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(meta @ MetaItem { kind: MetaItemKind::List(metas), .. }) = &meta {
 281             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 282                 if item.is_some() {
 283                     handle_errors(
 284                         &sess.parse_sess,
 285                         meta.span,
 286                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 287                     );
 288                     return false;
 289                 }
 290                 if let Some(v) = meta.value_str() {
 291                     *item = Some(v);
 292                     true
 293                 } else {
 294                     sess.emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
 295                     false
 296                 }
 297             };
 298
 299             let meta_name = meta.name_or_empty();
 300             match meta_name {
 301                 sym::rustc_const_unstable | sym::rustc_default_body_unstable | sym::unstable => {
 302                     if meta_name == sym::unstable && stab.is_some() {
 303                         handle_errors(
 304                             &sess.parse_sess,
 305                             attr.span,
 306                             AttrError::MultipleStabilityLevels,
 307                         );
 308                         break;
 309                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 310                         handle_errors(
 311                             &sess.parse_sess,
 312                             attr.span,
 313                             AttrError::MultipleStabilityLevels,
 314                         );
 315                         break;
 316                     } else if meta_name == sym::rustc_default_body_unstable && body_stab.is_some() {
 317                         handle_errors(
 318                             &sess.parse_sess,
 319                             attr.span,
 320                             AttrError::MultipleStabilityLevels,
 321                         );
 322                         break;
 323                     }
 324
 325                     let mut feature = None;
 326                     let mut reason = None;
 327                     let mut issue = None;
 328                     let mut issue_num = None;
 329                     let mut is_soft = false;
 330                     let mut implied_by = None;
 331                     for meta in metas {
 332                         let Some(mi) = meta.meta_item() else {
 333                             handle_errors(
 334                                 &sess.parse_sess,
 335                                 meta.span(),
 336                                 AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
 337                             );
 338                             continue 'outer;
 339                         };
 340                         match mi.name_or_empty() {
 341                             sym::feature => {
 342                                 if !get(mi, &mut feature) {
 343                                     continue 'outer;
 344                                 }
 345                             }
 346                             sym::reason => {
 347                                 if !get(mi, &mut reason) {
 348                                     continue 'outer;
 349                                 }
 350                             }
 351                             sym::issue => {
 352                                 if !get(mi, &mut issue) {
 353                                     continue 'outer;
 354                                 }
 355
 356                                 // These unwraps are safe because `get` ensures the meta item
 357                                 // is a name/value pair string literal.
 358                                 issue_num = match issue.unwrap().as_str() {
 359                                     "none" => None,
 360                                     issue => match issue.parse::<NonZeroU32>() {
 361                                         Ok(num) => Some(num),
 362                                         Err(err) => {
 363                                             sess.emit_err(
 364                                                 session_diagnostics::InvalidIssueString {
 365                                                     span: mi.span,
 366                                                     cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
 367                                                         mi.name_value_literal_span().unwrap(),
 368                                                         err.kind(),
 369                                                     ),
 370                                                 },
 371                                             );
 372                                             continue 'outer;
 373                                         }
 374                                     },
 375                                 };
 376                             }
 377                             sym::soft => {
 378                                 if !mi.is_word() {
 379                                     sess.emit_err(session_diagnostics::SoftNoArgs {
 380                                         span: mi.span,
 381                                     });
 382                                 }
 383                                 is_soft = true;
 384                             }
 385                             sym::implied_by => {
 386                                 if !get(mi, &mut implied_by) {
 387                                     continue 'outer;
 388                                 }
 389                             }
 390                             _ => {
 391                                 handle_errors(
 392                                     &sess.parse_sess,
 393                                     meta.span(),
 394                                     AttrError::UnknownMetaItem(
 395                                         pprust::path_to_string(&mi.path),
 396                                         &["feature", "reason", "issue", "soft"],
 397                                     ),
 398                                 );
 399                                 continue 'outer;
 400                             }
 401                         }
 402                     }
 403
 404                     match (feature, reason, issue) {
 405                         (Some(feature), reason, Some(_)) => {
 406                             if !rustc_lexer::is_ident(feature.as_str()) {
 407                                 handle_errors(
 408                                     &sess.parse_sess,
 409                                     attr.span,
