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 use version_check::Version;
  14
  15 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  16     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  17 }
  18
  19 enum AttrError {
  20     MultipleItem(String),
  21     UnknownMetaItem(String, &'static [&'static str]),
  22     MissingSince,
  23     NonIdentFeature,
  24     MissingFeature,
  25     MultipleStabilityLevels,
  26     UnsupportedLiteral(&'static str, /* is_bytestr */ bool),
  27 }
  28
  29 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
  30     let diag = &sess.span_diagnostic;
  31     match error {
  32         AttrError::MultipleItem(item) => {
  33             struct_span_err!(diag, span, E0538, "multiple '{}' items", item).emit();
  34         }
  35         AttrError::UnknownMetaItem(item, expected) => {
  36             let expected = expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
  37             struct_span_err!(diag, span, E0541, "unknown meta item '{}'", item)
  38                 .span_label(span, format!("expected one of {}", expected.join(", ")))
  39                 .emit();
  40         }
  41         AttrError::MissingSince => {
  42             struct_span_err!(diag, span, E0542, "missing 'since'").emit();
  43         }
  44         AttrError::NonIdentFeature => {
  45             struct_span_err!(diag, span, E0546, "'feature' is not an identifier").emit();
  46         }
  47         AttrError::MissingFeature => {
  48             struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
  49         }
  50         AttrError::MultipleStabilityLevels => {
  51             struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
  52         }
  53         AttrError::UnsupportedLiteral(msg, is_bytestr) => {
  54             let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
  55             if is_bytestr {
  56                 if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
  57                     err.span_suggestion(
  58                         span,
  59                         "consider removing the prefix",
  60                         lint_str[1..].to_string(),
  61                         Applicability::MaybeIncorrect,
  62                     );
  63                 }
  64             }
  65             err.emit();
  66         }
  67     }
  68 }
  69
  70 #[derive(Clone, PartialEq, Encodable, Decodable)]
  71 pub enum InlineAttr {
  72     None,
  73     Hint,
  74     Always,
  75     Never,
  76 }
  77
  78 #[derive(Clone, Encodable, Decodable)]
  79 pub enum OptimizeAttr {
  80     None,
  81     Speed,
  82     Size,
  83 }
  84
  85 #[derive(Copy, Clone, PartialEq)]
  86 pub enum UnwindAttr {
  87     Allowed,
  88     Aborts,
  89 }
  90
  91 /// Determine what `#[unwind]` attribute is present in `attrs`, if any.
  92 pub fn find_unwind_attr(sess: &Session, attrs: &[Attribute]) -> Option<UnwindAttr> {
  93     attrs.iter().fold(None, |ia, attr| {
  94         if sess.check_name(attr, sym::unwind) {
  95             if let Some(meta) = attr.meta() {
  96                 if let MetaItemKind::List(items) = meta.kind {
  97                     if items.len() == 1 {
  98                         if items[0].has_name(sym::allowed) {
  99                             return Some(UnwindAttr::Allowed);
 100                         } else if items[0].has_name(sym::aborts) {
 101                             return Some(UnwindAttr::Aborts);
 102                         }
 103                     }
 104
 105                     struct_span_err!(
 106                         sess.diagnostic(),
 107                         attr.span,
 108                         E0633,
 109                         "malformed `unwind` attribute input"
 110                     )
 111                     .span_label(attr.span, "invalid argument")
 112                     .span_suggestions(
 113                         attr.span,
 114                         "the allowed arguments are `allowed` and `aborts`",
 115                         (vec!["allowed", "aborts"])
 116                             .into_iter()
 117                             .map(|s| format!("#[unwind({})]", s)),
 118                         Applicability::MachineApplicable,
 119                     )
 120                     .emit();
 121                 }
 122             }
 123         }
 124
 125         ia
 126     })
 127 }
 128
 129 /// Represents the following attributes:
 130 ///
 131 /// - `#[stable]`
 132 /// - `#[unstable]`
 133 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 134 #[derive(HashStable_Generic)]
 135 pub struct Stability {
 136     pub level: StabilityLevel,
 137     pub feature: Symbol,
 138 }
 139
 140 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 141 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 142 #[derive(HashStable_Generic)]
 143 pub struct ConstStability {
 144     pub level: StabilityLevel,
 145     pub feature: Symbol,
 146     /// whether the function has a `#[rustc_promotable]` attribute
 147     pub promotable: bool,
 148     /// whether the function has a `#[rustc_allow_const_fn_ptr]` attribute
 149     pub allow_const_fn_ptr: bool,
 150 }
 151
 152 /// The available stability levels.
