compiler/rustc_attr/src/builtin.rs

   1 //! Parsing and validation of builtin attributes
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::{Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem, NodeId};
   5 use rustc_ast_pretty::pprust;
   6 use rustc_errors::{struct_span_err, Applicability};
   7 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
   8 use rustc_macros::HashStable_Generic;
   9 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
  10 use rustc_session::lint::BuiltinLintDiagnostics;
  11 use rustc_session::parse::{feature_err, ParseSess};
  12 use rustc_session::Session;
  13 use rustc_span::hygiene::Transparency;
  14 use rustc_span::{symbol::sym, symbol::Symbol, Span};
  15 use std::num::NonZeroU32;
  16
  17 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  18     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  19 }
  20
  21 enum AttrError {
  22     MultipleItem(String),
  23     UnknownMetaItem(String, &'static [&'static str]),
  24     MissingSince,
  25     NonIdentFeature,
  26     MissingFeature,
  27     MultipleStabilityLevels,
  28     UnsupportedLiteral(&'static str, /* is_bytestr */ bool),
  29 }
  30
  31 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
  32     let diag = &sess.span_diagnostic;
  33     match error {
  34         AttrError::MultipleItem(item) => {
  35             struct_span_err!(diag, span, E0538, "multiple '{}' items", item).emit();
  36         }
  37         AttrError::UnknownMetaItem(item, expected) => {
  38             let expected = expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
  39             struct_span_err!(diag, span, E0541, "unknown meta item '{}'", item)
  40                 .span_label(span, format!("expected one of {}", expected.join(", ")))
  41                 .emit();
  42         }
  43         AttrError::MissingSince => {
  44             struct_span_err!(diag, span, E0542, "missing 'since'").emit();
  45         }
  46         AttrError::NonIdentFeature => {
  47             struct_span_err!(diag, span, E0546, "'feature' is not an identifier").emit();
  48         }
  49         AttrError::MissingFeature => {
  50             struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
  51         }
  52         AttrError::MultipleStabilityLevels => {
  53             struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
  54         }
  55         AttrError::UnsupportedLiteral(msg, is_bytestr) => {
  56             let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
  57             if is_bytestr {
  58                 if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
  59                     err.span_suggestion(
  60                         span,
  61                         "consider removing the prefix",
  62                         lint_str[1..].to_string(),
  63                         Applicability::MaybeIncorrect,
  64                     );
  65                 }
  66             }
  67             err.emit();
  68         }
  69     }
  70 }
  71
  72 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
  73 pub enum InlineAttr {
  74     None,
  75     Hint,
  76     Always,
  77     Never,
  78 }
  79
  80 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
  81 pub enum InstructionSetAttr {
  82     ArmA32,
  83     ArmT32,
  84 }
  85
  86 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
  87 pub enum OptimizeAttr {
  88     None,
  89     Speed,
  90     Size,
  91 }
  92
  93 /// Represents the following attributes:
  94 ///
  95 /// - `#[stable]`
  96 /// - `#[unstable]`
  97 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
  98 #[derive(HashStable_Generic)]
  99 pub struct Stability {
 100     pub level: StabilityLevel,
 101     pub feature: Symbol,
 102 }
 103
 104 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 105 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 106 #[derive(HashStable_Generic)]
 107 pub struct ConstStability {
 108     pub level: StabilityLevel,
 109     pub feature: Symbol,
 110     /// whether the function has a `#[rustc_promotable]` attribute
 111     pub promotable: bool,
 112 }
 113
 114 /// The available stability levels.
 115 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 116 #[derive(HashStable_Generic)]
 117 pub enum StabilityLevel {
 118     // Reason for the current stability level and the relevant rust-lang issue
 119     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 120     Stable { since: Symbol },
 121 }
 122
 123 impl StabilityLevel {
 124     pub fn is_unstable(&self) -> bool {
 125         matches!(self, StabilityLevel::Unstable { .. })
 126     }
 127     pub fn is_stable(&self) -> bool {
 128         matches!(self, StabilityLevel::Stable { .. })
 129     }
 130 }
 131
 132 /// Collects stability info from all stability attributes in `attrs`.
 133 /// Returns `None` if no stability attributes are found.
