compiler/rustc_attr/src/builtin.rs

   1 //! Parsing and validation of builtin attributes
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::node_id::CRATE_NODE_ID;
   5 use rustc_ast::{Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem};
   6 use rustc_ast_pretty::pprust;
   7 use rustc_errors::{struct_span_err, Applicability};
   8 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
   9 use rustc_macros::HashStable_Generic;
  10 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
  11 use rustc_session::parse::{feature_err, ParseSess};
  12 use rustc_session::Session;
  13 use rustc_span::hygiene::Transparency;
  14 use rustc_span::{symbol::sym, symbol::Symbol, Span};
  15 use std::num::NonZeroU32;
  16
  17 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  18     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  19 }
  20
  21 enum AttrError {
  22     MultipleItem(String),
  23     UnknownMetaItem(String, &'static [&'static str]),
  24     MissingSince,
  25     NonIdentFeature,
  26     MissingFeature,
  27     MultipleStabilityLevels,
  28     UnsupportedLiteral(&'static str, /* is_bytestr */ bool),
  29 }
  30
  31 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
  32     let diag = &sess.span_diagnostic;
  33     match error {
  34         AttrError::MultipleItem(item) => {
  35             struct_span_err!(diag, span, E0538, "multiple '{}' items", item).emit();
  36         }
  37         AttrError::UnknownMetaItem(item, expected) => {
  38             let expected = expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
  39             struct_span_err!(diag, span, E0541, "unknown meta item '{}'", item)
  40                 .span_label(span, format!("expected one of {}", expected.join(", ")))
  41                 .emit();
  42         }
  43         AttrError::MissingSince => {
  44             struct_span_err!(diag, span, E0542, "missing 'since'").emit();
  45         }
  46         AttrError::NonIdentFeature => {
  47             struct_span_err!(diag, span, E0546, "'feature' is not an identifier").emit();
  48         }
  49         AttrError::MissingFeature => {
  50             struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
  51         }
  52         AttrError::MultipleStabilityLevels => {
  53             struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
  54         }
  55         AttrError::UnsupportedLiteral(msg, is_bytestr) => {
  56             let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
  57             if is_bytestr {
  58                 if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
  59                     err.span_suggestion(
  60                         span,
  61                         "consider removing the prefix",
  62                         lint_str[1..].to_string(),
  63                         Applicability::MaybeIncorrect,
  64                     );
  65                 }
  66             }
  67             err.emit();
  68         }
  69     }
  70 }
  71
  72 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
  73 pub enum InlineAttr {
  74     None,
  75     Hint,
  76     Always,
  77     Never,
  78 }
  79
  80 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
  81 pub enum InstructionSetAttr {
  82     ArmA32,
  83     ArmT32,
  84 }
  85
  86 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
  87 pub enum OptimizeAttr {
  88     None,
  89     Speed,
  90     Size,
  91 }
  92
  93 /// Represents the following attributes:
  94 ///
  95 /// - `#[stable]`
  96 /// - `#[unstable]`
  97 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
  98 #[derive(HashStable_Generic)]
  99 pub struct Stability {
 100     pub level: StabilityLevel,
 101     pub feature: Symbol,
 102 }
 103
 104 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 105 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 106 #[derive(HashStable_Generic)]
 107 pub struct ConstStability {
 108     pub level: StabilityLevel,
 109     pub feature: Symbol,
 110     /// whether the function has a `#[rustc_promotable]` attribute
 111     pub promotable: bool,
 112 }
 113
 114 /// The available stability levels.
 115 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 116 #[derive(HashStable_Generic)]
 117 pub enum StabilityLevel {
 118     // Reason for the current stability level and the relevant rust-lang issue
 119     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 120     Stable { since: Symbol },
 121 }
 122
 123 impl StabilityLevel {
 124     pub fn is_unstable(&self) -> bool {
 125         matches!(self, StabilityLevel::Unstable { .. })
 126     }
 127     pub fn is_stable(&self) -> bool {
 128         matches!(self, StabilityLevel::Stable { .. })
 129     }
 130 }
 131
 132 /// Collects stability info from all stability attributes in `attrs`.
