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, LitKind, MetaItem, MetaItemKind, MetaItemLit, NestedMetaItem, NodeId};
   5 use rustc_ast_pretty::pprust;
   6 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
   7 use rustc_macros::HashStable_Generic;
   8 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
   9 use rustc_session::lint::BuiltinLintDiagnostics;
  10 use rustc_session::parse::{feature_err, ParseSess};
  11 use rustc_session::Session;
  12 use rustc_span::hygiene::Transparency;
  13 use rustc_span::{symbol::sym, symbol::Symbol, Span};
  14 use std::num::NonZeroU32;
  15
  16 use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
  17
  18 /// The version placeholder that recently stabilized features contain inside the
  19 /// `since` field of the `#[stable]` attribute.
  20 ///
  21 /// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
  22 pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
  23
  24 pub fn rust_version_symbol() -> Symbol {
  25     let version = option_env!("CFG_VERSION").unwrap_or("<current>");
  26     let version = version.split(' ').next().unwrap();
  27     Symbol::intern(&version)
  28 }
  29
  30 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  31     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  32 }
  33
  34 enum AttrError {
  35     MultipleItem(String),
  36     UnknownMetaItem(String, &'static [&'static str]),
  37     MissingSince,
  38     NonIdentFeature,
  39     MissingFeature,
  40     MultipleStabilityLevels,
  41     UnsupportedLiteral(UnsupportedLiteralReason, /* is_bytestr */ bool),
  42 }
  43
  44 pub(crate) enum UnsupportedLiteralReason {
  45     Generic,
  46     CfgString,
  47     DeprecatedString,
  48     DeprecatedKvPair,
  49 }
  50
  51 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
  52     match error {
  53         AttrError::MultipleItem(item) => {
  54             sess.emit_err(session_diagnostics::MultipleItem { span, item });
  55         }
  56         AttrError::UnknownMetaItem(item, expected) => {
  57             sess.emit_err(session_diagnostics::UnknownMetaItem { span, item, expected });
  58         }
  59         AttrError::MissingSince => {
  60             sess.emit_err(session_diagnostics::MissingSince { span });
  61         }
  62         AttrError::NonIdentFeature => {
  63             sess.emit_err(session_diagnostics::NonIdentFeature { span });
  64         }
  65         AttrError::MissingFeature => {
  66             sess.emit_err(session_diagnostics::MissingFeature { span });
  67         }
  68         AttrError::MultipleStabilityLevels => {
  69             sess.emit_err(session_diagnostics::MultipleStabilityLevels { span });
  70         }
  71         AttrError::UnsupportedLiteral(reason, is_bytestr) => {
  72             sess.emit_err(session_diagnostics::UnsupportedLiteral {
  73                 span,
  74                 reason,
  75                 is_bytestr,
  76                 start_point_span: sess.source_map().start_point(span),
  77             });
  78         }
  79     }
  80 }
  81
  82 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
  83 pub enum InlineAttr {
  84     None,
  85     Hint,
  86     Always,
  87     Never,
  88 }
  89
  90 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
  91 pub enum InstructionSetAttr {
  92     ArmA32,
  93     ArmT32,
  94 }
  95
  96 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
  97 pub enum OptimizeAttr {
  98     None,
  99     Speed,
 100     Size,
 101 }
 102
 103 /// Represents the following attributes:
 104 ///
 105 /// - `#[stable]`
 106 /// - `#[unstable]`
 107 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 108 #[derive(HashStable_Generic)]
 109 pub struct Stability {
 110     pub level: StabilityLevel,
 111     pub feature: Symbol,
 112 }
 113
 114 impl Stability {
 115     pub fn is_unstable(&self) -> bool {
 116         self.level.is_unstable()
 117     }
 118
 119     pub fn is_stable(&self) -> bool {
 120         self.level.is_stable()
 121     }
 122 }
 123
 124 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 125 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 126 #[derive(HashStable_Generic)]
 127 pub struct ConstStability {
 128     pub level: StabilityLevel,
 129     pub feature: Symbol,
 130     /// whether the function has a `#[rustc_promotable]` attribute
 131     pub promotable: bool,
 132 }
 133
 134 impl ConstStability {
 135     pub fn is_const_unstable(&self) -> bool {
 136         self.level.is_unstable()
 137     }
 138
 139     pub fn is_const_stable(&self) -> bool {
 140         self.level.is_stable()
 141     }
 142 }
 143
 144 /// Represents the `#[rustc_default_body_unstable]` attribute.
 145 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 146 #[derive(HashStable_Generic)]
 147 pub struct DefaultBodyStability {
 148     pub level: StabilityLevel,
 149     pub feature: Symbol,
 150 }
 151
 152 /// The available stability levels.
