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
 160         .iter()
 161         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 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                 // `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<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1373
1374     if let Some(opt_self) = opt_self {
1375         params.push(opt_self);
1376     }
1377
1378     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1379     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1380         name: param.name.ident().name,
1381         index: own_start + i as u32,
1382         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1383         pure_wrt_drop: param.pure_wrt_drop,
1384         kind: ty::GenericParamDefKind::Lifetime,
1385     }));
1386
1387     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1388
1389     // Now create the real type and const parameters.
1390     let type_start = own_start - has_self as u32 + params.len() as u32;
1391     let mut i = 0;
1392
1393     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1394         GenericParamKind::Lifetime { .. } => None,
1395         GenericParamKind::Type { ref default, synthetic, .. } => {
1396             if !allow_defaults && default.is_some() {
1397                 if !tcx.features().default_type_parameter_fallback {
1398                     tcx.struct_span_lint_hir(
1399                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1400                         param.hir_id,
1401                         param.span,
1402                         |lint| {
1403                             lint.build(
1404                                 "defaults for type parameters are only allowed in \
1405                                  `struct`, `enum`, `type`, or `trait` definitions.",
1406                             )
1407                             .emit();
1408                         },
1409                     );
1410                 }
1411             }
1412
1413             let kind = ty::GenericParamDefKind::Type {
1414                 has_default: default.is_some(),
1415                 object_lifetime_default: object_lifetime_defaults
1416                     .as_ref()
1417                     .map_or(rl::Set1::Empty, |o| o[i]),
1418                 synthetic,
1419             };
1420
1421             let param_def = ty::GenericParamDef {
1422                 index: type_start + i as u32,
1423                 name: param.name.ident().name,
1424                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1425                 pure_wrt_drop: param.pure_wrt_drop,
1426                 kind,
1427             };
1428             i += 1;
1429             Some(param_def)
1430         }
1431         GenericParamKind::Const { .. } => {
1432             let param_def = ty::GenericParamDef {
1433                 index: type_start + i as u32,
1434                 name: param.name.ident().name,
1435                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1436                 pure_wrt_drop: param.pure_wrt_drop,
1437                 kind: ty::GenericParamDefKind::Const,
1438             };
1439             i += 1;
1440             Some(param_def)
1441         }
1442     }));
1443
1444     // provide junk type parameter defs - the only place that
1445     // cares about anything but the length is instantiation,
1446     // and we don't do that for closures.
1447     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1448         let dummy_args = if gen.is_some() {
1449             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1450         } else {
1451             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1452         };
1453
1454         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1455             index: type_start + i as u32,
1456             name: Symbol::intern(arg),
1457             def_id,
1458             pure_wrt_drop: false,
1459             kind: ty::GenericParamDefKind::Type {
1460                 has_default: false,
1461                 object_lifetime_default: rl::Set1::Empty,
1462                 synthetic: None,
1463             },
1464         }));
1465     }
1466
1467     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1468
1469     ty::Generics {
1470         parent: parent_def_id,
1471         parent_count,
1472         params,
1473         param_def_id_to_index,
1474         has_self: has_self || parent_has_self,
1475         has_late_bound_regions: has_late_bound_regions(tcx, node),
1476     }
1477 }
1478
1479 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1480     generic_args
1481         .iter()
1482         .filter_map(|arg| match arg {
1483             hir::GenericArg::Type(ty) => Some(ty),
1484             _ => None,
1485         })
1486         .any(is_suggestable_infer_ty)
1487 }
1488
1489 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1490 /// use inference to provide suggestions for the appropriate type if possible.
1491 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1492     use hir::TyKind::*;
1493     match &ty.kind {
1494         Infer => true,
1495         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1496         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1497         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1498         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1499         Path(hir::QPath::TypeRelative(ty, segment)) => {
1500             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1501         }
1502         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1503             ty_opt.map_or(false, is_suggestable_infer_ty)
1504                 || segments
1505                     .iter()
1506                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1507         }
1508         _ => false,
1509     }
1510 }
1511
1512 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1513     if let hir::FnRetTy::Return(ref ty) = output {
1514         if is_suggestable_infer_ty(ty) {
1515             return Some(&**ty);
1516         }
1517     }
1518     None
1519 }
1520
1521 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1522     use rustc_hir::Node::*;
1523     use rustc_hir::*;
1524
1525     let def_id = def_id.expect_local();
1526     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1527
1528     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1529
1530     match tcx.hir().get(hir_id) {
1531         TraitItem(hir::TraitItem {
1532             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1533             ident,
1534             generics,
1535             ..
1536         })
1537         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1538         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1539             match get_infer_ret_ty(&sig.decl.output) {
1540                 Some(ty) => {
1541                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1542                     let mut visitor = PlaceholderHirTyCollector::default();
1543                     visitor.visit_ty(ty);
1544                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1545                     let ret_ty = fn_sig.output();
1546                     if ret_ty != tcx.ty_error() {
1547                         if !ret_ty.is_closure() {
1548                             let ret_ty_str = match ret_ty.kind() {
1549                                 // Suggest a function pointer return type instead of a unique function definition
1550                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1551                                 // syntax)
1552                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1553                                 _ => ret_ty.to_string(),
1554                             };
1555                             diag.span_suggestion(
1556                                 ty.span,
1557                                 "replace with the correct return type",
1558                                 ret_ty_str,
1559                                 Applicability::MaybeIncorrect,
1560                             );
1561                         } else {
1562                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1563                             // to prevent the user from getting a papercut while trying to use the unique closure
1564                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1565                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1566                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1567                         }
1568                     }
1569                     diag.emit();
1570                     ty::Binder::bind(fn_sig)
1571                 }
1572                 None => AstConv::ty_of_fn(
1573                     &icx,
1574                     sig.header.unsafety,
1575                     sig.header.abi,
1576                     &sig.decl,
1577                     &generics,
1578                     Some(ident.span),
1579                 ),
1580             }
1581         }
1582
1583         TraitItem(hir::TraitItem {
1584             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1585             ident,
1586             generics,
1587             ..
1588         }) => {
1589             AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl, &generics, Some(ident.span))
1590         }
1591
1592         ForeignItem(&hir::ForeignItem {
1593             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1594             ident,
1595             ..
