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;
  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::Attribute;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  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, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         default_anon_const_substs: type_of::default_anon_const_substs,
  72         type_of: type_of::type_of,
  73         item_bounds: item_bounds::item_bounds,
  74         explicit_item_bounds: item_bounds::explicit_item_bounds,
  75         generics_of,
  76         predicates_of,
  77         predicates_defined_on,
  78         explicit_predicates_of,
  79         super_predicates_of,
  80         super_predicates_that_define_assoc_type,
  81         trait_explicit_predicates_and_bounds,
  82         type_param_predicates,
  83         trait_def,
  84         adt_def,
  85         fn_sig,
  86         impl_trait_ref,
  87         impl_polarity,
  88         is_foreign_item,
  89         static_mutability,
  90         generator_kind,
  91         codegen_fn_attrs,
  92         collect_mod_item_types,
  93         should_inherit_track_caller,
  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     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 132         match generic_arg {
 133             hir::GenericArg::Infer(inf) => {
 134                 self.0.push(inf.span);
 135                 intravisit::walk_inf(self, inf);
 136             }
 137             hir::GenericArg::Type(t) => self.visit_ty(t),
 138             _ => {}
 139         }
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty {
 193             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 194                 is_fn = true;
 195
 196                 // Check if parent is const or static
 197                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 198                 let parent_node = tcx.hir().get(parent_id);
 199
 200                 is_const_or_static = matches!(
 201                     parent_node,
 202                     Node::Item(&hir::Item {
 203                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 204                         ..
 205                     }) | Node::TraitItem(&hir::TraitItem {
 206                         kind: hir::TraitItemKind::Const(..),
 207                         ..
 208                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 209                 );
 210             }
 211         }
 212
 213         // if function is wrapped around a const or static,
 214         // then don't show the suggestion
 215         if !(is_fn && is_const_or_static) {
 216             err.multipart_suggestion(
 217                 "use type parameters instead",
 218                 sugg,
 219                 Applicability::HasPlaceholders,
 220             );
 221         }
 222     }
 223     err.emit();
 224 }
 225
 226 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 227     let (generics, suggest) = match &item.kind {
 228         hir::ItemKind::Union(_, generics)
 229         | hir::ItemKind::Enum(_, generics)
 230         | hir::ItemKind::TraitAlias(generics, _)
 231         | hir::ItemKind::Trait(_, _, generics, ..)
 232         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 233         | hir::ItemKind::Struct(_, generics) => (generics, true),
 234         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 235         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 236         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 237         _ => return,
 238     };
 239
 240     let mut visitor = PlaceholderHirTyCollector::default();
 241     visitor.visit_item(item);
 242
 243     placeholder_type_error(
 244         tcx,
 245         Some(generics.span),
 246         generics.params,
 247         visitor.0,
 248         suggest,
 249         None,
 250         item.kind.descr(),
 251     );
 252 }
 253
 254 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 255     type Map = Map<'tcx>;
 256
 257     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 258         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 259     }
 260
 261     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 262         convert_item(self.tcx, item.item_id());
 263         reject_placeholder_type_signatures_in_item(self.tcx, item);
 264         intravisit::walk_item(self, item);
 265     }
 266
 267     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 268         for param in generics.params {
 269             match param.kind {
 270                 hir::GenericParamKind::Lifetime { .. } => {}
 271                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 272                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 273                     self.tcx.ensure().type_of(def_id);
 274                 }
 275                 hir::GenericParamKind::Type { .. } => {}
 276                 hir::GenericParamKind::Const { default, .. } => {
 277                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 278                     self.tcx.ensure().type_of(def_id);
 279                     if let Some(default) = default {
 280                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 281                         // need to store default and type of default
 282                         self.tcx.ensure().type_of(default_def_id);
 283                         self.tcx.ensure().const_param_default(def_id);
 284                     }
 285                 }
 286             }
 287         }
 288         intravisit::walk_generics(self, generics);
 289     }
 290
 291     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 292         if let hir::ExprKind::Closure(..) = expr.kind {
 293             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 294             self.tcx.ensure().generics_of(def_id);
 295             self.tcx.ensure().type_of(def_id);
 296         }
 297         intravisit::walk_expr(self, expr);
 298     }
 299
 300     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 301         convert_trait_item(self.tcx, trait_item.trait_item_id());
 302         intravisit::walk_trait_item(self, trait_item);
 303     }
 304
 305     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 306         convert_impl_item(self.tcx, impl_item.impl_item_id());
 307         intravisit::walk_impl_item(self, impl_item);
 308     }
 309 }
 310
 311 ///////////////////////////////////////////////////////////////////////////
 312 // Utility types and common code for the above passes.
 313
 314 fn bad_placeholder_type(
 315     tcx: TyCtxt<'tcx>,
 316     mut spans: Vec<Span>,
 317     kind: &'static str,
 318 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 319     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 320
 321     spans.sort();
 322     let mut err = struct_span_err!(
 323         tcx.sess,
 324         spans.clone(),
 325         E0121,
 326         "the type placeholder `_` is not allowed within types on item signatures for {}",
 327         kind
 328     );
 329     for span in spans {
 330         err.span_label(span, "not allowed in type signatures");
 331     }
 332     err
 333 }
 334
 335 impl ItemCtxt<'tcx> {
 336     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 337         ItemCtxt { tcx, item_def_id }
 338     }
 339
 340     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 341         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 342     }
 343
 344     pub fn hir_id(&self) -> hir::HirId {
 345         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 346     }
 347
 348     pub fn node(&self) -> hir::Node<'tcx> {
 349         self.tcx.hir().get(self.hir_id())
 350     }
 351 }
 352
 353 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 354     fn tcx(&self) -> TyCtxt<'tcx> {
 355         self.tcx
 356     }
 357
 358     fn item_def_id(&self) -> Option<DefId> {
 359         Some(self.item_def_id)
 360     }
 361
 362     fn get_type_parameter_bounds(
 363         &self,
 364         span: Span,
 365         def_id: DefId,
 366         assoc_name: Ident,
 367     ) -> ty::GenericPredicates<'tcx> {
 368         self.tcx.at(span).type_param_predicates((
 369             self.item_def_id,
 370             def_id.expect_local(),
 371             assoc_name,
 372         ))
 373     }
 374
 375     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 376         None
 377     }
 378
 379     fn allow_ty_infer(&self) -> bool {
 380         false
 381     }
 382
 383     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 384         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 385     }
 386
 387     fn ct_infer(
 388         &self,
 389         ty: Ty<'tcx>,
 390         _: Option<&ty::GenericParamDef>,
 391         span: Span,
 392     ) -> &'tcx Const<'tcx> {
 393         bad_placeholder_type(self.tcx(), vec![span], "generic").emit();
 394         // Typeck doesn't expect erased regions to be returned from `type_of`.
 395         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 396             ty::ReErased => self.tcx.lifetimes.re_static,
 397             _ => r,
 398         });
 399         self.tcx().const_error(ty)
 400     }
 401
 402     fn projected_ty_from_poly_trait_ref(
 403         &self,
 404         span: Span,
 405         item_def_id: DefId,
 406         item_segment: &hir::PathSegment<'_>,
 407         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 408     ) -> Ty<'tcx> {
 409         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 410             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 411                 self,
 412                 self.tcx,
 413                 span,
 414                 item_def_id,
 415                 item_segment,
 416                 trait_ref.substs,
 417             );
 418             self.tcx().mk_projection(item_def_id, item_substs)
 419         } else {
 420             // There are no late-bound regions; we can just ignore the binder.
 421             let mut err = struct_span_err!(
 422                 self.tcx().sess,
 423                 span,
 424                 E0212,
 425                 "cannot use the associated type of a trait \
 426                  with uninferred generic parameters"
 427             );
 428
 429             match self.node() {
 430                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 431                     let item =
 432                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_did(self.hir_id()));
 433                     match &item.kind {
 434                         hir::ItemKind::Enum(_, generics)
 435                         | hir::ItemKind::Struct(_, generics)
 436                         | hir::ItemKind::Union(_, generics) => {
 437                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 438                             let (lt_sp, sugg) = match generics.params {
 439                                 [] => (generics.span, format!("<{}>", lt_name)),
 440                                 [bound, ..] => {
 441                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 442                                 }
 443                             };
 444                             let suggestions = vec![
 445                                 (lt_sp, sugg),
 446                                 (
 447                                     span.with_hi(item_segment.ident.span.lo()),
 448                                     format!(
 449                                         "{}::",
 450                                         // Replace the existing lifetimes with a new named lifetime.
 451                                         self.tcx
 452                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 453                                                 self.tcx.mk_region(ty::ReEarlyBound(
 454                                                     ty::EarlyBoundRegion {
 455                                                         def_id: item_def_id,
 456                                                         index: 0,
 457                                                         name: Symbol::intern(&lt_name),
 458                                                     },
 459                                                 ))
 460                                             })
 461                                             .0,
 462                                     ),
 463                                 ),
 464                             ];
 465                             err.multipart_suggestion(
 466                                 "use a fully qualified path with explicit lifetimes",
 467                                 suggestions,
 468                                 Applicability::MaybeIncorrect,
 469                             );
 470                         }
 471                         _ => {}
 472                     }
 473                 }
 474                 hir::Node::Item(hir::Item {
 475                     kind:
 476                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 477                     ..
 478                 }) => {}
 479                 hir::Node::Item(_)
 480                 | hir::Node::ForeignItem(_)
 481                 | hir::Node::TraitItem(_)
 482                 | hir::Node::ImplItem(_) => {
 483                     err.span_suggestion_verbose(
 484                         span.with_hi(item_segment.ident.span.lo()),
 485                         "use a fully qualified path with inferred lifetimes",
 486                         format!(
 487                             "{}::",
 488                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 489                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 490                         ),
 491                         Applicability::MaybeIncorrect,
 492                     );
 493                 }
 494                 _ => {}
 495             }
 496             err.emit();
 497             self.tcx().ty_error()
 498         }
 499     }
 500
 501     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 502         // Types in item signatures are not normalized to avoid undue dependencies.
 503         ty
 504     }
 505
 506     fn set_tainted_by_errors(&self) {
 507         // There's no obvious place to track this, so just let it go.
 508     }
 509
 510     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 511         // There's no place to record types from signatures?
 512     }
 513 }
 514
 515 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 516 fn get_new_lifetime_name<'tcx>(
 517     tcx: TyCtxt<'tcx>,
 518     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 519     generics: &hir::Generics<'tcx>,
 520 ) -> String {
 521     let existing_lifetimes = tcx
 522         .collect_referenced_late_bound_regions(&poly_trait_ref)
 523         .into_iter()
 524         .filter_map(|lt| {
 525             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 526                 Some(name.as_str().to_string())
 527             } else {
 528                 None
 529             }
 530         })
 531         .chain(generics.params.iter().filter_map(|param| {
 532             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 533                 Some(param.name.ident().as_str().to_string())
 534             } else {
 535                 None
 536             }
 537         }))
 538         .collect::<FxHashSet<String>>();
 539
 540     let a_to_z_repeat_n = |n| {
 541         (b'a'..=b'z').map(move |c| {
 542             let mut s = '\''.to_string();
 543             s.extend(std::iter::repeat(char::from(c)).take(n));
 544             s
 545         })
 546     };
 547
 548     // If all single char lifetime names are present, we wrap around and double the chars.
 549     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 550 }
 551
 552 /// Returns the predicates defined on `item_def_id` of the form
 553 /// `X: Foo` where `X` is the type parameter `def_id`.