 153 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 154 #[derive(HashStable_Generic)]
 155 pub enum StabilityLevel {
 156     /// `#[unstable]`
 157     Unstable {
 158         /// Reason for the current stability level.
 159         reason: UnstableReason,
 160         /// Relevant `rust-lang/rust` issue.
 161         issue: Option<NonZeroU32>,
 162         is_soft: bool,
 163         /// If part of a feature is stabilized and a new feature is added for the remaining parts,
 164         /// then the `implied_by` attribute is used to indicate which now-stable feature previously
 165         /// contained a item.
 166         ///
 167         /// ```pseudo-Rust
 168         /// #[unstable(feature = "foo", issue = "...")]
 169         /// fn foo() {}
 170         /// #[unstable(feature = "foo", issue = "...")]
 171         /// fn foobar() {}
 172         /// ```
 173         ///
 174         /// ...becomes...
 175         ///
 176         /// ```pseudo-Rust
 177         /// #[stable(feature = "foo", since = "1.XX.X")]
 178         /// fn foo() {}
 179         /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
 180         /// fn foobar() {}
 181         /// ```
 182         implied_by: Option<Symbol>,
 183     },
 184     /// `#[stable]`
 185     Stable {
 186         /// Rust release which stabilized this feature.
 187         since: Symbol,
 188         /// Is this item allowed to be referred to on stable, despite being contained in unstable
 189         /// modules?
 190         allowed_through_unstable_modules: bool,
 191     },
 192 }
 193
 194 impl StabilityLevel {
 195     pub fn is_unstable(&self) -> bool {
 196         matches!(self, StabilityLevel::Unstable { .. })
 197     }
 198     pub fn is_stable(&self) -> bool {
 199         matches!(self, StabilityLevel::Stable { .. })
 200     }
 201 }
 202
 203 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 204 #[derive(HashStable_Generic)]
 205 pub enum UnstableReason {
 206     None,
 207     Default,
 208     Some(Symbol),
 209 }
 210
 211 impl UnstableReason {
 212     fn from_opt_reason(reason: Option<Symbol>) -> Self {
 213         // UnstableReason::Default constructed manually
 214         match reason {
 215             Some(r) => Self::Some(r),
 216             None => Self::None,
 217         }
 218     }
 219
 220     pub fn to_opt_reason(&self) -> Option<Symbol> {
 221         match self {
 222             Self::None => None,
 223             Self::Default => Some(sym::unstable_location_reason_default),
 224             Self::Some(r) => Some(*r),
 225         }
 226     }
 227 }
 228
 229 /// Collects stability info from all stability attributes in `attrs`.
 230 /// Returns `None` if no stability attributes are found.
 231 pub fn find_stability(
 232     sess: &Session,
 233     attrs: &[Attribute],
 234     item_sp: Span,
 235 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>, Option<(DefaultBodyStability, Span)>)
 236 {
 237     find_stability_generic(sess, attrs.iter(), item_sp)
 238 }
 239
 240 fn find_stability_generic<'a, I>(
 241     sess: &Session,
 242     attrs_iter: I,
 243     item_sp: Span,
 244 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>, Option<(DefaultBodyStability, Span)>)
 245 where
 246     I: Iterator<Item = &'a Attribute>,
 247 {
 248     use StabilityLevel::*;
 249
 250     let mut stab: Option<(Stability, Span)> = None;
 251     let mut const_stab: Option<(ConstStability, Span)> = None;
 252     let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
 253     let mut promotable = false;
 254     let mut allowed_through_unstable_modules = false;
 255
 256     'outer: for attr in attrs_iter {
 257         if ![
 258             sym::rustc_const_unstable,
 259             sym::rustc_const_stable,
 260             sym::unstable,
 261             sym::stable,
 262             sym::rustc_promotable,
 263             sym::rustc_allowed_through_unstable_modules,
 264             sym::rustc_default_body_unstable,
 265         ]
 266         .iter()
 267         .any(|&s| attr.has_name(s))
 268         {
 269             continue; // not a stability level
 270         }
 271
 272         let meta = attr.meta();
 273
 274         if attr.has_name(sym::rustc_promotable) {
 275             promotable = true;
 276         } else if attr.has_name(sym::rustc_allowed_through_unstable_modules) {
 277             allowed_through_unstable_modules = true;
 278         }
 279         // attributes with data
 280         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 281             let meta = meta.as_ref().unwrap();
 282             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 283                 if item.is_some() {
 284                     handle_errors(
 285                         &sess.parse_sess,
 286                         meta.span,
 287                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 288                     );
 289                     return false;
 290                 }
 291                 if let Some(v) = meta.value_str() {
 292                     *item = Some(v);
 293                     true
 294                 } else {
 295                     sess.emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
 296                     false
 297                 }
 298             };
 299
 300             let meta_name = meta.name_or_empty();
 301             match meta_name {
 302                 sym::rustc_const_unstable | sym::rustc_default_body_unstable | sym::unstable => {
 303                     if meta_name == sym::unstable && stab.is_some() {
 304                         handle_errors(
 305                             &sess.parse_sess,
 306                             attr.span,
 307                             AttrError::MultipleStabilityLevels,
 308                         );
 309                         break;
 310                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 311                         handle_errors(
 312                             &sess.parse_sess,
 313                             attr.span,
 314                             AttrError::MultipleStabilityLevels,
 315                         );
 316                         break;
 317                     } else if meta_name == sym::rustc_default_body_unstable && body_stab.is_some() {
 318                         handle_errors(
 319                             &sess.parse_sess,
 320                             attr.span,
 321                             AttrError::MultipleStabilityLevels,
 322                         );
 323                         break;
 324                     }
 325
 326                     let mut feature = None;
 327                     let mut reason = None;
 328                     let mut issue = None;
 329                     let mut issue_num = None;
 330                     let mut is_soft = false;
 331                     let mut implied_by = None;
 332                     for meta in metas {
