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     /// `#[unstable]`
 139     Unstable {
 140         /// Reason for the current stability level.
 141         reason: UnstableReason,
 142         /// Relevant `rust-lang/rust` issue.
 143         issue: Option<NonZeroU32>,
 144         is_soft: bool,
 145         /// If part of a feature is stabilized and a new feature is added for the remaining parts,
 146         /// then the `implied_by` attribute is used to indicate which now-stable feature previously
 147         /// contained a item.
 148         ///
 149         /// ```pseudo-Rust
 150         /// #[unstable(feature = "foo", issue = "...")]
 151         /// fn foo() {}
 152         /// #[unstable(feature = "foo", issue = "...")]
 153         /// fn foobar() {}
 154         /// ```
 155         ///
 156         /// ...becomes...
 157         ///
 158         /// ```pseudo-Rust
 159         /// #[stable(feature = "foo", since = "1.XX.X")]
 160         /// fn foo() {}
 161         /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
 162         /// fn foobar() {}
 163         /// ```
 164         implied_by: Option<Symbol>,
 165     },
 166     /// `#[stable]`
 167     Stable {
 168         /// Rust release which stabilized this feature.
 169         since: Symbol,
 170         /// Is this item allowed to be referred to on stable, despite being contained in unstable
 171         /// modules?
 172         allowed_through_unstable_modules: bool,
 173     },
 174 }
 175
 176 impl StabilityLevel {
 177     pub fn is_unstable(&self) -> bool {
 178         matches!(self, StabilityLevel::Unstable { .. })
 179     }
 180     pub fn is_stable(&self) -> bool {
 181         matches!(self, StabilityLevel::Stable { .. })
 182     }
 183 }
 184
 185 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 186 #[derive(HashStable_Generic)]
 187 pub enum UnstableReason {
 188     None,
 189     Default,
 190     Some(Symbol),
 191 }
 192
 193 impl UnstableReason {
 194     fn from_opt_reason(reason: Option<Symbol>) -> Self {
 195         // UnstableReason::Default constructed manually
 196         match reason {
 197             Some(r) => Self::Some(r),
 198             None => Self::None,
 199         }
 200     }
 201
 202     pub fn to_opt_reason(&self) -> Option<Symbol> {
 203         match self {
 204             Self::None => None,
 205             Self::Default => Some(sym::unstable_location_reason_default),
 206             Self::Some(r) => Some(*r),
 207         }
 208     }
 209 }
 210
 211 /// Collects stability info from all stability attributes in `attrs`.
 212 /// Returns `None` if no stability attributes are found.
 213 pub fn find_stability(
 214     sess: &Session,
 215     attrs: &[Attribute],
 216     item_sp: Span,
 217 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
 218     find_stability_generic(sess, attrs.iter(), item_sp)
 219 }
 220
 221 fn find_stability_generic<'a, I>(
 222     sess: &Session,
 223     attrs_iter: I,
 224     item_sp: Span,
 225 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
 226 where
 227     I: Iterator<Item = &'a Attribute>,
 228 {
 229     use StabilityLevel::*;
 230
 231     let mut stab: Option<(Stability, Span)> = None;
 232     let mut const_stab: Option<(ConstStability, Span)> = None;
 233     let mut promotable = false;
 234     let mut allowed_through_unstable_modules = false;
 235
 236     let diagnostic = &sess.parse_sess.span_diagnostic;
 237
 238     'outer: for attr in attrs_iter {
 239         if ![
 240             sym::rustc_const_unstable,
 241             sym::rustc_const_stable,
 242             sym::unstable,
 243             sym::stable,
 244             sym::rustc_promotable,
 245             sym::rustc_allowed_through_unstable_modules,
 246         ]
 247         .iter()
 248         .any(|&s| attr.has_name(s))
 249         {
 250             continue; // not a stability level
 251         }
 252
 253         let meta = attr.meta();
 254
 255         if attr.has_name(sym::rustc_promotable) {
 256             promotable = true;
 257         } else if attr.has_name(sym::rustc_allowed_through_unstable_modules) {
 258             allowed_through_unstable_modules = true;
 259         }
 260         // attributes with data
 261         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 262             let meta = meta.as_ref().unwrap();
 263             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 264                 if item.is_some() {
 265                     handle_errors(
 266                         &sess.parse_sess,
 267                         meta.span,
 268                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 269                     );
 270                     return false;
 271                 }
 272                 if let Some(v) = meta.value_str() {
 273                     *item = Some(v);
 274                     true
 275                 } else {
 276                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 277                     false
 278                 }
 279             };
 280
 281             let meta_name = meta.name_or_empty();
 282             match meta_name {
 283                 sym::rustc_const_unstable | sym::unstable => {
 284                     if meta_name == sym::unstable && stab.is_some() {
 285                         handle_errors(
 286                             &sess.parse_sess,
 287                             attr.span,
 288                             AttrError::MultipleStabilityLevels,
 289                         );
 290                         break;
 291                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 292                         handle_errors(
 293                             &sess.parse_sess,
 294                             attr.span,
 295                             AttrError::MultipleStabilityLevels,
