compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::{AstConv, SizedByDefault};
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind, Res};
  31 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::map::blocks::FnLikeNode;
  36 use rustc_middle::hir::map::Map;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
  45 use rustc_session::config::SanitizerSet;
  46 use rustc_session::lint;
  47 use rustc_session::parse::feature_err;
  48 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  49 use rustc_span::{Span, DUMMY_SP};
  50 use rustc_target::spec::abi;
  51 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  52
  53 use std::ops::ControlFlow;
  54
  55 mod item_bounds;
  56 mod type_of;
  57
  58 struct OnlySelfBounds(bool);
  59
  60 ///////////////////////////////////////////////////////////////////////////
  61 // Main entry point
  62
  63 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  64     tcx.hir().visit_item_likes_in_module(
  65         module_def_id,
  66         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  67     );
  68 }
  69
  70 pub fn provide(providers: &mut Providers) {
  71     *providers = Providers {
  72         opt_const_param_of: type_of::opt_const_param_of,
  73         type_of: type_of::type_of,
  74         item_bounds: item_bounds::item_bounds,
  75         explicit_item_bounds: item_bounds::explicit_item_bounds,
  76         generics_of,
  77         predicates_of,
  78         predicates_defined_on,
  79         projection_ty_from_predicates,
  80         explicit_predicates_of,
  81         super_predicates_of,
  82         trait_explicit_predicates_and_bounds,
  83         type_param_predicates,
  84         trait_def,
  85         adt_def,
  86         fn_sig,
  87         impl_trait_ref,
  88         impl_polarity,
  89         is_foreign_item,
  90         static_mutability,
  91         generator_kind,
  92         codegen_fn_attrs,
  93         collect_mod_item_types,
  94         ..*providers
  95     };
  96 }
  97
  98 ///////////////////////////////////////////////////////////////////////////
  99
 100 /// Context specific to some particular item. This is what implements
 101 /// `AstConv`. It has information about the predicates that are defined
 102 /// on the trait. Unfortunately, this predicate information is
 103 /// available in various different forms at various points in the
 104 /// process. So we can't just store a pointer to e.g., the AST or the
 105 /// parsed ty form, we have to be more flexible. To this end, the
 106 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 107 /// `get_type_parameter_bounds` requests, drawing the information from
 108 /// the AST (`hir::Generics`), recursively.
 109 pub struct ItemCtxt<'tcx> {
 110     tcx: TyCtxt<'tcx>,
 111     item_def_id: DefId,
 112 }
 113
 114 ///////////////////////////////////////////////////////////////////////////
 115
 116 #[derive(Default)]
 117 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 118
 119 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 120     type Map = intravisit::ErasedMap<'v>;
 121
 122     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 123         NestedVisitorMap::None
 124     }
 125     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 126         if let hir::TyKind::Infer = t.kind {
 127             self.0.push(t.span);
 128         }
 129         intravisit::walk_ty(self, t)
 130     }
 131 }
 132
 133 struct CollectItemTypesVisitor<'tcx> {
 134     tcx: TyCtxt<'tcx>,
 135 }
 136
 137 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 138 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 139 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 140 crate fn placeholder_type_error(
 141     tcx: TyCtxt<'tcx>,
 142     span: Option<Span>,
 143     generics: &[hir::GenericParam<'_>],
 144     placeholder_types: Vec<Span>,
 145     suggest: bool,
 146 ) {
 147     if placeholder_types.is_empty() {
 148         return;
 149     }
 150
 151     let type_name = generics.next_type_param_name(None);
 152     let mut sugg: Vec<_> =
 153         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 154
 155     if generics.is_empty() {
 156         if let Some(span) = span {
 157             sugg.push((span, format!("<{}>", type_name)));
 158         }
 159     } else if let Some(arg) = generics.iter().find(|arg| match arg.name {
 160         hir::ParamName::Plain(Ident { name: kw::Underscore, .. }) => true,
 161         _ => false,
 162     }) {
 163         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 164         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 165         sugg.push((arg.span, (*type_name).to_string()));
 166     } else {
 167         let last = generics.iter().last().unwrap();
 168         sugg.push((
 169             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 170             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 171             format!(", {}", type_name),
 172         ));
 173     }
 174
 175     let mut err = bad_placeholder_type(tcx, placeholder_types);
 176     if suggest {
 177         err.multipart_suggestion(
 178             "use type parameters instead",
 179             sugg,
 180             Applicability::HasPlaceholders,
 181         );
 182     }
 183     err.emit();
 184 }
 185
 186 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 187     let (generics, suggest) = match &item.kind {
 188         hir::ItemKind::Union(_, generics)
 189         | hir::ItemKind::Enum(_, generics)
 190         | hir::ItemKind::TraitAlias(generics, _)
 191         | hir::ItemKind::Trait(_, _, generics, ..)
 192         | hir::ItemKind::Impl { generics, .. }
 193         | hir::ItemKind::Struct(_, generics) => (generics, true),
 194         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 195         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 196         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 197         _ => return,
 198     };
 199
 200     let mut visitor = PlaceholderHirTyCollector::default();
 201     visitor.visit_item(item);
 202
 203     placeholder_type_error(tcx, Some(generics.span), &generics.params[..], visitor.0, suggest);
 204 }
 205
 206 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 207     type Map = Map<'tcx>;
 208
 209     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 210         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 211     }
 212
 213     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 214         convert_item(self.tcx, item.hir_id);
 215         reject_placeholder_type_signatures_in_item(self.tcx, item);
 216         intravisit::walk_item(self, item);
 217     }
 218
 219     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 220         for param in generics.params {
 221             match param.kind {
 222                 hir::GenericParamKind::Lifetime { .. } => {}
 223                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 224                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 225                     self.tcx.ensure().type_of(def_id);
 226                 }
 227                 hir::GenericParamKind::Type { .. } => {}
 228                 hir::GenericParamKind::Const { .. } => {
 229                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 230                     self.tcx.ensure().type_of(def_id);
 231                     // FIXME(const_generics:defaults)
 232                 }
 233             }
 234         }
 235         intravisit::walk_generics(self, generics);
 236     }
 237
 238     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 239         if let hir::ExprKind::Closure(..) = expr.kind {
 240             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 241             self.tcx.ensure().generics_of(def_id);
 242             self.tcx.ensure().type_of(def_id);
 243         }
 244         intravisit::walk_expr(self, expr);
 245     }
 246
 247     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 248         convert_trait_item(self.tcx, trait_item.hir_id);
 249         intravisit::walk_trait_item(self, trait_item);
 250     }
 251
 252     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 253         convert_impl_item(self.tcx, impl_item.hir_id);
 254         intravisit::walk_impl_item(self, impl_item);
 255     }
 256 }
 257
 258 ///////////////////////////////////////////////////////////////////////////
 259 // Utility types and common code for the above passes.
 260
 261 fn bad_placeholder_type(
 262     tcx: TyCtxt<'tcx>,
 263     mut spans: Vec<Span>,
 264 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 265     spans.sort();
 266     let mut err = struct_span_err!(
 267         tcx.sess,
 268         spans.clone(),
 269         E0121,
 270         "the type placeholder `_` is not allowed within types on item signatures",
 271     );
 272     for span in spans {
 273         err.span_label(span, "not allowed in type signatures");
 274     }
 275     err
 276 }
 277
 278 impl ItemCtxt<'tcx> {
 279     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 280         ItemCtxt { tcx, item_def_id }
 281     }
 282
 283     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 284         AstConv::ast_ty_to_ty(self, ast_ty)
 285     }
 286
 287     pub fn hir_id(&self) -> hir::HirId {
 288         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 289     }
 290
 291     pub fn node(&self) -> hir::Node<'tcx> {
 292         self.tcx.hir().get(self.hir_id())
 293     }
 294 }
 295
 296 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 297     fn tcx(&self) -> TyCtxt<'tcx> {
 298         self.tcx
 299     }
 300
 301     fn item_def_id(&self) -> Option<DefId> {
 302         Some(self.item_def_id)
 303     }
 304
 305     fn default_constness_for_trait_bounds(&self) -> hir::Constness {
 306         if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
 307             fn_like.constness()
 308         } else {
 309             hir::Constness::NotConst
 310         }
 311     }
 312
 313     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 314         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id.expect_local()))
 315     }
 316
 317     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 318         None
 319     }
 320
 321     fn allow_ty_infer(&self) -> bool {
 322         false
 323     }
 324
 325     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 326         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 327     }
 328
 329     fn ct_infer(
 330         &self,
 331         ty: Ty<'tcx>,
 332         _: Option<&ty::GenericParamDef>,
 333         span: Span,
 334     ) -> &'tcx Const<'tcx> {
 335         bad_placeholder_type(self.tcx(), vec![span]).emit();
 336         self.tcx().const_error(ty)
 337     }
 338
 339     fn projected_ty_from_poly_trait_ref(
 340         &self,
 341         span: Span,
 342         item_def_id: DefId,
 343         item_segment: &hir::PathSegment<'_>,
 344         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 345     ) -> Ty<'tcx> {
 346         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 347             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 348                 self,
 349                 self.tcx,
 350                 span,
 351                 item_def_id,
 352                 item_segment,
 353                 trait_ref.substs,
 354             );
 355             self.tcx().mk_projection(item_def_id, item_substs)
 356         } else {
 357             // There are no late-bound regions; we can just ignore the binder.
 358             let mut err = struct_span_err!(
 359                 self.tcx().sess,
 360                 span,
 361                 E0212,
 362                 "cannot use the associated type of a trait \
 363                  with uninferred generic parameters"
 364             );
 365
 366             match self.node() {
 367                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 368                     let item =
 369                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 370                     match &item.kind {
 371                         hir::ItemKind::Enum(_, generics)
 372                         | hir::ItemKind::Struct(_, generics)
 373                         | hir::ItemKind::Union(_, generics) => {
 374                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 375                             let (lt_sp, sugg) = match &generics.params[..] {
 376                                 [] => (generics.span, format!("<{}>", lt_name)),
 377                                 [bound, ..] => {
 378                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 379                                 }
 380                             };
 381                             let suggestions = vec![
 382                                 (lt_sp, sugg),
 383                                 (
 384                                     span,
 385                                     format!(
 386                                         "{}::{}",
 387                                         // Replace the existing lifetimes with a new named lifetime.
 388                                         self.tcx
 389                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 390                                                 self.tcx.mk_region(ty::ReEarlyBound(
 391                                                     ty::EarlyBoundRegion {
 392                                                         def_id: item_def_id,
 393                                                         index: 0,
 394                                                         name: Symbol::intern(&lt_name),
 395                                                     },
 396                                                 ))
 397                                             })
 398                                             .0,
 399                                         item_segment.ident
 400                                     ),
 401                                 ),
 402                             ];
 403                             err.multipart_suggestion(
 404                                 "use a fully qualified path with explicit lifetimes",
 405                                 suggestions,
 406                                 Applicability::MaybeIncorrect,
 407                             );
 408                         }
 409                         _ => {}
 410                     }
 411                 }
 412                 hir::Node::Item(hir::Item {
 413                     kind:
 414                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 415                     ..
