compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind};
  31 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::nested_filter;
  36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  37 use rustc_middle::mir::mono::Linkage;
  38 use rustc_middle::ty::query::Providers;
  39 use rustc_middle::ty::subst::InternalSubsts;
  40 use rustc_middle::ty::util::Discr;
  41 use rustc_middle::ty::util::IntTypeExt;
  42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  43 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50 use std::iter;
  51
  52 mod item_bounds;
  53 mod type_of;
  54
  55 struct OnlySelfBounds(bool);
  56
  57 ///////////////////////////////////////////////////////////////////////////
  58 // Main entry point
  59
  60 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  61     tcx.hir().visit_item_likes_in_module(
  62         module_def_id,
  63         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  64     );
  65 }
  66
  67 pub fn provide(providers: &mut Providers) {
  68     *providers = Providers {
  69         opt_const_param_of: type_of::opt_const_param_of,
  70         type_of: type_of::type_of,
  71         item_bounds: item_bounds::item_bounds,
  72         explicit_item_bounds: item_bounds::explicit_item_bounds,
  73         generics_of,
  74         predicates_of,
  75         predicates_defined_on,
  76         explicit_predicates_of,
  77         super_predicates_of,
  78         super_predicates_that_define_assoc_type,
  79         trait_explicit_predicates_and_bounds,
  80         type_param_predicates,
  81         trait_def,
  82         adt_def,
  83         fn_sig,
  84         impl_trait_ref,
  85         impl_polarity,
  86         is_foreign_item,
  87         static_mutability,
  88         generator_kind,
  89         codegen_fn_attrs,
  90         collect_mod_item_types,
  91         should_inherit_track_caller,
  92         ..*providers
  93     };
  94 }
  95
  96 ///////////////////////////////////////////////////////////////////////////
  97
  98 /// Context specific to some particular item. This is what implements
  99 /// `AstConv`. It has information about the predicates that are defined
 100 /// on the trait. Unfortunately, this predicate information is
 101 /// available in various different forms at various points in the
 102 /// process. So we can't just store a pointer to e.g., the AST or the
 103 /// parsed ty form, we have to be more flexible. To this end, the
 104 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 105 /// `get_type_parameter_bounds` requests, drawing the information from
 106 /// the AST (`hir::Generics`), recursively.
 107 pub struct ItemCtxt<'tcx> {
 108     tcx: TyCtxt<'tcx>,
 109     item_def_id: DefId,
 110 }
 111
 112 ///////////////////////////////////////////////////////////////////////////
 113
 114 #[derive(Default)]
 115 crate struct HirPlaceholderCollector(crate Vec<Span>);
 116
 117 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 118     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 119         if let hir::TyKind::Infer = t.kind {
 120             self.0.push(t.span);
 121         }
 122         intravisit::walk_ty(self, t)
 123     }
 124     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 125         match generic_arg {
 126             hir::GenericArg::Infer(inf) => {
 127                 self.0.push(inf.span);
 128                 intravisit::walk_inf(self, inf);
 129             }
 130             hir::GenericArg::Type(t) => self.visit_ty(t),
 131             _ => {}
 132         }
 133     }
 134     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 135         if let &hir::ArrayLen::Infer(_, span) = length {
 136             self.0.push(span);
 137         }
 138         intravisit::walk_array_len(self, length)
 139     }
 140 }
 141
 142 struct CollectItemTypesVisitor<'tcx> {
 143     tcx: TyCtxt<'tcx>,
 144 }
 145
 146 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 147 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 148 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 149 crate fn placeholder_type_error<'tcx>(
 150     tcx: TyCtxt<'tcx>,
 151     span: Option<Span>,
 152     generics: &[hir::GenericParam<'_>],
 153     placeholder_types: Vec<Span>,
 154     suggest: bool,
 155     hir_ty: Option<&hir::Ty<'_>>,
 156     kind: &'static str,
 157 ) {
 158     if placeholder_types.is_empty() {
 159         return;
 160     }
 161
 162     let type_name = generics.next_type_param_name(None);
 163     let mut sugg: Vec<_> =
 164         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 165
 166     if generics.is_empty() {
 167         if let Some(span) = span {
 168             sugg.push((span, format!("<{}>", type_name)));
 169         }
 170     } else if let Some(arg) = generics
 171         .iter()
 172         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 173     {
 174         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 175         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 176         sugg.push((arg.span, (*type_name).to_string()));
 177     } else {
 178         let last = generics.iter().last().unwrap();
 179         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 180         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 181         sugg.push((span, format!(", {}", type_name)));
 182     }
 183
 184     let mut err = bad_placeholder(tcx, placeholder_types, kind);
 185
 186     // Suggest, but only if it is not a function in const or static
 187     if suggest {
 188         let mut is_fn = false;
 189         let mut is_const_or_static = false;
 190
 191         if let Some(hir_ty) = hir_ty {
 192             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 193                 is_fn = true;
 194
 195                 // Check if parent is const or static
 196                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 197                 let parent_node = tcx.hir().get(parent_id);
 198
 199                 is_const_or_static = matches!(
 200                     parent_node,
 201                     Node::Item(&hir::Item {
 202                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 203                         ..
