compiler/rustc_attr/src/builtin.rs

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