 416                 }) => {}
 417                 hir::Node::Item(_)
 418                 | hir::Node::ForeignItem(_)
 419                 | hir::Node::TraitItem(_)
 420                 | hir::Node::ImplItem(_) => {
 421                     err.span_suggestion(
 422                         span,
 423                         "use a fully qualified path with inferred lifetimes",
 424                         format!(
 425                             "{}::{}",
 426                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 427                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 428                             item_segment.ident
 429                         ),
 430                         Applicability::MaybeIncorrect,
 431                     );
 432                 }
 433                 _ => {}
 434             }
 435             err.emit();
 436             self.tcx().ty_error()
 437         }
 438     }
 439
 440     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 441         // Types in item signatures are not normalized to avoid undue dependencies.
 442         ty
 443     }
 444
 445     fn set_tainted_by_errors(&self) {
 446         // There's no obvious place to track this, so just let it go.
 447     }
 448
 449     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 450         // There's no place to record types from signatures?
 451     }
 452 }
 453
 454 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 455 fn get_new_lifetime_name<'tcx>(
 456     tcx: TyCtxt<'tcx>,
 457     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 458     generics: &hir::Generics<'tcx>,
 459 ) -> String {
 460     let existing_lifetimes = tcx
 461         .collect_referenced_late_bound_regions(&poly_trait_ref)
 462         .into_iter()
 463         .filter_map(|lt| {
 464             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 465                 Some(name.as_str().to_string())
 466             } else {
 467                 None
 468             }
 469         })
 470         .chain(generics.params.iter().filter_map(|param| {
 471             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 472                 Some(param.name.ident().as_str().to_string())
 473             } else {
 474                 None
 475             }
 476         }))
 477         .collect::<FxHashSet<String>>();
 478
 479     let a_to_z_repeat_n = |n| {
 480         (b'a'..=b'z').map(move |c| {
 481             let mut s = '\''.to_string();
 482             s.extend(std::iter::repeat(char::from(c)).take(n));
 483             s
 484         })
 485     };
 486
 487     // If all single char lifetime names are present, we wrap around and double the chars.
 488     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 489 }
 490
 491 /// Returns the predicates defined on `item_def_id` of the form
 492 /// `X: Foo` where `X` is the type parameter `def_id`.
 493 fn type_param_predicates(
 494     tcx: TyCtxt<'_>,
 495     (item_def_id, def_id): (DefId, LocalDefId),
 496 ) -> ty::GenericPredicates<'_> {
 497     use rustc_hir::*;
 498
 499     // In the AST, bounds can derive from two places. Either
 500     // written inline like `<T: Foo>` or in a where-clause like
 501     // `where T: Foo`.
 502
 503     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 504     let param_owner = tcx.hir().ty_param_owner(param_id);
 505     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 506     let generics = tcx.generics_of(param_owner_def_id);
 507     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 508     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 509
 510     // Don't look for bounds where the type parameter isn't in scope.
 511     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 512         None
 513     } else {
 514         tcx.generics_of(item_def_id).parent
 515     };
 516
 517     let mut result = parent
 518         .map(|parent| {
 519             let icx = ItemCtxt::new(tcx, parent);
 520             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id())
 521         })
 522         .unwrap_or_default();
 523     let mut extend = None;
 524
 525     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 526     let ast_generics = match tcx.hir().get(item_hir_id) {
 527         Node::TraitItem(item) => &item.generics,
 528
 529         Node::ImplItem(item) => &item.generics,
 530
 531         Node::Item(item) => {
 532             match item.kind {
 533                 ItemKind::Fn(.., ref generics, _)
 534                 | ItemKind::Impl { ref generics, .. }
 535                 | ItemKind::TyAlias(_, ref generics)
 536                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 537                 | ItemKind::Enum(_, ref generics)
 538                 | ItemKind::Struct(_, ref generics)
 539                 | ItemKind::Union(_, ref generics) => generics,
 540                 ItemKind::Trait(_, _, ref generics, ..) => {
 541                     // Implied `Self: Trait` and supertrait bounds.
 542                     if param_id == item_hir_id {
 543                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 544                         extend =
 545                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 546                     }
 547                     generics
 548                 }
 549                 _ => return result,
 550             }
 551         }
 552
 553         Node::ForeignItem(item) => match item.kind {
 554             ForeignItemKind::Fn(_, _, ref generics) => generics,
 555             _ => return result,
 556         },
 557
 558         _ => return result,
 559     };
 560
 561     let icx = ItemCtxt::new(tcx, item_def_id);
 562     let extra_predicates = extend.into_iter().chain(
 563         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 564             .into_iter()
 565             .filter(|(predicate, _)| match predicate.skip_binders() {
 566                 ty::PredicateAtom::Trait(data, _) => data.self_ty().is_param(index),
 567                 _ => false,
 568             }),
 569     );
 570     result.predicates =
 571         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 572     result
 573 }
 574
 575 impl ItemCtxt<'tcx> {
 576     /// Finds bounds from `hir::Generics`. This requires scanning through the
 577     /// AST. We do this to avoid having to convert *all* the bounds, which
 578     /// would create artificial cycles. Instead, we can only convert the
 579     /// bounds for a type parameter `X` if `X::Foo` is used.
 580     fn type_parameter_bounds_in_generics(
 581         &self,
 582         ast_generics: &'tcx hir::Generics<'tcx>,
 583         param_id: hir::HirId,
 584         ty: Ty<'tcx>,
 585         only_self_bounds: OnlySelfBounds,
 586     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 587         let constness = self.default_constness_for_trait_bounds();
 588         let from_ty_params = ast_generics
 589             .params
 590             .iter()
 591             .filter_map(|param| match param.kind {
 592                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 593                 _ => None,
 594             })
 595             .flat_map(|bounds| bounds.iter())
 596             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 597
 598         let from_where_clauses = ast_generics
 599             .where_clause
 600             .predicates
 601             .iter()
 602             .filter_map(|wp| match *wp {
 603                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 604                 _ => None,
 605             })
 606             .flat_map(|bp| {
 607                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 608                     Some(ty)
 609                 } else if !only_self_bounds.0 {
 610                     Some(self.to_ty(&bp.bounded_ty))
 611                 } else {
 612                     None
 613                 };
 614                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 615             })
 616             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 617
 618         from_ty_params.chain(from_where_clauses).collect()
 619     }
 620 }
 621
 622 /// Tests whether this is the AST for a reference to the type
 623 /// parameter with ID `param_id`. We use this so as to avoid running
 624 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 625 /// conversion of the type to avoid inducing unnecessary cycles.
 626 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 627     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 628         match path.res {
 629             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 630                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 631             }
 632             _ => false,
 633         }
 634     } else {
 635         false
 636     }
 637 }
 638
 639 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 640     let it = tcx.hir().expect_item(item_id);
 641     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 642     let def_id = tcx.hir().local_def_id(item_id);
 643     match it.kind {
 644         // These don't define types.
 645         hir::ItemKind::ExternCrate(_)
 646         | hir::ItemKind::Use(..)
 647         | hir::ItemKind::Mod(_)
 648         | hir::ItemKind::GlobalAsm(_) => {}
 649         hir::ItemKind::ForeignMod { items, .. } => {
 650             for item in items {
 651                 let item = tcx.hir().foreign_item(item.id);
 652                 let def_id = tcx.hir().local_def_id(item.hir_id);
 653                 tcx.ensure().generics_of(def_id);
 654                 tcx.ensure().type_of(def_id);
 655                 tcx.ensure().predicates_of(def_id);
 656                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 657                     tcx.ensure().fn_sig(def_id);
 658                 }
 659             }
 660         }
 661         hir::ItemKind::Enum(ref enum_definition, _) => {
 662             tcx.ensure().generics_of(def_id);
 663             tcx.ensure().type_of(def_id);
 664             tcx.ensure().predicates_of(def_id);
 665             convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
 666         }
 667         hir::ItemKind::Impl { .. } => {
 668             tcx.ensure().generics_of(def_id);
 669             tcx.ensure().type_of(def_id);
 670             tcx.ensure().impl_trait_ref(def_id);
 671             tcx.ensure().predicates_of(def_id);
 672         }
 673         hir::ItemKind::Trait(..) => {
 674             tcx.ensure().generics_of(def_id);
 675             tcx.ensure().trait_def(def_id);
 676             tcx.at(it.span).super_predicates_of(def_id);
 677             tcx.ensure().predicates_of(def_id);
 678         }
 679         hir::ItemKind::TraitAlias(..) => {
 680             tcx.ensure().generics_of(def_id);
 681             tcx.at(it.span).super_predicates_of(def_id);
 682             tcx.ensure().predicates_of(def_id);
 683         }
 684         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 685             tcx.ensure().generics_of(def_id);
 686             tcx.ensure().type_of(def_id);
 687             tcx.ensure().predicates_of(def_id);
 688
 689             for f in struct_def.fields() {
 690                 let def_id = tcx.hir().local_def_id(f.hir_id);
 691                 tcx.ensure().generics_of(def_id);
 692                 tcx.ensure().type_of(def_id);
 693                 tcx.ensure().predicates_of(def_id);
 694             }
 695
 696             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 697                 convert_variant_ctor(tcx, ctor_hir_id);
 698             }
 699         }
 700
 701         // Desugared from `impl Trait`, so visited by the function's return type.
 702         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 703
 704         // Don't call `type_of` on opaque types, since that depends on type
 705         // checking function bodies. `check_item_type` ensures that it's called
 706         // instead.
 707         hir::ItemKind::OpaqueTy(..) => {
 708             tcx.ensure().generics_of(def_id);
 709             tcx.ensure().predicates_of(def_id);
 710             tcx.ensure().explicit_item_bounds(def_id);
 711         }
 712         hir::ItemKind::TyAlias(..)
 713         | hir::ItemKind::Static(..)
 714         | hir::ItemKind::Const(..)
 715         | hir::ItemKind::Fn(..) => {
 716             tcx.ensure().generics_of(def_id);
 717             tcx.ensure().type_of(def_id);
 718             tcx.ensure().predicates_of(def_id);
 719             match it.kind {
 720                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 721                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 722                 _ => (),
 723             }
 724         }
 725     }
 726 }
 727
 728 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 729     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 730     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 731     tcx.ensure().generics_of(def_id);
 732
 733     match trait_item.kind {
 734         hir::TraitItemKind::Fn(..) => {
 735             tcx.ensure().type_of(def_id);
 736             tcx.ensure().fn_sig(def_id);
 737         }
 738
 739         hir::TraitItemKind::Const(.., Some(_)) => {
 740             tcx.ensure().type_of(def_id);
 741         }
 742
 743         hir::TraitItemKind::Const(..) => {
 744             tcx.ensure().type_of(def_id);
 745             // Account for `const C: _;`.
 746             let mut visitor = PlaceholderHirTyCollector::default();
 747             visitor.visit_trait_item(trait_item);
 748             placeholder_type_error(tcx, None, &[], visitor.0, false);
 749         }
 750
 751         hir::TraitItemKind::Type(_, Some(_)) => {
 752             tcx.ensure().item_bounds(def_id);
 753             tcx.ensure().type_of(def_id);
 754             // Account for `type T = _;`.
 755             let mut visitor = PlaceholderHirTyCollector::default();
 756             visitor.visit_trait_item(trait_item);
 757             placeholder_type_error(tcx, None, &[], visitor.0, false);
 758         }
 759
 760         hir::TraitItemKind::Type(_, None) => {
 761             tcx.ensure().item_bounds(def_id);
 762             // #74612: Visit and try to find bad placeholders
 763             // even if there is no concrete type.
