src/librustc_attr/builtin.rs

   1 //! Parsing and validation of builtin attributes
   2
   3 use super::{find_by_name, mark_used};
   4
   5 use rustc_ast::ast::{self, Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem};
   6 use rustc_ast_pretty::pprust;
   7 use rustc_errors::{struct_span_err, Applicability, Handler};
   8 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
   9 use rustc_macros::HashStable_Generic;
  10 use rustc_session::parse::{feature_err, ParseSess};
  11 use rustc_span::hygiene::Transparency;
  12 use rustc_span::{symbol::sym, symbol::Symbol, Span};
  13 use std::num::NonZeroU32;
  14 use version_check::Version;
  15
  16 pub fn is_builtin_attr(attr: &Attribute) -> bool {
  17     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
  18 }
  19
  20 enum AttrError {
  21     MultipleItem(String),
  22     UnknownMetaItem(String, &'static [&'static str]),
  23     MissingSince,
  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::MissingFeature => {
  45             struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
  46         }
  47         AttrError::MultipleStabilityLevels => {
  48             struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
  49         }
  50         AttrError::UnsupportedLiteral(msg, is_bytestr) => {
  51             let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
  52             if is_bytestr {
  53                 if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
  54                     err.span_suggestion(
  55                         span,
  56                         "consider removing the prefix",
  57                         lint_str[1..].to_string(),
  58                         Applicability::MaybeIncorrect,
  59                     );
  60                 }
  61             }
  62             err.emit();
  63         }
  64     }
  65 }
  66
  67 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable)]
  68 pub enum InlineAttr {
  69     None,
  70     Hint,
  71     Always,
  72     Never,
  73 }
  74
  75 #[derive(Clone, RustcEncodable, RustcDecodable)]
  76 pub enum OptimizeAttr {
  77     None,
  78     Speed,
  79     Size,
  80 }
  81
  82 #[derive(Copy, Clone, PartialEq)]
  83 pub enum UnwindAttr {
  84     Allowed,
  85     Aborts,
  86 }
  87
  88 /// Determine what `#[unwind]` attribute is present in `attrs`, if any.
  89 pub fn find_unwind_attr(diagnostic: Option<&Handler>, attrs: &[Attribute]) -> Option<UnwindAttr> {
  90     attrs.iter().fold(None, |ia, attr| {
  91         if attr.check_name(sym::unwind) {
  92             if let Some(meta) = attr.meta() {
  93                 if let MetaItemKind::List(items) = meta.kind {
  94                     if items.len() == 1 {
  95                         if items[0].check_name(sym::allowed) {
  96                             return Some(UnwindAttr::Allowed);
  97                         } else if items[0].check_name(sym::aborts) {
  98                             return Some(UnwindAttr::Aborts);
  99                         }
 100                     }
 101
 102                     if let Some(d) = diagnostic {
 103                         struct_span_err!(d, attr.span, E0633, "malformed `unwind` attribute input")
 104                             .span_label(attr.span, "invalid argument")
 105                             .span_suggestions(
 106                                 attr.span,
 107                                 "the allowed arguments are `allowed` and `aborts`",
 108                                 (vec!["allowed", "aborts"])
 109                                     .into_iter()
 110                                     .map(|s| format!("#[unwind({})]", s)),
 111                                 Applicability::MachineApplicable,
 112                             )
 113                             .emit();
 114                     };
 115                 }
 116             }
 117         }
 118
 119         ia
 120     })
 121 }
 122
 123 /// Represents the following attributes:
 124 ///
 125 /// - `#[stable]`
 126 /// - `#[unstable]`
 127 /// - `#[rustc_deprecated]`
 128 #[derive(RustcEncodable, RustcDecodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 129 #[derive(HashStable_Generic)]
 130 pub struct Stability {
 131     pub level: StabilityLevel,
 132     pub feature: Symbol,
 133     pub rustc_depr: Option<RustcDeprecation>,
 134 }
 135
 136 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
 137 #[derive(RustcEncodable, RustcDecodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 138 #[derive(HashStable_Generic)]
 139 pub struct ConstStability {
 140     pub level: StabilityLevel,
 141     pub feature: Symbol,
 142     /// whether the function has a `#[rustc_promotable]` attribute
 143     pub promotable: bool,
 144     /// whether the function has a `#[rustc_allow_const_fn_ptr]` attribute
 145     pub allow_const_fn_ptr: bool,
 146 }
 147
 148 /// The available stability levels.
