compiler/rustc_typeck/src/collect.rs

   1 // ignore-tidy-filelength
   2 //! "Collection" is the process of determining the type and other external
   3 //! details of each item in Rust. Collection is specifically concerned
   4 //! with *inter-procedural* things -- for example, for a function
   5 //! definition, collection will figure out the type and signature of the
   6 //! function, but it will not visit the *body* of the function in any way,
   7 //! nor examine type annotations on local variables (that's the job of
   8 //! type *checking*).
   9 //!
  10 //! Collecting is ultimately defined by a bundle of queries that
  11 //! inquire after various facts about the items in the crate (e.g.,
  12 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  13 //! for the full set.
  14 //!
  15 //! At present, however, we do run collection across all items in the
  16 //! crate as a kind of pass. This should eventually be factored away.
  17
  18 use crate::astconv::AstConv;
  19 use crate::bounds::Bounds;
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::errors;
  23 use crate::middle::resolve_lifetime as rl;
  24 use rustc_ast as ast;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::nested_filter;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         type_of: type_of::type_of,
  72         item_bounds: item_bounds::item_bounds,
  73         explicit_item_bounds: item_bounds::explicit_item_bounds,
  74         generics_of,
  75         predicates_of,
  76         predicates_defined_on,
  77         explicit_predicates_of,
  78         super_predicates_of,
  79         super_predicates_that_define_assoc_type,
  80         trait_explicit_predicates_and_bounds,
  81         type_param_predicates,
  82         trait_def,
  83         adt_def,
  84         fn_sig,
  85         impl_trait_ref,
  86         impl_polarity,
  87         is_foreign_item,
  88         static_mutability,
  89         generator_kind,
  90         codegen_fn_attrs,
  91         collect_mod_item_types,
  92         should_inherit_track_caller,
  93         ..*providers
  94     };
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98
  99 /// Context specific to some particular item. This is what implements
 100 /// `AstConv`. It has information about the predicates that are defined
 101 /// on the trait. Unfortunately, this predicate information is
 102 /// available in various different forms at various points in the
 103 /// process. So we can't just store a pointer to e.g., the AST or the
 104 /// parsed ty form, we have to be more flexible. To this end, the
 105 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 106 /// `get_type_parameter_bounds` requests, drawing the information from
 107 /// the AST (`hir::Generics`), recursively.
 108 pub struct ItemCtxt<'tcx> {
 109     tcx: TyCtxt<'tcx>,
 110     item_def_id: DefId,
 111 }
 112
 113 ///////////////////////////////////////////////////////////////////////////
 114
 115 #[derive(Default)]
 116 crate struct HirPlaceholderCollector(crate Vec<Span>);
 117
 118 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 119     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 120         if let hir::TyKind::Infer = t.kind {
 121             self.0.push(t.span);
 122         }
 123         intravisit::walk_ty(self, t)
 124     }
 125     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 126         match generic_arg {
 127             hir::GenericArg::Infer(inf) => {
 128                 self.0.push(inf.span);
 129                 intravisit::walk_inf(self, inf);
 130             }
 131             hir::GenericArg::Type(t) => self.visit_ty(t),
 132             _ => {}
 133         }
 134     }
 135     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 136         if let &hir::ArrayLen::Infer(_, span) = length {
 137             self.0.push(span);
 138         }
 139         intravisit::walk_array_len(self, length)
 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<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder(tcx, placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty {
 193             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 194                 is_fn = true;
 195
 196                 // Check if parent is const or static
 197                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 198                 let parent_node = tcx.hir().get(parent_id);
 199
 200                 is_const_or_static = matches!(
 201                     parent_node,
 202                     Node::Item(&hir::Item {
 203                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 204                         ..
 205                     }) | Node::TraitItem(&hir::TraitItem {
 206                         kind: hir::TraitItemKind::Const(..),
 207                         ..
 208                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 209                 );
 210             }
 211         }
 212
 213         // if function is wrapped around a const or static,
 214         // then don't show the suggestion
 215         if !(is_fn && is_const_or_static) {
 216             err.multipart_suggestion(
 217                 "use type parameters instead",
 218                 sugg,
 219                 Applicability::HasPlaceholders,
 220             );
 221         }
 222     }
 223     err.emit();
 224 }
 225
 226 fn reject_placeholder_type_signatures_in_item<'tcx>(
 227     tcx: TyCtxt<'tcx>,
 228     item: &'tcx hir::Item<'tcx>,
 229 ) {
 230     let (generics, suggest) = match &item.kind {
 231         hir::ItemKind::Union(_, generics)
 232         | hir::ItemKind::Enum(_, generics)
 233         | hir::ItemKind::TraitAlias(generics, _)
 234         | hir::ItemKind::Trait(_, _, generics, ..)
 235         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 236         | hir::ItemKind::Struct(_, generics) => (generics, true),
 237         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 238         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 239         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 240         _ => return,
 241     };
 242
 243     let mut visitor = HirPlaceholderCollector::default();
 244     visitor.visit_item(item);
 245
 246     placeholder_type_error(
 247         tcx,
 248         Some(generics.span),
 249         generics.params,
 250         visitor.0,
 251         suggest,
 252         None,
 253         item.kind.descr(),
 254     );
 255 }
 256
 257 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 258     type NestedFilter = nested_filter::OnlyBodies;
 259
 260     fn nested_visit_map(&mut self) -> Self::Map {
 261         self.tcx.hir()
 262     }
 263
 264     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 265         convert_item(self.tcx, item.item_id());
 266         reject_placeholder_type_signatures_in_item(self.tcx, item);
 267         intravisit::walk_item(self, item);
 268     }
 269
 270     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 271         for param in generics.params {
 272             match param.kind {
 273                 hir::GenericParamKind::Lifetime { .. } => {}
 274                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 275                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 276                     self.tcx.ensure().type_of(def_id);
 277                 }
 278                 hir::GenericParamKind::Type { .. } => {}
 279                 hir::GenericParamKind::Const { default, .. } => {
 280                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 281                     self.tcx.ensure().type_of(def_id);
 282                     if let Some(default) = default {
 283                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 284                         // need to store default and type of default
 285                         self.tcx.ensure().type_of(default_def_id);
 286                         self.tcx.ensure().const_param_default(def_id);
 287                     }
 288                 }
 289             }
 290         }
 291         intravisit::walk_generics(self, generics);
 292     }
 293
 294     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 295         if let hir::ExprKind::Closure(..) = expr.kind {
 296             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 297             self.tcx.ensure().generics_of(def_id);
 298             // We do not call `type_of` for closures here as that
 299             // depends on typecheck and would therefore hide
 300             // any further errors in case one typeck fails.
 301         }
 302         intravisit::walk_expr(self, expr);
 303     }
 304
 305     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 306         convert_trait_item(self.tcx, trait_item.trait_item_id());
 307         intravisit::walk_trait_item(self, trait_item);
 308     }
 309
 310     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 311         convert_impl_item(self.tcx, impl_item.impl_item_id());
 312         intravisit::walk_impl_item(self, impl_item);
 313     }
 314 }
 315
 316 ///////////////////////////////////////////////////////////////////////////
 317 // Utility types and common code for the above passes.
 318
 319 fn bad_placeholder<'tcx>(
 320     tcx: TyCtxt<'tcx>,
 321     mut spans: Vec<Span>,
 322     kind: &'static str,
 323 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 324     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 325
 326     spans.sort();
 327     let mut err = struct_span_err!(
 328         tcx.sess,
 329         spans.clone(),
 330         E0121,
 331         "the placeholder `_` is not allowed within types on item signatures for {}",
 332         kind
 333     );
 334     for span in spans {
 335         err.span_label(span, "not allowed in type signatures");
 336     }
 337     err
 338 }
 339
 340 impl<'tcx> ItemCtxt<'tcx> {
 341     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 342         ItemCtxt { tcx, item_def_id }
 343     }
 344
 345     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 346         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 347     }
 348
 349     pub fn hir_id(&self) -> hir::HirId {
 350         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 351     }
 352
 353     pub fn node(&self) -> hir::Node<'tcx> {
 354         self.tcx.hir().get(self.hir_id())
 355     }
 356 }
 357
 358 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 359     fn tcx(&self) -> TyCtxt<'tcx> {
 360         self.tcx
 361     }
 362
 363     fn item_def_id(&self) -> Option<DefId> {
 364         Some(self.item_def_id)
 365     }
 366
 367     fn get_type_parameter_bounds(
 368         &self,
 369         span: Span,
 370         def_id: DefId,
 371         assoc_name: Ident,
 372     ) -> ty::GenericPredicates<'tcx> {
 373         self.tcx.at(span).type_param_predicates((
 374             self.item_def_id,
 375             def_id.expect_local(),
 376             assoc_name,
 377         ))
 378     }
 379
 380     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 381         None
 382     }
 383
 384     fn allow_ty_infer(&self) -> bool {
 385         false
 386     }
 387
 388     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 389         self.tcx().ty_error_with_message(span, "bad placeholder type")
 390     }
 391
 392     fn ct_infer(
 393         &self,
 394         ty: Ty<'tcx>,
 395         _: Option<&ty::GenericParamDef>,
 396         span: Span,
 397     ) -> &'tcx Const<'tcx> {
 398         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 399             ty::ReErased => self.tcx.lifetimes.re_static,
 400             _ => r,
 401         });
 402         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 403     }
 404
 405     fn projected_ty_from_poly_trait_ref(
 406         &self,
 407         span: Span,
 408         item_def_id: DefId,
 409         item_segment: &hir::PathSegment<'_>,
 410         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 411     ) -> Ty<'tcx> {
 412         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 413             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 414                 self,
 415                 self.tcx,
 416                 span,
 417                 item_def_id,
 418                 item_segment,
 419                 trait_ref.substs,
 420             );
 421             self.tcx().mk_projection(item_def_id, item_substs)
 422         } else {
 423             // There are no late-bound regions; we can just ignore the binder.
 424             let mut err = struct_span_err!(
 425                 self.tcx().sess,
 426                 span,
 427                 E0212,
 428                 "cannot use the associated type of a trait \
 429                  with uninferred generic parameters"
 430             );
 431
 432             match self.node() {
 433                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 434                     let item =
 435                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 436                     match &item.kind {
 437                         hir::ItemKind::Enum(_, generics)
 438                         | hir::ItemKind::Struct(_, generics)
 439                         | hir::ItemKind::Union(_, generics) => {
 440                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 441                             let (lt_sp, sugg) = match generics.params {
 442                                 [] => (generics.span, format!("<{}>", lt_name)),
 443                                 [bound, ..] => {
 444                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 445                                 }
 446                             };
 447                             let suggestions = vec![
 448                                 (lt_sp, sugg),
 449                                 (
 450                                     span.with_hi(item_segment.ident.span.lo()),
 451                                     format!(
 452                                         "{}::",
 453                                         // Replace the existing lifetimes with a new named lifetime.
 454                                         self.tcx
 455                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 456                                                 self.tcx.mk_region(ty::ReEarlyBound(
 457                                                     ty::EarlyBoundRegion {
 458                                                         def_id: item_def_id,
 459                                                         index: 0,
 460                                                         name: Symbol::intern(&lt_name),
 461                                                     },
 462                                                 ))
 463                                             })
 464                                             .0,
 465                                     ),
 466                                 ),
 467                             ];
 468                             err.multipart_suggestion(
 469                                 "use a fully qualified path with explicit lifetimes",
 470                                 suggestions,
 471                                 Applicability::MaybeIncorrect,
 472                             );
 473                         }
 474                         _ => {}
 475                     }
 476                 }
 477                 hir::Node::Item(hir::Item {
 478                     kind:
 479                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 480                     ..