 764             let mut visitor = PlaceholderHirTyCollector::default();
 765             visitor.visit_trait_item(trait_item);
 766             placeholder_type_error(tcx, None, &[], visitor.0, false);
 767         }
 768     };
 769
 770     tcx.ensure().predicates_of(def_id);
 771 }
 772
 773 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 774     let def_id = tcx.hir().local_def_id(impl_item_id);
 775     tcx.ensure().generics_of(def_id);
 776     tcx.ensure().type_of(def_id);
 777     tcx.ensure().predicates_of(def_id);
 778     let impl_item = tcx.hir().expect_impl_item(impl_item_id);
 779     match impl_item.kind {
 780         hir::ImplItemKind::Fn(..) => {
 781             tcx.ensure().fn_sig(def_id);
 782         }
 783         hir::ImplItemKind::TyAlias(_) => {
 784             // Account for `type T = _;`
 785             let mut visitor = PlaceholderHirTyCollector::default();
 786             visitor.visit_impl_item(impl_item);
 787             placeholder_type_error(tcx, None, &[], visitor.0, false);
 788         }
 789         hir::ImplItemKind::Const(..) => {}
 790     }
 791 }
 792
 793 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 794     let def_id = tcx.hir().local_def_id(ctor_id);
 795     tcx.ensure().generics_of(def_id);
 796     tcx.ensure().type_of(def_id);
 797     tcx.ensure().predicates_of(def_id);
 798 }
 799
 800 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 801     let def = tcx.adt_def(def_id);
 802     let repr_type = def.repr.discr_type();
 803     let initial = repr_type.initial_discriminant(tcx);
 804     let mut prev_discr = None::<Discr<'_>>;
 805
 806     // fill the discriminant values and field types
 807     for variant in variants {
 808         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 809         prev_discr = Some(
 810             if let Some(ref e) = variant.disr_expr {
 811                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 812                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 813             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 814                 Some(discr)
 815             } else {
 816                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 817                     .span_label(
 818                         variant.span,
 819                         format!("overflowed on value after {}", prev_discr.unwrap()),
 820                     )
 821                     .note(&format!(
 822                         "explicitly set `{} = {}` if that is desired outcome",
 823                         variant.ident, wrapped_discr
 824                     ))
 825                     .emit();
 826                 None
 827             }
 828             .unwrap_or(wrapped_discr),
 829         );
 830
 831         for f in variant.data.fields() {
 832             let def_id = tcx.hir().local_def_id(f.hir_id);
 833             tcx.ensure().generics_of(def_id);
 834             tcx.ensure().type_of(def_id);
 835             tcx.ensure().predicates_of(def_id);
 836         }
 837
 838         // Convert the ctor, if any. This also registers the variant as
 839         // an item.
 840         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 841             convert_variant_ctor(tcx, ctor_hir_id);
 842         }
 843     }
 844 }
 845
 846 fn convert_variant(
 847     tcx: TyCtxt<'_>,
 848     variant_did: Option<LocalDefId>,
 849     ctor_did: Option<LocalDefId>,
 850     ident: Ident,
 851     discr: ty::VariantDiscr,
 852     def: &hir::VariantData<'_>,
 853     adt_kind: ty::AdtKind,
 854     parent_did: LocalDefId,
 855 ) -> ty::VariantDef {
 856     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 857     let fields = def
 858         .fields()
 859         .iter()
 860         .map(|f| {
 861             let fid = tcx.hir().local_def_id(f.hir_id);
 862             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 863             if let Some(prev_span) = dup_span {
 864                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 865                     field_name: f.ident,
 866                     span: f.span,
 867                     prev_span,
 868                 });
 869             } else {
 870                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 871             }
 872
 873             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 874         })
 875         .collect();
 876     let recovered = match def {
 877         hir::VariantData::Struct(_, r) => *r,
 878         _ => false,
 879     };
 880     ty::VariantDef::new(
 881         ident,
 882         variant_did.map(LocalDefId::to_def_id),
 883         ctor_did.map(LocalDefId::to_def_id),
 884         discr,
 885         fields,
 886         CtorKind::from_hir(def),
 887         adt_kind,
 888         parent_did.to_def_id(),
 889         recovered,
 890         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
 891             || variant_did.map_or(false, |variant_did| {
 892                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
 893             }),
 894     )
 895 }
 896
 897 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 898     use rustc_hir::*;
 899
 900     let def_id = def_id.expect_local();
 901     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
 902     let item = match tcx.hir().get(hir_id) {
 903         Node::Item(item) => item,
 904         _ => bug!(),
 905     };
 906
 907     let repr = ReprOptions::new(tcx, def_id.to_def_id());
 908     let (kind, variants) = match item.kind {
 909         ItemKind::Enum(ref def, _) => {
 910             let mut distance_from_explicit = 0;
 911             let variants = def
 912                 .variants
 913                 .iter()
 914                 .map(|v| {
 915                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 916                     let ctor_did =
 917                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 918
 919                     let discr = if let Some(ref e) = v.disr_expr {
 920                         distance_from_explicit = 0;
 921                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
 922                     } else {
 923                         ty::VariantDiscr::Relative(distance_from_explicit)
 924                     };
 925                     distance_from_explicit += 1;
 926
 927                     convert_variant(
 928                         tcx,
 929                         variant_did,
 930                         ctor_did,
 931                         v.ident,
 932                         discr,
 933                         &v.data,
 934                         AdtKind::Enum,
 935                         def_id,
 936                     )
 937                 })
 938                 .collect();
 939
 940             (AdtKind::Enum, variants)
 941         }
 942         ItemKind::Struct(ref def, _) => {
 943             let variant_did = None::<LocalDefId>;
 944             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 945
 946             let variants = std::iter::once(convert_variant(
 947                 tcx,
 948                 variant_did,
 949                 ctor_did,
 950                 item.ident,
 951                 ty::VariantDiscr::Relative(0),
 952                 def,
 953                 AdtKind::Struct,
 954                 def_id,
 955             ))
 956             .collect();
 957
 958             (AdtKind::Struct, variants)
 959         }
 960         ItemKind::Union(ref def, _) => {
 961             let variant_did = None;
 962             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 963
 964             let variants = std::iter::once(convert_variant(
 965                 tcx,
 966                 variant_did,
 967                 ctor_did,
 968                 item.ident,
 969                 ty::VariantDiscr::Relative(0),
 970                 def,
 971                 AdtKind::Union,
 972                 def_id,
 973             ))
 974             .collect();
 975
 976             (AdtKind::Union, variants)
 977         }
 978         _ => bug!(),
 979     };
 980     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
 981 }
 982
 983 /// Ensures that the super-predicates of the trait with a `DefId`
 984 /// of `trait_def_id` are converted and stored. This also ensures that
 985 /// the transitive super-predicates are converted.
 986 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 987     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 988     let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
 989
 990     let item = match tcx.hir().get(trait_hir_id) {
 991         Node::Item(item) => item,
 992         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 993     };
 994
 995     let (generics, bounds) = match item.kind {
 996         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 997         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 998         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 999     };
1000
1001     let icx = ItemCtxt::new(tcx, trait_def_id);
1002
1003     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1004     let self_param_ty = tcx.types.self_param;
1005     let superbounds1 =
1006         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
1007
1008     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1009
1010     // Convert any explicit superbounds in the where-clause,
1011     // e.g., `trait Foo where Self: Bar`.
1012     // In the case of trait aliases, however, we include all bounds in the where-clause,
1013     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1014     // as one of its "superpredicates".
1015     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1016     let superbounds2 = icx.type_parameter_bounds_in_generics(
1017         generics,
1018         item.hir_id,
1019         self_param_ty,
1020         OnlySelfBounds(!is_trait_alias),
1021     );
1022
1023     // Combine the two lists to form the complete set of superbounds:
1024     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1025
1026     // Now require that immediate supertraits are converted,
1027     // which will, in turn, reach indirect supertraits.
1028     for &(pred, span) in superbounds {
1029         debug!("superbound: {:?}", pred);
1030         if let ty::PredicateAtom::Trait(bound, _) = pred.skip_binders() {
1031             tcx.at(span).super_predicates_of(bound.def_id());
1032         }
1033     }
1034
1035     ty::GenericPredicates { parent: None, predicates: superbounds }
1036 }
1037
1038 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1039     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1040     let item = tcx.hir().expect_item(hir_id);
1041
1042     let (is_auto, unsafety) = match item.kind {
1043         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1044         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1045         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1046     };
1047
1048     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1049     if paren_sugar && !tcx.features().unboxed_closures {
1050         tcx.sess
1051             .struct_span_err(
1052                 item.span,
1053                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1054                  which traits can use parenthetical notation",
1055             )
1056             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1057             .emit();
1058     }
1059
1060     let is_marker = tcx.has_attr(def_id, sym::marker);
1061     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1062         ty::trait_def::TraitSpecializationKind::Marker
1063     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1064         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1065     } else {
1066         ty::trait_def::TraitSpecializationKind::None
1067     };
1068     let def_path_hash = tcx.def_path_hash(def_id);
1069     ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, spec_kind, def_path_hash)
1070 }
1071
1072 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1073     struct LateBoundRegionsDetector<'tcx> {
1074         tcx: TyCtxt<'tcx>,
1075         outer_index: ty::DebruijnIndex,
1076         has_late_bound_regions: Option<Span>,
1077     }
1078
1079     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1080         type Map = intravisit::ErasedMap<'tcx>;
1081
1082         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1083             NestedVisitorMap::None
1084         }
1085
1086         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1087             if self.has_late_bound_regions.is_some() {
1088                 return;
1089             }
1090             match ty.kind {
1091                 hir::TyKind::BareFn(..) => {
1092                     self.outer_index.shift_in(1);
1093                     intravisit::walk_ty(self, ty);
1094                     self.outer_index.shift_out(1);
1095                 }
1096                 _ => intravisit::walk_ty(self, ty),
1097             }
1098         }
1099
1100         fn visit_poly_trait_ref(
1101             &mut self,
1102             tr: &'tcx hir::PolyTraitRef<'tcx>,
1103             m: hir::TraitBoundModifier,
1104         ) {
1105             if self.has_late_bound_regions.is_some() {
1106                 return;
1107             }
1108             self.outer_index.shift_in(1);
1109             intravisit::walk_poly_trait_ref(self, tr, m);
1110             self.outer_index.shift_out(1);
1111         }
1112
1113         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1114             if self.has_late_bound_regions.is_some() {
1115                 return;
1116             }
1117
1118             match self.tcx.named_region(lt.hir_id) {
1119                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1120                 Some(
1121                     rl::Region::LateBound(debruijn, _, _) | rl::Region::LateBoundAnon(debruijn, _),
1122                 ) if debruijn < self.outer_index => {}
1123                 Some(
1124                     rl::Region::LateBound(..)
1125                     | rl::Region::LateBoundAnon(..)