 410                                     AttrError::NonIdentFeature,
 411                                 );
 412                                 continue;
 413                             }
 414                             let level = Unstable {
 415                                 reason: UnstableReason::from_opt_reason(reason),
 416                                 issue: issue_num,
 417                                 is_soft,
 418                                 implied_by,
 419                             };
 420                             if sym::unstable == meta_name {
 421                                 stab = Some((Stability { level, feature }, attr.span));
 422                             } else if sym::rustc_const_unstable == meta_name {
 423                                 const_stab = Some((
 424                                     ConstStability { level, feature, promotable: false },
 425                                     attr.span,
 426                                 ));
 427                             } else if sym::rustc_default_body_unstable == meta_name {
 428                                 body_stab =
 429                                     Some((DefaultBodyStability { level, feature }, attr.span));
 430                             } else {
 431                                 unreachable!("Unknown stability attribute {meta_name}");
 432                             }
 433                         }
 434                         (None, _, _) => {
 435                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 436                             continue;
 437                         }
 438                         _ => {
 439                             sess.emit_err(session_diagnostics::MissingIssue { span: attr.span });
 440                             continue;
 441                         }
 442                     }
 443                 }
 444                 sym::rustc_const_stable | sym::stable => {
 445                     if meta_name == sym::stable && stab.is_some() {
 446                         handle_errors(
 447                             &sess.parse_sess,
 448                             attr.span,
 449                             AttrError::MultipleStabilityLevels,
 450                         );
 451                         break;
 452                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 453                         handle_errors(
 454                             &sess.parse_sess,
 455                             attr.span,
 456                             AttrError::MultipleStabilityLevels,
 457                         );
 458                         break;
 459                     }
 460
 461                     let mut feature = None;
 462                     let mut since = None;
 463                     for meta in metas {
 464                         match meta {
 465                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 466                                 sym::feature => {
 467                                     if !get(mi, &mut feature) {
 468                                         continue 'outer;
 469                                     }
 470                                 }
 471                                 sym::since => {
 472                                     if !get(mi, &mut since) {
 473                                         continue 'outer;
 474                                     }
 475                                 }
 476                                 _ => {
 477                                     handle_errors(
 478                                         &sess.parse_sess,
 479                                         meta.span(),
 480                                         AttrError::UnknownMetaItem(
 481                                             pprust::path_to_string(&mi.path),
 482                                             &["feature", "since"],
 483                                         ),
 484                                     );
 485                                     continue 'outer;
 486                                 }
 487                             },
 488                             NestedMetaItem::Lit(lit) => {
 489                                 handle_errors(
 490                                     &sess.parse_sess,
 491                                     lit.span,
 492                                     AttrError::UnsupportedLiteral(
 493                                         UnsupportedLiteralReason::Generic,
 494                                         false,
 495                                     ),
 496                                 );
 497                                 continue 'outer;
 498                             }
 499                         }
 500                     }
 501
 502                     if let Some(s) = since && s.as_str() == VERSION_PLACEHOLDER {
 503                         since = Some(rust_version_symbol());
 504                     }
 505
 506                     match (feature, since) {
 507                         (Some(feature), Some(since)) => {
 508                             let level = Stable { since, allowed_through_unstable_modules: false };
 509                             if sym::stable == meta_name {
 510                                 stab = Some((Stability { level, feature }, attr.span));
 511                             } else {
 512                                 const_stab = Some((
 513                                     ConstStability { level, feature, promotable: false },
 514                                     attr.span,
 515                                 ));
 516                             }
 517                         }
 518                         (None, _) => {
 519                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 520                             continue;
 521                         }
 522                         _ => {
 523                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 524                             continue;
 525                         }
 526                     }
 527                 }
 528                 _ => unreachable!(),
 529             }
 530         }
 531     }
 532
 533     // Merge the const-unstable info into the stability info
 534     if promotable {
 535         match &mut const_stab {
 536             Some((stab, _)) => stab.promotable = promotable,
 537             _ => _ = sess.emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp }),
 538         }
 539     }
 540
 541     if allowed_through_unstable_modules {
 542         match &mut stab {
 543             Some((
 544                 Stability {
 545                     level: StabilityLevel::Stable { allowed_through_unstable_modules, .. },
 546                     ..