 554 fn type_param_predicates(
 555     tcx: TyCtxt<'_>,
 556     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 557 ) -> ty::GenericPredicates<'_> {
 558     use rustc_hir::*;
 559
 560     // In the AST, bounds can derive from two places. Either
 561     // written inline like `<T: Foo>` or in a where-clause like
 562     // `where T: Foo`.
 563
 564     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 565     let param_owner = tcx.hir().ty_param_owner(param_id);
 566     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 567     let generics = tcx.generics_of(param_owner_def_id);
 568     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 569     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 570
 571     // Don't look for bounds where the type parameter isn't in scope.
 572     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 573         None
 574     } else {
 575         tcx.generics_of(item_def_id).parent
 576     };
 577
 578     let mut result = parent
 579         .map(|parent| {
 580             let icx = ItemCtxt::new(tcx, parent);
 581             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 582         })
 583         .unwrap_or_default();
 584     let mut extend = None;
 585
 586     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 587     let ast_generics = match tcx.hir().get(item_hir_id) {
 588         Node::TraitItem(item) => &item.generics,
 589
 590         Node::ImplItem(item) => &item.generics,
 591
 592         Node::Item(item) => {
 593             match item.kind {
 594                 ItemKind::Fn(.., ref generics, _)
 595                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 596                 | ItemKind::TyAlias(_, ref generics)
 597                 | ItemKind::OpaqueTy(OpaqueTy {
 598                     ref generics,
 599                     origin: hir::OpaqueTyOrigin::TyAlias,
 600                     ..
 601                 })
 602                 | ItemKind::Enum(_, ref generics)
 603                 | ItemKind::Struct(_, ref generics)
 604                 | ItemKind::Union(_, ref generics) => generics,
 605                 ItemKind::Trait(_, _, ref generics, ..) => {
 606                     // Implied `Self: Trait` and supertrait bounds.
 607                     if param_id == item_hir_id {
 608                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 609                         extend =
 610                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 611                     }
 612                     generics
 613                 }
 614                 _ => return result,
 615             }
 616         }
 617
 618         Node::ForeignItem(item) => match item.kind {
 619             ForeignItemKind::Fn(_, _, ref generics) => generics,
 620             _ => return result,
 621         },
 622
 623         _ => return result,
 624     };
 625
 626     let icx = ItemCtxt::new(tcx, item_def_id);
 627     let extra_predicates = extend.into_iter().chain(
 628         icx.type_parameter_bounds_in_generics(
 629             ast_generics,
 630             param_id,
 631             ty,
 632             OnlySelfBounds(true),
 633             Some(assoc_name),
 634         )
 635         .into_iter()
 636         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 637             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 638             _ => false,
 639         }),
 640     );
 641     result.predicates =
 642         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 643     result
 644 }
 645
 646 impl ItemCtxt<'tcx> {
 647     /// Finds bounds from `hir::Generics`. This requires scanning through the
 648     /// AST. We do this to avoid having to convert *all* the bounds, which
 649     /// would create artificial cycles. Instead, we can only convert the
 650     /// bounds for a type parameter `X` if `X::Foo` is used.
 651     fn type_parameter_bounds_in_generics(
 652         &self,
 653         ast_generics: &'tcx hir::Generics<'tcx>,
 654         param_id: hir::HirId,
 655         ty: Ty<'tcx>,
 656         only_self_bounds: OnlySelfBounds,
 657         assoc_name: Option<Ident>,
 658     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 659         let from_ty_params = ast_generics
 660             .params
 661             .iter()
 662             .filter_map(|param| match param.kind {
 663                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 664                 _ => None,
 665             })
 666             .flat_map(|bounds| bounds.iter())
 667             .filter(|b| match assoc_name {
 668                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 669                 None => true,
 670             })
 671             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 672
 673         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 674         let from_where_clauses = ast_generics
 675             .where_clause
 676             .predicates
 677             .iter()
 678             .filter_map(|wp| match *wp {
 679                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 680                 _ => None,
 681             })
 682             .flat_map(|bp| {
 683                 let bt = if bp.is_param_bound(param_def_id) {
 684                     Some(ty)
 685                 } else if !only_self_bounds.0 {
 686                     Some(self.to_ty(bp.bounded_ty))
 687                 } else {
 688                     None
 689                 };
 690                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 691
 692                 bp.bounds
 693                     .iter()
 694                     .filter(|b| match assoc_name {
 695                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 696                         None => true,
 697                     })
 698                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 699             })
 700             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 701
 702         from_ty_params.chain(from_where_clauses).collect()
 703     }
 704
 705     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 706         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 707
 708         match b {
 709             hir::GenericBound::Trait(poly_trait_ref, _) => {
 710                 let trait_ref = &poly_trait_ref.trait_ref;
 711                 if let Some(trait_did) = trait_ref.trait_def_id() {
 712                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 713                 } else {
 714                     false
 715                 }
 716             }
 717             _ => false,
 718         }
 719     }
 720 }
 721
 722 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 723     let it = tcx.hir().item(item_id);
 724     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 725     let def_id = item_id.def_id;
 726
 727     match it.kind {
 728         // These don't define types.
 729         hir::ItemKind::ExternCrate(_)
 730         | hir::ItemKind::Use(..)
 731         | hir::ItemKind::Macro(_)
 732         | hir::ItemKind::Mod(_)
 733         | hir::ItemKind::GlobalAsm(_) => {}
 734         hir::ItemKind::ForeignMod { items, .. } => {
 735             for item in items {
 736                 let item = tcx.hir().foreign_item(item.id);
 737                 tcx.ensure().generics_of(item.def_id);
 738                 tcx.ensure().type_of(item.def_id);
 739                 tcx.ensure().predicates_of(item.def_id);
 740                 match item.kind {
 741                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 742                     hir::ForeignItemKind::Static(..) => {
 743                         let mut visitor = PlaceholderHirTyCollector::default();
 744                         visitor.visit_foreign_item(item);
 745                         placeholder_type_error(
 746                             tcx,
 747                             None,
 748                             &[],
 749                             visitor.0,
 750                             false,
 751                             None,
 752                             "static variable",
 753                         );
 754                     }
 755                     _ => (),
 756                 }
 757             }
 758         }
 759         hir::ItemKind::Enum(ref enum_definition, _) => {
 760             tcx.ensure().generics_of(def_id);
 761             tcx.ensure().type_of(def_id);
 762             tcx.ensure().predicates_of(def_id);
 763             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 764         }
 765         hir::ItemKind::Impl { .. } => {
 766             tcx.ensure().generics_of(def_id);
 767             tcx.ensure().type_of(def_id);
 768             tcx.ensure().impl_trait_ref(def_id);
 769             tcx.ensure().predicates_of(def_id);
 770         }
 771         hir::ItemKind::Trait(..) => {
 772             tcx.ensure().generics_of(def_id);
 773             tcx.ensure().trait_def(def_id);
 774             tcx.at(it.span).super_predicates_of(def_id);
 775             tcx.ensure().predicates_of(def_id);
 776         }
 777         hir::ItemKind::TraitAlias(..) => {
 778             tcx.ensure().generics_of(def_id);
 779             tcx.at(it.span).super_predicates_of(def_id);
 780             tcx.ensure().predicates_of(def_id);
 781         }
 782         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.ensure().type_of(def_id);
 785             tcx.ensure().predicates_of(def_id);
 786
 787             for f in struct_def.fields() {
 788                 let def_id = tcx.hir().local_def_id(f.hir_id);
 789                 tcx.ensure().generics_of(def_id);
 790                 tcx.ensure().type_of(def_id);
 791                 tcx.ensure().predicates_of(def_id);
 792             }
 793
 794             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 795                 convert_variant_ctor(tcx, ctor_hir_id);
 796             }
 797         }
 798
 799         // Desugared from `impl Trait`, so visited by the function's return type.
 800         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 801             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 802             ..
 803         }) => {}
 804
 805         // Don't call `type_of` on opaque types, since that depends on type
 806         // checking function bodies. `check_item_type` ensures that it's called
 807         // instead.
 808         hir::ItemKind::OpaqueTy(..) => {
 809             tcx.ensure().generics_of(def_id);
 810             tcx.ensure().predicates_of(def_id);
 811             tcx.ensure().explicit_item_bounds(def_id);
 812         }
 813         hir::ItemKind::TyAlias(..)
 814         | hir::ItemKind::Static(..)
 815         | hir::ItemKind::Const(..)
 816         | hir::ItemKind::Fn(..) => {
 817             tcx.ensure().generics_of(def_id);
 818             tcx.ensure().type_of(def_id);
 819             tcx.ensure().predicates_of(def_id);
 820             match it.kind {
 821                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 822                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 823                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 824                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 825                     if let hir::TyKind::TraitObject(..) = ty.kind {
 826                         let mut visitor = PlaceholderHirTyCollector::default();
 827                         visitor.visit_item(it);
 828                         placeholder_type_error(
 829                             tcx,
 830                             None,
 831                             &[],
 832                             visitor.0,
 833                             false,
 834                             None,
 835                             it.kind.descr(),
 836                         );
 837                     }
 838                 }
 839                 _ => (),
 840             }
 841         }
 842     }
 843 }
 844
 845 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 846     let trait_item = tcx.hir().trait_item(trait_item_id);
 847     tcx.ensure().generics_of(trait_item_id.def_id);
 848
 849     match trait_item.kind {
 850         hir::TraitItemKind::Fn(..) => {
 851             tcx.ensure().type_of(trait_item_id.def_id);
 852             tcx.ensure().fn_sig(trait_item_id.def_id);
 853         }
 854
 855         hir::TraitItemKind::Const(.., Some(_)) => {
 856             tcx.ensure().type_of(trait_item_id.def_id);
 857         }
 858
 859         hir::TraitItemKind::Const(..) => {
 860             tcx.ensure().type_of(trait_item_id.def_id);
 861             // Account for `const C: _;`.
 862             let mut visitor = PlaceholderHirTyCollector::default();
 863             visitor.visit_trait_item(trait_item);
 864             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 865         }
 866
 867         hir::TraitItemKind::Type(_, Some(_)) => {
 868             tcx.ensure().item_bounds(trait_item_id.def_id);
 869             tcx.ensure().type_of(trait_item_id.def_id);
 870             // Account for `type T = _;`.
 871             let mut visitor = PlaceholderHirTyCollector::default();
 872             visitor.visit_trait_item(trait_item);
 873             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 874         }
 875
 876         hir::TraitItemKind::Type(_, None) => {
 877             tcx.ensure().item_bounds(trait_item_id.def_id);
 878             // #74612: Visit and try to find bad placeholders
 879             // even if there is no concrete type.