 481                 }) => {}
 482                 hir::Node::Item(_)
 483                 | hir::Node::ForeignItem(_)
 484                 | hir::Node::TraitItem(_)
 485                 | hir::Node::ImplItem(_) => {
 486                     err.span_suggestion_verbose(
 487                         span.with_hi(item_segment.ident.span.lo()),
 488                         "use a fully qualified path with inferred lifetimes",
 489                         format!(
 490                             "{}::",
 491                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 492                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 493                         ),
 494                         Applicability::MaybeIncorrect,
 495                     );
 496                 }
 497                 _ => {}
 498             }
 499             err.emit();
 500             self.tcx().ty_error()
 501         }
 502     }
 503
 504     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 505         // Types in item signatures are not normalized to avoid undue dependencies.
 506         ty
 507     }
 508
 509     fn set_tainted_by_errors(&self) {
 510         // There's no obvious place to track this, so just let it go.
 511     }
 512
 513     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 514         // There's no place to record types from signatures?
 515     }
 516 }
 517
 518 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 519 fn get_new_lifetime_name<'tcx>(
 520     tcx: TyCtxt<'tcx>,
 521     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 522     generics: &hir::Generics<'tcx>,
 523 ) -> String {
 524     let existing_lifetimes = tcx
 525         .collect_referenced_late_bound_regions(&poly_trait_ref)
 526         .into_iter()
 527         .filter_map(|lt| {
 528             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 529                 Some(name.as_str().to_string())
 530             } else {
 531                 None
 532             }
 533         })
 534         .chain(generics.params.iter().filter_map(|param| {
 535             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 536                 Some(param.name.ident().as_str().to_string())
 537             } else {
 538                 None
 539             }
 540         }))
 541         .collect::<FxHashSet<String>>();
 542
 543     let a_to_z_repeat_n = |n| {
 544         (b'a'..=b'z').map(move |c| {
 545             let mut s = '\''.to_string();
 546             s.extend(std::iter::repeat(char::from(c)).take(n));
 547             s
 548         })
 549     };
 550
 551     // If all single char lifetime names are present, we wrap around and double the chars.
 552     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 553 }
 554
 555 /// Returns the predicates defined on `item_def_id` of the form
 556 /// `X: Foo` where `X` is the type parameter `def_id`.
 557 fn type_param_predicates(
 558     tcx: TyCtxt<'_>,
 559     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 560 ) -> ty::GenericPredicates<'_> {
 561     use rustc_hir::*;
 562
 563     // In the AST, bounds can derive from two places. Either
 564     // written inline like `<T: Foo>` or in a where-clause like
 565     // `where T: Foo`.
 566
 567     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 568     let param_owner = tcx.hir().ty_param_owner(param_id);
 569     let generics = tcx.generics_of(param_owner);
 570     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 571     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 572
 573     // Don't look for bounds where the type parameter isn't in scope.
 574     let parent = if item_def_id == param_owner.to_def_id() {
 575         None
 576     } else {
 577         tcx.generics_of(item_def_id).parent
 578     };
 579
 580     let mut result = parent
 581         .map(|parent| {
 582             let icx = ItemCtxt::new(tcx, parent);
 583             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 584         })
 585         .unwrap_or_default();
 586     let mut extend = None;
 587
 588     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 589     let ast_generics = match tcx.hir().get(item_hir_id) {
 590         Node::TraitItem(item) => &item.generics,
 591
 592         Node::ImplItem(item) => &item.generics,
 593
 594         Node::Item(item) => {
 595             match item.kind {
 596                 ItemKind::Fn(.., ref generics, _)
 597                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 598                 | ItemKind::TyAlias(_, ref generics)
 599                 | ItemKind::OpaqueTy(OpaqueTy {
 600                     ref generics,
 601                     origin: hir::OpaqueTyOrigin::TyAlias,
 602                     ..
 603                 })
 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<'tcx> 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 { .. } | GenericParamKind::Const { .. }
 666                     if param.hir_id == param_id =>
 667                 {
 668                     Some(&param.bounds)
 669                 }
 670                 _ => None,
 671             })
 672             .flat_map(|bounds| bounds.iter())
 673             .filter(|b| match assoc_name {
 674                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 675                 None => true,
 676             })
 677             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 678
 679         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 680         let from_where_clauses = ast_generics
 681             .where_clause
 682             .predicates
 683             .iter()
 684             .filter_map(|wp| match *wp {
 685                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 686                 _ => None,
 687             })
 688             .flat_map(|bp| {
 689                 let bt = if bp.is_param_bound(param_def_id) {
 690                     Some(ty)
 691                 } else if !only_self_bounds.0 {
 692                     Some(self.to_ty(bp.bounded_ty))
 693                 } else {
 694                     None
 695                 };
 696                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 697
 698                 bp.bounds
 699                     .iter()
 700                     .filter(|b| match assoc_name {
 701                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 702                         None => true,
 703                     })
 704                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 705             })
 706             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 707
 708         from_ty_params.chain(from_where_clauses).collect()
 709     }
 710
 711     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 712         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 713
 714         match b {
 715             hir::GenericBound::Trait(poly_trait_ref, _) => {
 716                 let trait_ref = &poly_trait_ref.trait_ref;
 717                 if let Some(trait_did) = trait_ref.trait_def_id() {
 718                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 719                 } else {
 720                     false
 721                 }
 722             }
 723             _ => false,
 724         }
 725     }
 726 }
 727
 728 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 729     let it = tcx.hir().item(item_id);
 730     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 731     let def_id = item_id.def_id;
 732
 733     match it.kind {
 734         // These don't define types.
 735         hir::ItemKind::ExternCrate(_)
 736         | hir::ItemKind::Use(..)
 737         | hir::ItemKind::Macro(_)
 738         | hir::ItemKind::Mod(_)
 739         | hir::ItemKind::GlobalAsm(_) => {}
 740         hir::ItemKind::ForeignMod { items, .. } => {
 741             for item in items {
 742                 let item = tcx.hir().foreign_item(item.id);
 743                 tcx.ensure().generics_of(item.def_id);
 744                 tcx.ensure().type_of(item.def_id);
 745                 tcx.ensure().predicates_of(item.def_id);
 746                 match item.kind {
 747                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 748                     hir::ForeignItemKind::Static(..) => {
 749                         let mut visitor = HirPlaceholderCollector::default();
 750                         visitor.visit_foreign_item(item);
 751                         placeholder_type_error(
 752                             tcx,
 753                             None,
 754                             &[],
 755                             visitor.0,
 756                             false,
 757                             None,
 758                             "static variable",
 759                         );
 760                     }
 761                     _ => (),
 762                 }
 763             }
 764         }
 765         hir::ItemKind::Enum(ref enum_definition, _) => {
 766             tcx.ensure().generics_of(def_id);
 767             tcx.ensure().type_of(def_id);
 768             tcx.ensure().predicates_of(def_id);
 769             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 770         }
 771         hir::ItemKind::Impl { .. } => {
 772             tcx.ensure().generics_of(def_id);
 773             tcx.ensure().type_of(def_id);
 774             tcx.ensure().impl_trait_ref(def_id);
 775             tcx.ensure().predicates_of(def_id);
 776         }
 777         hir::ItemKind::Trait(..) => {
 778             tcx.ensure().generics_of(def_id);
 779             tcx.ensure().trait_def(def_id);
 780             tcx.at(it.span).super_predicates_of(def_id);
 781             tcx.ensure().predicates_of(def_id);
 782         }
 783         hir::ItemKind::TraitAlias(..) => {
 784             tcx.ensure().generics_of(def_id);
 785             tcx.at(it.span).super_predicates_of(def_id);
 786             tcx.ensure().predicates_of(def_id);
 787         }
 788         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 789             tcx.ensure().generics_of(def_id);
 790             tcx.ensure().type_of(def_id);
 791             tcx.ensure().predicates_of(def_id);
 792
 793             for f in struct_def.fields() {
 794                 let def_id = tcx.hir().local_def_id(f.hir_id);
 795                 tcx.ensure().generics_of(def_id);
 796                 tcx.ensure().type_of(def_id);
 797                 tcx.ensure().predicates_of(def_id);
 798             }
 799
 800             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 801                 convert_variant_ctor(tcx, ctor_hir_id);
 802             }
 803         }
 804
 805         // Desugared from `impl Trait`, so visited by the function's return type.
 806         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 807             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 808             ..
 809         }) => {}
 810
 811         // Don't call `type_of` on opaque types, since that depends on type
 812         // checking function bodies. `check_item_type` ensures that it's called
 813         // instead.
 814         hir::ItemKind::OpaqueTy(..) => {
 815             tcx.ensure().generics_of(def_id);
 816             tcx.ensure().predicates_of(def_id);
 817             tcx.ensure().explicit_item_bounds(def_id);
 818         }
 819         hir::ItemKind::TyAlias(..)
 820         | hir::ItemKind::Static(..)
 821         | hir::ItemKind::Const(..)
 822         | hir::ItemKind::Fn(..) => {
 823             tcx.ensure().generics_of(def_id);
 824             tcx.ensure().type_of(def_id);
 825             tcx.ensure().predicates_of(def_id);
 826             match it.kind {
 827                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 828                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 829                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 830                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 831                     if let hir::TyKind::TraitObject(..) = ty.kind {
 832                         let mut visitor = HirPlaceholderCollector::default();
 833                         visitor.visit_item(it);
 834                         placeholder_type_error(
 835                             tcx,
 836                             None,
 837                             &[],
 838                             visitor.0,
 839                             false,
 840                             None,
 841                             it.kind.descr(),
 842                         );
 843                     }
 844                 }
 845                 _ => (),
 846             }
 847         }
 848     }
 849 }
 850
 851 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 852     let trait_item = tcx.hir().trait_item(trait_item_id);
 853     tcx.ensure().generics_of(trait_item_id.def_id);
 854
 855     match trait_item.kind {
 856         hir::TraitItemKind::Fn(..) => {
 857             tcx.ensure().type_of(trait_item_id.def_id);
 858             tcx.ensure().fn_sig(trait_item_id.def_id);
 859         }
 860
 861         hir::TraitItemKind::Const(.., Some(_)) => {
 862             tcx.ensure().type_of(trait_item_id.def_id);
 863         }
 864
 865         hir::TraitItemKind::Const(..) => {
 866             tcx.ensure().type_of(trait_item_id.def_id);
 867             // Account for `const C: _;`.
 868             let mut visitor = HirPlaceholderCollector::default();
 869             visitor.visit_trait_item(trait_item);
 870             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 871         }
 872
 873         hir::TraitItemKind::Type(_, Some(_)) => {
 874             tcx.ensure().item_bounds(trait_item_id.def_id);
 875             tcx.ensure().type_of(trait_item_id.def_id);
 876             // Account for `type T = _;`.
 877             let mut visitor = HirPlaceholderCollector::default();
 878             visitor.visit_trait_item(trait_item);
 879             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 880         }
 881
 882         hir::TraitItemKind::Type(_, None) => {
 883             tcx.ensure().item_bounds(trait_item_id.def_id);
 884             // #74612: Visit and try to find bad placeholders
 885             // even if there is no concrete type.