 547                 },
 548                 _,
 549             )) => *allowed_through_unstable_modules = true,
 550             _ => {
 551                 sess.emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
 552             }
 553         }
 554     }
 555
 556     (stab, const_stab, body_stab)
 557 }
 558
 559 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 560     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 561 }
 562
 563 #[derive(Clone, Debug)]
 564 pub struct Condition {
 565     pub name: Symbol,
 566     pub name_span: Span,
 567     pub value: Option<Symbol>,
 568     pub value_span: Option<Span>,
 569     pub span: Span,
 570 }
 571
 572 /// Tests if a cfg-pattern matches the cfg set
 573 pub fn cfg_matches(
 574     cfg: &ast::MetaItem,
 575     sess: &ParseSess,
 576     lint_node_id: NodeId,
 577     features: Option<&Features>,
 578 ) -> bool {
 579     eval_condition(cfg, sess, features, &mut |cfg| {
 580         try_gate_cfg(cfg.name, cfg.span, sess, features);
 581         if let Some(names_valid) = &sess.check_config.names_valid {
 582             if !names_valid.contains(&cfg.name) {
 583                 sess.buffer_lint_with_diagnostic(
 584                     UNEXPECTED_CFGS,
 585                     cfg.span,
 586                     lint_node_id,
 587                     "unexpected `cfg` condition name",
 588                     BuiltinLintDiagnostics::UnexpectedCfg((cfg.name, cfg.name_span), None),
 589                 );
 590             }
 591         }
 592         if let Some(value) = cfg.value {
 593             if let Some(values) = &sess.check_config.values_valid.get(&cfg.name) {
 594                 if !values.contains(&value) {
 595                     sess.buffer_lint_with_diagnostic(
 596                         UNEXPECTED_CFGS,
 597                         cfg.span,
 598                         lint_node_id,
 599                         "unexpected `cfg` condition value",
 600                         BuiltinLintDiagnostics::UnexpectedCfg(
 601                             (cfg.name, cfg.name_span),
 602                             cfg.value_span.map(|vs| (value, vs)),
 603                         ),
 604                     );
 605                 }
 606             }
 607         }
 608         sess.config.contains(&(cfg.name, cfg.value))
 609     })
 610 }
 611
 612 fn try_gate_cfg(name: Symbol, span: Span, sess: &ParseSess, features: Option<&Features>) {
 613     let gate = find_gated_cfg(|sym| sym == name);
 614     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 615         gate_cfg(&gated_cfg, span, sess, feats);
 616     }
 617 }
 618
 619 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 620     let (cfg, feature, has_feature) = gated_cfg;
 621     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 622         let explain = format!("`cfg({cfg})` is experimental and subject to change");
 623         feature_err(sess, *feature, cfg_span, &explain).emit();
 624     }
 625 }
 626
 627 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 628 struct Version {
 629     major: u16,
 630     minor: u16,
 631     patch: u16,
 632 }
 633
 634 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 635     let mut components = s.split('-');
 636     let d = components.next()?;
 637     if !allow_appendix && components.next().is_some() {
 638         return None;
 639     }
 640     let mut digits = d.splitn(3, '.');
 641     let major = digits.next()?.parse().ok()?;
 642     let minor = digits.next()?.parse().ok()?;
 643     let patch = digits.next().unwrap_or("0").parse().ok()?;
 644     Some(Version { major, minor, patch })
 645 }
 646
 647 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 648 /// evaluate individual items.
