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, Res};
  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, 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         sugg.push((
 181             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 182             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 183             format!(", {}", type_name),
 184         ));
 185     }
 186
 187     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);
 188
 189     // Suggest, but only if it is not a function in const or static
 190     if suggest {
 191         let mut is_fn = false;
 192         let mut is_const_or_static = false;
 193
 194         if let Some(hir_ty) = hir_ty {
 195             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 196                 is_fn = true;
 197
 198                 // Check if parent is const or static
 199                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 200                 let parent_node = tcx.hir().get(parent_id);
 201
 202                 is_const_or_static = matches!(
 203                     parent_node,
 204                     Node::Item(&hir::Item {
 205                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 206                         ..
 207                     }) | Node::TraitItem(&hir::TraitItem {
 208                         kind: hir::TraitItemKind::Const(..),
 209                         ..
 210                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 211                 );
 212             }
 213         }
 214
 215         // if function is wrapped around a const or static,
 216         // then don't show the suggestion
 217         if !(is_fn && is_const_or_static) {
 218             err.multipart_suggestion(
 219                 "use type parameters instead",
 220                 sugg,
 221                 Applicability::HasPlaceholders,
 222             );
 223         }
 224     }
 225     err.emit();
 226 }
 227
 228 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 229     let (generics, suggest) = match &item.kind {
 230         hir::ItemKind::Union(_, generics)
 231         | hir::ItemKind::Enum(_, generics)
 232         | hir::ItemKind::TraitAlias(generics, _)
 233         | hir::ItemKind::Trait(_, _, generics, ..)
 234         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 235         | hir::ItemKind::Struct(_, generics) => (generics, true),
 236         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 237         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 238         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 239         _ => return,
 240     };
 241
 242     let mut visitor = PlaceholderHirTyCollector::default();
 243     visitor.visit_item(item);
 244
 245     placeholder_type_error(
 246         tcx,
 247         Some(generics.span),
 248         generics.params,
 249         visitor.0,
 250         suggest,
 251         None,
 252         item.kind.descr(),
 253     );
 254 }
 255
 256 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 257     type Map = Map<'tcx>;
 258
 259     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 260         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 261     }
 262
 263     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 264         convert_item(self.tcx, item.item_id());
 265         reject_placeholder_type_signatures_in_item(self.tcx, item);
 266         intravisit::walk_item(self, item);
 267     }
 268
 269     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 270         for param in generics.params {
 271             match param.kind {
 272                 hir::GenericParamKind::Lifetime { .. } => {}
 273                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 274                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 275                     self.tcx.ensure().type_of(def_id);
 276                 }
 277                 hir::GenericParamKind::Type { .. } => {}
 278                 hir::GenericParamKind::Const { default, .. } => {
 279                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 280                     self.tcx.ensure().type_of(def_id);
 281                     if let Some(default) = default {
 282                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 283                         // need to store default and type of default
 284                         self.tcx.ensure().type_of(default_def_id);
 285                         self.tcx.ensure().const_param_default(def_id);
 286                     }
 287                 }
 288             }
 289         }
 290         intravisit::walk_generics(self, generics);
 291     }
 292
 293     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 294         if let hir::ExprKind::Closure(..) = expr.kind {
 295             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 296             self.tcx.ensure().generics_of(def_id);
 297             self.tcx.ensure().type_of(def_id);
 298         }
 299         intravisit::walk_expr(self, expr);
 300     }
 301
 302     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 303         convert_trait_item(self.tcx, trait_item.trait_item_id());
 304         intravisit::walk_trait_item(self, trait_item);
 305     }
 306
 307     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 308         convert_impl_item(self.tcx, impl_item.impl_item_id());
 309         intravisit::walk_impl_item(self, impl_item);
 310     }
 311 }
 312
 313 ///////////////////////////////////////////////////////////////////////////
 314 // Utility types and common code for the above passes.
 315
 316 fn bad_placeholder_type(
 317     tcx: TyCtxt<'tcx>,
 318     mut spans: Vec<Span>,
 319     kind: &'static str,
 320 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 321     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 322
 323     spans.sort();
 324     let mut err = struct_span_err!(
 325         tcx.sess,
 326         spans.clone(),
 327         E0121,
 328         "the type placeholder `_` is not allowed within types on item signatures for {}",
 329         kind
 330     );
 331     for span in spans {
 332         err.span_label(span, "not allowed in type signatures");
 333     }
 334     err
 335 }
 336
 337 impl ItemCtxt<'tcx> {
 338     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 339         ItemCtxt { tcx, item_def_id }
 340     }
 341
 342     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 343         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 344     }
 345
 346     pub fn hir_id(&self) -> hir::HirId {
 347         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 348     }
 349
 350     pub fn node(&self) -> hir::Node<'tcx> {
 351         self.tcx.hir().get(self.hir_id())
 352     }
 353 }
 354
 355 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 356     fn tcx(&self) -> TyCtxt<'tcx> {
 357         self.tcx
 358     }
 359
 360     fn item_def_id(&self) -> Option<DefId> {
 361         Some(self.item_def_id)
 362     }
 363
 364     fn get_type_parameter_bounds(
 365         &self,
 366         span: Span,
 367         def_id: DefId,
 368         assoc_name: Ident,
 369     ) -> ty::GenericPredicates<'tcx> {
 370         self.tcx.at(span).type_param_predicates((
 371             self.item_def_id,
 372             def_id.expect_local(),
 373             assoc_name,
 374         ))
 375     }
 376
 377     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 378         None
 379     }
 380
 381     fn allow_ty_infer(&self) -> bool {
 382         false
 383     }
 384
 385     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 386         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 387     }
 388
 389     fn ct_infer(
 390         &self,
 391         ty: Ty<'tcx>,
 392         _: Option<&ty::GenericParamDef>,
 393         span: Span,
 394     ) -> &'tcx Const<'tcx> {
 395         bad_placeholder_type(self.tcx(), vec![span], "generic").emit();
 396         // Typeck doesn't expect erased regions to be returned from `type_of`.
 397         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 398             ty::ReErased => self.tcx.lifetimes.re_static,
 399             _ => r,
 400         });
 401         self.tcx().const_error(ty)
 402     }
 403
 404     fn projected_ty_from_poly_trait_ref(
 405         &self,
 406         span: Span,
 407         item_def_id: DefId,
 408         item_segment: &hir::PathSegment<'_>,
 409         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 410     ) -> Ty<'tcx> {
 411         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 412             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 413                 self,
 414                 self.tcx,
 415                 span,
 416                 item_def_id,
 417                 item_segment,
 418                 trait_ref.substs,
 419             );
 420             self.tcx().mk_projection(item_def_id, item_substs)
 421         } else {
 422             // There are no late-bound regions; we can just ignore the binder.
 423             let mut err = struct_span_err!(
 424                 self.tcx().sess,
 425                 span,
 426                 E0212,
 427                 "cannot use the associated type of a trait \
 428                  with uninferred generic parameters"
 429             );
 430
 431             match self.node() {
 432                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 433                     let item =
 434                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 435                     match &item.kind {
 436                         hir::ItemKind::Enum(_, generics)
 437                         | hir::ItemKind::Struct(_, generics)
 438                         | hir::ItemKind::Union(_, generics) => {
 439                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 440                             let (lt_sp, sugg) = match generics.params {
 441                                 [] => (generics.span, format!("<{}>", lt_name)),
 442                                 [bound, ..] => {
 443                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 444                                 }
 445                             };
 446                             let suggestions = vec![
 447                                 (lt_sp, sugg),
 448                                 (
 449                                     span.with_hi(item_segment.ident.span.lo()),
 450                                     format!(
 451                                         "{}::",
 452                                         // Replace the existing lifetimes with a new named lifetime.
 453                                         self.tcx
 454                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 455                                                 self.tcx.mk_region(ty::ReEarlyBound(
 456                                                     ty::EarlyBoundRegion {
 457                                                         def_id: item_def_id,
 458                                                         index: 0,
 459                                                         name: Symbol::intern(&lt_name),
 460                                                     },
 461                                                 ))
 462                                             })
 463                                             .0,
 464                                     ),
 465                                 ),
 466                             ];
 467                             err.multipart_suggestion(
 468                                 "use a fully qualified path with explicit lifetimes",
 469                                 suggestions,
 470                                 Applicability::MaybeIncorrect,
 471                             );
 472                         }
 473                         _ => {}
 474                     }
 475                 }
 476                 hir::Node::Item(hir::Item {
 477                     kind:
 478                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 479                     ..
 480                 }) => {}
 481                 hir::Node::Item(_)
 482                 | hir::Node::ForeignItem(_)
 483                 | hir::Node::TraitItem(_)
 484                 | hir::Node::ImplItem(_) => {
 485                     err.span_suggestion_verbose(
 486                         span.with_hi(item_segment.ident.span.lo()),
 487                         "use a fully qualified path with inferred lifetimes",
 488                         format!(
 489                             "{}::",
 490                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 491                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 492                         ),
 493                         Applicability::MaybeIncorrect,
 494                     );
 495                 }
 496                 _ => {}
 497             }
 498             err.emit();
 499             self.tcx().ty_error()
 500         }
 501     }
 502
 503     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 504         // Types in item signatures are not normalized to avoid undue dependencies.
 505         ty
 506     }
 507
 508     fn set_tainted_by_errors(&self) {
 509         // There's no obvious place to track this, so just let it go.
 510     }
 511
 512     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 513         // There's no place to record types from signatures?
 514     }
 515 }
 516
 517 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 518 fn get_new_lifetime_name<'tcx>(
 519     tcx: TyCtxt<'tcx>,
 520     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 521     generics: &hir::Generics<'tcx>,
 522 ) -> String {
 523     let existing_lifetimes = tcx
 524         .collect_referenced_late_bound_regions(&poly_trait_ref)
 525         .into_iter()
 526         .filter_map(|lt| {
 527             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 528                 Some(name.as_str().to_string())
 529             } else {
 530                 None
 531             }
 532         })
 533         .chain(generics.params.iter().filter_map(|param| {
 534             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 535                 Some(param.name.ident().as_str().to_string())
 536             } else {
 537                 None
 538             }
 539         }))
 540         .collect::<FxHashSet<String>>();
 541
 542     let a_to_z_repeat_n = |n| {
 543         (b'a'..=b'z').map(move |c| {
 544             let mut s = '\''.to_string();
 545             s.extend(std::iter::repeat(char::from(c)).take(n));
 546             s
 547         })
 548     };
 549
 550     // If all single char lifetime names are present, we wrap around and double the chars.
 551     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 552 }
 553
 554 /// Returns the predicates defined on `item_def_id` of the form
 555 /// `X: Foo` where `X` is the type parameter `def_id`.
 556 fn type_param_predicates(
 557     tcx: TyCtxt<'_>,
 558     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 559 ) -> ty::GenericPredicates<'_> {
 560     use rustc_hir::*;
 561
 562     // In the AST, bounds can derive from two places. Either
 563     // written inline like `<T: Foo>` or in a where-clause like
 564     // `where T: Foo`.