 153 #[derive(Encodable, Decodable, PartialEq, PartialOrd, Copy, Clone, Debug, Eq, Hash)]
 154 #[derive(HashStable_Generic)]
 155 pub enum StabilityLevel {
 156     // Reason for the current stability level and the relevant rust-lang issue
 157     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 158     Stable { since: Symbol },
 159 }
 160
 161 impl StabilityLevel {
 162     pub fn is_unstable(&self) -> bool {
 163         matches!(self, StabilityLevel::Unstable { .. })
 164     }
 165     pub fn is_stable(&self) -> bool {
 166         matches!(self, StabilityLevel::Stable { .. })
 167     }
 168 }
 169
 170 /// Collects stability info from all stability attributes in `attrs`.
 171 /// Returns `None` if no stability attributes are found.
 172 pub fn find_stability(
 173     sess: &Session,
 174     attrs: &[Attribute],
 175     item_sp: Span,
 176 ) -> (Option<Stability>, Option<ConstStability>) {
 177     find_stability_generic(sess, attrs.iter(), item_sp)
 178 }
 179
 180 fn find_stability_generic<'a, I>(
 181     sess: &Session,
 182     attrs_iter: I,
 183     item_sp: Span,
 184 ) -> (Option<Stability>, Option<ConstStability>)
 185 where
 186     I: Iterator<Item = &'a Attribute>,
 187 {
 188     use StabilityLevel::*;
 189
 190     let mut stab: Option<Stability> = None;
 191     let mut const_stab: Option<ConstStability> = None;
 192     let mut promotable = false;
 193     let mut allow_const_fn_ptr = false;
 194     let diagnostic = &sess.parse_sess.span_diagnostic;
 195
 196     'outer: for attr in attrs_iter {
 197         if ![
 198             sym::rustc_const_unstable,
 199             sym::rustc_const_stable,
 200             sym::unstable,
 201             sym::stable,
 202             sym::rustc_promotable,
 203             sym::rustc_allow_const_fn_ptr,
 204         ]
 205         .iter()
 206         .any(|&s| attr.has_name(s))
 207         {
 208             continue; // not a stability level
 209         }
 210
 211         sess.mark_attr_used(attr);
 212
 213         let meta = attr.meta();
 214
 215         if attr.has_name(sym::rustc_promotable) {
 216             promotable = true;
 217         }
 218         if attr.has_name(sym::rustc_allow_const_fn_ptr) {
 219             allow_const_fn_ptr = true;
 220         }
 221         // attributes with data
 222         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 223             let meta = meta.as_ref().unwrap();
 224             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 225                 if item.is_some() {
 226                     handle_errors(
 227                         &sess.parse_sess,
 228                         meta.span,
 229                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 230                     );
 231                     return false;
 232                 }
 233                 if let Some(v) = meta.value_str() {
 234                     *item = Some(v);
 235                     true
 236                 } else {
 237                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 238                     false
 239                 }
 240             };
 241
 242             let meta_name = meta.name_or_empty();
 243             match meta_name {
 244                 sym::rustc_const_unstable | sym::unstable => {
 245                     if meta_name == sym::unstable && stab.is_some() {
 246                         handle_errors(
 247                             &sess.parse_sess,
 248                             attr.span,
 249                             AttrError::MultipleStabilityLevels,
 250                         );
 251                         break;
 252                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 253                         handle_errors(
 254                             &sess.parse_sess,
 255                             attr.span,
 256                             AttrError::MultipleStabilityLevels,
 257                         );
 258                         break;
 259                     }
 260
 261                     let mut feature = None;
 262                     let mut reason = None;
 263                     let mut issue = None;
 264                     let mut issue_num = None;
 265                     let mut is_soft = false;
 266                     for meta in metas {
 267                         if let Some(mi) = meta.meta_item() {
 268                             match mi.name_or_empty() {
 269                                 sym::feature => {
 270                                     if !get(mi, &mut feature) {
 271                                         continue 'outer;
 272                                     }
 273                                 }
 274                                 sym::reason => {
 275                                     if !get(mi, &mut reason) {
 276                                         continue 'outer;
 277                                     }
 278                                 }
 279                                 sym::issue => {
 280                                     if !get(mi, &mut issue) {
 281                                         continue 'outer;
 282                                     }
 283
 284                                     // These unwraps are safe because `get` ensures the meta item
 285                                     // is a name/value pair string literal.