 149 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Copy, Clone, Debug, Eq, Hash)]
 150 #[derive(HashStable_Generic)]
 151 pub enum StabilityLevel {
 152     // Reason for the current stability level and the relevant rust-lang issue
 153     Unstable { reason: Option<Symbol>, issue: Option<NonZeroU32>, is_soft: bool },
 154     Stable { since: Symbol },
 155 }
 156
 157 impl StabilityLevel {
 158     pub fn is_unstable(&self) -> bool {
 159         if let StabilityLevel::Unstable { .. } = *self { true } else { false }
 160     }
 161     pub fn is_stable(&self) -> bool {
 162         if let StabilityLevel::Stable { .. } = *self { true } else { false }
 163     }
 164 }
 165
 166 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Copy, Clone, Debug, Eq, Hash)]
 167 #[derive(HashStable_Generic)]
 168 pub struct RustcDeprecation {
 169     pub since: Symbol,
 170     pub reason: Symbol,
 171     /// A text snippet used to completely replace any use of the deprecated item in an expression.
 172     pub suggestion: Option<Symbol>,
 173 }
 174
 175 /// Checks if `attrs` contains an attribute like `#![feature(feature_name)]`.
 176 /// This will not perform any "sanity checks" on the form of the attributes.
 177 pub fn contains_feature_attr(attrs: &[Attribute], feature_name: Symbol) -> bool {
 178     attrs.iter().any(|item| {
 179         item.check_name(sym::feature)
 180             && item
 181                 .meta_item_list()
 182                 .map(|list| list.iter().any(|mi| mi.is_word() && mi.check_name(feature_name)))
 183                 .unwrap_or(false)
 184     })
 185 }
 186
 187 /// Collects stability info from all stability attributes in `attrs`.
 188 /// Returns `None` if no stability attributes are found.
 189 pub fn find_stability(
 190     sess: &ParseSess,
 191     attrs: &[Attribute],
 192     item_sp: Span,
 193 ) -> (Option<Stability>, Option<ConstStability>) {
 194     find_stability_generic(sess, attrs.iter(), item_sp)
 195 }
 196
 197 fn find_stability_generic<'a, I>(
 198     sess: &ParseSess,
 199     attrs_iter: I,
 200     item_sp: Span,
 201 ) -> (Option<Stability>, Option<ConstStability>)
 202 where
 203     I: Iterator<Item = &'a Attribute>,
 204 {
 205     use StabilityLevel::*;
 206
 207     let mut stab: Option<Stability> = None;
 208     let mut rustc_depr: Option<RustcDeprecation> = None;
 209     let mut const_stab: Option<ConstStability> = None;
 210     let mut promotable = false;
 211     let mut allow_const_fn_ptr = false;
 212     let diagnostic = &sess.span_diagnostic;
 213
 214     'outer: for attr in attrs_iter {
 215         if ![
 216             sym::rustc_deprecated,
 217             sym::rustc_const_unstable,
 218             sym::rustc_const_stable,
 219             sym::unstable,
 220             sym::stable,
 221             sym::rustc_promotable,
 222             sym::rustc_allow_const_fn_ptr,
 223         ]
 224         .iter()
 225         .any(|&s| attr.has_name(s))
 226         {
 227             continue; // not a stability level
 228         }
 229
 230         mark_used(attr);
 231
 232         let meta = attr.meta();
 233
 234         if attr.has_name(sym::rustc_promotable) {
 235             promotable = true;
 236         }
 237         if attr.has_name(sym::rustc_allow_const_fn_ptr) {
 238             allow_const_fn_ptr = true;
 239         }
 240         // attributes with data
 241         else if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta {
 242             let meta = meta.as_ref().unwrap();
 243             let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 244                 if item.is_some() {
 245                     handle_errors(
 246                         sess,
 247                         meta.span,
 248                         AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 249                     );
 250                     return false;
 251                 }
 252                 if let Some(v) = meta.value_str() {
 253                     *item = Some(v);
 254                     true
 255                 } else {
 256                     struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
 257                     false
 258                 }
 259             };
 260
 261             macro_rules! get_meta {
 262                 ($($name:ident),+) => {
 263                     $(
 264                         let mut $name = None;
 265                     )+
 266                     for meta in metas {
 267                         if let Some(mi) = meta.meta_item() {
 268                             match mi.name_or_empty() {
 269                                 $(
 270                                     sym::$name => if !get(mi, &mut $name) { continue 'outer },
 271                                 )+
 272                                 _ => {
 273                                     let expected = &[ $( stringify!($name) ),+ ];
 274                                     handle_errors(
 275                                         sess,
 276                                         mi.span,
 277                                         AttrError::UnknownMetaItem(
 278                                             pprust::path_to_string(&mi.path),
 279                                             expected,
 280                                         ),
 281                                     );
 282                                     continue 'outer
 283                                 }
 284                             }
 285                         } else {
 286                             handle_errors(
 287                                 sess,
 288                                 meta.span(),
 289                                 AttrError::UnsupportedLiteral(
 290                                     "unsupported literal",
 291                                     false,
 292                                 ),
 293                             );
 294                             continue 'outer
 295                         }
 296                     }
 297                 }
 298             }
 299
 300             let meta_name = meta.name_or_empty();