 565
 566     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 567     let param_owner = tcx.hir().ty_param_owner(param_id);
 568     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 569     let generics = tcx.generics_of(param_owner_def_id);
 570     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 571     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 572
 573     // Don't look for bounds where the type parameter isn't in scope.
 574     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 575         None
 576     } else {
 577         tcx.generics_of(item_def_id).parent
 578     };
 579
 580     let mut result = parent
 581         .map(|parent| {
 582             let icx = ItemCtxt::new(tcx, parent);
 583             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 584         })
 585         .unwrap_or_default();
 586     let mut extend = None;
 587
 588     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 589     let ast_generics = match tcx.hir().get(item_hir_id) {
 590         Node::TraitItem(item) => &item.generics,
 591
 592         Node::ImplItem(item) => &item.generics,
 593
 594         Node::Item(item) => {
 595             match item.kind {
 596                 ItemKind::Fn(.., ref generics, _)
 597                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 598                 | ItemKind::TyAlias(_, ref generics)
 599                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 600                 | ItemKind::Enum(_, ref generics)
 601                 | ItemKind::Struct(_, ref generics)
 602                 | ItemKind::Union(_, ref generics) => generics,
 603                 ItemKind::Trait(_, _, ref generics, ..) => {
 604                     // Implied `Self: Trait` and supertrait bounds.
 605                     if param_id == item_hir_id {
 606                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 607                         extend =
 608                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 609                     }
 610                     generics
 611                 }
 612                 _ => return result,
 613             }
 614         }
 615
 616         Node::ForeignItem(item) => match item.kind {
 617             ForeignItemKind::Fn(_, _, ref generics) => generics,
 618             _ => return result,
 619         },
 620
 621         _ => return result,
 622     };
 623
 624     let icx = ItemCtxt::new(tcx, item_def_id);
 625     let extra_predicates = extend.into_iter().chain(
 626         icx.type_parameter_bounds_in_generics(
 627             ast_generics,
 628             param_id,
 629             ty,
 630             OnlySelfBounds(true),
 631             Some(assoc_name),
 632         )
 633         .into_iter()
 634         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 635             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 636             _ => false,
 637         }),
 638     );
 639     result.predicates =
 640         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 641     result
 642 }
 643
 644 impl ItemCtxt<'tcx> {
 645     /// Finds bounds from `hir::Generics`. This requires scanning through the
 646     /// AST. We do this to avoid having to convert *all* the bounds, which
 647     /// would create artificial cycles. Instead, we can only convert the
 648     /// bounds for a type parameter `X` if `X::Foo` is used.
 649     fn type_parameter_bounds_in_generics(
 650         &self,
 651         ast_generics: &'tcx hir::Generics<'tcx>,
 652         param_id: hir::HirId,
 653         ty: Ty<'tcx>,
 654         only_self_bounds: OnlySelfBounds,
 655         assoc_name: Option<Ident>,
 656     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 657         let from_ty_params = ast_generics
 658             .params
 659             .iter()
 660             .filter_map(|param| match param.kind {
 661                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 662                 _ => None,
 663             })
 664             .flat_map(|bounds| bounds.iter())
 665             .filter(|b| match assoc_name {
 666                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 667                 None => true,
 668             })
 669             .flat_map(|b| predicates_from_bound(self, ty, b));
 670
 671         let from_where_clauses = ast_generics
 672             .where_clause
 673             .predicates
 674             .iter()
 675             .filter_map(|wp| match *wp {
 676                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 677                 _ => None,
 678             })
 679             .flat_map(|bp| {
 680                 let bt = if is_param(self.tcx, bp.bounded_ty, param_id) {
 681                     Some(ty)
 682                 } else if !only_self_bounds.0 {
 683                     Some(self.to_ty(bp.bounded_ty))
 684                 } else {
 685                     None
 686                 };
 687                 bp.bounds
 688                     .iter()
 689                     .filter(|b| match assoc_name {
 690                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 691                         None => true,
 692                     })
 693                     .filter_map(move |b| bt.map(|bt| (bt, b)))
 694             })
 695             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
 696
 697         from_ty_params.chain(from_where_clauses).collect()
 698     }
 699
 700     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 701         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 702
 703         match b {
 704             hir::GenericBound::Trait(poly_trait_ref, _) => {
 705                 let trait_ref = &poly_trait_ref.trait_ref;
 706                 if let Some(trait_did) = trait_ref.trait_def_id() {
 707                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 708                 } else {
 709                     false
 710                 }
 711             }
 712             _ => false,
 713         }
 714     }
 715 }
 716
 717 /// Tests whether this is the AST for a reference to the type
 718 /// parameter with ID `param_id`. We use this so as to avoid running
 719 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 720 /// conversion of the type to avoid inducing unnecessary cycles.
 721 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 722     if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = ast_ty.kind {
 723         match path.res {
 724             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 725                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 726             }
 727             _ => false,
 728         }
 729     } else {
 730         false
 731     }
 732 }
 733
 734 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 735     let it = tcx.hir().item(item_id);
 736     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 737     let def_id = item_id.def_id;
 738
 739     match it.kind {
 740         // These don't define types.
 741         hir::ItemKind::ExternCrate(_)
 742         | hir::ItemKind::Use(..)
 743         | hir::ItemKind::Macro(_)
 744         | hir::ItemKind::Mod(_)
 745         | hir::ItemKind::GlobalAsm(_) => {}
 746         hir::ItemKind::ForeignMod { items, .. } => {
 747             for item in items {
 748                 let item = tcx.hir().foreign_item(item.id);
 749                 tcx.ensure().generics_of(item.def_id);
 750                 tcx.ensure().type_of(item.def_id);
 751                 tcx.ensure().predicates_of(item.def_id);
 752                 match item.kind {
 753                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 754                     hir::ForeignItemKind::Static(..) => {
 755                         let mut visitor = PlaceholderHirTyCollector::default();
 756                         visitor.visit_foreign_item(item);
 757                         placeholder_type_error(
 758                             tcx,
 759                             None,
 760                             &[],
 761                             visitor.0,
 762                             false,
 763                             None,
 764                             "static variable",
 765                         );
 766                     }
 767                     _ => (),
 768                 }
 769             }
 770         }
 771         hir::ItemKind::Enum(ref enum_definition, _) => {
 772             tcx.ensure().generics_of(def_id);
 773             tcx.ensure().type_of(def_id);
 774             tcx.ensure().predicates_of(def_id);
 775             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 776         }
 777         hir::ItemKind::Impl { .. } => {
 778             tcx.ensure().generics_of(def_id);
 779             tcx.ensure().type_of(def_id);
 780             tcx.ensure().impl_trait_ref(def_id);
 781             tcx.ensure().predicates_of(def_id);
 782         }
 783         hir::ItemKind::Trait(..) => {
 784             tcx.ensure().generics_of(def_id);
 785             tcx.ensure().trait_def(def_id);
 786             tcx.at(it.span).super_predicates_of(def_id);
 787             tcx.ensure().predicates_of(def_id);
 788         }
 789         hir::ItemKind::TraitAlias(..) => {
 790             tcx.ensure().generics_of(def_id);
 791             tcx.at(it.span).super_predicates_of(def_id);
 792             tcx.ensure().predicates_of(def_id);
 793         }
 794         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 795             tcx.ensure().generics_of(def_id);
 796             tcx.ensure().type_of(def_id);
 797             tcx.ensure().predicates_of(def_id);
 798
 799             for f in struct_def.fields() {
 800                 let def_id = tcx.hir().local_def_id(f.hir_id);
 801                 tcx.ensure().generics_of(def_id);
 802                 tcx.ensure().type_of(def_id);
 803                 tcx.ensure().predicates_of(def_id);
 804             }
 805
 806             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 807                 convert_variant_ctor(tcx, ctor_hir_id);
 808             }
 809         }
 810
 811         // Desugared from `impl Trait`, so visited by the function's return type.
 812         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 813
 814         // Don't call `type_of` on opaque types, since that depends on type
 815         // checking function bodies. `check_item_type` ensures that it's called
 816         // instead.
 817         hir::ItemKind::OpaqueTy(..) => {
 818             tcx.ensure().generics_of(def_id);
 819             tcx.ensure().predicates_of(def_id);
 820             tcx.ensure().explicit_item_bounds(def_id);
 821         }
 822         hir::ItemKind::TyAlias(..)
 823         | hir::ItemKind::Static(..)
 824         | hir::ItemKind::Const(..)
 825         | hir::ItemKind::Fn(..) => {
 826             tcx.ensure().generics_of(def_id);
 827             tcx.ensure().type_of(def_id);
 828             tcx.ensure().predicates_of(def_id);
 829             match it.kind {
 830                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 831                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 832                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 833                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 834                     if let hir::TyKind::TraitObject(..) = ty.kind {
 835                         let mut visitor = PlaceholderHirTyCollector::default();
 836                         visitor.visit_item(it);
 837                         placeholder_type_error(
 838                             tcx,
 839                             None,
 840                             &[],
 841                             visitor.0,
 842                             false,
 843                             None,
 844                             it.kind.descr(),
 845                         );
 846                     }
 847                 }
 848                 _ => (),
 849             }
 850         }
 851     }
 852 }
 853
 854 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 855     let trait_item = tcx.hir().trait_item(trait_item_id);
 856     tcx.ensure().generics_of(trait_item_id.def_id);
 857
 858     match trait_item.kind {
 859         hir::TraitItemKind::Fn(..) => {
 860             tcx.ensure().type_of(trait_item_id.def_id);
 861             tcx.ensure().fn_sig(trait_item_id.def_id);
 862         }
 863
 864         hir::TraitItemKind::Const(.., Some(_)) => {
 865             tcx.ensure().type_of(trait_item_id.def_id);
 866         }
 867
 868         hir::TraitItemKind::Const(..) => {
 869             tcx.ensure().type_of(trait_item_id.def_id);
 870             // Account for `const C: _;`.
 871             let mut visitor = PlaceholderHirTyCollector::default();
 872             visitor.visit_trait_item(trait_item);
 873             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 874         }
 875
 876         hir::TraitItemKind::Type(_, Some(_)) => {
 877             tcx.ensure().item_bounds(trait_item_id.def_id);
 878             tcx.ensure().type_of(trait_item_id.def_id);
 879             // Account for `type T = _;`.
 880             let mut visitor = PlaceholderHirTyCollector::default();
 881             visitor.visit_trait_item(trait_item);
 882             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 883         }
 884
 885         hir::TraitItemKind::Type(_, None) => {
 886             tcx.ensure().item_bounds(trait_item_id.def_id);
 887             // #74612: Visit and try to find bad placeholders
 888             // even if there is no concrete type.