 286                                     issue_num = match &*issue.unwrap().as_str() {
 287                                         "none" => None,
 288                                         issue => {
 289                                             let emit_diag = |msg: &str| {
 290                                                 struct_span_err!(
 291                                                     diagnostic,
 292                                                     mi.span,
 293                                                     E0545,
 294                                                     "`issue` must be a non-zero numeric string \
 295                                                     or \"none\"",
 296                                                 )
 297                                                 .span_label(
 298                                                     mi.name_value_literal().unwrap().span,
 299                                                     msg,
 300                                                 )
 301                                                 .emit();
 302                                             };
 303                                             match issue.parse() {
 304                                                 Ok(num) if num == 0 => {
 305                                                     emit_diag(
 306                                                         "`issue` must not be \"0\", \
 307                                                         use \"none\" instead",
 308                                                     );
 309                                                     continue 'outer;
 310                                                 }
 311                                                 Ok(num) => NonZeroU32::new(num),
 312                                                 Err(err) => {
 313                                                     emit_diag(&err.to_string());
 314                                                     continue 'outer;
 315                                                 }
 316                                             }
 317                                         }
 318                                     };
 319                                 }
 320                                 sym::soft => {
 321                                     if !mi.is_word() {
 322                                         let msg = "`soft` should not have any arguments";
 323                                         sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 324                                     }
 325                                     is_soft = true;
 326                                 }
 327                                 _ => {
 328                                     handle_errors(
 329                                         &sess.parse_sess,
 330                                         meta.span(),
 331                                         AttrError::UnknownMetaItem(
 332                                             pprust::path_to_string(&mi.path),
 333                                             &["feature", "reason", "issue", "soft"],
 334                                         ),
 335                                     );
 336                                     continue 'outer;
 337                                 }
 338                             }
 339                         } else {
 340                             handle_errors(
 341                                 &sess.parse_sess,
 342                                 meta.span(),
 343                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 344                             );
 345                             continue 'outer;
 346                         }
 347                     }
 348
 349                     match (feature, reason, issue) {
 350                         (Some(feature), reason, Some(_)) => {
 351                             if !rustc_lexer::is_ident(&feature.as_str()) {
 352                                 handle_errors(
 353                                     &sess.parse_sess,
 354                                     attr.span,
 355                                     AttrError::NonIdentFeature,
 356                                 );
 357                                 continue;
 358                             }
 359                             let level = Unstable { reason, issue: issue_num, is_soft };
 360                             if sym::unstable == meta_name {
 361                                 stab = Some(Stability { level, feature });
 362                             } else {
 363                                 const_stab = Some(ConstStability {
 364                                     level,
 365                                     feature,
 366                                     promotable: false,
 367                                     allow_const_fn_ptr: false,
 368                                 });
 369                             }
 370                         }
 371                         (None, _, _) => {
 372                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 373                             continue;
 374                         }
 375                         _ => {
 376                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 377                                 .emit();
 378                             continue;
 379                         }
 380                     }
 381                 }
 382                 sym::rustc_const_stable | sym::stable => {
 383                     if meta_name == sym::stable && stab.is_some() {
 384                         handle_errors(
 385                             &sess.parse_sess,
 386                             attr.span,
 387                             AttrError::MultipleStabilityLevels,
 388                         );
 389                         break;
 390                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 391                         handle_errors(
 392                             &sess.parse_sess,
 393                             attr.span,
 394                             AttrError::MultipleStabilityLevels,
 395                         );
 396                         break;