 204                     }) | Node::TraitItem(&hir::TraitItem {
 205                         kind: hir::TraitItemKind::Const(..),
 206                         ..
 207                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 208                 );
 209             }
 210         }
 211
 212         // if function is wrapped around a const or static,
 213         // then don't show the suggestion
 214         if !(is_fn && is_const_or_static) {
 215             err.multipart_suggestion(
 216                 "use type parameters instead",
 217                 sugg,
 218                 Applicability::HasPlaceholders,
 219             );
 220         }
 221     }
 222     err.emit();
 223 }
 224
 225 fn reject_placeholder_type_signatures_in_item<'tcx>(
 226     tcx: TyCtxt<'tcx>,
 227     item: &'tcx hir::Item<'tcx>,
 228 ) {
 229     let (generics, suggest) = match &item.kind {
 230         hir::ItemKind::Union(_, generics)
 231         | hir::ItemKind::Enum(_, generics)
 232         | hir::ItemKind::TraitAlias(generics, _)
 233         | hir::ItemKind::Trait(_, _, generics, ..)
 234         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 235         | hir::ItemKind::Struct(_, generics) => (generics, true),
 236         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 237         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 238         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 239         _ => return,
 240     };
 241
 242     let mut visitor = HirPlaceholderCollector::default();
 243     visitor.visit_item(item);
 244
 245     placeholder_type_error(
 246         tcx,
 247         Some(generics.span),
 248         generics.params,
 249         visitor.0,
 250         suggest,
 251         None,
 252         item.kind.descr(),
 253     );
 254 }
 255
 256 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 257     type NestedFilter = nested_filter::OnlyBodies;
 258
 259     fn nested_visit_map(&mut self) -> Self::Map {
 260         self.tcx.hir()
 261     }
 262
 263     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 264         convert_item(self.tcx, item.item_id());
 265         reject_placeholder_type_signatures_in_item(self.tcx, item);
 266         intravisit::walk_item(self, item);
 267     }
 268
 269     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 270         for param in generics.params {
 271             match param.kind {
 272                 hir::GenericParamKind::Lifetime { .. } => {}
 273                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 274                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 275                     self.tcx.ensure().type_of(def_id);
 276                 }
 277                 hir::GenericParamKind::Type { .. } => {}
 278                 hir::GenericParamKind::Const { default, .. } => {
 279                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 280                     self.tcx.ensure().type_of(def_id);
 281                     if let Some(default) = default {
 282                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 283                         // need to store default and type of default
 284                         self.tcx.ensure().type_of(default_def_id);
 285                         self.tcx.ensure().const_param_default(def_id);
 286                     }
 287                 }
 288             }
 289         }
 290         intravisit::walk_generics(self, generics);
 291     }
 292
 293     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 294         if let hir::ExprKind::Closure(..) = expr.kind {
 295             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 296             self.tcx.ensure().generics_of(def_id);
 297             // We do not call `type_of` for closures here as that
 298             // depends on typecheck and would therefore hide
 299             // any further errors in case one typeck fails.
 300         }
 301         intravisit::walk_expr(self, expr);
 302     }
 303
 304     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 305         convert_trait_item(self.tcx, trait_item.trait_item_id());
 306         intravisit::walk_trait_item(self, trait_item);
 307     }
 308
 309     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 310         convert_impl_item(self.tcx, impl_item.impl_item_id());
 311         intravisit::walk_impl_item(self, impl_item);
 312     }
 313 }
 314
 315 ///////////////////////////////////////////////////////////////////////////
 316 // Utility types and common code for the above passes.