 134 pub fn find_stability(
 135     sess: &Session,
 136     attrs: &[Attribute],
 137     item_sp: Span,
 138 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
 139     find_stability_generic(sess, attrs.iter(), item_sp)
 140 }
 141
 142 fn find_stability_generic<'a, I>(
 143     sess: &Session,
 144     attrs_iter: I,
 145     item_sp: Span,
 146 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
 147 where
 148     I: Iterator<Item = &'a Attribute>,
 149 {
 150     use StabilityLevel::*;
 151
 152     let mut stab: Option<(Stability, Span)> = None;
 153     let mut const_stab: Option<(ConstStability, Span)> = None;
 154     let mut promotable = false;
 155
 156     let diagnostic = &sess.parse_sess.span_diagnostic;
 157
 158     'outer: for attr in attrs_iter {
 159         if ![
 160             sym::rustc_const_unstable,
 161             sym::rustc_const_stable,
 162             sym::unstable,
 163             sym::stable,
 164             sym::rustc_promotable,
 165         ]
 166         .iter()
 167         .any(|&s| attr.has_name(s))
 168         {
 169             continue; // not a stability level
 170         }
 171
 172         let meta = attr.meta();
 173
 174         if attr.has_name(sym::rustc_promotable) {
 175             promotable = true;
 176         }
 177         // attributes with data
 178         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 179             let meta = meta.as_ref().unwrap();
 180             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 181                 if item.is_some() {
 182                     handle_errors(
 183                         &sess.parse_sess,
 184                         meta.span,
 185                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 186                     );
 187                     return false;
 188                 }
 189                 if let Some(v) = meta.value_str() {
 190                     *item = Some(v);
 191                     true
 192                 } else {
 193                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 194                     false
 195                 }
 196             };
 197
 198             let meta_name = meta.name_or_empty();
 199             match meta_name {
 200                 sym::rustc_const_unstable | sym::unstable => {
 201                     if meta_name == sym::unstable && stab.is_some() {
 202                         handle_errors(
 203                             &sess.parse_sess,
 204                             attr.span,
 205                             AttrError::MultipleStabilityLevels,
 206                         );
 207                         break;
 208                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 209                         handle_errors(
 210                             &sess.parse_sess,
 211                             attr.span,
 212                             AttrError::MultipleStabilityLevels,
 213                         );
 214                         break;
 215                     }
 216
 217                     let mut feature = None;
 218                     let mut reason = None;
 219                     let mut issue = None;
 220                     let mut issue_num = None;
 221                     let mut is_soft = false;
 222                     for meta in metas {
 223                         let Some(mi) = meta.meta_item() else {
 224                             handle_errors(
 225                                 &sess.parse_sess,
 226                                 meta.span(),
 227                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 228                             );
 229                             continue 'outer;
 230                         };
 231                         match mi.name_or_empty() {
 232                             sym::feature => {
 233                                 if !get(mi, &mut feature) {
 234                                     continue 'outer;
 235                                 }
 236                             }
 237                             sym::reason => {
 238                                 if !get(mi, &mut reason) {
 239                                     continue 'outer;
 240                                 }
 241                             }
 242                             sym::issue => {
 243                                 if !get(mi, &mut issue) {
 244                                     continue 'outer;
 245                                 }
 246
 247                                 // These unwraps are safe because `get` ensures the meta item
 248                                 // is a name/value pair string literal.