 889             let mut visitor = PlaceholderHirTyCollector::default();
 890             visitor.visit_trait_item(trait_item);
 891
 892             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 893         }
 894     };
 895
 896     tcx.ensure().predicates_of(trait_item_id.def_id);
 897 }
 898
 899 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 900     let def_id = impl_item_id.def_id;
 901     tcx.ensure().generics_of(def_id);
 902     tcx.ensure().type_of(def_id);
 903     tcx.ensure().predicates_of(def_id);
 904     let impl_item = tcx.hir().impl_item(impl_item_id);
 905     match impl_item.kind {
 906         hir::ImplItemKind::Fn(..) => {
 907             tcx.ensure().fn_sig(def_id);
 908         }
 909         hir::ImplItemKind::TyAlias(_) => {
 910             // Account for `type T = _;`
 911             let mut visitor = PlaceholderHirTyCollector::default();
 912             visitor.visit_impl_item(impl_item);
 913
 914             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 915         }
 916         hir::ImplItemKind::Const(..) => {}
 917     }
 918 }
 919
 920 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 921     let def_id = tcx.hir().local_def_id(ctor_id);
 922     tcx.ensure().generics_of(def_id);
 923     tcx.ensure().type_of(def_id);
 924     tcx.ensure().predicates_of(def_id);
 925 }
 926
 927 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 928     let def = tcx.adt_def(def_id);
 929     let repr_type = def.repr.discr_type();
 930     let initial = repr_type.initial_discriminant(tcx);
 931     let mut prev_discr = None::<Discr<'_>>;
 932
 933     // fill the discriminant values and field types
 934     for variant in variants {
 935         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 936         prev_discr = Some(
 937             if let Some(ref e) = variant.disr_expr {
 938                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 939                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 940             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 941                 Some(discr)
 942             } else {
 943                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 944                     .span_label(
 945                         variant.span,
 946                         format!("overflowed on value after {}", prev_discr.unwrap()),
 947                     )
 948                     .note(&format!(
 949                         "explicitly set `{} = {}` if that is desired outcome",
 950                         variant.ident, wrapped_discr
 951                     ))
 952                     .emit();
 953                 None
 954             }
 955             .unwrap_or(wrapped_discr),
 956         );
 957
 958         for f in variant.data.fields() {
 959             let def_id = tcx.hir().local_def_id(f.hir_id);
 960             tcx.ensure().generics_of(def_id);
 961             tcx.ensure().type_of(def_id);
 962             tcx.ensure().predicates_of(def_id);
 963         }
 964
 965         // Convert the ctor, if any. This also registers the variant as
 966         // an item.
 967         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 968             convert_variant_ctor(tcx, ctor_hir_id);
 969         }
 970     }
 971 }
 972
 973 fn convert_variant(
 974     tcx: TyCtxt<'_>,
 975     variant_did: Option<LocalDefId>,
 976     ctor_did: Option<LocalDefId>,
 977     ident: Ident,
 978     discr: ty::VariantDiscr,
 979     def: &hir::VariantData<'_>,
 980     adt_kind: ty::AdtKind,
 981     parent_did: LocalDefId,
 982 ) -> ty::VariantDef {
 983     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 984     let fields = def
 985         .fields()
 986         .iter()
 987         .map(|f| {
 988             let fid = tcx.hir().local_def_id(f.hir_id);
 989             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 990             if let Some(prev_span) = dup_span {
 991                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 992                     field_name: f.ident,
 993                     span: f.span,
 994                     prev_span,
 995                 });
 996             } else {
 997                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 998             }
 999
1000             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
1001         })
1002         .collect();
1003     let recovered = match def {
1004         hir::VariantData::Struct(_, r) => *r,
1005         _ => false,
1006     };
1007     ty::VariantDef::new(
1008         ident,
1009         variant_did.map(LocalDefId::to_def_id),
1010         ctor_did.map(LocalDefId::to_def_id),
1011         discr,
1012         fields,
1013         CtorKind::from_hir(def),
1014         adt_kind,
1015         parent_did.to_def_id(),
1016         recovered,
1017         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1018             || variant_did.map_or(false, |variant_did| {
1019                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1020             }),
1021     )
1022 }
1023
1024 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1025     use rustc_hir::*;
1026
1027     let def_id = def_id.expect_local();
1028     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1029     let item = match tcx.hir().get(hir_id) {
1030         Node::Item(item) => item,
1031         _ => bug!(),
1032     };
1033
1034     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1035     let (kind, variants) = match item.kind {
1036         ItemKind::Enum(ref def, _) => {
1037             let mut distance_from_explicit = 0;
1038             let variants = def
1039                 .variants
1040                 .iter()
1041                 .map(|v| {
1042                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1043                     let ctor_did =
1044                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1045
1046                     let discr = if let Some(ref e) = v.disr_expr {
1047                         distance_from_explicit = 0;
1048                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1049                     } else {
1050                         ty::VariantDiscr::Relative(distance_from_explicit)
1051                     };
1052                     distance_from_explicit += 1;
1053
1054                     convert_variant(
1055                         tcx,
1056                         variant_did,
1057                         ctor_did,
1058                         v.ident,
1059                         discr,
1060                         &v.data,
1061                         AdtKind::Enum,
1062                         def_id,
1063                     )
1064                 })
1065                 .collect();
1066
1067             (AdtKind::Enum, variants)
1068         }
1069         ItemKind::Struct(ref def, _) => {
1070             let variant_did = None::<LocalDefId>;
1071             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1072
1073             let variants = std::iter::once(convert_variant(
1074                 tcx,
1075                 variant_did,
1076                 ctor_did,
1077                 item.ident,
1078                 ty::VariantDiscr::Relative(0),
1079                 def,
1080                 AdtKind::Struct,
1081                 def_id,
1082             ))
1083             .collect();
1084
1085             (AdtKind::Struct, variants)
1086         }
1087         ItemKind::Union(ref def, _) => {
1088             let variant_did = None;
1089             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1090
1091             let variants = std::iter::once(convert_variant(
1092                 tcx,
1093                 variant_did,
1094                 ctor_did,
1095                 item.ident,
1096                 ty::VariantDiscr::Relative(0),
1097                 def,
1098                 AdtKind::Union,
1099                 def_id,
1100             ))
1101             .collect();
1102
1103             (AdtKind::Union, variants)
1104         }
1105         _ => bug!(),
1106     };
1107     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1108 }
1109
1110 /// Ensures that the super-predicates of the trait with a `DefId`
1111 /// of `trait_def_id` are converted and stored. This also ensures that
1112 /// the transitive super-predicates are converted.
1113 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1114     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1115     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1116 }
1117
1118 /// Ensures that the super-predicates of the trait with a `DefId`
1119 /// of `trait_def_id` are converted and stored. This also ensures that
1120 /// the transitive super-predicates are converted.
1121 fn super_predicates_that_define_assoc_type(
1122     tcx: TyCtxt<'_>,
1123     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1124 ) -> ty::GenericPredicates<'_> {
1125     debug!(
1126         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1127         trait_def_id, assoc_name
1128     );
1129     if trait_def_id.is_local() {
1130         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1131         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1132
1133         let item = match tcx.hir().get(trait_hir_id) {
1134             Node::Item(item) => item,
1135             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1136         };
1137
1138         let (generics, bounds) = match item.kind {
1139             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1140             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1141             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1142         };
1143
1144         let icx = ItemCtxt::new(tcx, trait_def_id);
1145
1146         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1147         let self_param_ty = tcx.types.self_param;
1148         let superbounds1 = if let Some(assoc_name) = assoc_name {
1149             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1150                 &icx,
1151                 self_param_ty,
1152                 bounds,
1153                 assoc_name,
1154             )
1155         } else {
1156             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1157         };
1158
1159         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1160
1161         // Convert any explicit superbounds in the where-clause,
1162         // e.g., `trait Foo where Self: Bar`.
1163         // In the case of trait aliases, however, we include all bounds in the where-clause,
1164         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1165         // as one of its "superpredicates".
1166         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1167         let superbounds2 = icx.type_parameter_bounds_in_generics(
1168             generics,
1169             item.hir_id(),
1170             self_param_ty,
1171             OnlySelfBounds(!is_trait_alias),
1172             assoc_name,
1173         );
1174
1175         // Combine the two lists to form the complete set of superbounds:
1176         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1177
1178         // Now require that immediate supertraits are converted,
1179         // which will, in turn, reach indirect supertraits.
1180         if assoc_name.is_none() {
1181             // Now require that immediate supertraits are converted,
1182             // which will, in turn, reach indirect supertraits.
1183             for &(pred, span) in superbounds {
1184                 debug!("superbound: {:?}", pred);
1185                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1186                     tcx.at(span).super_predicates_of(bound.def_id());
1187                 }
1188             }
1189         }
1190
1191         ty::GenericPredicates { parent: None, predicates: superbounds }
1192     } else {
1193         // if `assoc_name` is None, then the query should've been redirected to an
1194         // external provider
1195         assert!(assoc_name.is_some());
1196         tcx.super_predicates_of(trait_def_id)
1197     }
1198 }
1199
1200 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1201     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1202     let item = tcx.hir().expect_item(hir_id);
1203
1204     let (is_auto, unsafety) = match item.kind {
1205         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1206         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1207         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1208     };
1209
1210     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1211     if paren_sugar && !tcx.features().unboxed_closures {
1212         tcx.sess
1213             .struct_span_err(
1214                 item.span,
1215                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1216                  which traits can use parenthetical notation",
1217             )
1218             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1219             .emit();
1220     }
1221
1222     let is_marker = tcx.has_attr(def_id, sym::marker);
1223     let skip_array_during_method_dispatch =
1224         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1225     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1226         ty::trait_def::TraitSpecializationKind::Marker
1227     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1228         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1229     } else {
1230         ty::trait_def::TraitSpecializationKind::None
1231     };
1232     let def_path_hash = tcx.def_path_hash(def_id);
1233     ty::TraitDef::new(
1234         def_id,
1235         unsafety,
1236         paren_sugar,
1237         is_auto,
1238         is_marker,
1239         skip_array_during_method_dispatch,
1240         spec_kind,
1241         def_path_hash,
1242     )
1243 }
1244
1245 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1246     struct LateBoundRegionsDetector<'tcx> {
1247         tcx: TyCtxt<'tcx>,
1248         outer_index: ty::DebruijnIndex,
1249         has_late_bound_regions: Option<Span>,
1250     }
1251
1252     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1253         type Map = intravisit::ErasedMap<'tcx>;
1254
1255         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1256             NestedVisitorMap::None
1257         }
1258
1259         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1260             if self.has_late_bound_regions.is_some() {
1261                 return;
1262             }
1263             match ty.kind {
1264                 hir::TyKind::BareFn(..) => {
1265                     self.outer_index.shift_in(1);
1266                     intravisit::walk_ty(self, ty);
1267                     self.outer_index.shift_out(1);
1268                 }
1269                 _ => intravisit::walk_ty(self, ty),
1270             }
1271         }
1272
1273         fn visit_poly_trait_ref(
1274             &mut self,
1275             tr: &'tcx hir::PolyTraitRef<'tcx>,
1276             m: hir::TraitBoundModifier,
1277         ) {
1278             if self.has_late_bound_regions.is_some() {
1279                 return;
1280             }
1281             self.outer_index.shift_in(1);
1282             intravisit::walk_poly_trait_ref(self, tr, m);
1283             self.outer_index.shift_out(1);
1284         }
1285
1286         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1287             if self.has_late_bound_regions.is_some() {
1288                 return;
1289             }
1290
1291             match self.tcx.named_region(lt.hir_id) {
1292                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1293                 Some(
1294                     rl::Region::LateBound(debruijn, _, _, _)
1295                     | rl::Region::LateBoundAnon(debruijn, _, _),
1296                 ) if debruijn < self.outer_index => {}
1297                 Some(
1298                     rl::Region::LateBound(..)