 886             let mut visitor = HirPlaceholderCollector::default();
 887             visitor.visit_trait_item(trait_item);
 888
 889             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 890         }
 891     };
 892
 893     tcx.ensure().predicates_of(trait_item_id.def_id);
 894 }
 895
 896 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 897     let def_id = impl_item_id.def_id;
 898     tcx.ensure().generics_of(def_id);
 899     tcx.ensure().type_of(def_id);
 900     tcx.ensure().predicates_of(def_id);
 901     let impl_item = tcx.hir().impl_item(impl_item_id);
 902     match impl_item.kind {
 903         hir::ImplItemKind::Fn(..) => {
 904             tcx.ensure().fn_sig(def_id);
 905         }
 906         hir::ImplItemKind::TyAlias(_) => {
 907             // Account for `type T = _;`
 908             let mut visitor = HirPlaceholderCollector::default();
 909             visitor.visit_impl_item(impl_item);
 910
 911             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 912         }
 913         hir::ImplItemKind::Const(..) => {}
 914     }
 915 }
 916
 917 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 918     let def_id = tcx.hir().local_def_id(ctor_id);
 919     tcx.ensure().generics_of(def_id);
 920     tcx.ensure().type_of(def_id);
 921     tcx.ensure().predicates_of(def_id);
 922 }
 923
 924 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 925     let def = tcx.adt_def(def_id);
 926     let repr_type = def.repr.discr_type();
 927     let initial = repr_type.initial_discriminant(tcx);
 928     let mut prev_discr = None::<Discr<'_>>;
 929
 930     // fill the discriminant values and field types
 931     for variant in variants {
 932         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 933         prev_discr = Some(
 934             if let Some(ref e) = variant.disr_expr {
 935                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 936                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 937             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 938                 Some(discr)
 939             } else {
 940                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 941                     .span_label(
 942                         variant.span,
 943                         format!("overflowed on value after {}", prev_discr.unwrap()),
 944                     )
 945                     .note(&format!(
 946                         "explicitly set `{} = {}` if that is desired outcome",
 947                         variant.ident, wrapped_discr
 948                     ))
 949                     .emit();
 950                 None
 951             }
 952             .unwrap_or(wrapped_discr),
 953         );
 954
 955         for f in variant.data.fields() {
 956             let def_id = tcx.hir().local_def_id(f.hir_id);
 957             tcx.ensure().generics_of(def_id);
 958             tcx.ensure().type_of(def_id);
 959             tcx.ensure().predicates_of(def_id);
 960         }
 961
 962         // Convert the ctor, if any. This also registers the variant as
 963         // an item.
 964         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 965             convert_variant_ctor(tcx, ctor_hir_id);
 966         }
 967     }
 968 }
 969
 970 fn convert_variant(
 971     tcx: TyCtxt<'_>,
 972     variant_did: Option<LocalDefId>,
 973     ctor_did: Option<LocalDefId>,
 974     ident: Ident,
 975     discr: ty::VariantDiscr,
 976     def: &hir::VariantData<'_>,
 977     adt_kind: ty::AdtKind,
 978     parent_did: LocalDefId,
 979 ) -> ty::VariantDef {
 980     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 981     let fields = def
 982         .fields()
 983         .iter()
 984         .map(|f| {
 985             let fid = tcx.hir().local_def_id(f.hir_id);
 986             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 987             if let Some(prev_span) = dup_span {
 988                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 989                     field_name: f.ident,
 990                     span: f.span,
 991                     prev_span,
 992                 });
 993             } else {
 994                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 995             }
 996
 997             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 998         })
 999         .collect();
1000     let recovered = match def {
1001         hir::VariantData::Struct(_, r) => *r,
1002         _ => false,
1003     };
1004     ty::VariantDef::new(
1005         ident.name,
1006         variant_did.map(LocalDefId::to_def_id),
1007         ctor_did.map(LocalDefId::to_def_id),
1008         discr,
1009         fields,
1010         CtorKind::from_hir(def),
1011         adt_kind,
1012         parent_did.to_def_id(),
1013         recovered,
1014         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1015             || variant_did.map_or(false, |variant_did| {
1016                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1017             }),
1018     )
1019 }
1020
1021 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1022     use rustc_hir::*;
1023
1024     let def_id = def_id.expect_local();
1025     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1026     let item = match tcx.hir().get(hir_id) {
1027         Node::Item(item) => item,
1028         _ => bug!(),
1029     };
1030
1031     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1032     let (kind, variants) = match item.kind {
1033         ItemKind::Enum(ref def, _) => {
1034             let mut distance_from_explicit = 0;
1035             let variants = def
1036                 .variants
1037                 .iter()
1038                 .map(|v| {
1039                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1040                     let ctor_did =
1041                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1042
1043                     let discr = if let Some(ref e) = v.disr_expr {
1044                         distance_from_explicit = 0;
1045                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1046                     } else {
1047                         ty::VariantDiscr::Relative(distance_from_explicit)
1048                     };
1049                     distance_from_explicit += 1;
1050
1051                     convert_variant(
1052                         tcx,
1053                         variant_did,
1054                         ctor_did,
1055                         v.ident,
1056                         discr,
1057                         &v.data,
1058                         AdtKind::Enum,
1059                         def_id,
1060                     )
1061                 })
1062                 .collect();
1063
1064             (AdtKind::Enum, variants)
1065         }
1066         ItemKind::Struct(ref def, _) => {
1067             let variant_did = None::<LocalDefId>;
1068             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1069
1070             let variants = std::iter::once(convert_variant(
1071                 tcx,
1072                 variant_did,
1073                 ctor_did,
1074                 item.ident,
1075                 ty::VariantDiscr::Relative(0),
1076                 def,
1077                 AdtKind::Struct,
1078                 def_id,
1079             ))
1080             .collect();
1081
1082             (AdtKind::Struct, variants)
1083         }
1084         ItemKind::Union(ref def, _) => {
1085             let variant_did = None;
1086             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1087
1088             let variants = std::iter::once(convert_variant(
1089                 tcx,
1090                 variant_did,
1091                 ctor_did,
1092                 item.ident,
1093                 ty::VariantDiscr::Relative(0),
1094                 def,
1095                 AdtKind::Union,
1096                 def_id,
1097             ))
1098             .collect();
1099
1100             (AdtKind::Union, variants)
1101         }
1102         _ => bug!(),
1103     };
1104     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1105 }
1106
1107 /// Ensures that the super-predicates of the trait with a `DefId`
1108 /// of `trait_def_id` are converted and stored. This also ensures that
1109 /// the transitive super-predicates are converted.
1110 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1111     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1112     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1113 }
1114
1115 /// Ensures that the super-predicates of the trait with a `DefId`
1116 /// of `trait_def_id` are converted and stored. This also ensures that
1117 /// the transitive super-predicates are converted.
1118 fn super_predicates_that_define_assoc_type(
1119     tcx: TyCtxt<'_>,
1120     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1121 ) -> ty::GenericPredicates<'_> {
1122     debug!(
1123         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1124         trait_def_id, assoc_name
1125     );
1126     if trait_def_id.is_local() {
1127         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1128         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1129
1130         let item = match tcx.hir().get(trait_hir_id) {
1131             Node::Item(item) => item,
1132             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1133         };
1134
1135         let (generics, bounds) = match item.kind {
1136             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1137             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1138             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1139         };
1140
1141         let icx = ItemCtxt::new(tcx, trait_def_id);
1142
1143         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1144         let self_param_ty = tcx.types.self_param;
1145         let superbounds1 = if let Some(assoc_name) = assoc_name {
1146             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1147                 &icx,
1148                 self_param_ty,
1149                 bounds,
1150                 assoc_name,
1151             )
1152         } else {
1153             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1154         };
1155
1156         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1157
1158         // Convert any explicit superbounds in the where-clause,
1159         // e.g., `trait Foo where Self: Bar`.
1160         // In the case of trait aliases, however, we include all bounds in the where-clause,
1161         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1162         // as one of its "superpredicates".
1163         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1164         let superbounds2 = icx.type_parameter_bounds_in_generics(
1165             generics,
1166             item.hir_id(),
1167             self_param_ty,
1168             OnlySelfBounds(!is_trait_alias),
1169             assoc_name,
1170         );
1171
1172         // Combine the two lists to form the complete set of superbounds:
1173         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1174
1175         // Now require that immediate supertraits are converted,
1176         // which will, in turn, reach indirect supertraits.
1177         if assoc_name.is_none() {
1178             // Now require that immediate supertraits are converted,
1179             // which will, in turn, reach indirect supertraits.
1180             for &(pred, span) in superbounds {
1181                 debug!("superbound: {:?}", pred);
1182                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1183                     tcx.at(span).super_predicates_of(bound.def_id());
1184                 }
1185             }
1186         }
1187
1188         ty::GenericPredicates { parent: None, predicates: superbounds }
1189     } else {
1190         // if `assoc_name` is None, then the query should've been redirected to an
1191         // external provider
1192         assert!(assoc_name.is_some());
1193         tcx.super_predicates_of(trait_def_id)
1194     }
1195 }
1196
1197 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1198     let item = tcx.hir().expect_item(def_id.expect_local());
1199
1200     let (is_auto, unsafety, items) = match item.kind {
1201         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1202             (is_auto == hir::IsAuto::Yes, unsafety, items)
1203         }
1204         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1205         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1206     };
1207
1208     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1209     if paren_sugar && !tcx.features().unboxed_closures {
1210         tcx.sess
1211             .struct_span_err(
1212                 item.span,
1213                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1214                  which traits can use parenthetical notation",
1215             )
1216             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1217             .emit();
1218     }
1219
1220     let is_marker = tcx.has_attr(def_id, sym::marker);
1221     let skip_array_during_method_dispatch =
1222         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1223     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1224         ty::trait_def::TraitSpecializationKind::Marker
1225     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1226         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1227     } else {
1228         ty::trait_def::TraitSpecializationKind::None
1229     };
1230     let def_path_hash = tcx.def_path_hash(def_id);
1231
1232     let must_implement_one_of = tcx
1233         .get_attrs(def_id)
1234         .iter()
1235         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1236         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1237         // and that they are all identifiers
1238         .and_then(|attr| match attr.meta_item_list() {
1239             Some(items) if items.len() < 2 => {
1240                 tcx.sess
1241                     .struct_span_err(
1242                         attr.span,
1243                         "the `#[rustc_must_implement_one_of]` attribute must be \
1244                         used with at least 2 args",
1245                     )
1246                     .emit();
1247
1248                 None
1249             }
1250             Some(items) => items
1251                 .into_iter()
1252                 .map(|item| item.ident().ok_or(item.span()))
1253                 .collect::<Result<Box<[_]>, _>>()
1254                 .map_err(|span| {
1255                     tcx.sess
1256                         .struct_span_err(span, "must be a name of an associated function")
1257                         .emit();
1258                 })
1259                 .ok()
1260                 .zip(Some(attr.span)),
1261             // Error is reported by `rustc_attr!`
1262             None => None,
1263         })
1264         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1265         // functions in the trait with default implementations
1266         .and_then(|(list, attr_span)| {
1267             let errors = list.iter().filter_map(|ident| {
1268                 let item = items.iter().find(|item| item.ident == *ident);
1269
1270                 match item {
1271                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1272                         if !item.defaultness.has_value() {
1273                             tcx.sess
1274                                 .struct_span_err(
1275                                     item.span,
1276                                     "This function doesn't have a default implementation",
1277                                 )
1278                                 .span_note(attr_span, "required by this annotation")
1279                                 .emit();
1280
1281                             return Some(());
1282                         }
1283
1284                         return None;
1285                     }
1286                     Some(item) => tcx
1287                         .sess
1288                         .struct_span_err(item.span, "Not a function")
1289                         .span_note(attr_span, "required by this annotation")
1290                         .note(
1291                             "All `#[rustc_must_implement_one_of]` arguments \
1292                             must be associated function names",
1293                         )
1294                         .emit(),
1295                     None => tcx
1296                         .sess
1297                         .struct_span_err(ident.span, "Function not found in this trait")
1298                         .emit(),
1299                 }
1300
1301                 Some(())
1302             });
1303
1304             (errors.count() == 0).then_some(list)
1305         })
1306         // Check for duplicates
1307         .and_then(|list| {
1308             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1309             let mut no_dups = true;
1310
1311             for ident in &*list {
1312                 if let Some(dup) = set.insert(ident.name, ident.span) {
1313                     tcx.sess
1314                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1315                         .note(
1316                             "All `#[rustc_must_implement_one_of]` arguments \
1317                             must be unique",
1318                         )
1319                         .emit();
1320
1321                     no_dups = false;
1322                 }
1323             }
1324
1325             no_dups.then_some(list)
1326         });
1327
1328     ty::TraitDef::new(
1329         def_id,
1330         unsafety,
1331         paren_sugar,
1332         is_auto,
1333         is_marker,
1334         skip_array_during_method_dispatch,
1335         spec_kind,
1336         def_path_hash,
1337         must_implement_one_of,
1338     )
1339 }
1340
1341 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1342     struct LateBoundRegionsDetector<'tcx> {
1343         tcx: TyCtxt<'tcx>,
1344         outer_index: ty::DebruijnIndex,
1345         has_late_bound_regions: Option<Span>,
1346     }
1347
1348     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1349         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1350             if self.has_late_bound_regions.is_some() {
1351                 return;
1352             }
1353             match ty.kind {
1354                 hir::TyKind::BareFn(..) => {
1355                     self.outer_index.shift_in(1);
1356                     intravisit::walk_ty(self, ty);
1357                     self.outer_index.shift_out(1);
1358                 }
1359                 _ => intravisit::walk_ty(self, ty),
1360             }
1361         }
1362
1363         fn visit_poly_trait_ref(
1364             &mut self,
1365             tr: &'tcx hir::PolyTraitRef<'tcx>,
1366             m: hir::TraitBoundModifier,
1367         ) {
1368             if self.has_late_bound_regions.is_some() {
1369                 return;
1370             }
1371             self.outer_index.shift_in(1);
1372             intravisit::walk_poly_trait_ref(self, tr, m);
1373             self.outer_index.shift_out(1);
1374         }
1375
1376         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1377             if self.has_late_bound_regions.is_some() {
1378                 return;
1379             }
1380
1381             match self.tcx.named_region(lt.hir_id) {
1382                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1383                 Some(
1384                     rl::Region::LateBound(debruijn, _, _, _)
1385                     | rl::Region::LateBoundAnon(debruijn, _, _),
1386                 ) if debruijn < self.outer_index => {}
1387                 Some(
1388                     rl::Region::LateBound(..)