 249                                 issue_num = match issue.unwrap().as_str() {
 250                                     "none" => None,
 251                                     issue => {
 252                                         let emit_diag = |msg: &str| {
 253                                             struct_span_err!(
 254                                                 diagnostic,
 255                                                 mi.span,
 256                                                 E0545,
 257                                                 "`issue` must be a non-zero numeric string \
 258                                                 or \"none\"",
 259                                             )
 260                                             .span_label(mi.name_value_literal_span().unwrap(), msg)
 261                                             .emit();
 262                                         };
 263                                         match issue.parse() {
 264                                             Ok(0) => {
 265                                                 emit_diag(
 266                                                     "`issue` must not be \"0\", \
 267                                                     use \"none\" instead",
 268                                                 );
 269                                                 continue 'outer;
 270                                             }
 271                                             Ok(num) => NonZeroU32::new(num),
 272                                             Err(err) => {
 273                                                 emit_diag(&err.to_string());
 274                                                 continue 'outer;
 275                                             }
 276                                         }
 277                                     }
 278                                 };
 279                             }
 280                             sym::soft => {
 281                                 if !mi.is_word() {
 282                                     let msg = "`soft` should not have any arguments";
 283                                     sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 284                                 }
 285                                 is_soft = true;
 286                             }
 287                             _ => {
 288                                 handle_errors(
 289                                     &sess.parse_sess,
 290                                     meta.span(),
 291                                     AttrError::UnknownMetaItem(
 292                                         pprust::path_to_string(&mi.path),
 293                                         &["feature", "reason", "issue", "soft"],
 294                                     ),
 295                                 );
 296                                 continue 'outer;
 297                             }
 298                         }
 299                     }
 300
 301                     match (feature, reason, issue) {
 302                         (Some(feature), reason, Some(_)) => {
 303                             if !rustc_lexer::is_ident(feature.as_str()) {
 304                                 handle_errors(
 305                                     &sess.parse_sess,
 306                                     attr.span,
 307                                     AttrError::NonIdentFeature,
 308                                 );
 309                                 continue;
 310                             }
 311                             let level = Unstable { reason, issue: issue_num, is_soft };
 312                             if sym::unstable == meta_name {
 313                                 stab = Some((Stability { level, feature }, attr.span));
 314                             } else {
 315                                 const_stab = Some((
 316                                     ConstStability { level, feature, promotable: false },
 317                                     attr.span,
 318                                 ));
 319                             }
 320                         }
 321                         (None, _, _) => {
 322                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 323                             continue;
 324                         }
 325                         _ => {
 326                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 327                                 .emit();
 328                             continue;
 329                         }
 330                     }
 331                 }
 332                 sym::rustc_const_stable | sym::stable => {
 333                     if meta_name == sym::stable && stab.is_some() {
 334                         handle_errors(
 335                             &sess.parse_sess,
 336                             attr.span,
 337                             AttrError::MultipleStabilityLevels,
 338                         );
 339                         break;
 340                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 341                         handle_errors(
 342                             &sess.parse_sess,
 343                             attr.span,
 344                             AttrError::MultipleStabilityLevels,
 345                         );
 346                         break;
 347                     }
 348
 349                     let mut feature = None;
 350                     let mut since = None;
 351                     for meta in metas {
 352                         match meta {
 353                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 354                                 sym::feature => {
 355                                     if !get(mi, &mut feature) {
 356                                         continue 'outer;
 357                                     }
 358                                 }
 359                                 sym::since => {
 360                                     if !get(mi, &mut since) {
 361                                         continue 'outer;
 362                                     }
 363                                 }
 364                                 _ => {
 365                                     handle_errors(
 366                                         &sess.parse_sess,
 367                                         meta.span(),
 368                                         AttrError::UnknownMetaItem(
 369                                             pprust::path_to_string(&mi.path),
 370                                             &["since", "note"],
 371                                         ),
 372                                     );
 373                                     continue 'outer;
 374                                 }