 296                         );
 297                         break;
 298                     }
 299
 300                     let mut feature = None;
 301                     let mut reason = None;
 302                     let mut issue = None;
 303                     let mut issue_num = None;
 304                     let mut is_soft = false;
 305                     let mut implied_by = None;
 306                     for meta in metas {
 307                         let Some(mi) = meta.meta_item() else {
 308                             handle_errors(
 309                                 &sess.parse_sess,
 310                                 meta.span(),
 311                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 312                             );
 313                             continue 'outer;
 314                         };
 315                         match mi.name_or_empty() {
 316                             sym::feature => {
 317                                 if !get(mi, &mut feature) {
 318                                     continue 'outer;
 319                                 }
 320                             }
 321                             sym::reason => {
 322                                 if !get(mi, &mut reason) {
 323                                     continue 'outer;
 324                                 }
 325                             }
 326                             sym::issue => {
 327                                 if !get(mi, &mut issue) {
 328                                     continue 'outer;
 329                                 }
 330
 331                                 // These unwraps are safe because `get` ensures the meta item
 332                                 // is a name/value pair string literal.
 333                                 issue_num = match issue.unwrap().as_str() {
 334                                     "none" => None,
 335                                     issue => {
 336                                         let emit_diag = |msg: &str| {
 337                                             struct_span_err!(
 338                                                 diagnostic,
 339                                                 mi.span,
 340                                                 E0545,
 341                                                 "`issue` must be a non-zero numeric string \
 342                                                 or \"none\"",
 343                                             )
 344                                             .span_label(mi.name_value_literal_span().unwrap(), msg)
 345                                             .emit();
 346                                         };
 347                                         match issue.parse() {
 348                                             Ok(0) => {
 349                                                 emit_diag(
 350                                                     "`issue` must not be \"0\", \
 351                                                     use \"none\" instead",
 352                                                 );
 353                                                 continue 'outer;
 354                                             }
 355                                             Ok(num) => NonZeroU32::new(num),
 356                                             Err(err) => {
 357                                                 emit_diag(&err.to_string());
 358                                                 continue 'outer;
 359                                             }
 360                                         }
 361                                     }
 362                                 };
 363                             }
 364                             sym::soft => {
 365                                 if !mi.is_word() {
 366                                     let msg = "`soft` should not have any arguments";
 367                                     sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 368                                 }
 369                                 is_soft = true;
 370                             }
 371                             sym::implied_by => {
 372                                 if !get(mi, &mut implied_by) {
 373                                     continue 'outer;
 374                                 }
 375                             }
 376                             _ => {
 377                                 handle_errors(
 378                                     &sess.parse_sess,
 379                                     meta.span(),
 380                                     AttrError::UnknownMetaItem(
 381                                         pprust::path_to_string(&mi.path),
 382                                         &["feature", "reason", "issue", "soft"],
 383                                     ),
 384                                 );
 385                                 continue 'outer;
 386                             }
 387                         }
 388                     }
 389
 390                     match (feature, reason, issue) {
 391                         (Some(feature), reason, Some(_)) => {
 392                             if !rustc_lexer::is_ident(feature.as_str()) {
 393                                 handle_errors(
 394                                     &sess.parse_sess,
 395                                     attr.span,
 396                                     AttrError::NonIdentFeature,
 397                                 );
 398                                 continue;
 399                             }
 400                             let level = Unstable {
 401                                 reason: UnstableReason::from_opt_reason(reason),
 402                                 issue: issue_num,