 880             let mut visitor = PlaceholderHirTyCollector::default();
 881             visitor.visit_trait_item(trait_item);
 882
 883             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 884         }
 885     };
 886
 887     tcx.ensure().predicates_of(trait_item_id.def_id);
 888 }
 889
 890 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 891     let def_id = impl_item_id.def_id;
 892     tcx.ensure().generics_of(def_id);
 893     tcx.ensure().type_of(def_id);
 894     tcx.ensure().predicates_of(def_id);
 895     let impl_item = tcx.hir().impl_item(impl_item_id);
 896     match impl_item.kind {
 897         hir::ImplItemKind::Fn(..) => {
 898             tcx.ensure().fn_sig(def_id);
 899         }
 900         hir::ImplItemKind::TyAlias(_) => {
 901             // Account for `type T = _;`
 902             let mut visitor = PlaceholderHirTyCollector::default();
 903             visitor.visit_impl_item(impl_item);
 904
 905             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 906         }
 907         hir::ImplItemKind::Const(..) => {}
 908     }
 909 }
 910
 911 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 912     let def_id = tcx.hir().local_def_id(ctor_id);
 913     tcx.ensure().generics_of(def_id);
 914     tcx.ensure().type_of(def_id);
 915     tcx.ensure().predicates_of(def_id);
 916 }
 917
 918 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 919     let def = tcx.adt_def(def_id);
 920     let repr_type = def.repr.discr_type();
 921     let initial = repr_type.initial_discriminant(tcx);
 922     let mut prev_discr = None::<Discr<'_>>;
 923
 924     // fill the discriminant values and field types
 925     for variant in variants {
 926         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 927         prev_discr = Some(
 928             if let Some(ref e) = variant.disr_expr {
 929                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 930                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 931             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 932                 Some(discr)
 933             } else {
 934                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 935                     .span_label(
 936                         variant.span,
 937                         format!("overflowed on value after {}", prev_discr.unwrap()),
 938                     )
 939                     .note(&format!(
 940                         "explicitly set `{} = {}` if that is desired outcome",
 941                         variant.ident, wrapped_discr
 942                     ))
 943                     .emit();
 944                 None
 945             }
 946             .unwrap_or(wrapped_discr),
 947         );
 948
 949         for f in variant.data.fields() {
 950             let def_id = tcx.hir().local_def_id(f.hir_id);
 951             tcx.ensure().generics_of(def_id);
 952             tcx.ensure().type_of(def_id);
 953             tcx.ensure().predicates_of(def_id);
 954         }
 955
 956         // Convert the ctor, if any. This also registers the variant as
 957         // an item.
 958         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 959             convert_variant_ctor(tcx, ctor_hir_id);
 960         }
 961     }
 962 }
 963
 964 fn convert_variant(
 965     tcx: TyCtxt<'_>,
 966     variant_did: Option<LocalDefId>,
 967     ctor_did: Option<LocalDefId>,
 968     ident: Ident,
 969     discr: ty::VariantDiscr,
 970     def: &hir::VariantData<'_>,
 971     adt_kind: ty::AdtKind,
 972     parent_did: LocalDefId,
 973 ) -> ty::VariantDef {
 974     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 975     let fields = def
 976         .fields()
 977         .iter()
 978         .map(|f| {
 979             let fid = tcx.hir().local_def_id(f.hir_id);
 980             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 981             if let Some(prev_span) = dup_span {
 982                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 983                     field_name: f.ident,
 984                     span: f.span,
 985                     prev_span,
 986                 });
 987             } else {
 988                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 989             }
 990
 991             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 992         })
 993         .collect();
 994     let recovered = match def {
 995         hir::VariantData::Struct(_, r) => *r,
 996         _ => false,
 997     };
 998     ty::VariantDef::new(
 999         ident,
1000         variant_did.map(LocalDefId::to_def_id),
1001         ctor_did.map(LocalDefId::to_def_id),
1002         discr,
1003         fields,
1004         CtorKind::from_hir(def),
1005         adt_kind,
1006         parent_did.to_def_id(),
1007         recovered,
1008         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1009             || variant_did.map_or(false, |variant_did| {
1010                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1011             }),
1012     )
1013 }
1014
1015 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1016     use rustc_hir::*;
1017
1018     let def_id = def_id.expect_local();
1019     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1020     let item = match tcx.hir().get(hir_id) {
1021         Node::Item(item) => item,
1022         _ => bug!(),
1023     };
1024
1025     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1026     let (kind, variants) = match item.kind {
1027         ItemKind::Enum(ref def, _) => {
1028             let mut distance_from_explicit = 0;
1029             let variants = def
1030                 .variants
1031                 .iter()
1032                 .map(|v| {
1033                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1034                     let ctor_did =
1035                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1036
1037                     let discr = if let Some(ref e) = v.disr_expr {
1038                         distance_from_explicit = 0;
1039                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1040                     } else {
1041                         ty::VariantDiscr::Relative(distance_from_explicit)
1042                     };
1043                     distance_from_explicit += 1;
1044
1045                     convert_variant(
1046                         tcx,
1047                         variant_did,
1048                         ctor_did,
1049                         v.ident,
1050                         discr,
1051                         &v.data,
1052                         AdtKind::Enum,
1053                         def_id,
1054                     )
1055                 })
1056                 .collect();
1057
1058             (AdtKind::Enum, variants)
1059         }
1060         ItemKind::Struct(ref def, _) => {
1061             let variant_did = None::<LocalDefId>;
1062             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1063
1064             let variants = std::iter::once(convert_variant(
1065                 tcx,
1066                 variant_did,
1067                 ctor_did,
1068                 item.ident,
1069                 ty::VariantDiscr::Relative(0),
1070                 def,
1071                 AdtKind::Struct,
1072                 def_id,
1073             ))
1074             .collect();
1075
1076             (AdtKind::Struct, variants)
1077         }
1078         ItemKind::Union(ref def, _) => {
1079             let variant_did = None;
1080             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1081
1082             let variants = std::iter::once(convert_variant(
1083                 tcx,
1084                 variant_did,
1085                 ctor_did,
1086                 item.ident,
1087                 ty::VariantDiscr::Relative(0),
1088                 def,
1089                 AdtKind::Union,
1090                 def_id,
1091             ))
1092             .collect();
1093
1094             (AdtKind::Union, variants)
1095         }
1096         _ => bug!(),
1097     };
1098     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1099 }
1100
1101 /// Ensures that the super-predicates of the trait with a `DefId`
1102 /// of `trait_def_id` are converted and stored. This also ensures that
1103 /// the transitive super-predicates are converted.
1104 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1105     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1106     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1107 }
1108
1109 /// Ensures that the super-predicates of the trait with a `DefId`
1110 /// of `trait_def_id` are converted and stored. This also ensures that
1111 /// the transitive super-predicates are converted.
1112 fn super_predicates_that_define_assoc_type(
1113     tcx: TyCtxt<'_>,
1114     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1115 ) -> ty::GenericPredicates<'_> {
1116     debug!(
1117         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1118         trait_def_id, assoc_name
1119     );
1120     if trait_def_id.is_local() {
1121         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1122         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1123
1124         let item = match tcx.hir().get(trait_hir_id) {
1125             Node::Item(item) => item,
1126             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1127         };
1128
1129         let (generics, bounds) = match item.kind {
1130             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1131             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1132             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1133         };
1134
1135         let icx = ItemCtxt::new(tcx, trait_def_id);
1136
1137         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1138         let self_param_ty = tcx.types.self_param;
1139         let superbounds1 = if let Some(assoc_name) = assoc_name {
1140             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1141                 &icx,
1142                 self_param_ty,
1143                 bounds,
1144                 assoc_name,
1145             )
1146         } else {
1147             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1148         };
1149
1150         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1151
1152         // Convert any explicit superbounds in the where-clause,
1153         // e.g., `trait Foo where Self: Bar`.
1154         // In the case of trait aliases, however, we include all bounds in the where-clause,
1155         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1156         // as one of its "superpredicates".
1157         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1158         let superbounds2 = icx.type_parameter_bounds_in_generics(
1159             generics,
1160             item.hir_id(),
1161             self_param_ty,
1162             OnlySelfBounds(!is_trait_alias),
1163             assoc_name,
1164         );
1165
1166         // Combine the two lists to form the complete set of superbounds:
1167         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1168
1169         // Now require that immediate supertraits are converted,
1170         // which will, in turn, reach indirect supertraits.
1171         if assoc_name.is_none() {
1172             // Now require that immediate supertraits are converted,
1173             // which will, in turn, reach indirect supertraits.
1174             for &(pred, span) in superbounds {
1175                 debug!("superbound: {:?}", pred);
1176                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1177                     tcx.at(span).super_predicates_of(bound.def_id());
1178                 }
1179             }
1180         }
1181
1182         ty::GenericPredicates { parent: None, predicates: superbounds }
1183     } else {
1184         // if `assoc_name` is None, then the query should've been redirected to an
1185         // external provider
1186         assert!(assoc_name.is_some());
1187         tcx.super_predicates_of(trait_def_id)
1188     }
1189 }
1190
1191 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1192     let item = tcx.hir().expect_item(def_id.expect_local());
1193
1194     let (is_auto, unsafety) = match item.kind {
1195         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1196         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1197         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1198     };
1199
1200     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1201     if paren_sugar && !tcx.features().unboxed_closures {
1202         tcx.sess
1203             .struct_span_err(
1204                 item.span,
1205                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1206                  which traits can use parenthetical notation",
1207             )
1208             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1209             .emit();
1210     }
1211
1212     let is_marker = tcx.has_attr(def_id, sym::marker);
1213     let skip_array_during_method_dispatch =
1214         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1215     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1216         ty::trait_def::TraitSpecializationKind::Marker
1217     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1218         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1219     } else {
1220         ty::trait_def::TraitSpecializationKind::None
1221     };
1222     let def_path_hash = tcx.def_path_hash(def_id);
1223     ty::TraitDef::new(
1224         def_id,
1225         unsafety,
1226         paren_sugar,
1227         is_auto,
1228         is_marker,
1229         skip_array_during_method_dispatch,
1230         spec_kind,
1231         def_path_hash,
1232     )
1233 }
1234
1235 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1236     struct LateBoundRegionsDetector<'tcx> {
1237         tcx: TyCtxt<'tcx>,
1238         outer_index: ty::DebruijnIndex,
1239         has_late_bound_regions: Option<Span>,
1240     }
1241
1242     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1243         type Map = intravisit::ErasedMap<'tcx>;
1244
1245         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1246             NestedVisitorMap::None
1247         }
1248
1249         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1250             if self.has_late_bound_regions.is_some() {
1251                 return;
1252             }
1253             match ty.kind {
1254                 hir::TyKind::BareFn(..) => {
1255                     self.outer_index.shift_in(1);
1256                     intravisit::walk_ty(self, ty);
1257                     self.outer_index.shift_out(1);
1258                 }
1259                 _ => intravisit::walk_ty(self, ty),
1260             }
1261         }
1262
1263         fn visit_poly_trait_ref(
1264             &mut self,
1265             tr: &'tcx hir::PolyTraitRef<'tcx>,
1266             m: hir::TraitBoundModifier,
1267         ) {
1268             if self.has_late_bound_regions.is_some() {
1269                 return;
1270             }
1271             self.outer_index.shift_in(1);
1272             intravisit::walk_poly_trait_ref(self, tr, m);
1273             self.outer_index.shift_out(1);
1274         }
1275
1276         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1277             if self.has_late_bound_regions.is_some() {
1278                 return;
1279             }
1280
1281             match self.tcx.named_region(lt.hir_id) {
1282                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1283                 Some(
1284                     rl::Region::LateBound(debruijn, _, _, _)
1285                     | rl::Region::LateBoundAnon(debruijn, _, _),
1286                 ) if debruijn < self.outer_index => {}
1287                 Some(
1288                     rl::Region::LateBound(..)
1289                     | rl::Region::LateBoundAnon(..)