 649 pub fn eval_condition(
 650     cfg: &ast::MetaItem,
 651     sess: &ParseSess,
 652     features: Option<&Features>,
 653     eval: &mut impl FnMut(Condition) -> bool,
 654 ) -> bool {
 655     match &cfg.kind {
 656         ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
 657             try_gate_cfg(sym::version, cfg.span, sess, features);
 658             let (min_version, span) = match &mis[..] {
 659                 [NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
 660                     (sym, span)
 661                 }
 662                 [
 663                     NestedMetaItem::Lit(MetaItemLit { span, .. })
 664                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 665                 ] => {
 666                     sess.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
 667                     return false;
 668                 }
 669                 [..] => {
 670                     sess.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
 671                         span: cfg.span,
 672                     });
 673                     return false;
 674                 }
 675             };
 676             let Some(min_version) = parse_version(min_version.as_str(), false) else {
 677                 sess.emit_warning(session_diagnostics::UnknownVersionLiteral { span: *span });
 678                 return false;
 679             };
 680             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 681
 682             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 683             if sess.assume_incomplete_release {
 684                 rustc_version > min_version
 685             } else {
 686                 rustc_version >= min_version
 687             }
 688         }
 689         ast::MetaItemKind::List(mis) => {
 690             for mi in mis.iter() {
 691                 if !mi.is_meta_item() {
 692                     handle_errors(
 693                         sess,
 694                         mi.span(),
 695                         AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
 696                     );
 697                     return false;
 698                 }
 699             }
 700
 701             // The unwraps below may look dangerous, but we've already asserted
 702             // that they won't fail with the loop above.
 703             match cfg.name_or_empty() {
 704                 sym::any => mis
 705                     .iter()
 706                     // We don't use any() here, because we want to evaluate all cfg condition
 707                     // as eval_condition can (and does) extra checks
 708                     .fold(false, |res, mi| {
 709                         res | eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 710                     }),
 711                 sym::all => mis
 712                     .iter()
 713                     // We don't use all() here, because we want to evaluate all cfg condition
 714                     // as eval_condition can (and does) extra checks
 715                     .fold(true, |res, mi| {
 716                         res & eval_condition(mi.meta_item().unwrap(), sess, features, eval)
 717                     }),
 718                 sym::not => {
 719                     if mis.len() != 1 {
 720                         sess.emit_err(session_diagnostics::ExpectedOneCfgPattern {
 721                             span: cfg.span,
 722                         });
 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                     sess.emit_err(session_diagnostics::InvalidPredicate {
 749                         span: cfg.span,
 750                         predicate: pprust::path_to_string(&cfg.path),
 751                     });
 752                     false
 753                 }
 754             }
 755         }
 756         ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
 757             sess.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
 758             true
 759         }
 760         MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 761             handle_errors(
 762                 sess,
 763                 lit.span,
 764                 AttrError::UnsupportedLiteral(
 765                     UnsupportedLiteralReason::CfgString,
 766                     lit.kind.is_bytestr(),
 767                 ),
 768             );
 769             true
 770         }
 771         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
 772             let ident = cfg.ident().expect("multi-segment cfg predicate");
 773             eval(Condition {
 774                 name: ident.name,
 775                 name_span: ident.span,
 776                 value: cfg.value_str(),
 777                 value_span: cfg.name_value_literal_span(),
 778                 span: cfg.span,
 779             })
 780         }
 781     }
 782 }
 783
 784 #[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
 785 pub struct Deprecation {
 786     pub since: Option<Symbol>,
 787     /// The note to issue a reason.
 788     pub note: Option<Symbol>,
 789     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 790     ///
 791     /// This is currently unstable.
 792     pub suggestion: Option<Symbol>,
 793
 794     /// Whether to treat the since attribute as being a Rust version identifier
 795     /// (rather than an opaque string).
 796     pub is_since_rustc_version: bool,
 797 }
 798
 799 /// Finds the deprecation attribute. `None` if none exists.