 403                                 is_soft,
 404                                 implied_by,
 405                             };
 406                             if sym::unstable == meta_name {
 407                                 stab = Some((Stability { level, feature }, attr.span));
 408                             } else {
 409                                 const_stab = Some((
 410                                     ConstStability { level, feature, promotable: false },
 411                                     attr.span,
 412                                 ));
 413                             }
 414                         }
 415                         (None, _, _) => {
 416                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 417                             continue;
 418                         }
 419                         _ => {
 420                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 421                                 .emit();
 422                             continue;
 423                         }
 424                     }
 425                 }
 426                 sym::rustc_const_stable | sym::stable => {
 427                     if meta_name == sym::stable && stab.is_some() {
 428                         handle_errors(
 429                             &sess.parse_sess,
 430                             attr.span,
 431                             AttrError::MultipleStabilityLevels,
 432                         );
 433                         break;
 434                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 435                         handle_errors(
 436                             &sess.parse_sess,
 437                             attr.span,
 438                             AttrError::MultipleStabilityLevels,
 439                         );
 440                         break;
 441                     }
 442
 443                     let mut feature = None;
 444                     let mut since = None;
 445                     for meta in metas {
 446                         match meta {
 447                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 448                                 sym::feature => {
 449                                     if !get(mi, &mut feature) {
 450                                         continue 'outer;
 451                                     }
 452                                 }
 453                                 sym::since => {
 454                                     if !get(mi, &mut since) {
 455                                         continue 'outer;
 456                                     }
 457                                 }
 458                                 _ => {
 459                                     handle_errors(
 460                                         &sess.parse_sess,
 461                                         meta.span(),
 462                                         AttrError::UnknownMetaItem(
 463                                             pprust::path_to_string(&mi.path),
 464                                             &["feature", "since"],
 465                                         ),
 466                                     );
 467                                     continue 'outer;
 468                                 }
 469                             },
 470                             NestedMetaItem::Literal(lit) => {
 471                                 handle_errors(
 472                                     &sess.parse_sess,
 473                                     lit.span,
 474                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 475                                 );
 476                                 continue 'outer;
 477                             }
 478                         }
 479                     }
 480
 481                     match (feature, since) {
 482                         (Some(feature), Some(since)) => {
 483                             let level = Stable { since, allowed_through_unstable_modules: false };
 484                             if sym::stable == meta_name {
 485                                 stab = Some((Stability { level, feature }, attr.span));
 486                             } else {
 487                                 const_stab = Some((
 488                                     ConstStability { level, feature, promotable: false },
 489                                     attr.span,
 490                                 ));
 491                             }
 492                         }
 493                         (None, _) => {
 494                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 495                             continue;
 496                         }
 497                         _ => {
 498                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 499                             continue;
 500                         }
 501                     }
 502                 }
 503                 _ => unreachable!(),
 504             }
 505         }
 506     }
 507
 508     // Merge the const-unstable info into the stability info
 509     if promotable {
 510         if let Some((ref mut stab, _)) = const_stab {
 511             stab.promotable = promotable;
 512         } else {
 513             struct_span_err!(
 514                 diagnostic,
 515                 item_sp,
 516                 E0717,
 517                 "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
 518                 or a `rustc_const_stable` attribute"
 519             )
 520             .emit();
 521         }
 522     }
 523
 524     if allowed_through_unstable_modules {
 525         if let Some((
 526             Stability {
 527                 level: StabilityLevel::Stable { ref mut allowed_through_unstable_modules, .. },
 528                 ..