1596         }) => {
1597             let abi = tcx.hir().get_foreign_abi(hir_id);
1598             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1599         }
1600
1601         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1602             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1603             let inputs =
1604                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1605             ty::Binder::bind(tcx.mk_fn_sig(
1606                 inputs,
1607                 ty,
1608                 false,
1609                 hir::Unsafety::Normal,
1610                 abi::Abi::Rust,
1611             ))
1612         }
1613
1614         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1615             // Closure signatures are not like other function
1616             // signatures and cannot be accessed through `fn_sig`. For
1617             // example, a closure signature excludes the `self`
1618             // argument. In any case they are embedded within the
1619             // closure type as part of the `ClosureSubsts`.
1620             //
1621             // To get the signature of a closure, you should use the
1622             // `sig` method on the `ClosureSubsts`:
1623             //
1624             //    substs.as_closure().sig(def_id, tcx)
1625             bug!(
1626                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1627             );
1628         }
1629
1630         x => {
1631             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1632         }
1633     }
1634 }
1635
1636 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1637     let icx = ItemCtxt::new(tcx, def_id);
1638
1639     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1640     match tcx.hir().expect_item(hir_id).kind {
1641         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
1642             let selfty = tcx.type_of(def_id);
1643             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1644         }),
1645         _ => bug!(),
1646     }
1647 }
1648
1649 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1650     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1651     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1652     let item = tcx.hir().expect_item(hir_id);
1653     match &item.kind {
1654         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative(span), of_trait, .. } => {
1655             if is_rustc_reservation {
1656                 let span = span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(*span));
1657                 tcx.sess.span_err(span, "reservation impls can't be negative");
1658             }
1659             ty::ImplPolarity::Negative
1660         }
1661         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
1662             if is_rustc_reservation {
1663                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1664             }
1665             ty::ImplPolarity::Positive
1666         }
1667         hir::ItemKind::Impl {
1668             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
1669         } => {
1670             if is_rustc_reservation {
1671                 ty::ImplPolarity::Reservation
1672             } else {
1673                 ty::ImplPolarity::Positive
1674             }
1675         }
1676         ref item => bug!("impl_polarity: {:?} not an impl", item),
1677     }
1678 }
1679
1680 /// Returns the early-bound lifetimes declared in this generics
1681 /// listing. For anything other than fns/methods, this is just all
1682 /// the lifetimes that are declared. For fns or methods, we have to
1683 /// screen out those that do not appear in any where-clauses etc using
1684 /// `resolve_lifetime::early_bound_lifetimes`.
1685 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1686     tcx: TyCtxt<'tcx>,
1687     generics: &'a hir::Generics<'a>,
1688 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1689     generics.params.iter().filter(move |param| match param.kind {
1690         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1691         _ => false,
1692     })
1693 }
1694
1695 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1696 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1697 /// inferred constraints concerning which regions outlive other regions.
1698 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1699     debug!("predicates_defined_on({:?})", def_id);
1700     let mut result = tcx.explicit_predicates_of(def_id);
1701     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1702     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1703     if !inferred_outlives.is_empty() {
1704         debug!(
1705             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1706             def_id, inferred_outlives,
1707         );
1708         if result.predicates.is_empty() {
1709             result.predicates = inferred_outlives;
1710         } else {
1711             result.predicates = tcx
1712                 .arena
1713                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1714         }
1715     }
1716
1717     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1718     result
1719 }
1720
1721 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1722 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1723 /// `Self: Trait` predicates for traits.
1724 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1725     let mut result = tcx.predicates_defined_on(def_id);
1726
1727     if tcx.is_trait(def_id) {
1728         // For traits, add `Self: Trait` predicate. This is
1729         // not part of the predicates that a user writes, but it
1730         // is something that one must prove in order to invoke a
1731         // method or project an associated type.
1732         //
1733         // In the chalk setup, this predicate is not part of the
1734         // "predicates" for a trait item. But it is useful in
1735         // rustc because if you directly (e.g.) invoke a trait
1736         // method like `Trait::method(...)`, you must naturally
1737         // prove that the trait applies to the types that were
1738         // used, and adding the predicate into this list ensures
1739         // that this is done.
1740         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
1741         result.predicates =
1742             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
1743                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
1744                 span,
1745             ))));
1746     }
1747     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1748     result
1749 }
1750
1751 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1752 /// N.B., this does not include any implied/inferred constraints.
1753 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1754     use rustc_hir::*;
1755
1756     debug!("explicit_predicates_of(def_id={:?})", def_id);
1757
1758     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1759     let node = tcx.hir().get(hir_id);
1760
1761     let mut is_trait = None;
1762     let mut is_default_impl_trait = None;
1763
1764     let icx = ItemCtxt::new(tcx, def_id);
1765     let constness = icx.default_constness_for_trait_bounds();
1766
1767     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
1768
1769     // We use an `IndexSet` to preserves order of insertion.
1770     // Preserving the order of insertion is important here so as not to break UI tests.
1771     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
1772
1773     let ast_generics = match node {
1774         Node::TraitItem(item) => &item.generics,
1775
1776         Node::ImplItem(item) => &item.generics,
1777
1778         Node::Item(item) => {
1779             match item.kind {
1780                 ItemKind::Impl { defaultness, ref generics, .. } => {
1781                     if defaultness.is_default() {
1782                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
1783                     }
1784                     generics
1785                 }
1786                 ItemKind::Fn(.., ref generics, _)
1787                 | ItemKind::TyAlias(_, ref generics)
1788                 | ItemKind::Enum(_, ref generics)
1789                 | ItemKind::Struct(_, ref generics)
1790                 | ItemKind::Union(_, ref generics) => generics,
1791
1792                 ItemKind::Trait(_, _, ref generics, ..) => {
1793                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1794                     generics
1795                 }
1796                 ItemKind::TraitAlias(ref generics, _) => {
1797                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1798                     generics
1799                 }
1800                 ItemKind::OpaqueTy(OpaqueTy {
1801                     bounds: _,
1802                     impl_trait_fn,
1803                     ref generics,
1804                     origin: _,
1805                 }) => {
1806                     if impl_trait_fn.is_some() {
1807                         // return-position impl trait
1808                         //
1809                         // We don't inherit predicates from the parent here:
1810                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
1811                         // then the return type is `f::<'static, T>::{{opaque}}`.
