                             AttrError::MultipleStabilityLevels,
 249                         );
 250                         break;
 251                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 252                         handle_errors(
 253                             &sess.parse_sess,
 254                             attr.span,
 255                             AttrError::MultipleStabilityLevels,
 256                         );
 257                         break;
 258                     }
 259
 260                     let mut feature = None;
 261                     let mut reason = None;
 262                     let mut issue = None;
 263                     let mut issue_num = None;
 264                     let mut is_soft = false;
 265                     for meta in metas {
 266                         if let Some(mi) = meta.meta_item() {
 267                             match mi.name_or_empty() {
 268                                 sym::feature => {
 269                                     if !get(mi, &mut feature) {
 270                                         continue 'outer;
 271                                     }
 272                                 }
 273                                 sym::reason => {
 274                                     if !get(mi, &mut reason) {
 275                                         continue 'outer;
 276                                     }
 277                                 }
 278                                 sym::issue => {
 279                                     if !get(mi, &mut issue) {
 280                                         continue 'outer;
 281                                     }
 282
 283                                     // These unwraps are safe because `get` ensures the meta item
 284                                     // is a name/value pair string literal.
 285                                     issue_num = match &*issue.unwrap().as_str() {
 286                                         "none" => None,
 287                                         issue => {
 288                                             let emit_diag = |msg: &str| {
 289                                                 struct_span_err!(
 290                                                     diagnostic,
 291                                                     mi.span,
 292                                                     E0545,
 293                                                     "`issue` must be a non-zero numeric string \
 294                                                     or \"none\"",
 295                                                 )
 296                                                 .span_label(
 297                                                     mi.name_value_literal_span().unwrap(),
 298                                                     msg,
 299                                                 )
 300                                                 .emit();
 301                                             };
 302                                             match issue.parse() {
 303                                                 Ok(0) => {
 304                                                     emit_diag(
 305                                                         "`issue` must not be \"0\", \
 306                                                         use \"none\" instead",
 307                                                     );
 308                                                     continue 'outer;
 309                                                 }
 310                                                 Ok(num) => NonZeroU32::new(num),
 311                                                 Err(err) => {
 312                                                     emit_diag(&err.to_string());
 313                                                     continue 'outer;
 314                                                 }
 315                                             }
 316                                         }
 317                                     };
 318                                 }
 319                                 sym::soft => {
 320                                     if !mi.is_word() {
 321                                         let msg = "`soft` should not have any arguments";
 322                                         sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 323                                     }
 324                                     is_soft = true;
 325                                 }
 326                                 _ => {
 327                                     handle_errors(
 328                                         &sess.parse_sess,
 329                                         meta.span(),
 330                                         AttrError::UnknownMetaItem(
 331                                             pprust::path_to_string(&mi.path),
 332                                             &["feature", "reason", "issue", "soft"],
 333                                         ),
 334                                     );
 335                                     continue 'outer;
 336                                 }
 337                             }
 338                         } else {
 339                             handle_errors(
 340                                 &sess.parse_sess,
 341                                 meta.span(),
 342                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 343                             );
 344                             continue 'outer;
 345                         }
 346                     }
 347
 348                     match (feature, reason, issue) {
 349                         (Some(feature), reason, Some(_)) => {
 350                             if !rustc_lexer::is_ident(&feature.as_str()) {
 351                                 handle_errors(
 352                                     &sess.parse_sess,
 353                                     attr.span,
 354                                     AttrError::NonIdentFeature,
 355                                 );
 356                                 continue;
 357                             }
 358                             let level = Unstable { reason, issue: issue_num, is_soft };
 359                             if sym::unstable == meta_name {
 360                                 stab = Some((Stability { level, feature }, attr.span));
 361                             } else {
 362                                 const_stab = Some((
 363                                     ConstStability { level, feature, promotable: false },
 364                                     attr.span,
 365                                 ));
 366                             }
 367                         }
 368                         (None, _, _) => {
 369                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 370                             continue;
 371                         }
 372                         _ => {
 373                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 374                                 .emit();
 375                             continue;
 376                         }
 377                     }
 378                 }
 379                 sym::rustc_const_stable | sym::stable => {