 529             },
 530             _,
 531         )) = stab
 532         {
 533             *allowed_through_unstable_modules = true;
 534         } else {
 535             struct_span_err!(
 536                 diagnostic,
 537                 item_sp,
 538                 E0789,
 539                 "`rustc_allowed_through_unstable_modules` attribute must be paired with a `stable` attribute"
 540             )
 541             .emit();
 542         }
 543     }
 544
 545     (stab, const_stab)
 546 }
 547
 548 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 549     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 550 }
 551
 552 #[derive(Clone, Debug)]
 553 pub struct Condition {
 554     pub name: Symbol,
 555     pub name_span: Span,
 556     pub value: Option<Symbol>,
 557     pub value_span: Option<Span>,
 558     pub span: Span,
 559 }
 560
 561 /// Tests if a cfg-pattern matches the cfg set
 562 pub fn cfg_matches(
 563     cfg: &ast::MetaItem,
 564     sess: &ParseSess,
 565     lint_node_id: NodeId,
 566     features: Option<&Features>,
 567 ) -> bool {
 568     eval_condition(cfg, sess, features, &mut |cfg| {
 569         try_gate_cfg(cfg.name, cfg.span, sess, features);
 570         if let Some(names_valid) = &sess.check_config.names_valid {
 571             if !names_valid.contains(&cfg.name) {
 572                 sess.buffer_lint_with_diagnostic(
 573                     UNEXPECTED_CFGS,
 574                     cfg.span,
 575                     lint_node_id,
 576                     "unexpected `cfg` condition name",
 577                     BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
 578                 );
 579             }
 580         }
 581         if let Some(value) = cfg.value {
 582             if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
 583                 if !values.contains(&value) {
 584                     sess.buffer_lint_with_diagnostic(
 585                         UNEXPECTED_CFGS,
 586                         cfg.span,
 587                         lint_node_id,
 588                         "unexpected `cfg` condition value",
 589                         BuiltinLintDiagnostics::UnexpectedCfg(
 590                             (cfg.name, cfg.name_span),
 591                             cfg.value_span.map(|vs| (value, vs)),
 592                         ),
 593                     );
 594                 }
 595             }
 596         }
 597         sess.config.contains(&(cfg.name, cfg.value))
 598     })
 599 }
 600
 601 fn try_gate_cfg(name: Symbol, span: Span, sess: &ParseSess, features: Option<&Features>) {
 602     let gate = find_gated_cfg(|sym| sym == name);
 603     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 604         gate_cfg(&gated_cfg, span, sess, feats);
 605     }
 606 }
 607
 608 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 609     let (cfg, feature, has_feature) = gated_cfg;
 610     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 611         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 612         feature_err(sess, *feature, cfg_span, &explain).emit();
 613     }
 614 }
 615
 616 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 617 struct Version {
 618     major: u16,
 619     minor: u16,
 620     patch: u16,
 621 }
 622
 623 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 624     let mut components = s.split('-');
 625     let d = components.next()?;
 626     if !allow_appendix && components.next().is_some() {
 627         return None;
 628     }
 629     let mut digits = d.splitn(3, '.');
 630     let major = digits.next()?.parse().ok()?;
 631     let minor = digits.next()?.parse().ok()?;
 632     let patch = digits.next().unwrap_or("0").parse().ok()?;
 633     Some(Version { major, minor, patch })
 634 }
 635
 636 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 637 /// evaluate individual items.
 638 pub fn eval_condition(
 639     cfg: &ast::MetaItem,
 640     sess: &ParseSess,
 641     features: Option<&Features>,
 642     eval: &mut impl FnMut(Condition) -> bool,
 643 ) -> bool {
 644     match cfg.kind {
 645         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 646             try_gate_cfg(sym::version, cfg.span, sess, features);
 647             let (min_version, span) = match &mis[..] {
 648                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 649                     (sym, span)
 650                 }
 651                 [
 652                     NestedMetaItem::Literal(Lit { span, .. })
 653                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 654                 ] => {
 655                     sess.span_diagnostic
 656                         .struct_span_err(*span, "expected a version literal")
 657                         .emit();
 658                     return false;
 659                 }
 660                 [..] => {
 661                     sess.span_diagnostic
 662                         .struct_span_err(cfg.span, "expected single version literal")
 663                         .emit();
 664                     return false;
 665                 }
 666             };
 667             let Some(min_version) = parse_version(min_version.as_str(), false) else {
 668                 sess.span_diagnostic
 669                     .struct_span_warn(
 670                         *span,
 671                         "unknown version literal format, assuming it refers to a future version",
 672                     )
 673                     .emit();
 674                 return false;
 675             };
 676             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 677
 678             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 679             if sess.assume_incomplete_release {
 680                 rustc_version > min_version
 681             } else {
 682                 rustc_version >= min_version
 683             }
 684         }
 685         ast::MetaItemKind::List(ref mis) => {
 686             for mi in mis.iter() {
 687                 if !mi.is_meta_item() {
 688                     handle_errors(
 689                         sess,
 690                         mi.span(),
 691                         AttrError::UnsupportedLiteral("unsupported literal", false),
 692                     );
 693                     return false;
 694                 }
 695             }
 696
 697             // The unwraps below may look dangerous, but we've already asserted
 698             // that they won't fail with the loop above.