 133 /// Returns `None` if no stability attributes are found.
 134 pub fn find_stability(
 135     sess: &Session,
 136     attrs: &[Attribute],
 137     item_sp: Span,
 138 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
 139     find_stability_generic(sess, attrs.iter(), item_sp)
 140 }
 141
 142 fn find_stability_generic<'a, I>(
 143     sess: &Session,
 144     attrs_iter: I,
 145     item_sp: Span,
 146 ) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
 147 where
 148     I: Iterator<Item = &'a Attribute>,
 149 {
 150     use StabilityLevel::*;
 151
 152     let mut stab: Option<(Stability, Span)> = None;
 153     let mut const_stab: Option<(ConstStability, Span)> = None;
 154     let mut promotable = false;
 155
 156     let diagnostic = &sess.parse_sess.span_diagnostic;
 157
 158     'outer: for attr in attrs_iter {
 159         if ![
 160             sym::rustc_const_unstable,
 161             sym::rustc_const_stable,
 162             sym::unstable,
 163             sym::stable,
 164             sym::rustc_promotable,
 165         ]
 166         .iter()
 167         .any(|&s| attr.has_name(s))
 168         {
 169             continue; // not a stability level
 170         }
 171
 172         let meta = attr.meta();
 173
 174         if attr.has_name(sym::rustc_promotable) {
 175             promotable = true;
 176         }
 177         // attributes with data
 178         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 179             let meta = meta.as_ref().unwrap();
 180             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 181                 if item.is_some() {
 182                     handle_errors(
 183                         &sess.parse_sess,
 184                         meta.span,
 185                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 186                     );
 187                     return false;
 188                 }
 189                 if let Some(v) = meta.value_str() {
 190                     *item = Some(v);
 191                     true
 192                 } else {
 193                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 194                     false
 195                 }
 196             };
 197
 198             let meta_name = meta.name_or_empty();
 199             match meta_name {
 200                 sym::rustc_const_unstable | sym::unstable => {
 201                     if meta_name == sym::unstable && stab.is_some() {
 202                         handle_errors(
 203                             &sess.parse_sess,
 204                             attr.span,
 205                             AttrError::MultipleStabilityLevels,
 206                         );
 207                         break;
 208                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 209                         handle_errors(
 210                             &sess.parse_sess,
 211                             attr.span,
 212                             AttrError::MultipleStabilityLevels,
 213                         );
 214                         break;
 215                     }
 216
 217                     let mut feature = None;
 218                     let mut reason = None;
 219                     let mut issue = None;
 220                     let mut issue_num = None;
 221                     let mut is_soft = false;
 222                     for meta in metas {
 223                         let Some(mi) = meta.meta_item() else {
 224                             handle_errors(
 225                                 &sess.parse_sess,
 226                                 meta.span(),
 227                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 228                             );
 229                             continue 'outer;
 230                         };
 231                         match mi.name_or_empty() {
 232                             sym::feature => {
 233                                 if !get(mi, &mut feature) {
 234                                     continue 'outer;
 235                                 }
 236                             }
 237                             sym::reason => {
 238                                 if !get(mi, &mut reason) {
 239                                     continue 'outer;
 240                                 }
 241                             }
 242                             sym::issue => {
 243                                 if !get(mi, &mut issue) {
 244                                     continue 'outer;
 245                                 }
 246
 247                                 // These unwraps are safe because `get` ensures the meta item
 248                                 // is a name/value pair string literal.