1812                         //
1813                         // If we inherited the predicates of `f` then we would
1814                         // require that `T: 'static` to show that the return
1815                         // type is well-formed.
1816                         //
1817                         // The only way to have something with this opaque type
1818                         // is from the return type of the containing function,
1819                         // which will ensure that the function's predicates
1820                         // hold.
1821                         return ty::GenericPredicates { parent: None, predicates: &[] };
1822                     } else {
1823                         // type-alias impl trait
1824                         generics
1825                     }
1826                 }
1827
1828                 _ => NO_GENERICS,
1829             }
1830         }
1831
1832         Node::ForeignItem(item) => match item.kind {
1833             ForeignItemKind::Static(..) => NO_GENERICS,
1834             ForeignItemKind::Fn(_, _, ref generics) => generics,
1835             ForeignItemKind::Type => NO_GENERICS,
1836         },
1837
1838         _ => NO_GENERICS,
1839     };
1840
1841     let generics = tcx.generics_of(def_id);
1842     let parent_count = generics.parent_count as u32;
1843     let has_own_self = generics.has_self && parent_count == 0;
1844
1845     // Below we'll consider the bounds on the type parameters (including `Self`)
1846     // and the explicit where-clauses, but to get the full set of predicates
1847     // on a trait we need to add in the supertrait bounds and bounds found on
1848     // associated types.
1849     if let Some(_trait_ref) = is_trait {
1850         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
1851     }
1852
1853     // In default impls, we can assume that the self type implements
1854     // the trait. So in:
1855     //
1856     //     default impl Foo for Bar { .. }
1857     //
1858     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
1859     // (see below). Recall that a default impl is not itself an impl, but rather a
1860     // set of defaults that can be incorporated into another impl.
1861     if let Some(trait_ref) = is_default_impl_trait {
1862         predicates.insert((
1863             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
1864             tcx.def_span(def_id),
1865         ));
1866     }
1867
1868     // Collect the region predicates that were declared inline as
1869     // well. In the case of parameters declared on a fn or method, we
1870     // have to be careful to only iterate over early-bound regions.
1871     let mut index = parent_count + has_own_self as u32;
1872     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
1873         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
1874             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1875             index,
1876             name: param.name.ident().name,
1877         }));
1878         index += 1;
1879
1880         match param.kind {
1881             GenericParamKind::Lifetime { .. } => {
1882                 param.bounds.iter().for_each(|bound| match bound {
1883                     hir::GenericBound::Outlives(lt) => {
1884                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
1885                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
1886                         predicates.insert((outlives.to_predicate(tcx), lt.span));
1887                     }
1888                     _ => bug!(),
1889                 });
1890             }
1891             _ => bug!(),
1892         }
1893     }
1894
1895     // Collect the predicates that were written inline by the user on each
1896     // type parameter (e.g., `<T: Foo>`).
1897     for param in ast_generics.params {
1898         match param.kind {
1899             // We already dealt with early bound lifetimes above.
1900             GenericParamKind::Lifetime { .. } => (),
1901             GenericParamKind::Type { .. } => {
1902                 let name = param.name.ident().name;
1903                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
1904                 index += 1;
1905
1906                 let sized = SizedByDefault::Yes;
1907                 let bounds =
1908                     AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
1909                 predicates.extend(bounds.predicates(tcx, param_ty));
1910             }
1911             GenericParamKind::Const { .. } => {
1912                 // Bounds on const parameters are currently not possible.
1913                 debug_assert!(param.bounds.is_empty());
1914                 index += 1;
1915             }
1916         }
1917     }
1918
1919     // Add in the bounds that appear in the where-clause.
1920     let where_clause = &ast_generics.where_clause;
1921     for predicate in where_clause.predicates {
1922         match predicate {
1923             hir::WherePredicate::BoundPredicate(bound_pred) => {
1924                 let ty = icx.to_ty(&bound_pred.bounded_ty);
1925
1926                 // Keep the type around in a dummy predicate, in case of no bounds.
1927                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
1928                 // is still checked for WF.
1929                 if bound_pred.bounds.is_empty() {
1930                     if let ty::Param(_) = ty.kind() {
1931                         // This is a `where T:`, which can be in the HIR from the
1932                         // transformation that moves `?Sized` to `T`'s declaration.
1933                         // We can skip the predicate because type parameters are
1934                         // trivially WF, but also we *should*, to avoid exposing
1935                         // users who never wrote `where Type:,` themselves, to
1936                         // compiler/tooling bugs from not handling WF predicates.
1937                     } else {
1938                         let span = bound_pred.bounded_ty.span;
1939                         let re_root_empty = tcx.lifetimes.re_root_empty;
1940                         let predicate = ty::Binder::bind(ty::PredicateAtom::TypeOutlives(
1941                             ty::OutlivesPredicate(ty, re_root_empty),
1942                         ));
1943                         predicates.insert((
1944                             predicate.potentially_quantified(tcx, ty::PredicateKind::ForAll),
1945                             span,
1946                         ));
1947                     }
1948                 }
1949
1950                 for bound in bound_pred.bounds.iter() {
1951                     match bound {
1952                         hir::GenericBound::Trait(poly_trait_ref, modifier) => {
1953                             let constness = match modifier {
1954                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
1955                                 hir::TraitBoundModifier::None => constness,
1956                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
1957                             };
1958
1959                             let mut bounds = Bounds::default();
1960                             let _ = AstConv::instantiate_poly_trait_ref(
1961                                 &icx,
1962                                 &poly_trait_ref,
1963                                 constness,
1964                                 ty,
1965                                 &mut bounds,
1966                             );
1967                             predicates.extend(bounds.predicates(tcx, ty));
1968                         }
1969
1970                         &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
1971                             let mut bounds = Bounds::default();
1972                             AstConv::instantiate_lang_item_trait_ref(
1973                                 &icx,
1974                                 lang_item,
1975                                 span,
1976                                 hir_id,
1977                                 args,
1978                                 ty,
1979                                 &mut bounds,
1980                             );
1981                             predicates.extend(bounds.predicates(tcx, ty));
1982                         }
1983
1984                         hir::GenericBound::Outlives(lifetime) => {
1985                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
1986                             predicates.insert((
1987                                 ty::Binder::bind(ty::PredicateAtom::TypeOutlives(
1988                                     ty::OutlivesPredicate(ty, region),
1989                                 ))
1990                                 .potentially_quantified(tcx, ty::PredicateKind::ForAll),
1991                                 lifetime.span,
1992                             ));
1993                         }
1994                     }
1995                 }
1996             }
1997
1998             hir::WherePredicate::RegionPredicate(region_pred) => {
1999                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2000                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2001                     let (r2, span) = match bound {
2002                         hir::GenericBound::Outlives(lt) => {
2003                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2004                         }
2005                         _ => bug!(),
2006                     };
2007                     let pred = ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(r1, r2))
2008                         .to_predicate(icx.tcx);
2009
2010                     (pred, span)
2011                 }))
2012             }
2013
2014             hir::WherePredicate::EqPredicate(..) => {
2015                 // FIXME(#20041)
2016             }
2017         }
2018     }
2019
2020     if tcx.features().const_evaluatable_checked {
2021         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2022     }
2023
2024     let mut predicates: Vec<_> = predicates.into_iter().collect();
2025
2026     // Subtle: before we store the predicates into the tcx, we
2027     // sort them so that predicates like `T: Foo<Item=U>` come
2028     // before uses of `U`.  This avoids false ambiguity errors
2029     // in trait checking. See `setup_constraining_predicates`
2030     // for details.