 699             match cfg.name_or_empty() {
 700                 sym::any => mis
 701                     .iter()
 702                     // We don't use any() here, because we want to evaluate all cfg condition
 703                     // as eval_condition can (and does) extra checks
 704                     .fold(false, |res, mi| {
 705                         res | eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 706                     }),
 707                 sym::all => mis
 708                     .iter()
 709                     // We don't use all() here, because we want to evaluate all cfg condition
 710                     // as eval_condition can (and does) extra checks
 711                     .fold(true, |res, mi| {
 712                         res & eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 713                     }),
 714                 sym::not => {
 715                     if mis.len() != 1 {
 716                         struct_span_err!(
 717                             sess.span_diagnostic,
 718                             cfg.span,
 719                             E0536,
 720                             "expected 1 cfg-pattern"
 721                         )
 722                         .emit();
 723                         return false;
 724                     }
 725
 726                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 727                 }
 728                 sym::target => {
 729                     if let Some(features) = features && !features.cfg_target_compact {
 730                         feature_err(
 731                             sess,
 732                             sym::cfg_target_compact,
 733                             cfg.span,
 734                             &"compact `cfg(target(..))` is experimental and subject to change"
 735                         ).emit();
 736                     }
 737
 738                     mis.iter().fold(true, |res, mi| {
 739                         let mut mi = mi.meta_item().unwrap().clone();
 740                         if let [seg, ..] = &mut mi.path.segments[..] {
 741                             seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
 742                         }
 743
 744                         res & eval_condition(&mi, sess, features, eval)
 745                     })
 746                 }
 747                 _ => {
 748                     struct_span_err!(
 749                         sess.span_diagnostic,
 750                         cfg.span,
 751                         E0537,
 752                         "invalid predicate `{}`",
 753                         pprust::path_to_string(&cfg.path)
 754                     )
 755                     .emit();
 756                     false
 757                 }
 758             }
 759         }
 760         ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
 761             sess.span_diagnostic
 762                 .span_err(cfg.path.span, "`cfg` predicate key must be an identifier");
 763             true
 764         }
 765         MetaItemKind::NameValue(ref lit) if !lit.kind.is_str() => {
 766             handle_errors(
 767                 sess,
 768                 lit.span,
 769                 AttrError::UnsupportedLiteral(
 770                     "literal in `cfg` predicate value must be a string",
 771                     lit.kind.is_bytestr(),
 772                 ),
 773             );
 774             true
 775         }
 776         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
 777             let ident = cfg.ident().expect("multi-segment cfg predicate");
 778             eval(Condition {
 779                 name: ident.name,
 780                 name_span: ident.span,
 781                 value: cfg.value_str(),
 782                 value_span: cfg.name_value_literal_span(),
 783                 span: cfg.span,
 784             })
 785         }
 786     }
 787 }
 788
 789 #[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 790 pub struct Deprecation {
 791     pub since: Option<Symbol>,
 792     /// The note to issue a reason.
 793     pub note: Option<Symbol>,
 794     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 795     ///
 796     /// This is currently unstable.
 797     pub suggestion: Option<Symbol>,
 798
 799     /// Whether to treat the since attribute as being a Rust version identifier
 800     /// (rather than an opaque string).
 801     pub is_since_rustc_version: bool,
 802 }
 803
 804 /// Finds the deprecation attribute. `None` if none exists.