 333                         let Some(mi) = meta.meta_item() else {
 334                             handle_errors(
 335                                 &sess.parse_sess,
 336                                 meta.span(),
 337                                 AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
 338                             );
 339                             continue 'outer;
 340                         };
 341                         match mi.name_or_empty() {
 342                             sym::feature => {
 343                                 if !get(mi, &mut feature) {
 344                                     continue 'outer;
 345                                 }
 346                             }
 347                             sym::reason => {
 348                                 if !get(mi, &mut reason) {
 349                                     continue 'outer;
 350                                 }
 351                             }
 352                             sym::issue => {
 353                                 if !get(mi, &mut issue) {
 354                                     continue 'outer;
 355                                 }
 356
 357                                 // These unwraps are safe because `get` ensures the meta item
 358                                 // is a name/value pair string literal.
 359                                 issue_num = match issue.unwrap().as_str() {
 360                                     "none" => None,
 361                                     issue => match issue.parse::<NonZeroU32>() {
 362                                         Ok(num) => Some(num),
 363                                         Err(err) => {
 364                                             sess.emit_err(
 365                                                 session_diagnostics::InvalidIssueString {
 366                                                     span: mi.span,
 367                                                     cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
 368                                                         mi.name_value_literal_span().unwrap(),
 369                                                         err.kind(),
 370                                                     ),
 371                                                 },
 372                                             );
 373                                             continue 'outer;
 374                                         }
 375                                     },
 376                                 };
 377                             }
 378                             sym::soft => {
 379                                 if !mi.is_word() {
 380                                     sess.emit_err(session_diagnostics::SoftNoArgs {
 381                                         span: mi.span,
 382                                     });
 383                                 }
 384                                 is_soft = true;
 385                             }
 386                             sym::implied_by => {
 387                                 if !get(mi, &mut implied_by) {
 388                                     continue 'outer;
 389                                 }
 390                             }
 391                             _ => {
 392                                 handle_errors(
 393                                     &sess.parse_sess,
 394                                     meta.span(),
 395                                     AttrError::UnknownMetaItem(
 396                                         pprust::path_to_string(&mi.path),
 397                                         &["feature", "reason", "issue", "soft"],
 398                                     ),
 399                                 );
 400                                 continue 'outer;
 401                             }
 402                         }
 403                     }
 404
 405                     match (feature, reason, issue) {
 406                         (Some(feature), reason, Some(_)) => {
 407                             if !rustc_lexer::is_ident(feature.as_str()) {
 408                                 handle_errors(
 409                                     &sess.parse_sess,
 410                                     attr.span,
 411                                     AttrError::NonIdentFeature,
 412                                 );
 413                                 continue;
 414                             }
 415                             let level = Unstable {
 416                                 reason: UnstableReason::from_opt_reason(reason),
 417                                 issue: issue_num,
 418                                 is_soft,
 419                                 implied_by,
 420                             };
 421                             if sym::unstable == meta_name {
 422                                 stab = Some((Stability { level, feature }, attr.span));
 423                             } else if sym::rustc_const_unstable == meta_name {
 424                                 const_stab = Some((
 425                                     ConstStability { level, feature, promotable: false },
 426                                     attr.span,
 427                                 ));
 428                             } else if sym::rustc_default_body_unstable == meta_name {
 429                                 body_stab =
 430                                     Some((DefaultBodyStability { level, feature }, attr.span));
 431                             } else {
 432                                 unreachable!("Unknown stability attribute {meta_name}");
 433                             }
 434                         }
 435                         (None, _, _) => {
 436                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 437                             continue;
 438                         }
 439                         _ => {
 440                             sess.emit_err(session_diagnostics::MissingIssue { span: attr.span });
 441                             continue;
 442                         }
 443                     }
 444                 }
 445                 sym::rustc_const_stable | sym::stable => {
 446                     if meta_name == sym::stable && stab.is_some() {
 447                         handle_errors(
 448                             &sess.parse_sess,
 449                             attr.span,
 450                             AttrError::MultipleStabilityLevels,
 451                         );
 452                         break;
 453                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 454                         handle_errors(
 455                             &sess.parse_sess,
 456                             attr.span,
 457                             AttrError::MultipleStabilityLevels,
 458                         );
 459                         break;