2031     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2032         let self_ty = tcx.type_of(def_id);
2033         let trait_ref = tcx.impl_trait_ref(def_id);
2034         cgp::setup_constraining_predicates(
2035             tcx,
2036             &mut predicates,
2037             trait_ref,
2038             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2039         );
2040     }
2041
2042     let result = ty::GenericPredicates {
2043         parent: generics.parent,
2044         predicates: tcx.arena.alloc_from_iter(predicates),
2045     };
2046     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2047     result
2048 }
2049
2050 fn const_evaluatable_predicates_of<'tcx>(
2051     tcx: TyCtxt<'tcx>,
2052     def_id: LocalDefId,
2053 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2054     struct ConstCollector<'tcx> {
2055         tcx: TyCtxt<'tcx>,
2056         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2057     }
2058
2059     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2060         type Map = Map<'tcx>;
2061
2062         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2063             intravisit::NestedVisitorMap::None
2064         }
2065
2066         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2067             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2068             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2069             if let ty::ConstKind::Unevaluated(def, substs, None) = ct.val {
2070                 let span = self.tcx.hir().span(c.hir_id);
2071                 self.preds.insert((
2072                     ty::PredicateAtom::ConstEvaluatable(def, substs).to_predicate(self.tcx),
2073                     span,
2074                 ));
2075             }
2076         }
2077
2078         // Look into `TyAlias`.
2079         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
2080             use ty::fold::{TypeFoldable, TypeVisitor};
2081             struct TyAliasVisitor<'a, 'tcx> {
2082                 tcx: TyCtxt<'tcx>,
2083                 preds: &'a mut FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2084                 span: Span,
2085             }
2086
2087             impl<'a, 'tcx> TypeVisitor<'tcx> for TyAliasVisitor<'a, 'tcx> {
2088                 fn visit_const(&mut self, ct: &'tcx Const<'tcx>) -> ControlFlow<Self::BreakTy> {
2089                     if let ty::ConstKind::Unevaluated(def, substs, None) = ct.val {
2090                         self.preds.insert((
2091                             ty::PredicateAtom::ConstEvaluatable(def, substs).to_predicate(self.tcx),
2092                             self.span,
2093                         ));
2094                     }
2095                     ControlFlow::CONTINUE
2096                 }
2097             }
2098
2099             if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = ty.kind {
2100                 if let Res::Def(DefKind::TyAlias, def_id) = path.res {
2101                     let mut visitor =
2102                         TyAliasVisitor { tcx: self.tcx, preds: &mut self.preds, span: path.span };
2103                     self.tcx.type_of(def_id).visit_with(&mut visitor);
2104                 }
2105             }
2106
2107             intravisit::walk_ty(self, ty)
2108         }
2109     }
2110
2111     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2112     let node = tcx.hir().get(hir_id);
2113
2114     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2115     if let hir::Node::Item(item) = node {
2116         if let hir::ItemKind::Impl { ref of_trait, ref self_ty, .. } = item.kind {
2117             if let Some(of_trait) = of_trait {
2118                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2119                 collector.visit_trait_ref(of_trait);
2120             }
2121
2122             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2123             collector.visit_ty(self_ty);
2124         }
2125     }
2126
2127     if let Some(generics) = node.generics() {
2128         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2129         collector.visit_generics(generics);
2130     }
2131
2132     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2133         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2134         collector.visit_fn_decl(fn_sig.decl);
2135     }
2136     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2137
2138     collector.preds
2139 }
2140
2141 fn trait_explicit_predicates_and_bounds(
2142     tcx: TyCtxt<'_>,
2143     def_id: LocalDefId,
2144 ) -> ty::GenericPredicates<'_> {
2145     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2146     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2147 }
2148
2149 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2150     if let DefKind::Trait = tcx.def_kind(def_id) {
2151         // Remove bounds on associated types from the predicates, they will be
2152         // returned by `explicit_item_bounds`.
2153         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2154         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2155
2156         let is_assoc_item_ty = |ty: Ty<'_>| {
2157             // For a predicate from a where clause to become a bound on an
2158             // associated type:
2159             // * It must use the identity substs of the item.
2160             //     * Since any generic parameters on the item are not in scope,
2161             //       this means that the item is not a GAT, and its identity
2162             //       substs are the same as the trait's.
2163             // * It must be an associated type for this trait (*not* a
2164             //   supertrait).