 805 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 806     find_deprecation_generic(sess, attrs.iter())
 807 }
 808
 809 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 810 where
 811     I: Iterator<Item = &'a Attribute>,
 812 {
 813     let mut depr: Option<(Deprecation, Span)> = None;
 814     let diagnostic = &sess.parse_sess.span_diagnostic;
 815     let is_rustc = sess.features_untracked().staged_api;
 816
 817     'outer: for attr in attrs_iter {
 818         if !attr.has_name(sym::deprecated) {
 819             continue;
 820         }
 821
 822         let Some(meta) = attr.meta() else {
 823             continue;
 824         };
 825         let mut since = None;
 826         let mut note = None;
 827         let mut suggestion = None;
 828         match &meta.kind {
 829             MetaItemKind::Word => {}
 830             MetaItemKind::NameValue(..) => note = meta.value_str(),
 831             MetaItemKind::List(list) => {
 832                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 833                     if item.is_some() {
 834                         handle_errors(
 835                             &sess.parse_sess,
 836                             meta.span,
 837                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 838                         );
 839                         return false;
 840                     }
 841                     if let Some(v) = meta.value_str() {
 842                         *item = Some(v);
 843                         true
 844                     } else {
 845                         if let Some(lit) = meta.name_value_literal() {
 846                             handle_errors(
 847                                 &sess.parse_sess,
 848                                 lit.span,
 849                                 AttrError::UnsupportedLiteral(
 850                                     "literal in `deprecated` \
 851                                     value must be a string",
 852                                     lit.kind.is_bytestr(),
 853                                 ),
 854                             );
 855                         } else {
 856                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 857                                 .emit();
 858                         }
 859
 860                         false
 861                     }
 862                 };
 863
 864                 for meta in list {
 865                     match meta {
 866                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 867                             sym::since => {
 868                                 if !get(mi, &mut since) {
 869                                     continue 'outer;
 870                                 }
 871                             }
 872                             sym::note => {
 873                                 if !get(mi, &mut note) {
 874                                     continue 'outer;
 875                                 }
 876                             }
 877                             sym::suggestion => {
 878                                 if !sess.features_untracked().deprecated_suggestion {
 879                                     let mut diag = sess.struct_span_err(
 880                                         mi.span,
 881                                         "suggestions on deprecated items are unstable",
 882                                     );
 883                                     if sess.is_nightly_build() {
 884                                         diag.help("add `#![feature(deprecated_suggestion)]` to the crate root");
 885                                     }
 886                                     diag.note("see #94785 for more details").emit();
 887                                 }
 888
 889                                 if !get(mi, &mut suggestion) {
 890                                     continue 'outer;
 891                                 }
 892                             }
 893                             _ => {
 894                                 handle_errors(
 895                                     &sess.parse_sess,
 896                                     meta.span(),
 897                                     AttrError::UnknownMetaItem(
 898                                         pprust::path_to_string(&mi.path),
 899                                         if sess.features_untracked().deprecated_suggestion {
 900                                             &["since", "note", "suggestion"]
 901                                         } else {
 902                                             &["since", "note"]
 903                                         },
 904                                     ),
 905                                 );
 906                                 continue 'outer;
 907                             }
 908                         },
 909                         NestedMetaItem::Literal(lit) => {
 910                             handle_errors(
 911                                 &sess.parse_sess,
 912                                 lit.span,
 913                                 AttrError::UnsupportedLiteral(
 914                                     "item in `deprecated` must be a key/value pair",
 915                                     false,
 916                                 ),
 917                             );
 918                             continue 'outer;
 919                         }
 920                     }
 921                 }
 922             }
 923         }
 924
 925         if is_rustc {
 926             if since.is_none() {
 927                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 928                 continue;
 929             }
 930
 931             if note.is_none() {
 932                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'note'").emit();
 933                 continue;
 934             }
 935         }
 936
 937         depr = Some((
 938             Deprecation { since, note, suggestion, is_since_rustc_version: is_rustc },
 939             attr.span,
 940         ));
 941     }
 942
 943     depr
 944 }
 945
 946 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 947 pub enum ReprAttr {
 948     ReprInt(IntType),
 949     ReprC,
 950     ReprPacked(u32),
 951     ReprSimd,
 952     ReprTransparent,
 953     ReprAlign(u32),
 954 }
 955
 956 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 957 #[derive(Encodable, Decodable, HashStable_Generic)]
 958 pub enum IntType {
 959     SignedInt(ast::IntTy),
 960     UnsignedInt(ast::UintTy),
 961 }
 962
 963 impl IntType {
 964     #[inline]
 965     pub fn is_signed(self) -> bool {
 966         use IntType::*;
 967
 968         match self {
 969             SignedInt(..) => true,
 970             UnsignedInt(..) => false,
 971         }
 972     }
 973 }
 974
 975 /// Parse #[repr(...)] forms.
 976 ///
 977 /// Valid repr contents: any of the primitive integral type names (see
 978 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 979 /// the same discriminant size that the corresponding C enum would or C
 980 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 981 /// concerns to the only non-ZST field.
