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..],
  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 impl Stability {
 105     pub fn is_unstable(&self) -> bool {
 106         self.level.is_unstable()
 107     }
 108
 109     pub fn is_stable(&self) -> bool {
 110         self.level.is_stable()
 111     }
 112 }
 113
 114 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 115 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 116 #[derive(HashStable_Generic)]
 117 pub struct ConstStability {
 118     pub level: StabilityLevel,
 119     pub feature: Symbol,
 120     /// whether the function has a `#[rustc_promotable]` attribute
 121     pub promotable: bool,
 122 }
 123
 124 impl ConstStability {
 125     pub fn is_const_unstable(&self) -> bool {
 126         self.level.is_unstable()
 127     }
 128
 129     pub fn is_const_stable(&self) -> bool {
 130         self.level.is_stable()
 131     }
 132 }
 133
 134 /// The available stability levels.
 135 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 136 #[derive(HashStable_Generic)]
 137 pub enum StabilityLevel {
 138     // Reason for the current stability level and the relevant rust-lang issue
 139     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 140     Stable { since: Symbol },
 141 }
 142
 143 impl StabilityLevel {
 144     pub fn is_unstable(&self) -> bool {
 145         matches!(self, StabilityLevel::Unstable { .. })
 146     }
 147     pub fn is_stable(&self) -> bool {
 148         matches!(self, StabilityLevel::Stable { .. })
 149     }
 150 }
 151
 152 /// Collects stability info from all stability attributes in `attrs`.
 153 /// Returns `None` if no stability attributes are found.
 154 pub fn find_stability(
 155     sess: &Session,
 156     attrs: &[Attribute],
 157     item_sp: Span,
 158 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
 159     find_stability_generic(sess, attrs.iter(), item_sp)
 160 }
 161
 162 fn find_stability_generic<'a, I>(
 163     sess: &Session,
 164     attrs_iter: I,
 165     item_sp: Span,
 166 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
 167 where
 168     I: Iterator<Item = &'a Attribute>,
 169 {
 170     use StabilityLevel::*;
 171
 172     let mut stab: Option<(Stability, Span)> = None;
 173     let mut const_stab: Option<(ConstStability, Span)> = None;
 174     let mut promotable = false;
 175
 176     let diagnostic = &sess.parse_sess.span_diagnostic;
 177
 178     'outer: for attr in attrs_iter {
 179         if ![
 180             sym::rustc_const_unstable,
 181             sym::rustc_const_stable,
 182             sym::unstable,
 183             sym::stable,
 184             sym::rustc_promotable,
 185         ]
 186         .iter()
 187         .any(|&s| attr.has_name(s))
 188         {
 189             continue; // not a stability level
 190         }
 191
 192         let meta = attr.meta();
 193
 194         if attr.has_name(sym::rustc_promotable) {
 195             promotable = true;
 196         }
 197         // attributes with data
 198         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 199             let meta = meta.as_ref().unwrap();
 200             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 201                 if item.is_some() {
 202                     handle_errors(
 203                         &sess.parse_sess,
 204                         meta.span,
 205                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 206                     );
 207                     return false;
 208                 }
 209                 if let Some(v) = meta.value_str() {
 210                     *item = Some(v);
 211                     true
 212                 } else {
 213                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 214                     false
 215                 }
 216             };
 217
 218             let meta_name = meta.name_or_empty();
 219             match meta_name {
 220                 sym::rustc_const_unstable | sym::unstable => {
 221                     if meta_name == sym::unstable && stab.is_some() {
 222                         handle_errors(
 223                             &sess.parse_sess,
 224                             attr.span,
 225                             AttrError::MultipleStabilityLevels,
 226                         );
 227                         break;
 228                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 229                         handle_errors(
 230                             &sess.parse_sess,
 231                             attr.span,
 232                             AttrError::MultipleStabilityLevels,
 233                         );
 234                         break;
 235                     }
 236
 237                     let mut feature = None;
 238                     let mut reason = None;
 239                     let mut issue = None;
 240                     let mut issue_num = None;
 241                     let mut is_soft = false;
 242                     for meta in metas {
 243                         let Some(mi) = meta.meta_item() else {
 244                             handle_errors(
 245                                 &sess.parse_sess,
 246                                 meta.span(),
 247                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 248                             );
 249                             continue 'outer;
 250                         };
 251                         match mi.name_or_empty() {
 252                             sym::feature => {
 253                                 if !get(mi, &mut feature) {
 254                                     continue 'outer;
 255                                 }
 256                             }
 257                             sym::reason => {
 258                                 if !get(mi, &mut reason) {
 259                                     continue 'outer;
 260                                 }
 261                             }
 262                             sym::issue => {
 263                                 if !get(mi, &mut issue) {
 264                                     continue 'outer;
 265                                 }
 266
 267                                 // These unwraps are safe because `get` ensures the meta item
 268                                 // is a name/value pair string literal.