 301             match meta_name {
 302                 sym::rustc_deprecated => {
 303                     if rustc_depr.is_some() {
 304                         struct_span_err!(
 305                             diagnostic,
 306                             item_sp,
 307                             E0540,
 308                             "multiple rustc_deprecated attributes"
 309                         )
 310                         .emit();
 311                         continue 'outer;
 312                     }
 313
 314                     get_meta!(since, reason, suggestion);
 315
 316                     match (since, reason) {
 317                         (Some(since), Some(reason)) => {
 318                             rustc_depr = Some(RustcDeprecation { since, reason, suggestion })
 319                         }
 320                         (None, _) => {
 321                             handle_errors(sess, attr.span, AttrError::MissingSince);
 322                             continue;
 323                         }
 324                         _ => {
 325                             struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'")
 326                                 .emit();
 327                             continue;
 328                         }
 329                     }
 330                 }
 331                 sym::rustc_const_unstable | sym::unstable => {
 332                     if meta_name == sym::unstable && stab.is_some() {
 333                         handle_errors(sess, attr.span, AttrError::MultipleStabilityLevels);
 334                         break;
 335                     } else if meta_name == sym::rustc_const_unstable && const_stab.is_some() {
 336                         handle_errors(sess, attr.span, AttrError::MultipleStabilityLevels);
 337                         break;
 338                     }
 339
 340                     let mut feature = None;
 341                     let mut reason = None;
 342                     let mut issue = None;
 343                     let mut issue_num = None;
 344                     let mut is_soft = false;
 345                     for meta in metas {
 346                         if let Some(mi) = meta.meta_item() {
 347                             match mi.name_or_empty() {
 348                                 sym::feature => {
 349                                     if !get(mi, &mut feature) {
 350                                         continue 'outer;
 351                                     }
 352                                 }
 353                                 sym::reason => {
 354                                     if !get(mi, &mut reason) {
 355                                         continue 'outer;
 356                                     }
 357                                 }
 358                                 sym::issue => {
 359                                     if !get(mi, &mut issue) {
 360                                         continue 'outer;
 361                                     }
 362
 363                                     // These unwraps are safe because `get` ensures the meta item
 364                                     // is a name/value pair string literal.
 365                                     issue_num = match &*issue.unwrap().as_str() {
 366                                         "none" => None,
 367                                         issue => {
 368                                             let emit_diag = |msg: &str| {
 369                                                 struct_span_err!(
 370                                                     diagnostic,
 371                                                     mi.span,
 372                                                     E0545,
 373                                                     "`issue` must be a non-zero numeric string \
 374                                                     or \"none\"",
 375                                                 )
 376                                                 .span_label(
 377                                                     mi.name_value_literal().unwrap().span,
 378                                                     msg,
 379                                                 )
 380                                                 .emit();
 381                                             };
 382                                             match issue.parse() {
 383                                                 Ok(num) if num == 0 => {
 384                                                     emit_diag(
 385                                                         "`issue` must not be \"0\", \
 386                                                         use \"none\" instead",
 387                                                     );
 388                                                     continue 'outer;
 389                                                 }
 390                                                 Ok(num) => NonZeroU32::new(num),
 391                                                 Err(err) => {
 392                                                     emit_diag(&err.to_string());
 393                                                     continue 'outer;
 394                                                 }
 395                                             }
 396                                         }
 397                                     };
 398                                 }
 399                                 sym::soft => {
 400                                     if !mi.is_word() {
 401                                         let msg = "`soft` should not have any arguments";
 402                                         sess.span_diagnostic.span_err(mi.span, msg);
 403                                     }
 404                                     is_soft = true;
 405                                 }
 406                                 _ => {
 407                                     handle_errors(
 408                                         sess,
 409                                         meta.span(),