 460                     }
 461
 462                     let mut feature = None;
 463                     let mut since = None;
 464                     for meta in metas {
 465                         match meta {
 466                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 467                                 sym::feature => {
 468                                     if !get(mi, &mut feature) {
 469                                         continue 'outer;
 470                                     }
 471                                 }
 472                                 sym::since => {
 473                                     if !get(mi, &mut since) {
 474                                         continue 'outer;
 475                                     }
 476                                 }
 477                                 _ => {
 478                                     handle_errors(
 479                                         &sess.parse_sess,
 480                                         meta.span(),
 481                                         AttrError::UnknownMetaItem(
 482                                             pprust::path_to_string(&mi.path),
 483                                             &["feature", "since"],
 484                                         ),
 485                                     );
 486                                     continue 'outer;
 487                                 }
 488                             },
 489                             NestedMetaItem::Lit(lit) => {
 490                                 handle_errors(
 491                                     &sess.parse_sess,
 492                                     lit.span,
 493                                     AttrError::UnsupportedLiteral(
 494                                         UnsupportedLiteralReason::Generic,
 495                                         false,
 496                                     ),
 497                                 );
 498                                 continue 'outer;
 499                             }
 500                         }
 501                     }
 502
 503                     if let Some(s) = since && s.as_str() == VERSION_PLACEHOLDER {
 504                         since = Some(rust_version_symbol());
 505                     }
 506
 507                     match (feature, since) {
 508                         (Some(feature), Some(since)) => {
 509                             let level = Stable { since, allowed_through_unstable_modules: false };
 510                             if sym::stable == meta_name {
 511                                 stab = Some((Stability { level, feature }, attr.span));
 512                             } else {
 513                                 const_stab = Some((
 514                                     ConstStability { level, feature, promotable: false },
 515                                     attr.span,
 516                                 ));
 517                             }
 518                         }
 519                         (None, _) => {
 520                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 521                             continue;
 522                         }
 523                         _ => {
 524                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 525                             continue;
 526                         }
 527                     }
 528                 }
 529                 _ => unreachable!(),
 530             }
 531         }
 532     }
 533
 534     // Merge the const-unstable info into the stability info
 535     if promotable {
 536         if let Some((ref mut stab, _)) = const_stab {
 537             stab.promotable = promotable;
 538         } else {
 539             sess.emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp });
 540         }
 541     }
 542
 543     if allowed_through_unstable_modules {
 544         if let Some((
 545             Stability {
 546                 level: StabilityLevel::Stable { ref mut allowed_through_unstable_modules, .. },
 547                 ..
 548             },
 549             _,
 550         )) = stab
 551         {
 552             *allowed_through_unstable_modules = true;
 553         } else {
 554             sess.emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
 555         }
 556     }
 557
 558     (stab, const_stab, body_stab)
 559 }
 560
 561 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 562     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 563 }
 564
 565 #[derive(Clone, Debug)]
 566 pub struct Condition {
 567     pub name: Symbol,
 568     pub name_span: Span,
 569     pub value: Option<Symbol>,
 570     pub value_span: Option<Span>,
 571     pub span: Span,
 572 }
 573
 574 /// Tests if a cfg-pattern matches the cfg set
 575 pub fn cfg_matches(
 576     cfg: &ast::MetaItem,
 577     sess: &ParseSess,
 578     lint_node_id: NodeId,
 579     features: Option<&Features>,
 580 ) -> bool {
 581     eval_condition(cfg, sess, features, &mut |cfg| {
 582         try_gate_cfg(cfg.name, cfg.span, sess, features);
 583         if let Some(names_valid) = &sess.check_config.names_valid {
 584             if !names_valid.contains(&cfg.name) {
 585                 sess.buffer_lint_with_diagnostic(
 586                     UNEXPECTED_CFGS,
 587                     cfg.span,
 588                     lint_node_id,
 589                     "unexpected `cfg` condition name",
 590                     BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
 591                 );
 592             }
 593         }
 594         if let Some(value) = cfg.value {
 595             if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
 596                 if !values.contains(&value) {
 597                     sess.buffer_lint_with_diagnostic(
 598                         UNEXPECTED_CFGS,
 599                         cfg.span,
 600                         lint_node_id,
 601                         "unexpected `cfg` condition value",
 602                         BuiltinLintDiagnostics::UnexpectedCfg(
 603                             (cfg.name, cfg.name_span),
 604                             cfg.value_span.map(|vs| (value, vs)),
 605                         ),
 606                     );
 607                 }
 608             }
 609         }
 610         sess.config.contains(&(cfg.name, cfg.value))
 611     })
 612 }
 613
 614 fn try_gate_cfg(name: Symbol, span: Span, sess: &ParseSess, features: Option<&Features>) {
 615     let gate = find_gated_cfg(|sym| sym == name);
 616     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 617         gate_cfg(&gated_cfg, span, sess, feats);
 618     }
 619 }
 620
 621 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 622     let (cfg, feature, has_feature) = gated_cfg;
 623     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 624         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 625         feature_err(sess, *feature, cfg_span, &explain).emit();