 269                                 issue_num = match issue.unwrap().as_str() {
 270                                     "none" => None,
 271                                     issue => {
 272                                         let emit_diag = |msg: &str| {
 273                                             struct_span_err!(
 274                                                 diagnostic,
 275                                                 mi.span,
 276                                                 E0545,
 277                                                 "`issue` must be a non-zero numeric string \
 278                                                 or \"none\"",
 279                                             )
 280                                             .span_label(mi.name_value_literal_span().unwrap(), msg)
 281                                             .emit();
 282                                         };
 283                                         match issue.parse() {
 284                                             Ok(0) => {
 285                                                 emit_diag(
 286                                                     "`issue` must not be \"0\", \
 287                                                     use \"none\" instead",
 288                                                 );
 289                                                 continue 'outer;
 290                                             }
 291                                             Ok(num) => NonZeroU32::new(num),
 292                                             Err(err) => {
 293                                                 emit_diag(&err.to_string());
 294                                                 continue 'outer;
 295                                             }
 296                                         }
 297                                     }
 298                                 };
 299                             }
 300                             sym::soft => {
 301                                 if !mi.is_word() {
 302                                     let msg = "`soft` should not have any arguments";
 303                                     sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 304                                 }
 305                                 is_soft = true;
 306                             }
 307                             _ => {
 308                                 handle_errors(
 309                                     &sess.parse_sess,
 310                                     meta.span(),
 311                                     AttrError::UnknownMetaItem(
 312                                         pprust::path_to_string(&mi.path),
 313                                         &["feature", "reason", "issue", "soft"],
 314                                     ),
 315                                 );
 316                                 continue 'outer;
 317                             }
 318                         }
 319                     }
 320
 321                     match (feature, reason, issue) {
 322                         (Some(feature), reason, Some(_)) => {
 323                             if !rustc_lexer::is_ident(feature.as_str()) {
 324                                 handle_errors(
 325                                     &sess.parse_sess,
 326                                     attr.span,
 327                                     AttrError::NonIdentFeature,
 328                                 );
 329                                 continue;
 330                             }
 331                             let level = Unstable { reason, issue: issue_num, is_soft };
 332                             if sym::unstable == meta_name {
 333                                 stab = Some((Stability { level, feature }, attr.span));
 334                             } else {
 335                                 const_stab = Some((
 336                                     ConstStability { level, feature, promotable: false },
 337                                     attr.span,
 338                                 ));
 339                             }
 340                         }
 341                         (None, _, _) => {
 342                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 343                             continue;
 344                         }
 345                         _ => {
 346                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 347                                 .emit();
 348                             continue;
 349                         }
 350                     }
 351                 }
 352                 sym::rustc_const_stable | sym::stable => {
 353                     if meta_name == sym::stable && stab.is_some() {
 354                         handle_errors(
 355                             &sess.parse_sess,
 356                             attr.span,
 357                             AttrError::MultipleStabilityLevels,
 358                         );
 359                         break;
 360                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 361                         handle_errors(
 362                             &sess.parse_sess,
 363                             attr.span,
 364                             AttrError::MultipleStabilityLevels,
 365                         );
 366                         break;
 367                     }
 368
 369                     let mut feature = None;
 370                     let mut since = None;
 371                     for meta in metas {
 372                         match meta {
 373                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 374                                 sym::feature => {
 375                                     if !get(mi, &mut feature) {
 376                                         continue 'outer;
 377                                     }
 378                                 }
 379                                 sym::since => {
 380                                     if !get(mi, &mut since) {
 381                                         continue 'outer;
 382                                     }
 383                                 }
 384                                 _ => {