1299                     | rl::Region::LateBoundAnon(..)
1300                     | rl::Region::Free(..),
1301                 )
1302                 | None => {
1303                     self.has_late_bound_regions = Some(lt.span);
1304                 }
1305             }
1306         }
1307     }
1308
1309     fn has_late_bound_regions<'tcx>(
1310         tcx: TyCtxt<'tcx>,
1311         generics: &'tcx hir::Generics<'tcx>,
1312         decl: &'tcx hir::FnDecl<'tcx>,
1313     ) -> Option<Span> {
1314         let mut visitor = LateBoundRegionsDetector {
1315             tcx,
1316             outer_index: ty::INNERMOST,
1317             has_late_bound_regions: None,
1318         };
1319         for param in generics.params {
1320             if let GenericParamKind::Lifetime { .. } = param.kind {
1321                 if tcx.is_late_bound(param.hir_id) {
1322                     return Some(param.span);
1323                 }
1324             }
1325         }
1326         visitor.visit_fn_decl(decl);
1327         visitor.has_late_bound_regions
1328     }
1329
1330     match node {
1331         Node::TraitItem(item) => match item.kind {
1332             hir::TraitItemKind::Fn(ref sig, _) => {
1333                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1334             }
1335             _ => None,
1336         },
1337         Node::ImplItem(item) => match item.kind {
1338             hir::ImplItemKind::Fn(ref sig, _) => {
1339                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1340             }
1341             _ => None,
1342         },
1343         Node::ForeignItem(item) => match item.kind {
1344             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1345                 has_late_bound_regions(tcx, generics, fn_decl)
1346             }
1347             _ => None,
1348         },
1349         Node::Item(item) => match item.kind {
1350             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1351                 has_late_bound_regions(tcx, generics, sig.decl)
1352             }
1353             _ => None,
1354         },
1355         _ => None,
1356     }
1357 }
1358
1359 struct AnonConstInParamTyDetector {
1360     in_param_ty: bool,
1361     found_anon_const_in_param_ty: bool,
1362     ct: HirId,
1363 }
1364
1365 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1366     type Map = intravisit::ErasedMap<'v>;
1367
1368     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1369         NestedVisitorMap::None
1370     }
1371
1372     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1373         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1374             let prev = self.in_param_ty;
1375             self.in_param_ty = true;
1376             self.visit_ty(ty);
1377             self.in_param_ty = prev;
1378         }
1379     }
1380
1381     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1382         if self.in_param_ty && self.ct == c.hir_id {
1383             self.found_anon_const_in_param_ty = true;
1384         } else {
1385             intravisit::walk_anon_const(self, c)
1386         }
1387     }
1388 }
1389
1390 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1391     use rustc_hir::*;
1392
1393     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1394
1395     let node = tcx.hir().get(hir_id);
1396     let parent_def_id = match node {
1397         Node::ImplItem(_)
1398         | Node::TraitItem(_)
1399         | Node::Variant(_)
1400         | Node::Ctor(..)
1401         | Node::Field(_) => {
1402             let parent_id = tcx.hir().get_parent_item(hir_id);
1403             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1404         }
1405         // FIXME(#43408) always enable this once `lazy_normalization` is
1406         // stable enough and does not need a feature gate anymore.
1407         Node::AnonConst(_) => {
1408             let parent_id = tcx.hir().get_parent_item(hir_id);
1409             let parent_def_id = tcx.hir().local_def_id(parent_id);
1410
1411             let mut in_param_ty = false;
1412             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1413                 if let Some(generics) = node.generics() {
1414                     let mut visitor = AnonConstInParamTyDetector {
1415                         in_param_ty: false,
1416                         found_anon_const_in_param_ty: false,
1417                         ct: hir_id,
1418                     };
1419
1420                     visitor.visit_generics(generics);
1421                     in_param_ty = visitor.found_anon_const_in_param_ty;
1422                     break;
1423                 }
1424             }
1425
1426             if in_param_ty {
1427                 // We do not allow generic parameters in anon consts if we are inside
1428                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1429                 None
1430             } else if tcx.lazy_normalization() {
1431                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1432                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1433                     //
1434                     // struct Foo<const N: usize = { .. }>;
1435                     //        ^^^       ^          ^^^^^^ def id of this anon const
1436                     //        ^         ^ param_id
1437                     //        ^ parent_def_id
1438                     //
1439                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1440                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1441                     //
1442                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1443                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1444                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1445                     //
1446                     // We fix this by having this function return the parent's generics ourselves and truncating the
1447                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1448                     //
1449                     // For the above code example that means we want `substs: []`
1450                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1451                     // the def id of the `{ N + 1 }` anon const
1452                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1453                     //
1454                     // This has some implications for how we get the predicates available to the anon const
1455                     // see `explicit_predicates_of` for more information on this
1456                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1457                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1458                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1459                     // In the above example this would be .params[..N#0]
1460                     let params = generics.params[..param_def_idx as usize].to_owned();
1461                     let param_def_id_to_index =
1462                         params.iter().map(|param| (param.def_id, param.index)).collect();
1463
1464                     return ty::Generics {
1465                         // we set the parent of these generics to be our parent's parent so that we
1466                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1467                         // struct Foo<const N: usize, const M: usize = { ... }>;
1468                         parent: generics.parent,
1469                         parent_count: generics.parent_count,
1470                         params,
1471                         param_def_id_to_index,
1472                         has_self: generics.has_self,
1473                         has_late_bound_regions: generics.has_late_bound_regions,
1474                     };
1475                 }
1476
1477                 // HACK(eddyb) this provides the correct generics when
1478                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1479                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1480                 //
1481                 // Note that we do not supply the parent generics when using
1482                 // `min_const_generics`.
1483                 Some(parent_def_id.to_def_id())
1484             } else {
1485                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1486                 match parent_node {
1487                     // HACK(eddyb) this provides the correct generics for repeat
1488                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1489                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1490                     // as they shouldn't be able to cause query cycle errors.
1491                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1492                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1493                         if constant.hir_id == hir_id =>
1494                     {
1495                         Some(parent_def_id.to_def_id())
1496                     }
1497
1498                     _ => None,
1499                 }
1500             }
1501         }
1502         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1503             Some(tcx.closure_base_def_id(def_id))
1504         }
1505         Node::Item(item) => match item.kind {
1506             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1507                 impl_trait_fn.or_else(|| {
1508                     let parent_id = tcx.hir().get_parent_item(hir_id);
1509                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1510                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1511                     // Opaque types are always nested within another item, and
1512                     // inherit the generics of the item.
1513                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1514                 })
1515             }
1516             _ => None,
1517         },
1518         _ => None,
1519     };
1520
1521     let mut opt_self = None;
1522     let mut allow_defaults = false;
1523
1524     let no_generics = hir::Generics::empty();
1525     let ast_generics = match node {
1526         Node::TraitItem(item) => &item.generics,
1527
1528         Node::ImplItem(item) => &item.generics,
1529
1530         Node::Item(item) => {
1531             match item.kind {
1532                 ItemKind::Fn(.., ref generics, _)
1533                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1534
1535                 ItemKind::TyAlias(_, ref generics)
1536                 | ItemKind::Enum(_, ref generics)
1537                 | ItemKind::Struct(_, ref generics)
1538                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1539                 | ItemKind::Union(_, ref generics) => {
1540                     allow_defaults = true;
1541                     generics
1542                 }
1543
1544                 ItemKind::Trait(_, _, ref generics, ..)
1545                 | ItemKind::TraitAlias(ref generics, ..) => {
1546                     // Add in the self type parameter.
1547                     //
1548                     // Something of a hack: use the node id for the trait, also as
1549                     // the node id for the Self type parameter.
1550                     let param_id = item.def_id;
1551
1552                     opt_self = Some(ty::GenericParamDef {
1553                         index: 0,
1554                         name: kw::SelfUpper,
1555                         def_id: param_id.to_def_id(),
1556                         pure_wrt_drop: false,
1557                         kind: ty::GenericParamDefKind::Type {
1558                             has_default: false,
1559                             object_lifetime_default: rl::Set1::Empty,
1560                             synthetic: None,
1561                         },
1562                     });
1563
1564                     allow_defaults = true;
1565                     generics
1566                 }
1567
1568                 _ => &no_generics,
1569             }
1570         }
1571
1572         Node::ForeignItem(item) => match item.kind {
1573             ForeignItemKind::Static(..) => &no_generics,
1574             ForeignItemKind::Fn(_, _, ref generics) => generics,
1575             ForeignItemKind::Type => &no_generics,
1576         },
1577
1578         _ => &no_generics,
1579     };
1580
1581     let has_self = opt_self.is_some();
1582     let mut parent_has_self = false;
1583     let mut own_start = has_self as u32;
1584     let parent_count = parent_def_id.map_or(0, |def_id| {
1585         let generics = tcx.generics_of(def_id);
1586         assert!(!has_self);
1587         parent_has_self = generics.has_self;
1588         own_start = generics.count() as u32;
1589         generics.parent_count + generics.params.len()
1590     });
1591
1592     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1593
1594     if let Some(opt_self) = opt_self {
1595         params.push(opt_self);
1596     }
1597
1598     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1599     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1600         name: param.name.ident().name,
1601         index: own_start + i as u32,
1602         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1603         pure_wrt_drop: param.pure_wrt_drop,
1604         kind: ty::GenericParamDefKind::Lifetime,
1605     }));
1606
1607     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1608
1609     // Now create the real type and const parameters.
1610     let type_start = own_start - has_self as u32 + params.len() as u32;
1611     let mut i = 0;
1612
1613     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1614         GenericParamKind::Lifetime { .. } => None,
1615         GenericParamKind::Type { ref default, synthetic, .. } => {
1616             if !allow_defaults && default.is_some() {
1617                 if !tcx.features().default_type_parameter_fallback {
1618                     tcx.struct_span_lint_hir(
1619                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1620                         param.hir_id,
1621                         param.span,
1622                         |lint| {
1623                             lint.build(
1624                                 "defaults for type parameters are only allowed in \
1625                                  `struct`, `enum`, `type`, or `trait` definitions",
1626                             )
1627                             .emit();
1628                         },
1629                     );
1630                 }
1631             }
1632
1633             let kind = ty::GenericParamDefKind::Type {
1634                 has_default: default.is_some(),
1635                 object_lifetime_default: object_lifetime_defaults
1636                     .as_ref()
1637                     .map_or(rl::Set1::Empty, |o| o[i]),
1638                 synthetic,
1639             };
1640
1641             let param_def = ty::GenericParamDef {
1642                 index: type_start + i as u32,
1643                 name: param.name.ident().name,
1644                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1645                 pure_wrt_drop: param.pure_wrt_drop,
1646                 kind,
1647             };
1648             i += 1;
1649             Some(param_def)
1650         }
1651         GenericParamKind::Const { default, .. } => {
1652             if !allow_defaults && default.is_some() {
1653                 tcx.sess.span_err(
1654                     param.span,
1655                     "defaults for const parameters are only allowed in \
1656                     `struct`, `enum`, `type`, or `trait` definitions",
1657                 );
1658             }
1659
1660             let param_def = ty::GenericParamDef {
1661                 index: type_start + i as u32,
1662                 name: param.name.ident().name,
1663                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1664                 pure_wrt_drop: param.pure_wrt_drop,
1665                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1666             };
1667             i += 1;
1668             Some(param_def)
1669         }
1670     }));
1671
1672     // provide junk type parameter defs - the only place that
1673     // cares about anything but the length is instantiation,
1674     // and we don't do that for closures.