 397                     }
 398
 399                     let mut feature = None;
 400                     let mut since = None;
 401                     for meta in metas {
 402                         match meta {
 403                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 404                                 sym::feature => {
 405                                     if !get(mi, &mut feature) {
 406                                         continue 'outer;
 407                                     }
 408                                 }
 409                                 sym::since => {
 410                                     if !get(mi, &mut since) {
 411                                         continue 'outer;
 412                                     }
 413                                 }
 414                                 _ => {
 415                                     handle_errors(
 416                                         &sess.parse_sess,
 417                                         meta.span(),
 418                                         AttrError::UnknownMetaItem(
 419                                             pprust::path_to_string(&mi.path),
 420                                             &["since", "note"],
 421                                         ),
 422                                     );
 423                                     continue 'outer;
 424                                 }
 425                             },
 426                             NestedMetaItem::Literal(lit) => {
 427                                 handle_errors(
 428                                     &sess.parse_sess,
 429                                     lit.span,
 430                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 431                                 );
 432                                 continue 'outer;
 433                             }
 434                         }
 435                     }
 436
 437                     match (feature, since) {
 438                         (Some(feature), Some(since)) => {
 439                             let level = Stable { since };
 440                             if sym::stable == meta_name {
 441                                 stab = Some(Stability { level, feature });
 442                             } else {
 443                                 const_stab = Some(ConstStability {
 444                                     level,
 445                                     feature,
 446                                     promotable: false,
 447                                     allow_const_fn_ptr: false,
 448                                 });
 449                             }
 450                         }
 451                         (None, _) => {
 452                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 453                             continue;
 454                         }
 455                         _ => {
 456                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 457                             continue;
 458                         }
 459                     }
 460                 }
 461                 _ => unreachable!(),
 462             }
 463         }
 464     }
 465
 466     // Merge the const-unstable info into the stability info
 467     if promotable || allow_const_fn_ptr {
 468         if let Some(ref mut stab) = const_stab {
 469             stab.promotable = promotable;
 470             stab.allow_const_fn_ptr = allow_const_fn_ptr;
 471         } else {
 472             struct_span_err!(
 473                 diagnostic,
 474                 item_sp,
 475                 E0717,
 476                 "rustc_promotable and rustc_allow_const_fn_ptr attributes \
 477                       must be paired with either a rustc_const_unstable or a rustc_const_stable \
 478                       attribute"
 479             )
 480             .emit();
 481         }
 482     }
 483
 484     (stab, const_stab)
 485 }
 486
 487 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 488     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 489 }
 490
 491 /// Tests if a cfg-pattern matches the cfg set
 492 pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) -> bool {
 493     eval_condition(cfg, sess, features, &mut |cfg| {
 494         try_gate_cfg(cfg, sess, features);
 495         let error = |span, msg| {
 496             sess.span_diagnostic.span_err(span, msg);
 497             true
 498         };
 499         if cfg.path.segments.len() != 1 {
 500             return error(cfg.path.span, "`cfg` predicate key must be an identifier");
 501         }
 502         match &cfg.kind {
 503             MetaItemKind::List(..) => {
 504                 error(cfg.span, "unexpected parentheses after `cfg` predicate key")
 505             }
 506             MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 507                 handle_errors(
 508                     sess,
 509                     lit.span,
 510                     AttrError::UnsupportedLiteral(
 511                         "literal in `cfg` predicate value must be a string",
 512                         lit.kind.is_bytestr(),
 513                     ),
 514                 );
 515                 true
 516             }
 517             MetaItemKind::NameValue(..) | MetaItemKind::Word => {
 518                 let ident = cfg.ident().expect("multi-segment cfg predicate");
 519                 sess.config.contains(&(ident.name, cfg.value_str()))
 520             }
 521         }
 522     })
 523 }
 524
 525 fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
 526     let gate = find_gated_cfg(|sym| cfg.has_name(sym));
 527     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 528         gate_cfg(&gated_cfg, cfg.span, sess, feats);
 529     }
 530 }
 531
 532 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 533     let (cfg, feature, has_feature) = gated_cfg;
 534     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 535         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 536         feature_err(sess, *feature, cfg_span, &explain).emit();
 537     }
 538 }
 539
 540 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 541 /// evaluate individual items.