 249                                 issue_num = match issue.unwrap().as_str() {
 250                                     "none" => None,
 251                                     issue => {
 252                                         let emit_diag = |msg: &str| {
 253                                             struct_span_err!(
 254                                                 diagnostic,
 255                                                 mi.span,
 256                                                 E0545,
 257                                                 "`issue` must be a non-zero numeric string \
 258                                                 or \"none\"",
 259                                             )
 260                                             .span_label(mi.name_value_literal_span().unwrap(), msg)
 261                                             .emit();
 262                                         };
 263                                         match issue.parse() {
 264                                             Ok(0) => {
 265                                                 emit_diag(
 266                                                     "`issue` must not be \"0\", \
 267                                                     use \"none\" instead",
 268                                                 );
 269                                                 continue 'outer;
 270                                             }
 271                                             Ok(num) => NonZeroU32::new(num),
 272                                             Err(err) => {
 273                                                 emit_diag(&err.to_string());
 274                                                 continue 'outer;
 275                                             }
 276                                         }
 277                                     }
 278                                 };
 279                             }
 280                             sym::soft => {
 281                                 if !mi.is_word() {
 282                                     let msg = "`soft` should not have any arguments";
 283                                     sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
 284                                 }
 285                                 is_soft = true;
 286                             }
 287                             _ => {
 288                                 handle_errors(
 289                                     &sess.parse_sess,
 290                                     meta.span(),
 291                                     AttrError::UnknownMetaItem(
 292                                         pprust::path_to_string(&mi.path),
 293                                         &["feature", "reason", "issue", "soft"],
 294                                     ),
 295                                 );
 296                                 continue 'outer;
 297                             }
 298                         }
 299                     }
 300
 301                     match (feature, reason, issue) {
 302                         (Some(feature), reason, Some(_)) => {
 303                             if !rustc_lexer::is_ident(feature.as_str()) {
 304                                 handle_errors(
 305                                     &sess.parse_sess,
 306                                     attr.span,
 307                                     AttrError::NonIdentFeature,
 308                                 );
 309                                 continue;
 310                             }
 311                             let level = Unstable { reason, issue: issue_num, is_soft };
 312                             if sym::unstable == meta_name {
 313                                 stab = Some((Stability { level, feature }, attr.span));
 314                             } else {
 315                                 const_stab = Some((
 316                                     ConstStability { level, feature, promotable: false },
 317                                     attr.span,
 318                                 ));
 319                             }
 320                         }
 321                         (None, _, _) => {
 322                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 323                             continue;
 324                         }
 325                         _ => {
 326                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 327                                 .emit();
 328                             continue;
 329                         }
 330                     }
 331                 }
 332                 sym::rustc_const_stable | sym::stable => {
 333                     if meta_name == sym::stable && stab.is_some() {
 334                         handle_errors(
 335                             &sess.parse_sess,
 336                             attr.span,
 337                             AttrError::MultipleStabilityLevels,
 338                         );
 339                         break;
 340                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 341                         handle_errors(
 342                             &sess.parse_sess,
 343                             attr.span,
 344                             AttrError::MultipleStabilityLevels,
 345                         );
 346                         break;
 347                     }
 348
 349                     let mut feature = None;
 350                     let mut since = None;
 351                     for meta in metas {
 352                         match meta {
 353                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 354                                 sym::feature => {
 355                                     if !get(mi, &mut feature) {
 356                                         continue 'outer;
 357                                     }
 358                                 }
 359                                 sym::since => {
 360                                     if !get(mi, &mut since) {
 361                                         continue 'outer;
 362                                     }
 363                                 }
 364                                 _ => {
 365                                     handle_errors(
 366                                         &sess.parse_sess,
 367                                         meta.span(),
 368                                         AttrError::UnknownMetaItem(
 369                                             pprust::path_to_string(&mi.path),
 370                                             &["since", "note"],