2165             if let ty::Projection(projection) = ty.kind() {
2166                 projection.substs == trait_identity_substs
2167                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2168             } else {
2169                 false
2170             }
2171         };
2172
2173         let predicates: Vec<_> = predicates_and_bounds
2174             .predicates
2175             .iter()
2176             .copied()
2177             .filter(|(pred, _)| match pred.skip_binders() {
2178                 ty::PredicateAtom::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
2179                 ty::PredicateAtom::Projection(proj) => {
2180                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2181                 }
2182                 ty::PredicateAtom::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2183                 _ => true,
2184             })
2185             .collect();
2186         if predicates.len() == predicates_and_bounds.predicates.len() {
2187             predicates_and_bounds
2188         } else {
2189             ty::GenericPredicates {
2190                 parent: predicates_and_bounds.parent,
2191                 predicates: tcx.arena.alloc_slice(&predicates),
2192             }
2193         }
2194     } else {
2195         gather_explicit_predicates_of(tcx, def_id)
2196     }
2197 }
2198
2199 fn projection_ty_from_predicates(
2200     tcx: TyCtxt<'tcx>,
2201     key: (
2202         // ty_def_id
2203         DefId,
2204         // def_id of `N` in `<T as Trait>::N`
2205         DefId,
2206     ),
2207 ) -> Option<ty::ProjectionTy<'tcx>> {
2208     let (ty_def_id, item_def_id) = key;
2209     let mut projection_ty = None;
2210     for (predicate, _) in tcx.predicates_of(ty_def_id).predicates {
2211         if let ty::PredicateAtom::Projection(projection_predicate) = predicate.skip_binders() {
2212             if item_def_id == projection_predicate.projection_ty.item_def_id {
2213                 projection_ty = Some(projection_predicate.projection_ty);
2214                 break;
2215             }
2216         }
2217     }
2218     projection_ty
2219 }
2220
2221 /// Converts a specific `GenericBound` from the AST into a set of
2222 /// predicates that apply to the self type. A vector is returned
2223 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2224 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2225 /// and `<T as Bar>::X == i32`).
2226 fn predicates_from_bound<'tcx>(
2227     astconv: &dyn AstConv<'tcx>,
2228     param_ty: Ty<'tcx>,
2229     bound: &'tcx hir::GenericBound<'tcx>,
2230     constness: hir::Constness,
2231 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2232     match *bound {
2233         hir::GenericBound::Trait(ref tr, modifier) => {
2234             let constness = match modifier {
2235                 hir::TraitBoundModifier::Maybe => return vec![],
2236                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2237                 hir::TraitBoundModifier::None => constness,
2238             };
2239
2240             let mut bounds = Bounds::default();
2241             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2242             bounds.predicates(astconv.tcx(), param_ty)
2243         }
2244         hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2245             let mut bounds = Bounds::default();
2246             astconv.instantiate_lang_item_trait_ref(
2247                 lang_item,
2248                 span,
2249                 hir_id,
2250                 args,
2251                 param_ty,
2252                 &mut bounds,
2253             );
2254             bounds.predicates(astconv.tcx(), param_ty)
2255         }
2256         hir::GenericBound::Outlives(ref lifetime) => {
2257             let region = astconv.ast_region_to_region(lifetime, None);
2258             let pred = ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2259                 .to_predicate(astconv.tcx());
2260             vec![(pred, lifetime.span)]
2261         }
2262     }
2263 }
2264
2265 fn compute_sig_of_foreign_fn_decl<'tcx>(
2266     tcx: TyCtxt<'tcx>,
2267     def_id: DefId,
2268     decl: &'tcx hir::FnDecl<'tcx>,
2269     abi: abi::Abi,
2270     ident: Ident,
2271 ) -> ty::PolyFnSig<'tcx> {
2272     let unsafety = if abi == abi::Abi::RustIntrinsic {
2273         intrinsic_operation_unsafety(tcx.item_name(def_id))
2274     } else {
2275         hir::Unsafety::Unsafe
2276     };
2277     let fty = AstConv::ty_of_fn(
2278         &ItemCtxt::new(tcx, def_id),
2279         unsafety,
2280         abi,
2281         decl,
2282         &hir::Generics::empty(),
2283         Some(ident.span),
2284     );
2285
2286     // Feature gate SIMD types in FFI, since I am not sure that the
2287     // ABIs are handled at all correctly. -huonw
2288     if abi != abi::Abi::RustIntrinsic
2289         && abi != abi::Abi::PlatformIntrinsic
2290         && !tcx.features().simd_ffi
2291     {
2292         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2293             if ty.is_simd() {
2294                 let snip = tcx
2295                     .sess
2296                     .source_map()
2297                     .span_to_snippet(ast_ty.span)
2298                     .map_or(String::new(), |s| format!(" `{}`", s));
2299                 tcx.sess
2300                     .struct_span_err(
2301                         ast_ty.span,
2302                         &format!(
2303                             "use of SIMD type{} in FFI is highly experimental and \
2304                              may result in invalid code",
2305                             snip
2306                         ),
2307                     )
2308                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2309                     .emit();
2310             }
2311         };
2312         for (input, ty) in decl.inputs.iter().zip(fty.inputs().skip_binder()) {
2313             check(&input, ty)
2314         }
2315         if let hir::FnRetTy::Return(ref ty) = decl.output {
2316             check(&ty, fty.output().skip_binder())
2317         }
2318     }
2319
2320     fty
2321 }
2322
2323 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2324     match tcx.hir().get_if_local(def_id) {
2325         Some(Node::ForeignItem(..)) => true,
2326         Some(_) => false,
2327         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2328     }
2329 }
2330
2331 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2332     match tcx.hir().get_if_local(def_id) {
2333         Some(
2334             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2335             | Node::ForeignItem(&hir::ForeignItem {
2336                 kind: hir::ForeignItemKind::Static(_, mutbl),
2337                 ..
2338             }),
2339         ) => Some(mutbl),
2340         Some(_) => None,
2341         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2342     }
2343 }
2344
2345 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2346     match tcx.hir().get_if_local(def_id) {
2347         Some(Node::Expr(&rustc_hir::Expr {
2348             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2349             ..
2350         })) => tcx.hir().body(body_id).generator_kind(),
2351         Some(_) => None,
2352         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2353     }
2354 }
2355
2356 fn from_target_feature(
2357     tcx: TyCtxt<'_>,
2358     id: DefId,
2359     attr: &ast::Attribute,
2360     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2361     target_features: &mut Vec<Symbol>,
2362 ) {
2363     let list = match attr.meta_item_list() {
2364         Some(list) => list,
2365         None => return,
2366     };
2367     let bad_item = |span| {
2368         let msg = "malformed `target_feature` attribute input";
2369         let code = "enable = \"..\"".to_owned();
2370         tcx.sess
2371             .struct_span_err(span, &msg)
2372             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2373             .emit();
2374     };
2375     let rust_features = tcx.features();
2376     for item in list {
2377         // Only `enable = ...` is accepted in the meta-item list.