 385                                     handle_errors(
 386                                         &sess.parse_sess,
 387                                         meta.span(),
 388                                         AttrError::UnknownMetaItem(
 389                                             pprust::path_to_string(&mi.path),
 390                                             &["since", "note"],
 391                                         ),
 392                                     );
 393                                     continue 'outer;
 394                                 }
 395                             },
 396                             NestedMetaItem::Literal(lit) => {
 397                                 handle_errors(
 398                                     &sess.parse_sess,
 399                                     lit.span,
 400                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 401                                 );
 402                                 continue 'outer;
 403                             }
 404                         }
 405                     }
 406
 407                     match (feature, since) {
 408                         (Some(feature), Some(since)) => {
 409                             let level = Stable { since };
 410                             if sym::stable == meta_name {
 411                                 stab = Some((Stability { level, feature }, attr.span));
 412                             } else {
 413                                 const_stab = Some((
 414                                     ConstStability { level, feature, promotable: false },
 415                                     attr.span,
 416                                 ));
 417                             }
 418                         }
 419                         (None, _) => {
 420                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 421                             continue;
 422                         }
 423                         _ => {
 424                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 425                             continue;
 426                         }
 427                     }
 428                 }
 429                 _ => unreachable!(),
 430             }
 431         }
 432     }
 433
 434     // Merge the const-unstable info into the stability info
 435     if promotable {
 436         if let Some((ref mut stab, _)) = const_stab {
 437             stab.promotable = promotable;
 438         } else {
 439             struct_span_err!(
 440                 diagnostic,
 441                 item_sp,
 442                 E0717,
 443                 "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
 444                 or a `rustc_const_stable` attribute"
 445             )
 446             .emit();
 447         }
 448     }
 449
 450     (stab, const_stab)
 451 }
 452
 453 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 454     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 455 }
 456
 457 #[derive(Clone, Debug)]
 458 pub struct Condition {
 459     pub name: Symbol,
 460     pub name_span: Span,
 461     pub value: Option<Symbol>,
 462     pub value_span: Option<Span>,
 463     pub span: Span,
 464 }
 465
 466 /// Tests if a cfg-pattern matches the cfg set
 467 pub fn cfg_matches(
 468     cfg: &ast::MetaItem,
 469     sess: &ParseSess,
 470     lint_node_id: NodeId,
 471     features: Option<&Features>,
 472 ) -> bool {
 473     eval_condition(cfg, sess, features, &mut |cfg| {
 474         try_gate_cfg(cfg.name, cfg.span, sess, features);
 475         if let Some(names_valid) = &sess.check_config.names_valid {
 476             if !names_valid.contains(&cfg.name) {
 477                 sess.buffer_lint_with_diagnostic(
 478                     UNEXPECTED_CFGS,
 479                     cfg.span,
 480                     lint_node_id,
 481                     "unexpected `cfg` condition name",
 482                     BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
 483                 );
 484             }
 485         }
 486         if let Some(value) = cfg.value {
 487             if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
 488                 if !values.contains(&value) {
 489                     sess.buffer_lint_with_diagnostic(
 490                         UNEXPECTED_CFGS,
 491                         cfg.span,
 492                         lint_node_id,
 493                         "unexpected `cfg` condition value",
 494                         BuiltinLintDiagnostics::UnexpectedCfg(
 495                             (cfg.name, cfg.name_span),
 496                             cfg.value_span.map(|vs| (value, vs)),
 497                         ),
 498                     );
 499                 }
 500             }
 501         }
 502         sess.config.contains(&(cfg.name, cfg.value))
 503     })
 504 }
 505
 506 fn try_gate_cfg(name: Symbol, span: Span, sess: &ParseSess, features: Option<&Features>) {
 507     let gate = find_gated_cfg(|sym| sym == name);
 508     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 509         gate_cfg(&gated_cfg, span, sess, feats);
 510     }
 511 }
 512
 513 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 514     let (cfg, feature, has_feature) = gated_cfg;
 515     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 516         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 517         feature_err(sess, *feature, cfg_span, &explain).emit();
 518     }
 519 }
 520
 521 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 522 struct Version {
 523     major: u16,
 524     minor: u16,
 525     patch: u16,
 526 }
 527
 528 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 529     let mut components = s.split('-');
 530     let d = components.next()?;
 531     if !allow_appendix && components.next().is_some() {
 532         return None;
 533     }
 534     let mut digits = d.splitn(3, '.');
 535     let major = digits.next()?.parse().ok()?;
 536     let minor = digits.next()?.parse().ok()?;
 537     let patch = digits.next().unwrap_or("0").parse().ok()?;
 538     Some(Version { major, minor, patch })
 539 }
 540
 541 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 542 /// evaluate individual items.