1675     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1676         let dummy_args = if gen.is_some() {
1677             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1678         } else {
1679             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1680         };
1681
1682         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1683             index: type_start + i as u32,
1684             name: Symbol::intern(arg),
1685             def_id,
1686             pure_wrt_drop: false,
1687             kind: ty::GenericParamDefKind::Type {
1688                 has_default: false,
1689                 object_lifetime_default: rl::Set1::Empty,
1690                 synthetic: None,
1691             },
1692         }));
1693     }
1694
1695     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1696
1697     ty::Generics {
1698         parent: parent_def_id,
1699         parent_count,
1700         params,
1701         param_def_id_to_index,
1702         has_self: has_self || parent_has_self,
1703         has_late_bound_regions: has_late_bound_regions(tcx, node),
1704     }
1705 }
1706
1707 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1708     generic_args.iter().any(|arg| match arg {
1709         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1710         hir::GenericArg::Infer(_) => true,
1711         _ => false,
1712     })
1713 }
1714
1715 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1716 /// use inference to provide suggestions for the appropriate type if possible.
1717 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1718     use hir::TyKind::*;
1719     match &ty.kind {
1720         Infer => true,
1721         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1722         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1723         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1724         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1725         Path(hir::QPath::TypeRelative(ty, segment)) => {
1726             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1727         }
1728         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1729             ty_opt.map_or(false, is_suggestable_infer_ty)
1730                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1731         }
1732         _ => false,
1733     }
1734 }
1735
1736 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1737     if let hir::FnRetTy::Return(ty) = output {
1738         if is_suggestable_infer_ty(ty) {
1739             return Some(&*ty);
1740         }
1741     }
1742     None
1743 }
1744
1745 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1746     use rustc_hir::Node::*;
1747     use rustc_hir::*;
1748
1749     let def_id = def_id.expect_local();
1750     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1751
1752     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1753
1754     match tcx.hir().get(hir_id) {
1755         TraitItem(hir::TraitItem {
1756             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1757             ident,
1758             generics,
1759             ..
1760         })
1761         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1762         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1763             match get_infer_ret_ty(&sig.decl.output) {
1764                 Some(ty) => {
1765                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1766                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1767                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1768                         ty::ReErased => tcx.lifetimes.re_static,
1769                         _ => r,
1770                     });
1771                     let fn_sig = ty::Binder::dummy(fn_sig);
1772
1773                     let mut visitor = PlaceholderHirTyCollector::default();
1774                     visitor.visit_ty(ty);
1775                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
1776                     let ret_ty = fn_sig.skip_binder().output();
1777                     if ret_ty != tcx.ty_error() {
1778                         if !ret_ty.is_closure() {
1779                             let ret_ty_str = match ret_ty.kind() {
1780                                 // Suggest a function pointer return type instead of a unique function definition
1781                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1782                                 // syntax)
1783                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1784                                 _ => ret_ty.to_string(),
1785                             };
1786                             diag.span_suggestion(
1787                                 ty.span,
1788                                 "replace with the correct return type",
1789                                 ret_ty_str,
1790                                 Applicability::MaybeIncorrect,
1791                             );
1792                         } else {
1793                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1794                             // to prevent the user from getting a papercut while trying to use the unique closure
1795                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1796                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1797                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1798                         }
1799                     }
1800                     diag.emit();
1801
1802                     fn_sig
1803                 }
1804                 None => <dyn AstConv<'_>>::ty_of_fn(
1805                     &icx,
1806                     hir_id,
1807                     sig.header.unsafety,
1808                     sig.header.abi,
1809                     sig.decl,
1810                     generics,
1811                     Some(ident.span),
1812                     None,
1813                 ),
1814             }
1815         }
1816
1817         TraitItem(hir::TraitItem {
1818             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1819             ident,
1820             generics,
1821             ..
1822         }) => <dyn AstConv<'_>>::ty_of_fn(
1823             &icx,
1824             hir_id,
1825             header.unsafety,
1826             header.abi,
1827             decl,
1828             generics,
1829             Some(ident.span),
1830             None,
1831         ),
1832
1833         ForeignItem(&hir::ForeignItem {
1834             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1835         }) => {
1836             let abi = tcx.hir().get_foreign_abi(hir_id);
1837             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1838         }
1839
1840         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1841             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1842             let inputs =
1843                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1844             ty::Binder::dummy(tcx.mk_fn_sig(
1845                 inputs,
1846                 ty,
1847                 false,
1848                 hir::Unsafety::Normal,
1849                 abi::Abi::Rust,
1850             ))
1851         }
1852
1853         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1854             // Closure signatures are not like other function
1855             // signatures and cannot be accessed through `fn_sig`. For
1856             // example, a closure signature excludes the `self`
1857             // argument. In any case they are embedded within the
1858             // closure type as part of the `ClosureSubsts`.
1859             //
1860             // To get the signature of a closure, you should use the
1861             // `sig` method on the `ClosureSubsts`:
1862             //
1863             //    substs.as_closure().sig(def_id, tcx)
1864             bug!(
1865                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1866             );
1867         }
1868
1869         x => {
1870             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1871         }
1872     }
1873 }
1874
1875 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1876     let icx = ItemCtxt::new(tcx, def_id);
1877
1878     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1879     match tcx.hir().expect_item(hir_id).kind {
1880         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1881             let selfty = tcx.type_of(def_id);
1882             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1883         }),
1884         _ => bug!(),
1885     }
1886 }
1887
1888 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1889     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1890     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1891     let item = tcx.hir().expect_item(hir_id);
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         let mut span = tcx.def_span(def_id);
1990         if tcx.sess.source_map().is_local_span(span) {
1991             // `guess_head_span` reads the actual source file from
1992             // disk to try to determine the 'head' snippet of the span.
1993             // Don't do this for a span that comes from a file outside
1994             // of our crate, since this would make our query output
1995             // (and overall crate metadata) dependent on the
1996             // *current* state of an external file.
1997             span = tcx.sess.source_map().guess_head_span(span);
1998         }
1999         result.predicates =
2000             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2001                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2002                 span,
2003             ))));
2004     }
2005     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2006     result
2007 }
2008
2009 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2010 /// N.B., this does not include any implied/inferred constraints.
2011 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2012     use rustc_hir::*;
2013
2014     debug!("explicit_predicates_of(def_id={:?})", def_id);
2015
2016     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2017     let node = tcx.hir().get(hir_id);
2018
2019     let mut is_trait = None;
2020     let mut is_default_impl_trait = None;
2021
2022     let icx = ItemCtxt::new(tcx, def_id);
2023
2024     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2025
2026     // We use an `IndexSet` to preserves order of insertion.
2027     // Preserving the order of insertion is important here so as not to break UI tests.
2028     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2029
2030     let ast_generics = match node {
2031         Node::TraitItem(item) => &item.generics,
2032
2033         Node::ImplItem(item) => &item.generics,
2034
2035         Node::Item(item) => {
2036             match item.kind {
2037                 ItemKind::Impl(ref impl_) => {
2038                     if impl_.defaultness.is_default() {
2039                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2040                     }
2041                     &impl_.generics
2042                 }
2043                 ItemKind::Fn(.., ref generics, _)
2044                 | ItemKind::TyAlias(_, ref generics)
2045                 | ItemKind::Enum(_, ref generics)
2046                 | ItemKind::Struct(_, ref generics)
2047                 | ItemKind::Union(_, ref generics) => generics,
2048
2049                 ItemKind::Trait(_, _, ref generics, ..) => {
2050                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2051                     generics
2052                 }
2053                 ItemKind::TraitAlias(ref generics, _) => {
2054                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2055                     generics
2056                 }
2057                 ItemKind::OpaqueTy(OpaqueTy {
2058                     bounds: _,
2059                     impl_trait_fn,
2060                     ref generics,
2061                     origin: _,
2062                 }) => {
2063                     if impl_trait_fn.is_some() {
2064                         // return-position impl trait
2065                         //
2066                         // We don't inherit predicates from the parent here:
2067                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2068                         // then the return type is `f::<'static, T>::{{opaque}}`.
2069                         //
2070                         // If we inherited the predicates of `f` then we would
2071                         // require that `T: 'static` to show that the return
2072                         // type is well-formed.
2073                         //
2074                         // The only way to have something with this opaque type
2075                         // is from the return type of the containing function,
2076                         // which will ensure that the function's predicates
2077                         // hold.
2078                         return ty::GenericPredicates { parent: None, predicates: &[] };
2079                     } else {
2080                         // type-alias impl trait
2081                         generics
2082                     }
2083                 }
2084
2085                 _ => NO_GENERICS,
2086             }
2087         }
2088
2089         Node::ForeignItem(item) => match item.kind {
2090             ForeignItemKind::Static(..) => NO_GENERICS,
2091             ForeignItemKind::Fn(_, _, ref generics) => generics,
2092             ForeignItemKind::Type => NO_GENERICS,
2093         },
2094
2095         _ => NO_GENERICS,
2096     };
2097
2098     let generics = tcx.generics_of(def_id);
2099     let parent_count = generics.parent_count as u32;
2100     let has_own_self = generics.has_self && parent_count == 0;
2101
2102     // Below we'll consider the bounds on the type parameters (including `Self`)
2103     // and the explicit where-clauses, but to get the full set of predicates
2104     // on a trait we need to add in the supertrait bounds and bounds found on
2105     // associated types.
2106     if let Some(_trait_ref) = is_trait {
2107         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2108     }
2109
2110     // In default impls, we can assume that the self type implements
2111     // the trait. So in:
2112     //
2113     //     default impl Foo for Bar { .. }
2114     //
2115     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2116     // (see below). Recall that a default impl is not itself an impl, but rather a
2117     // set of defaults that can be incorporated into another impl.
2118     if let Some(trait_ref) = is_default_impl_trait {
2119         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2120     }
2121
2122     // Collect the region predicates that were declared inline as
2123     // well. In the case of parameters declared on a fn or method, we
2124     // have to be careful to only iterate over early-bound regions.