 800 pub fn find_deprecation(sess: &Session, attrs: &[Attribute]) -> Option<(Deprecation, Span)> {
 801     find_deprecation_generic(sess, attrs.iter())
 802 }
 803
 804 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 805 where
 806     I: Iterator<Item = &'a Attribute>,
 807 {
 808     let mut depr: Option<(Deprecation, Span)> = None;
 809     let is_rustc = sess.features_untracked().staged_api;
 810
 811     'outer: for attr in attrs_iter {
 812         if !attr.has_name(sym::deprecated) {
 813             continue;
 814         }
 815
 816         let Some(meta) = attr.meta() else {
 817             continue;
 818         };
 819         let mut since = None;
 820         let mut note = None;
 821         let mut suggestion = None;
 822         match &meta.kind {
 823             MetaItemKind::Word => {}
 824             MetaItemKind::NameValue(..) => note = meta.value_str(),
 825             MetaItemKind::List(list) => {
 826                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 827                     if item.is_some() {
 828                         handle_errors(
 829                             &sess.parse_sess,
 830                             meta.span,
 831                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 832                         );
 833                         return false;
 834                     }
 835                     if let Some(v) = meta.value_str() {
 836                         *item = Some(v);
 837                         true
 838                     } else {
 839                         if let Some(lit) = meta.name_value_literal() {
 840                             handle_errors(
 841                                 &sess.parse_sess,
 842                                 lit.span,
 843                                 AttrError::UnsupportedLiteral(
 844                                     UnsupportedLiteralReason::DeprecatedString,
 845                                     lit.kind.is_bytestr(),
 846                                 ),
 847                             );
 848                         } else {
 849                             sess.emit_err(session_diagnostics::IncorrectMetaItem2 {
 850                                 span: meta.span,
 851                             });
 852                         }
 853
 854                         false
 855                     }
 856                 };
 857
 858                 for meta in list {
 859                     match meta {
 860                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 861                             sym::since => {
 862                                 if !get(mi, &mut since) {
 863                                     continue 'outer;
 864                                 }
 865                             }
 866                             sym::note => {
 867                                 if !get(mi, &mut note) {
 868                                     continue 'outer;
 869                                 }
 870                             }
 871                             sym::suggestion => {
 872                                 if !sess.features_untracked().deprecated_suggestion {
 873                                     sess.emit_err(session_diagnostics::DeprecatedItemSuggestion {
 874                                         span: mi.span,
 875                                         is_nightly: sess.is_nightly_build().then_some(()),
 876                                         details: (),
 877                                     });
 878                                 }
 879
 880                                 if !get(mi, &mut suggestion) {
 881                                     continue 'outer;
 882                                 }
 883                             }
 884                             _ => {
 885                                 handle_errors(
 886                                     &sess.parse_sess,
 887                                     meta.span(),
 888                                     AttrError::UnknownMetaItem(
 889                                         pprust::path_to_string(&mi.path),
 890                                         if sess.features_untracked().deprecated_suggestion {
 891                                             &["since", "note", "suggestion"]
 892                                         } else {
 893                                             &["since", "note"]
 894                                         },
 895                                     ),
 896                                 );
 897                                 continue 'outer;
 898                             }
 899                         },
 900                         NestedMetaItem::Lit(lit) => {
 901                             handle_errors(
 902                                 &sess.parse_sess,
 903                                 lit.span,
 904                                 AttrError::UnsupportedLiteral(
 905                                     UnsupportedLiteralReason::DeprecatedKvPair,
 906                                     false,
 907                                 ),
 908                             );
 909                             continue 'outer;
 910                         }
 911                     }
 912                 }
 913             }
 914         }
 915
 916         if is_rustc {
 917             if since.is_none() {
 918                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 919                 continue;
 920             }
 921
 922             if note.is_none() {
 923                 sess.emit_err(session_diagnostics::MissingNote { span: attr.span });
 924                 continue;
 925             }
 926         }
 927
 928         depr = Some((
 929             Deprecation { since, note, suggestion, is_since_rustc_version: is_rustc },
 930             attr.span,
 931         ));
 932     }
 933
 934     depr
 935 }
 936
 937 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 938 pub enum ReprAttr {
 939     ReprInt(IntType),
 940     ReprC,
 941     ReprPacked(u32),
 942     ReprSimd,
 943     ReprTransparent,
 944     ReprAlign(u32),
 945 }
 946
 947 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 948 #[derive(Encodable, Decodable, HashStable_Generic)]
 949 pub enum IntType {
 950     SignedInt(ast::IntTy),
 951     UnsignedInt(ast::UintTy),
 952 }
 953
 954 impl IntType {
 955     #[inline]
 956     pub fn is_signed(self) -> bool {
 957         use IntType::*;
 958
 959         match self {
 960             SignedInt(..) => true,
 961             UnsignedInt(..) => false,
 962         }
 963     }
 964 }
 965
 966 /// Parse #[repr(...)] forms.