 542 pub fn eval_condition(
 543     cfg: &ast::MetaItem,
 544     sess: &ParseSess,
 545     features: Option<&Features>,
 546     eval: &mut impl FnMut(&ast::MetaItem) -> bool,
 547 ) -> bool {
 548     match cfg.kind {
 549         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 550             try_gate_cfg(cfg, sess, features);
 551             let (min_version, span) = match &mis[..] {
 552                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 553                     (sym, span)
 554                 }
 555                 [NestedMetaItem::Literal(Lit { span, .. })
 556                 | NestedMetaItem::MetaItem(MetaItem { span, .. })] => {
 557                     sess.span_diagnostic
 558                         .struct_span_err(*span, "expected a version literal")
 559                         .emit();
 560                     return false;
 561                 }
 562                 [..] => {
 563                     sess.span_diagnostic
 564                         .struct_span_err(cfg.span, "expected single version literal")
 565                         .emit();
 566                     return false;
 567                 }
 568             };
 569             let min_version = match Version::parse(&min_version.as_str()) {
 570                 Some(ver) => ver,
 571                 None => {
 572                     sess.span_diagnostic.struct_span_err(*span, "invalid version literal").emit();
 573                     return false;
 574                 }
 575             };
 576             let channel = env!("CFG_RELEASE_CHANNEL");
 577             let nightly = channel == "nightly" || channel == "dev";
 578             let rustc_version = Version::parse(env!("CFG_RELEASE")).unwrap();
 579
 580             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-625474439 for details
 581             if nightly { rustc_version > min_version } else { rustc_version >= min_version }
 582         }
 583         ast::MetaItemKind::List(ref mis) => {
 584             for mi in mis.iter() {
 585                 if !mi.is_meta_item() {
 586                     handle_errors(
 587                         sess,
 588                         mi.span(),
 589                         AttrError::UnsupportedLiteral("unsupported literal", false),
 590                     );
 591                     return false;
 592                 }
 593             }
 594
 595             // The unwraps below may look dangerous, but we've already asserted
 596             // that they won't fail with the loop above.
 597             match cfg.name_or_empty() {
 598                 sym::any => mis
 599                     .iter()
 600                     .any(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 601                 sym::all => mis
 602                     .iter()
 603                     .all(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 604                 sym::not => {
 605                     if mis.len() != 1 {
 606                         struct_span_err!(
 607                             sess.span_diagnostic,
 608                             cfg.span,
 609                             E0536,
 610                             "expected 1 cfg-pattern"
 611                         )
 612                         .emit();
 613                         return false;
 614                     }
 615
 616                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 617                 }
 618                 _ => {
 619                     struct_span_err!(
 620                         sess.span_diagnostic,
 621                         cfg.span,
 622                         E0537,
 623                         "invalid predicate `{}`",
 624                         pprust::path_to_string(&cfg.path)
 625                     )
 626                     .emit();
 627                     false
 628                 }
 629             }
 630         }
 631         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => eval(cfg),
 632     }
 633 }
 634
 635 #[derive(Encodable, Decodable, Clone, HashStable_Generic)]
 636 pub struct Deprecation {
 637     pub since: Option<Symbol>,
 638     /// The note to issue a reason.
 639     pub note: Option<Symbol>,
 640     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 641     ///
 642     /// This is currently unstable.
 643     pub suggestion: Option<Symbol>,
 644
 645     /// Whether to treat the since attribute as being a Rust version identifier
 646     /// (rather than an opaque string).
 647     pub is_since_rustc_version: bool,
 648 }
 649
 650 /// Finds the deprecation attribute. `None` if none exists.
