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