1290                     | rl::Region::Free(..),
1291                 )
1292                 | None => {
1293                     self.has_late_bound_regions = Some(lt.span);
1294                 }
1295             }
1296         }
1297     }
1298
1299     fn has_late_bound_regions<'tcx>(
1300         tcx: TyCtxt<'tcx>,
1301         generics: &'tcx hir::Generics<'tcx>,
1302         decl: &'tcx hir::FnDecl<'tcx>,
1303     ) -> Option<Span> {
1304         let mut visitor = LateBoundRegionsDetector {
1305             tcx,
1306             outer_index: ty::INNERMOST,
1307             has_late_bound_regions: None,
1308         };
1309         for param in generics.params {
1310             if let GenericParamKind::Lifetime { .. } = param.kind {
1311                 if tcx.is_late_bound(param.hir_id) {
1312                     return Some(param.span);
1313                 }
1314             }
1315         }
1316         visitor.visit_fn_decl(decl);
1317         visitor.has_late_bound_regions
1318     }
1319
1320     match node {
1321         Node::TraitItem(item) => match item.kind {
1322             hir::TraitItemKind::Fn(ref sig, _) => {
1323                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1324             }
1325             _ => None,
1326         },
1327         Node::ImplItem(item) => match item.kind {
1328             hir::ImplItemKind::Fn(ref sig, _) => {
1329                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1330             }
1331             _ => None,
1332         },
1333         Node::ForeignItem(item) => match item.kind {
1334             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1335                 has_late_bound_regions(tcx, generics, fn_decl)
1336             }
1337             _ => None,
1338         },
1339         Node::Item(item) => match item.kind {
1340             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1341                 has_late_bound_regions(tcx, generics, sig.decl)
1342             }
1343             _ => None,
1344         },
1345         _ => None,
1346     }
1347 }
1348
1349 struct AnonConstInParamTyDetector {
1350     in_param_ty: bool,
1351     found_anon_const_in_param_ty: bool,
1352     ct: HirId,
1353 }
1354
1355 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1356     type Map = intravisit::ErasedMap<'v>;
1357
1358     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1359         NestedVisitorMap::None
1360     }
1361
1362     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1363         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1364             let prev = self.in_param_ty;
1365             self.in_param_ty = true;
1366             self.visit_ty(ty);
1367             self.in_param_ty = prev;
1368         }
1369     }
1370
1371     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1372         if self.in_param_ty && self.ct == c.hir_id {
1373             self.found_anon_const_in_param_ty = true;
1374         } else {
1375             intravisit::walk_anon_const(self, c)
1376         }
1377     }
1378 }
1379
1380 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1381     use rustc_hir::*;
1382
1383     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1384
1385     let node = tcx.hir().get(hir_id);
1386     let parent_def_id = match node {
1387         Node::ImplItem(_)
1388         | Node::TraitItem(_)
1389         | Node::Variant(_)
1390         | Node::Ctor(..)
1391         | Node::Field(_) => {
1392             let parent_id = tcx.hir().get_parent_item(hir_id);
1393             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1394         }
1395         // FIXME(#43408) always enable this once `lazy_normalization` is
1396         // stable enough and does not need a feature gate anymore.
1397         Node::AnonConst(_) => {
1398             let parent_id = tcx.hir().get_parent_item(hir_id);
1399             let parent_def_id = tcx.hir().local_def_id(parent_id);
1400
1401             let mut in_param_ty = false;
1402             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1403                 if let Some(generics) = node.generics() {
1404                     let mut visitor = AnonConstInParamTyDetector {
1405                         in_param_ty: false,
1406                         found_anon_const_in_param_ty: false,
1407                         ct: hir_id,
1408                     };
1409
1410                     visitor.visit_generics(generics);
1411                     in_param_ty = visitor.found_anon_const_in_param_ty;
1412                     break;
1413                 }
1414             }
1415
1416             if in_param_ty {
1417                 // We do not allow generic parameters in anon consts if we are inside
1418                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1419                 None
1420             } else if tcx.lazy_normalization() {
1421                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1422                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1423                     //
1424                     // struct Foo<const N: usize = { .. }>;
1425                     //        ^^^       ^          ^^^^^^ def id of this anon const
1426                     //        ^         ^ param_id
1427                     //        ^ parent_def_id
1428                     //
1429                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1430                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1431                     //
1432                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1433                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1434                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1435                     //
1436                     // We fix this by having this function return the parent's generics ourselves and truncating the
1437                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1438                     //
1439                     // For the above code example that means we want `substs: []`
1440                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1441                     // the def id of the `{ N + 1 }` anon const
1442                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1443                     //
1444                     // This has some implications for how we get the predicates available to the anon const
1445                     // see `explicit_predicates_of` for more information on this
1446                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1447                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1448                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1449                     // In the above example this would be .params[..N#0]
1450                     let params = generics.params[..param_def_idx as usize].to_owned();
1451                     let param_def_id_to_index =
1452                         params.iter().map(|param| (param.def_id, param.index)).collect();
1453
1454                     return ty::Generics {
1455                         // we set the parent of these generics to be our parent's parent so that we
1456                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1457                         // struct Foo<const N: usize, const M: usize = { ... }>;
1458                         parent: generics.parent,
1459                         parent_count: generics.parent_count,
1460                         params,
1461                         param_def_id_to_index,
1462                         has_self: generics.has_self,
1463                         has_late_bound_regions: generics.has_late_bound_regions,
1464                     };
1465                 }
1466
1467                 // HACK(eddyb) this provides the correct generics when
1468                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1469                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1470                 //
1471                 // Note that we do not supply the parent generics when using
1472                 // `min_const_generics`.
1473                 Some(parent_def_id.to_def_id())
1474             } else {
1475                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1476                 match parent_node {
1477                     // HACK(eddyb) this provides the correct generics for repeat
1478                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1479                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1480                     // as they shouldn't be able to cause query cycle errors.
1481                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1482                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1483                         if constant.hir_id == hir_id =>
1484                     {
1485                         Some(parent_def_id.to_def_id())
1486                     }
1487                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1488                         Some(tcx.typeck_root_def_id(def_id))
1489                     }
1490                     _ => None,
1491                 }
1492             }
1493         }
1494         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1495             Some(tcx.typeck_root_def_id(def_id))
1496         }
1497         Node::Item(item) => match item.kind {
1498             ItemKind::OpaqueTy(hir::OpaqueTy {
1499                 origin:
1500                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1501                 ..
1502             }) => Some(fn_def_id.to_def_id()),
1503             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1504                 let parent_id = tcx.hir().get_parent_item(hir_id);
1505                 assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1506                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1507                 // Opaque types are always nested within another item, and
1508                 // inherit the generics of the item.
1509                 Some(tcx.hir().local_def_id(parent_id).to_def_id())
1510             }
1511             _ => None,
1512         },
1513         _ => None,
1514     };
1515
1516     let mut opt_self = None;
1517     let mut allow_defaults = false;
1518
1519     let no_generics = hir::Generics::empty();
1520     let ast_generics = match node {
1521         Node::TraitItem(item) => &item.generics,
1522
1523         Node::ImplItem(item) => &item.generics,
1524
1525         Node::Item(item) => {
1526             match item.kind {
1527                 ItemKind::Fn(.., ref generics, _)
1528                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1529
1530                 ItemKind::TyAlias(_, ref generics)
1531                 | ItemKind::Enum(_, ref generics)
1532                 | ItemKind::Struct(_, ref generics)
1533                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1534                 | ItemKind::Union(_, ref generics) => {
1535                     allow_defaults = true;
1536                     generics
1537                 }
1538
1539                 ItemKind::Trait(_, _, ref generics, ..)
1540                 | ItemKind::TraitAlias(ref generics, ..) => {
1541                     // Add in the self type parameter.
1542                     //
1543                     // Something of a hack: use the node id for the trait, also as
1544                     // the node id for the Self type parameter.
1545                     let param_id = item.def_id;
1546
1547                     opt_self = Some(ty::GenericParamDef {
1548                         index: 0,
1549                         name: kw::SelfUpper,
1550                         def_id: param_id.to_def_id(),
1551                         pure_wrt_drop: false,
1552                         kind: ty::GenericParamDefKind::Type {
1553                             has_default: false,
1554                             object_lifetime_default: rl::Set1::Empty,
1555                             synthetic: false,
1556                         },
1557                     });
1558
1559                     allow_defaults = true;
1560                     generics
1561                 }
1562
1563                 _ => &no_generics,
1564             }
1565         }
1566
1567         Node::ForeignItem(item) => match item.kind {
1568             ForeignItemKind::Static(..) => &no_generics,
1569             ForeignItemKind::Fn(_, _, ref generics) => generics,
1570             ForeignItemKind::Type => &no_generics,
1571         },
1572
1573         _ => &no_generics,
1574     };
1575
1576     let has_self = opt_self.is_some();
1577     let mut parent_has_self = false;
1578     let mut own_start = has_self as u32;
1579     let parent_count = parent_def_id.map_or(0, |def_id| {
1580         let generics = tcx.generics_of(def_id);
1581         assert!(!has_self);
1582         parent_has_self = generics.has_self;
1583         own_start = generics.count() as u32;
1584         generics.parent_count + generics.params.len()
1585     });
1586
1587     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1588
1589     if let Some(opt_self) = opt_self {
1590         params.push(opt_self);
1591     }
1592
1593     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1594     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1595         name: param.name.ident().name,
1596         index: own_start + i as u32,
1597         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1598         pure_wrt_drop: param.pure_wrt_drop,
1599         kind: ty::GenericParamDefKind::Lifetime,
1600     }));
1601
1602     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1603
1604     // Now create the real type and const parameters.
1605     let type_start = own_start - has_self as u32 + params.len() as u32;
1606     let mut i = 0;
1607
1608     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1609         GenericParamKind::Lifetime { .. } => None,
1610         GenericParamKind::Type { ref default, synthetic, .. } => {
1611             if !allow_defaults && default.is_some() {
1612                 if !tcx.features().default_type_parameter_fallback {
1613                     tcx.struct_span_lint_hir(
1614                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1615                         param.hir_id,
1616                         param.span,
1617                         |lint| {
1618                             lint.build(
1619                                 "defaults for type parameters are only allowed in \
1620                                  `struct`, `enum`, `type`, or `trait` definitions",
1621                             )
1622                             .emit();
1623                         },
1624                     );
1625                 }
1626             }
1627
1628             let kind = ty::GenericParamDefKind::Type {
1629                 has_default: default.is_some(),
1630                 object_lifetime_default: object_lifetime_defaults
1631                     .as_ref()
1632                     .map_or(rl::Set1::Empty, |o| o[i]),
1633                 synthetic,
1634             };
1635
1636             let param_def = ty::GenericParamDef {
1637                 index: type_start + i as u32,
1638                 name: param.name.ident().name,
1639                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1640                 pure_wrt_drop: param.pure_wrt_drop,
1641                 kind,
1642             };
1643             i += 1;
1644             Some(param_def)
1645         }
1646         GenericParamKind::Const { default, .. } => {
1647             if !allow_defaults && default.is_some() {
1648                 tcx.sess.span_err(
1649                     param.span,
1650                     "defaults for const parameters are only allowed in \
1651                     `struct`, `enum`, `type`, or `trait` definitions",
1652                 );
1653             }
1654
1655             let param_def = ty::GenericParamDef {
1656                 index: type_start + i as u32,
1657                 name: param.name.ident().name,
1658                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1659                 pure_wrt_drop: param.pure_wrt_drop,
1660                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1661             };
1662             i += 1;
1663             Some(param_def)
1664         }
1665     }));
1666
1667     // provide junk type parameter defs - the only place that
1668     // cares about anything but the length is instantiation,
1669     // and we don't do that for closures.