1126                     | rl::Region::Free(..),
1127                 )
1128                 | None => {
1129                     self.has_late_bound_regions = Some(lt.span);
1130                 }
1131             }
1132         }
1133     }
1134
1135     fn has_late_bound_regions<'tcx>(
1136         tcx: TyCtxt<'tcx>,
1137         generics: &'tcx hir::Generics<'tcx>,
1138         decl: &'tcx hir::FnDecl<'tcx>,
1139     ) -> Option<Span> {
1140         let mut visitor = LateBoundRegionsDetector {
1141             tcx,
1142             outer_index: ty::INNERMOST,
1143             has_late_bound_regions: None,
1144         };
1145         for param in generics.params {
1146             if let GenericParamKind::Lifetime { .. } = param.kind {
1147                 if tcx.is_late_bound(param.hir_id) {
1148                     return Some(param.span);
1149                 }
1150             }
1151         }
1152         visitor.visit_fn_decl(decl);
1153         visitor.has_late_bound_regions
1154     }
1155
1156     match node {
1157         Node::TraitItem(item) => match item.kind {
1158             hir::TraitItemKind::Fn(ref sig, _) => {
1159                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1160             }
1161             _ => None,
1162         },
1163         Node::ImplItem(item) => match item.kind {
1164             hir::ImplItemKind::Fn(ref sig, _) => {
1165                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1166             }
1167             _ => None,
1168         },
1169         Node::ForeignItem(item) => match item.kind {
1170             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1171                 has_late_bound_regions(tcx, generics, fn_decl)
1172             }
1173             _ => None,
1174         },
1175         Node::Item(item) => match item.kind {
1176             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1177                 has_late_bound_regions(tcx, generics, &sig.decl)
1178             }
1179             _ => None,
1180         },
1181         _ => None,
1182     }
1183 }
1184
1185 struct AnonConstInParamListDetector {
1186     in_param_list: bool,
1187     found_anon_const_in_list: bool,
1188     ct: HirId,
1189 }
1190
1191 impl<'v> Visitor<'v> for AnonConstInParamListDetector {
1192     type Map = intravisit::ErasedMap<'v>;
1193
1194     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1195         NestedVisitorMap::None
1196     }
1197
1198     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1199         let prev = self.in_param_list;
1200         self.in_param_list = true;
1201         intravisit::walk_generic_param(self, p);
1202         self.in_param_list = prev;
1203     }
1204
1205     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1206         if self.in_param_list && self.ct == c.hir_id {
1207             self.found_anon_const_in_list = true;
1208         } else {
1209             intravisit::walk_anon_const(self, c)
1210         }
1211     }
1212 }
1213
1214 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1215     use rustc_hir::*;
1216
1217     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1218
1219     let node = tcx.hir().get(hir_id);
1220     let parent_def_id = match node {
1221         Node::ImplItem(_)
1222         | Node::TraitItem(_)
1223         | Node::Variant(_)
1224         | Node::Ctor(..)
1225         | Node::Field(_) => {
1226             let parent_id = tcx.hir().get_parent_item(hir_id);
1227             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1228         }
1229         // FIXME(#43408) always enable this once `lazy_normalization` is
1230         // stable enough and does not need a feature gate anymore.
1231         Node::AnonConst(_) => {
1232             let parent_id = tcx.hir().get_parent_item(hir_id);
1233             let parent_def_id = tcx.hir().local_def_id(parent_id);
1234
1235             let mut in_param_list = false;
1236             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1237                 if let Some(generics) = node.generics() {
1238                     let mut visitor = AnonConstInParamListDetector {
1239                         in_param_list: false,
1240                         found_anon_const_in_list: false,
1241                         ct: hir_id,
1242                     };
1243
1244                     visitor.visit_generics(generics);
1245                     in_param_list = visitor.found_anon_const_in_list;
1246                     break;
1247                 }
1248             }
1249
1250             if in_param_list {
1251                 // We do not allow generic parameters in anon consts if we are inside
1252                 // of a param list.
1253                 //
1254                 // This affects both default type bindings, e.g. `struct<T, U = [u8; std::mem::size_of::<T>()]>(T, U)`,
1255                 // and the types of const parameters, e.g. `struct V<const N: usize, const M: [u8; N]>();`.
1256                 None
1257             } else if tcx.lazy_normalization() {
1258                 // HACK(eddyb) this provides the correct generics when
1259                 // `feature(const_generics)` is enabled, so that const expressions
1260                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1261                 //
1262                 // Note that we do not supply the parent generics when using
1263                 // `feature(min_const_generics)`.
1264                 Some(parent_def_id.to_def_id())
1265             } else {
1266                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1267                 match parent_node {
1268                     // HACK(eddyb) this provides the correct generics for repeat
1269                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1270                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1271                     // as they shouldn't be able to cause query cycle errors.
1272                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1273                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1274                         if constant.hir_id == hir_id =>
1275                     {
1276                         Some(parent_def_id.to_def_id())
1277                     }
1278
1279                     _ => None,
1280                 }
1281             }
1282         }
1283         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1284             Some(tcx.closure_base_def_id(def_id))
1285         }
1286         Node::Item(item) => match item.kind {
1287             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1288                 impl_trait_fn.or_else(|| {
1289                     let parent_id = tcx.hir().get_parent_item(hir_id);
1290                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1291                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1292                     // Opaque types are always nested within another item, and
1293                     // inherit the generics of the item.
1294                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1295                 })
1296             }
1297             _ => None,
1298         },
1299         _ => None,
1300     };
1301
1302     let mut opt_self = None;
1303     let mut allow_defaults = false;
1304
1305     let no_generics = hir::Generics::empty();
1306     let ast_generics = match node {
1307         Node::TraitItem(item) => &item.generics,
1308
1309         Node::ImplItem(item) => &item.generics,
1310
1311         Node::Item(item) => {
1312             match item.kind {
1313                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl { ref generics, .. } => generics,
1314
1315                 ItemKind::TyAlias(_, ref generics)
1316                 | ItemKind::Enum(_, ref generics)
1317                 | ItemKind::Struct(_, ref generics)
1318                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1319                 | ItemKind::Union(_, ref generics) => {
1320                     allow_defaults = true;
1321                     generics
1322                 }
1323
1324                 ItemKind::Trait(_, _, ref generics, ..)
1325                 | ItemKind::TraitAlias(ref generics, ..) => {
1326                     // Add in the self type parameter.
1327                     //
1328                     // Something of a hack: use the node id for the trait, also as
1329                     // the node id for the Self type parameter.
1330                     let param_id = item.hir_id;
1331
1332                     opt_self = Some(ty::GenericParamDef {
1333                         index: 0,
1334                         name: kw::SelfUpper,
1335                         def_id: tcx.hir().local_def_id(param_id).to_def_id(),
1336                         pure_wrt_drop: false,
1337                         kind: ty::GenericParamDefKind::Type {
1338                             has_default: false,
1339                             object_lifetime_default: rl::Set1::Empty,
1340                             synthetic: None,
1341                         },
1342                     });
1343
1344                     allow_defaults = true;
1345                     generics
1346                 }
1347
1348                 _ => &no_generics,
1349             }
1350         }
1351
1352         Node::ForeignItem(item) => match item.kind {
1353             ForeignItemKind::Static(..) => &no_generics,
1354             ForeignItemKind::Fn(_, _, ref generics) => generics,
1355             ForeignItemKind::Type => &no_generics,
1356         },
1357
1358         _ => &no_generics,
1359     };
1360
1361     let has_self = opt_self.is_some();
1362     let mut parent_has_self = false;
1363     let mut own_start = has_self as u32;
1364     let parent_count = parent_def_id.map_or(0, |def_id| {
1365         let generics = tcx.generics_of(def_id);
1366         assert_eq!(has_self, false);
1367         parent_has_self = generics.has_self;
1368         own_start = generics.count() as u32;
1369         generics.parent_count + generics.params.len()
1370     });
1371
1372     let mut params: Vec<_> = opt_self.into_iter().collect();
1373
1374     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1375     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1376         name: param.name.ident().name,
1377         index: own_start + i as u32,
1378         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1379         pure_wrt_drop: param.pure_wrt_drop,
1380         kind: ty::GenericParamDefKind::Lifetime,
1381     }));
1382
1383     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1384
1385     // Now create the real type and const parameters.
1386     let type_start = own_start - has_self as u32 + params.len() as u32;
1387     let mut i = 0;
1388
1389     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1390         GenericParamKind::Lifetime { .. } => None,
1391         GenericParamKind::Type { ref default, synthetic, .. } => {
1392             if !allow_defaults && default.is_some() {
1393                 if !tcx.features().default_type_parameter_fallback {
1394                     tcx.struct_span_lint_hir(
1395                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1396                         param.hir_id,
1397                         param.span,
1398                         |lint| {
1399                             lint.build(
1400                                 "defaults for type parameters are only allowed in \
1401                                  `struct`, `enum`, `type`, or `trait` definitions.",
1402                             )
1403                             .emit();
1404                         },
1405                     );
1406                 }
1407             }
1408
1409             let kind = ty::GenericParamDefKind::Type {
1410                 has_default: default.is_some(),
1411                 object_lifetime_default: object_lifetime_defaults
1412                     .as_ref()
1413                     .map_or(rl::Set1::Empty, |o| o[i]),
1414                 synthetic,
1415             };
1416
1417             let param_def = ty::GenericParamDef {
1418                 index: type_start + i as u32,
1419                 name: param.name.ident().name,
1420                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1421                 pure_wrt_drop: param.pure_wrt_drop,
1422                 kind,
1423             };
1424             i += 1;
1425             Some(param_def)
1426         }
1427         GenericParamKind::Const { .. } => {
1428             let param_def = ty::GenericParamDef {
1429                 index: type_start + i as u32,
1430                 name: param.name.ident().name,
1431                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1432                 pure_wrt_drop: param.pure_wrt_drop,
1433                 kind: ty::GenericParamDefKind::Const,
1434             };
1435             i += 1;
1436             Some(param_def)
1437         }
1438     }));
1439
1440     // provide junk type parameter defs - the only place that
1441     // cares about anything but the length is instantiation,
1442     // and we don't do that for closures.
1443     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1444         let dummy_args = if gen.is_some() {
1445             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1446         } else {
1447             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1448         };
1449
1450         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1451             index: type_start + i as u32,
1452             name: Symbol::intern(arg),
1453             def_id,
1454             pure_wrt_drop: false,
1455             kind: ty::GenericParamDefKind::Type {
1456                 has_default: false,
1457                 object_lifetime_default: rl::Set1::Empty,
1458                 synthetic: None,
1459             },
1460         }));
1461     }
1462
1463     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1464
1465     ty::Generics {
1466         parent: parent_def_id,
1467         parent_count,
1468         params,
1469         param_def_id_to_index,
1470         has_self: has_self || parent_has_self,
1471         has_late_bound_regions: has_late_bound_regions(tcx, node),
1472     }
1473 }
1474
1475 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1476     generic_args
1477         .iter()
1478         .filter_map(|arg| match arg {
1479             hir::GenericArg::Type(ty) => Some(ty),
1480             _ => None,
1481         })
1482         .any(is_suggestable_infer_ty)
1483 }
1484
1485 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1486 /// use inference to provide suggestions for the appropriate type if possible.