 543 pub fn eval_condition(
 544     cfg: &ast::MetaItem,
 545     sess: &ParseSess,
 546     features: Option<&Features>,
 547     eval: &mut impl FnMut(Condition) -> bool,
 548 ) -> bool {
 549     match cfg.kind {
 550         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 551             try_gate_cfg(sym::version, cfg.span, sess, features);
 552             let (min_version, span) = match &mis[..] {
 553                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 554                     (sym, span)
 555                 }
 556                 [
 557                     NestedMetaItem::Literal(Lit { span, .. })
 558                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 559                 ] => {
 560                     sess.span_diagnostic
 561                         .struct_span_err(*span, "expected a version literal")
 562                         .emit();
 563                     return false;
 564                 }
 565                 [..] => {
 566                     sess.span_diagnostic
 567                         .struct_span_err(cfg.span, "expected single version literal")
 568                         .emit();
 569                     return false;
 570                 }
 571             };
 572             let Some(min_version) = parse_version(min_version.as_str(), false) else {
 573                 sess.span_diagnostic
 574                     .struct_span_warn(
 575                         *span,
 576                         "unknown version literal format, assuming it refers to a future version",
 577                     )
 578                     .emit();
 579                 return false;
 580             };
 581             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 582
 583             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 584             if sess.assume_incomplete_release {
 585                 rustc_version > min_version
 586             } else {
 587                 rustc_version >= min_version
 588             }
 589         }
 590         ast::MetaItemKind::List(ref mis) => {
 591             for mi in mis.iter() {
 592                 if !mi.is_meta_item() {
 593                     handle_errors(
 594                         sess,
 595                         mi.span(),
 596                         AttrError::UnsupportedLiteral("unsupported literal", false),
 597                     );
 598                     return false;
 599                 }
 600             }
 601
 602             // The unwraps below may look dangerous, but we've already asserted
 603             // that they won't fail with the loop above.