 380                     if meta_name == sym::stable && stab.is_some() {
 381                         handle_errors(
 382                             &sess.parse_sess,
 383                             attr.span,
 384                             AttrError::MultipleStabilityLevels,
 385                         );
 386                         break;
 387                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 388                         handle_errors(
 389                             &sess.parse_sess,
 390                             attr.span,
 391                             AttrError::MultipleStabilityLevels,
 392                         );
 393                         break;
 394                     }
 395
 396                     let mut feature = None;
 397                     let mut since = None;
 398                     for meta in metas {
 399                         match meta {
 400                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 401                                 sym::feature => {
 402                                     if !get(mi, &mut feature) {
 403                                         continue 'outer;
 404                                     }
 405                                 }
 406                                 sym::since => {
 407                                     if !get(mi, &mut since) {
 408                                         continue 'outer;
 409                                     }
 410                                 }
 411                                 _ => {
 412                                     handle_errors(
 413                                         &sess.parse_sess,
 414                                         meta.span(),
 415                                         AttrError::UnknownMetaItem(
 416                                             pprust::path_to_string(&mi.path),
 417                                             &["since", "note"],
 418                                         ),
 419                                     );
 420                                     continue 'outer;
 421                                 }
 422                             },
 423                             NestedMetaItem::Literal(lit) => {
 424                                 handle_errors(
 425                                     &sess.parse_sess,
 426                                     lit.span,
 427                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 428                                 );
 429                                 continue 'outer;
 430                             }
 431                         }
 432                     }
 433
 434                     match (feature, since) {
 435                         (Some(feature), Some(since)) => {
 436                             let level = Stable { since };
 437                             if sym::stable == meta_name {
 438                                 stab = Some((Stability { level, feature }, attr.span));
 439                             } else {
 440                                 const_stab = Some((
 441                                     ConstStability { level, feature, promotable: false },
 442                                     attr.span,
 443                                 ));
 444                             }
 445                         }
 446                         (None, _) => {
 447                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 448                             continue;
 449                         }
 450                         _ => {
 451                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 452                             continue;
 453                         }
 454                     }
 455                 }
 456                 _ => unreachable!(),
 457             }
 458         }
 459     }
 460
 461     // Merge the const-unstable info into the stability info
 462     if promotable {
 463         if let Some((ref mut stab, _)) = const_stab {
 464             stab.promotable = promotable;
 465         } else {
 466             struct_span_err!(
 467                 diagnostic,
 468                 item_sp,
 469                 E0717,
 470                 "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
 471                 or a `rustc_const_stable` attribute"
 472             )
 473             .emit();
 474         }
 475     }
 476
 477     (stab, const_stab)
 478 }
 479
 480 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 481     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 482 }
 483
 484 /// Tests if a cfg-pattern matches the cfg set
 485 pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) -> bool {
 486     eval_condition(cfg, sess, features, &mut |cfg| {
 487         try_gate_cfg(cfg, sess, features);
 488         let error = |span, msg| {
 489             sess.span_diagnostic.span_err(span, msg);
 490             true
 491         };
 492         if cfg.path.segments.len() != 1 {
 493             return error(cfg.path.span, "`cfg` predicate key must be an identifier");
 494         }
 495         match &cfg.kind {
 496             MetaItemKind::List(..) => {
 497                 error(cfg.span, "unexpected parentheses after `cfg` predicate key")
 498             }
 499             MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 500                 handle_errors(
 501                     sess,
 502                     lit.span,
 503                     AttrError::UnsupportedLiteral(
 504                         "literal in `cfg` predicate value must be a string",
 505                         lit.kind.is_bytestr(),
 506                     ),
 507                 );
 508                 true
 509             }
 510             MetaItemKind::NameValue(..) | MetaItemKind::Word => {
 511                 let ident = cfg.ident().expect("multi-segment cfg predicate");
 512                 sess.config.contains(&(ident.name, cfg.value_str()))
 513             }
 514         }
 515     })
 516 }
 517
 518 fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
 519     let gate = find_gated_cfg(|sym| cfg.has_name(sym));
 520     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 521         gate_cfg(&gated_cfg, cfg.span, sess, feats);
 522     }
 523 }
 524
 525 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 526     let (cfg, feature, has_feature) = gated_cfg;
 527     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 528         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 529         feature_err(sess, *feature, cfg_span, &explain).emit();
 530     }
 531 }
 532
 533 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 534 struct Version {
 535     major: u16,
 536     minor: u16,
 537     patch: u16,
 538 }
 539
 540 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 541     let mut components = s.split('-');
 542     let d = components.next()?;
 543     if !allow_appendix && components.next().is_some() {
 544         return None;
 545     }
 546     let mut digits = d.splitn(3, '.');
 547     let major = digits.next()?.parse().ok()?;
 548     let minor = digits.next()?.parse().ok()?;
 549     let patch = digits.next().unwrap_or("0").parse().ok()?;
 550     Some(Version { major, minor, patch })
 551 }
 552
 553 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 554 /// evaluate individual items.
