compiler/rustc_attr/src/builtin.rs

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