 967 ///
 968 /// Valid repr contents: any of the primitive integral type names (see
 969 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 970 /// the same discriminant size that the corresponding C enum would or C
 971 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 972 /// concerns to the only non-ZST field.
 973 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 974     if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
 975 }
 976
 977 pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 978     assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {attr:?}");
 979     use ReprAttr::*;
 980     let mut acc = Vec::new();
 981     let diagnostic = &sess.parse_sess.span_diagnostic;
 982
 983     if let Some(items) = attr.meta_item_list() {
 984         for item in items {
 985             let mut recognised = false;
 986             if item.is_word() {
 987                 let hint = match item.name_or_empty() {
 988                     sym::C => Some(ReprC),
 989                     sym::packed => Some(ReprPacked(1)),
 990                     sym::simd => Some(ReprSimd),
 991                     sym::transparent => Some(ReprTransparent),
 992                     sym::align => {
 993                         sess.emit_err(session_diagnostics::InvalidReprAlignNeedArg {
 994                             span: item.span(),
 995                         });
 996                         recognised = true;
 997                         None
 998                     }
 999                     name => int_type_of_word(name).map(ReprInt),
1000                 };
1001
1002                 if let Some(h) = hint {
1003                     recognised = true;
1004                     acc.push(h);
1005                 }
1006             } else if let Some((name, value)) = item.name_value_literal() {
1007                 let mut literal_error = None;
1008                 if name == sym::align {
1009                     recognised = true;
1010                     match parse_alignment(&value.kind) {
1011                         Ok(literal) => acc.push(ReprAlign(literal)),
1012                         Err(message) => literal_error = Some(message),
1013                     };
1014                 } else if name == sym::packed {
1015                     recognised = true;
1016                     match parse_alignment(&value.kind) {
1017                         Ok(literal) => acc.push(ReprPacked(literal)),
1018                         Err(message) => literal_error = Some(message),
1019                     };
1020                 } else if matches!(name, sym::C | sym::simd | sym::transparent)
1021                     || int_type_of_word(name).is_some()
1022                 {
1023                     recognised = true;
1024                     sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
1025                         span: item.span(),
1026                         name: name.to_ident_string(),
1027                     });
1028                 }
1029                 if let Some(literal_error) = literal_error {
1030                     sess.emit_err(session_diagnostics::InvalidReprGeneric {
1031                         span: item.span(),
1032                         repr_arg: name.to_ident_string(),
1033                         error_part: literal_error,
1034                     });
1035                 }
1036             } else if let Some(meta_item) = item.meta_item() {
1037                 match &meta_item.kind {
1038                     MetaItemKind::NameValue(value) => {
1039                         if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
1040                             let name = meta_item.name_or_empty().to_ident_string();
1041                             recognised = true;
1042                             sess.emit_err(session_diagnostics::IncorrectReprFormatGeneric {
1043                                 span: item.span(),
1044                                 repr_arg: &name,
1045                                 cause: IncorrectReprFormatGenericCause::from_lit_kind(
1046                                     item.span(),
1047                                     &value.kind,
1048                                     &name,
1049                                 ),
1050                             });
1051                         } else if matches!(
1052                             meta_item.name_or_empty(),
1053                             sym::C | sym::simd | sym::transparent
1054                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1055                         {
1056                             recognised = true;
1057                             sess.emit_err(session_diagnostics::InvalidReprHintNoValue {
1058                                 span: meta_item.span,
1059                                 name: meta_item.name_or_empty().to_ident_string(),
1060                             });
1061                         }
1062                     }
1063                     MetaItemKind::List(_) => {
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(
1072                                 session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
1073                                     span: meta_item.span,
1074                                 },
1075                             );
1076                         } else if matches!(
1077                             meta_item.name_or_empty(),
1078                             sym::C | sym::simd | sym::transparent