 410                                         AttrError::UnknownMetaItem(
 411                                             pprust::path_to_string(&mi.path),
 412                                             &["feature", "reason", "issue", "soft"],
 413                                         ),
 414                                     );
 415                                     continue 'outer;
 416                                 }
 417                             }
 418                         } else {
 419                             handle_errors(
 420                                 sess,
 421                                 meta.span(),
 422                                 AttrError::UnsupportedLiteral("unsupported literal", false),
 423                             );
 424                             continue 'outer;
 425                         }
 426                     }
 427
 428                     match (feature, reason, issue) {
 429                         (Some(feature), reason, Some(_)) => {
 430                             let level = Unstable { reason, issue: issue_num, is_soft };
 431                             if sym::unstable == meta_name {
 432                                 stab = Some(Stability { level, feature, rustc_depr: None });
 433                             } else {
 434                                 const_stab = Some(ConstStability {
 435                                     level,
 436                                     feature,
 437                                     promotable: false,
 438                                     allow_const_fn_ptr: false,
 439                                 });
 440                             }
 441                         }
 442                         (None, _, _) => {
 443                             handle_errors(sess, attr.span, AttrError::MissingFeature);
 444                             continue;
 445                         }
 446                         _ => {
 447                             struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
 448                                 .emit();
 449                             continue;
 450                         }
 451                     }
 452                 }
 453                 sym::rustc_const_stable | sym::stable => {
 454                     if meta_name == sym::stable && stab.is_some() {
 455                         handle_errors(sess, attr.span, AttrError::MultipleStabilityLevels);
 456                         break;
 457                     } else if meta_name == sym::rustc_const_stable && const_stab.is_some() {
 458                         handle_errors(sess, attr.span, AttrError::MultipleStabilityLevels);
 459                         break;
 460                     }
 461
 462                     let mut feature = None;
 463                     let mut since = None;
 464                     for meta in metas {
 465                         match meta {
 466                             NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 467                                 sym::feature => {
 468                                     if !get(mi, &mut feature) {
 469                                         continue 'outer;
 470                                     }
 471                                 }
 472                                 sym::since => {
 473                                     if !get(mi, &mut since) {
 474                                         continue 'outer;
 475                                     }
 476                                 }
 477                                 _ => {
 478                                     handle_errors(
 479                                         sess,
 480                                         meta.span(),
 481                                         AttrError::UnknownMetaItem(
 482                                             pprust::path_to_string(&mi.path),
 483                                             &["since", "note"],
 484                                         ),
 485                                     );
 486                                     continue 'outer;
 487                                 }
 488                             },
 489                             NestedMetaItem::Literal(lit) => {
 490                                 handle_errors(
 491                                     sess,
 492                                     lit.span,
 493                                     AttrError::UnsupportedLiteral("unsupported literal", false),
 494                                 );
 495                                 continue 'outer;
 496                             }
 497                         }
 498                     }
 499
 500                     match (feature, since) {
 501                         (Some(feature), Some(since)) => {
 502                             let level = Stable { since };
 503                             if sym::stable == meta_name {
 504                                 stab = Some(Stability { level, feature, rustc_depr: None });
 505                             } else {
 506                                 const_stab = Some(ConstStability {
 507                                     level,
 508                                     feature,
 509                                     promotable: false,
 510                                     allow_const_fn_ptr: false,
 511                                 });
 512                             }
 513                         }
 514                         (None, _) => {
 515                             handle_errors(sess, attr.span, AttrError::MissingFeature);
 516                             continue;
 517                         }
 518                         _ => {
 519                             handle_errors(sess, attr.span, AttrError::MissingSince);
 520                             continue;
 521                         }
 522                     }
 523                 }
 524                 _ => unreachable!(),
 525             }
 526         }
 527     }
 528
 529     // Merge the deprecation info into the stability info
 530     if let Some(rustc_depr) = rustc_depr {
 531         if let Some(ref mut stab) = stab {