 371                                         ),
 372                                     );
 373                                     continue 'outer;
 374                                 }
 375                             },
 376                             NestedMetaItem::Literal(lit) => {
 377                                 handle_errors(
 378                                     &sess.parse_sess,
 379                                     lit.span,
 380                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 381                                 );
 382                                 continue 'outer;
 383                             }
 384                         }
 385                     }
 386
 387                     match (feature, since) {
 388                         (Some(feature), Some(since)) => {
 389                             let level = Stable { since };
 390                             if sym::stable == meta_name {
 391                                 stab = Some((Stability { level, feature }, attr.span));
 392                             } else {
 393                                 const_stab = Some((
 394                                     ConstStability { level, feature, promotable: false },
 395                                     attr.span,
 396                                 ));
 397                             }
 398                         }
 399                         (None, _) => {
 400                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingFeature);
 401                             continue;
 402                         }
 403                         _ => {
 404                             handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 405                             continue;
 406                         }
 407                     }
 408                 }
 409                 _ => unreachable!(),
 410             }
 411         }
 412     }
 413
 414     // Merge the const-unstable info into the stability info
 415     if promotable {
 416         if let Some((ref mut stab, _)) = const_stab {
 417             stab.promotable = promotable;
 418         } else {
 419             struct_span_err!(
 420                 diagnostic,
 421                 item_sp,
 422                 E0717,
 423                 "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
 424                 or a `rustc_const_stable` attribute"
 425             )
 426             .emit();
 427         }
 428     }
 429
 430     (stab, const_stab)
 431 }
 432
 433 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
 434     sess.first_attr_value_str_by_name(attrs, sym::crate_name)
 435 }
 436
 437 /// Tests if a cfg-pattern matches the cfg set
 438 pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) -> bool {
 439     eval_condition(cfg, sess, features, &mut |cfg| {
 440         try_gate_cfg(cfg, sess, features);
 441         let error = |span, msg| {
 442             sess.span_diagnostic.span_err(span, msg);
 443             true
 444         };
 445         if cfg.path.segments.len() != 1 {
 446             return error(cfg.path.span, "`cfg` predicate key must be an identifier");
 447         }
 448         match &cfg.kind {
 449             MetaItemKind::List(..) => {
 450                 error(cfg.span, "unexpected parentheses after `cfg` predicate key")
 451             }
 452             MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 453                 handle_errors(
 454                     sess,
 455                     lit.span,
 456                     AttrError::UnsupportedLiteral(
 457                         "literal in `cfg` predicate value must be a string",
 458                         lit.kind.is_bytestr(),
 459                     ),
 460                 );
 461                 true
 462             }
 463             MetaItemKind::NameValue(..) | MetaItemKind::Word => {
 464                 let name = cfg.ident().expect("multi-segment cfg predicate").name;
 465                 let value = cfg.value_str();
 466                 if let Some(names_valid) = &sess.check_config.names_valid {
 467                     if !names_valid.contains(&name) {
 468                         sess.buffer_lint(
 469                             UNEXPECTED_CFGS,
 470                             cfg.span,
 471                             CRATE_NODE_ID,
 472                             "unexpected `cfg` condition name",
 473                         );
 474                     }
 475                 }
 476                 if let Some(val) = value {
 477                     if let Some(values_valid) = &sess.check_config.values_valid {
 478                         if let Some(values) = values_valid.get(&name) {
 479                             if !values.contains(&val) {
 480                                 sess.buffer_lint(
 481                                     UNEXPECTED_CFGS,
 482                                     cfg.span,
 483                                     CRATE_NODE_ID,
 484                                     "unexpected `cfg` condition value",
 485                                 );
 486                             }
 487                         }
 488                     }
 489                 }
 490                 sess.config.contains(&(name, value))
 491             }
 492         }
 493     })
 494 }
 495
 496 fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
 497     let gate = find_gated_cfg(|sym| cfg.has_name(sym));
 498     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 499         gate_cfg(&gated_cfg, cfg.span, sess, feats);
 500     }
 501 }
 502
 503 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 504     let (cfg, feature, has_feature) = gated_cfg;
 505     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 506         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 507         feature_err(sess, *feature, cfg_span, &explain).emit();
 508     }
 509 }
 510
 511 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 512 struct Version {
 513     major: u16,
 514     minor: u16,
 515     patch: u16,
 516 }
 517
 518 fn parse_version(s: &str, allow_appendix: bool) -> Option<Version> {
 519     let mut components = s.split('-');
 520     let d = components.next()?;
 521     if !allow_appendix && components.next().is_some() {
 522         return None;
 523     }
 524     let mut digits = d.splitn(3, '.');
 525     let major = digits.next()?.parse().ok()?;
 526     let minor = digits.next()?.parse().ok()?;
 527     let patch = digits.next().unwrap_or("0").parse().ok()?;
 528     Some(Version { major, minor, patch })
 529 }
 530
 531 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 532 /// evaluate individual items.
