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