1389                     | rl::Region::LateBoundAnon(..)
1390                     | rl::Region::Free(..),
1391                 )
1392                 | None => {
1393                     self.has_late_bound_regions = Some(lt.span);
1394                 }
1395             }
1396         }
1397     }
1398
1399     fn has_late_bound_regions<'tcx>(
1400         tcx: TyCtxt<'tcx>,
1401         generics: &'tcx hir::Generics<'tcx>,
1402         decl: &'tcx hir::FnDecl<'tcx>,
1403     ) -> Option<Span> {
1404         let mut visitor = LateBoundRegionsDetector {
1405             tcx,
1406             outer_index: ty::INNERMOST,
1407             has_late_bound_regions: None,
1408         };
1409         for param in generics.params {
1410             if let GenericParamKind::Lifetime { .. } = param.kind {
1411                 if tcx.is_late_bound(param.hir_id) {
1412                     return Some(param.span);
1413                 }
1414             }
1415         }
1416         visitor.visit_fn_decl(decl);
1417         visitor.has_late_bound_regions
1418     }
1419
1420     match node {
1421         Node::TraitItem(item) => match item.kind {
1422             hir::TraitItemKind::Fn(ref sig, _) => {
1423                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1424             }
1425             _ => None,
1426         },
1427         Node::ImplItem(item) => match item.kind {
1428             hir::ImplItemKind::Fn(ref sig, _) => {
1429                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1430             }
1431             _ => None,
1432         },
1433         Node::ForeignItem(item) => match item.kind {
1434             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1435                 has_late_bound_regions(tcx, generics, fn_decl)
1436             }
1437             _ => None,
1438         },
1439         Node::Item(item) => match item.kind {
1440             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1441                 has_late_bound_regions(tcx, generics, sig.decl)
1442             }
1443             _ => None,
1444         },
1445         _ => None,
1446     }
1447 }
1448
1449 struct AnonConstInParamTyDetector {
1450     in_param_ty: bool,
1451     found_anon_const_in_param_ty: bool,
1452     ct: HirId,
1453 }
1454
1455 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1456     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1457         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1458             let prev = self.in_param_ty;
1459             self.in_param_ty = true;
1460             self.visit_ty(ty);
1461             self.in_param_ty = prev;
1462         }
1463     }
1464
1465     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1466         if self.in_param_ty && self.ct == c.hir_id {
1467             self.found_anon_const_in_param_ty = true;
1468         } else {
1469             intravisit::walk_anon_const(self, c)
1470         }
1471     }
1472 }
1473
1474 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1475     use rustc_hir::*;
1476
1477     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1478
1479     let node = tcx.hir().get(hir_id);
1480     let parent_def_id = match node {
1481         Node::ImplItem(_)
1482         | Node::TraitItem(_)
1483         | Node::Variant(_)
1484         | Node::Ctor(..)
1485         | Node::Field(_) => {
1486             let parent_id = tcx.hir().get_parent_item(hir_id);
1487             Some(parent_id.to_def_id())
1488         }
1489         // FIXME(#43408) always enable this once `lazy_normalization` is
1490         // stable enough and does not need a feature gate anymore.
1491         Node::AnonConst(_) => {
1492             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1493
1494             let mut in_param_ty = false;
1495             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1496                 if let Some(generics) = node.generics() {
1497                     let mut visitor = AnonConstInParamTyDetector {
1498                         in_param_ty: false,
1499                         found_anon_const_in_param_ty: false,
1500                         ct: hir_id,
1501                     };
1502
1503                     visitor.visit_generics(generics);
1504                     in_param_ty = visitor.found_anon_const_in_param_ty;
1505                     break;
1506                 }
1507             }
1508
1509             if in_param_ty {
1510                 // We do not allow generic parameters in anon consts if we are inside
1511                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1512                 None
1513             } else if tcx.lazy_normalization() {
1514                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1515                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1516                     //
1517                     // struct Foo<const N: usize = { .. }>;
1518                     //        ^^^       ^          ^^^^^^ def id of this anon const
1519                     //        ^         ^ param_id
1520                     //        ^ parent_def_id
1521                     //
1522                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1523                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1524                     //
1525                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1526                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1527                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1528                     //
1529                     // We fix this by having this function return the parent's generics ourselves and truncating the
1530                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1531                     //
1532                     // For the above code example that means we want `substs: []`
1533                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1534                     // the def id of the `{ N + 1 }` anon const
1535                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1536                     //
1537                     // This has some implications for how we get the predicates available to the anon const
1538                     // see `explicit_predicates_of` for more information on this
1539                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1540                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1541                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1542                     // In the above example this would be .params[..N#0]
1543                     let params = generics.params[..param_def_idx as usize].to_owned();
1544                     let param_def_id_to_index =
1545                         params.iter().map(|param| (param.def_id, param.index)).collect();
1546
1547                     return ty::Generics {
1548                         // we set the parent of these generics to be our parent's parent so that we
1549                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1550                         // struct Foo<const N: usize, const M: usize = { ... }>;
1551                         parent: generics.parent,
1552                         parent_count: generics.parent_count,
1553                         params,
1554                         param_def_id_to_index,
1555                         has_self: generics.has_self,
1556                         has_late_bound_regions: generics.has_late_bound_regions,
1557                     };
1558                 }
1559
1560                 // HACK(eddyb) this provides the correct generics when
1561                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1562                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1563                 //
1564                 // Note that we do not supply the parent generics when using
1565                 // `min_const_generics`.
1566                 Some(parent_def_id.to_def_id())
1567             } else {
1568                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1569                 match parent_node {
1570                     // HACK(eddyb) this provides the correct generics for repeat
1571                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1572                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1573                     // as they shouldn't be able to cause query cycle errors.
1574                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1575                         if constant.hir_id() == hir_id =>
1576                     {
1577                         Some(parent_def_id.to_def_id())
1578                     }
1579                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1580                         if constant.hir_id == hir_id =>
1581                     {
1582                         Some(parent_def_id.to_def_id())
1583                     }
1584                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1585                         Some(tcx.typeck_root_def_id(def_id))
1586                     }
1587                     _ => None,
1588                 }
1589             }
1590         }
1591         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1592             Some(tcx.typeck_root_def_id(def_id))
1593         }
1594         Node::Item(item) => match item.kind {
1595             ItemKind::OpaqueTy(hir::OpaqueTy {
1596                 origin:
1597                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1598                 ..
1599             }) => Some(fn_def_id.to_def_id()),
1600             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1601                 let parent_id = tcx.hir().get_parent_item(hir_id);
1602                 assert_ne!(parent_id, CRATE_DEF_ID);
1603                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1604                 // Opaque types are always nested within another item, and
1605                 // inherit the generics of the item.
1606                 Some(parent_id.to_def_id())
1607             }
1608             _ => None,
1609         },
1610         _ => None,
1611     };
1612
1613     let mut opt_self = None;
1614     let mut allow_defaults = false;
1615
1616     let no_generics = hir::Generics::empty();
1617     let ast_generics = match node {
1618         Node::TraitItem(item) => &item.generics,
1619
1620         Node::ImplItem(item) => &item.generics,
1621
1622         Node::Item(item) => {
1623             match item.kind {
1624                 ItemKind::Fn(.., ref generics, _)
1625                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1626
1627                 ItemKind::TyAlias(_, ref generics)
1628                 | ItemKind::Enum(_, ref generics)
1629                 | ItemKind::Struct(_, ref generics)
1630                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1631                 | ItemKind::Union(_, ref generics) => {
1632                     allow_defaults = true;
1633                     generics
1634                 }
1635
1636                 ItemKind::Trait(_, _, ref generics, ..)
1637                 | ItemKind::TraitAlias(ref generics, ..) => {
1638                     // Add in the self type parameter.
1639                     //
1640                     // Something of a hack: use the node id for the trait, also as
1641                     // the node id for the Self type parameter.
1642                     let param_id = item.def_id;
1643
1644                     opt_self = Some(ty::GenericParamDef {
1645                         index: 0,
1646                         name: kw::SelfUpper,
1647                         def_id: param_id.to_def_id(),
1648                         pure_wrt_drop: false,
1649                         kind: ty::GenericParamDefKind::Type {
1650                             has_default: false,
1651                             object_lifetime_default: rl::Set1::Empty,
1652                             synthetic: false,
1653                         },
1654                     });
1655
1656                     allow_defaults = true;
1657                     generics
1658                 }
1659
1660                 _ => &no_generics,
1661             }
1662         }
1663
1664         Node::ForeignItem(item) => match item.kind {
1665             ForeignItemKind::Static(..) => &no_generics,
1666             ForeignItemKind::Fn(_, _, ref generics) => generics,
1667             ForeignItemKind::Type => &no_generics,
1668         },
1669
1670         _ => &no_generics,
1671     };
1672
1673     let has_self = opt_self.is_some();
1674     let mut parent_has_self = false;
1675     let mut own_start = has_self as u32;
1676     let parent_count = parent_def_id.map_or(0, |def_id| {
1677         let generics = tcx.generics_of(def_id);
1678         assert!(!has_self);
1679         parent_has_self = generics.has_self;
1680         own_start = generics.count() as u32;
1681         generics.parent_count + generics.params.len()
1682     });
1683
1684     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1685
1686     if let Some(opt_self) = opt_self {
1687         params.push(opt_self);
1688     }
1689
1690     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1691     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1692         name: param.name.ident().name,
1693         index: own_start + i as u32,
1694         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1695         pure_wrt_drop: param.pure_wrt_drop,
1696         kind: ty::GenericParamDefKind::Lifetime,
1697     }));
1698
1699     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1700
1701     // Now create the real type and const parameters.