1487 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1488     use hir::TyKind::*;
1489     match &ty.kind {
1490         Infer => true,
1491         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1492         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1493         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1494         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1495         Path(hir::QPath::TypeRelative(ty, segment)) => {
1496             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1497         }
1498         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1499             ty_opt.map_or(false, is_suggestable_infer_ty)
1500                 || segments
1501                     .iter()
1502                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1503         }
1504         _ => false,
1505     }
1506 }
1507
1508 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1509     if let hir::FnRetTy::Return(ref ty) = output {
1510         if is_suggestable_infer_ty(ty) {
1511             return Some(&**ty);
1512         }
1513     }
1514     None
1515 }
1516
1517 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1518     use rustc_hir::Node::*;
1519     use rustc_hir::*;
1520
1521     let def_id = def_id.expect_local();
1522     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1523
1524     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1525
1526     match tcx.hir().get(hir_id) {
1527         TraitItem(hir::TraitItem {
1528             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1529             ident,
1530             generics,
1531             ..
1532         })
1533         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1534         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1535             match get_infer_ret_ty(&sig.decl.output) {
1536                 Some(ty) => {
1537                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1538                     let mut visitor = PlaceholderHirTyCollector::default();
1539                     visitor.visit_ty(ty);
1540                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1541                     let ret_ty = fn_sig.output();
1542                     if ret_ty != tcx.ty_error() {
1543                         diag.span_suggestion(
1544                             ty.span,
1545                             "replace with the correct return type",
1546                             ret_ty.to_string(),
1547                             Applicability::MaybeIncorrect,
1548                         );
1549                     }
1550                     diag.emit();
1551                     ty::Binder::bind(fn_sig)
1552                 }
1553                 None => AstConv::ty_of_fn(
1554                     &icx,
1555                     sig.header.unsafety,
1556                     sig.header.abi,
1557                     &sig.decl,
1558                     &generics,
1559                     Some(ident.span),
1560                 ),
1561             }
1562         }
1563
1564         TraitItem(hir::TraitItem {
1565             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1566             ident,
1567             generics,
1568             ..
1569         }) => {
1570             AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl, &generics, Some(ident.span))
1571         }
1572
1573         ForeignItem(&hir::ForeignItem {
1574             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1575             ident,
1576             ..
1577         }) => {
1578             let abi = tcx.hir().get_foreign_abi(hir_id);
1579             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1580         }
1581
1582         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1583             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1584             let inputs =
1585                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1586             ty::Binder::bind(tcx.mk_fn_sig(
1587                 inputs,
1588                 ty,
1589                 false,
1590                 hir::Unsafety::Normal,
1591                 abi::Abi::Rust,
1592             ))
1593         }
1594
1595         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1596             // Closure signatures are not like other function
1597             // signatures and cannot be accessed through `fn_sig`. For
1598             // example, a closure signature excludes the `self`
1599             // argument. In any case they are embedded within the
1600             // closure type as part of the `ClosureSubsts`.
1601             //
1602             // To get the signature of a closure, you should use the
1603             // `sig` method on the `ClosureSubsts`:
1604             //
1605             //    substs.as_closure().sig(def_id, tcx)
1606             bug!(
1607                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1608             );
1609         }
1610
1611         x => {
1612             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1613         }
1614     }
1615 }
1616
1617 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1618     let icx = ItemCtxt::new(tcx, def_id);
1619
1620     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1621     match tcx.hir().expect_item(hir_id).kind {
1622         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
1623             let selfty = tcx.type_of(def_id);
1624             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1625         }),
1626         _ => bug!(),
1627     }
1628 }
1629
1630 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1631     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1632     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1633     let item = tcx.hir().expect_item(hir_id);
1634     match &item.kind {
1635         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative(span), of_trait, .. } => {
1636             if is_rustc_reservation {
1637                 let span = span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(*span));
1638                 tcx.sess.span_err(span, "reservation impls can't be negative");
1639             }
1640             ty::ImplPolarity::Negative
1641         }
1642         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
1643             if is_rustc_reservation {
1644                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1645             }
1646             ty::ImplPolarity::Positive
1647         }
1648         hir::ItemKind::Impl {
1649             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
1650         } => {
1651             if is_rustc_reservation {
1652                 ty::ImplPolarity::Reservation
1653             } else {
1654                 ty::ImplPolarity::Positive
1655             }
1656         }
1657         ref item => bug!("impl_polarity: {:?} not an impl", item),
1658     }
1659 }
1660
1661 /// Returns the early-bound lifetimes declared in this generics
1662 /// listing. For anything other than fns/methods, this is just all
1663 /// the lifetimes that are declared. For fns or methods, we have to
1664 /// screen out those that do not appear in any where-clauses etc using
1665 /// `resolve_lifetime::early_bound_lifetimes`.
1666 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1667     tcx: TyCtxt<'tcx>,
1668     generics: &'a hir::Generics<'a>,
1669 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1670     generics.params.iter().filter(move |param| match param.kind {
1671         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1672         _ => false,
1673     })
1674 }
1675
1676 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1677 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1678 /// inferred constraints concerning which regions outlive other regions.
1679 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1680     debug!("predicates_defined_on({:?})", def_id);
1681     let mut result = tcx.explicit_predicates_of(def_id);
1682     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1683     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1684     if !inferred_outlives.is_empty() {
1685         debug!(
1686             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1687             def_id, inferred_outlives,
1688         );
1689         if result.predicates.is_empty() {
1690             result.predicates = inferred_outlives;
1691         } else {
1692             result.predicates = tcx
1693                 .arena
1694                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1695         }
1696     }
1697
1698     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1699     result
1700 }
1701
1702 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1703 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1704 /// `Self: Trait` predicates for traits.
1705 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1706     let mut result = tcx.predicates_defined_on(def_id);
1707
1708     if tcx.is_trait(def_id) {
1709         // For traits, add `Self: Trait` predicate. This is
1710         // not part of the predicates that a user writes, but it
1711         // is something that one must prove in order to invoke a
1712         // method or project an associated type.
1713         //
1714         // In the chalk setup, this predicate is not part of the
1715         // "predicates" for a trait item. But it is useful in
1716         // rustc because if you directly (e.g.) invoke a trait
1717         // method like `Trait::method(...)`, you must naturally
1718         // prove that the trait applies to the types that were
1719         // used, and adding the predicate into this list ensures
1720         // that this is done.
1721         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
1722         result.predicates =
1723             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
1724                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
1725                 span,
1726             ))));
1727     }
1728     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1729     result
1730 }
1731
1732 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1733 /// N.B., this does not include any implied/inferred constraints.
1734 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1735     use rustc_hir::*;
1736
1737     debug!("explicit_predicates_of(def_id={:?})", def_id);
1738
1739     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1740     let node = tcx.hir().get(hir_id);
1741
1742     let mut is_trait = None;
1743     let mut is_default_impl_trait = None;
1744
1745     let icx = ItemCtxt::new(tcx, def_id);
1746     let constness = icx.default_constness_for_trait_bounds();
1747
1748     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
1749
1750     // We use an `IndexSet` to preserves order of insertion.
1751     // Preserving the order of insertion is important here so as not to break
1752     // compile-fail UI tests.
1753     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
1754
1755     let ast_generics = match node {
1756         Node::TraitItem(item) => &item.generics,
1757
1758         Node::ImplItem(item) => &item.generics,
1759
1760         Node::Item(item) => {
1761             match item.kind {
1762                 ItemKind::Impl { defaultness, ref generics, .. } => {
1763                     if defaultness.is_default() {
1764                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
1765                     }
1766                     generics
1767                 }
1768                 ItemKind::Fn(.., ref generics, _)
1769                 | ItemKind::TyAlias(_, ref generics)
1770                 | ItemKind::Enum(_, ref generics)
1771                 | ItemKind::Struct(_, ref generics)
1772                 | ItemKind::Union(_, ref generics) => generics,
1773
1774                 ItemKind::Trait(_, _, ref generics, ..) => {
1775                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1776                     generics
1777                 }
1778                 ItemKind::TraitAlias(ref generics, _) => {
1779                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1780                     generics
1781                 }
1782                 ItemKind::OpaqueTy(OpaqueTy {
1783                     bounds: _,
1784                     impl_trait_fn,
1785                     ref generics,
1786                     origin: _,
1787                 }) => {
1788                     if impl_trait_fn.is_some() {
1789                         // return-position impl trait
1790                         //
1791                         // We don't inherit predicates from the parent here:
1792                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
1793                         // then the return type is `f::<'static, T>::{{opaque}}`.
1794                         //
1795                         // If we inherited the predicates of `f` then we would
1796                         // require that `T: 'static` to show that the return
1797                         // type is well-formed.
1798                         //
1799                         // The only way to have something with this opaque type
1800                         // is from the return type of the containing function,
1801                         // which will ensure that the function's predicates
1802                         // hold.
1803                         return ty::GenericPredicates { parent: None, predicates: &[] };
1804                     } else {
1805                         // type-alias impl trait
1806                         generics
1807                     }
1808                 }
1809
1810                 _ => NO_GENERICS,
1811             }
1812         }
1813
1814         Node::ForeignItem(item) => match item.kind {
1815             ForeignItemKind::Static(..) => NO_GENERICS,
1816             ForeignItemKind::Fn(_, _, ref generics) => generics,
1817             ForeignItemKind::Type => NO_GENERICS,
1818         },
1819
1820         _ => NO_GENERICS,
1821     };
1822
1823     let generics = tcx.generics_of(def_id);
1824     let parent_count = generics.parent_count as u32;
1825     let has_own_self = generics.has_self && parent_count == 0;
1826
1827     // Below we'll consider the bounds on the type parameters (including `Self`)
1828     // and the explicit where-clauses, but to get the full set of predicates
1829     // on a trait we need to add in the supertrait bounds and bounds found on
1830     // associated types.
1831     if let Some(_trait_ref) = is_trait {
1832         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
1833     }
1834
1835     // In default impls, we can assume that the self type implements
1836     // the trait. So in:
1837     //
1838     //     default impl Foo for Bar { .. }
1839     //
1840     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
1841     // (see below). Recall that a default impl is not itself an impl, but rather a
1842     // set of defaults that can be incorporated into another impl.
1843     if let Some(trait_ref) = is_default_impl_trait {
1844         predicates.insert((
1845             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
1846             tcx.def_span(def_id),
1847         ));
1848     }
1849
1850     // Collect the region predicates that were declared inline as
1851     // well. In the case of parameters declared on a fn or method, we
1852     // have to be careful to only iterate over early-bound regions.
1853     let mut index = parent_count + has_own_self as u32;
1854     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
1855         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
1856             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1857             index,
1858             name: param.name.ident().name,
1859         }));
1860         index += 1;
1861
1862         match param.kind {
1863             GenericParamKind::Lifetime { .. } => {
1864                 param.bounds.iter().for_each(|bound| match bound {
1865                     hir::GenericBound::Outlives(lt) => {
1866                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
1867                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
1868                         predicates.insert((outlives.to_predicate(tcx), lt.span));
1869                     }
1870                     _ => bug!(),
1871                 });
1872             }
1873             _ => bug!(),
1874         }
1875     }
1876
1877     // Collect the predicates that were written inline by the user on each
1878     // type parameter (e.g., `<T: Foo>`).
1879     for param in ast_generics.params {
1880         match param.kind {
1881             // We already dealt with early bound lifetimes above.