 982 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 983     if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
 984 }
 985
 986 pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 987     assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {:?}", attr);
 988     use ReprAttr::*;
 989     let mut acc = Vec::new();
 990     let diagnostic = &sess.parse_sess.span_diagnostic;
 991
 992     if let Some(items) = attr.meta_item_list() {
 993         for item in items {
 994             let mut recognised = false;
 995             if item.is_word() {
 996                 let hint = match item.name_or_empty() {
 997                     sym::C => Some(ReprC),
 998                     sym::packed => Some(ReprPacked(1)),
 999                     sym::simd => Some(ReprSimd),
1000                     sym::transparent => Some(ReprTransparent),
1001                     sym::align => {
1002                         let mut err = struct_span_err!(
1003                             diagnostic,
1004                             item.span(),
1005                             E0589,
1006                             "invalid `repr(align)` attribute: `align` needs an argument"
1007                         );
1008                         err.span_suggestion(
1009                             item.span(),
1010                             "supply an argument here",
1011                             "align(...)",
1012                             Applicability::HasPlaceholders,
1013                         );
1014                         err.emit();
1015                         recognised = true;
1016                         None
1017                     }
1018                     name => int_type_of_word(name).map(ReprInt),
1019                 };
1020
1021                 if let Some(h) = hint {
1022                     recognised = true;
1023                     acc.push(h);
1024                 }
1025             } else if let Some((name, value)) = item.name_value_literal() {
1026                 let mut literal_error = None;
1027                 if name == sym::align {
1028                     recognised = true;
1029                     match parse_alignment(&value.kind) {
1030                         Ok(literal) => acc.push(ReprAlign(literal)),
1031                         Err(message) => literal_error = Some(message),
1032                     };
1033                 } else if name == sym::packed {
1034                     recognised = true;
1035                     match parse_alignment(&value.kind) {
1036                         Ok(literal) => acc.push(ReprPacked(literal)),
1037                         Err(message) => literal_error = Some(message),
1038                     };
1039                 } else if matches!(name, sym::C | sym::simd | sym::transparent)
1040                     || int_type_of_word(name).is_some()
1041                 {
1042                     recognised = true;
1043                     struct_span_err!(
1044                                 diagnostic,
1045                                 item.span(),
1046                                 E0552,
1047                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
1048                                 name.to_ident_string(),
1049                             ).emit();
1050                 }
1051                 if let Some(literal_error) = literal_error {
1052                     struct_span_err!(
1053                         diagnostic,
1054                         item.span(),
1055                         E0589,
1056                         "invalid `repr({})` attribute: {}",
1057                         name.to_ident_string(),
1058                         literal_error
1059                     )
1060                     .emit();
1061                 }
1062             } else if let Some(meta_item) = item.meta_item() {
1063                 if let MetaItemKind::NameValue(ref value) = meta_item.kind {
1064                     if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
1065                         let name = meta_item.name_or_empty().to_ident_string();
1066                         recognised = true;
1067                         let mut err = struct_span_err!(
1068                             diagnostic,
1069                             item.span(),
1070                             E0693,
1071                             "incorrect `repr({})` attribute format",
1072                             name,
1073                         );
1074                         match value.kind {
1075                             ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
1076                                 err.span_suggestion(
1077                                     item.span(),
1078                                     "use parentheses instead",
1079                                     format!("{}({})", name, int),
1080                                     Applicability::MachineApplicable,
1081                                 );
1082                             }
1083                             ast::LitKind::Str(s, _) => {
1084                                 err.span_suggestion(
1085                                     item.span(),
1086                                     "use parentheses instead",
1087                                     format!("{}({})", name, s),
1088                                     Applicability::MachineApplicable,
1089                                 );
1090                             }
1091                             _ => {}
1092                         }
1093                         err.emit();
1094                     } else {
1095                         if matches!(
1096                             meta_item.name_or_empty(),
1097                             sym::C | sym::simd | sym::transparent
1098                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1099                         {
1100                             recognised = true;
1101                             struct_span_err!(
1102                                 diagnostic,
1103                                 meta_item.span,
1104                                 E0552,
1105                                 "invalid representation hint: `{}` does not take a value",
1106                                 meta_item.name_or_empty().to_ident_string(),
1107                             )
1108                             .emit();
1109                         }
1110                     }
1111                 } else if let MetaItemKind::List(_) = meta_item.kind {
1112                     if meta_item.has_name(sym::align) {
1113                         recognised = true;