1670     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1671         let dummy_args = if gen.is_some() {
1672             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1673         } else {
1674             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1675         };
1676
1677         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1678             index: type_start + i as u32,
1679             name: Symbol::intern(arg),
1680             def_id,
1681             pure_wrt_drop: false,
1682             kind: ty::GenericParamDefKind::Type {
1683                 has_default: false,
1684                 object_lifetime_default: rl::Set1::Empty,
1685                 synthetic: false,
1686             },
1687         }));
1688     }
1689
1690     // provide junk type parameter defs for const blocks.
1691     if let Node::AnonConst(_) = node {
1692         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1693         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1694             params.push(ty::GenericParamDef {
1695                 index: type_start,
1696                 name: Symbol::intern("<const_ty>"),
1697                 def_id,
1698                 pure_wrt_drop: false,
1699                 kind: ty::GenericParamDefKind::Type {
1700                     has_default: false,
1701                     object_lifetime_default: rl::Set1::Empty,
1702                     synthetic: false,
1703                 },
1704             });
1705         }
1706     }
1707
1708     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1709
1710     ty::Generics {
1711         parent: parent_def_id,
1712         parent_count,
1713         params,
1714         param_def_id_to_index,
1715         has_self: has_self || parent_has_self,
1716         has_late_bound_regions: has_late_bound_regions(tcx, node),
1717     }
1718 }
1719
1720 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1721     generic_args.iter().any(|arg| match arg {
1722         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1723         hir::GenericArg::Infer(_) => true,
1724         _ => false,
1725     })
1726 }
1727
1728 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1729 /// use inference to provide suggestions for the appropriate type if possible.
1730 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1731     use hir::TyKind::*;
1732     match &ty.kind {
1733         Infer => true,
1734         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1735         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1736         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1737         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1738         Path(hir::QPath::TypeRelative(ty, segment)) => {
1739             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1740         }
1741         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1742             ty_opt.map_or(false, is_suggestable_infer_ty)
1743                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1744         }
1745         _ => false,
1746     }
1747 }
1748
1749 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1750     if let hir::FnRetTy::Return(ty) = output {
1751         if is_suggestable_infer_ty(ty) {
1752             return Some(&*ty);
1753         }
1754     }
1755     None
1756 }
1757
1758 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1759     use rustc_hir::Node::*;
1760     use rustc_hir::*;
1761
1762     let def_id = def_id.expect_local();
1763     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1764
1765     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1766
1767     match tcx.hir().get(hir_id) {
1768         TraitItem(hir::TraitItem {
1769             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1770             ident,
1771             generics,
1772             ..
1773         })
1774         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1775         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1776             match get_infer_ret_ty(&sig.decl.output) {
1777                 Some(ty) => {
1778                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1779                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1780                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1781                         ty::ReErased => tcx.lifetimes.re_static,
1782                         _ => r,
1783                     });
1784                     let fn_sig = ty::Binder::dummy(fn_sig);
1785
1786                     let mut visitor = PlaceholderHirTyCollector::default();
1787                     visitor.visit_ty(ty);
1788                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
1789                     let ret_ty = fn_sig.skip_binder().output();
1790                     if !ret_ty.references_error() {
1791                         if !ret_ty.is_closure() {
1792                             let ret_ty_str = match ret_ty.kind() {
1793                                 // Suggest a function pointer return type instead of a unique function definition
1794                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1795                                 // syntax)
1796                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1797                                 _ => ret_ty.to_string(),
1798                             };
1799                             diag.span_suggestion(
1800                                 ty.span,
1801                                 "replace with the correct return type",
1802                                 ret_ty_str,
1803                                 Applicability::MaybeIncorrect,
1804                             );
1805                         } else {
1806                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1807                             // to prevent the user from getting a papercut while trying to use the unique closure
1808                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1809                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1810                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1811                         }
1812                     }
1813                     diag.emit();
1814
1815                     fn_sig
1816                 }
1817                 None => <dyn AstConv<'_>>::ty_of_fn(
1818                     &icx,
1819                     hir_id,
1820                     sig.header.unsafety,
1821                     sig.header.abi,
1822                     sig.decl,
1823                     generics,
1824                     Some(ident.span),
1825                     None,
1826                 ),
1827             }
1828         }
1829
1830         TraitItem(hir::TraitItem {
1831             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1832             ident,
1833             generics,
1834             ..
1835         }) => <dyn AstConv<'_>>::ty_of_fn(
1836             &icx,
1837             hir_id,
1838             header.unsafety,
1839             header.abi,
1840             decl,
1841             generics,
1842             Some(ident.span),
1843             None,
1844         ),
1845
1846         ForeignItem(&hir::ForeignItem {
1847             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1848         }) => {
1849             let abi = tcx.hir().get_foreign_abi(hir_id);
1850             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1851         }
1852
1853         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1854             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1855             let inputs =
1856                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1857             ty::Binder::dummy(tcx.mk_fn_sig(
1858                 inputs,
1859                 ty,
1860                 false,
1861                 hir::Unsafety::Normal,
1862                 abi::Abi::Rust,
1863             ))
1864         }
1865
1866         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1867             // Closure signatures are not like other function
1868             // signatures and cannot be accessed through `fn_sig`. For
1869             // example, a closure signature excludes the `self`
1870             // argument. In any case they are embedded within the
1871             // closure type as part of the `ClosureSubsts`.
1872             //
1873             // To get the signature of a closure, you should use the
1874             // `sig` method on the `ClosureSubsts`:
1875             //
1876             //    substs.as_closure().sig(def_id, tcx)
1877             bug!(
1878                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1879             );
1880         }
1881
1882         x => {
1883             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1884         }
1885     }
1886 }
1887
1888 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1889     let icx = ItemCtxt::new(tcx, def_id);
1890     match tcx.hir().expect_item(def_id.expect_local()).kind {
1891         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1892             let selfty = tcx.type_of(def_id);
1893             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1894         }),
1895         _ => bug!(),
1896     }
1897 }
1898
1899 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1900     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1901     let item = tcx.hir().expect_item(def_id.expect_local());
1902     match &item.kind {
1903         hir::ItemKind::Impl(hir::Impl {
1904             polarity: hir::ImplPolarity::Negative(span),
1905             of_trait,
1906             ..
1907         }) => {
1908             if is_rustc_reservation {
1909                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1910                 tcx.sess.span_err(span, "reservation impls can't be negative");
1911             }
1912             ty::ImplPolarity::Negative
1913         }
1914         hir::ItemKind::Impl(hir::Impl {
1915             polarity: hir::ImplPolarity::Positive,
1916             of_trait: None,
1917             ..
1918         }) => {
1919             if is_rustc_reservation {
1920                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1921             }
1922             ty::ImplPolarity::Positive
1923         }
1924         hir::ItemKind::Impl(hir::Impl {
1925             polarity: hir::ImplPolarity::Positive,
1926             of_trait: Some(_),
1927             ..
1928         }) => {
1929             if is_rustc_reservation {
1930                 ty::ImplPolarity::Reservation
1931             } else {
1932                 ty::ImplPolarity::Positive
1933             }
1934         }
1935         item => bug!("impl_polarity: {:?} not an impl", item),
1936     }
1937 }
1938
1939 /// Returns the early-bound lifetimes declared in this generics
1940 /// listing. For anything other than fns/methods, this is just all
1941 /// the lifetimes that are declared. For fns or methods, we have to
1942 /// screen out those that do not appear in any where-clauses etc using
1943 /// `resolve_lifetime::early_bound_lifetimes`.
1944 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1945     tcx: TyCtxt<'tcx>,
1946     generics: &'a hir::Generics<'a>,
1947 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1948     generics.params.iter().filter(move |param| match param.kind {
1949         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1950         _ => false,
1951     })
1952 }
1953
1954 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1955 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1956 /// inferred constraints concerning which regions outlive other regions.
1957 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1958     debug!("predicates_defined_on({:?})", def_id);
1959     let mut result = tcx.explicit_predicates_of(def_id);
1960     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1961     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1962     if !inferred_outlives.is_empty() {
1963         debug!(
1964             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1965             def_id, inferred_outlives,
1966         );
1967         if result.predicates.is_empty() {
1968             result.predicates = inferred_outlives;
1969         } else {
1970             result.predicates = tcx
1971                 .arena
1972                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1973         }
1974     }
1975
1976     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1977     result
1978 }
1979
1980 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1981 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1982 /// `Self: Trait` predicates for traits.
1983 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1984     let mut result = tcx.predicates_defined_on(def_id);
1985
1986     if tcx.is_trait(def_id) {
1987         // For traits, add `Self: Trait` predicate. This is
1988         // not part of the predicates that a user writes, but it
1989         // is something that one must prove in order to invoke a
1990         // method or project an associated type.
1991         //
1992         // In the chalk setup, this predicate is not part of the
1993         // "predicates" for a trait item. But it is useful in
1994         // rustc because if you directly (e.g.) invoke a trait
1995         // method like `Trait::method(...)`, you must naturally
1996         // prove that the trait applies to the types that were
1997         // used, and adding the predicate into this list ensures
1998         // that this is done.
1999         //
2000         // We use a DUMMY_SP here as a way to signal trait bounds that come
2001         // from the trait itself that *shouldn't* be shown as the source of
2002         // an obligation and instead be skipped. Otherwise we'd use
2003         // `tcx.def_span(def_id);`
2004         let span = rustc_span::DUMMY_SP;
2005         result.predicates =
2006             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2007                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2008                 span,
2009             ))));
2010     }
2011     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2012     result
2013 }
2014
2015 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2016 /// N.B., this does not include any implied/inferred constraints.
2017 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2018     use rustc_hir::*;
2019
2020     debug!("explicit_predicates_of(def_id={:?})", def_id);
2021
2022     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2023     let node = tcx.hir().get(hir_id);
2024
2025     let mut is_trait = None;
2026     let mut is_default_impl_trait = None;
2027
2028     let icx = ItemCtxt::new(tcx, def_id);
2029
2030     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2031
2032     // We use an `IndexSet` to preserves order of insertion.
2033     // Preserving the order of insertion is important here so as not to break UI tests.
2034     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2035
2036     let ast_generics = match node {
2037         Node::TraitItem(item) => &item.generics,
2038
2039         Node::ImplItem(item) => &item.generics,
2040
2041         Node::Item(item) => {
2042             match item.kind {
2043                 ItemKind::Impl(ref impl_) => {
2044                     if impl_.defaultness.is_default() {
2045                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2046                     }
2047                     &impl_.generics
2048                 }
2049                 ItemKind::Fn(.., ref generics, _)
2050                 | ItemKind::TyAlias(_, ref generics)
2051                 | ItemKind::Enum(_, ref generics)
2052                 | ItemKind::Struct(_, ref generics)
2053                 | ItemKind::Union(_, ref generics) => generics,
2054
2055                 ItemKind::Trait(_, _, ref generics, ..) => {
2056                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2057                     generics
2058                 }
2059                 ItemKind::TraitAlias(ref generics, _) => {
2060                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2061                     generics
2062                 }
2063                 ItemKind::OpaqueTy(OpaqueTy {
2064                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2065                     ..
2066                 }) => {
2067                     // return-position impl trait
2068                     //
2069                     // We don't inherit predicates from the parent here:
2070                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2071                     // then the return type is `f::<'static, T>::{{opaque}}`.
2072                     //
2073                     // If we inherited the predicates of `f` then we would
2074                     // require that `T: 'static` to show that the return
2075                     // type is well-formed.
2076                     //
2077                     // The only way to have something with this opaque type
2078                     // is from the return type of the containing function,
2079                     // which will ensure that the function's predicates
2080                     // hold.