 626     }
 627 }
 628
 629 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 630 struct Version {
 631     major: u16,
 632     minor: u16,
 633     patch: u16,
 634 }
 635
 636 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 637     let mut components = s.split('-');
 638     let d = components.next()?;
 639     if !allow_appendix && components.next().is_some() {
 640         return None;
 641     }
 642     let mut digits = d.splitn(3, '.');
 643     let major = digits.next()?.parse().ok()?;
 644     let minor = digits.next()?.parse().ok()?;
 645     let patch = digits.next().unwrap_or("0").parse().ok()?;
 646     Some(Version { major, minor, patch })
 647 }
 648
 649 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 650 /// evaluate individual items.
 651 pub fn eval_condition(
 652     cfg: &ast::MetaItem,
 653     sess: &ParseSess,
 654     features: Option<&Features>,
 655     eval: &mut impl FnMut(Condition) -> bool,
 656 ) -> bool {
 657     match cfg.kind {
 658         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 659             try_gate_cfg(sym::version, cfg.span, sess, features);
 660             let (min_version, span) = match &mis[..] {
 661                 [NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
 662                     (sym, span)
 663                 }
 664                 [
 665                     NestedMetaItem::Lit(MetaItemLit { span, .. })
 666                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 667                 ] => {
 668                     sess.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
 669                     return false;
 670                 }
 671                 [..] => {
 672                     sess.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
 673                         span: cfg.span,
 674                     });
 675                     return false;
 676                 }
 677             };
 678             let Some(min_version) = parse_version(min_version.as_str(), false) else {
 679                 sess.emit_warning(session_diagnostics::UnknownVersionLiteral { span: *span });
 680                 return false;
 681             };
 682             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 683
 684             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 685             if sess.assume_incomplete_release {
 686                 rustc_version > min_version
 687             } else {
 688                 rustc_version >= min_version
 689             }
 690         }
 691         ast::MetaItemKind::List(ref mis) => {
 692             for mi in mis.iter() {
 693                 if !mi.is_meta_item() {
 694                     handle_errors(
 695                         sess,
 696                         mi.span(),
 697                         AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
 698                     );
 699                     return false;
 700                 }
 701             }
 702
 703             // The unwraps below may look dangerous, but we've already asserted
 704             // that they won't fail with the loop above.
 705             match cfg.name_or_empty() {
 706                 sym::any => mis
 707                     .iter()
 708                     // We don't use any() here, because we want to evaluate all cfg condition
 709                     // as eval_condition can (and does) extra checks
 710                     .fold(false, |res, mi| {
 711                         res | eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 712                     }),
 713                 sym::all => mis
 714                     .iter()
 715                     // We don't use all() here, because we want to evaluate all cfg condition
 716                     // as eval_condition can (and does) extra checks
 717                     .fold(true, |res, mi| {
 718                         res & eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 719                     }),
 720                 sym::not => {
 721                     if mis.len() != 1 {
 722                         sess.emit_err(session_diagnostics::ExpectedOneCfgPattern {
 723                             span: cfg.span,
 724                         });
 725                         return false;
 726                     }
 727
 728                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 729                 }
 730                 sym::target => {
 731                     if let Some(features) = features && !features.cfg_target_compact {
 732                         feature_err(
 733                             sess,
 734                             sym::cfg_target_compact,
 735                             cfg.span,
 736                             &"compact `cfg(target(..))` is experimental and subject to change"
 737                         ).emit();
 738                     }
 739
 740                     mis.iter().fold(true, |res, mi| {
 741                         let mut mi = mi.meta_item().unwrap().clone();
 742                         if let [seg, ..] = &mut mi.path.segments[..] {
 743                             seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
 744                         }
 745
 746                         res & eval_condition(&mi, sess, features, eval)
 747                     })
 748                 }
 749                 _ => {
 750                     sess.emit_err(session_diagnostics::InvalidPredicate {
 751                         span: cfg.span,
 752                         predicate: pprust::path_to_string(&cfg.path),
 753                     });
 754                     false
 755                 }
 756             }
 757         }
 758         ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
 759             sess.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
 760             true
 761         }
 762         MetaItemKind::NameValue(ref lit) if !lit.kind.is_str() => {
 763             handle_errors(
 764                 sess,
 765                 lit.span,
 766                 AttrError::UnsupportedLiteral(
 767                     UnsupportedLiteralReason::CfgString,
 768                     lit.kind.is_bytestr(),
 769                 ),
 770             );
 771             true
 772         }
 773         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
 774             let ident = cfg.ident().expect("multi-segment cfg predicate");
 775             eval(Condition {
 776                 name: ident.name,
 777                 name_span: ident.span,
 778                 value: cfg.value_str(),
 779                 value_span: cfg.name_value_literal_span(),
 780                 span: cfg.span,
 781             })
 782         }
 783     }
 784 }
 785
 786 #[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 787 pub struct Deprecation {
 788     pub since: Option<Symbol>,
 789     /// The note to issue a reason.