 532             stab.rustc_depr = Some(rustc_depr);
 533         } else {
 534             struct_span_err!(
 535                 diagnostic,
 536                 item_sp,
 537                 E0549,
 538                 "rustc_deprecated attribute must be paired with \
 539                        either stable or unstable attribute"
 540             )
 541             .emit();
 542         }
 543     }
 544
 545     // Merge the const-unstable info into the stability info
 546     if promotable || allow_const_fn_ptr {
 547         if let Some(ref mut stab) = const_stab {
 548             stab.promotable = promotable;
 549             stab.allow_const_fn_ptr = allow_const_fn_ptr;
 550         } else {
 551             struct_span_err!(
 552                 diagnostic,
 553                 item_sp,
 554                 E0717,
 555                 "rustc_promotable and rustc_allow_const_fn_ptr attributes \
 556                       must be paired with either a rustc_const_unstable or a rustc_const_stable \
 557                       attribute"
 558             )
 559             .emit();
 560         }
 561     }
 562
 563     (stab, const_stab)
 564 }
 565
 566 pub fn find_crate_name(attrs: &[Attribute]) -> Option<Symbol> {
 567     super::first_attr_value_str_by_name(attrs, sym::crate_name)
 568 }
 569
 570 /// Tests if a cfg-pattern matches the cfg set
 571 pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) -> bool {
 572     eval_condition(cfg, sess, features, &mut |cfg| {
 573         try_gate_cfg(cfg, sess, features);
 574         let error = |span, msg| {
 575             sess.span_diagnostic.span_err(span, msg);
 576             true
 577         };
 578         if cfg.path.segments.len() != 1 {
 579             return error(cfg.path.span, "`cfg` predicate key must be an identifier");
 580         }
 581         match &cfg.kind {
 582             MetaItemKind::List(..) => {
 583                 error(cfg.span, "unexpected parentheses after `cfg` predicate key")
 584             }
 585             MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
 586                 handle_errors(
 587                     sess,
 588                     lit.span,
 589                     AttrError::UnsupportedLiteral(
 590                         "literal in `cfg` predicate value must be a string",
 591                         lit.kind.is_bytestr(),
 592                     ),
 593                 );
 594                 true
 595             }
 596             MetaItemKind::NameValue(..) | MetaItemKind::Word => {
 597                 let ident = cfg.ident().expect("multi-segment cfg predicate");
 598                 sess.config.contains(&(ident.name, cfg.value_str()))
 599             }
 600         }
 601     })
 602 }
 603
 604 fn try_gate_cfg(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) {
 605     let gate = find_gated_cfg(|sym| cfg.check_name(sym));
 606     if let (Some(feats), Some(gated_cfg)) = (features, gate) {
 607         gate_cfg(&gated_cfg, cfg.span, sess, feats);
 608     }
 609 }
 610
 611 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &ParseSess, features: &Features) {
 612     let (cfg, feature, has_feature) = gated_cfg;
 613     if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
 614         let explain = format!("`cfg({})` is experimental and subject to change", cfg);
 615         feature_err(sess, *feature, cfg_span, &explain).emit();
 616     }
 617 }
 618
 619 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 620 /// evaluate individual items.
 621 pub fn eval_condition(
 622     cfg: &ast::MetaItem,
 623     sess: &ParseSess,
 624     features: Option<&Features>,
 625     eval: &mut impl FnMut(&ast::MetaItem) -> bool,
 626 ) -> bool {
 627     match cfg.kind {
 628         ast::MetaItemKind::List(ref mis) if cfg.name_or_empty() == sym::version => {
 629             try_gate_cfg(cfg, sess, features);
 630             let (min_version, span) = match &mis[..] {
 631                 [NestedMetaItem::Literal(Lit { kind: LitKind::Str(sym, ..), span, .. })] => {
 632                     (sym, span)
 633                 }
 634                 [NestedMetaItem::Literal(Lit { span, .. })
 635                 | NestedMetaItem::MetaItem(MetaItem { span, .. })] => {
 636                     sess.span_diagnostic
 637                         .struct_span_err(*span, "expected a version literal")
 638                         .emit();
 639                     return false;
 640                 }
 641                 [..] => {
 642                     sess.span_diagnostic
 643                         .struct_span_err(cfg.span, "expected single version literal")
 644                         .emit();
 645                     return false;
 646                 }
 647             };
 648             let min_version = match Version::parse(&min_version.as_str()) {
 649                 Some(ver) => ver,
 650                 None => {
 651                     sess.span_diagnostic.struct_span_err(*span, "invalid version literal").emit();
 652                     return false;
 653                 }
 654             };
 655             let channel = env!("CFG_RELEASE_CHANNEL");
 656             let nightly = channel == "nightly" || channel == "dev";
 657             let rustc_version = Version::parse(env!("CFG_RELEASE")).unwrap();
 658
 659             // See https://github.com/rust-lang/rust/issues/64796#issuecomment-625474439 for details
 660             if nightly { rustc_version > min_version } else { rustc_version >= min_version }
 661         }
 662         ast::MetaItemKind::List(ref mis) => {
 663             for mi in mis.iter() {
 664                 if !mi.is_meta_item() {
 665                     handle_errors(
 666                         sess,
 667                         mi.span(),
 668                         AttrError::UnsupportedLiteral("unsupported literal", false),
 669                     );
 670                     return false;
 671                 }
 672             }
 673
 674             // The unwraps below may look dangerous, but we've already asserted
 675             // that they won't fail with the loop above.