2081                     return ty::GenericPredicates { parent: None, predicates: &[] };
2082                 }
2083                 ItemKind::OpaqueTy(OpaqueTy {
2084                     ref generics,
2085                     origin: hir::OpaqueTyOrigin::TyAlias,
2086                     ..
2087                 }) => {
2088                     // type-alias impl trait
2089                     generics
2090                 }
2091
2092                 _ => NO_GENERICS,
2093             }
2094         }
2095
2096         Node::ForeignItem(item) => match item.kind {
2097             ForeignItemKind::Static(..) => NO_GENERICS,
2098             ForeignItemKind::Fn(_, _, ref generics) => generics,
2099             ForeignItemKind::Type => NO_GENERICS,
2100         },
2101
2102         _ => NO_GENERICS,
2103     };
2104
2105     let generics = tcx.generics_of(def_id);
2106     let parent_count = generics.parent_count as u32;
2107     let has_own_self = generics.has_self && parent_count == 0;
2108
2109     // Below we'll consider the bounds on the type parameters (including `Self`)
2110     // and the explicit where-clauses, but to get the full set of predicates
2111     // on a trait we need to add in the supertrait bounds and bounds found on
2112     // associated types.
2113     if let Some(_trait_ref) = is_trait {
2114         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2115     }
2116
2117     // In default impls, we can assume that the self type implements
2118     // the trait. So in:
2119     //
2120     //     default impl Foo for Bar { .. }
2121     //
2122     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2123     // (see below). Recall that a default impl is not itself an impl, but rather a
2124     // set of defaults that can be incorporated into another impl.
2125     if let Some(trait_ref) = is_default_impl_trait {
2126         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2127     }
2128
2129     // Collect the region predicates that were declared inline as
2130     // well. In the case of parameters declared on a fn or method, we
2131     // have to be careful to only iterate over early-bound regions.
2132     let mut index = parent_count + has_own_self as u32;
2133     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2134         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2135             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2136             index,
2137             name: param.name.ident().name,
2138         }));
2139         index += 1;
2140
2141         match param.kind {
2142             GenericParamKind::Lifetime { .. } => {
2143                 param.bounds.iter().for_each(|bound| match bound {
2144                     hir::GenericBound::Outlives(lt) => {
2145                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2146                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2147                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2148                     }
2149                     _ => bug!(),
2150                 });
2151             }
2152             _ => bug!(),
2153         }
2154     }
2155
2156     // Collect the predicates that were written inline by the user on each
2157     // type parameter (e.g., `<T: Foo>`).
2158     for param in ast_generics.params {
2159         match param.kind {
2160             // We already dealt with early bound lifetimes above.
2161             GenericParamKind::Lifetime { .. } => (),
2162             GenericParamKind::Type { .. } => {
2163                 let name = param.name.ident().name;
2164                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2165                 index += 1;
2166
2167                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2168                 // Params are implicitly sized unless a `?Sized` bound is found
2169                 <dyn AstConv<'_>>::add_implicitly_sized(
2170                     &icx,
2171                     &mut bounds,
2172                     param.bounds,
2173                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2174                     param.span,
2175                 );
2176                 predicates.extend(bounds.predicates(tcx, param_ty));
2177             }
2178             GenericParamKind::Const { .. } => {
2179                 // Bounds on const parameters are currently not possible.
2180                 debug_assert!(param.bounds.is_empty());
2181                 index += 1;
2182             }
2183         }
2184     }
2185
2186     // Add in the bounds that appear in the where-clause.
2187     let where_clause = &ast_generics.where_clause;
2188     for predicate in where_clause.predicates {
2189         match predicate {
2190             hir::WherePredicate::BoundPredicate(bound_pred) => {
2191                 let ty = icx.to_ty(bound_pred.bounded_ty);
2192                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2193
2194                 // Keep the type around in a dummy predicate, in case of no bounds.
2195                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2196                 // is still checked for WF.
2197                 if bound_pred.bounds.is_empty() {
2198                     if let ty::Param(_) = ty.kind() {
2199                         // This is a `where T:`, which can be in the HIR from the
2200                         // transformation that moves `?Sized` to `T`'s declaration.
2201                         // We can skip the predicate because type parameters are
2202                         // trivially WF, but also we *should*, to avoid exposing
2203                         // users who never wrote `where Type:,` themselves, to
2204                         // compiler/tooling bugs from not handling WF predicates.
2205                     } else {
2206                         let span = bound_pred.bounded_ty.span;
2207                         let re_root_empty = tcx.lifetimes.re_root_empty;
2208                         let predicate = ty::Binder::bind_with_vars(
2209                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2210                                 ty,
2211                                 re_root_empty,
2212                             )),
2213                             bound_vars,
2214                         );
2215                         predicates.insert((predicate.to_predicate(tcx), span));
2216                     }
2217                 }
2218
2219                 let mut bounds = Bounds::default();
2220                 <dyn AstConv<'_>>::add_bounds(
2221                     &icx,
2222                     ty,
2223                     bound_pred.bounds.iter(),
2224                     &mut bounds,
2225                     bound_vars,
2226                 );
2227                 predicates.extend(bounds.predicates(tcx, ty));
2228             }
2229
2230             hir::WherePredicate::RegionPredicate(region_pred) => {
2231                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2232                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2233                     let (r2, span) = match bound {
2234                         hir::GenericBound::Outlives(lt) => {
2235                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2236                         }
2237                         _ => bug!(),
2238                     };
2239                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2240                         ty::OutlivesPredicate(r1, r2),
2241                     ))
2242                     .to_predicate(icx.tcx);
2243
2244                     (pred, span)
2245                 }))
2246             }
2247
2248             hir::WherePredicate::EqPredicate(..) => {
2249                 // FIXME(#20041)
2250             }
2251         }
2252     }
2253
2254     if tcx.features().generic_const_exprs {
2255         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2256     }
2257
2258     let mut predicates: Vec<_> = predicates.into_iter().collect();
2259
2260     // Subtle: before we store the predicates into the tcx, we
2261     // sort them so that predicates like `T: Foo<Item=U>` come
2262     // before uses of `U`.  This avoids false ambiguity errors
2263     // in trait checking. See `setup_constraining_predicates`
2264     // for details.
2265     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2266         let self_ty = tcx.type_of(def_id);
2267         let trait_ref = tcx.impl_trait_ref(def_id);
2268         cgp::setup_constraining_predicates(
2269             tcx,
2270             &mut predicates,
2271             trait_ref,
2272             &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref),
2273         );
2274     }
2275
2276     let result = ty::GenericPredicates {
2277         parent: generics.parent,
2278         predicates: tcx.arena.alloc_from_iter(predicates),
2279     };
2280     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2281     result
2282 }
2283
2284 fn const_evaluatable_predicates_of<'tcx>(
2285     tcx: TyCtxt<'tcx>,
2286     def_id: LocalDefId,
2287 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2288     struct ConstCollector<'tcx> {
2289         tcx: TyCtxt<'tcx>,
2290         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2291     }
2292
2293     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2294         type Map = Map<'tcx>;
2295
2296         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2297             intravisit::NestedVisitorMap::None
2298         }
2299
2300         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2301             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2302             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2303             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2304                 assert_eq!(uv.promoted, None);
2305                 let span = self.tcx.hir().span(c.hir_id);
2306                 self.preds.insert((
2307                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2308                         .to_predicate(self.tcx),
2309                     span,
2310                 ));
2311             }
2312         }
2313
2314         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2315             // Do not look into const param defaults,
2316             // these get checked when they are actually instantiated.
2317             //
2318             // We do not want the following to error:
2319             //
2320             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2321             //     struct Bar<const N: usize>(Foo<N, 3>);
2322         }
2323     }
2324
2325     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2326     let node = tcx.hir().get(hir_id);
2327
2328     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2329     if let hir::Node::Item(item) = node {
2330         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2331             if let Some(of_trait) = &impl_.of_trait {
2332                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2333                 collector.visit_trait_ref(of_trait);
2334             }
2335
2336             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2337             collector.visit_ty(impl_.self_ty);
2338         }
2339     }
2340
2341     if let Some(generics) = node.generics() {
2342         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2343         collector.visit_generics(generics);
2344     }
2345
2346     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2347         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2348         collector.visit_fn_decl(fn_sig.decl);
2349     }
2350     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2351
2352     collector.preds
2353 }
2354
2355 fn trait_explicit_predicates_and_bounds(
2356     tcx: TyCtxt<'_>,
2357     def_id: LocalDefId,
2358 ) -> ty::GenericPredicates<'_> {
2359     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2360     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2361 }
2362
2363 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2364     let def_kind = tcx.def_kind(def_id);
2365     if let DefKind::Trait = def_kind {
2366         // Remove bounds on associated types from the predicates, they will be
2367         // returned by `explicit_item_bounds`.
2368         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2369         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2370
2371         let is_assoc_item_ty = |ty: Ty<'_>| {
2372             // For a predicate from a where clause to become a bound on an
2373             // associated type:
2374             // * It must use the identity substs of the item.
2375             //     * Since any generic parameters on the item are not in scope,
2376             //       this means that the item is not a GAT, and its identity
2377             //       substs are the same as the trait's.
2378             // * It must be an associated type for this trait (*not* a
2379             //   supertrait).
2380             if let ty::Projection(projection) = ty.kind() {
2381                 projection.substs == trait_identity_substs
2382                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2383             } else {
2384                 false
2385             }
2386         };
2387
2388         let predicates: Vec<_> = predicates_and_bounds
2389             .predicates
2390             .iter()
2391             .copied()
2392             .filter(|(pred, _)| match pred.kind().skip_binder() {
2393                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2394                 ty::PredicateKind::Projection(proj) => {
2395                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2396                 }
2397                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2398                 _ => true,
2399             })
2400             .collect();
2401         if predicates.len() == predicates_and_bounds.predicates.len() {
2402             predicates_and_bounds
2403         } else {
2404             ty::GenericPredicates {
2405                 parent: predicates_and_bounds.parent,
2406                 predicates: tcx.arena.alloc_slice(&predicates),
2407             }
2408         }
2409     } else {
2410         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2411             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2412             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2413                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2414                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2415                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2416                 //
2417                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2418                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2419                 //        ^^^                                             explicit_predicates_of on
2420                 //        parent item we dont have set as the
2421                 //        parent of generics returned by `generics_of`
2422                 //
2423                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2424                 let item_id = tcx.hir().get_parent_item(hir_id);
2425                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2426                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2427                 return tcx.explicit_predicates_of(item_def_id);
2428             }
2429         }
2430         gather_explicit_predicates_of(tcx, def_id)
2431     }
2432 }
2433
2434 /// Converts a specific `GenericBound` from the AST into a set of
2435 /// predicates that apply to the self type. A vector is returned
2436 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2437 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2438 /// and `<T as Bar>::X == i32`).