 790     pub note: Option<Symbol>,
 791     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 792     ///
 793     /// This is currently unstable.
 794     pub suggestion: Option<Symbol>,
 795
 796     /// Whether to treat the since attribute as being a Rust version identifier
 797     /// (rather than an opaque string).
 798     pub is_since_rustc_version: bool,
 799 }
 800
 801 /// Finds the deprecation attribute. `None` if none exists.
 802 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 803     find_deprecation_generic(sess, attrs.iter())
 804 }
 805
 806 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 807 where
 808     I: Iterator<Item = &'a Attribute>,
 809 {
 810     let mut depr: Option<(Deprecation, Span)> = None;
 811     let is_rustc = sess.features_untracked().staged_api;
 812
 813     'outer: for attr in attrs_iter {
 814         if !attr.has_name(sym::deprecated) {
 815             continue;
 816         }
 817
 818         let Some(meta) = attr.meta() else {
 819             continue;
 820         };
 821         let mut since = None;
 822         let mut note = None;
 823         let mut suggestion = None;
 824         match &meta.kind {
 825             MetaItemKind::Word => {}
 826             MetaItemKind::NameValue(..) => note = meta.value_str(),
 827             MetaItemKind::List(list) => {
 828                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 829                     if item.is_some() {
 830                         handle_errors(
 831                             &sess.parse_sess,
 832                             meta.span,
 833                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 834                         );
 835                         return false;
 836                     }
 837                     if let Some(v) = meta.value_str() {
 838                         *item = Some(v);
 839                         true
 840                     } else {
 841                         if let Some(lit) = meta.name_value_literal() {
 842                             handle_errors(
 843                                 &sess.parse_sess,
 844                                 lit.span,
 845                                 AttrError::UnsupportedLiteral(
 846                                     UnsupportedLiteralReason::DeprecatedString,
 847                                     lit.kind.is_bytestr(),
 848                                 ),
 849                             );
 850                         } else {
 851                             sess.emit_err(session_diagnostics::IncorrectMetaItem2 {
 852                                 span: meta.span,
 853                             });
 854                         }
 855
 856                         false
 857                     }
 858                 };
 859
 860                 for meta in list {
 861                     match meta {
 862                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 863                             sym::since => {
 864                                 if !get(mi, &mut since) {
 865                                     continue 'outer;
 866                                 }
 867                             }
 868                             sym::note => {
 869                                 if !get(mi, &mut note) {
 870                                     continue 'outer;
 871                                 }
 872                             }
 873                             sym::suggestion => {
 874                                 if !sess.features_untracked().deprecated_suggestion {
 875                                     sess.emit_err(session_diagnostics::DeprecatedItemSuggestion {
 876                                         span: mi.span,
 877                                         is_nightly: sess.is_nightly_build().then_some(()),
 878                                         details: (),
 879                                     });
 880                                 }
 881
 882                                 if !get(mi, &mut suggestion) {
 883                                     continue 'outer;
 884                                 }
 885                             }
 886                             _ => {
 887                                 handle_errors(
 888                                     &sess.parse_sess,
 889                                     meta.span(),
 890                                     AttrError::UnknownMetaItem(
 891                                         pprust::path_to_string(&mi.path),
 892                                         if sess.features_untracked().deprecated_suggestion {
 893                                             &["since", "note", "suggestion"]
 894                                         } else {
 895                                             &["since", "note"]
 896                                         },
 897                                     ),
 898                                 );
 899                                 continue 'outer;
 900                             }
 901                         },
 902                         NestedMetaItem::Lit(lit) => {
 903                             handle_errors(
 904                                 &sess.parse_sess,
 905                                 lit.span,
 906                                 AttrError::UnsupportedLiteral(
 907                                     UnsupportedLiteralReason::DeprecatedKvPair,
 908                                     false,
 909                                 ),
 910                             );
 911                             continue 'outer;
 912                         }
 913                     }
 914                 }
 915             }
 916         }
 917
 918         if is_rustc {
 919             if since.is_none() {
 920                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 921                 continue;
 922             }
 923
 924             if note.is_none() {
 925                 sess.emit_err(session_diagnostics::MissingNote { span: attr.span });