 651 pub fn find_deprecation(sess: &Session, attrs: &[Attribute], item_sp: Span) -> Option<Deprecation> {
 652     find_deprecation_generic(sess, attrs.iter(), item_sp)
 653 }
 654
 655 fn find_deprecation_generic<'a, I>(
 656     sess: &Session,
 657     attrs_iter: I,
 658     item_sp: Span,
 659 ) -> Option<Deprecation>
 660 where
 661     I: Iterator<Item = &'a Attribute>,
 662 {
 663     let mut depr: Option<Deprecation> = None;
 664     let diagnostic = &sess.parse_sess.span_diagnostic;
 665
 666     'outer: for attr in attrs_iter {
 667         if !(sess.check_name(attr, sym::deprecated) || sess.check_name(attr, sym::rustc_deprecated))
 668         {
 669             continue;
 670         }
 671
 672         if depr.is_some() {
 673             struct_span_err!(diagnostic, item_sp, E0550, "multiple deprecated attributes").emit();
 674             break;
 675         }
 676
 677         let meta = match attr.meta() {
 678             Some(meta) => meta,
 679             None => continue,
 680         };
 681         let mut since = None;
 682         let mut note = None;
 683         let mut suggestion = None;
 684         match &meta.kind {
 685             MetaItemKind::Word => {}
 686             MetaItemKind::NameValue(..) => note = meta.value_str(),
 687             MetaItemKind::List(list) => {
 688                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 689                     if item.is_some() {
 690                         handle_errors(
 691                             &sess.parse_sess,
 692                             meta.span,
 693                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 694                         );
 695                         return false;
 696                     }
 697                     if let Some(v) = meta.value_str() {
 698                         *item = Some(v);
 699                         true
 700                     } else {
 701                         if let Some(lit) = meta.name_value_literal() {
 702                             handle_errors(
 703                                 &sess.parse_sess,
 704                                 lit.span,
 705                                 AttrError::UnsupportedLiteral(
 706                                     "literal in `deprecated` \
 707                                     value must be a string",
 708                                     lit.kind.is_bytestr(),
 709                                 ),
 710                             );
 711                         } else {
 712                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 713                                 .emit();
 714                         }
 715
 716                         false
 717                     }
 718                 };
 719
 720                 for meta in list {
 721                     match meta {
 722                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 723                             sym::since => {
 724                                 if !get(mi, &mut since) {
 725                                     continue 'outer;
 726                                 }
 727                             }
 728                             sym::note if sess.check_name(attr, sym::deprecated) => {
 729                                 if !get(mi, &mut note) {
 730                                     continue 'outer;
 731                                 }
 732                             }
 733                             sym::reason if sess.check_name(attr, sym::rustc_deprecated) => {
 734                                 if !get(mi, &mut note) {
 735                                     continue 'outer;
 736                                 }
 737                             }
 738                             sym::suggestion if sess.check_name(attr, sym::rustc_deprecated) => {
 739                                 if !get(mi, &mut suggestion) {
 740                                     continue 'outer;
 741                                 }
 742                             }
 743                             _ => {
 744                                 handle_errors(
 745                                     &sess.parse_sess,
 746                                     meta.span(),
 747                                     AttrError::UnknownMetaItem(
 748                                         pprust::path_to_string(&mi.path),
 749                                         if sess.check_name(attr, sym::deprecated) {
 750                                             &["since", "note"]
 751                                         } else {
 752                                             &["since", "reason", "suggestion"]
 753                                         },
 754                                     ),
 755                                 );
 756                                 continue 'outer;
 757                             }
 758                         },
 759                         NestedMetaItem::Literal(lit) => {
 760                             handle_errors(
 761                                 &sess.parse_sess,
 762                                 lit.span,
 763                                 AttrError::UnsupportedLiteral(
 764                                     "item in `deprecated` must be a key/value pair",
 765                                     false,
 766                                 ),
 767                             );
 768                             continue 'outer;
 769                         }
 770                     }
 771                 }
 772             }
 773         }
 774
 775         if suggestion.is_some() && sess.check_name(attr, sym::deprecated) {