 604             match cfg.name_or_empty() {
 605                 sym::any => mis
 606                     .iter()
 607                     // We don't use any() here, because we want to evaluate all cfg condition
 608                     // as eval_condition can (and does) extra checks
 609                     .fold(false, |res, mi| {
 610                         res | eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 611                     }),
 612                 sym::all => mis
 613                     .iter()
 614                     // We don't use all() here, because we want to evaluate all cfg condition
 615                     // as eval_condition can (and does) extra checks
 616                     .fold(true, |res, mi| {
 617                         res & eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 618                     }),
 619                 sym::not => {
 620                     if mis.len() != 1 {
 621                         struct_span_err!(
 622                             sess.span_diagnostic,
 623                             cfg.span,
 624                             E0536,
 625                             "expected 1 cfg-pattern"
 626                         )
 627                         .emit();
 628                         return false;
 629                     }
 630
 631                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 632                 }
 633                 sym::target => {
 634                     if let Some(features) = features && !features.cfg_target_compact {
 635                         feature_err(
 636                             sess,
 637                             sym::cfg_target_compact,
 638                             cfg.span,
 639                             &"compact `cfg(target(..))` is experimental and subject to change"
 640                         ).emit();
 641                     }
 642
 643                     mis.iter().fold(true, |res, mi| {
 644                         let mut mi = mi.meta_item().unwrap().clone();
 645                         if let [seg, ..] = &mut mi.path.segments[..] {
 646                             seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
 647                         }
 648
 649                         res & eval_condition(&mi, sess, features, eval)
 650                     })
 651                 }
 652                 _ => {
 653                     struct_span_err!(
 654                         sess.span_diagnostic,
 655                         cfg.span,
 656                         E0537,
 657                         "invalid predicate `{}`",
 658                         pprust::path_to_string(&cfg.path)
 659                     )
 660                     .emit();
 661                     false
 662                 }
 663             }
 664         }
 665         ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
 666             sess.span_diagnostic
 667                 .span_err(cfg.path.span, "`cfg` predicate key must be an identifier");
 668             true
 669         }
 670         MetaItemKind::NameValue(ref lit) if !lit.kind.is_str() => {
 671             handle_errors(
 672                 sess,
 673                 lit.span,
 674                 AttrError::UnsupportedLiteral(
 675                     "literal in `cfg` predicate value must be a string",
 676                     lit.kind.is_bytestr(),
 677                 ),
 678             );
 679             true
 680         }
 681         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
 682             let ident = cfg.ident().expect("multi-segment cfg predicate");
 683             eval(Condition {
 684                 name: ident.name,
 685                 name_span: ident.span,
 686                 value: cfg.value_str(),
 687                 value_span: cfg.name_value_literal_span(),
 688                 span: cfg.span,
 689             })
 690         }
 691     }
 692 }
 693
 694 #[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 695 pub struct Deprecation {
 696     pub since: Option<Symbol>,
 697     /// The note to issue a reason.
 698     pub note: Option<Symbol>,
 699     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 700     ///
 701     /// This is currently unstable.
 702     pub suggestion: Option<Symbol>,
 703
 704     /// Whether to treat the since attribute as being a Rust version identifier
 705     /// (rather than an opaque string).
 706     pub is_since_rustc_version: bool,
 707 }
 708
 709 /// Finds the deprecation attribute. `None` if none exists.
 710 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 711     find_deprecation_generic(sess, attrs.iter())
 712 }
 713
 714 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 715 where
 716     I: Iterator<Item = &'a Attribute>,
 717 {
 718     let mut depr: Option<(Deprecation, Span)> = None;
 719     let diagnostic = &sess.parse_sess.span_diagnostic;
 720     let is_rustc = sess.features_untracked().staged_api;
 721
 722     'outer: for attr in attrs_iter {
 723         if !attr.has_name(sym::deprecated) {
 724             continue;
 725         }
 726
 727         let Some(meta) = attr.meta() else {
 728             continue;
 729         };
 730         let mut since = None;
 731         let mut note = None;
 732         let mut suggestion = None;
 733         match &meta.kind {
 734             MetaItemKind::Word => {}
 735             MetaItemKind::NameValue(..) => note = meta.value_str(),
 736             MetaItemKind::List(list) => {
 737                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 738                     if item.is_some() {
 739                         handle_errors(
 740                             &sess.parse_sess,
 741                             meta.span,
 742                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 743                         );
 744                         return false;