2125     let mut index = parent_count + has_own_self as u32;
2126     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2127         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2128             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2129             index,
2130             name: param.name.ident().name,
2131         }));
2132         index += 1;
2133
2134         match param.kind {
2135             GenericParamKind::Lifetime { .. } => {
2136                 param.bounds.iter().for_each(|bound| match bound {
2137                     hir::GenericBound::Outlives(lt) => {
2138                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2139                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2140                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2141                     }
2142                     _ => bug!(),
2143                 });
2144             }
2145             _ => bug!(),
2146         }
2147     }
2148
2149     // Collect the predicates that were written inline by the user on each
2150     // type parameter (e.g., `<T: Foo>`).
2151     for param in ast_generics.params {
2152         match param.kind {
2153             // We already dealt with early bound lifetimes above.
2154             GenericParamKind::Lifetime { .. } => (),
2155             GenericParamKind::Type { .. } => {
2156                 let name = param.name.ident().name;
2157                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2158                 index += 1;
2159
2160                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2161                 // Params are implicitly sized unless a `?Sized` bound is found
2162                 <dyn AstConv<'_>>::add_implicitly_sized(
2163                     &icx,
2164                     &mut bounds,
2165                     param.bounds,
2166                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2167                     param.span,
2168                 );
2169                 predicates.extend(bounds.predicates(tcx, param_ty));
2170             }
2171             GenericParamKind::Const { .. } => {
2172                 // Bounds on const parameters are currently not possible.
2173                 debug_assert!(param.bounds.is_empty());
2174                 index += 1;
2175             }
2176         }
2177     }
2178
2179     // Add in the bounds that appear in the where-clause.
2180     let where_clause = &ast_generics.where_clause;
2181     for predicate in where_clause.predicates {
2182         match predicate {
2183             hir::WherePredicate::BoundPredicate(bound_pred) => {
2184                 let ty = icx.to_ty(bound_pred.bounded_ty);
2185                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2186
2187                 // Keep the type around in a dummy predicate, in case of no bounds.
2188                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2189                 // is still checked for WF.
2190                 if bound_pred.bounds.is_empty() {
2191                     if let ty::Param(_) = ty.kind() {
2192                         // This is a `where T:`, which can be in the HIR from the
2193                         // transformation that moves `?Sized` to `T`'s declaration.
2194                         // We can skip the predicate because type parameters are
2195                         // trivially WF, but also we *should*, to avoid exposing
2196                         // users who never wrote `where Type:,` themselves, to
2197                         // compiler/tooling bugs from not handling WF predicates.
2198                     } else {
2199                         let span = bound_pred.bounded_ty.span;
2200                         let re_root_empty = tcx.lifetimes.re_root_empty;
2201                         let predicate = ty::Binder::bind_with_vars(
2202                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2203                                 ty,
2204                                 re_root_empty,
2205                             )),
2206                             bound_vars,
2207                         );
2208                         predicates.insert((predicate.to_predicate(tcx), span));
2209                     }
2210                 }
2211
2212                 let mut bounds = Bounds::default();
2213                 <dyn AstConv<'_>>::add_bounds(
2214                     &icx,
2215                     ty,
2216                     bound_pred.bounds.iter(),
2217                     &mut bounds,
2218                     bound_vars,
2219                 );
2220                 predicates.extend(bounds.predicates(tcx, ty));
2221             }
2222
2223             hir::WherePredicate::RegionPredicate(region_pred) => {
2224                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2225                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2226                     let (r2, span) = match bound {
2227                         hir::GenericBound::Outlives(lt) => {
2228                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2229                         }
2230                         _ => bug!(),
2231                     };
2232                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2233                         ty::OutlivesPredicate(r1, r2),
2234                     ))
2235                     .to_predicate(icx.tcx);
2236
2237                     (pred, span)
2238                 }))
2239             }
2240
2241             hir::WherePredicate::EqPredicate(..) => {
2242                 // FIXME(#20041)
2243             }
2244         }
2245     }
2246
2247     if tcx.features().generic_const_exprs {
2248         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2249     }
2250
2251     let mut predicates: Vec<_> = predicates.into_iter().collect();
2252
2253     // Subtle: before we store the predicates into the tcx, we
2254     // sort them so that predicates like `T: Foo<Item=U>` come
2255     // before uses of `U`.  This avoids false ambiguity errors
2256     // in trait checking. See `setup_constraining_predicates`
2257     // for details.
2258     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2259         let self_ty = tcx.type_of(def_id);
2260         let trait_ref = tcx.impl_trait_ref(def_id);
2261         cgp::setup_constraining_predicates(
2262             tcx,
2263             &mut predicates,
2264             trait_ref,
2265             &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref),
2266         );
2267     }
2268
2269     let result = ty::GenericPredicates {
2270         parent: generics.parent,
2271         predicates: tcx.arena.alloc_from_iter(predicates),
2272     };
2273     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2274     result
2275 }
2276
2277 fn const_evaluatable_predicates_of<'tcx>(
2278     tcx: TyCtxt<'tcx>,
2279     def_id: LocalDefId,
2280 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2281     struct ConstCollector<'tcx> {
2282         tcx: TyCtxt<'tcx>,
2283         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2284     }
2285
2286     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2287         type Map = Map<'tcx>;
2288
2289         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2290             intravisit::NestedVisitorMap::None
2291         }
2292
2293         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2294             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2295             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2296             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2297                 assert_eq!(uv.promoted, None);
2298                 let span = self.tcx.hir().span(c.hir_id);
2299                 self.preds.insert((
2300                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2301                         .to_predicate(self.tcx),
2302                     span,
2303                 ));
2304             }
2305         }
2306
2307         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2308             // Do not look into const param defaults,
2309             // these get checked when they are actually instantiated.
2310             //
2311             // We do not want the following to error:
2312             //
2313             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2314             //     struct Bar<const N: usize>(Foo<N, 3>);
2315         }
2316     }
2317
2318     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2319     let node = tcx.hir().get(hir_id);
2320
2321     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2322     if let hir::Node::Item(item) = node {
2323         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2324             if let Some(of_trait) = &impl_.of_trait {
2325                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2326                 collector.visit_trait_ref(of_trait);
2327             }
2328
2329             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2330             collector.visit_ty(impl_.self_ty);
2331         }
2332     }
2333
2334     if let Some(generics) = node.generics() {
2335         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2336         collector.visit_generics(generics);
2337     }
2338
2339     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2340         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2341         collector.visit_fn_decl(fn_sig.decl);
2342     }
2343     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2344
2345     collector.preds
2346 }
2347
2348 fn trait_explicit_predicates_and_bounds(
2349     tcx: TyCtxt<'_>,
2350     def_id: LocalDefId,
2351 ) -> ty::GenericPredicates<'_> {
2352     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2353     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2354 }
2355
2356 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2357     let def_kind = tcx.def_kind(def_id);
2358     if let DefKind::Trait = def_kind {
2359         // Remove bounds on associated types from the predicates, they will be
2360         // returned by `explicit_item_bounds`.
2361         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2362         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2363
2364         let is_assoc_item_ty = |ty: Ty<'_>| {
2365             // For a predicate from a where clause to become a bound on an
2366             // associated type:
2367             // * It must use the identity substs of the item.
2368             //     * Since any generic parameters on the item are not in scope,
2369             //       this means that the item is not a GAT, and its identity
2370             //       substs are the same as the trait's.
2371             // * It must be an associated type for this trait (*not* a
2372             //   supertrait).
2373             if let ty::Projection(projection) = ty.kind() {
2374                 projection.substs == trait_identity_substs
2375                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2376             } else {
2377                 false
2378             }
2379         };
2380
2381         let predicates: Vec<_> = predicates_and_bounds
2382             .predicates
2383             .iter()
2384             .copied()
2385             .filter(|(pred, _)| match pred.kind().skip_binder() {
2386                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2387                 ty::PredicateKind::Projection(proj) => {
2388                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2389                 }
2390                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2391                 _ => true,
2392             })
2393             .collect();
2394         if predicates.len() == predicates_and_bounds.predicates.len() {
2395             predicates_and_bounds
2396         } else {
2397             ty::GenericPredicates {
2398                 parent: predicates_and_bounds.parent,
2399                 predicates: tcx.arena.alloc_slice(&predicates),
2400             }
2401         }
2402     } else {
2403         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2404             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2405             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2406                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2407                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2408                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2409                 //
2410                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2411                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2412                 //        ^^^                                             explicit_predicates_of on
2413                 //        parent item we dont have set as the
2414                 //        parent of generics returned by `generics_of`
2415                 //
2416                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2417                 let item_id = tcx.hir().get_parent_item(hir_id);
2418                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2419                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2420                 return tcx.explicit_predicates_of(item_def_id);
2421             }
2422         }
2423         gather_explicit_predicates_of(tcx, def_id)
2424     }
2425 }
2426
2427 /// Converts a specific `GenericBound` from the AST into a set of
2428 /// predicates that apply to the self type. A vector is returned
2429 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2430 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2431 /// and `<T as Bar>::X == i32`).
2432 fn predicates_from_bound<'tcx>(
2433     astconv: &dyn AstConv<'tcx>,
2434     param_ty: Ty<'tcx>,
2435     bound: &'tcx hir::GenericBound<'tcx>,
2436 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2437     let mut bounds = Bounds::default();
2438     astconv.add_bounds(
2439         param_ty,
2440         std::array::IntoIter::new([bound]),
2441         &mut bounds,
2442         ty::List::empty(),
2443     );
2444     bounds.predicates(astconv.tcx(), param_ty)
2445 }
2446
2447 fn compute_sig_of_foreign_fn_decl<'tcx>(
2448     tcx: TyCtxt<'tcx>,
2449     def_id: DefId,
2450     decl: &'tcx hir::FnDecl<'tcx>,
2451     abi: abi::Abi,
2452     ident: Ident,
2453 ) -> ty::PolyFnSig<'tcx> {
2454     let unsafety = if abi == abi::Abi::RustIntrinsic {
2455         intrinsic_operation_unsafety(tcx.item_name(def_id))
2456     } else {
2457         hir::Unsafety::Unsafe
2458     };
2459     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2460     let fty = <dyn AstConv<'_>>::ty_of_fn(
2461         &ItemCtxt::new(tcx, def_id),
2462         hir_id,
2463         unsafety,
2464         abi,
2465         decl,
2466         &hir::Generics::empty(),
2467         Some(ident.span),
2468         None,
2469     );
2470
2471     // Feature gate SIMD types in FFI, since I am not sure that the
2472     // ABIs are handled at all correctly. -huonw
2473     if abi != abi::Abi::RustIntrinsic
2474         && abi != abi::Abi::PlatformIntrinsic
2475         && !tcx.features().simd_ffi
2476     {
2477         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2478             if ty.is_simd() {
2479                 let snip = tcx
2480                     .sess
2481                     .source_map()
2482                     .span_to_snippet(ast_ty.span)
2483                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2484                 tcx.sess
2485                     .struct_span_err(
2486                         ast_ty.span,
2487                         &format!(
2488                             "use of SIMD type{} in FFI is highly experimental and \
2489                              may result in invalid code",
2490                             snip
2491                         ),
2492                     )
2493                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2494                     .emit();
2495             }
2496         };
2497         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2498             check(input, ty)
2499         }
2500         if let hir::FnRetTy::Return(ref ty) = decl.output {
2501             check(ty, fty.output().skip_binder())
2502         }
2503     }
2504
2505     fty
2506 }
2507
2508 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2509     match tcx.hir().get_if_local(def_id) {
2510         Some(Node::ForeignItem(..)) => true,
2511         Some(_) => false,
2512         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2513     }
2514 }
2515
2516 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2517     match tcx.hir().get_if_local(def_id) {
2518         Some(
2519             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2520             | Node::ForeignItem(&hir::ForeignItem {
2521                 kind: hir::ForeignItemKind::Static(_, mutbl),
2522                 ..