1702     let type_start = own_start - has_self as u32 + params.len() as u32;
1703     let mut i = 0;
1704
1705     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1706         GenericParamKind::Lifetime { .. } => None,
1707         GenericParamKind::Type { ref default, synthetic, .. } => {
1708             if !allow_defaults && default.is_some() {
1709                 if !tcx.features().default_type_parameter_fallback {
1710                     tcx.struct_span_lint_hir(
1711                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1712                         param.hir_id,
1713                         param.span,
1714                         |lint| {
1715                             lint.build(
1716                                 "defaults for type parameters are only allowed in \
1717                                  `struct`, `enum`, `type`, or `trait` definitions",
1718                             )
1719                             .emit();
1720                         },
1721                     );
1722                 }
1723             }
1724
1725             let kind = ty::GenericParamDefKind::Type {
1726                 has_default: default.is_some(),
1727                 object_lifetime_default: object_lifetime_defaults
1728                     .as_ref()
1729                     .map_or(rl::Set1::Empty, |o| o[i]),
1730                 synthetic,
1731             };
1732
1733             let param_def = ty::GenericParamDef {
1734                 index: type_start + i as u32,
1735                 name: param.name.ident().name,
1736                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1737                 pure_wrt_drop: param.pure_wrt_drop,
1738                 kind,
1739             };
1740             i += 1;
1741             Some(param_def)
1742         }
1743         GenericParamKind::Const { default, .. } => {
1744             if !allow_defaults && default.is_some() {
1745                 tcx.sess.span_err(
1746                     param.span,
1747                     "defaults for const parameters are only allowed in \
1748                     `struct`, `enum`, `type`, or `trait` definitions",
1749                 );
1750             }
1751
1752             let param_def = ty::GenericParamDef {
1753                 index: type_start + i as u32,
1754                 name: param.name.ident().name,
1755                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1756                 pure_wrt_drop: param.pure_wrt_drop,
1757                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1758             };
1759             i += 1;
1760             Some(param_def)
1761         }
1762     }));
1763
1764     // provide junk type parameter defs - the only place that
1765     // cares about anything but the length is instantiation,
1766     // and we don't do that for closures.
1767     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1768         let dummy_args = if gen.is_some() {
1769             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1770         } else {
1771             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1772         };
1773
1774         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1775             index: type_start + i as u32,
1776             name: Symbol::intern(arg),
1777             def_id,
1778             pure_wrt_drop: false,
1779             kind: ty::GenericParamDefKind::Type {
1780                 has_default: false,
1781                 object_lifetime_default: rl::Set1::Empty,
1782                 synthetic: false,
1783             },
1784         }));
1785     }
1786
1787     // provide junk type parameter defs for const blocks.
1788     if let Node::AnonConst(_) = node {
1789         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1790         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1791             params.push(ty::GenericParamDef {
1792                 index: type_start,
1793                 name: Symbol::intern("<const_ty>"),
1794                 def_id,
1795                 pure_wrt_drop: false,
1796                 kind: ty::GenericParamDefKind::Type {
1797                     has_default: false,
1798                     object_lifetime_default: rl::Set1::Empty,
1799                     synthetic: false,
1800                 },
1801             });
1802         }
1803     }
1804
1805     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1806
1807     ty::Generics {
1808         parent: parent_def_id,
1809         parent_count,
1810         params,
1811         param_def_id_to_index,
1812         has_self: has_self || parent_has_self,
1813         has_late_bound_regions: has_late_bound_regions(tcx, node),
1814     }
1815 }
1816
1817 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1818     generic_args.iter().any(|arg| match arg {
1819         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1820         hir::GenericArg::Infer(_) => true,
1821         _ => false,
1822     })
1823 }
1824
1825 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1826 /// use inference to provide suggestions for the appropriate type if possible.
1827 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1828     debug!(?ty);
1829     use hir::TyKind::*;
1830     match &ty.kind {
1831         Infer => true,
1832         Slice(ty) => is_suggestable_infer_ty(ty),
1833         Array(ty, length) => {
1834             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1835         }
1836         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1837         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1838         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1839         Path(hir::QPath::TypeRelative(ty, segment)) => {
1840             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1841         }
1842         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1843             ty_opt.map_or(false, is_suggestable_infer_ty)
1844                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1845         }
1846         _ => false,
1847     }
1848 }
1849
1850 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1851     if let hir::FnRetTy::Return(ty) = output {
1852         if is_suggestable_infer_ty(ty) {
1853             return Some(&*ty);
1854         }
1855     }
1856     None
1857 }
1858
1859 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1860     use rustc_hir::Node::*;
1861     use rustc_hir::*;
1862
1863     let def_id = def_id.expect_local();
1864     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1865
1866     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1867
1868     match tcx.hir().get(hir_id) {
1869         TraitItem(hir::TraitItem {
1870             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1871             ident,
1872             generics,
1873             ..
1874         })
1875         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1876         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1877             match get_infer_ret_ty(&sig.decl.output) {
1878                 Some(ty) => {
1879                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1880                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1881                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1882                         ty::ReErased => tcx.lifetimes.re_static,
1883                         _ => r,
1884                     });
1885                     let fn_sig = ty::Binder::dummy(fn_sig);
1886
1887                     let mut visitor = HirPlaceholderCollector::default();
1888                     visitor.visit_ty(ty);
1889                     let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1890                     let ret_ty = fn_sig.skip_binder().output();
1891                     if !ret_ty.references_error() {
1892                         if !ret_ty.is_closure() {
1893                             let ret_ty_str = match ret_ty.kind() {
1894                                 // Suggest a function pointer return type instead of a unique function definition
1895                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1896                                 // syntax)
1897                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1898                                 _ => ret_ty.to_string(),
1899                             };
1900                             diag.span_suggestion(
1901                                 ty.span,
1902                                 "replace with the correct return type",
1903                                 ret_ty_str,
1904                                 Applicability::MaybeIncorrect,
1905                             );
1906                         } else {
1907                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1908                             // to prevent the user from getting a papercut while trying to use the unique closure
1909                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1910                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1911                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1912                         }
1913                     }
1914                     diag.emit();
1915
1916                     fn_sig
1917                 }
1918                 None => <dyn AstConv<'_>>::ty_of_fn(
1919                     &icx,
1920                     hir_id,
1921                     sig.header.unsafety,
1922                     sig.header.abi,
1923                     sig.decl,
1924                     generics,
1925                     Some(ident.span),
1926                     None,
1927                 ),
1928             }
1929         }
1930
1931         TraitItem(hir::TraitItem {
1932             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1933             ident,
1934             generics,
1935             ..
1936         }) => <dyn AstConv<'_>>::ty_of_fn(
1937             &icx,
1938             hir_id,
1939             header.unsafety,
1940             header.abi,
1941             decl,
1942             generics,
1943             Some(ident.span),
1944             None,
1945         ),
1946
1947         ForeignItem(&hir::ForeignItem {
1948             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1949         }) => {
1950             let abi = tcx.hir().get_foreign_abi(hir_id);
1951             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1952         }
1953
1954         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1955             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1956             let inputs =
1957                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1958             ty::Binder::dummy(tcx.mk_fn_sig(
1959                 inputs,
1960                 ty,
1961                 false,
1962                 hir::Unsafety::Normal,
1963                 abi::Abi::Rust,
1964             ))
1965         }
1966
1967         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1968             // Closure signatures are not like other function
1969             // signatures and cannot be accessed through `fn_sig`. For
1970             // example, a closure signature excludes the `self`
1971             // argument. In any case they are embedded within the
1972             // closure type as part of the `ClosureSubsts`.
1973             //
1974             // To get the signature of a closure, you should use the
1975             // `sig` method on the `ClosureSubsts`:
1976             //
1977             //    substs.as_closure().sig(def_id, tcx)
1978             bug!(
1979                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1980             );
1981         }
1982
1983         x => {
1984             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1985         }
1986     }
1987 }
1988
1989 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1990     let icx = ItemCtxt::new(tcx, def_id);
1991     match tcx.hir().expect_item(def_id.expect_local()).kind {
1992         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1993             let selfty = tcx.type_of(def_id);
1994             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1995         }),
1996         _ => bug!(),
1997     }
1998 }
1999
2000 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2001     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2002     let item = tcx.hir().expect_item(def_id.expect_local());
2003     match &item.kind {
2004         hir::ItemKind::Impl(hir::Impl {
2005             polarity: hir::ImplPolarity::Negative(span),
2006             of_trait,
2007             ..
2008         }) => {
2009             if is_rustc_reservation {
2010                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2011                 tcx.sess.span_err(span, "reservation impls can't be negative");
2012             }
2013             ty::ImplPolarity::Negative
2014         }
2015         hir::ItemKind::Impl(hir::Impl {
2016             polarity: hir::ImplPolarity::Positive,
2017             of_trait: None,
2018             ..
2019         }) => {
2020             if is_rustc_reservation {
2021                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2022             }
2023             ty::ImplPolarity::Positive
2024         }
2025         hir::ItemKind::Impl(hir::Impl {
2026             polarity: hir::ImplPolarity::Positive,
2027             of_trait: Some(_),
2028             ..
2029         }) => {
2030             if is_rustc_reservation {
2031                 ty::ImplPolarity::Reservation
2032             } else {
2033                 ty::ImplPolarity::Positive
2034             }
2035         }
2036         item => bug!("impl_polarity: {:?} not an impl", item),
2037     }
2038 }
2039
2040 /// Returns the early-bound lifetimes declared in this generics
2041 /// listing. For anything other than fns/methods, this is just all
2042 /// the lifetimes that are declared. For fns or methods, we have to
2043 /// screen out those that do not appear in any where-clauses etc using
2044 /// `resolve_lifetime::early_bound_lifetimes`.
2045 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2046     tcx: TyCtxt<'tcx>,
2047     generics: &'a hir::Generics<'a>,
2048 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2049     generics.params.iter().filter(move |param| match param.kind {
2050         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2051         _ => false,
2052     })
2053 }
2054
2055 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2056 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2057 /// inferred constraints concerning which regions outlive other regions.
2058 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2059     debug!("predicates_defined_on({:?})", def_id);
2060     let mut result = tcx.explicit_predicates_of(def_id);
2061     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2062     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2063     if !inferred_outlives.is_empty() {
2064         debug!(
2065             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2066             def_id, inferred_outlives,
2067         );
2068         if result.predicates.is_empty() {
2069             result.predicates = inferred_outlives;
2070         } else {
2071             result.predicates = tcx
2072                 .arena
2073                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2074         }
2075     }
2076
2077     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2078     result
2079 }
2080
2081 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2082 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2083 /// `Self: Trait` predicates for traits.
2084 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2085     let mut result = tcx.predicates_defined_on(def_id);
2086
2087     if tcx.is_trait(def_id) {
2088         // For traits, add `Self: Trait` predicate. This is
2089         // not part of the predicates that a user writes, but it
2090         // is something that one must prove in order to invoke a
2091         // method or project an associated type.
2092         //
2093         // In the chalk setup, this predicate is not part of the
2094         // "predicates" for a trait item. But it is useful in
2095         // rustc because if you directly (e.g.) invoke a trait
2096         // method like `Trait::method(...)`, you must naturally
2097         // prove that the trait applies to the types that were
2098         // used, and adding the predicate into this list ensures
2099         // that this is done.
2100         //
2101         // We use a DUMMY_SP here as a way to signal trait bounds that come
2102         // from the trait itself that *shouldn't* be shown as the source of
2103         // an obligation and instead be skipped. Otherwise we'd use
2104         // `tcx.def_span(def_id);`
2105         let span = rustc_span::DUMMY_SP;
2106         result.predicates =
2107             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2108                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2109                 span,
2110             ))));
2111     }
2112     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2113     result
2114 }
2115
2116 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2117 /// N.B., this does not include any implied/inferred constraints.
2118 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2119     use rustc_hir::*;
2120
2121     debug!("explicit_predicates_of(def_id={:?})", def_id);
2122
2123     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2124     let node = tcx.hir().get(hir_id);
2125
2126     let mut is_trait = None;
2127     let mut is_default_impl_trait = None;
2128
2129     let icx = ItemCtxt::new(tcx, def_id);
2130
2131     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2132
2133     // We use an `IndexSet` to preserves order of insertion.
2134     // Preserving the order of insertion is important here so as not to break UI tests.
2135     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2136
2137     let ast_generics = match node {
2138         Node::TraitItem(item) => &item.generics,
2139
2140         Node::ImplItem(item) => &item.generics,
2141
2142         Node::Item(item) => {
2143             match item.kind {
2144                 ItemKind::Impl(ref impl_) => {
2145                     if impl_.defaultness.is_default() {
2146                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2147                     }
2148                     &impl_.generics
2149                 }
2150                 ItemKind::Fn(.., ref generics, _)
2151                 | ItemKind::TyAlias(_, ref generics)
2152                 | ItemKind::Enum(_, ref generics)
2153                 | ItemKind::Struct(_, ref generics)
2154                 | ItemKind::Union(_, ref generics) => generics,
2155
2156                 ItemKind::Trait(_, _, ref generics, ..) => {
2157                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2158                     generics
2159                 }
2160                 ItemKind::TraitAlias(ref generics, _) => {
2161                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2162                     generics
2163                 }
2164                 ItemKind::OpaqueTy(OpaqueTy {
2165                     origin: hir::OpaqueTyOrigin::FnReturn(..), ..