 533 pub fn eval_condition(
 534     cfg: &ast::MetaItem,
 535     sess: &ParseSess,
 536     features: Option<&Features>,
 537     eval: &mut impl FnMut(&ast::MetaItem) -> bool,
 538 ) -> bool {
 539     match cfg.kind {
 540         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 541             try_gate_cfg(cfg, sess, features);
 542             let (min_version, span) = match &mis[..] {
 543                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 544                     (sym, span)
 545                 }
 546                 [
 547                     NestedMetaItem::Literal(Lit { span, .. })
 548                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
 549                 ] => {
 550                     sess.span_diagnostic
 551                         .struct_span_err(*span, "expected a version literal")
 552                         .emit();
 553                     return false;
 554                 }
 555                 [..] => {
 556                     sess.span_diagnostic
 557                         .struct_span_err(cfg.span, "expected single version literal")
 558                         .emit();
 559                     return false;
 560                 }
 561             };
 562             let min_version = match parse_version(min_version.as_str(), false) {
 563                 Some(ver) => ver,
 564                 None => {
 565                     sess.span_diagnostic
 566                         .struct_span_warn(
 567                             *span,
 568                             "unknown version literal format, assuming it refers to a future version",
 569                         )
 570                         .emit();
 571                     return false;
 572                 }
 573             };
 574             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
 575
 576             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
 577             if sess.assume_incomplete_release {
 578                 rustc_version > min_version
 579             } else {
 580                 rustc_version >= min_version
 581             }
 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(Copy, Debug, 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]) -> Option<(Deprecation, Span)> {
 652     find_deprecation_generic(sess, attrs.iter())
 653 }
 654
 655 fn find_deprecation_generic<'a, I>(sess: &Session, attrs_iter: I) -> Option<(Deprecation, Span)>
 656 where
 657     I: Iterator<Item = &'a Attribute>,
 658 {
 659     let mut depr: Option<(Deprecation, Span)> = None;
 660     let diagnostic = &sess.parse_sess.span_diagnostic;
 661
 662     'outer: for attr in attrs_iter {
 663         if !(attr.has_name(sym::deprecated) || attr.has_name(sym::rustc_deprecated)) {
 664             continue;
 665         }
 666
 667         if let Some((_, span)) = &depr {
 668             struct_span_err!(diagnostic, attr.span, E0550, "multiple deprecated attributes")
 669                 .span_label(attr.span, "repeated deprecation attribute")
 670                 .span_label(*span, "first deprecation attribute")
 671                 .emit();
 672             break;
 673         }
 674
 675         let meta = match attr.meta() {
 676             Some(meta) => meta,
 677             None => continue,
 678         };
 679         let mut since = None;
 680         let mut note = None;
 681         let mut suggestion = None;
 682         match &meta.kind {
 683             MetaItemKind::Word => {}
 684             MetaItemKind::NameValue(..) => note = meta.value_str(),
 685             MetaItemKind::List(list) => {
 686                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 687                     if item.is_some() {
 688                         handle_errors(
 689                             &sess.parse_sess,
 690                             meta.span,
 691                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 692                         );
 693                         return false;
 694                     }
 695                     if let Some(v) = meta.value_str() {
 696                         *item = Some(v);
 697                         true
 698                     } else {
 699                         if let Some(lit) = meta.name_value_literal() {
 700                             handle_errors(
 701                                 &sess.parse_sess,
 702                                 lit.span,
 703                                 AttrError::UnsupportedLiteral(
 704                                     "literal in `deprecated` \
 705                                     value must be a string",
 706                                     lit.kind.is_bytestr(),
 707                                 ),
 708                             );
 709                         } else {
 710                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 711                                 .emit();