 776             unreachable!("only allowed on rustc_deprecated")
 777         }
 778
 779         if sess.check_name(attr, sym::rustc_deprecated) {
 780             if since.is_none() {
 781                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 782                 continue;
 783             }
 784
 785             if note.is_none() {
 786                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'").emit();
 787                 continue;
 788             }
 789         }
 790
 791         sess.mark_attr_used(&attr);
 792
 793         let is_since_rustc_version = sess.check_name(attr, sym::rustc_deprecated);
 794         depr = Some(Deprecation { since, note, suggestion, is_since_rustc_version });
 795     }
 796
 797     depr
 798 }
 799
 800 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 801 pub enum ReprAttr {
 802     ReprInt(IntType),
 803     ReprC,
 804     ReprPacked(u32),
 805     ReprSimd,
 806     ReprTransparent,
 807     ReprAlign(u32),
 808     ReprNoNiche,
 809 }
 810
 811 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 812 #[derive(Encodable, Decodable, HashStable_Generic)]
 813 pub enum IntType {
 814     SignedInt(ast::IntTy),
 815     UnsignedInt(ast::UintTy),
 816 }
 817
 818 impl IntType {
 819     #[inline]
 820     pub fn is_signed(self) -> bool {
 821         use IntType::*;
 822
 823         match self {
 824             SignedInt(..) => true,
 825             UnsignedInt(..) => false,
 826         }
 827     }
 828 }
 829
 830 /// Parse #[repr(...)] forms.
 831 ///
 832 /// Valid repr contents: any of the primitive integral type names (see
 833 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 834 /// the same discriminant size that the corresponding C enum would or C
 835 /// structure layout, `packed` to remove padding, and `transparent` to elegate representation
 836 /// concerns to the only non-ZST field.
 837 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 838     use ReprAttr::*;
 839
 840     let mut acc = Vec::new();
 841     let diagnostic = &sess.parse_sess.span_diagnostic;
 842     if attr.has_name(sym::repr) {
 843         if let Some(items) = attr.meta_item_list() {
 844             sess.mark_attr_used(attr);
 845             for item in items {
 846                 if !item.is_meta_item() {
 847                     handle_errors(
 848                         &sess.parse_sess,
 849                         item.span(),
 850                         AttrError::UnsupportedLiteral(
 851                             "meta item in `repr` must be an identifier",
 852                             false,
 853                         ),
 854                     );
 855                     continue;
 856                 }
 857
 858                 let mut recognised = false;
 859                 if item.is_word() {
 860                     let hint = match item.name_or_empty() {
 861                         sym::C => Some(ReprC),
 862                         sym::packed => Some(ReprPacked(1)),
 863                         sym::simd => Some(ReprSimd),
 864                         sym::transparent => Some(ReprTransparent),
 865                         sym::no_niche => Some(ReprNoNiche),
 866                         name => int_type_of_word(name).map(ReprInt),
 867                     };
 868
 869                     if let Some(h) = hint {
 870                         recognised = true;
 871                         acc.push(h);
 872                     }
 873                 } else if let Some((name, value)) = item.name_value_literal() {
 874                     let parse_alignment = |node: &ast::LitKind| -> Result<u32, &'static str> {
 875                         if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
 876                             if literal.is_power_of_two() {
 877                                 // rustc_middle::ty::layout::Align restricts align to <= 2^29
 878                                 if *literal <= 1 << 29 {
 879                                     Ok(*literal as u32)
 880                                 } else {
 881                                     Err("larger than 2^29")
 882                                 }
 883                             } else {
 884                                 Err("not a power of two")
 885                             }
 886                         } else {
 887                             Err("not an unsuffixed integer")
 888                         }
 889                     };
 890
 891                     let mut literal_error = None;
 892                     if name == sym::align {
 893                         recognised = true;
 894                         match parse_alignment(&value.kind) {
 895                             Ok(literal) => acc.push(ReprAlign(literal)),
 896                             Err(message) => literal_error = Some(message),
 897                         };
 898                     } else if name == sym::packed {
 899                         recognised = true;
 900                         match parse_alignment(&value.kind) {
 901                             Ok(literal) => acc.push(ReprPacked(literal)),
 902                             Err(message) => literal_error = Some(message),
 903                         };
 904                     }
 905                     if let Some(literal_error) = literal_error {
 906                         struct_span_err!(
 907                             diagnostic,
 908                             item.span(),
 909                             E0589,
 910                             "invalid `repr(align)` attribute: {}",
 911                             literal_error
 912                         )
 913                         .emit();
