compiler/rustc_attr/src/builtin.rs

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