 712                         }
 713
 714                         false
 715                     }
 716                 };
 717
 718                 for meta in list {
 719                     match meta {
 720                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 721                             sym::since => {
 722                                 if !get(mi, &mut since) {
 723                                     continue 'outer;
 724                                 }
 725                             }
 726                             sym::note if attr.has_name(sym::deprecated) => {
 727                                 if !get(mi, &mut note) {
 728                                     continue 'outer;
 729                                 }
 730                             }
 731                             sym::reason if attr.has_name(sym::rustc_deprecated) => {
 732                                 if !get(mi, &mut note) {
 733                                     continue 'outer;
 734                                 }
 735                             }
 736                             sym::suggestion if attr.has_name(sym::rustc_deprecated) => {
 737                                 if !get(mi, &mut suggestion) {
 738                                     continue 'outer;
 739                                 }
 740                             }
 741                             _ => {
 742                                 handle_errors(
 743                                     &sess.parse_sess,
 744                                     meta.span(),
 745                                     AttrError::UnknownMetaItem(
 746                                         pprust::path_to_string(&mi.path),
 747                                         if attr.has_name(sym::deprecated) {
 748                                             &["since", "note"]
 749                                         } else {
 750                                             &["since", "reason", "suggestion"]
 751                                         },
 752                                     ),
 753                                 );
 754                                 continue 'outer;
 755                             }
 756                         },
 757                         NestedMetaItem::Literal(lit) => {
 758                             handle_errors(
 759                                 &sess.parse_sess,
 760                                 lit.span,
 761                                 AttrError::UnsupportedLiteral(
 762                                     "item in `deprecated` must be a key/value pair",
 763                                     false,
 764                                 ),
 765                             );
 766                             continue 'outer;
 767                         }
 768                     }
 769                 }
 770             }
 771         }
 772
 773         if suggestion.is_some() && attr.has_name(sym::deprecated) {
 774             unreachable!("only allowed on rustc_deprecated")
 775         }
 776
 777         if attr.has_name(sym::rustc_deprecated) {
 778             if since.is_none() {
 779                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
 780                 continue;
 781             }
 782
 783             if note.is_none() {
 784                 struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'").emit();
 785                 continue;
 786             }
 787         }
 788
 789         let is_since_rustc_version = attr.has_name(sym::rustc_deprecated);
 790         depr = Some((Deprecation { since, note, suggestion, is_since_rustc_version }, attr.span));
 791     }
 792
 793     depr
 794 }
 795
 796 #[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
 797 pub enum ReprAttr {
 798     ReprInt(IntType),
 799     ReprC,
 800     ReprPacked(u32),
 801     ReprSimd,
 802     ReprTransparent,
 803     ReprAlign(u32),
 804     ReprNoNiche,
 805 }
 806
 807 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 808 #[derive(Encodable, Decodable, HashStable_Generic)]
 809 pub enum IntType {
 810     SignedInt(ast::IntTy),
 811     UnsignedInt(ast::UintTy),
 812 }
 813
 814 impl IntType {
 815     #[inline]
 816     pub fn is_signed(self) -> bool {
 817         use IntType::*;
 818
 819         match self {
 820             SignedInt(..) => true,
 821             UnsignedInt(..) => false,
 822         }
 823     }
 824 }
 825
 826 /// Parse #[repr(...)] forms.
 827 ///
 828 /// Valid repr contents: any of the primitive integral type names (see
 829 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 830 /// the same discriminant size that the corresponding C enum would or C
 831 /// structure layout, `packed` to remove padding, and `transparent` to delegate representation
 832 /// concerns to the only non-ZST field.