 375                             },
 376                             NestedMetaItem::Literal(lit) => {
 377                                 handle_errors(
 378                                     &sess.parse_sess,
 379                                     lit.span,
 380                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 381                                 );
 382                                 continue 'outer;
 383                             }
 384                         }
 385                     }
 386
 387                     match (feature, since) {
 388                         (Some(feature), Some(since)) => {
 389                             let level = Stable { since };
 390                             if sym::stable == meta_name {
 391                                 stab = Some((Stability { level, feature }, attr.span));
 392                             } else {
 393                                 const_stab = Some((
 394                                     ConstStability { level, feature, promotable: false },
 395                                     attr.span,
 396                                 ));
 397                             }
 398                         }
 399                         (None, _) => {
 400                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 401                             continue;
 402                         }
 403                         _ => {
 404                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 405                             continue;
 406                         }
 407                     }
 408                 }
 409                 _ => unreachable!(),
 410             }
 411         }
 412     }
 413
 414     // Merge the const-unstable info into the stability info
 415     if promotable {
 416         if let Some((ref mut stab, _)) = const_stab {
 417             stab.promotable = promotable;
 418         } else {
 419             struct_span_err!(
 420                 diagnostic,
 421                 item_sp,
 422                 E0717,
 423                 "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
 424                 or a `rustc_const_stable` attribute"
 425             )
 426             .emit();
 427         }
 428     }
 429
 430     (stab, const_stab)
 431 }
 432
 433 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 434     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 435 }
 436
 437 /// Tests if a cfg-pattern matches the cfg set
 438 pub fn cfg_matches(
 439     cfg: &ast::MetaItem,
 440     sess: &ParseSess,
 441     lint_node_id: NodeId,
 442     features: Option<&Features>,
 443 ) -> bool {
 444     eval_condition(cfg, sess, features, &mut |cfg| {
 445         try_gate_cfg(cfg, sess, features);
 446         let error = |span, msg| {
 447             sess.span_diagnostic.span_err(span, msg);
 448             true
 449         };
 450         if cfg.path.segments.len() != 1 {
 451             return error(cfg.path.span, "`cfg` predicate key must be an identifier");
 452         }
 453         match &cfg.kind {
 454             MetaItemKind::List(..) => {
 455                 error(cfg.span, "unexpected parentheses after `cfg` predicate key")
 456             }
 457             MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 458                 handle_errors(
 459                     sess,
 460                     lit.span,
 461                     AttrError::UnsupportedLiteral(
 462                         "literal in `cfg` predicate value must be a string",
 463                         lit.kind.is_bytestr(),
 464                     ),
 465                 );
 466                 true
 467             }
 468             MetaItemKind::NameValue(..) | MetaItemKind::Word => {
 469                 let ident = cfg.ident().expect("multi-segment cfg predicate");
 470                 let name = ident.name;
 471                 let value = cfg.value_str();
 472                 if let Some(names_valid) = &sess.check_config.names_valid {
 473                     if !names_valid.contains(&name) {
 474                         sess.buffer_lint_with_diagnostic(
 475                             UNEXPECTED_CFGS,
 476                             cfg.span,
 477                             lint_node_id,
 478                             "unexpected `cfg` condition name",
 479                             BuiltinLintDiagnostics::UnexpectedCfg((name, ident.span), None),
 480                         );
 481                     }
 482                 }
 483                 if let Some(value) = value {
 484                     if let Some(values) = &sess.check_config.values_valid.get(&name) {
 485                         if !values.contains(&value) {
 486                             sess.buffer_lint_with_diagnostic(
 487                                 UNEXPECTED_CFGS,
 488                                 cfg.span,
 489                                 lint_node_id,
 490                                 "unexpected `cfg` condition value",
 491                                 BuiltinLintDiagnostics::UnexpectedCfg(
 492                                     (name, ident.span),
 493                                     Some((value, cfg.name_value_literal_span().unwrap())),
 494                                 ),
 495                             );
 496                         }
 497                     }
 498                 }
 499                 sess.config.contains(&(name, value))
 500             }
 501         }
 502     })
 503 }
 504
 505 fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
 506     let gate = find_gated_cfg(|sym| cfg.has_name(sym));
 507     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 508         gate_cfg(&gated_cfg, cfg.span, sess, feats);
 509     }
 510 }
 511
 512 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 513     let (cfg, feature, has_feature) = gated_cfg;
 514     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 515         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 516         feature_err(sess, *feature, cfg_span, &explain).emit();
 517     }
 518 }
 519
 520 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 521 struct Version {
 522     major: u16,
 523     minor: u16,
 524     patch: u16,
 525 }
 526
 527 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 528     let mut components = s.split('-');
 529     let d = components.next()?;
 530     if !allow_appendix && components.next().is_some() {
 531         return None;
 532     }
 533     let mut digits = d.splitn(3, '.');
 534     let major = digits.next()?.parse().ok()?;
 535     let minor = digits.next()?.parse().ok()?;
 536     let patch = digits.next().unwrap_or("0").parse().ok()?;
 537     Some(Version { major, minor, patch })
 538 }
 539
 540 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 541 /// evaluate individual items.