1882             GenericParamKind::Lifetime { .. } => (),
1883             GenericParamKind::Type { .. } => {
1884                 let name = param.name.ident().name;
1885                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
1886                 index += 1;
1887
1888                 let sized = SizedByDefault::Yes;
1889                 let bounds =
1890                     AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
1891                 predicates.extend(bounds.predicates(tcx, param_ty));
1892             }
1893             GenericParamKind::Const { .. } => {
1894                 // Bounds on const parameters are currently not possible.
1895                 debug_assert!(param.bounds.is_empty());
1896                 index += 1;
1897             }
1898         }
1899     }
1900
1901     // Add in the bounds that appear in the where-clause.
1902     let where_clause = &ast_generics.where_clause;
1903     for predicate in where_clause.predicates {
1904         match predicate {
1905             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
1906                 let ty = icx.to_ty(&bound_pred.bounded_ty);
1907
1908                 // Keep the type around in a dummy predicate, in case of no bounds.
1909                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
1910                 // is still checked for WF.
1911                 if bound_pred.bounds.is_empty() {
1912                     if let ty::Param(_) = ty.kind() {
1913                         // This is a `where T:`, which can be in the HIR from the
1914                         // transformation that moves `?Sized` to `T`'s declaration.
1915                         // We can skip the predicate because type parameters are
1916                         // trivially WF, but also we *should*, to avoid exposing
1917                         // users who never wrote `where Type:,` themselves, to
1918                         // compiler/tooling bugs from not handling WF predicates.
1919                     } else {
1920                         let span = bound_pred.bounded_ty.span;
1921                         let re_root_empty = tcx.lifetimes.re_root_empty;
1922                         let predicate = ty::Binder::bind(ty::PredicateAtom::TypeOutlives(
1923                             ty::OutlivesPredicate(ty, re_root_empty),
1924                         ));
1925                         predicates.insert((
1926                             predicate.potentially_quantified(tcx, ty::PredicateKind::ForAll),
1927                             span,
1928                         ));
1929                     }
1930                 }
1931
1932                 for bound in bound_pred.bounds.iter() {
1933                     match bound {
1934                         &hir::GenericBound::Trait(ref poly_trait_ref, modifier) => {
1935                             let constness = match modifier {
1936                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
1937                                 hir::TraitBoundModifier::None => constness,
1938                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
1939                             };
1940
1941                             let mut bounds = Bounds::default();
1942                             let _ = AstConv::instantiate_poly_trait_ref(
1943                                 &icx,
1944                                 poly_trait_ref,
1945                                 constness,
1946                                 ty,
1947                                 &mut bounds,
1948                             );
1949                             predicates.extend(bounds.predicates(tcx, ty));
1950                         }
1951
1952                         &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
1953                             let mut bounds = Bounds::default();
1954                             AstConv::instantiate_lang_item_trait_ref(
1955                                 &icx,
1956                                 lang_item,
1957                                 span,
1958                                 hir_id,
1959                                 args,
1960                                 ty,
1961                                 &mut bounds,
1962                             );
1963                             predicates.extend(bounds.predicates(tcx, ty));
1964                         }
1965
1966                         &hir::GenericBound::Outlives(ref lifetime) => {
1967                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
1968                             predicates.insert((
1969                                 ty::Binder::bind(ty::PredicateAtom::TypeOutlives(
1970                                     ty::OutlivesPredicate(ty, region),
1971                                 ))
1972                                 .potentially_quantified(tcx, ty::PredicateKind::ForAll),
1973                                 lifetime.span,
1974                             ));
1975                         }
1976                     }
1977                 }
1978             }
1979
1980             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
1981                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
1982                 predicates.extend(region_pred.bounds.iter().map(|bound| {
1983                     let (r2, span) = match bound {
1984                         hir::GenericBound::Outlives(lt) => {
1985                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
1986                         }
1987                         _ => bug!(),
1988                     };
1989                     let pred = ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(r1, r2))
1990                         .to_predicate(icx.tcx);
1991
1992                     (pred, span)
1993                 }))
1994             }
1995
1996             &hir::WherePredicate::EqPredicate(..) => {
1997                 // FIXME(#20041)
1998             }
1999         }
2000     }
2001
2002     if tcx.features().const_evaluatable_checked {
2003         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2004     }
2005
2006     let mut predicates: Vec<_> = predicates.into_iter().collect();
2007
2008     // Subtle: before we store the predicates into the tcx, we
2009     // sort them so that predicates like `T: Foo<Item=U>` come
2010     // before uses of `U`.  This avoids false ambiguity errors
2011     // in trait checking. See `setup_constraining_predicates`
2012     // for details.
2013     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2014         let self_ty = tcx.type_of(def_id);
2015         let trait_ref = tcx.impl_trait_ref(def_id);
2016         cgp::setup_constraining_predicates(
2017             tcx,
2018             &mut predicates,
2019             trait_ref,
2020             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2021         );
2022     }
2023
2024     let result = ty::GenericPredicates {
2025         parent: generics.parent,
2026         predicates: tcx.arena.alloc_from_iter(predicates),
2027     };
2028     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2029     result
2030 }
2031
2032 fn const_evaluatable_predicates_of<'tcx>(
2033     tcx: TyCtxt<'tcx>,
2034     def_id: LocalDefId,
2035 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2036     struct ConstCollector<'tcx> {
2037         tcx: TyCtxt<'tcx>,
2038         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2039     }
2040
2041     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2042         type Map = Map<'tcx>;
2043
2044         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2045             intravisit::NestedVisitorMap::None
2046         }
2047
2048         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2049             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2050             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2051             if let ty::ConstKind::Unevaluated(def, substs, None) = ct.val {
2052                 let span = self.tcx.hir().span(c.hir_id);
2053                 self.preds.insert((
2054                     ty::PredicateAtom::ConstEvaluatable(def, substs).to_predicate(self.tcx),
2055                     span,
2056                 ));
2057             }
2058         }
2059
2060         // Look into `TyAlias`.
2061         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
2062             use ty::fold::{TypeFoldable, TypeVisitor};
2063             struct TyAliasVisitor<'a, 'tcx> {
2064                 tcx: TyCtxt<'tcx>,
2065                 preds: &'a mut FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2066                 span: Span,
2067             }
2068
2069             impl<'a, 'tcx> TypeVisitor<'tcx> for TyAliasVisitor<'a, 'tcx> {
2070                 fn visit_const(&mut self, ct: &'tcx Const<'tcx>) -> ControlFlow<Self::BreakTy> {
2071                     if let ty::ConstKind::Unevaluated(def, substs, None) = ct.val {
2072                         self.preds.insert((
2073                             ty::PredicateAtom::ConstEvaluatable(def, substs).to_predicate(self.tcx),
2074                             self.span,
2075                         ));
2076                     }
2077                     ControlFlow::CONTINUE
2078                 }
2079             }
2080
2081             if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = ty.kind {
2082                 if let Res::Def(DefKind::TyAlias, def_id) = path.res {
2083                     let mut visitor =
2084                         TyAliasVisitor { tcx: self.tcx, preds: &mut self.preds, span: path.span };
2085                     self.tcx.type_of(def_id).visit_with(&mut visitor);
2086                 }
2087             }
2088
2089             intravisit::walk_ty(self, ty)
2090         }
2091     }
2092
2093     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2094     let node = tcx.hir().get(hir_id);
2095
2096     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2097     if let hir::Node::Item(item) = node {
2098         if let hir::ItemKind::Impl { ref of_trait, ref self_ty, .. } = item.kind {
2099             if let Some(of_trait) = of_trait {
2100                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2101                 collector.visit_trait_ref(of_trait);
2102             }
2103
2104             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2105             collector.visit_ty(self_ty);
2106         }
2107     }
2108
2109     if let Some(generics) = node.generics() {
2110         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2111         collector.visit_generics(generics);
2112     }
2113
2114     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2115         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2116         collector.visit_fn_decl(fn_sig.decl);
2117     }
2118     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2119
2120     collector.preds
2121 }
2122
2123 fn trait_explicit_predicates_and_bounds(
2124     tcx: TyCtxt<'_>,
2125     def_id: LocalDefId,
2126 ) -> ty::GenericPredicates<'_> {
2127     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2128     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2129 }
2130
2131 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2132     if let DefKind::Trait = tcx.def_kind(def_id) {
2133         // Remove bounds on associated types from the predicates, they will be
2134         // returned by `explicit_item_bounds`.
2135         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2136         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2137
2138         let is_assoc_item_ty = |ty: Ty<'_>| {
2139             // For a predicate from a where clause to become a bound on an
2140             // associated type:
2141             // * It must use the identity substs of the item.
2142             //     * Since any generic parameters on the item are not in scope,
2143             //       this means that the item is not a GAT, and its identity
2144             //       substs are the same as the trait's.
2145             // * It must be an associated type for this trait (*not* a
2146             //   supertrait).
2147             if let ty::Projection(projection) = ty.kind() {
2148                 projection.substs == trait_identity_substs
2149                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2150             } else {
2151                 false
2152             }
2153         };
2154
2155         let predicates: Vec<_> = predicates_and_bounds
2156             .predicates
2157             .iter()
2158             .copied()
2159             .filter(|(pred, _)| match pred.skip_binders() {
2160                 ty::PredicateAtom::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
2161                 ty::PredicateAtom::Projection(proj) => {
2162                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2163                 }
2164                 ty::PredicateAtom::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2165                 _ => true,
2166             })
2167             .collect();
2168         if predicates.len() == predicates_and_bounds.predicates.len() {
2169             predicates_and_bounds
2170         } else {
2171             ty::GenericPredicates {
2172                 parent: predicates_and_bounds.parent,
2173                 predicates: tcx.arena.alloc_slice(&predicates),
2174             }
2175         }
2176     } else {
2177         gather_explicit_predicates_of(tcx, def_id)
2178     }
2179 }
2180
2181 fn projection_ty_from_predicates(
2182     tcx: TyCtxt<'tcx>,
2183     key: (
2184         // ty_def_id
2185         DefId,
2186         // def_id of `N` in `<T as Trait>::N`
2187         DefId,
2188     ),
2189 ) -> Option<ty::ProjectionTy<'tcx>> {
2190     let (ty_def_id, item_def_id) = key;
2191     let mut projection_ty = None;
2192     for (predicate, _) in tcx.predicates_of(ty_def_id).predicates {
2193         if let ty::PredicateAtom::Projection(projection_predicate) = predicate.skip_binders() {
2194             if item_def_id == projection_predicate.projection_ty.item_def_id {
2195                 projection_ty = Some(projection_predicate.projection_ty);
2196                 break;
2197             }
2198         }
2199     }
2200     projection_ty
2201 }
2202
2203 /// Converts a specific `GenericBound` from the AST into a set of
2204 /// predicates that apply to the self type. A vector is returned
2205 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2206 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2207 /// and `<T as Bar>::X == i32`).