 914                     }
 915                 } else {
 916                     if let Some(meta_item) = item.meta_item() {
 917                         if meta_item.has_name(sym::align) {
 918                             if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 919                                 recognised = true;
 920                                 let mut err = struct_span_err!(
 921                                     diagnostic,
 922                                     item.span(),
 923                                     E0693,
 924                                     "incorrect `repr(align)` attribute format"
 925                                 );
 926                                 match value.kind {
 927                                     ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 928                                         err.span_suggestion(
 929                                             item.span(),
 930                                             "use parentheses instead",
 931                                             format!("align({})", int),
 932                                             Applicability::MachineApplicable,
 933                                         );
 934                                     }
 935                                     ast::LitKind::Str(s, _) => {
 936                                         err.span_suggestion(
 937                                             item.span(),
 938                                             "use parentheses instead",
 939                                             format!("align({})", s),
 940                                             Applicability::MachineApplicable,
 941                                         );
 942                                     }
 943                                     _ => {}
 944                                 }
 945                                 err.emit();
 946                             }
 947                         }
 948                     }
 949                 }
 950                 if !recognised {
 951                     // Not a word we recognize
 952                     struct_span_err!(
 953                         diagnostic,
 954                         item.span(),
 955                         E0552,
 956                         "unrecognized representation hint"
 957                     )
 958                     .emit();
 959                 }
 960             }
 961         }
 962     }
 963     acc
 964 }
 965
 966 fn int_type_of_word(s: Symbol) -> Option<IntType> {
 967     use IntType::*;
 968
 969     match s {
 970         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
 971         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
 972         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
 973         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
 974         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
 975         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
 976         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
 977         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
 978         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
 979         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
 980         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
 981         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
 982         _ => None,
 983     }
 984 }
 985
 986 pub enum TransparencyError {
 987     UnknownTransparency(Symbol, Span),
 988     MultipleTransparencyAttrs(Span, Span),
 989 }
 990
 991 pub fn find_transparency(
 992     sess: &Session,
 993     attrs: &[Attribute],
 994     macro_rules: bool,
 995 ) -> (Transparency, Option<TransparencyError>) {
 996     let mut transparency = None;
 997     let mut error = None;
 998     for attr in attrs {
 999         if sess.check_name(attr, sym::rustc_macro_transparency) {
1000             if let Some((_, old_span)) = transparency {
1001                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1002                 break;
1003             } else if let Some(value) = attr.value_str() {
1004                 transparency = Some((
1005                     match value {
1006                         sym::transparent => Transparency::Transparent,
1007                         sym::semitransparent => Transparency::SemiTransparent,
1008                         sym::opaque => Transparency::Opaque,
1009                         _ => {
1010                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1011                             continue;
1012                         }
1013                     },
1014                     attr.span,
1015                 ));
1016             }
1017         }
1018     }
1019     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1020     (transparency.map_or(fallback, |t| t.0), error)
1021 }
1022
1023 pub fn allow_internal_unstable<'a>(
1024     sess: &'a Session,
1025     attrs: &[Attribute],
1026 ) -> Option<impl Iterator<Item = Symbol> + 'a> {
1027     let attr = sess.find_by_name(attrs, sym::allow_internal_unstable)?;
1028     let list = attr.meta_item_list().or_else(|| {
1029         sess.diagnostic()
1030             .span_err(attr.span, "allow_internal_unstable expects list of feature names");
1031         None
1032     })?;
1033     Some(list.into_iter().filter_map(move |it| {
1034         let name = it.ident().map(|ident| ident.name);
1035         if name.is_none() {
1036             sess.diagnostic()
1037                 .span_err(it.span(), "`allow_internal_unstable` expects feature names");
1038         }
1039         name
1040     }))
1041 }