 833 pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
 834     use ReprAttr::*;
 835
 836     let mut acc = Vec::new();
 837     let diagnostic = &sess.parse_sess.span_diagnostic;
 838     if attr.has_name(sym::repr) {
 839         if let Some(items) = attr.meta_item_list() {
 840             for item in items {
 841                 let mut recognised = false;
 842                 if item.is_word() {
 843                     let hint = match item.name_or_empty() {
 844                         sym::C => Some(ReprC),
 845                         sym::packed => Some(ReprPacked(1)),
 846                         sym::simd => Some(ReprSimd),
 847                         sym::transparent => Some(ReprTransparent),
 848                         sym::no_niche => Some(ReprNoNiche),
 849                         sym::align => {
 850                             let mut err = struct_span_err!(
 851                                 diagnostic,
 852                                 item.span(),
 853                                 E0589,
 854                                 "invalid `repr(align)` attribute: `align` needs an argument"
 855                             );
 856                             err.span_suggestion(
 857                                 item.span(),
 858                                 "supply an argument here",
 859                                 "align(...)".to_string(),
 860                                 Applicability::HasPlaceholders,
 861                             );
 862                             err.emit();
 863                             recognised = true;
 864                             None
 865                         }
 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 mut literal_error = None;
 875                     if name == sym::align {
 876                         recognised = true;
 877                         match parse_alignment(&value.kind) {
 878                             Ok(literal) => acc.push(ReprAlign(literal)),
 879                             Err(message) => literal_error = Some(message),
 880                         };
 881                     } else if name == sym::packed {
 882                         recognised = true;
 883                         match parse_alignment(&value.kind) {
 884                             Ok(literal) => acc.push(ReprPacked(literal)),
 885                             Err(message) => literal_error = Some(message),
 886                         };
 887                     } else if matches!(name, sym::C | sym::simd | sym::transparent | sym::no_niche)
 888                         || int_type_of_word(name).is_some()
 889                     {
 890                         recognised = true;
 891                         struct_span_err!(
 892                                 diagnostic,
 893                                 item.span(),
 894                                 E0552,
 895                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
 896                                 name.to_ident_string(),
 897                             ).emit();
 898                     }
 899                     if let Some(literal_error) = literal_error {
 900                         struct_span_err!(
 901                             diagnostic,
 902                             item.span(),
 903                             E0589,
 904                             "invalid `repr({})` attribute: {}",
 905                             name.to_ident_string(),
 906                             literal_error
 907                         )
 908                         .emit();
 909                     }
 910                 } else if let Some(meta_item) = item.meta_item() {
 911                     if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 912                         if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
 913                             let name = meta_item.name_or_empty().to_ident_string();
 914                             recognised = true;
 915                             let mut err = struct_span_err!(
 916                                 diagnostic,
 917                                 item.span(),
 918                                 E0693,
 919                                 "incorrect `repr({})` attribute format",
 920                                 name,
 921                             );
 922                             match value.kind {
 923                                 ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 924                                     err.span_suggestion(
 925                                         item.span(),
 926                                         "use parentheses instead",
 927                                         format!("{}({})", name, int),
 928                                         Applicability::MachineApplicable,
 929                                     );
 930                                 }
 931                                 ast::LitKind::Str(s, _) => {
 932                                     err.span_suggestion(
 933                                         item.span(),
 934                                         "use parentheses instead",
 935                                         format!("{}({})", name, s),
 936                                         Applicability::MachineApplicable,
 937                                     );
 938                                 }
 939                                 _ => {}
 940                             }
 941                             err.emit();
 942                         } else {
 943                             if matches!(
 944                                 meta_item.name_or_empty(),
 945                                 sym::C | sym::simd | sym::transparent | sym::no_niche
 946                             ) || int_type_of_word(meta_item.name_or_empty()).is_some()
 947                             {
 948                                 recognised = true;
 949                                 struct_span_err!(
 950                                     diagnostic,
 951                                     meta_item.span,
 952                                     E0552,
 953                                     "invalid representation hint: `{}` does not take a value",
 954                                     meta_item.name_or_empty().to_ident_string(),
 955                                 )
 956                                 .emit();
 957                             }
 958                         }
 959                     } else if let MetaItemKind::List(_) = meta_item.kind {
 960                         if meta_item.has_name(sym::align) {
 961                             recognised = true;
 962                             struct_span_err!(
 963                                 diagnostic,
 964                                 meta_item.span,