 745                     }
 746                     if let Some(v) = meta.value_str() {
 747                         *item = Some(v);
 748                         true
 749                     } else {
 750                         if let Some(lit) = meta.name_value_literal() {
 751                             handle_errors(
 752                                 &sess.parse_sess,
 753                                 lit.span,
 754                                 AttrError::UnsupportedLiteral(
 755                                     "literal in `deprecated` \
 756                                     value must be a string",
 757                                     lit.kind.is_bytestr(),
 758                                 ),
 759                             );
 760                         } else {
 761                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 762                                 .emit();
 763                         }
 764
 765                         false
 766                     }
 767                 };
 768
 769                 for meta in list {
 770                     match meta {
 771                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 772                             sym::since => {
 773                                 if !get(mi, &mut since) {
 774                                     continue 'outer;
 775                                 }
 776                             }
 777                             sym::note => {
 778                                 if !get(mi, &mut note) {
 779                                     continue 'outer;
 780                                 }
 781                             }
 782                             sym::suggestion => {
 783                                 if !sess.features_untracked().deprecated_suggestion {
 784                                     let mut diag = sess.struct_span_err(
 785                                         mi.span,
 786                                         "suggestions on deprecated items are unstable",
 787                                     );
 788                                     if sess.is_nightly_build() {
 789                                         diag.help("add `#![feature(deprecated_suggestion)]` to the crate root");
 790                                     }
 791                                     diag.note("see #94785 for more details").emit();
 792                                 }
 793
 794                                 if !get(mi, &mut suggestion) {
 795                                     continue 'outer;
 796                                 }
 797                             }
 798                             _ => {
 799                                 handle_errors(
 800                                     &sess.parse_sess,
 801                                     meta.span(),
 802                                     AttrError::UnknownMetaItem(
 803                                         pprust::path_to_string(&mi.path),
 804                                         if sess.features_untracked().deprecated_suggestion {
 805                                             &["since", "note", "suggestion"]
 806                                         } else {
 807                                             &["since", "note"]
 808                                         },
 809                                     ),
 810                                 );
 811                                 continue 'outer;
 812                             }
 813                         },
 814                         NestedMetaItem::Literal(lit) => {
 815                             handle_errors(
 816                                 &sess.parse_sess,
 817                                 lit.span,
 818                                 AttrError::UnsupportedLiteral(
 819                                     "item in `deprecated` must be a key/value pair",
 820                                     false,
 821                                 ),
 822                             );
 823                             continue 'outer;
 824                         }
 825                     }
 826                 }
 827             }
 828         }
 829
 830         if is_rustc {
 831             if since.is_none() {
 832                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 833                 continue;
 834             }
 835
 836             if note.is_none() {
 837                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'note'").emit();
 838                 continue;
 839             }
 840         }
 841
 842         depr = Some((
 843             Deprecation { since, note, suggestion, is_since_rustc_version: is_rustc },
 844             attr.span,
 845         ));
 846     }
 847
 848     depr
 849 }
 850
 851 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 852 pub enum ReprAttr {
 853     ReprInt(IntType),
 854     ReprC,
 855     ReprPacked(u32),
 856     ReprSimd,
 857     ReprTransparent,
 858     ReprAlign(u32),
 859     ReprNoNiche,
 860 }
 861
 862 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 863 #[derive(Encodable, Decodable, HashStable_Generic)]
 864 pub enum IntType {
 865     SignedInt(ast::IntTy),
 866     UnsignedInt(ast::UintTy),
 867 }
 868
 869 impl IntType {
 870     #[inline]
 871     pub fn is_signed(self) -> bool {
 872         use IntType::*;
 873
 874         match self {
 875             SignedInt(..) => true,
 876             UnsignedInt(..) => false,
 877         }
 878     }
 879 }
 880
 881 /// Parse #[repr(...)] forms.
 882 ///
 883 /// Valid repr contents: any of the primitive integral type names (see
 884 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 885 /// the same discriminant size that the corresponding C enum would or C
 886 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 887 /// concerns to the only non-ZST field.