2439 fn predicates_from_bound<'tcx>(
2440     astconv: &dyn AstConv<'tcx>,
2441     param_ty: Ty<'tcx>,
2442     bound: &'tcx hir::GenericBound<'tcx>,
2443     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2444 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2445     let mut bounds = Bounds::default();
2446     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2447     bounds.predicates(astconv.tcx(), param_ty)
2448 }
2449
2450 fn compute_sig_of_foreign_fn_decl<'tcx>(
2451     tcx: TyCtxt<'tcx>,
2452     def_id: DefId,
2453     decl: &'tcx hir::FnDecl<'tcx>,
2454     abi: abi::Abi,
2455     ident: Ident,
2456 ) -> ty::PolyFnSig<'tcx> {
2457     let unsafety = if abi == abi::Abi::RustIntrinsic {
2458         intrinsic_operation_unsafety(tcx.item_name(def_id))
2459     } else {
2460         hir::Unsafety::Unsafe
2461     };
2462     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2463     let fty = <dyn AstConv<'_>>::ty_of_fn(
2464         &ItemCtxt::new(tcx, def_id),
2465         hir_id,
2466         unsafety,
2467         abi,
2468         decl,
2469         &hir::Generics::empty(),
2470         Some(ident.span),
2471         None,
2472     );
2473
2474     // Feature gate SIMD types in FFI, since I am not sure that the
2475     // ABIs are handled at all correctly. -huonw
2476     if abi != abi::Abi::RustIntrinsic
2477         && abi != abi::Abi::PlatformIntrinsic
2478         && !tcx.features().simd_ffi
2479     {
2480         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2481             if ty.is_simd() {
2482                 let snip = tcx
2483                     .sess
2484                     .source_map()
2485                     .span_to_snippet(ast_ty.span)
2486                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2487                 tcx.sess
2488                     .struct_span_err(
2489                         ast_ty.span,
2490                         &format!(
2491                             "use of SIMD type{} in FFI is highly experimental and \
2492                              may result in invalid code",
2493                             snip
2494                         ),
2495                     )
2496                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2497                     .emit();
2498             }
2499         };
2500         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2501             check(input, ty)
2502         }
2503         if let hir::FnRetTy::Return(ref ty) = decl.output {
2504             check(ty, fty.output().skip_binder())
2505         }
2506     }
2507
2508     fty
2509 }
2510
2511 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2512     match tcx.hir().get_if_local(def_id) {
2513         Some(Node::ForeignItem(..)) => true,
2514         Some(_) => false,
2515         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2516     }
2517 }
2518
2519 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2520     match tcx.hir().get_if_local(def_id) {
2521         Some(
2522             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2523             | Node::ForeignItem(&hir::ForeignItem {
2524                 kind: hir::ForeignItemKind::Static(_, mutbl),
2525                 ..
2526             }),
2527         ) => Some(mutbl),
2528         Some(_) => None,
2529         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2530     }
2531 }
2532
2533 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2534     match tcx.hir().get_if_local(def_id) {
2535         Some(Node::Expr(&rustc_hir::Expr {
2536             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2537             ..
2538         })) => tcx.hir().body(body_id).generator_kind(),
2539         Some(_) => None,
2540         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2541     }
2542 }
2543
2544 fn from_target_feature(
2545     tcx: TyCtxt<'_>,
2546     id: DefId,
2547     attr: &ast::Attribute,
2548     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2549     target_features: &mut Vec<Symbol>,
2550 ) {
2551     let list = match attr.meta_item_list() {
2552         Some(list) => list,
2553         None => return,
2554     };
2555     let bad_item = |span| {
2556         let msg = "malformed `target_feature` attribute input";
2557         let code = "enable = \"..\"".to_owned();
2558         tcx.sess
2559             .struct_span_err(span, msg)
2560             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2561             .emit();
2562     };
2563     let rust_features = tcx.features();
2564     for item in list {
2565         // Only `enable = ...` is accepted in the meta-item list.
2566         if !item.has_name(sym::enable) {
2567             bad_item(item.span());
2568             continue;
2569         }
2570
2571         // Must be of the form `enable = "..."` (a string).
2572         let value = match item.value_str() {
2573             Some(value) => value,
2574             None => {
2575                 bad_item(item.span());
2576                 continue;
2577             }
2578         };
2579
2580         // We allow comma separation to enable multiple features.
2581         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2582             let feature_gate = match supported_target_features.get(feature) {
2583                 Some(g) => g,
2584                 None => {
2585                     let msg =
2586                         format!("the feature named `{}` is not valid for this target", feature);
2587                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2588                     err.span_label(
2589                         item.span(),
2590                         format!("`{}` is not valid for this target", feature),
2591                     );
2592                     if let Some(stripped) = feature.strip_prefix('+') {
2593                         let valid = supported_target_features.contains_key(stripped);
2594                         if valid {
2595                             err.help("consider removing the leading `+` in the feature name");
2596                         }
2597                     }
2598                     err.emit();
2599                     return None;
2600                 }
2601             };
2602
2603             // Only allow features whose feature gates have been enabled.
2604             let allowed = match feature_gate.as_ref().copied() {
2605                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2606                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2607                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2608                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2609                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2610                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2611                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2612                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2613                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2614                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2615                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2616                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2617                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2618                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2619                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2620                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2621                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2622                 Some(name) => bug!("unknown target feature gate {}", name),
2623                 None => true,
2624             };
2625             if !allowed && id.is_local() {
2626                 feature_err(
2627                     &tcx.sess.parse_sess,
2628                     feature_gate.unwrap(),
2629                     item.span(),
2630                     &format!("the target feature `{}` is currently unstable", feature),
2631                 )
2632                 .emit();
2633             }
2634             Some(Symbol::intern(feature))
2635         }));
2636     }
2637 }
2638
2639 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2640     use rustc_middle::mir::mono::Linkage::*;
2641
2642     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2643     // applicable to variable declarations and may not really make sense for
2644     // Rust code in the first place but allow them anyway and trust that the
2645     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2646     // up in the future.
2647     //
2648     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2649     // and don't have to be, LLVM treats them as no-ops.
2650     match name {
2651         "appending" => Appending,
2652         "available_externally" => AvailableExternally,
2653         "common" => Common,
2654         "extern_weak" => ExternalWeak,
2655         "external" => External,
2656         "internal" => Internal,
2657         "linkonce" => LinkOnceAny,
2658         "linkonce_odr" => LinkOnceODR,
2659         "private" => Private,
2660         "weak" => WeakAny,
2661         "weak_odr" => WeakODR,
2662         _ => {
2663             let span = tcx.hir().span_if_local(def_id);
2664             if let Some(span) = span {
2665                 tcx.sess.span_fatal(span, "invalid linkage specified")
2666             } else {
2667                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2668             }
2669         }
2670     }
2671 }
2672
2673 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2674     let attrs = tcx.get_attrs(id);
2675
2676     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2677     if tcx.should_inherit_track_caller(id) {
2678         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2679     }
2680
2681     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2682     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2683         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2684             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2685         }
2686     }
2687
2688     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2689
2690     let mut inline_span = None;
2691     let mut link_ordinal_span = None;
2692     let mut no_sanitize_span = None;
2693     for attr in attrs.iter() {
2694         if attr.has_name(sym::cold) {
2695             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2696         } else if attr.has_name(sym::rustc_allocator) {
2697             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2698         } else if attr.has_name(sym::ffi_returns_twice) {
2699             if tcx.is_foreign_item(id) {
2700                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2701             } else {
2702                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2703                 struct_span_err!(
2704                     tcx.sess,
2705                     attr.span,
2706                     E0724,
2707                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2708                 )
2709                 .emit();
2710             }
2711         } else if attr.has_name(sym::ffi_pure) {
2712             if tcx.is_foreign_item(id) {
2713                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2714                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2715                     struct_span_err!(
2716                         tcx.sess,
2717                         attr.span,
2718                         E0757,
2719                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2720                     )
2721                     .emit();
2722                 } else {
2723                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2724                 }
2725             } else {
2726                 // `#[ffi_pure]` is only allowed on foreign functions
2727                 struct_span_err!(
2728                     tcx.sess,
2729                     attr.span,
2730                     E0755,
2731                     "`#[ffi_pure]` may only be used on foreign functions"
2732                 )
2733                 .emit();
2734             }
2735         } else if attr.has_name(sym::ffi_const) {
2736             if tcx.is_foreign_item(id) {
2737                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2738             } else {
2739                 // `#[ffi_const]` is only allowed on foreign functions
2740                 struct_span_err!(
2741                     tcx.sess,
2742                     attr.span,
2743                     E0756,
2744                     "`#[ffi_const]` may only be used on foreign functions"
2745                 )
2746                 .emit();
2747             }
2748         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2749             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2750         } else if attr.has_name(sym::naked) {
2751             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2752         } else if attr.has_name(sym::no_mangle) {
2753             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2754         } else if attr.has_name(sym::no_coverage) {
2755             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2756         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2757             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2758         } else if attr.has_name(sym::used) {
2759             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2760         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2761             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2762                 struct_span_err!(
2763                     tcx.sess,
2764                     attr.span,
2765                     E0776,
2766                     "`#[cmse_nonsecure_entry]` requires C ABI"
2767                 )
2768                 .emit();
2769             }
2770             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2771                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2772                     .emit();
2773             }
2774             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2775         } else if attr.has_name(sym::thread_local) {
2776             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2777         } else if attr.has_name(sym::track_caller) {
2778             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2779                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2780                     .emit();
2781             }
2782             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2783                 feature_err(
2784                     &tcx.sess.parse_sess,
2785                     sym::closure_track_caller,
2786                     attr.span,
2787                     "`#[track_caller]` on closures is currently unstable",
2788                 )
2789                 .emit();
2790             }
2791             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2792         } else if attr.has_name(sym::export_name) {
2793             if let Some(s) = attr.value_str() {
2794                 if s.as_str().contains('\0') {
2795                     // `#[export_name = ...]` will be converted to a null-terminated string,
2796                     // so it may not contain any null characters.
2797                     struct_span_err!(
2798                         tcx.sess,
2799                         attr.span,
2800                         E0648,
2801                         "`export_name` may not contain null characters"
2802                     )
2803                     .emit();
2804                 }
2805                 codegen_fn_attrs.export_name = Some(s);
2806             }
2807         } else if attr.has_name(sym::target_feature) {
2808             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2809                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2810                     // The `#[target_feature]` attribute is allowed on
2811                     // WebAssembly targets on all functions, including safe
2812                     // ones. Other targets require that `#[target_feature]` is
2813                     // only applied to unsafe funtions (pending the
2814                     // `target_feature_11` feature) because on most targets
2815                     // execution of instructions that are not supported is
2816                     // considered undefined behavior. For WebAssembly which is a
2817                     // 100% safe target at execution time it's not possible to
2818                     // execute undefined instructions, and even if a future
2819                     // feature was added in some form for this it would be a
2820                     // deterministic trap. There is no undefined behavior when
2821                     // executing WebAssembly so `#[target_feature]` is allowed
2822                     // on safe functions (but again, only for WebAssembly)
2823                     //
2824                     // Note that this is also allowed if `actually_rustdoc` so
2825                     // if a target is documenting some wasm-specific code then
2826                     // it's not spuriously denied.