 965                                 E0693,
 966                                 "incorrect `repr(align)` attribute format: \
 967                                  `align` takes exactly one argument in parentheses"
 968                             )
 969                             .emit();
 970                         } else if meta_item.has_name(sym::packed) {
 971                             recognised = true;
 972                             struct_span_err!(
 973                                 diagnostic,
 974                                 meta_item.span,
 975                                 E0552,
 976                                 "incorrect `repr(packed)` attribute format: \
 977                                  `packed` takes exactly one parenthesized argument, \
 978                                  or no parentheses at all"
 979                             )
 980                             .emit();
 981                         } else if matches!(
 982                             meta_item.name_or_empty(),
 983                             sym::C | sym::simd | sym::transparent | sym::no_niche
 984                         ) || int_type_of_word(meta_item.name_or_empty()).is_some()
 985                         {
 986                             recognised = true;
 987                             struct_span_err!(
 988                                 diagnostic,
 989                                 meta_item.span,
 990                                 E0552,
 991                                 "invalid representation hint: `{}` does not take a parenthesized argument list",
 992                                 meta_item.name_or_empty().to_ident_string(),
 993                             ).emit();
 994                         }
 995                     }
 996                 }
 997                 if !recognised {
 998                     // Not a word we recognize. This will be caught and reported by
 999                     // the `check_mod_attrs` pass, but this pass doesn't always run
1000                     // (e.g. if we only pretty-print the source), so we have to gate
1001                     // the `delay_span_bug` call as follows:
1002                     if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
1003                         diagnostic.delay_span_bug(item.span(), "unrecognized representation hint");
1004                     }
1005                 }
1006             }
1007         }
1008     }
1009     acc
1010 }
1011
1012 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1013     use IntType::*;
1014
1015     match s {
1016         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1017         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1018         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1019         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1020         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1021         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1022         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1023         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1024         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1025         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1026         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1027         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1028         _ => None,
1029     }
1030 }
1031
1032 pub enum TransparencyError {
1033     UnknownTransparency(Symbol, Span),
1034     MultipleTransparencyAttrs(Span, Span),
1035 }
1036
1037 pub fn find_transparency(
1038     attrs: &[Attribute],
1039     macro_rules: bool,
1040 ) -> (Transparency, Option<TransparencyError>) {
1041     let mut transparency = None;
1042     let mut error = None;
1043     for attr in attrs {
1044         if attr.has_name(sym::rustc_macro_transparency) {
1045             if let Some((_, old_span)) = transparency {
1046                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1047                 break;
1048             } else if let Some(value) = attr.value_str() {
1049                 transparency = Some((
1050                     match value {
1051                         sym::transparent => Transparency::Transparent,
1052                         sym::semitransparent => Transparency::SemiTransparent,
1053                         sym::opaque => Transparency::Opaque,
1054                         _ => {
1055                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1056                             continue;
1057                         }
1058                     },
1059                     attr.span,
1060                 ));
1061             }
1062         }
1063     }
1064     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1065     (transparency.map_or(fallback, |t| t.0), error)
1066 }
1067
1068 pub fn allow_internal_unstable<'a>(
1069     sess: &'a Session,
1070     attrs: &'a [Attribute],
1071 ) -> impl Iterator<Item = Symbol> + 'a {
1072     allow_unstable(sess, attrs, sym::allow_internal_unstable)
1073 }
1074
1075 pub fn rustc_allow_const_fn_unstable<'a>(
1076     sess: &'a Session,
1077     attrs: &'a [Attribute],
1078 ) -> impl Iterator<Item = Symbol> + 'a {
1079     allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
1080 }
1081
1082 fn allow_unstable<'a>(
1083     sess: &'a Session,
1084     attrs: &'a [Attribute],
1085     symbol: Symbol,
1086 ) -> impl Iterator<Item = Symbol> + 'a {
1087     let attrs = sess.filter_by_name(attrs, symbol);
1088     let list = attrs
1089         .filter_map(move |attr| {
1090             attr.meta_item_list().or_else(|| {
1091                 sess.diagnostic().span_err(
1092                     attr.span,
1093                     &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
1094                 );
1095                 None
1096             })
1097         })
1098         .flatten();
1099
1100     list.into_iter().filter_map(move |it| {
1101         let name = it.ident().map(|ident| ident.name);
1102         if name.is_none() {
1103             sess.diagnostic().span_err(
1104                 it.span(),
1105                 &format!("`{}` expects feature names", symbol.to_ident_string()),
1106             );
1107         }
1108         name
1109     })
1110 }
1111
1112 pub fn parse_alignment(node: &ast::LitKind) -> Result<u32, &'static str> {
1113     if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
1114         if literal.is_power_of_two() {
1115             // rustc_middle::ty::layout::Align restricts align to <= 2^29
1116             if *literal <= 1 << 29 { Ok(*literal as u32) } else { Err("larger than 2^29") }
1117         } else {
1118             Err("not a power of two")
1119         }
1120     } else {
1121         Err("not an unsuffixed integer")
1122     }
1123 }