 555 pub fn eval_condition(
 556     cfg: &ast::MetaItem,
 557     sess: &ParseSess,
 558     features: Option<&Features>,
 559     eval: &mut impl FnMut(&ast::MetaItem) -> bool,
 560 ) -> bool {
 561     match cfg.kind {
 562         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 563             try_gate_cfg(cfg, sess, features);
 564             let (min_version, span) = match &mis[..] {
 565                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 566                     (sym, span)
 567                 }
 568                 [NestedMetaItem::Literal(Lit { span, .. })
 569                 | NestedMetaItem::MetaItem(MetaItem { span, .. })] => {
 570                     sess.span_diagnostic
 571                         .struct_span_err(*span, "expected a version literal")
 572                         .emit();
 573                     return false;
 574                 }
 575                 [..] => {
 576                     sess.span_diagnostic
 577                         .struct_span_err(cfg.span, "expected single version literal")
 578                         .emit();
 579                     return false;
 580                 }
 581             };
 582             let min_version = match parse_version(&min_version.as_str(), false) {
 583                 Some(ver) => ver,
 584                 None => {
 585                     sess.span_diagnostic
 586                         .struct_span_warn(
 587                             *span,
 588                             "unknown version literal format, assuming it refers to a future version",
 589                         )
 590                         .emit();
 591                     return false;
 592                 }
 593             };
 594             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 595
 596             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 597             if sess.assume_incomplete_release {
 598                 rustc_version > min_version
 599             } else {
 600                 rustc_version >= min_version
 601             }
 602         }
 603         ast::MetaItemKind::List(ref mis) => {
 604             for mi in mis.iter() {
 605                 if !mi.is_meta_item() {
 606                     handle_errors(
 607                         sess,
 608                         mi.span(),
 609                         AttrError::UnsupportedLiteral("unsupported literal", false),
 610                     );
 611                     return false;
 612                 }
 613             }
 614
 615             // The unwraps below may look dangerous, but we've already asserted
 616             // that they won't fail with the loop above.
 617             match cfg.name_or_empty() {
 618                 sym::any => mis
 619                     .iter()
 620                     .any(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 621                 sym::all => mis
 622                     .iter()
 623                     .all(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 624                 sym::not => {
 625                     if mis.len() != 1 {
 626                         struct_span_err!(
 627                             sess.span_diagnostic,
 628                             cfg.span,
 629                             E0536,
 630                             "expected 1 cfg-pattern"
 631                         )
 632                         .emit();
 633                         return false;
 634                     }
 635
 636                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 637                 }
 638                 _ => {
 639                     struct_span_err!(
 640                         sess.span_diagnostic,
 641                         cfg.span,
 642                         E0537,
 643                         "invalid predicate `{}`",
 644                         pprust::path_to_string(&cfg.path)
 645                     )
 646                     .emit();
 647                     false
 648                 }
 649             }
 650         }
 651         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => eval(cfg),
 652     }
 653 }
 654
 655 #[derive(Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 656 pub struct Deprecation {
 657     pub since: Option<Symbol>,
 658     /// The note to issue a reason.
 659     pub note: Option<Symbol>,
 660     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 661     ///
 662     /// This is currently unstable.
 663     pub suggestion: Option<Symbol>,
 664
 665     /// Whether to treat the since attribute as being a Rust version identifier
 666     /// (rather than an opaque string).
 667     pub is_since_rustc_version: bool,
 668 }
 669
 670 /// Finds the deprecation attribute. `None` if none exists.