 542 pub fn eval_condition(
 543     cfg: &ast::MetaItem,
 544     sess: &ParseSess,
 545     features: Option<&Features>,
 546     eval: &mut impl FnMut(&ast::MetaItem) -> bool,
 547 ) -> bool {
 548     match cfg.kind {
 549         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 550             try_gate_cfg(cfg, sess, features);
 551             let (min_version, span) = match &mis[..] {
 552                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 553                     (sym, span)
 554                 }
 555                 [
 556                     NestedMetaItem::Literal(Lit { span, .. })
 557                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 558                 ] => {
 559                     sess.span_diagnostic
 560                         .struct_span_err(*span, "expected a version literal")
 561                         .emit();
 562                     return false;
 563                 }
 564                 [..] => {
 565                     sess.span_diagnostic
 566                         .struct_span_err(cfg.span, "expected single version literal")
 567                         .emit();
 568                     return false;
 569                 }
 570             };
 571             let Some(min_version) = parse_version(min_version.as_str(), false) else {
 572                 sess.span_diagnostic
 573                     .struct_span_warn(
 574                         *span,
 575                         "unknown version literal format, assuming it refers to a future version",
 576                     )
 577                     .emit();
 578                 return false;
 579             };
 580             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 581
 582             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 583             if sess.assume_incomplete_release {
 584                 rustc_version > min_version
 585             } else {
 586                 rustc_version >= min_version
 587             }
 588         }
 589         ast::MetaItemKind::List(ref mis) => {
 590             for mi in mis.iter() {
 591                 if !mi.is_meta_item() {
 592                     handle_errors(
 593                         sess,
 594                         mi.span(),
 595                         AttrError::UnsupportedLiteral("unsupported literal", false),
 596                     );
 597                     return false;
 598                 }
 599             }
 600
 601             // The unwraps below may look dangerous, but we've already asserted
 602             // that they won't fail with the loop above.
 603             match cfg.name_or_empty() {
 604                 sym::any => mis
 605                     .iter()
 606                     .any(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 607                 sym::all => mis
 608                     .iter()
 609                     .all(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 610                 sym::not => {
 611                     if mis.len() != 1 {
 612                         struct_span_err!(
 613                             sess.span_diagnostic,
 614                             cfg.span,
 615                             E0536,
 616                             "expected 1 cfg-pattern"
 617                         )
 618                         .emit();
 619                         return false;
 620                     }
 621
 622                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 623                 }
 624                 _ => {
 625                     struct_span_err!(
 626                         sess.span_diagnostic,
 627                         cfg.span,
 628                         E0537,
 629                         "invalid predicate `{}`",
 630                         pprust::path_to_string(&cfg.path)
 631                     )
 632                     .emit();
 633                     false
 634                 }
 635             }
 636         }
 637         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => eval(cfg),
 638     }
 639 }
 640
 641 #[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 642 pub struct Deprecation {
 643     pub since: Option<Symbol>,
 644     /// The note to issue a reason.
 645     pub note: Option<Symbol>,
 646     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 647     ///
 648     /// This is currently unstable.
 649     pub suggestion: Option<Symbol>,
 650
 651     /// Whether to treat the since attribute as being a Rust version identifier
 652     /// (rather than an opaque string).
 653     pub is_since_rustc_version: bool,
 654 }
 655
 656 /// Finds the deprecation attribute. `None` if none exists.
 657 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 658     find_deprecation_generic(sess, attrs.iter())
 659 }
 660
 661 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 662 where
 663     I: Iterator<Item = &'a Attribute>,
 664 {
 665     let mut depr: Option<(Deprecation, Span)> = None;
 666     let diagnostic = &sess.parse_sess.span_diagnostic;
 667
 668     'outer: for attr in attrs_iter {
 669         if !(attr.has_name(sym::deprecated) || attr.has_name(sym::rustc_deprecated)) {
 670             continue;
 671         }
 672
 673         if let Some((_, span)) = &depr {
 674             struct_span_err!(diagnostic, attr.span, E0550, "multiple deprecated attributes")
 675                 .span_label(attr.span, "repeated deprecation attribute")
 676                 .span_label(*span, "first deprecation attribute")
 677                 .emit();
 678             break;
 679         }
 680
 681         let Some(meta) = attr.meta() else {
 682             continue;
 683         };
 684         let mut since = None;
 685         let mut note = None;
 686         let mut suggestion = None;
 687         match &meta.kind {
 688             MetaItemKind::Word => {}
 689             MetaItemKind::NameValue(..) => note = meta.value_str(),
 690             MetaItemKind::List(list) => {
 691                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 692                     if item.is_some() {