1114                         struct_span_err!(
1115                             diagnostic,
1116                             meta_item.span,
1117                             E0693,
1118                             "incorrect `repr(align)` attribute format: \
1119                                  `align` takes exactly one argument in parentheses"
1120                         )
1121                         .emit();
1122                     } else if meta_item.has_name(sym::packed) {
1123                         recognised = true;
1124                         struct_span_err!(
1125                             diagnostic,
1126                             meta_item.span,
1127                             E0552,
1128                             "incorrect `repr(packed)` attribute format: \
1129                                  `packed` takes exactly one parenthesized argument, \
1130                                  or no parentheses at all"
1131                         )
1132                         .emit();
1133                     } else if matches!(
1134                         meta_item.name_or_empty(),
1135                         sym::C | sym::simd | sym::transparent
1136                     ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1137                     {
1138                         recognised = true;
1139                         struct_span_err!(
1140                                 diagnostic,
1141                                 meta_item.span,
1142                                 E0552,
1143                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
1144                                 meta_item.name_or_empty().to_ident_string(),
1145                             ).emit();
1146                     }
1147                 }
1148             }
1149             if !recognised {
1150                 // Not a word we recognize. This will be caught and reported by
1151                 // the `check_mod_attrs` pass, but this pass doesn't always run
1152                 // (e.g. if we only pretty-print the source), so we have to gate
1153                 // the `delay_span_bug` call as follows:
1154                 if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1155                     diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1156                 }
1157             }
1158         }
1159     }
1160     acc
1161 }
1162
1163 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1164     use IntType::*;
1165
1166     match s {
1167         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1168         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1169         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1170         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1171         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1172         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1173         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1174         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1175         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1176         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1177         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1178         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1179         _ => None,
1180     }
1181 }
1182
1183 pub enum TransparencyError {
1184     UnknownTransparency(Symbol, Span),
1185     MultipleTransparencyAttrs(Span, Span),
1186 }
1187
1188 pub fn find_transparency(
1189     attrs: &[Attribute],
1190     macro_rules: bool,
1191 ) -> (Transparency, Option<TransparencyError>) {
1192     let mut transparency = None;
1193     let mut error = None;
1194     for attr in attrs {
1195         if attr.has_name(sym::rustc_macro_transparency) {
1196             if let Some((_, old_span)) = transparency {
1197                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1198                 break;
1199             } else if let Some(value) = attr.value_str() {
1200                 transparency = Some((
1201                     match value {
1202                         sym::transparent => Transparency::Transparent,
1203                         sym::semitransparent => Transparency::SemiTransparent,
1204                         sym::opaque => Transparency::Opaque,
1205                         _ => {
1206                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1207                             continue;
1208                         }
1209                     },
1210                     attr.span,
1211                 ));
1212             }
1213         }
1214     }
1215     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1216     (transparency.map_or(fallback, |t| t.0), error)
1217 }
1218
1219 pub fn allow_internal_unstable<'a>(
1220     sess: &'a Session,
1221     attrs: &'a [Attribute],
1222 ) -> impl Iterator<Item = Symbol> + 'a {
1223     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1224 }
1225
1226 pub fn rustc_allow_const_fn_unstable<'a>(
1227     sess: &'a Session,
1228     attrs: &'a [Attribute],
1229 ) -> impl Iterator<Item = Symbol> + 'a {
1230     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1231 }
1232
1233 fn allow_unstable<'a>(
1234     sess: &'a Session,
1235     attrs: &'a [Attribute],
1236     symbol: Symbol,
1237 ) -> impl Iterator<Item = Symbol> + 'a {
1238     let attrs = sess.filter_by_name(attrs, symbol);
1239     let list = attrs
1240         .filter_map(move |attr| {
1241             attr.meta_item_list().or_else(|| {
1242                 sess.diagnostic().span_err(
1243                     attr.span,
1244                     &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
1245                 );
1246                 None
1247             })
1248         })
1249         .flatten();
1250
1251     list.into_iter().filter_map(move |it| {
1252         let name = it.ident().map(|ident| ident.name);
1253         if name.is_none() {
1254             sess.diagnostic().span_err(
1255                 it.span(),
1256                 &format!("`{}` expects feature names", symbol.to_ident_string()),
1257             );
1258         }
1259         name
1260     })
1261 }
1262
1263 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1264     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1265         if literal.is_power_of_two() {
1266             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1267             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1268         } else {
1269             Err("not a power of two")
1270         }
1271     } else {
1272         Err("not an unsuffixed integer")
1273     }
1274 }