 671 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 672     find_deprecation_generic(sess, attrs.iter())
 673 }
 674
 675 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 676 where
 677     I: Iterator<Item = &'a Attribute>,
 678 {
 679     let mut depr: Option<(Deprecation, Span)> = None;
 680     let diagnostic = &sess.parse_sess.span_diagnostic;
 681
 682     'outer: for attr in attrs_iter {
 683         if !(sess.check_name(attr, sym::deprecated) || sess.check_name(attr, sym::rustc_deprecated))
 684         {
 685             continue;
 686         }
 687
 688         if let Some((_, span)) = &depr {
 689             struct_span_err!(diagnostic, attr.span, E0550, "multiple deprecated attributes")
 690                 .span_label(attr.span, "repeated deprecation attribute")
 691                 .span_label(*span, "first deprecation attribute")
 692                 .emit();
 693             break;
 694         }
 695
 696         let meta = match attr.meta() {
 697             Some(meta) => meta,
 698             None => continue,
 699         };
 700         let mut since = None;
 701         let mut note = None;
 702         let mut suggestion = None;
 703         match &meta.kind {
 704             MetaItemKind::Word => {}
 705             MetaItemKind::NameValue(..) => note = meta.value_str(),
 706             MetaItemKind::List(list) => {
 707                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 708                     if item.is_some() {
 709                         handle_errors(
 710                             &sess.parse_sess,
 711                             meta.span,
 712                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 713                         );
 714                         return false;
 715                     }
 716                     if let Some(v) = meta.value_str() {
 717                         *item = Some(v);
 718                         true
 719                     } else {
 720                         if let Some(lit) = meta.name_value_literal() {
 721                             handle_errors(
 722                                 &sess.parse_sess,
 723                                 lit.span,
 724                                 AttrError::UnsupportedLiteral(
 725                                     "literal in `deprecated` \
 726                                     value must be a string",
 727                                     lit.kind.is_bytestr(),
 728                                 ),
 729                             );
 730                         } else {
 731                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 732                                 .emit();
 733                         }
 734
 735                         false
 736                     }
 737                 };
 738
 739                 for meta in list {
 740                     match meta {
 741                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 742                             sym::since => {
 743                                 if !get(mi, &mut since) {
 744                                     continue 'outer;
 745                                 }
 746                             }
 747                             sym::note if sess.check_name(attr, sym::deprecated) => {
 748                                 if !get(mi, &mut note) {
 749                                     continue 'outer;
 750                                 }
 751                             }
 752                             sym::reason if sess.check_name(attr, sym::rustc_deprecated) => {
 753                                 if !get(mi, &mut note) {
 754                                     continue 'outer;
 755                                 }
 756                             }
 757                             sym::suggestion if sess.check_name(attr, sym::rustc_deprecated) => {
 758                                 if !get(mi, &mut suggestion) {
 759                                     continue 'outer;
 760                                 }
 761                             }
 762                             _ => {
 763                                 handle_errors(
 764                                     &sess.parse_sess,
 765                                     meta.span(),
 766                                     AttrError::UnknownMetaItem(
 767                                         pprust::path_to_string(&mi.path),
 768                                         if sess.check_name(attr, sym::deprecated) {
 769                                             &["since", "note"]
 770                                         } else {
 771                                             &["since", "reason", "suggestion"]
 772                                         },
 773                                     ),
 774                                 );
 775                                 continue 'outer;
 776                             }
 777                         },
 778                         NestedMetaItem::Literal(lit) => {
 779                             handle_errors(
 780                                 &sess.parse_sess,
 781                                 lit.span,
 782                                 AttrError::UnsupportedLiteral(
 783                                     "item in `deprecated` must be a key/value pair",
 784                                     false,
 785                                 ),
 786                             );
 787                             continue 'outer;
 788                         }
 789                     }
 790                 }
 791             }
 792         }
 793
 794         if suggestion.is_some() && sess.check_name(attr, sym::deprecated) {
 795             unreachable!("only allowed on rustc_deprecated")
 796         }
 797
 798         if sess.check_name(attr, sym::rustc_deprecated) {
 799             if since.is_none() {
 800                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 801                 continue;
 802             }
 803
 804             if note.is_none() {
 805                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'").emit();
 806                 continue;
 807             }
 808         }
 809
 810         sess.mark_attr_used(&attr);
 811
 812         let is_since_rustc_version = sess.check_name(attr, sym::rustc_deprecated);
 813         depr = Some((Deprecation { since, note, suggestion, is_since_rustc_version }, attr.span));
 814     }
 815
 816     depr
 817 }
 818
 819 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 820 pub enum ReprAttr {
 821     ReprInt(IntType),
 822     ReprC,
 823     ReprPacked(u32),
 824     ReprSimd,
 825     ReprTransparent,
 826     ReprAlign(u32),
 827     ReprNoNiche,
 828 }
 829
 830 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 831 #[derive(Encodable, Decodable, HashStable_Generic)]
 832 pub enum IntType {
 833     SignedInt(ast::IntTy),
 834     UnsignedInt(ast::UintTy),
 835 }
 836
 837 impl IntType {
 838     #[inline]
 839     pub fn is_signed(self) -> bool {
 840         use IntType::*;
 841
 842         match self {
 843             SignedInt(..) => true,
 844             UnsignedInt(..) => false,
 845         }
 846     }
 847 }
 848
 849 /// Parse #[repr(...)] forms.