 676             match cfg.name_or_empty() {
 677                 sym::any => mis
 678                     .iter()
 679                     .any(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 680                 sym::all => mis
 681                     .iter()
 682                     .all(|mi| eval_condition(mi.meta_item().unwrap(), sess, features, eval)),
 683                 sym::not => {
 684                     if mis.len() != 1 {
 685                         struct_span_err!(
 686                             sess.span_diagnostic,
 687                             cfg.span,
 688                             E0536,
 689                             "expected 1 cfg-pattern"
 690                         )
 691                         .emit();
 692                         return false;
 693                     }
 694
 695                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
 696                 }
 697                 _ => {
 698                     struct_span_err!(
 699                         sess.span_diagnostic,
 700                         cfg.span,
 701                         E0537,
 702                         "invalid predicate `{}`",
 703                         pprust::path_to_string(&cfg.path)
 704                     )
 705                     .emit();
 706                     false
 707                 }
 708             }
 709         }
 710         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => eval(cfg),
 711     }
 712 }
 713
 714 #[derive(RustcEncodable, RustcDecodable, Clone, HashStable_Generic)]
 715 pub struct Deprecation {
 716     pub since: Option<Symbol>,
 717     pub note: Option<Symbol>,
 718 }
 719
 720 /// Finds the deprecation attribute. `None` if none exists.
 721 pub fn find_deprecation(
 722     sess: &ParseSess,
 723     attrs: &[Attribute],
 724     item_sp: Span,
 725 ) -> Option<Deprecation> {
 726     find_deprecation_generic(sess, attrs.iter(), item_sp)
 727 }
 728
 729 fn find_deprecation_generic<'a, I>(
 730     sess: &ParseSess,
 731     attrs_iter: I,
 732     item_sp: Span,
 733 ) -> Option<Deprecation>
 734 where
 735     I: Iterator<Item = &'a Attribute>,
 736 {
 737     let mut depr: Option<Deprecation> = None;
 738     let diagnostic = &sess.span_diagnostic;
 739
 740     'outer: for attr in attrs_iter {
 741         if !attr.check_name(sym::deprecated) {
 742             continue;
 743         }
 744
 745         if depr.is_some() {
 746             struct_span_err!(diagnostic, item_sp, E0550, "multiple deprecated attributes").emit();
 747             break;
 748         }
 749
 750         let meta = match attr.meta() {
 751             Some(meta) => meta,
 752             None => continue,
 753         };
 754         depr = match &meta.kind {
 755             MetaItemKind::Word => Some(Deprecation { since: None, note: None }),
 756             MetaItemKind::NameValue(..) => {
 757                 meta.value_str().map(|note| Deprecation { since: None, note: Some(note) })
 758             }
 759             MetaItemKind::List(list) => {
 760                 let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
 761                     if item.is_some() {
 762                         handle_errors(
 763                             sess,
 764                             meta.span,
 765                             AttrError::MultipleItem(pprust::path_to_string(&meta.path)),
 766                         );
 767                         return false;
 768                     }
 769                     if let Some(v) = meta.value_str() {
 770                         *item = Some(v);
 771                         true
 772                     } else {
 773                         if let Some(lit) = meta.name_value_literal() {
 774                             handle_errors(
 775                                 sess,
 776                                 lit.span,
 777                                 AttrError::UnsupportedLiteral(
 778                                     "literal in `deprecated` \
 779                                     value must be a string",
 780                                     lit.kind.is_bytestr(),
 781                                 ),
 782                             );
 783                         } else {
 784                             struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
 785                                 .emit();
 786                         }
 787
 788                         false
 789                     }
 790                 };
 791
 792                 let mut since = None;
 793                 let mut note = None;
 794                 for meta in list {
 795                     match meta {
 796                         NestedMetaItem::MetaItem(mi) => match mi.name_or_empty() {
 797                             sym::since => {
 798                                 if !get(mi, &mut since) {
 799                                     continue 'outer;
 800                                 }
 801                             }
 802                             sym::note => {
 803                                 if !get(mi, &mut note) {
 804                                     continue 'outer;
 805                                 }
 806                             }
 807                             _ => {
 808                                 handle_errors(
 809                                     sess,
 810                                     meta.span(),
 811                                     AttrError::UnknownMetaItem(
 812                                         pprust::path_to_string(&mi.path),
 813                                         &["since", "note"],
 814                                     ),