2378         if !item.has_name(sym::enable) {
2379             bad_item(item.span());
2380             continue;
2381         }
2382
2383         // Must be of the form `enable = "..."` (a string).
2384         let value = match item.value_str() {
2385             Some(value) => value,
2386             None => {
2387                 bad_item(item.span());
2388                 continue;
2389             }
2390         };
2391
2392         // We allow comma separation to enable multiple features.
2393         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2394             let feature_gate = match supported_target_features.get(feature) {
2395                 Some(g) => g,
2396                 None => {
2397                     let msg =
2398                         format!("the feature named `{}` is not valid for this target", feature);
2399                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2400                     err.span_label(
2401                         item.span(),
2402                         format!("`{}` is not valid for this target", feature),
2403                     );
2404                     if let Some(stripped) = feature.strip_prefix('+') {
2405                         let valid = supported_target_features.contains_key(stripped);
2406                         if valid {
2407                             err.help("consider removing the leading `+` in the feature name");
2408                         }
2409                     }
2410                     err.emit();
2411                     return None;
2412                 }
2413             };
2414
2415             // Only allow features whose feature gates have been enabled.
2416             let allowed = match feature_gate.as_ref().copied() {
2417                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2418                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2419                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2420                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2421                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2422                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2423                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2424                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2425                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2426                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2427                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2428                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2429                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2430                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2431                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2432                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2433                 Some(name) => bug!("unknown target feature gate {}", name),
2434                 None => true,
2435             };
2436             if !allowed && id.is_local() {
2437                 feature_err(
2438                     &tcx.sess.parse_sess,
2439                     feature_gate.unwrap(),
2440                     item.span(),
2441                     &format!("the target feature `{}` is currently unstable", feature),
2442                 )
2443                 .emit();
2444             }
2445             Some(Symbol::intern(feature))
2446         }));
2447     }
2448 }
2449
2450 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2451     use rustc_middle::mir::mono::Linkage::*;
2452
2453     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2454     // applicable to variable declarations and may not really make sense for
2455     // Rust code in the first place but allow them anyway and trust that the
2456     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2457     // up in the future.
2458     //
2459     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2460     // and don't have to be, LLVM treats them as no-ops.
2461     match name {
2462         "appending" => Appending,
2463         "available_externally" => AvailableExternally,
2464         "common" => Common,
2465         "extern_weak" => ExternalWeak,
2466         "external" => External,
2467         "internal" => Internal,
2468         "linkonce" => LinkOnceAny,
2469         "linkonce_odr" => LinkOnceODR,
2470         "private" => Private,
2471         "weak" => WeakAny,
2472         "weak_odr" => WeakODR,
2473         _ => {
2474             let span = tcx.hir().span_if_local(def_id);
2475             if let Some(span) = span {
2476                 tcx.sess.span_fatal(span, "invalid linkage specified")
2477             } else {
2478                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2479             }
2480         }
2481     }
2482 }
2483
2484 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2485     let attrs = tcx.get_attrs(id);
2486
2487     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2488     if should_inherit_track_caller(tcx, id) {
2489         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2490     }
2491
2492     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2493
2494     let mut inline_span = None;
2495     let mut link_ordinal_span = None;
2496     let mut no_sanitize_span = None;
2497     for attr in attrs.iter() {
2498         if tcx.sess.check_name(attr, sym::cold) {
2499             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2500         } else if tcx.sess.check_name(attr, sym::rustc_allocator) {
2501             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2502         } else if tcx.sess.check_name(attr, sym::unwind) {
2503             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2504         } else if tcx.sess.check_name(attr, sym::ffi_returns_twice) {
2505             if tcx.is_foreign_item(id) {
2506                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2507             } else {
2508                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2509                 struct_span_err!(
2510                     tcx.sess,
2511                     attr.span,
2512                     E0724,
2513                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2514                 )
2515                 .emit();
2516             }
2517         } else if tcx.sess.check_name(attr, sym::ffi_pure) {
2518             if tcx.is_foreign_item(id) {
2519                 if attrs.iter().any(|a| tcx.sess.check_name(a, sym::ffi_const)) {
2520                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2521                     struct_span_err!(
2522                         tcx.sess,
2523                         attr.span,
2524                         E0757,
2525                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2526                     )
2527                     .emit();
2528                 } else {
2529                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2530                 }
2531             } else {
2532                 // `#[ffi_pure]` is only allowed on foreign functions
2533                 struct_span_err!(
2534                     tcx.sess,
2535                     attr.span,
2536                     E0755,
2537                     "`#[ffi_pure]` may only be used on foreign functions"
2538                 )
2539                 .emit();
2540             }
2541         } else if tcx.sess.check_name(attr, sym::ffi_const) {
2542             if tcx.is_foreign_item(id) {
2543                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2544             } else {
2545                 // `#[ffi_const]` is only allowed on foreign functions
2546                 struct_span_err!(
2547                     tcx.sess,
2548                     attr.span,
2549                     E0756,
2550                     "`#[ffi_const]` may only be used on foreign functions"
2551                 )
2552                 .emit();
2553             }
2554         } else if tcx.sess.check_name(attr, sym::rustc_allocator_nounwind) {
2555             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2556         } else if tcx.sess.check_name(attr, sym::naked) {
2557             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2558         } else if tcx.sess.check_name(attr, sym::no_mangle) {
2559             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2560         } else if tcx.sess.check_name(attr, sym::rustc_std_internal_symbol) {
2561             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2562         } else if tcx.sess.check_name(attr, sym::used) {
2563             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2564         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
2565             if tcx.fn_sig(id).abi() != abi::Abi::C {
2566                 struct_span_err!(
2567                     tcx.sess,
2568                     attr.span,
2569                     E0776,
2570                     "`#[cmse_nonsecure_entry]` requires C ABI"
2571                 )
2572                 .emit();
2573             }
2574             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2575                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2576                     .emit();
2577             }
2578             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2579         } else if tcx.sess.check_name(attr, sym::thread_local) {
2580             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2581         } else if tcx.sess.check_name(attr, sym::track_caller) {
2582             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2583                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2584                     .emit();
2585             }
2586             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2587         } else if tcx.sess.check_name(attr, sym::export_name) {
2588             if let Some(s) = attr.value_str() {
2589                 if s.as_str().contains('\0') {
2590                     // `#[export_name = ...]` will be converted to a null-terminated string,
2591                     // so it may not contain any null characters.