2523             }),
2524         ) => Some(mutbl),
2525         Some(_) => None,
2526         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2527     }
2528 }
2529
2530 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2531     match tcx.hir().get_if_local(def_id) {
2532         Some(Node::Expr(&rustc_hir::Expr {
2533             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2534             ..
2535         })) => tcx.hir().body(body_id).generator_kind(),
2536         Some(_) => None,
2537         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2538     }
2539 }
2540
2541 fn from_target_feature(
2542     tcx: TyCtxt<'_>,
2543     id: DefId,
2544     attr: &ast::Attribute,
2545     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2546     target_features: &mut Vec<Symbol>,
2547 ) {
2548     let list = match attr.meta_item_list() {
2549         Some(list) => list,
2550         None => return,
2551     };
2552     let bad_item = |span| {
2553         let msg = "malformed `target_feature` attribute input";
2554         let code = "enable = \"..\"".to_owned();
2555         tcx.sess
2556             .struct_span_err(span, msg)
2557             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2558             .emit();
2559     };
2560     let rust_features = tcx.features();
2561     for item in list {
2562         // Only `enable = ...` is accepted in the meta-item list.
2563         if !item.has_name(sym::enable) {
2564             bad_item(item.span());
2565             continue;
2566         }
2567
2568         // Must be of the form `enable = "..."` (a string).
2569         let value = match item.value_str() {
2570             Some(value) => value,
2571             None => {
2572                 bad_item(item.span());
2573                 continue;
2574             }
2575         };
2576
2577         // We allow comma separation to enable multiple features.
2578         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2579             let feature_gate = match supported_target_features.get(feature) {
2580                 Some(g) => g,
2581                 None => {
2582                     let msg =
2583                         format!("the feature named `{}` is not valid for this target", feature);
2584                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2585                     err.span_label(
2586                         item.span(),
2587                         format!("`{}` is not valid for this target", feature),
2588                     );
2589                     if let Some(stripped) = feature.strip_prefix('+') {
2590                         let valid = supported_target_features.contains_key(stripped);
2591                         if valid {
2592                             err.help("consider removing the leading `+` in the feature name");
2593                         }
2594                     }
2595                     err.emit();
2596                     return None;
2597                 }
2598             };
2599
2600             // Only allow features whose feature gates have been enabled.
2601             let allowed = match feature_gate.as_ref().copied() {
2602                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2603                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2604                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2605                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2606                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2607                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2608                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2609                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2610                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2611                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2612                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2613                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2614                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2615                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2616                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2617                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2618                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2619                 Some(name) => bug!("unknown target feature gate {}", name),
2620                 None => true,
2621             };
2622             if !allowed && id.is_local() {
2623                 feature_err(
2624                     &tcx.sess.parse_sess,
2625                     feature_gate.unwrap(),
2626                     item.span(),
2627                     &format!("the target feature `{}` is currently unstable", feature),
2628                 )
2629                 .emit();
2630             }
2631             Some(Symbol::intern(feature))
2632         }));
2633     }
2634 }
2635
2636 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2637     use rustc_middle::mir::mono::Linkage::*;
2638
2639     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2640     // applicable to variable declarations and may not really make sense for
2641     // Rust code in the first place but allow them anyway and trust that the
2642     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2643     // up in the future.
2644     //
2645     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2646     // and don't have to be, LLVM treats them as no-ops.
2647     match name {
2648         "appending" => Appending,
2649         "available_externally" => AvailableExternally,
2650         "common" => Common,
2651         "extern_weak" => ExternalWeak,
2652         "external" => External,
2653         "internal" => Internal,
2654         "linkonce" => LinkOnceAny,
2655         "linkonce_odr" => LinkOnceODR,
2656         "private" => Private,
2657         "weak" => WeakAny,
2658         "weak_odr" => WeakODR,
2659         _ => {
2660             let span = tcx.hir().span_if_local(def_id);
2661             if let Some(span) = span {
2662                 tcx.sess.span_fatal(span, "invalid linkage specified")
2663             } else {
2664                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2665             }
2666         }
2667     }
2668 }
2669
2670 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2671     let attrs = tcx.get_attrs(id);
2672
2673     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2674     if tcx.should_inherit_track_caller(id) {
2675         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2676     }
2677
2678     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2679     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2680         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2681             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2682         }
2683     }
2684
2685     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2686
2687     let mut inline_span = None;
2688     let mut link_ordinal_span = None;
2689     let mut no_sanitize_span = None;
2690     for attr in attrs.iter() {
2691         if attr.has_name(sym::cold) {
2692             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2693         } else if attr.has_name(sym::rustc_allocator) {
2694             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2695         } else if attr.has_name(sym::ffi_returns_twice) {
2696             if tcx.is_foreign_item(id) {
2697                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2698             } else {
2699                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2700                 struct_span_err!(
2701                     tcx.sess,
2702                     attr.span,
2703                     E0724,
2704                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2705                 )
2706                 .emit();
2707             }
2708         } else if attr.has_name(sym::ffi_pure) {
2709             if tcx.is_foreign_item(id) {
2710                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2711                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2712                     struct_span_err!(
2713                         tcx.sess,
2714                         attr.span,
2715                         E0757,
2716                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2717                     )
2718                     .emit();
2719                 } else {
2720                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2721                 }
2722             } else {
2723                 // `#[ffi_pure]` is only allowed on foreign functions
2724                 struct_span_err!(
2725                     tcx.sess,
2726                     attr.span,
2727                     E0755,
2728                     "`#[ffi_pure]` may only be used on foreign functions"
2729                 )
2730                 .emit();
2731             }
2732         } else if attr.has_name(sym::ffi_const) {
2733             if tcx.is_foreign_item(id) {
2734                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2735             } else {
2736                 // `#[ffi_const]` is only allowed on foreign functions
2737                 struct_span_err!(
2738                     tcx.sess,
2739                     attr.span,
2740                     E0756,
2741                     "`#[ffi_const]` may only be used on foreign functions"
2742                 )
2743                 .emit();
2744             }
2745         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2746             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2747         } else if attr.has_name(sym::naked) {
2748             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2749         } else if attr.has_name(sym::no_mangle) {
2750             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2751         } else if attr.has_name(sym::no_coverage) {
2752             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2753         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2754             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2755         } else if attr.has_name(sym::used) {
2756             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2757         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2758             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2759                 struct_span_err!(
2760                     tcx.sess,
2761                     attr.span,
2762                     E0776,
2763                     "`#[cmse_nonsecure_entry]` requires C ABI"
2764                 )
2765                 .emit();
2766             }
2767             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2768                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2769                     .emit();
2770             }
2771             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2772         } else if attr.has_name(sym::thread_local) {
2773             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2774         } else if attr.has_name(sym::track_caller) {
2775             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2776                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2777                     .emit();
2778             }
2779             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2780                 feature_err(
2781                     &tcx.sess.parse_sess,
2782                     sym::closure_track_caller,
2783                     attr.span,
2784                     "`#[track_caller]` on closures is currently unstable",
2785                 )
2786                 .emit();
2787             }
2788             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2789         } else if attr.has_name(sym::export_name) {
2790             if let Some(s) = attr.value_str() {
2791                 if s.as_str().contains('\0') {
2792                     // `#[export_name = ...]` will be converted to a null-terminated string,
2793                     // so it may not contain any null characters.
2794                     struct_span_err!(
2795                         tcx.sess,
2796                         attr.span,
2797                         E0648,
2798                         "`export_name` may not contain null characters"
2799                     )
2800                     .emit();
2801                 }
2802                 codegen_fn_attrs.export_name = Some(s);
2803             }
2804         } else if attr.has_name(sym::target_feature) {
2805             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2806                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2807                     // The `#[target_feature]` attribute is allowed on
2808                     // WebAssembly targets on all functions, including safe
2809                     // ones. Other targets require that `#[target_feature]` is
2810                     // only applied to unsafe funtions (pending the
2811                     // `target_feature_11` feature) because on most targets
2812                     // execution of instructions that are not supported is
2813                     // considered undefined behavior. For WebAssembly which is a
2814                     // 100% safe target at execution time it's not possible to
2815                     // execute undefined instructions, and even if a future
2816                     // feature was added in some form for this it would be a
2817                     // deterministic trap. There is no undefined behavior when
2818                     // executing WebAssembly so `#[target_feature]` is allowed
2819                     // on safe functions (but again, only for WebAssembly)
2820                     //
2821                     // Note that this is also allowed if `actually_rustdoc` so
2822                     // if a target is documenting some wasm-specific code then
2823                     // it's not spuriously denied.