 815                                 );
 816                                 continue 'outer;
 817                             }
 818                         },
 819                         NestedMetaItem::Literal(lit) => {
 820                             handle_errors(
 821                                 sess,
 822                                 lit.span,
 823                                 AttrError::UnsupportedLiteral(
 824                                     "item in `deprecated` must be a key/value pair",
 825                                     false,
 826                                 ),
 827                             );
 828                             continue 'outer;
 829                         }
 830                     }
 831                 }
 832
 833                 Some(Deprecation { since, note })
 834             }
 835         };
 836     }
 837
 838     depr
 839 }
 840
 841 #[derive(PartialEq, Debug, RustcEncodable, RustcDecodable, Copy, Clone)]
 842 pub enum ReprAttr {
 843     ReprInt(IntType),
 844     ReprC,
 845     ReprPacked(u32),
 846     ReprSimd,
 847     ReprTransparent,
 848     ReprAlign(u32),
 849     ReprNoNiche,
 850 }
 851
 852 #[derive(Eq, PartialEq, Debug, RustcEncodable, RustcDecodable, Copy, Clone, HashStable_Generic)]
 853 pub enum IntType {
 854     SignedInt(ast::IntTy),
 855     UnsignedInt(ast::UintTy),
 856 }
 857
 858 impl IntType {
 859     #[inline]
 860     pub fn is_signed(self) -> bool {
 861         use IntType::*;
 862
 863         match self {
 864             SignedInt(..) => true,
 865             UnsignedInt(..) => false,
 866         }
 867     }
 868 }
 869
 870 /// Parse #[repr(...)] forms.
 871 ///
 872 /// Valid repr contents: any of the primitive integral type names (see
 873 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 874 /// the same discriminant size that the corresponding C enum would or C
 875 /// structure layout, `packed` to remove padding, and `transparent` to elegate representation
 876 /// concerns to the only non-ZST field.
 877 pub fn find_repr_attrs(sess: &ParseSess, attr: &Attribute) -> Vec<ReprAttr> {
 878     use ReprAttr::*;
 879
 880     let mut acc = Vec::new();
 881     let diagnostic = &sess.span_diagnostic;
 882     if attr.has_name(sym::repr) {
 883         if let Some(items) = attr.meta_item_list() {
 884             mark_used(attr);
 885             for item in items {
 886                 if !item.is_meta_item() {
 887                     handle_errors(
 888                         sess,
 889                         item.span(),
 890                         AttrError::UnsupportedLiteral(
 891                             "meta item in `repr` must be an identifier",
 892                             false,
 893                         ),
 894                     );
 895                     continue;
 896                 }
 897
 898                 let mut recognised = false;
 899                 if item.is_word() {
 900                     let hint = match item.name_or_empty() {
 901                         sym::C => Some(ReprC),
 902                         sym::packed => Some(ReprPacked(1)),
 903                         sym::simd => Some(ReprSimd),
 904                         sym::transparent => Some(ReprTransparent),
 905                         sym::no_niche => Some(ReprNoNiche),
 906                         name => int_type_of_word(name).map(ReprInt),
 907                     };
 908
 909                     if let Some(h) = hint {
 910                         recognised = true;
 911                         acc.push(h);
 912                     }
 913                 } else if let Some((name, value)) = item.name_value_literal() {
 914                     let parse_alignment = |node: &ast::LitKind| -> Result<u32, &'static str> {
 915                         if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
 916                             if literal.is_power_of_two() {
 917                                 // rustc_middle::ty::layout::Align restricts align to <= 2^29
 918                                 if *literal <= 1 << 29 {
 919                                     Ok(*literal as u32)
 920                                 } else {
 921                                     Err("larger than 2^29")
 922                                 }
 923                             } else {
 924                                 Err("not a power of two")
 925                             }
 926                         } else {
 927                             Err("not an unsuffixed integer")
 928                         }
 929                     };
 930
 931                     let mut literal_error = None;
 932                     if name == sym::align {
 933                         recognised = true;
 934                         match parse_alignment(&value.kind) {
 935                             Ok(literal) => acc.push(ReprAlign(literal)),
 936                             Err(message) => literal_error = Some(message),
 937                         };
 938                     } else if name == sym::packed {
 939                         recognised = true;
 940                         match parse_alignment(&value.kind) {
 941                             Ok(literal) => acc.push(ReprPacked(literal)),
 942                             Err(message) => literal_error = Some(message),
 943                         };
 944                     }
 945                     if let Some(literal_error) = literal_error {
 946                         struct_span_err!(
 947                             diagnostic,
 948                             item.span(),
 949                             E0589,
 950                             "invalid `repr(align)` attribute: {}",