 888 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 889     if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
 890 }
 891
 892 pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 893     assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {:?}", attr);
 894     use ReprAttr::*;
 895     let mut acc = Vec::new();
 896     let diagnostic = &sess.parse_sess.span_diagnostic;
 897
 898     if let Some(items) = attr.meta_item_list() {
 899         for item in items {
 900             let mut recognised = false;
 901             if item.is_word() {
 902                 let hint = match item.name_or_empty() {
 903                     sym::C => Some(ReprC),
 904                     sym::packed => Some(ReprPacked(1)),
 905                     sym::simd => Some(ReprSimd),
 906                     sym::transparent => Some(ReprTransparent),
 907                     sym::no_niche => Some(ReprNoNiche),
 908                     sym::align => {
 909                         let mut err = struct_span_err!(
 910                             diagnostic,
 911                             item.span(),
 912                             E0589,
 913                             "invalid `repr(align)` attribute: `align` needs an argument"
 914                         );
 915                         err.span_suggestion(
 916                             item.span(),
 917                             "supply an argument here",
 918                             "align(...)",
 919                             Applicability::HasPlaceholders,
 920                         );
 921                         err.emit();
 922                         recognised = true;
 923                         None
 924                     }
 925                     name => int_type_of_word(name).map(ReprInt),
 926                 };
 927
 928                 if let Some(h) = hint {
 929                     recognised = true;
 930                     acc.push(h);
 931                 }
 932             } else if let Some((name, value)) = item.name_value_literal() {
 933                 let mut literal_error = None;
 934                 if name == sym::align {
 935                     recognised = true;
 936                     match parse_alignment(&value.kind) {
 937                         Ok(literal) => acc.push(ReprAlign(literal)),
 938                         Err(message) => literal_error = Some(message),
 939                     };
 940                 } else if name == sym::packed {
 941                     recognised = true;
 942                     match parse_alignment(&value.kind) {
 943                         Ok(literal) => acc.push(ReprPacked(literal)),
 944                         Err(message) => literal_error = Some(message),
 945                     };
 946                 } else if matches!(name, sym::C | sym::simd | sym::transparent | sym::no_niche)
 947                     || int_type_of_word(name).is_some()
 948                 {
 949                     recognised = true;
 950                     struct_span_err!(
 951                                 diagnostic,
 952                                 item.span(),
 953                                 E0552,
 954                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
 955                                 name.to_ident_string(),
 956                             ).emit();
 957                 }
 958                 if let Some(literal_error) = literal_error {
 959                     struct_span_err!(
 960                         diagnostic,
 961                         item.span(),
 962                         E0589,
 963                         "invalid `repr({})` attribute: {}",
 964                         name.to_ident_string(),
 965                         literal_error
 966                     )
 967                     .emit();
 968                 }
 969             } else if let Some(meta_item) = item.meta_item() {
 970                 if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 971                     if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
 972                         let name = meta_item.name_or_empty().to_ident_string();
 973                         recognised = true;
 974                         let mut err = struct_span_err!(
 975                             diagnostic,
 976                             item.span(),
 977                             E0693,
 978                             "incorrect `repr({})` attribute format",
 979                             name,
 980                         );
 981                         match value.kind {
 982                             ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 983                                 err.span_suggestion(
 984                                     item.span(),
 985                                     "use parentheses instead",
 986                                     format!("{}({})", name, int),
 987                                     Applicability::MachineApplicable,
 988                                 );
 989                             }
 990                             ast::LitKind::Str(s, _) => {
 991                                 err.span_suggestion(
 992                                     item.span(),
 993                                     "use parentheses instead",
 994                                     format!("{}({})", name, s),
 995                                     Applicability::MachineApplicable,
 996                                 );
 997                             }
 998                             _ => {}
 999                         }
1000                         err.emit();
1001                     } else {
1002                         if matches!(
1003                             meta_item.name_or_empty(),
1004                             sym::C | sym::simd | sym::transparent | sym::no_niche
1005                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1006                         {
1007                             recognised = true;
1008                             struct_span_err!(
1009                                 diagnostic,
1010                                 meta_item.span,
1011                                 E0552,
1012                                 "invalid representation hint: `{}` does not take a value",
1013                                 meta_item.name_or_empty().to_ident_string(),
1014                             )
1015                             .emit();
1016                         }
1017                     }
1018                 } else if let MetaItemKind::List(_) = meta_item.kind {
1019                     if meta_item.has_name(sym::align) {
1020                         recognised = true;