2827                 } else if !tcx.features().target_feature_11 {
2828                     let mut err = feature_err(
2829                         &tcx.sess.parse_sess,
2830                         sym::target_feature_11,
2831                         attr.span,
2832                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2833                     );
2834                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2835                     err.emit();
2836                 } else if let Some(local_id) = id.as_local() {
2837                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2838                 }
2839             }
2840             from_target_feature(
2841                 tcx,
2842                 id,
2843                 attr,
2844                 supported_target_features,
2845                 &mut codegen_fn_attrs.target_features,
2846             );
2847         } else if attr.has_name(sym::linkage) {
2848             if let Some(val) = attr.value_str() {
2849                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2850             }
2851         } else if attr.has_name(sym::link_section) {
2852             if let Some(val) = attr.value_str() {
2853                 if val.as_str().bytes().any(|b| b == 0) {
2854                     let msg = format!(
2855                         "illegal null byte in link_section \
2856                          value: `{}`",
2857                         &val
2858                     );
2859                     tcx.sess.span_err(attr.span, &msg);
2860                 } else {
2861                     codegen_fn_attrs.link_section = Some(val);
2862                 }
2863             }
2864         } else if attr.has_name(sym::link_name) {
2865             codegen_fn_attrs.link_name = attr.value_str();
2866         } else if attr.has_name(sym::link_ordinal) {
2867             link_ordinal_span = Some(attr.span);
2868             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2869                 codegen_fn_attrs.link_ordinal = ordinal;
2870             }
2871         } else if attr.has_name(sym::no_sanitize) {
2872             no_sanitize_span = Some(attr.span);
2873             if let Some(list) = attr.meta_item_list() {
2874                 for item in list.iter() {
2875                     if item.has_name(sym::address) {
2876                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2877                     } else if item.has_name(sym::cfi) {
2878                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2879                     } else if item.has_name(sym::memory) {
2880                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2881                     } else if item.has_name(sym::thread) {
2882                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2883                     } else if item.has_name(sym::hwaddress) {
2884                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2885                     } else {
2886                         tcx.sess
2887                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2888                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2889                             .emit();
2890                     }
2891                 }
2892             }
2893         } else if attr.has_name(sym::instruction_set) {
2894             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2895                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2896                     [NestedMetaItem::MetaItem(set)] => {
2897                         let segments =
2898                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2899                         match segments.as_slice() {
2900                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2901                                 if !tcx.sess.target.has_thumb_interworking {
2902                                     struct_span_err!(
2903                                         tcx.sess.diagnostic(),
2904                                         attr.span,
2905                                         E0779,
2906                                         "target does not support `#[instruction_set]`"
2907                                     )
2908                                     .emit();
2909                                     None
2910                                 } else if segments[1] == sym::a32 {
2911                                     Some(InstructionSetAttr::ArmA32)
2912                                 } else if segments[1] == sym::t32 {
2913                                     Some(InstructionSetAttr::ArmT32)
2914                                 } else {
2915                                     unreachable!()
2916                                 }
2917                             }
2918                             _ => {
2919                                 struct_span_err!(
2920                                     tcx.sess.diagnostic(),
2921                                     attr.span,
2922                                     E0779,
2923                                     "invalid instruction set specified",
2924                                 )
2925                                 .emit();
2926                                 None
2927                             }
2928                         }
2929                     }
2930                     [] => {
2931                         struct_span_err!(
2932                             tcx.sess.diagnostic(),
2933                             attr.span,
2934                             E0778,
2935                             "`#[instruction_set]` requires an argument"
2936                         )
2937                         .emit();
2938                         None
2939                     }
2940                     _ => {
2941                         struct_span_err!(
2942                             tcx.sess.diagnostic(),
2943                             attr.span,
2944                             E0779,
2945                             "cannot specify more than one instruction set"
2946                         )
2947                         .emit();
2948                         None
2949                     }
2950                 },
2951                 _ => {
2952                     struct_span_err!(
2953                         tcx.sess.diagnostic(),
2954                         attr.span,
2955                         E0778,
2956                         "must specify an instruction set"
2957                     )
2958                     .emit();
2959                     None
2960                 }
2961             };
2962         } else if attr.has_name(sym::repr) {
2963             codegen_fn_attrs.alignment = match attr.meta_item_list() {
2964                 Some(items) => match items.as_slice() {
2965                     [item] => match item.name_value_literal() {
2966                         Some((sym::align, literal)) => {
2967                             let alignment = rustc_attr::parse_alignment(&literal.kind);
2968
2969                             match alignment {
2970                                 Ok(align) => Some(align),
2971                                 Err(msg) => {
2972                                     struct_span_err!(
2973                                         tcx.sess.diagnostic(),
2974                                         attr.span,
2975                                         E0589,
2976                                         "invalid `repr(align)` attribute: {}",
2977                                         msg
2978                                     )
2979                                     .emit();
2980
2981                                     None
2982                                 }
2983                             }
2984                         }
2985                         _ => None,
2986                     },
2987                     [] => None,
2988                     _ => None,
2989                 },
2990                 None => None,
2991             };
2992         }
2993     }
2994
2995     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2996         if !attr.has_name(sym::inline) {
2997             return ia;
2998         }
2999         match attr.meta().map(|i| i.kind) {
3000             Some(MetaItemKind::Word) => InlineAttr::Hint,
3001             Some(MetaItemKind::List(ref items)) => {
3002                 inline_span = Some(attr.span);
3003                 if items.len() != 1 {
3004                     struct_span_err!(
3005                         tcx.sess.diagnostic(),
3006                         attr.span,
3007                         E0534,
3008                         "expected one argument"
3009                     )
3010                     .emit();
3011                     InlineAttr::None
3012                 } else if list_contains_name(&items, sym::always) {
3013                     InlineAttr::Always
3014                 } else if list_contains_name(&items, sym::never) {
3015                     InlineAttr::Never
3016                 } else {
3017                     struct_span_err!(
3018                         tcx.sess.diagnostic(),
3019                         items[0].span(),
3020                         E0535,
3021                         "invalid argument"
3022                     )
3023                     .emit();
3024
3025                     InlineAttr::None
3026                 }
3027             }
3028             Some(MetaItemKind::NameValue(_)) => ia,
3029             None => ia,
3030         }
3031     });
3032
3033     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3034         if !attr.has_name(sym::optimize) {
3035             return ia;
3036         }
3037         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3038         match attr.meta().map(|i| i.kind) {
3039             Some(MetaItemKind::Word) => {
3040                 err(attr.span, "expected one argument");
3041                 ia
3042             }
3043             Some(MetaItemKind::List(ref items)) => {
3044                 inline_span = Some(attr.span);
3045                 if items.len() != 1 {
3046                     err(attr.span, "expected one argument");
3047                     OptimizeAttr::None
3048                 } else if list_contains_name(&items, sym::size) {
3049                     OptimizeAttr::Size
3050                 } else if list_contains_name(&items, sym::speed) {
3051                     OptimizeAttr::Speed
3052                 } else {
3053                     err(items[0].span(), "invalid argument");
3054                     OptimizeAttr::None
3055                 }
3056             }
3057             Some(MetaItemKind::NameValue(_)) => ia,
3058             None => ia,
3059         }
3060     });
3061
3062     // #73631: closures inherit `#[target_feature]` annotations
3063     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3064         let owner_id = tcx.parent(id).expect("closure should have a parent");
3065         codegen_fn_attrs
3066             .target_features
3067             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3068     }
3069
3070     // If a function uses #[target_feature] it can't be inlined into general
3071     // purpose functions as they wouldn't have the right target features
3072     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3073     // respected.
3074     if !codegen_fn_attrs.target_features.is_empty() {
3075         if codegen_fn_attrs.inline == InlineAttr::Always {
3076             if let Some(span) = inline_span {
3077                 tcx.sess.span_err(
3078                     span,
3079                     "cannot use `#[inline(always)]` with \
3080                      `#[target_feature]`",
3081                 );
3082             }
3083         }
3084     }
3085
3086     if !codegen_fn_attrs.no_sanitize.is_empty() {
3087         if codegen_fn_attrs.inline == InlineAttr::Always {
3088             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3089                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3090                 tcx.struct_span_lint_hir(
3091                     lint::builtin::INLINE_NO_SANITIZE,
3092                     hir_id,
3093                     no_sanitize_span,
3094                     |lint| {
3095                         lint.build("`no_sanitize` will have no effect after inlining")
3096                             .span_note(inline_span, "inlining requested here")
3097                             .emit();
3098                     },
3099                 )
3100             }
3101         }
3102     }
3103
3104     // Weak lang items have the same semantics as "std internal" symbols in the
3105     // sense that they're preserved through all our LTO passes and only
3106     // strippable by the linker.
3107     //
3108     // Additionally weak lang items have predetermined symbol names.
3109     if tcx.is_weak_lang_item(id) {
3110         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3111     }
3112     let check_name = |attr: &Attribute, sym| attr.has_name(sym);
3113     if let Some(name) = weak_lang_items::link_name(check_name, attrs) {
3114         codegen_fn_attrs.export_name = Some(name);
3115         codegen_fn_attrs.link_name = Some(name);
3116     }
3117     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3118
3119     // Internal symbols to the standard library all have no_mangle semantics in
3120     // that they have defined symbol names present in the function name. This
3121     // also applies to weak symbols where they all have known symbol names.
3122     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3123         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3124     }
3125
3126     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3127     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3128     // intrinsic functions.
3129     if let Some(name) = &codegen_fn_attrs.link_name {
3130         if name.as_str().starts_with("llvm.") {
3131             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3132         }
3133     }
3134
3135     codegen_fn_attrs
3136 }
3137
3138 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3139 /// applied to the method prototype.
3140 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3141     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3142         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3143             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3144                 if let Some(trait_item) = tcx
3145                     .associated_items(trait_def_id)
3146                     .filter_by_name_unhygienic(impl_item.ident.name)
3147                     .find(move |trait_item| {
3148                         trait_item.kind == ty::AssocKind::Fn
3149                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3150                     })
3151                 {
3152                     return tcx
3153                         .codegen_fn_attrs(trait_item.def_id)
3154                         .flags
3155                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3156                 }
3157             }
3158         }
3159     }
3160
3161     false
3162 }
3163
3164 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3165     use rustc_ast::{Lit, LitIntType, LitKind};
3166     let meta_item_list = attr.meta_item_list();
3167     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3168     let sole_meta_list = match meta_item_list {
3169         Some([item]) => item.literal(),
3170         Some(_) => {
3171             tcx.sess
3172                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3173                 .note("the attribute requires exactly one argument")
3174                 .emit();
3175             return None;
3176         }
3177         _ => None,
3178     };
3179     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3180         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3181         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3182         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3183         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3184         //
3185         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3186         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3187         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3188         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3189         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3190         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3191         // about LINK.EXE failing.)
3192         if *ordinal <= u16::MAX as u128 {
3193             Some(*ordinal as u16)
3194         } else {
3195             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3196             tcx.sess
3197                 .struct_span_err(attr.span, &msg)
3198                 .note("the value may not exceed `u16::MAX`")
3199                 .emit();
3200             None
3201         }
3202     } else {
3203         tcx.sess
3204             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3205             .note("an unsuffixed integer value, e.g., `1`, is expected")
3206             .emit();
3207         None
3208     }
3209 }
3210
3211 fn check_link_name_xor_ordinal(
3212     tcx: TyCtxt<'_>,
3213     codegen_fn_attrs: &CodegenFnAttrs,
3214     inline_span: Option<Span>,
3215 ) {
3216     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3217         return;
3218     }
3219     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3220     if let Some(span) = inline_span {
3221         tcx.sess.span_err(span, msg);
3222     } else {
3223         tcx.sess.err(msg);
3224     }
3225 }
3226
3227 /// Checks the function annotated with `#[target_feature]` is not a safe
3228 /// trait method implementation, reporting an error if it is.
3229 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3230     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3231     let node = tcx.hir().get(hir_id);
3232     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3233         let parent_id = tcx.hir().get_parent_did(hir_id);
3234         let parent_item = tcx.hir().expect_item(parent_id);
3235         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3236             tcx.sess
3237                 .struct_span_err(
3238                     attr_span,
3239                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3240                 )
3241                 .span_label(attr_span, "cannot be applied to safe trait method")
3242                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3243                 .emit();
3244         }
3245     }
3246 }