 693                         handle_errors(
 694                             &sess.parse_sess,
 695                             meta.span,
 696                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 697                         );
 698                         return false;
 699                     }
 700                     if let Some(v) = meta.value_str() {
 701                         *item = Some(v);
 702                         true
 703                     } else {
 704                         if let Some(lit) = meta.name_value_literal() {
 705                             handle_errors(
 706                                 &sess.parse_sess,
 707                                 lit.span,
 708                                 AttrError::UnsupportedLiteral(
 709                                     "literal in `deprecated` \
 710                                     value must be a string",
 711                                     lit.kind.is_bytestr(),
 712                                 ),
 713                             );
 714                         } else {
 715                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 716                                 .emit();
 717                         }
 718
 719                         false
 720                     }
 721                 };
 722
 723                 for meta in list {
 724                     match meta {
 725                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 726                             sym::since => {
 727                                 if !get(mi, &mut since) {
 728                                     continue 'outer;
 729                                 }
 730                             }
 731                             sym::note if attr.has_name(sym::deprecated) => {
 732                                 if !get(mi, &mut note) {
 733                                     continue 'outer;
 734                                 }
 735                             }
 736                             sym::reason if attr.has_name(sym::rustc_deprecated) => {
 737                                 if !get(mi, &mut note) {
 738                                     continue 'outer;
 739                                 }
 740                             }
 741                             sym::suggestion if attr.has_name(sym::rustc_deprecated) => {
 742                                 if !get(mi, &mut suggestion) {
 743                                     continue 'outer;
 744                                 }
 745                             }
 746                             _ => {
 747                                 handle_errors(
 748                                     &sess.parse_sess,
 749                                     meta.span(),
 750                                     AttrError::UnknownMetaItem(
 751                                         pprust::path_to_string(&mi.path),
 752                                         if attr.has_name(sym::deprecated) {
 753                                             &["since", "note"]
 754                                         } else {
 755                                             &["since", "reason", "suggestion"]
 756                                         },
 757                                     ),
 758                                 );
 759                                 continue 'outer;
 760                             }
 761                         },
 762                         NestedMetaItem::Literal(lit) => {
 763                             handle_errors(
 764                                 &sess.parse_sess,
 765                                 lit.span,
 766                                 AttrError::UnsupportedLiteral(
 767                                     "item in `deprecated` must be a key/value pair",
 768                                     false,
 769                                 ),
 770                             );
 771                             continue 'outer;
 772                         }
 773                     }
 774                 }
 775             }
 776         }
 777
 778         if suggestion.is_some() && attr.has_name(sym::deprecated) {
 779             unreachable!("only allowed on rustc_deprecated")
 780         }
 781
 782         if attr.has_name(sym::rustc_deprecated) {
 783             if since.is_none() {
 784                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 785                 continue;
 786             }
 787
 788             if note.is_none() {
 789                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'").emit();
 790                 continue;
 791             }
 792         }
 793
 794         let is_since_rustc_version = attr.has_name(sym::rustc_deprecated);
 795         depr = Some((Deprecation { since, note, suggestion, is_since_rustc_version }, attr.span));
 796     }
 797
 798     depr
 799 }
 800
 801 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 802 pub enum ReprAttr {
 803     ReprInt(IntType),
 804     ReprC,
 805     ReprPacked(u32),
 806     ReprSimd,
 807     ReprTransparent,
 808     ReprAlign(u32),
 809     ReprNoNiche,
 810 }
 811
 812 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 813 #[derive(Encodable, Decodable, HashStable_Generic)]
 814 pub enum IntType {
 815     SignedInt(ast::IntTy),
 816     UnsignedInt(ast::UintTy),
 817 }
 818
 819 impl IntType {
 820     #[inline]
 821     pub fn is_signed(self) -> bool {
 822         use IntType::*;
 823
 824         match self {
 825             SignedInt(..) => true,
 826             UnsignedInt(..) => false,
 827         }
 828     }
 829 }
 830
 831 /// Parse #[repr(...)] forms.
 832 ///
 833 /// Valid repr contents: any of the primitive integral type names (see
 834 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 835 /// the same discriminant size that the corresponding C enum would or C
 836 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 837 /// concerns to the only non-ZST field.