1079                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
1080                         {
1081                             recognised = true;
1082                             sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
1083                                 span: meta_item.span,
1084                                 name: meta_item.name_or_empty().to_ident_string(),
1085                             });
1086                         }
1087                     }
1088                     _ => (),
1089                 }
1090             }
1091             if !recognised {
1092                 // Not a word we recognize. This will be caught and reported by
1093                 // the `check_mod_attrs` pass, but this pass doesn't always run
1094                 // (e.g. if we only pretty-print the source), so we have to gate
1095                 // the `delay_span_bug` call as follows:
1096                 if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1097                     diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1098                 }
1099             }
1100         }
1101     }
1102     acc
1103 }
1104
1105 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1106     use IntType::*;
1107
1108     match s {
1109         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1110         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1111         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1112         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1113         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1114         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1115         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1116         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1117         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1118         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1119         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1120         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1121         _ => None,
1122     }
1123 }
1124
1125 pub enum TransparencyError {
1126     UnknownTransparency(Symbol, Span),
1127     MultipleTransparencyAttrs(Span, Span),
1128 }
1129
1130 pub fn find_transparency(
1131     attrs: &[Attribute],
1132     macro_rules: bool,
1133 ) -> (Transparency, Option<TransparencyError>) {
1134     let mut transparency = None;
1135     let mut error = None;
1136     for attr in attrs {
1137         if attr.has_name(sym::rustc_macro_transparency) {
1138             if let Some((_, old_span)) = transparency {
1139                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1140                 break;
1141             } else if let Some(value) = attr.value_str() {
1142                 transparency = Some((
1143                     match value {
1144                         sym::transparent => Transparency::Transparent,
1145                         sym::semitransparent => Transparency::SemiTransparent,
1146                         sym::opaque => Transparency::Opaque,
1147                         _ => {
1148                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1149                             continue;
1150                         }
1151                     },
1152                     attr.span,
1153                 ));
1154             }
1155         }
1156     }
1157     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1158     (transparency.map_or(fallback, |t| t.0), error)
1159 }
1160
1161 pub fn allow_internal_unstable<'a>(
1162     sess: &'a Session,
1163     attrs: &'a [Attribute],
1164 ) -> impl Iterator<Item = Symbol> + 'a {
1165     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1166 }
1167
1168 pub fn rustc_allow_const_fn_unstable<'a>(
1169     sess: &'a Session,
1170     attrs: &'a [Attribute],
1171 ) -> impl Iterator<Item = Symbol> + 'a {
1172     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1173 }
1174
1175 fn allow_unstable<'a>(
1176     sess: &'a Session,
1177     attrs: &'a [Attribute],
1178     symbol: Symbol,
1179 ) -> impl Iterator<Item = Symbol> + 'a {
1180     let attrs = sess.filter_by_name(attrs, symbol);
1181     let list = attrs
1182         .filter_map(move |attr| {
1183             attr.meta_item_list().or_else(|| {
1184                 sess.emit_err(session_diagnostics::ExpectsFeatureList {
1185                     span: attr.span,
1186                     name: symbol.to_ident_string(),
1187                 });
1188                 None
1189             })
1190         })
1191         .flatten();
1192
1193     list.into_iter().filter_map(move |it| {
1194         let name = it.ident().map(|ident| ident.name);
1195         if name.is_none() {
1196             sess.emit_err(session_diagnostics::ExpectsFeatures {
1197                 span: it.span(),
1198                 name: symbol.to_ident_string(),
1199             });
1200         }
1201         name
1202     })
1203 }
1204
1205 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1206     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1207         if literal.is_power_of_two() {
1208             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1209             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1210         } else {
1211             Err("not a power of two")
1212         }
1213     } else {
1214         Err("not an unsuffixed integer")
1215     }
1216 }