 926                 continue;
 927             }
 928         }
 929
 930         depr = Some((
 931             Deprecation { since, note, suggestion, is_since_rustc_version: is_rustc },
 932             attr.span,
 933         ));
 934     }
 935
 936     depr
 937 }
 938
 939 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 940 pub enum ReprAttr {
 941     ReprInt(IntType),
 942     ReprC,
 943     ReprPacked(u32),
 944     ReprSimd,
 945     ReprTransparent,
 946     ReprAlign(u32),
 947 }
 948
 949 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 950 #[derive(Encodable, Decodable, HashStable_Generic)]
 951 pub enum IntType {
 952     SignedInt(ast::IntTy),
 953     UnsignedInt(ast::UintTy),
 954 }
 955
 956 impl IntType {
 957     #[inline]
 958     pub fn is_signed(self) -> bool {
 959         use IntType::*;
 960
 961         match self {
 962             SignedInt(..) => true,
 963             UnsignedInt(..) => false,
 964         }
 965     }
 966 }
 967
 968 /// Parse #[repr(...)] forms.
 969 ///
 970 /// Valid repr contents: any of the primitive integral type names (see
 971 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 972 /// the same discriminant size that the corresponding C enum would or C
 973 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 974 /// concerns to the only non-ZST field.
 975 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 976     if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
 977 }
 978
 979 pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 980     assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {:?}", attr);
 981     use ReprAttr::*;
 982     let mut acc = Vec::new();
 983     let diagnostic = &sess.parse_sess.span_diagnostic;
 984
 985     if let Some(items) = attr.meta_item_list() {
 986         for item in items {
 987             let mut recognised = false;
 988             if item.is_word() {
 989                 let hint = match item.name_or_empty() {
 990                     sym::C => Some(ReprC),
 991                     sym::packed => Some(ReprPacked(1)),
 992                     sym::simd => Some(ReprSimd),
 993                     sym::transparent => Some(ReprTransparent),
 994                     sym::align => {
 995                         sess.emit_err(session_diagnostics::InvalidReprAlignNeedArg {
 996                             span: item.span(),
 997                         });
 998                         recognised = true;
 999                         None
1000                     }
1001                     name => int_type_of_word(name).map(ReprInt),
1002                 };
1003
1004                 if let Some(h) = hint {
1005                     recognised = true;
1006                     acc.push(h);
1007                 }
1008             } else if let Some((name, value)) = item.name_value_literal() {
1009                 let mut literal_error = None;
1010                 if name == sym::align {
1011                     recognised = true;
1012                     match parse_alignment(&value.kind) {
1013                         Ok(literal) => acc.push(ReprAlign(literal)),
1014                         Err(message) => literal_error = Some(message),
1015                     };
1016                 } else if name == sym::packed {
1017                     recognised = true;
1018                     match parse_alignment(&value.kind) {
1019                         Ok(literal) => acc.push(ReprPacked(literal)),
1020                         Err(message) => literal_error = Some(message),
1021                     };
1022                 } else if matches!(name, sym::C | sym::simd | sym::transparent)
1023                     || int_type_of_word(name).is_some()
1024                 {
1025                     recognised = true;
1026                     sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
1027                         span: item.span(),
1028                         name: name.to_ident_string(),
1029                     });
1030                 }
1031                 if let Some(literal_error) = literal_error {
1032                     sess.emit_err(session_diagnostics::InvalidReprGeneric {
1033                         span: item.span(),
1034                         repr_arg: name.to_ident_string(),
1035                         error_part: literal_error,
1036                     });
1037                 }
1038             } else if let Some(meta_item) = item.meta_item() {
1039                 if let MetaItemKind::NameValue(ref value) = meta_item.kind {
1040                     if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
1041                         let name = meta_item.name_or_empty().to_ident_string();
1042                         recognised = true;
1043                         sess.emit_err(session_diagnostics::IncorrectReprFormatGeneric {
1044                             span: item.span(),
1045                             repr_arg: &name,
1046                             cause: IncorrectReprFormatGenericCause::from_lit_kind(
1047                                 item.span(),
1048                                 &value.kind,
1049                                 &name,
1050                             ),
1051                         });
1052                     } else if matches!(
1053                         meta_item.name_or_empty(),
1054                         sym::C | sym::simd | sym::transparent
1055                     ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1056                     {
1057                         recognised = true;
1058                         sess.emit_err(session_diagnostics::InvalidReprHintNoValue {
1059                             span: meta_item.span,
1060                             name: meta_item.name_or_empty().to_ident_string(),
1061                         });
1062                     }
1063                 } else if let MetaItemKind::List(_) = meta_item.kind {
1064                     if meta_item.has_name(sym::align) {