 951                             literal_error
 952                         )
 953                         .emit();
 954                     }
 955                 } else {
 956                     if let Some(meta_item) = item.meta_item() {
 957                         if meta_item.check_name(sym::align) {
 958                             if let MetaItemKind::NameValue(ref value) = meta_item.kind {
 959                                 recognised = true;
 960                                 let mut err = struct_span_err!(
 961                                     diagnostic,
 962                                     item.span(),
 963                                     E0693,
 964                                     "incorrect `repr(align)` attribute format"
 965                                 );
 966                                 match value.kind {
 967                                     ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
 968                                         err.span_suggestion(
 969                                             item.span(),
 970                                             "use parentheses instead",
 971                                             format!("align({})", int),
 972                                             Applicability::MachineApplicable,
 973                                         );
 974                                     }
 975                                     ast::LitKind::Str(s, _) => {
 976                                         err.span_suggestion(
 977                                             item.span(),
 978                                             "use parentheses instead",
 979                                             format!("align({})", s),
 980                                             Applicability::MachineApplicable,
 981                                         );
 982                                     }
 983                                     _ => {}
 984                                 }
 985                                 err.emit();
 986                             }
 987                         }
 988                     }
 989                 }
 990                 if !recognised {
 991                     // Not a word we recognize
 992                     struct_span_err!(
 993                         diagnostic,
 994                         item.span(),
 995                         E0552,
 996                         "unrecognized representation hint"
 997                     )
 998                     .emit();
 999                 }
1000             }
1001         }
1002     }
1003     acc
1004 }
1005
1006 fn int_type_of_word(s: Symbol) -> Option<IntType> {
1007     use IntType::*;
1008
1009     match s {
1010         sym::i8 => Some(SignedInt(ast::IntTy::I8)),
1011         sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
1012         sym::i16 => Some(SignedInt(ast::IntTy::I16)),
1013         sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
1014         sym::i32 => Some(SignedInt(ast::IntTy::I32)),
1015         sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
1016         sym::i64 => Some(SignedInt(ast::IntTy::I64)),
1017         sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
1018         sym::i128 => Some(SignedInt(ast::IntTy::I128)),
1019         sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
1020         sym::isize => Some(SignedInt(ast::IntTy::Isize)),
1021         sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
1022         _ => None,
1023     }
1024 }
1025
1026 pub enum TransparencyError {
1027     UnknownTransparency(Symbol, Span),
1028     MultipleTransparencyAttrs(Span, Span),
1029 }
1030
1031 pub fn find_transparency(
1032     attrs: &[Attribute],
1033     macro_rules: bool,
1034 ) -> (Transparency, Option<TransparencyError>) {
1035     let mut transparency = None;
1036     let mut error = None;
1037     for attr in attrs {
1038         if attr.check_name(sym::rustc_macro_transparency) {
1039             if let Some((_, old_span)) = transparency {
1040                 error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
1041                 break;
1042             } else if let Some(value) = attr.value_str() {
1043                 transparency = Some((
1044                     match &*value.as_str() {
1045                         "transparent" => Transparency::Transparent,
1046                         "semitransparent" => Transparency::SemiTransparent,
1047                         "opaque" => Transparency::Opaque,
1048                         _ => {
1049                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
1050                             continue;
1051                         }
1052                     },
1053                     attr.span,
1054                 ));
1055             }
1056         }
1057     }
1058     let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
1059     (transparency.map_or(fallback, |t| t.0), error)
1060 }
1061
1062 pub fn allow_internal_unstable<'a>(
1063     attrs: &[Attribute],
1064     diag: &'a rustc_errors::Handler,
1065 ) -> Option<impl Iterator<Item = Symbol> + 'a> {
1066     let attr = find_by_name(attrs, sym::allow_internal_unstable)?;
1067     let list = attr.meta_item_list().or_else(|| {
1068         diag.span_err(attr.span, "allow_internal_unstable expects list of feature names");
1069         None
1070     })?;
1071     Some(list.into_iter().filter_map(move |it| {
1072         let name = it.ident().map(|ident| ident.name);
1073         if name.is_none() {
1074             diag.span_err(it.span(), "`allow_internal_unstable` expects feature names");
1075         }
1076         name
1077     }))
1078 }