1021                         struct_span_err!(
1022                             diagnostic,
1023                             meta_item.span,
1024                             E0693,
1025                             "incorrect `repr(align)` attribute format: \
1026                                  `align` takes exactly one argument in parentheses"
1027                         )
1028                         .emit();
1029                     } else if meta_item.has_name(sym::packed) {
1030                         recognised = true;
1031                         struct_span_err!(
1032                             diagnostic,
1033                             meta_item.span,
1034                             E0552,
1035                             "incorrect `repr(packed)` attribute format: \
1036                                  `packed` takes exactly one parenthesized argument, \
1037                                  or no parentheses at all"
1038                         )
1039                         .emit();
1040                     } else if matches!(
1041                         meta_item.name_or_empty(),
1042                         sym::C | sym::simd | sym::transparent | sym::no_niche
1043                     ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1044                     {
1045                         recognised = true;
1046                         struct_span_err!(
1047                                 diagnostic,
1048                                 meta_item.span,
1049                                 E0552,
1050                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
1051                                 meta_item.name_or_empty().to_ident_string(),
1052                             ).emit();
1053                     }
1054                 }
1055             }
1056             if !recognised {
1057                 // Not a word we recognize. This will be caught and reported by
1058                 // the `check_mod_attrs` pass, but this pass doesn't always run
1059                 // (e.g. if we only pretty-print the source), so we have to gate
1060                 // the `delay_span_bug` call as follows:
1061                 if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1062                     diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1063                 }
1064             }
1065         }
1066     }
1067     acc
1068 }
1069
1070 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1071     use IntType::*;
1072
1073     match s {
1074         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1075         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1076         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1077         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1078         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1079         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1080         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1081         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1082         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1083         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1084         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1085         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1086         _ => None,
1087     }
1088 }
1089
1090 pub enum TransparencyError {
1091     UnknownTransparency(Symbol, Span),
1092     MultipleTransparencyAttrs(Span, Span),
1093 }
1094
1095 pub fn find_transparency(
1096     attrs: &[Attribute],
1097     macro_rules: bool,
1098 ) -> (Transparency, Option<TransparencyError>) {
1099     let mut transparency = None;
1100     let mut error = None;
1101     for attr in attrs {
1102         if attr.has_name(sym::rustc_macro_transparency) {
1103             if let Some((_, old_span)) = transparency {
1104                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1105                 break;
1106             } else if let Some(value) = attr.value_str() {
1107                 transparency = Some((
1108                     match value {
1109                         sym::transparent => Transparency::Transparent,
1110                         sym::semitransparent => Transparency::SemiTransparent,
1111                         sym::opaque => Transparency::Opaque,
1112                         _ => {
1113                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1114                             continue;
1115                         }
1116                     },
1117                     attr.span,
1118                 ));
1119             }
1120         }
1121     }
1122     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1123     (transparency.map_or(fallback, |t| t.0), error)
1124 }
1125
1126 pub fn allow_internal_unstable<'a>(
1127     sess: &'a Session,
1128     attrs: &'a [Attribute],
1129 ) -> impl Iterator<Item = Symbol> + 'a {
1130     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1131 }
1132
1133 pub fn rustc_allow_const_fn_unstable<'a>(
1134     sess: &'a Session,
1135     attrs: &'a [Attribute],
1136 ) -> impl Iterator<Item = Symbol> + 'a {
1137     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1138 }
1139
1140 fn allow_unstable<'a>(
1141     sess: &'a Session,
1142     attrs: &'a [Attribute],
1143     symbol: Symbol,
1144 ) -> impl Iterator<Item = Symbol> + 'a {
1145     let attrs = sess.filter_by_name(attrs, symbol);
1146     let list = attrs
1147         .filter_map(move |attr| {
1148             attr.meta_item_list().or_else(|| {
1149                 sess.diagnostic().span_err(
1150                     attr.span,
1151                     &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
1152                 );
1153                 None
1154             })
1155         })
1156         .flatten();
1157
1158     list.into_iter().filter_map(move |it| {
1159         let name = it.ident().map(|ident| ident.name);
1160         if name.is_none() {
1161             sess.diagnostic().span_err(
1162                 it.span(),
1163                 &format!("`{}` expects feature names", symbol.to_ident_string()),
1164             );
1165         }
1166         name
1167     })
1168 }
1169
1170 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1171     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1172         if literal.is_power_of_two() {
1173             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1174             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1175         } else {
1176             Err("not a power of two")
1177         }
1178     } else {
1179         Err("not an unsuffixed integer")
1180     }
1181 }