2824                 } else if !tcx.features().target_feature_11 {
2825                     let mut err = feature_err(
2826                         &tcx.sess.parse_sess,
2827                         sym::target_feature_11,
2828                         attr.span,
2829                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2830                     );
2831                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2832                     err.emit();
2833                 } else if let Some(local_id) = id.as_local() {
2834                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2835                 }
2836             }
2837             from_target_feature(
2838                 tcx,
2839                 id,
2840                 attr,
2841                 supported_target_features,
2842                 &mut codegen_fn_attrs.target_features,
2843             );
2844         } else if attr.has_name(sym::linkage) {
2845             if let Some(val) = attr.value_str() {
2846                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2847             }
2848         } else if attr.has_name(sym::link_section) {
2849             if let Some(val) = attr.value_str() {
2850                 if val.as_str().bytes().any(|b| b == 0) {
2851                     let msg = format!(
2852                         "illegal null byte in link_section \
2853                          value: `{}`",
2854                         &val
2855                     );
2856                     tcx.sess.span_err(attr.span, &msg);
2857                 } else {
2858                     codegen_fn_attrs.link_section = Some(val);
2859                 }
2860             }
2861         } else if attr.has_name(sym::link_name) {
2862             codegen_fn_attrs.link_name = attr.value_str();
2863         } else if attr.has_name(sym::link_ordinal) {
2864             if link_ordinal_span.is_some() {
2865                 tcx.sess
2866                     .struct_span_err(
2867                         attr.span,
2868                         "multiple `link_ordinal` attributes on a single definition",
2869                     )
2870                     .emit();
2871             }
2872             link_ordinal_span = Some(attr.span);
2873             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2874                 codegen_fn_attrs.link_ordinal = ordinal;
2875             }
2876         } else if attr.has_name(sym::no_sanitize) {
2877             no_sanitize_span = Some(attr.span);
2878             if let Some(list) = attr.meta_item_list() {
2879                 for item in list.iter() {
2880                     if item.has_name(sym::address) {
2881                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2882                     } else if item.has_name(sym::cfi) {
2883                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2884                     } else if item.has_name(sym::memory) {
2885                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2886                     } else if item.has_name(sym::thread) {
2887                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2888                     } else if item.has_name(sym::hwaddress) {
2889                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2890                     } else {
2891                         tcx.sess
2892                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2893                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2894                             .emit();
2895                     }
2896                 }
2897             }
2898         } else if attr.has_name(sym::instruction_set) {
2899             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2900                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2901                     [NestedMetaItem::MetaItem(set)] => {
2902                         let segments =
2903                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2904                         match segments.as_slice() {
2905                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2906                                 if !tcx.sess.target.has_thumb_interworking {
2907                                     struct_span_err!(
2908                                         tcx.sess.diagnostic(),
2909                                         attr.span,
2910                                         E0779,
2911                                         "target does not support `#[instruction_set]`"
2912                                     )
2913                                     .emit();
2914                                     None
2915                                 } else if segments[1] == sym::a32 {
2916                                     Some(InstructionSetAttr::ArmA32)
2917                                 } else if segments[1] == sym::t32 {
2918                                     Some(InstructionSetAttr::ArmT32)
2919                                 } else {
2920                                     unreachable!()
2921                                 }
2922                             }
2923                             _ => {
2924                                 struct_span_err!(
2925                                     tcx.sess.diagnostic(),
2926                                     attr.span,
2927                                     E0779,
2928                                     "invalid instruction set specified",
2929                                 )
2930                                 .emit();
2931                                 None
2932                             }
2933                         }
2934                     }
2935                     [] => {
2936                         struct_span_err!(
2937                             tcx.sess.diagnostic(),
2938                             attr.span,
2939                             E0778,
2940                             "`#[instruction_set]` requires an argument"
2941                         )
2942                         .emit();
2943                         None
2944                     }
2945                     _ => {
2946                         struct_span_err!(
2947                             tcx.sess.diagnostic(),
2948                             attr.span,
2949                             E0779,
2950                             "cannot specify more than one instruction set"
2951                         )
2952                         .emit();
2953                         None
2954                     }
2955                 },
2956                 _ => {
2957                     struct_span_err!(
2958                         tcx.sess.diagnostic(),
2959                         attr.span,
2960                         E0778,
2961                         "must specify an instruction set"
2962                     )
2963                     .emit();
2964                     None
2965                 }
2966             };
2967         } else if attr.has_name(sym::repr) {
2968             codegen_fn_attrs.alignment = match attr.meta_item_list() {
2969                 Some(items) => match items.as_slice() {
2970                     [item] => match item.name_value_literal() {
2971                         Some((sym::align, literal)) => {
2972                             let alignment = rustc_attr::parse_alignment(&literal.kind);
2973
2974                             match alignment {
2975                                 Ok(align) => Some(align),
2976                                 Err(msg) => {
2977                                     struct_span_err!(
2978                                         tcx.sess.diagnostic(),
2979                                         attr.span,
2980                                         E0589,
2981                                         "invalid `repr(align)` attribute: {}",
2982                                         msg
2983                                     )
2984                                     .emit();
2985
2986                                     None
2987                                 }
2988                             }
2989                         }
2990                         _ => None,
2991                     },
2992                     [] => None,
2993                     _ => None,
2994                 },
2995                 None => None,
2996             };
2997         }
2998     }
2999
3000     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3001         if !attr.has_name(sym::inline) {
3002             return ia;
3003         }
3004         match attr.meta().map(|i| i.kind) {
3005             Some(MetaItemKind::Word) => InlineAttr::Hint,
3006             Some(MetaItemKind::List(ref items)) => {
3007                 inline_span = Some(attr.span);
3008                 if items.len() != 1 {
3009                     struct_span_err!(
3010                         tcx.sess.diagnostic(),
3011                         attr.span,
3012                         E0534,
3013                         "expected one argument"
3014                     )
3015                     .emit();
3016                     InlineAttr::None
3017                 } else if list_contains_name(&items[..], sym::always) {
3018                     InlineAttr::Always
3019                 } else if list_contains_name(&items[..], sym::never) {
3020                     InlineAttr::Never
3021                 } else {
3022                     struct_span_err!(
3023                         tcx.sess.diagnostic(),
3024                         items[0].span(),
3025                         E0535,
3026                         "invalid argument"
3027                     )
3028                     .emit();
3029
3030                     InlineAttr::None
3031                 }
3032             }
3033             Some(MetaItemKind::NameValue(_)) => ia,
3034             None => ia,
3035         }
3036     });
3037
3038     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3039         if !attr.has_name(sym::optimize) {
3040             return ia;
3041         }
3042         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3043         match attr.meta().map(|i| i.kind) {
3044             Some(MetaItemKind::Word) => {
3045                 err(attr.span, "expected one argument");
3046                 ia
3047             }
3048             Some(MetaItemKind::List(ref items)) => {
3049                 inline_span = Some(attr.span);
3050                 if items.len() != 1 {
3051                     err(attr.span, "expected one argument");
3052                     OptimizeAttr::None
3053                 } else if list_contains_name(&items[..], sym::size) {
3054                     OptimizeAttr::Size
3055                 } else if list_contains_name(&items[..], sym::speed) {
3056                     OptimizeAttr::Speed
3057                 } else {
3058                     err(items[0].span(), "invalid argument");
3059                     OptimizeAttr::None
3060                 }
3061             }
3062             Some(MetaItemKind::NameValue(_)) => ia,
3063             None => ia,
3064         }
3065     });
3066
3067     // #73631: closures inherit `#[target_feature]` annotations
3068     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3069         let owner_id = tcx.parent(id).expect("closure should have a parent");
3070         codegen_fn_attrs
3071             .target_features
3072             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3073     }
3074
3075     // If a function uses #[target_feature] it can't be inlined into general
3076     // purpose functions as they wouldn't have the right target features
3077     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3078     // respected.
3079     if !codegen_fn_attrs.target_features.is_empty() {
3080         if codegen_fn_attrs.inline == InlineAttr::Always {
3081             if let Some(span) = inline_span {
3082                 tcx.sess.span_err(
3083                     span,
3084                     "cannot use `#[inline(always)]` with \
3085                      `#[target_feature]`",
3086                 );
3087             }
3088         }
3089     }
3090
3091     if !codegen_fn_attrs.no_sanitize.is_empty() {
3092         if codegen_fn_attrs.inline == InlineAttr::Always {
3093             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3094                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3095                 tcx.struct_span_lint_hir(
3096                     lint::builtin::INLINE_NO_SANITIZE,
3097                     hir_id,
3098                     no_sanitize_span,
3099                     |lint| {
3100                         lint.build("`no_sanitize` will have no effect after inlining")
3101                             .span_note(inline_span, "inlining requested here")
3102                             .emit();
3103                     },
3104                 )
3105             }
3106         }
3107     }
3108
3109     // Weak lang items have the same semantics as "std internal" symbols in the
3110     // sense that they're preserved through all our LTO passes and only
3111     // strippable by the linker.
3112     //
3113     // Additionally weak lang items have predetermined symbol names.
3114     if tcx.is_weak_lang_item(id) {
3115         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3116     }
3117     let check_name = |attr: &Attribute, sym| attr.has_name(sym);
3118     if let Some(name) = weak_lang_items::link_name(check_name, attrs) {
3119         codegen_fn_attrs.export_name = Some(name);
3120         codegen_fn_attrs.link_name = Some(name);
3121     }
3122     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3123
3124     // Internal symbols to the standard library all have no_mangle semantics in
3125     // that they have defined symbol names present in the function name. This
3126     // also applies to weak symbols where they all have known symbol names.
3127     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3128         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3129     }
3130
3131     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3132     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3133     // intrinsic functions.
3134     if let Some(name) = &codegen_fn_attrs.link_name {
3135         if name.as_str().starts_with("llvm.") {
3136             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3137         }
3138     }
3139
3140     codegen_fn_attrs
3141 }
3142
3143 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3144 /// applied to the method prototype.
3145 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3146     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3147         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3148             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3149                 if let Some(trait_item) = tcx
3150                     .associated_items(trait_def_id)
3151                     .filter_by_name_unhygienic(impl_item.ident.name)
3152                     .find(move |trait_item| {
3153                         trait_item.kind == ty::AssocKind::Fn
3154                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3155                     })
3156                 {
3157                     return tcx
3158                         .codegen_fn_attrs(trait_item.def_id)
3159                         .flags
3160                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3161                 }
3162             }
3163         }
3164     }
3165
3166     false
3167 }
3168
3169 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3170     use rustc_ast::{Lit, LitIntType, LitKind};
3171     let meta_item_list = attr.meta_item_list();
3172     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3173     let sole_meta_list = match meta_item_list {
3174         Some([item]) => item.literal(),
3175         Some(_) => {
3176             tcx.sess
3177                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3178                 .note("the attribute requires exactly one argument")
3179                 .emit();
3180             return None;
3181         }
3182         _ => None,
3183     };
3184     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3185         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3186         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3187         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3188         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3189         //
3190         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3191         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3192         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3193         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3194         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3195         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3196         // about LINK.EXE failing.)
3197         if *ordinal <= u16::MAX as u128 {
3198             Some(*ordinal as u16)
3199         } else {
3200             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3201             tcx.sess
3202                 .struct_span_err(attr.span, &msg)
3203                 .note("the value may not exceed `u16::MAX`")
3204                 .emit();
3205             None
3206         }
3207     } else {
3208         tcx.sess
3209             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3210             .note("an unsuffixed integer value, e.g., `1`, is expected")
3211             .emit();
3212         None
3213     }
3214 }
3215
3216 fn check_link_name_xor_ordinal(
3217     tcx: TyCtxt<'_>,
3218     codegen_fn_attrs: &CodegenFnAttrs,
3219     inline_span: Option<Span>,
3220 ) {
3221     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3222         return;
3223     }
3224     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3225     if let Some(span) = inline_span {
3226         tcx.sess.span_err(span, msg);
3227     } else {
3228         tcx.sess.err(msg);
3229     }
3230 }
3231
3232 /// Checks the function annotated with `#[target_feature]` is not a safe
3233 /// trait method implementation, reporting an error if it is.
3234 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3235     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3236     let node = tcx.hir().get(hir_id);
3237     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3238         let parent_id = tcx.hir().get_parent_item(hir_id);
3239         let parent_item = tcx.hir().expect_item(parent_id);
3240         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3241             tcx.sess
3242                 .struct_span_err(
3243                     attr_span,
3244                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3245                 )
3246                 .span_label(attr_span, "cannot be applied to safe trait method")
3247                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3248                 .emit();
3249         }
3250     }
3251 }