2592                     struct_span_err!(
2593                         tcx.sess,
2594                         attr.span,
2595                         E0648,
2596                         "`export_name` may not contain null characters"
2597                     )
2598                     .emit();
2599                 }
2600                 codegen_fn_attrs.export_name = Some(s);
2601             }
2602         } else if tcx.sess.check_name(attr, sym::target_feature) {
2603             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2604                 if !tcx.features().target_feature_11 {
2605                     let mut err = feature_err(
2606                         &tcx.sess.parse_sess,
2607                         sym::target_feature_11,
2608                         attr.span,
2609                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2610                     );
2611                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2612                     err.emit();
2613                 } else if let Some(local_id) = id.as_local() {
2614                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2615                 }
2616             }
2617             from_target_feature(
2618                 tcx,
2619                 id,
2620                 attr,
2621                 &supported_target_features,
2622                 &mut codegen_fn_attrs.target_features,
2623             );
2624         } else if tcx.sess.check_name(attr, sym::linkage) {
2625             if let Some(val) = attr.value_str() {
2626                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2627             }
2628         } else if tcx.sess.check_name(attr, sym::link_section) {
2629             if let Some(val) = attr.value_str() {
2630                 if val.as_str().bytes().any(|b| b == 0) {
2631                     let msg = format!(
2632                         "illegal null byte in link_section \
2633                          value: `{}`",
2634                         &val
2635                     );
2636                     tcx.sess.span_err(attr.span, &msg);
2637                 } else {
2638                     codegen_fn_attrs.link_section = Some(val);
2639                 }
2640             }
2641         } else if tcx.sess.check_name(attr, sym::link_name) {
2642             codegen_fn_attrs.link_name = attr.value_str();
2643         } else if tcx.sess.check_name(attr, sym::link_ordinal) {
2644             link_ordinal_span = Some(attr.span);
2645             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2646                 codegen_fn_attrs.link_ordinal = ordinal;
2647             }
2648         } else if tcx.sess.check_name(attr, sym::no_sanitize) {
2649             no_sanitize_span = Some(attr.span);
2650             if let Some(list) = attr.meta_item_list() {
2651                 for item in list.iter() {
2652                     if item.has_name(sym::address) {
2653                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2654                     } else if item.has_name(sym::memory) {
2655                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2656                     } else if item.has_name(sym::thread) {
2657                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2658                     } else {
2659                         tcx.sess
2660                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2661                             .note("expected one of: `address`, `memory` or `thread`")
2662                             .emit();
2663                     }
2664                 }
2665             }
2666         } else if tcx.sess.check_name(attr, sym::instruction_set) {
2667             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2668                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2669                     [NestedMetaItem::MetaItem(set)] => {
2670                         let segments =
2671                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2672                         match segments.as_slice() {
2673                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2674                                 if !tcx.sess.target.has_thumb_interworking {
2675                                     struct_span_err!(
2676                                         tcx.sess.diagnostic(),
2677                                         attr.span,
2678                                         E0779,
2679                                         "target does not support `#[instruction_set]`"
2680                                     )
2681                                     .emit();
2682                                     None
2683                                 } else if segments[1] == sym::a32 {
2684                                     Some(InstructionSetAttr::ArmA32)
2685                                 } else if segments[1] == sym::t32 {
2686                                     Some(InstructionSetAttr::ArmT32)
2687                                 } else {
2688                                     unreachable!()
2689                                 }
2690                             }
2691                             _ => {
2692                                 struct_span_err!(
2693                                     tcx.sess.diagnostic(),
2694                                     attr.span,
2695                                     E0779,
2696                                     "invalid instruction set specified",
2697                                 )
2698                                 .emit();
2699                                 None
2700                             }
2701                         }
2702                     }
2703                     [] => {
2704                         struct_span_err!(
2705                             tcx.sess.diagnostic(),
2706                             attr.span,
2707                             E0778,
2708                             "`#[instruction_set]` requires an argument"
2709                         )
2710                         .emit();
2711                         None
2712                     }
2713                     _ => {
2714                         struct_span_err!(
2715                             tcx.sess.diagnostic(),
2716                             attr.span,
2717                             E0779,
2718                             "cannot specify more than one instruction set"
2719                         )
2720                         .emit();
2721                         None
2722                     }
2723                 },
2724                 _ => {
2725                     struct_span_err!(
2726                         tcx.sess.diagnostic(),
2727                         attr.span,
2728                         E0778,
2729                         "must specify an instruction set"
2730                     )
2731                     .emit();
2732                     None
2733                 }
2734             };
2735         }
2736     }
2737
2738     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2739         if !attr.has_name(sym::inline) {
2740             return ia;
2741         }
2742         match attr.meta().map(|i| i.kind) {
2743             Some(MetaItemKind::Word) => {
2744                 tcx.sess.mark_attr_used(attr);
2745                 InlineAttr::Hint
2746             }
2747             Some(MetaItemKind::List(ref items)) => {
2748                 tcx.sess.mark_attr_used(attr);
2749                 inline_span = Some(attr.span);
2750                 if items.len() != 1 {
2751                     struct_span_err!(
2752                         tcx.sess.diagnostic(),
2753                         attr.span,
2754                         E0534,
2755                         "expected one argument"
2756                     )
2757                     .emit();
2758                     InlineAttr::None
2759                 } else if list_contains_name(&items[..], sym::always) {
2760                     InlineAttr::Always
2761                 } else if list_contains_name(&items[..], sym::never) {
2762                     InlineAttr::Never
2763                 } else {
2764                     struct_span_err!(
2765                         tcx.sess.diagnostic(),
2766                         items[0].span(),
2767                         E0535,
2768                         "invalid argument"
2769                     )
2770                     .emit();
2771
2772                     InlineAttr::None
2773                 }
2774             }
2775             Some(MetaItemKind::NameValue(_)) => ia,
2776             None => ia,
2777         }
2778     });
2779
2780     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2781         if !attr.has_name(sym::optimize) {
2782             return ia;
2783         }
2784         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2785         match attr.meta().map(|i| i.kind) {
2786             Some(MetaItemKind::Word) => {
2787                 err(attr.span, "expected one argument");
2788                 ia
2789             }
2790             Some(MetaItemKind::List(ref items)) => {
2791                 tcx.sess.mark_attr_used(attr);
2792                 inline_span = Some(attr.span);
2793                 if items.len() != 1 {
2794                     err(attr.span, "expected one argument");
2795                     OptimizeAttr::None
2796                 } else if list_contains_name(&items[..], sym::size) {
2797                     OptimizeAttr::Size
2798                 } else if list_contains_name(&items[..], sym::speed) {
2799                     OptimizeAttr::Speed
2800                 } else {
2801                     err(items[0].span(), "invalid argument");
2802                     OptimizeAttr::None
2803                 }
2804             }
2805             Some(MetaItemKind::NameValue(_)) => ia,
2806             None => ia,
2807         }
2808     });
2809
2810     // #73631: closures inherit `#[target_feature]` annotations
2811     if tcx.features().target_feature_11 && tcx.is_closure(id) {
2812         let owner_id = tcx.parent(id).expect("closure should have a parent");
2813         codegen_fn_attrs
2814             .target_features
2815             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
2816     }
2817
2818     // If a function uses #[target_feature] it can't be inlined into general
2819     // purpose functions as they wouldn't have the right target features
2820     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2821     // respected.