 838 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 839     use ReprAttr::*;
 840
 841     let mut acc = Vec::new();
 842     let diagnostic = &sess.parse_sess.span_diagnostic;
 843     if attr.has_name(sym::repr) {
 844         if let Some(items) = attr.meta_item_list() {
 845             for item in items {
 846                 let mut recognised = false;
 847                 if item.is_word() {
 848                     let hint = match item.name_or_empty() {
 849                         sym::C => Some(ReprC),
 850                         sym::packed => Some(ReprPacked(1)),
 851                         sym::simd => Some(ReprSimd),
 852                         sym::transparent => Some(ReprTransparent),
 853                         sym::no_niche => Some(ReprNoNiche),
 854                         sym::align => {
 855                             let mut err = struct_span_err!(
 856                                 diagnostic,
 857                                 item.span(),
 858                                 E0589,
 859                                 "invalid `repr(align)` attribute: `align` needs an argument"
 860                             );
 861                             err.span_suggestion(
 862                                 item.span(),
 863                                 "supply an argument here",
 864                                 "align(...)".to_string(),
 865                                 Applicability::HasPlaceholders,
 866                             );
 867                             err.emit();
 868                             recognised = true;
 869                             None
 870                         }
 871                         name => int_type_of_word(name).map(ReprInt),
 872                     };
 873
 874                     if let Some(h) = hint {
 875                         recognised = true;
 876                         acc.push(h);
 877                     }
 878                 } else if let Some((name, value)) = item.name_value_literal() {
 879                     let mut literal_error = None;
 880                     if name == sym::align {
 881                         recognised = true;
 882                         match parse_alignment(&value.kind) {
 883                             Ok(literal) => acc.push(ReprAlign(literal)),
 884                             Err(message) => literal_error = Some(message),
 885                         };
 886                     } else if name == sym::packed {
 887                         recognised = true;
 888                         match parse_alignment(&value.kind) {
 889                             Ok(literal) => acc.push(ReprPacked(literal)),
 890                             Err(message) => literal_error = Some(message),
 891                         };
 892                     } else if matches!(name, sym::C | sym::simd | sym::transparent | sym::no_niche)
 893                         || int_type_of_word(name).is_some()
 894                     {
 895                         recognised = true;
 896                         struct_span_err!(
 897                                 diagnostic,
 898                                 item.span(),
 899                                 E0552,
 900                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
 901                                 name.to_ident_string(),
 902                             ).emit();
 903                     }
 904                     if let Some(literal_error) = literal_error {
 905                         struct_span_err!(
 906                             diagnostic,
 907                             item.span(),
 908                             E0589,
 909                             "invalid `repr({})` attribute: {}",
 910                             name.to_ident_string(),
 911                             literal_error
 912                         )
 913                         .emit();
 914                     }
 915                 } else if let Some(meta_item) = item.meta_item() {
 916                     if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 917                         if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
 918                             let name = meta_item.name_or_empty().to_ident_string();
 919                             recognised = true;
 920                             let mut err = struct_span_err!(
 921                                 diagnostic,
 922                                 item.span(),
 923                                 E0693,
 924                                 "incorrect `repr({})` attribute format",
 925                                 name,
 926                             );
 927                             match value.kind {
 928                                 ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 929                                     err.span_suggestion(
 930                                         item.span(),
 931                                         "use parentheses instead",
 932                                         format!("{}({})", name, int),
 933                                         Applicability::MachineApplicable,
 934                                     );
 935                                 }
 936                                 ast::LitKind::Str(s, _) => {
 937                                     err.span_suggestion(
 938                                         item.span(),
 939                                         "use parentheses instead",
 940                                         format!("{}({})", name, s),
 941                                         Applicability::MachineApplicable,
 942                                     );
 943                                 }
 944                                 _ => {}
 945                             }
 946                             err.emit();
 947                         } else {
 948                             if matches!(
 949                                 meta_item.name_or_empty(),
 950                                 sym::C | sym::simd | sym::transparent | sym::no_niche
 951                             ) || int_type_of_word(meta_item.name_or_empty()).is_some()
 952                             {
 953                                 recognised = true;
 954                                 struct_span_err!(
 955                                     diagnostic,
 956                                     meta_item.span,
 957                                     E0552,
 958                                     "invalid representation hint: `{}` does not take a value",
 959                                     meta_item.name_or_empty().to_ident_string(),
 960                                 )
 961                                 .emit();
 962                             }
 963                         }
 964                     } else if let MetaItemKind::List(_) = meta_item.kind {