2166                 }) => {
2167                     // return-position impl trait
2168                     //
2169                     // We don't inherit predicates from the parent here:
2170                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2171                     // then the return type is `f::<'static, T>::{{opaque}}`.
2172                     //
2173                     // If we inherited the predicates of `f` then we would
2174                     // require that `T: 'static` to show that the return
2175                     // type is well-formed.
2176                     //
2177                     // The only way to have something with this opaque type
2178                     // is from the return type of the containing function,
2179                     // which will ensure that the function's predicates
2180                     // hold.
2181                     return ty::GenericPredicates { parent: None, predicates: &[] };
2182                 }
2183                 ItemKind::OpaqueTy(OpaqueTy {
2184                     ref generics,
2185                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::TyAlias,
2186                     ..
2187                 }) => {
2188                     // type-alias impl trait
2189                     generics
2190                 }
2191
2192                 _ => NO_GENERICS,
2193             }
2194         }
2195
2196         Node::ForeignItem(item) => match item.kind {
2197             ForeignItemKind::Static(..) => NO_GENERICS,
2198             ForeignItemKind::Fn(_, _, ref generics) => generics,
2199             ForeignItemKind::Type => NO_GENERICS,
2200         },
2201
2202         _ => NO_GENERICS,
2203     };
2204
2205     let generics = tcx.generics_of(def_id);
2206     let parent_count = generics.parent_count as u32;
2207     let has_own_self = generics.has_self && parent_count == 0;
2208
2209     // Below we'll consider the bounds on the type parameters (including `Self`)
2210     // and the explicit where-clauses, but to get the full set of predicates
2211     // on a trait we need to add in the supertrait bounds and bounds found on
2212     // associated types.
2213     if let Some(_trait_ref) = is_trait {
2214         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2215     }
2216
2217     // In default impls, we can assume that the self type implements
2218     // the trait. So in:
2219     //
2220     //     default impl Foo for Bar { .. }
2221     //
2222     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2223     // (see below). Recall that a default impl is not itself an impl, but rather a
2224     // set of defaults that can be incorporated into another impl.
2225     if let Some(trait_ref) = is_default_impl_trait {
2226         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2227     }
2228
2229     // Collect the region predicates that were declared inline as
2230     // well. In the case of parameters declared on a fn or method, we
2231     // have to be careful to only iterate over early-bound regions.
2232     let mut index = parent_count + has_own_self as u32;
2233     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2234         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2235             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2236             index,
2237             name: param.name.ident().name,
2238         }));
2239         index += 1;
2240
2241         match param.kind {
2242             GenericParamKind::Lifetime { .. } => {
2243                 param.bounds.iter().for_each(|bound| match bound {
2244                     hir::GenericBound::Outlives(lt) => {
2245                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2246                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2247                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2248                     }
2249                     _ => bug!(),
2250                 });
2251             }
2252             _ => bug!(),
2253         }
2254     }
2255
2256     // Collect the predicates that were written inline by the user on each
2257     // type parameter (e.g., `<T: Foo>`).
2258     for param in ast_generics.params {
2259         match param.kind {
2260             // We already dealt with early bound lifetimes above.
2261             GenericParamKind::Lifetime { .. } => (),
2262             GenericParamKind::Type { .. } => {
2263                 let name = param.name.ident().name;
2264                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2265                 index += 1;
2266
2267                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2268                 // Params are implicitly sized unless a `?Sized` bound is found
2269                 <dyn AstConv<'_>>::add_implicitly_sized(
2270                     &icx,
2271                     &mut bounds,
2272                     param.bounds,
2273                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2274                     param.span,
2275                 );
2276                 predicates.extend(bounds.predicates(tcx, param_ty));
2277             }
2278             GenericParamKind::Const { .. } => {
2279                 // Bounds on const parameters are currently not possible.
2280                 debug_assert!(param.bounds.is_empty());
2281                 index += 1;
2282             }
2283         }
2284     }
2285
2286     // Add in the bounds that appear in the where-clause.
2287     let where_clause = &ast_generics.where_clause;
2288     for predicate in where_clause.predicates {
2289         match predicate {
2290             hir::WherePredicate::BoundPredicate(bound_pred) => {
2291                 let ty = icx.to_ty(bound_pred.bounded_ty);
2292                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2293
2294                 // Keep the type around in a dummy predicate, in case of no bounds.
2295                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2296                 // is still checked for WF.
2297                 if bound_pred.bounds.is_empty() {
2298                     if let ty::Param(_) = ty.kind() {
2299                         // This is a `where T:`, which can be in the HIR from the
2300                         // transformation that moves `?Sized` to `T`'s declaration.
2301                         // We can skip the predicate because type parameters are
2302                         // trivially WF, but also we *should*, to avoid exposing
2303                         // users who never wrote `where Type:,` themselves, to
2304                         // compiler/tooling bugs from not handling WF predicates.
2305                     } else {
2306                         let span = bound_pred.bounded_ty.span;
2307                         let re_root_empty = tcx.lifetimes.re_root_empty;
2308                         let predicate = ty::Binder::bind_with_vars(
2309                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2310                                 ty,
2311                                 re_root_empty,
2312                             )),
2313                             bound_vars,
2314                         );
2315                         predicates.insert((predicate.to_predicate(tcx), span));
2316                     }
2317                 }
2318
2319                 let mut bounds = Bounds::default();
2320                 <dyn AstConv<'_>>::add_bounds(
2321                     &icx,
2322                     ty,
2323                     bound_pred.bounds.iter(),
2324                     &mut bounds,
2325                     bound_vars,
2326                 );
2327                 predicates.extend(bounds.predicates(tcx, ty));
2328             }
2329
2330             hir::WherePredicate::RegionPredicate(region_pred) => {
2331                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2332                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2333                     let (r2, span) = match bound {
2334                         hir::GenericBound::Outlives(lt) => {
2335                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2336                         }
2337                         _ => bug!(),
2338                     };
2339                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2340                         ty::OutlivesPredicate(r1, r2),
2341                     ))
2342                     .to_predicate(icx.tcx);
2343
2344                     (pred, span)
2345                 }))
2346             }
2347
2348             hir::WherePredicate::EqPredicate(..) => {
2349                 // FIXME(#20041)
2350             }
2351         }
2352     }
2353
2354     if tcx.features().generic_const_exprs {
2355         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2356     }
2357
2358     let mut predicates: Vec<_> = predicates.into_iter().collect();
2359
2360     // Subtle: before we store the predicates into the tcx, we
2361     // sort them so that predicates like `T: Foo<Item=U>` come
2362     // before uses of `U`.  This avoids false ambiguity errors
2363     // in trait checking. See `setup_constraining_predicates`
2364     // for details.
2365     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2366         let self_ty = tcx.type_of(def_id);
2367         let trait_ref = tcx.impl_trait_ref(def_id);
2368         cgp::setup_constraining_predicates(
2369             tcx,
2370             &mut predicates,
2371             trait_ref,
2372             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2373         );
2374     }
2375
2376     let result = ty::GenericPredicates {
2377         parent: generics.parent,
2378         predicates: tcx.arena.alloc_from_iter(predicates),
2379     };
2380     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2381     result
2382 }
2383
2384 fn const_evaluatable_predicates_of<'tcx>(
2385     tcx: TyCtxt<'tcx>,
2386     def_id: LocalDefId,
2387 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2388     struct ConstCollector<'tcx> {
2389         tcx: TyCtxt<'tcx>,
2390         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2391     }
2392
2393     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2394         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2395             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2396             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2397             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2398                 assert_eq!(uv.promoted, None);
2399                 let span = self.tcx.hir().span(c.hir_id);
2400                 self.preds.insert((
2401                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2402                         .to_predicate(self.tcx),
2403                     span,
2404                 ));
2405             }
2406         }
2407
2408         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2409             // Do not look into const param defaults,
2410             // these get checked when they are actually instantiated.
2411             //
2412             // We do not want the following to error:
2413             //
2414             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2415             //     struct Bar<const N: usize>(Foo<N, 3>);
2416         }
2417     }
2418
2419     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2420     let node = tcx.hir().get(hir_id);
2421
2422     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2423     if let hir::Node::Item(item) = node {
2424         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2425             if let Some(of_trait) = &impl_.of_trait {
2426                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2427                 collector.visit_trait_ref(of_trait);
2428             }
2429
2430             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2431             collector.visit_ty(impl_.self_ty);
2432         }
2433     }
2434
2435     if let Some(generics) = node.generics() {
2436         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2437         collector.visit_generics(generics);
2438     }
2439
2440     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2441         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2442         collector.visit_fn_decl(fn_sig.decl);
2443     }
2444     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2445
2446     collector.preds
2447 }
2448
2449 fn trait_explicit_predicates_and_bounds(
2450     tcx: TyCtxt<'_>,
2451     def_id: LocalDefId,
2452 ) -> ty::GenericPredicates<'_> {
2453     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2454     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2455 }
2456
2457 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2458     let def_kind = tcx.def_kind(def_id);
2459     if let DefKind::Trait = def_kind {
2460         // Remove bounds on associated types from the predicates, they will be
2461         // returned by `explicit_item_bounds`.
2462         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2463         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2464
2465         let is_assoc_item_ty = |ty: Ty<'_>| {
2466             // For a predicate from a where clause to become a bound on an
2467             // associated type:
2468             // * It must use the identity substs of the item.
2469             //     * Since any generic parameters on the item are not in scope,
2470             //       this means that the item is not a GAT, and its identity
2471             //       substs are the same as the trait's.
2472             // * It must be an associated type for this trait (*not* a
2473             //   supertrait).
2474             if let ty::Projection(projection) = ty.kind() {
2475                 projection.substs == trait_identity_substs
2476                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2477             } else {
2478                 false
2479             }
2480         };
2481
2482         let predicates: Vec<_> = predicates_and_bounds
2483             .predicates
2484             .iter()
2485             .copied()
2486             .filter(|(pred, _)| match pred.kind().skip_binder() {
2487                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2488                 ty::PredicateKind::Projection(proj) => {
2489                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2490                 }
2491                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2492                 _ => true,
2493             })
2494             .collect();
2495         if predicates.len() == predicates_and_bounds.predicates.len() {
2496             predicates_and_bounds
2497         } else {
2498             ty::GenericPredicates {
2499                 parent: predicates_and_bounds.parent,
2500                 predicates: tcx.arena.alloc_slice(&predicates),
2501             }
2502         }
2503     } else {
2504         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2505             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2506             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2507                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2508                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2509                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2510                 //
2511                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2512                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2513                 //        ^^^                                             explicit_predicates_of on
2514                 //        parent item we dont have set as the
2515                 //        parent of generics returned by `generics_of`
2516                 //
2517                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2518                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2519                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2520                 return tcx.explicit_predicates_of(item_def_id);
2521             }
2522         }
2523         gather_explicit_predicates_of(tcx, def_id)
2524     }
2525 }
2526
2527 /// Converts a specific `GenericBound` from the AST into a set of
2528 /// predicates that apply to the self type. A vector is returned
2529 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2530 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2531 /// and `<T as Bar>::X == i32`).