2822     if !codegen_fn_attrs.target_features.is_empty() {
2823         if codegen_fn_attrs.inline == InlineAttr::Always {
2824             if let Some(span) = inline_span {
2825                 tcx.sess.span_err(
2826                     span,
2827                     "cannot use `#[inline(always)]` with \
2828                      `#[target_feature]`",
2829                 );
2830             }
2831         }
2832     }
2833
2834     if !codegen_fn_attrs.no_sanitize.is_empty() {
2835         if codegen_fn_attrs.inline == InlineAttr::Always {
2836             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2837                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
2838                 tcx.struct_span_lint_hir(
2839                     lint::builtin::INLINE_NO_SANITIZE,
2840                     hir_id,
2841                     no_sanitize_span,
2842                     |lint| {
2843                         lint.build("`no_sanitize` will have no effect after inlining")
2844                             .span_note(inline_span, "inlining requested here")
2845                             .emit();
2846                     },
2847                 )
2848             }
2849         }
2850     }
2851
2852     // Weak lang items have the same semantics as "std internal" symbols in the
2853     // sense that they're preserved through all our LTO passes and only
2854     // strippable by the linker.
2855     //
2856     // Additionally weak lang items have predetermined symbol names.
2857     if tcx.is_weak_lang_item(id) {
2858         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2859     }
2860     let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
2861     if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
2862         codegen_fn_attrs.export_name = Some(name);
2863         codegen_fn_attrs.link_name = Some(name);
2864     }
2865     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2866
2867     // Internal symbols to the standard library all have no_mangle semantics in
2868     // that they have defined symbol names present in the function name. This
2869     // also applies to weak symbols where they all have known symbol names.
2870     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2871         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2872     }
2873
2874     codegen_fn_attrs
2875 }
2876
2877 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
2878 /// applied to the method prototype.
2879 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2880     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
2881         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
2882             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
2883                 if let Some(trait_item) = tcx
2884                     .associated_items(trait_def_id)
2885                     .filter_by_name_unhygienic(impl_item.ident.name)
2886                     .find(move |trait_item| {
2887                         trait_item.kind == ty::AssocKind::Fn
2888                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
2889                     })
2890                 {
2891                     return tcx
2892                         .codegen_fn_attrs(trait_item.def_id)
2893                         .flags
2894                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
2895                 }
2896             }
2897         }
2898     }
2899
2900     false
2901 }
2902
2903 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2904     use rustc_ast::{Lit, LitIntType, LitKind};
2905     let meta_item_list = attr.meta_item_list();
2906     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2907     let sole_meta_list = match meta_item_list {
2908         Some([item]) => item.literal(),
2909         _ => None,
2910     };
2911     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2912         if *ordinal <= usize::MAX as u128 {
2913             Some(*ordinal as usize)
2914         } else {
2915             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2916             tcx.sess
2917                 .struct_span_err(attr.span, &msg)
2918                 .note("the value may not exceed `usize::MAX`")
2919                 .emit();
2920             None
2921         }
2922     } else {
2923         tcx.sess
2924             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2925             .note("an unsuffixed integer value, e.g., `1`, is expected")
2926             .emit();
2927         None
2928     }
2929 }
2930
2931 fn check_link_name_xor_ordinal(
2932     tcx: TyCtxt<'_>,
2933     codegen_fn_attrs: &CodegenFnAttrs,
2934     inline_span: Option<Span>,
2935 ) {
2936     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2937         return;
2938     }
2939     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2940     if let Some(span) = inline_span {
2941         tcx.sess.span_err(span, msg);
2942     } else {
2943         tcx.sess.err(msg);
2944     }
2945 }
2946
2947 /// Checks the function annotated with `#[target_feature]` is not a safe
2948 /// trait method implementation, reporting an error if it is.
2949 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
2950     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
2951     let node = tcx.hir().get(hir_id);
2952     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
2953         let parent_id = tcx.hir().get_parent_item(hir_id);
2954         let parent_item = tcx.hir().expect_item(parent_id);
2955         if let hir::ItemKind::Impl { of_trait: Some(_), .. } = parent_item.kind {
2956             tcx.sess
2957                 .struct_span_err(
2958                     attr_span,
2959                     "`#[target_feature(..)]` cannot be applied to safe trait method",
2960                 )
2961                 .span_label(attr_span, "cannot be applied to safe trait method")
2962                 .span_label(tcx.def_span(id), "not an `unsafe` function")
2963                 .emit();
2964         }
2965     }
2966 }