2208 fn predicates_from_bound<'tcx>(
2209     astconv: &dyn AstConv<'tcx>,
2210     param_ty: Ty<'tcx>,
2211     bound: &'tcx hir::GenericBound<'tcx>,
2212     constness: hir::Constness,
2213 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2214     match *bound {
2215         hir::GenericBound::Trait(ref tr, modifier) => {
2216             let constness = match modifier {
2217                 hir::TraitBoundModifier::Maybe => return vec![],
2218                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2219                 hir::TraitBoundModifier::None => constness,
2220             };
2221
2222             let mut bounds = Bounds::default();
2223             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2224             bounds.predicates(astconv.tcx(), param_ty)
2225         }
2226         hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2227             let mut bounds = Bounds::default();
2228             astconv.instantiate_lang_item_trait_ref(
2229                 lang_item,
2230                 span,
2231                 hir_id,
2232                 args,
2233                 param_ty,
2234                 &mut bounds,
2235             );
2236             bounds.predicates(astconv.tcx(), param_ty)
2237         }
2238         hir::GenericBound::Outlives(ref lifetime) => {
2239             let region = astconv.ast_region_to_region(lifetime, None);
2240             let pred = ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2241                 .to_predicate(astconv.tcx());
2242             vec![(pred, lifetime.span)]
2243         }
2244     }
2245 }
2246
2247 fn compute_sig_of_foreign_fn_decl<'tcx>(
2248     tcx: TyCtxt<'tcx>,
2249     def_id: DefId,
2250     decl: &'tcx hir::FnDecl<'tcx>,
2251     abi: abi::Abi,
2252     ident: Ident,
2253 ) -> ty::PolyFnSig<'tcx> {
2254     let unsafety = if abi == abi::Abi::RustIntrinsic {
2255         intrinsic_operation_unsafety(tcx.item_name(def_id))
2256     } else {
2257         hir::Unsafety::Unsafe
2258     };
2259     let fty = AstConv::ty_of_fn(
2260         &ItemCtxt::new(tcx, def_id),
2261         unsafety,
2262         abi,
2263         decl,
2264         &hir::Generics::empty(),
2265         Some(ident.span),
2266     );
2267
2268     // Feature gate SIMD types in FFI, since I am not sure that the
2269     // ABIs are handled at all correctly. -huonw
2270     if abi != abi::Abi::RustIntrinsic
2271         && abi != abi::Abi::PlatformIntrinsic
2272         && !tcx.features().simd_ffi
2273     {
2274         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2275             if ty.is_simd() {
2276                 let snip = tcx
2277                     .sess
2278                     .source_map()
2279                     .span_to_snippet(ast_ty.span)
2280                     .map_or(String::new(), |s| format!(" `{}`", s));
2281                 tcx.sess
2282                     .struct_span_err(
2283                         ast_ty.span,
2284                         &format!(
2285                             "use of SIMD type{} in FFI is highly experimental and \
2286                              may result in invalid code",
2287                             snip
2288                         ),
2289                     )
2290                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2291                     .emit();
2292             }
2293         };
2294         for (input, ty) in decl.inputs.iter().zip(fty.inputs().skip_binder()) {
2295             check(&input, ty)
2296         }
2297         if let hir::FnRetTy::Return(ref ty) = decl.output {
2298             check(&ty, fty.output().skip_binder())
2299         }
2300     }
2301
2302     fty
2303 }
2304
2305 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2306     match tcx.hir().get_if_local(def_id) {
2307         Some(Node::ForeignItem(..)) => true,
2308         Some(_) => false,
2309         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2310     }
2311 }
2312
2313 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2314     match tcx.hir().get_if_local(def_id) {
2315         Some(
2316             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2317             | Node::ForeignItem(&hir::ForeignItem {
2318                 kind: hir::ForeignItemKind::Static(_, mutbl),
2319                 ..
2320             }),
2321         ) => Some(mutbl),
2322         Some(_) => None,
2323         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2324     }
2325 }
2326
2327 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2328     match tcx.hir().get_if_local(def_id) {
2329         Some(Node::Expr(&rustc_hir::Expr {
2330             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2331             ..
2332         })) => tcx.hir().body(body_id).generator_kind(),
2333         Some(_) => None,
2334         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2335     }
2336 }
2337
2338 fn from_target_feature(
2339     tcx: TyCtxt<'_>,
2340     id: DefId,
2341     attr: &ast::Attribute,
2342     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2343     target_features: &mut Vec<Symbol>,
2344 ) {
2345     let list = match attr.meta_item_list() {
2346         Some(list) => list,
2347         None => return,
2348     };
2349     let bad_item = |span| {
2350         let msg = "malformed `target_feature` attribute input";
2351         let code = "enable = \"..\"".to_owned();
2352         tcx.sess
2353             .struct_span_err(span, &msg)
2354             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2355             .emit();
2356     };
2357     let rust_features = tcx.features();
2358     for item in list {
2359         // Only `enable = ...` is accepted in the meta-item list.
2360         if !item.has_name(sym::enable) {
2361             bad_item(item.span());
2362             continue;
2363         }
2364
2365         // Must be of the form `enable = "..."` (a string).
2366         let value = match item.value_str() {
2367             Some(value) => value,
2368             None => {
2369                 bad_item(item.span());
2370                 continue;
2371             }
2372         };
2373
2374         // We allow comma separation to enable multiple features.
2375         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2376             let feature_gate = match supported_target_features.get(feature) {
2377                 Some(g) => g,
2378                 None => {
2379                     let msg =
2380                         format!("the feature named `{}` is not valid for this target", feature);
2381                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2382                     err.span_label(
2383                         item.span(),
2384                         format!("`{}` is not valid for this target", feature),
2385                     );
2386                     if let Some(stripped) = feature.strip_prefix('+') {
2387                         let valid = supported_target_features.contains_key(stripped);
2388                         if valid {
2389                             err.help("consider removing the leading `+` in the feature name");
2390                         }
2391                     }
2392                     err.emit();
2393                     return None;
2394                 }
2395             };
2396
2397             // Only allow features whose feature gates have been enabled.
2398             let allowed = match feature_gate.as_ref().copied() {
2399                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2400                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2401                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2402                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2403                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2404                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2405                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2406                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2407                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2408                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2409                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2410                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2411                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2412                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2413                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2414                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2415                 Some(name) => bug!("unknown target feature gate {}", name),
2416                 None => true,
2417             };
2418             if !allowed && id.is_local() {
2419                 feature_err(
2420                     &tcx.sess.parse_sess,
2421                     feature_gate.unwrap(),
2422                     item.span(),
2423                     &format!("the target feature `{}` is currently unstable", feature),
2424                 )
2425                 .emit();
2426             }
2427             Some(Symbol::intern(feature))
2428         }));
2429     }
2430 }
2431
2432 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2433     use rustc_middle::mir::mono::Linkage::*;
2434
2435     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2436     // applicable to variable declarations and may not really make sense for
2437     // Rust code in the first place but allow them anyway and trust that the
2438     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2439     // up in the future.
2440     //
2441     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2442     // and don't have to be, LLVM treats them as no-ops.
2443     match name {
2444         "appending" => Appending,
2445         "available_externally" => AvailableExternally,
2446         "common" => Common,
2447         "extern_weak" => ExternalWeak,
2448         "external" => External,
2449         "internal" => Internal,
2450         "linkonce" => LinkOnceAny,
2451         "linkonce_odr" => LinkOnceODR,
2452         "private" => Private,
2453         "weak" => WeakAny,
2454         "weak_odr" => WeakODR,
2455         _ => {
2456             let span = tcx.hir().span_if_local(def_id);
2457             if let Some(span) = span {
2458                 tcx.sess.span_fatal(span, "invalid linkage specified")
2459             } else {
2460                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2461             }
2462         }
2463     }
2464 }
2465
2466 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2467     let attrs = tcx.get_attrs(id);
2468
2469     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2470     if should_inherit_track_caller(tcx, id) {
2471         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2472     }
2473
2474     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2475
2476     let mut inline_span = None;
2477     let mut link_ordinal_span = None;
2478     let mut no_sanitize_span = None;
2479     for attr in attrs.iter() {
2480         if tcx.sess.check_name(attr, sym::cold) {
2481             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2482         } else if tcx.sess.check_name(attr, sym::rustc_allocator) {
2483             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2484         } else if tcx.sess.check_name(attr, sym::unwind) {
2485             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2486         } else if tcx.sess.check_name(attr, sym::ffi_returns_twice) {
2487             if tcx.is_foreign_item(id) {
2488                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2489             } else {
2490                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2491                 struct_span_err!(
2492                     tcx.sess,
2493                     attr.span,
2494                     E0724,
2495                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2496                 )
2497                 .emit();
2498             }
2499         } else if tcx.sess.check_name(attr, sym::ffi_pure) {
2500             if tcx.is_foreign_item(id) {
2501                 if attrs.iter().any(|a| tcx.sess.check_name(a, sym::ffi_const)) {
2502                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2503                     struct_span_err!(
2504                         tcx.sess,
2505                         attr.span,
2506                         E0757,
2507                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2508                     )
2509                     .emit();
2510                 } else {
2511                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2512                 }
2513             } else {
2514                 // `#[ffi_pure]` is only allowed on foreign functions
2515                 struct_span_err!(
2516                     tcx.sess,
2517                     attr.span,
2518                     E0755,
2519                     "`#[ffi_pure]` may only be used on foreign functions"
2520                 )
2521                 .emit();
2522             }
2523         } else if tcx.sess.check_name(attr, sym::ffi_const) {
2524             if tcx.is_foreign_item(id) {
2525                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2526             } else {
2527                 // `#[ffi_const]` is only allowed on foreign functions
2528                 struct_span_err!(
2529                     tcx.sess,
2530                     attr.span,
2531                     E0756,
2532                     "`#[ffi_const]` may only be used on foreign functions"
2533                 )
2534                 .emit();
2535             }
2536         } else if tcx.sess.check_name(attr, sym::rustc_allocator_nounwind) {
2537             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2538         } else if tcx.sess.check_name(attr, sym::naked) {
2539             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2540         } else if tcx.sess.check_name(attr, sym::no_mangle) {
2541             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2542         } else if tcx.sess.check_name(attr, sym::rustc_std_internal_symbol) {
2543             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2544         } else if tcx.sess.check_name(attr, sym::used) {
2545             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2546         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
2547             if tcx.fn_sig(id).abi() != abi::Abi::C {
2548                 struct_span_err!(
2549                     tcx.sess,
2550                     attr.span,
2551                     E0776,
2552                     "`#[cmse_nonsecure_entry]` requires C ABI"
2553                 )
2554                 .emit();
2555             }
2556             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2557                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2558                     .emit();
2559             }
2560             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2561         } else if tcx.sess.check_name(attr, sym::thread_local) {
2562             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2563         } else if tcx.sess.check_name(attr, sym::track_caller) {
2564             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2565                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2566                     .emit();
2567             }
2568             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2569         } else if tcx.sess.check_name(attr, sym::export_name) {
2570             if let Some(s) = attr.value_str() {
2571                 if s.as_str().contains('\0') {
2572                     // `#[export_name = ...]` will be converted to a null-terminated string,
2573                     // so it may not contain any null characters.