 850 ///
 851 /// Valid repr contents: any of the primitive integral type names (see
 852 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 853 /// the same discriminant size that the corresponding C enum would or C
 854 /// structure layout, `packed` to remove padding, and `transparent` to elegate representation
 855 /// concerns to the only non-ZST field.
 856 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 857     use ReprAttr::*;
 858
 859     let mut acc = Vec::new();
 860     let diagnostic = &sess.parse_sess.span_diagnostic;
 861     if attr.has_name(sym::repr) {
 862         if let Some(items) = attr.meta_item_list() {
 863             sess.mark_attr_used(attr);
 864             for item in items {
 865                 if !item.is_meta_item() {
 866                     handle_errors(
 867                         &sess.parse_sess,
 868                         item.span(),
 869                         AttrError::UnsupportedLiteral(
 870                             "meta item in `repr` must be an identifier",
 871                             false,
 872                         ),
 873                     );
 874                     continue;
 875                 }
 876
 877                 let mut recognised = false;
 878                 if item.is_word() {
 879                     let hint = match item.name_or_empty() {
 880                         sym::C => Some(ReprC),
 881                         sym::packed => Some(ReprPacked(1)),
 882                         sym::simd => Some(ReprSimd),
 883                         sym::transparent => Some(ReprTransparent),
 884                         sym::no_niche => Some(ReprNoNiche),
 885                         name => int_type_of_word(name).map(ReprInt),
 886                     };
 887
 888                     if let Some(h) = hint {
 889                         recognised = true;
 890                         acc.push(h);
 891                     }
 892                 } else if let Some((name, value)) = item.name_value_literal() {
 893                     let parse_alignment = |node: &ast::LitKind| -> Result<u32, &'static str> {
 894                         if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
 895                             if literal.is_power_of_two() {
 896                                 // rustc_middle::ty::layout::Align restricts align to <= 2^29
 897                                 if *literal <= 1 << 29 {
 898                                     Ok(*literal as u32)
 899                                 } else {
 900                                     Err("larger than 2^29")
 901                                 }
 902                             } else {
 903                                 Err("not a power of two")
 904                             }
 905                         } else {
 906                             Err("not an unsuffixed integer")
 907                         }
 908                     };
 909
 910                     let mut literal_error = None;
 911                     if name == sym::align {
 912                         recognised = true;
 913                         match parse_alignment(&value.kind) {
 914                             Ok(literal) => acc.push(ReprAlign(literal)),
 915                             Err(message) => literal_error = Some(message),
 916                         };
 917                     } else if name == sym::packed {
 918                         recognised = true;
 919                         match parse_alignment(&value.kind) {
 920                             Ok(literal) => acc.push(ReprPacked(literal)),
 921                             Err(message) => literal_error = Some(message),
 922                         };
 923                     }
 924                     if let Some(literal_error) = literal_error {
 925                         struct_span_err!(
 926                             diagnostic,
 927                             item.span(),
 928                             E0589,
 929                             "invalid `repr(align)` attribute: {}",
 930                             literal_error
 931                         )
 932                         .emit();
 933                     }
 934                 } else if let Some(meta_item) = item.meta_item() {
 935                     if meta_item.has_name(sym::align) {
 936                         if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 937                             recognised = true;
 938                             let mut err = struct_span_err!(
 939                                 diagnostic,
 940                                 item.span(),
 941                                 E0693,
 942                                 "incorrect `repr(align)` attribute format"
 943                             );
 944                             match value.kind {
 945                                 ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 946                                     err.span_suggestion(
 947                                         item.span(),
 948                                         "use parentheses instead",
 949                                         format!("align({})", int),