1065                         recognised = true;
1066                         sess.emit_err(session_diagnostics::IncorrectReprFormatAlignOneArg {
1067                             span: meta_item.span,
1068                         });
1069                     } else if meta_item.has_name(sym::packed) {
1070                         recognised = true;
1071                         sess.emit_err(session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
1072                             span: meta_item.span,
1073                         });
1074                     } else if matches!(
1075                         meta_item.name_or_empty(),
1076                         sym::C | sym::simd | sym::transparent
1077                     ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1078                     {
1079                         recognised = true;
1080                         sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
1081                             span: meta_item.span,
1082                             name: meta_item.name_or_empty().to_ident_string(),
1083                         });
1084                     }
1085                 }
1086             }
1087             if !recognised {
1088                 // Not a word we recognize. This will be caught and reported by
1089                 // the `check_mod_attrs` pass, but this pass doesn't always run
1090                 // (e.g. if we only pretty-print the source), so we have to gate
1091                 // the `delay_span_bug` call as follows:
1092                 if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1093                     diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1094                 }
1095             }
1096         }
1097     }
1098     acc
1099 }
1100
1101 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1102     use IntType::*;
1103
1104     match s {
1105         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1106         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1107         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1108         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1109         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1110         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1111         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1112         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1113         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1114         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1115         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1116         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1117         _ => None,
1118     }
1119 }
1120
1121 pub enum TransparencyError {
1122     UnknownTransparency(Symbol, Span),
1123     MultipleTransparencyAttrs(Span, Span),
1124 }
1125
1126 pub fn find_transparency(
1127     attrs: &[Attribute],
1128     macro_rules: bool,
1129 ) -> (Transparency, Option<TransparencyError>) {
1130     let mut transparency = None;
1131     let mut error = None;
1132     for attr in attrs {
1133         if attr.has_name(sym::rustc_macro_transparency) {
1134             if let Some((_, old_span)) = transparency {
1135                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1136                 break;
1137             } else if let Some(value) = attr.value_str() {
1138                 transparency = Some((
1139                     match value {
1140                         sym::transparent => Transparency::Transparent,
1141                         sym::semitransparent => Transparency::SemiTransparent,
1142                         sym::opaque => Transparency::Opaque,
1143                         _ => {
1144                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1145                             continue;
1146                         }
1147                     },
1148                     attr.span,
1149                 ));
1150             }
1151         }
1152     }
1153     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1154     (transparency.map_or(fallback, |t| t.0), error)
1155 }
1156
1157 pub fn allow_internal_unstable<'a>(
1158     sess: &'a Session,
1159     attrs: &'a [Attribute],
1160 ) -> impl Iterator<Item = Symbol> + 'a {
1161     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1162 }
1163
1164 pub fn rustc_allow_const_fn_unstable<'a>(
1165     sess: &'a Session,
1166     attrs: &'a [Attribute],
1167 ) -> impl Iterator<Item = Symbol> + 'a {
1168     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1169 }
1170
1171 fn allow_unstable<'a>(
1172     sess: &'a Session,
1173     attrs: &'a [Attribute],
1174     symbol: Symbol,
1175 ) -> impl Iterator<Item = Symbol> + 'a {
1176     let attrs = sess.filter_by_name(attrs, symbol);
1177     let list = attrs
1178         .filter_map(move |attr| {
1179             attr.meta_item_list().or_else(|| {
1180                 sess.emit_err(session_diagnostics::ExpectsFeatureList {
1181                     span: attr.span,
1182                     name: symbol.to_ident_string(),
1183                 });
1184                 None
1185             })
1186         })
1187         .flatten();
1188
1189     list.into_iter().filter_map(move |it| {
1190         let name = it.ident().map(|ident| ident.name);
1191         if name.is_none() {
1192             sess.emit_err(session_diagnostics::ExpectsFeatures {
1193                 span: it.span(),
1194                 name: symbol.to_ident_string(),
1195             });
1196         }
1197         name
1198     })
1199 }
1200
1201 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1202     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1203         if literal.is_power_of_two() {
1204             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1205             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1206         } else {
1207             Err("not a power of two")
1208         }
1209     } else {
1210         Err("not an unsuffixed integer")
1211     }
1212 }