2532 fn predicates_from_bound<'tcx>(
2533     astconv: &dyn AstConv<'tcx>,
2534     param_ty: Ty<'tcx>,
2535     bound: &'tcx hir::GenericBound<'tcx>,
2536     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2537 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2538     let mut bounds = Bounds::default();
2539     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2540     bounds.predicates(astconv.tcx(), param_ty).collect()
2541 }
2542
2543 fn compute_sig_of_foreign_fn_decl<'tcx>(
2544     tcx: TyCtxt<'tcx>,
2545     def_id: DefId,
2546     decl: &'tcx hir::FnDecl<'tcx>,
2547     abi: abi::Abi,
2548     ident: Ident,
2549 ) -> ty::PolyFnSig<'tcx> {
2550     let unsafety = if abi == abi::Abi::RustIntrinsic {
2551         intrinsic_operation_unsafety(tcx.item_name(def_id))
2552     } else {
2553         hir::Unsafety::Unsafe
2554     };
2555     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2556     let fty = <dyn AstConv<'_>>::ty_of_fn(
2557         &ItemCtxt::new(tcx, def_id),
2558         hir_id,
2559         unsafety,
2560         abi,
2561         decl,
2562         &hir::Generics::empty(),
2563         Some(ident.span),
2564         None,
2565     );
2566
2567     // Feature gate SIMD types in FFI, since I am not sure that the
2568     // ABIs are handled at all correctly. -huonw
2569     if abi != abi::Abi::RustIntrinsic
2570         && abi != abi::Abi::PlatformIntrinsic
2571         && !tcx.features().simd_ffi
2572     {
2573         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2574             if ty.is_simd() {
2575                 let snip = tcx
2576                     .sess
2577                     .source_map()
2578                     .span_to_snippet(ast_ty.span)
2579                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2580                 tcx.sess
2581                     .struct_span_err(
2582                         ast_ty.span,
2583                         &format!(
2584                             "use of SIMD type{} in FFI is highly experimental and \
2585                              may result in invalid code",
2586                             snip
2587                         ),
2588                     )
2589                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2590                     .emit();
2591             }
2592         };
2593         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2594             check(input, ty)
2595         }
2596         if let hir::FnRetTy::Return(ref ty) = decl.output {
2597             check(ty, fty.output().skip_binder())
2598         }
2599     }
2600
2601     fty
2602 }
2603
2604 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2605     match tcx.hir().get_if_local(def_id) {
2606         Some(Node::ForeignItem(..)) => true,
2607         Some(_) => false,
2608         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2609     }
2610 }
2611
2612 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2613     match tcx.hir().get_if_local(def_id) {
2614         Some(
2615             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2616             | Node::ForeignItem(&hir::ForeignItem {
2617                 kind: hir::ForeignItemKind::Static(_, mutbl),
2618                 ..
2619             }),
2620         ) => Some(mutbl),
2621         Some(_) => None,
2622         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2623     }
2624 }
2625
2626 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2627     match tcx.hir().get_if_local(def_id) {
2628         Some(Node::Expr(&rustc_hir::Expr {
2629             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2630             ..
2631         })) => tcx.hir().body(body_id).generator_kind(),
2632         Some(_) => None,
2633         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2634     }
2635 }
2636
2637 fn from_target_feature(
2638     tcx: TyCtxt<'_>,
2639     id: DefId,
2640     attr: &ast::Attribute,
2641     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2642     target_features: &mut Vec<Symbol>,
2643 ) {
2644     let list = match attr.meta_item_list() {
2645         Some(list) => list,
2646         None => return,
2647     };
2648     let bad_item = |span| {
2649         let msg = "malformed `target_feature` attribute input";
2650         let code = "enable = \"..\"".to_owned();
2651         tcx.sess
2652             .struct_span_err(span, msg)
2653             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2654             .emit();
2655     };
2656     let rust_features = tcx.features();
2657     for item in list {
2658         // Only `enable = ...` is accepted in the meta-item list.
2659         if !item.has_name(sym::enable) {
2660             bad_item(item.span());
2661             continue;
2662         }
2663
2664         // Must be of the form `enable = "..."` (a string).
2665         let value = match item.value_str() {
2666             Some(value) => value,
2667             None => {
2668                 bad_item(item.span());
2669                 continue;
2670             }
2671         };
2672
2673         // We allow comma separation to enable multiple features.
2674         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2675             let feature_gate = match supported_target_features.get(feature) {
2676                 Some(g) => g,
2677                 None => {
2678                     let msg =
2679                         format!("the feature named `{}` is not valid for this target", feature);
2680                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2681                     err.span_label(
2682                         item.span(),
2683                         format!("`{}` is not valid for this target", feature),
2684                     );
2685                     if let Some(stripped) = feature.strip_prefix('+') {
2686                         let valid = supported_target_features.contains_key(stripped);
2687                         if valid {
2688                             err.help("consider removing the leading `+` in the feature name");
2689                         }
2690                     }
2691                     err.emit();
2692                     return None;
2693                 }
2694             };
2695
2696             // Only allow features whose feature gates have been enabled.
2697             let allowed = match feature_gate.as_ref().copied() {
2698                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2699                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2700                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2701                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2702                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2703                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2704                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2705                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2706                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2707                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2708                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2709                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2710                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2711                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2712                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2713                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2714                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2715                 Some(name) => bug!("unknown target feature gate {}", name),
2716                 None => true,
2717             };
2718             if !allowed && id.is_local() {
2719                 feature_err(
2720                     &tcx.sess.parse_sess,
2721                     feature_gate.unwrap(),
2722                     item.span(),
2723                     &format!("the target feature `{}` is currently unstable", feature),
2724                 )
2725                 .emit();
2726             }
2727             Some(Symbol::intern(feature))
2728         }));
2729     }
2730 }
2731
2732 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2733     use rustc_middle::mir::mono::Linkage::*;
2734
2735     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2736     // applicable to variable declarations and may not really make sense for
2737     // Rust code in the first place but allow them anyway and trust that the
2738     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2739     // up in the future.
2740     //
2741     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2742     // and don't have to be, LLVM treats them as no-ops.
2743     match name {
2744         "appending" => Appending,
2745         "available_externally" => AvailableExternally,
2746         "common" => Common,
2747         "extern_weak" => ExternalWeak,
2748         "external" => External,
2749         "internal" => Internal,
2750         "linkonce" => LinkOnceAny,
2751         "linkonce_odr" => LinkOnceODR,
2752         "private" => Private,
2753         "weak" => WeakAny,
2754         "weak_odr" => WeakODR,
2755         _ => {
2756             let span = tcx.hir().span_if_local(def_id);
2757             if let Some(span) = span {
2758                 tcx.sess.span_fatal(span, "invalid linkage specified")
2759             } else {
2760                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2761             }
2762         }
2763     }
2764 }
2765
2766 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2767     let attrs = tcx.get_attrs(id);
2768
2769     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2770     if tcx.should_inherit_track_caller(id) {
2771         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2772     }
2773
2774     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2775     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2776         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2777             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2778         }
2779     }
2780
2781     // The panic_no_unwind function called by TerminatorKind::Abort will never
2782     // unwind. If the panic handler that it invokes unwind then it will simply
2783     // call the panic handler again.
2784     if Some(id) == tcx.lang_items().panic_no_unwind() {
2785         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2786     }
2787
2788     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2789
2790     let mut inline_span = None;
2791     let mut link_ordinal_span = None;
2792     let mut no_sanitize_span = None;
2793     for attr in attrs.iter() {
2794         if attr.has_name(sym::cold) {
2795             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2796         } else if attr.has_name(sym::rustc_allocator) {
2797             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2798         } else if attr.has_name(sym::ffi_returns_twice) {
2799             if tcx.is_foreign_item(id) {
2800                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2801             } else {
2802                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2803                 struct_span_err!(
2804                     tcx.sess,
2805                     attr.span,
2806                     E0724,
2807                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2808                 )
2809                 .emit();
2810             }
2811         } else if attr.has_name(sym::ffi_pure) {
2812             if tcx.is_foreign_item(id) {
2813                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2814                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2815                     struct_span_err!(
2816                         tcx.sess,
2817                         attr.span,
2818                         E0757,
2819                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2820                     )
2821                     .emit();
2822                 } else {
2823                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2824                 }
2825             } else {
2826                 // `#[ffi_pure]` is only allowed on foreign functions
2827                 struct_span_err!(
2828                     tcx.sess,
2829                     attr.span,
2830                     E0755,
2831                     "`#[ffi_pure]` may only be used on foreign functions"
2832                 )
2833                 .emit();
2834             }
2835         } else if attr.has_name(sym::ffi_const) {
2836             if tcx.is_foreign_item(id) {
2837                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2838             } else {
2839                 // `#[ffi_const]` is only allowed on foreign functions
2840                 struct_span_err!(
2841                     tcx.sess,
2842                     attr.span,
2843                     E0756,
2844                     "`#[ffi_const]` may only be used on foreign functions"
2845                 )
2846                 .emit();
2847             }
2848         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2849             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2850         } else if attr.has_name(sym::naked) {
2851             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2852         } else if attr.has_name(sym::no_mangle) {
2853             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2854         } else if attr.has_name(sym::no_coverage) {
2855             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2856         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2857             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2858         } else if attr.has_name(sym::used) {
2859             let inner = attr.meta_item_list();
2860             match inner.as_deref() {
2861                 Some([item]) if item.has_name(sym::linker) => {
2862                     if !tcx.features().used_with_arg {
2863                         feature_err(
2864                             &tcx.sess.parse_sess,
2865                             sym::used_with_arg,
2866                             attr.span,
2867                             "`#[used(linker)]` is currently unstable",
2868                         )
2869                         .emit();
2870                     }
2871                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2872                 }
2873                 Some([item]) if item.has_name(sym::compiler) => {
2874                     if !tcx.features().used_with_arg {
2875                         feature_err(
2876                             &tcx.sess.parse_sess,
2877                             sym::used_with_arg,
2878                             attr.span,
2879                             "`#[used(compiler)]` is currently unstable",
2880                         )
2881                         .emit();
2882                     }
2883                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2884                 }
2885                 Some(_) => {
2886                     tcx.sess
2887                         .struct_span_err(
2888                             attr.span,
2889                             "expected `used`, `used(compiler)` or `used(linker)`",
2890                         )
2891                         .emit();
2892                 }
2893                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2894             }
2895         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2896             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2897                 struct_span_err!(
2898                     tcx.sess,
2899                     attr.span,
2900                     E0776,
2901                     "`#[cmse_nonsecure_entry]` requires C ABI"
2902                 )
2903                 .emit();
2904             }
2905             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2906                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2907                     .emit();
2908             }
2909             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2910         } else if attr.has_name(sym::thread_local) {
2911             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2912         } else if attr.has_name(sym::track_caller) {
2913             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2914                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2915                     .emit();
2916             }
2917             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2918                 feature_err(
2919                     &tcx.sess.parse_sess,
2920                     sym::closure_track_caller,
2921                     attr.span,
2922                     "`#[track_caller]` on closures is currently unstable",
2923                 )
2924                 .emit();
2925             }
2926             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2927         } else if attr.has_name(sym::export_name) {
2928             if let Some(s) = attr.value_str() {
2929                 if s.as_str().contains('\0') {
2930                     // `#[export_name = ...]` will be converted to a null-terminated string,
2931                     // so it may not contain any null characters.
2932                     struct_span_err!(
2933                         tcx.sess,
2934                         attr.span,
2935                         E0648,
2936                         "`export_name` may not contain null characters"
2937                     )
2938                     .emit();
2939                 }
2940                 codegen_fn_attrs.export_name = Some(s);
2941             }
2942         } else if attr.has_name(sym::target_feature) {
2943             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2944                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2945                     // The `#[target_feature]` attribute is allowed on
2946                     // WebAssembly targets on all functions, including safe
2947                     // ones. Other targets require that `#[target_feature]` is
2948                     // only applied to unsafe funtions (pending the
2949                     // `target_feature_11` feature) because on most targets
2950                     // execution of instructions that are not supported is
2951                     // considered undefined behavior. For WebAssembly which is a
2952                     // 100% safe target at execution time it's not possible to
2953                     // execute undefined instructions, and even if a future
2954                     // feature was added in some form for this it would be a
2955                     // deterministic trap. There is no undefined behavior when
2956                     // executing WebAssembly so `#[target_feature]` is allowed
2957                     // on safe functions (but again, only for WebAssembly)
2958                     //
2959                     // Note that this is also allowed if `actually_rustdoc` so
2960                     // if a target is documenting some wasm-specific code then
2961                     // it's not spuriously denied.