2574                     struct_span_err!(
2575                         tcx.sess,
2576                         attr.span,
2577                         E0648,
2578                         "`export_name` may not contain null characters"
2579                     )
2580                     .emit();
2581                 }
2582                 codegen_fn_attrs.export_name = Some(s);
2583             }
2584         } else if tcx.sess.check_name(attr, sym::target_feature) {
2585             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2586                 if !tcx.features().target_feature_11 {
2587                     let mut err = feature_err(
2588                         &tcx.sess.parse_sess,
2589                         sym::target_feature_11,
2590                         attr.span,
2591                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2592                     );
2593                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2594                     err.emit();
2595                 } else if let Some(local_id) = id.as_local() {
2596                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2597                 }
2598             }
2599             from_target_feature(
2600                 tcx,
2601                 id,
2602                 attr,
2603                 &supported_target_features,
2604                 &mut codegen_fn_attrs.target_features,
2605             );
2606         } else if tcx.sess.check_name(attr, sym::linkage) {
2607             if let Some(val) = attr.value_str() {
2608                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2609             }
2610         } else if tcx.sess.check_name(attr, sym::link_section) {
2611             if let Some(val) = attr.value_str() {
2612                 if val.as_str().bytes().any(|b| b == 0) {
2613                     let msg = format!(
2614                         "illegal null byte in link_section \
2615                          value: `{}`",
2616                         &val
2617                     );
2618                     tcx.sess.span_err(attr.span, &msg);
2619                 } else {
2620                     codegen_fn_attrs.link_section = Some(val);
2621                 }
2622             }
2623         } else if tcx.sess.check_name(attr, sym::link_name) {
2624             codegen_fn_attrs.link_name = attr.value_str();
2625         } else if tcx.sess.check_name(attr, sym::link_ordinal) {
2626             link_ordinal_span = Some(attr.span);
2627             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2628                 codegen_fn_attrs.link_ordinal = ordinal;
2629             }
2630         } else if tcx.sess.check_name(attr, sym::no_sanitize) {
2631             no_sanitize_span = Some(attr.span);
2632             if let Some(list) = attr.meta_item_list() {
2633                 for item in list.iter() {
2634                     if item.has_name(sym::address) {
2635                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2636                     } else if item.has_name(sym::memory) {
2637                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2638                     } else if item.has_name(sym::thread) {
2639                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2640                     } else {
2641                         tcx.sess
2642                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2643                             .note("expected one of: `address`, `memory` or `thread`")
2644                             .emit();
2645                     }
2646                 }
2647             }
2648         } else if tcx.sess.check_name(attr, sym::instruction_set) {
2649             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2650                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2651                     [NestedMetaItem::MetaItem(set)] => {
2652                         let segments =
2653                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2654                         match segments.as_slice() {
2655                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2656                                 if !tcx.sess.target.has_thumb_interworking {
2657                                     struct_span_err!(
2658                                         tcx.sess.diagnostic(),
2659                                         attr.span,
2660                                         E0779,
2661                                         "target does not support `#[instruction_set]`"
2662                                     )
2663                                     .emit();
2664                                     None
2665                                 } else if segments[1] == sym::a32 {
2666                                     Some(InstructionSetAttr::ArmA32)
2667                                 } else if segments[1] == sym::t32 {
2668                                     Some(InstructionSetAttr::ArmT32)
2669                                 } else {
2670                                     unreachable!()
2671                                 }
2672                             }
2673                             _ => {
2674                                 struct_span_err!(
2675                                     tcx.sess.diagnostic(),
2676                                     attr.span,
2677                                     E0779,
2678                                     "invalid instruction set specified",
2679                                 )
2680                                 .emit();
2681                                 None
2682                             }
2683                         }
2684                     }
2685                     [] => {
2686                         struct_span_err!(
2687                             tcx.sess.diagnostic(),
2688                             attr.span,
2689                             E0778,
2690                             "`#[instruction_set]` requires an argument"
2691                         )
2692                         .emit();
2693                         None
2694                     }
2695                     _ => {
2696                         struct_span_err!(
2697                             tcx.sess.diagnostic(),
2698                             attr.span,
2699                             E0779,
2700                             "cannot specify more than one instruction set"
2701                         )
2702                         .emit();
2703                         None
2704                     }
2705                 },
2706                 _ => {
2707                     struct_span_err!(
2708                         tcx.sess.diagnostic(),
2709                         attr.span,
2710                         E0778,
2711                         "must specify an instruction set"
2712                     )
2713                     .emit();
2714                     None
2715                 }
2716             };
2717         }
2718     }
2719
2720     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2721         if !attr.has_name(sym::inline) {
2722             return ia;
2723         }
2724         match attr.meta().map(|i| i.kind) {
2725             Some(MetaItemKind::Word) => {
2726                 tcx.sess.mark_attr_used(attr);
2727                 InlineAttr::Hint
2728             }
2729             Some(MetaItemKind::List(ref items)) => {
2730                 tcx.sess.mark_attr_used(attr);
2731                 inline_span = Some(attr.span);
2732                 if items.len() != 1 {
2733                     struct_span_err!(
2734                         tcx.sess.diagnostic(),
2735                         attr.span,
2736                         E0534,
2737                         "expected one argument"
2738                     )
2739                     .emit();
2740                     InlineAttr::None
2741                 } else if list_contains_name(&items[..], sym::always) {
2742                     InlineAttr::Always
2743                 } else if list_contains_name(&items[..], sym::never) {
2744                     InlineAttr::Never
2745                 } else {
2746                     struct_span_err!(
2747                         tcx.sess.diagnostic(),
2748                         items[0].span(),
2749                         E0535,
2750                         "invalid argument"
2751                     )
2752                     .emit();
2753
2754                     InlineAttr::None
2755                 }
2756             }
2757             Some(MetaItemKind::NameValue(_)) => ia,
2758             None => ia,
2759         }
2760     });
2761
2762     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2763         if !attr.has_name(sym::optimize) {
2764             return ia;
2765         }
2766         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2767         match attr.meta().map(|i| i.kind) {
2768             Some(MetaItemKind::Word) => {
2769                 err(attr.span, "expected one argument");
2770                 ia
2771             }
2772             Some(MetaItemKind::List(ref items)) => {
2773                 tcx.sess.mark_attr_used(attr);
2774                 inline_span = Some(attr.span);
2775                 if items.len() != 1 {
2776                     err(attr.span, "expected one argument");
2777                     OptimizeAttr::None
2778                 } else if list_contains_name(&items[..], sym::size) {
2779                     OptimizeAttr::Size
2780                 } else if list_contains_name(&items[..], sym::speed) {
2781                     OptimizeAttr::Speed
2782                 } else {
2783                     err(items[0].span(), "invalid argument");
2784                     OptimizeAttr::None
2785                 }
2786             }
2787             Some(MetaItemKind::NameValue(_)) => ia,
2788             None => ia,
2789         }
2790     });
2791
2792     // #73631: closures inherit `#[target_feature]` annotations
2793     if tcx.features().target_feature_11 && tcx.is_closure(id) {
2794         let owner_id = tcx.parent(id).expect("closure should have a parent");
2795         codegen_fn_attrs
2796             .target_features
2797             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
2798     }
2799
2800     // If a function uses #[target_feature] it can't be inlined into general
2801     // purpose functions as they wouldn't have the right target features
2802     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2803     // respected.
2804     if !codegen_fn_attrs.target_features.is_empty() {
2805         if codegen_fn_attrs.inline == InlineAttr::Always {
2806             if let Some(span) = inline_span {
2807                 tcx.sess.span_err(
2808                     span,
2809                     "cannot use `#[inline(always)]` with \
2810                      `#[target_feature]`",
2811                 );
2812             }
2813         }
2814     }
2815
2816     if !codegen_fn_attrs.no_sanitize.is_empty() {
2817         if codegen_fn_attrs.inline == InlineAttr::Always {
2818             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2819                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
2820                 tcx.struct_span_lint_hir(
2821                     lint::builtin::INLINE_NO_SANITIZE,
2822                     hir_id,
2823                     no_sanitize_span,
2824                     |lint| {
2825                         lint.build("`no_sanitize` will have no effect after inlining")
2826                             .span_note(inline_span, "inlining requested here")
2827                             .emit();
2828                     },
2829                 )
2830             }
2831         }
2832     }
2833
2834     // Weak lang items have the same semantics as "std internal" symbols in the
2835     // sense that they're preserved through all our LTO passes and only
2836     // strippable by the linker.
2837     //
2838     // Additionally weak lang items have predetermined symbol names.
2839     if tcx.is_weak_lang_item(id) {
2840         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2841     }
2842     let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
2843     if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
2844         codegen_fn_attrs.export_name = Some(name);
2845         codegen_fn_attrs.link_name = Some(name);
2846     }
2847     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2848
2849     // Internal symbols to the standard library all have no_mangle semantics in
2850     // that they have defined symbol names present in the function name. This
2851     // also applies to weak symbols where they all have known symbol names.
2852     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2853         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2854     }
2855
2856     codegen_fn_attrs
2857 }
2858
2859 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
2860 /// applied to the method prototype.
2861 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2862     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
2863         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
2864             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
2865                 if let Some(trait_item) = tcx
2866                     .associated_items(trait_def_id)
2867                     .filter_by_name_unhygienic(impl_item.ident.name)
2868                     .find(move |trait_item| {
2869                         trait_item.kind == ty::AssocKind::Fn
2870                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
2871                     })
2872                 {
2873                     return tcx
2874                         .codegen_fn_attrs(trait_item.def_id)
2875                         .flags
2876                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
2877                 }
2878             }
2879         }
2880     }
2881
2882     false
2883 }
2884
2885 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2886     use rustc_ast::{Lit, LitIntType, LitKind};
2887     let meta_item_list = attr.meta_item_list();
2888     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2889     let sole_meta_list = match meta_item_list {
2890         Some([item]) => item.literal(),
2891         _ => None,
2892     };
2893     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2894         if *ordinal <= usize::MAX as u128 {
2895             Some(*ordinal as usize)
2896         } else {
2897             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2898             tcx.sess
2899                 .struct_span_err(attr.span, &msg)
2900                 .note("the value may not exceed `usize::MAX`")
2901                 .emit();
2902             None
2903         }
2904     } else {
2905         tcx.sess
2906             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2907             .note("an unsuffixed integer value, e.g., `1`, is expected")
2908             .emit();
2909         None
2910     }
2911 }
2912
2913 fn check_link_name_xor_ordinal(
2914     tcx: TyCtxt<'_>,
2915     codegen_fn_attrs: &CodegenFnAttrs,
2916     inline_span: Option<Span>,
2917 ) {
2918     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2919         return;
2920     }
2921     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2922     if let Some(span) = inline_span {
2923         tcx.sess.span_err(span, msg);
2924     } else {
2925         tcx.sess.err(msg);
2926     }
2927 }
2928
2929 /// Checks the function annotated with `#[target_feature]` is not a safe
2930 /// trait method implementation, reporting an error if it is.
2931 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
2932     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
2933     let node = tcx.hir().get(hir_id);
2934     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
2935         let parent_id = tcx.hir().get_parent_item(hir_id);
2936         let parent_item = tcx.hir().expect_item(parent_id);
2937         if let hir::ItemKind::Impl { of_trait: Some(_), .. } = parent_item.kind {
2938             tcx.sess
2939                 .struct_span_err(
2940                     attr_span,
2941                     "`#[target_feature(..)]` cannot be applied to safe trait method",
2942                 )
2943                 .span_label(attr_span, "cannot be applied to safe trait method")
2944                 .span_label(tcx.def_span(id), "not an `unsafe` function")
2945                 .emit();
2946         }
2947     }
2948 }