compiler/rustc_attr/src/builtin.rs

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