2962                 } else if !tcx.features().target_feature_11 {
2963                     let mut err = feature_err(
2964                         &tcx.sess.parse_sess,
2965                         sym::target_feature_11,
2966                         attr.span,
2967                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2968                     );
2969                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2970                     err.emit();
2971                 } else if let Some(local_id) = id.as_local() {
2972                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2973                 }
2974             }
2975             from_target_feature(
2976                 tcx,
2977                 id,
2978                 attr,
2979                 supported_target_features,
2980                 &mut codegen_fn_attrs.target_features,
2981             );
2982         } else if attr.has_name(sym::linkage) {
2983             if let Some(val) = attr.value_str() {
2984                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2985             }
2986         } else if attr.has_name(sym::link_section) {
2987             if let Some(val) = attr.value_str() {
2988                 if val.as_str().bytes().any(|b| b == 0) {
2989                     let msg = format!(
2990                         "illegal null byte in link_section \
2991                          value: `{}`",
2992                         &val
2993                     );
2994                     tcx.sess.span_err(attr.span, &msg);
2995                 } else {
2996                     codegen_fn_attrs.link_section = Some(val);
2997                 }
2998             }
2999         } else if attr.has_name(sym::link_name) {
3000             codegen_fn_attrs.link_name = attr.value_str();
3001         } else if attr.has_name(sym::link_ordinal) {
3002             link_ordinal_span = Some(attr.span);
3003             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
3004                 codegen_fn_attrs.link_ordinal = ordinal;
3005             }
3006         } else if attr.has_name(sym::no_sanitize) {
3007             no_sanitize_span = Some(attr.span);
3008             if let Some(list) = attr.meta_item_list() {
3009                 for item in list.iter() {
3010                     if item.has_name(sym::address) {
3011                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
3012                     } else if item.has_name(sym::cfi) {
3013                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
3014                     } else if item.has_name(sym::memory) {
3015                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
3016                     } else if item.has_name(sym::thread) {
3017                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
3018                     } else if item.has_name(sym::hwaddress) {
3019                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
3020                     } else {
3021                         tcx.sess
3022                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
3023                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
3024                             .emit();
3025                     }
3026                 }
3027             }
3028         } else if attr.has_name(sym::instruction_set) {
3029             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3030                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3031                     [NestedMetaItem::MetaItem(set)] => {
3032                         let segments =
3033                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3034                         match segments.as_slice() {
3035                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3036                                 if !tcx.sess.target.has_thumb_interworking {
3037                                     struct_span_err!(
3038                                         tcx.sess.diagnostic(),
3039                                         attr.span,
3040                                         E0779,
3041                                         "target does not support `#[instruction_set]`"
3042                                     )
3043                                     .emit();
3044                                     None
3045                                 } else if segments[1] == sym::a32 {
3046                                     Some(InstructionSetAttr::ArmA32)
3047                                 } else if segments[1] == sym::t32 {
3048                                     Some(InstructionSetAttr::ArmT32)
3049                                 } else {
3050                                     unreachable!()
3051                                 }
3052                             }
3053                             _ => {
3054                                 struct_span_err!(
3055                                     tcx.sess.diagnostic(),
3056                                     attr.span,
3057                                     E0779,
3058                                     "invalid instruction set specified",
3059                                 )
3060                                 .emit();
3061                                 None
3062                             }
3063                         }
3064                     }
3065                     [] => {
3066                         struct_span_err!(
3067                             tcx.sess.diagnostic(),
3068                             attr.span,
3069                             E0778,
3070                             "`#[instruction_set]` requires an argument"
3071                         )
3072                         .emit();
3073                         None
3074                     }
3075                     _ => {
3076                         struct_span_err!(
3077                             tcx.sess.diagnostic(),
3078                             attr.span,
3079                             E0779,
3080                             "cannot specify more than one instruction set"
3081                         )
3082                         .emit();
3083                         None
3084                     }
3085                 },
3086                 _ => {
3087                     struct_span_err!(
3088                         tcx.sess.diagnostic(),
3089                         attr.span,
3090                         E0778,
3091                         "must specify an instruction set"
3092                     )
3093                     .emit();
3094                     None
3095                 }
3096             };
3097         } else if attr.has_name(sym::repr) {
3098             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3099                 Some(items) => match items.as_slice() {
3100                     [item] => match item.name_value_literal() {
3101                         Some((sym::align, literal)) => {
3102                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3103
3104                             match alignment {
3105                                 Ok(align) => Some(align),
3106                                 Err(msg) => {
3107                                     struct_span_err!(
3108                                         tcx.sess.diagnostic(),
3109                                         attr.span,
3110                                         E0589,
3111                                         "invalid `repr(align)` attribute: {}",
3112                                         msg
3113                                     )
3114                                     .emit();
3115
3116                                     None
3117                                 }
3118                             }
3119                         }
3120                         _ => None,
3121                     },
3122                     [] => None,
3123                     _ => None,
3124                 },
3125                 None => None,
3126             };
3127         }
3128     }
3129
3130     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3131         if !attr.has_name(sym::inline) {
3132             return ia;
3133         }
3134         match attr.meta_kind() {
3135             Some(MetaItemKind::Word) => InlineAttr::Hint,
3136             Some(MetaItemKind::List(ref items)) => {
3137                 inline_span = Some(attr.span);
3138                 if items.len() != 1 {
3139                     struct_span_err!(
3140                         tcx.sess.diagnostic(),
3141                         attr.span,
3142                         E0534,
3143                         "expected one argument"
3144                     )
3145                     .emit();
3146                     InlineAttr::None
3147                 } else if list_contains_name(&items, sym::always) {
3148                     InlineAttr::Always
3149                 } else if list_contains_name(&items, sym::never) {
3150                     InlineAttr::Never
3151                 } else {
3152                     struct_span_err!(
3153                         tcx.sess.diagnostic(),
3154                         items[0].span(),
3155                         E0535,
3156                         "invalid argument"
3157                     )
3158                     .emit();
3159
3160                     InlineAttr::None
3161                 }
3162             }
3163             Some(MetaItemKind::NameValue(_)) => ia,
3164             None => ia,
3165         }
3166     });
3167
3168     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3169         if !attr.has_name(sym::optimize) {
3170             return ia;
3171         }
3172         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3173         match attr.meta_kind() {
3174             Some(MetaItemKind::Word) => {
3175                 err(attr.span, "expected one argument");
3176                 ia
3177             }
3178             Some(MetaItemKind::List(ref items)) => {
3179                 inline_span = Some(attr.span);
3180                 if items.len() != 1 {
3181                     err(attr.span, "expected one argument");
3182                     OptimizeAttr::None
3183                 } else if list_contains_name(&items, sym::size) {
3184                     OptimizeAttr::Size
3185                 } else if list_contains_name(&items, sym::speed) {
3186                     OptimizeAttr::Speed
3187                 } else {
3188                     err(items[0].span(), "invalid argument");
3189                     OptimizeAttr::None
3190                 }
3191             }
3192             Some(MetaItemKind::NameValue(_)) => ia,
3193             None => ia,
3194         }
3195     });
3196
3197     // #73631: closures inherit `#[target_feature]` annotations
3198     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3199         let owner_id = tcx.parent(id).expect("closure should have a parent");
3200         codegen_fn_attrs
3201             .target_features
3202             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3203     }
3204
3205     // If a function uses #[target_feature] it can't be inlined into general
3206     // purpose functions as they wouldn't have the right target features
3207     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3208     // respected.
3209     if !codegen_fn_attrs.target_features.is_empty() {
3210         if codegen_fn_attrs.inline == InlineAttr::Always {
3211             if let Some(span) = inline_span {
3212                 tcx.sess.span_err(
3213                     span,
3214                     "cannot use `#[inline(always)]` with \
3215                      `#[target_feature]`",
3216                 );
3217             }
3218         }
3219     }
3220
3221     if !codegen_fn_attrs.no_sanitize.is_empty() {
3222         if codegen_fn_attrs.inline == InlineAttr::Always {
3223             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3224                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3225                 tcx.struct_span_lint_hir(
3226                     lint::builtin::INLINE_NO_SANITIZE,
3227                     hir_id,
3228                     no_sanitize_span,
3229                     |lint| {
3230                         lint.build("`no_sanitize` will have no effect after inlining")
3231                             .span_note(inline_span, "inlining requested here")
3232                             .emit();
3233                     },
3234                 )
3235             }
3236         }
3237     }
3238
3239     // Weak lang items have the same semantics as "std internal" symbols in the
3240     // sense that they're preserved through all our LTO passes and only
3241     // strippable by the linker.
3242     //
3243     // Additionally weak lang items have predetermined symbol names.
3244     if tcx.is_weak_lang_item(id) {
3245         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3246     }
3247     if let Some(name) = weak_lang_items::link_name(attrs) {
3248         codegen_fn_attrs.export_name = Some(name);
3249         codegen_fn_attrs.link_name = Some(name);
3250     }
3251     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3252
3253     // Internal symbols to the standard library all have no_mangle semantics in
3254     // that they have defined symbol names present in the function name. This
3255     // also applies to weak symbols where they all have known symbol names.
3256     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3257         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3258     }
3259
3260     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3261     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3262     // intrinsic functions.
3263     if let Some(name) = &codegen_fn_attrs.link_name {
3264         if name.as_str().starts_with("llvm.") {
3265             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3266         }
3267     }
3268
3269     codegen_fn_attrs
3270 }
3271
3272 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3273 /// applied to the method prototype.
3274 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3275     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3276         if let ty::AssocItemContainer::ImplContainer(_) = impl_item.container {
3277             if let Some(trait_item) = impl_item.trait_item_def_id {
3278                 return tcx
3279                     .codegen_fn_attrs(trait_item)
3280                     .flags
3281                     .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3282             }
3283         }
3284     }
3285
3286     false
3287 }
3288
3289 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3290     use rustc_ast::{Lit, LitIntType, LitKind};
3291     let meta_item_list = attr.meta_item_list();
3292     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3293     let sole_meta_list = match meta_item_list {
3294         Some([item]) => item.literal(),
3295         Some(_) => {
3296             tcx.sess
3297                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3298                 .note("the attribute requires exactly one argument")
3299                 .emit();
3300             return None;
3301         }
3302         _ => None,
3303     };
3304     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3305         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3306         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3307         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3308         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3309         //
3310         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3311         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3312         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3313         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3314         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3315         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3316         // about LINK.EXE failing.)
3317         if *ordinal <= u16::MAX as u128 {
3318             Some(*ordinal as u16)
3319         } else {
3320             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3321             tcx.sess
3322                 .struct_span_err(attr.span, &msg)
3323                 .note("the value may not exceed `u16::MAX`")
3324                 .emit();
3325             None
3326         }
3327     } else {
3328         tcx.sess
3329             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3330             .note("an unsuffixed integer value, e.g., `1`, is expected")
3331             .emit();
3332         None
3333     }
3334 }
3335
3336 fn check_link_name_xor_ordinal(
3337     tcx: TyCtxt<'_>,
3338     codegen_fn_attrs: &CodegenFnAttrs,
3339     inline_span: Option<Span>,
3340 ) {
3341     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3342         return;
3343     }
3344     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3345     if let Some(span) = inline_span {
3346         tcx.sess.span_err(span, msg);
3347     } else {
3348         tcx.sess.err(msg);
3349     }
3350 }
3351
3352 /// Checks the function annotated with `#[target_feature]` is not a safe
3353 /// trait method implementation, reporting an error if it is.
3354 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3355     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3356     let node = tcx.hir().get(hir_id);
3357     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3358         let parent_id = tcx.hir().get_parent_item(hir_id);
3359         let parent_item = tcx.hir().expect_item(parent_id);
3360         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3361             tcx.sess
3362                 .struct_span_err(
3363                     attr_span,
3364                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3365                 )
3366                 .span_label(attr_span, "cannot be applied to safe trait method")
3367                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3368                 .emit();
3369         }
3370     }
3371 }