 950                                         Applicability::MachineApplicable,
 951                                     );
 952                                 }
 953                                 ast::LitKind::Str(s, _) => {
 954                                     err.span_suggestion(
 955                                         item.span(),
 956                                         "use parentheses instead",
 957                                         format!("align({})", s),
 958                                         Applicability::MachineApplicable,
 959                                     );
 960                                 }
 961                                 _ => {}
 962                             }
 963                             err.emit();
 964                         }
 965                     }
 966                 }
 967                 if !recognised {
 968                     // Not a word we recognize
 969                     struct_span_err!(
 970                         diagnostic,
 971                         item.span(),
 972                         E0552,
 973                         "unrecognized representation hint"
 974                     )
 975                     .emit();
 976                 }
 977             }
 978         }
 979     }
 980     acc
 981 }
 982
 983 fn int_type_of_word(s: Symbol) -> Option<IntType> {
 984     use IntType::*;
 985
 986     match s {
 987         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
 988         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
 989         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
 990         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
 991         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
 992         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
 993         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
 994         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
 995         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
 996         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
 997         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
 998         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
 999         _ => None,
1000     }
1001 }
1002
1003 pub enum TransparencyError {
1004     UnknownTransparency(Symbol, Span),
1005     MultipleTransparencyAttrs(Span, Span),
1006 }
1007
1008 pub fn find_transparency(
1009     sess: &Session,
1010     attrs: &[Attribute],
1011     macro_rules: bool,
1012 ) -> (Transparency, Option<TransparencyError>) {
1013     let mut transparency = None;
1014     let mut error = None;
1015     for attr in attrs {
1016         if sess.check_name(attr, sym::rustc_macro_transparency) {
1017             if let Some((_, old_span)) = transparency {
1018                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1019                 break;
1020             } else if let Some(value) = attr.value_str() {
1021                 transparency = Some((
1022                     match value {
1023                         sym::transparent => Transparency::Transparent,
1024                         sym::semitransparent => Transparency::SemiTransparent,
1025                         sym::opaque => Transparency::Opaque,
1026                         _ => {
1027                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1028                             continue;
1029                         }
1030                     },
1031                     attr.span,
1032                 ));
1033             }
1034         }
1035     }
1036     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1037     (transparency.map_or(fallback, |t| t.0), error)
1038 }
1039
1040 pub fn allow_internal_unstable<'a>(
1041     sess: &'a Session,
1042     attrs: &'a [Attribute],
1043 ) -> impl Iterator<Item = Symbol> + 'a {
1044     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1045 }
1046
1047 pub fn rustc_allow_const_fn_unstable<'a>(
1048     sess: &'a Session,
1049     attrs: &'a [Attribute],
1050 ) -> impl Iterator<Item = Symbol> + 'a {
1051     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1052 }
1053
1054 fn allow_unstable<'a>(
1055     sess: &'a Session,
1056     attrs: &'a [Attribute],
1057     symbol: Symbol,
1058 ) -> impl Iterator<Item = Symbol> + 'a {
1059     let attrs = sess.filter_by_name(attrs, symbol);
1060     let list = attrs
1061         .filter_map(move |attr| {
1062             attr.meta_item_list().or_else(|| {
1063                 sess.diagnostic().span_err(
1064                     attr.span,
1065                     &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
1066                 );
1067                 None
1068             })
1069         })
1070         .flatten();
1071
1072     list.into_iter().filter_map(move |it| {
1073         let name = it.ident().map(|ident| ident.name);
1074         if name.is_none() {
1075             sess.diagnostic().span_err(
1076                 it.span(),
1077                 &format!("`{}` expects feature names", symbol.to_ident_string()),
1078             );
1079         }
1080         name
1081     })
1082 }