 965                         if meta_item.has_name(sym::align) {
 966                             recognised = true;
 967                             struct_span_err!(
 968                                 diagnostic,
 969                                 meta_item.span,
 970                                 E0693,
 971                                 "incorrect `repr(align)` attribute format: \
 972                                  `align` takes exactly one argument in parentheses"
 973                             )
 974                             .emit();
 975                         } else if meta_item.has_name(sym::packed) {
 976                             recognised = true;
 977                             struct_span_err!(
 978                                 diagnostic,
 979                                 meta_item.span,
 980                                 E0552,
 981                                 "incorrect `repr(packed)` attribute format: \
 982                                  `packed` takes exactly one parenthesized argument, \
 983                                  or no parentheses at all"
 984                             )
 985                             .emit();
 986                         } else if matches!(
 987                             meta_item.name_or_empty(),
 988                             sym::C | sym::simd | sym::transparent | sym::no_niche
 989                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
 990                         {
 991                             recognised = true;
 992                             struct_span_err!(
 993                                 diagnostic,
 994                                 meta_item.span,
 995                                 E0552,
 996                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
 997                                 meta_item.name_or_empty().to_ident_string(),
 998                             ).emit();
 999                         }
1000                     }
1001                 }
1002                 if !recognised {
1003                     // Not a word we recognize. This will be caught and reported by
1004                     // the `check_mod_attrs` pass, but this pass doesn't always run
1005                     // (e.g. if we only pretty-print the source), so we have to gate
1006                     // the `delay_span_bug` call as follows:
1007                     if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1008                         diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1009                     }
1010                 }
1011             }
1012         }
1013     }
1014     acc
1015 }
1016
1017 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1018     use IntType::*;
1019
1020     match s {
1021         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1022         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1023         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1024         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1025         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1026         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1027         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1028         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1029         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1030         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1031         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1032         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1033         _ => None,
1034     }
1035 }
1036
1037 pub enum TransparencyError {
1038     UnknownTransparency(Symbol, Span),
1039     MultipleTransparencyAttrs(Span, Span),
1040 }
1041
1042 pub fn find_transparency(
1043     attrs: &[Attribute],
1044     macro_rules: bool,
1045 ) -> (Transparency, Option<TransparencyError>) {
1046     let mut transparency = None;
1047     let mut error = None;
1048     for attr in attrs {
1049         if attr.has_name(sym::rustc_macro_transparency) {
1050             if let Some((_, old_span)) = transparency {
1051                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1052                 break;
1053             } else if let Some(value) = attr.value_str() {
1054                 transparency = Some((
1055                     match value {
1056                         sym::transparent => Transparency::Transparent,
1057                         sym::semitransparent => Transparency::SemiTransparent,
1058                         sym::opaque => Transparency::Opaque,
1059                         _ => {
1060                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1061                             continue;
1062                         }
1063                     },
1064                     attr.span,
1065                 ));
1066             }
1067         }
1068     }
1069     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1070     (transparency.map_or(fallback, |t| t.0), error)
1071 }
1072
1073 pub fn allow_internal_unstable<'a>(
1074     sess: &'a Session,
1075     attrs: &'a [Attribute],
1076 ) -> impl Iterator<Item = Symbol> + 'a {
1077     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1078 }
1079
1080 pub fn rustc_allow_const_fn_unstable<'a>(
1081     sess: &'a Session,
1082     attrs: &'a [Attribute],
1083 ) -> impl Iterator<Item = Symbol> + 'a {
1084     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1085 }
1086
1087 fn allow_unstable<'a>(
1088     sess: &'a Session,
1089     attrs: &'a [Attribute],
1090     symbol: Symbol,
1091 ) -> impl Iterator<Item = Symbol> + 'a {
1092     let attrs = sess.filter_by_name(attrs, symbol);
1093     let list = attrs
1094         .filter_map(move |attr| {
1095             attr.meta_item_list().or_else(|| {
1096                 sess.diagnostic().span_err(
1097                     attr.span,
1098                     &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
1099                 );
1100                 None
1101             })
1102         })
1103         .flatten();
1104
1105     list.into_iter().filter_map(move |it| {
1106         let name = it.ident().map(|ident| ident.name);
1107         if name.is_none() {
1108             sess.diagnostic().span_err(
1109                 it.span(),
1110                 &format!("`{}` expects feature names", symbol.to_ident_string()),
1111             );
1112         }
1113         name
1114     })
1115 }
1116
1117 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1118     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1119         if literal.is_power_of_two() {
1120             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1121             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1122         } else {
1123             Err("not a power of two")
1124         }
1125     } else {
1126         Err("not an unsuffixed integer")
1127     }
1128 }