 317
 318 fn bad_placeholder<'tcx>(
 319     tcx: TyCtxt<'tcx>,
 320     mut spans: Vec<Span>,
 321     kind: &'static str,
 322 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 323     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 324
 325     spans.sort();
 326     let mut err = struct_span_err!(
 327         tcx.sess,
 328         spans.clone(),
 329         E0121,
 330         "the placeholder `_` is not allowed within types on item signatures for {}",
 331         kind
 332     );
 333     for span in spans {
 334         err.span_label(span, "not allowed in type signatures");
 335     }
 336     err
 337 }
 338
 339 impl<'tcx> ItemCtxt<'tcx> {
 340     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 341         ItemCtxt { tcx, item_def_id }
 342     }
 343
 344     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 345         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 346     }
 347
 348     pub fn hir_id(&self) -> hir::HirId {
 349         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 350     }
 351
 352     pub fn node(&self) -> hir::Node<'tcx> {
 353         self.tcx.hir().get(self.hir_id())
 354     }
 355 }
 356
 357 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 358     fn tcx(&self) -> TyCtxt<'tcx> {
 359         self.tcx
 360     }
 361
 362     fn item_def_id(&self) -> Option<DefId> {
 363         Some(self.item_def_id)
 364     }
 365
 366     fn get_type_parameter_bounds(
 367         &self,
 368         span: Span,
 369         def_id: DefId,
 370         assoc_name: Ident,
 371     ) -> ty::GenericPredicates<'tcx> {
 372         self.tcx.at(span).type_param_predicates((
 373             self.item_def_id,
 374             def_id.expect_local(),
 375             assoc_name,
 376         ))
 377     }
 378
 379     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 380         None
 381     }
 382
 383     fn allow_ty_infer(&self) -> bool {
 384         false
 385     }
 386
 387     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 388         self.tcx().ty_error_with_message(span, "bad placeholder type")
 389     }
 390
 391     fn ct_infer(
 392         &self,
 393         ty: Ty<'tcx>,
 394         _: Option<&ty::GenericParamDef>,
 395         span: Span,
 396     ) -> &'tcx Const<'tcx> {
 397         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 398             ty::ReErased => self.tcx.lifetimes.re_static,
 399             _ => r,
 400         });
 401         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 402     }
 403
 404     fn projected_ty_from_poly_trait_ref(
 405         &self,
 406         span: Span,
 407         item_def_id: DefId,
 408         item_segment: &hir::PathSegment<'_>,
 409         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 410     ) -> Ty<'tcx> {
 411         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 412             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 413                 self,
 414                 self.tcx,
 415                 span,
 416                 item_def_id,
 417                 item_segment,
 418                 trait_ref.substs,
 419             );
 420             self.tcx().mk_projection(item_def_id, item_substs)
 421         } else {
 422             // There are no late-bound regions; we can just ignore the binder.
 423             let mut err = struct_span_err!(
 424                 self.tcx().sess,
 425                 span,
 426                 E0212,
 427                 "cannot use the associated type of a trait \
 428                  with uninferred generic parameters"
 429             );
 430
 431             match self.node() {
 432                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 433                     let item =
 434                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 435                     match &item.kind {
 436                         hir::ItemKind::Enum(_, generics)
 437                         | hir::ItemKind::Struct(_, generics)
 438                         | hir::ItemKind::Union(_, generics) => {
 439                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 440                             let (lt_sp, sugg) = match generics.params {
 441                                 [] => (generics.span, format!("<{}>", lt_name)),
 442                                 [bound, ..] => {
 443                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 444                                 }
 445                             };
 446                             let suggestions = vec![
 447                                 (lt_sp, sugg),
 448                                 (
 449                                     span.with_hi(item_segment.ident.span.lo()),
 450                                     format!(
 451                                         "{}::",
 452                                         // Replace the existing lifetimes with a new named lifetime.
 453                                         self.tcx
 454                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 455                                                 self.tcx.mk_region(ty::ReEarlyBound(
 456                                                     ty::EarlyBoundRegion {
 457                                                         def_id: item_def_id,
 458                                                         index: 0,
 459                                                         name: Symbol::intern(&lt_name),
 460                                                     },
 461                                                 ))
 462                                             })
 463                                             .0,
 464                                     ),
 465                                 ),
 466                             ];
 467                             err.multipart_suggestion(
 468                                 "use a fully qualified path with explicit lifetimes",
 469                                 suggestions,
 470                                 Applicability::MaybeIncorrect,
 471                             );
 472                         }
 473                         _ => {}
 474                     }
 475                 }
 476                 hir::Node::Item(hir::Item {
 477                     kind:
 478                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 479                     ..
 480                 }) => {}
 481                 hir::Node::Item(_)
 482                 | hir::Node::ForeignItem(_)
 483                 | hir::Node::TraitItem(_)
 484                 | hir::Node::ImplItem(_) => {
 485                     err.span_suggestion_verbose(
 486                         span.with_hi(item_segment.ident.span.lo()),
 487                         "use a fully qualified path with inferred lifetimes",
 488                         format!(
 489                             "{}::",
 490                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 491                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 492                         ),
 493                         Applicability::MaybeIncorrect,
 494                     );
 495                 }
 496                 _ => {}
 497             }
 498             err.emit();
 499             self.tcx().ty_error()
 500         }
 501     }
 502
 503     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 504         // Types in item signatures are not normalized to avoid undue dependencies.
 505         ty
 506     }
 507
 508     fn set_tainted_by_errors(&self) {
 509         // There's no obvious place to track this, so just let it go.
 510     }
 511
 512     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 513         // There's no place to record types from signatures?
 514     }
 515 }
 516
 517 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 518 fn get_new_lifetime_name<'tcx>(
 519     tcx: TyCtxt<'tcx>,
 520     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 521     generics: &hir::Generics<'tcx>,
 522 ) -> String {
 523     let existing_lifetimes = tcx
 524         .collect_referenced_late_bound_regions(&poly_trait_ref)
 525         .into_iter()
 526         .filter_map(|lt| {
 527             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 528                 Some(name.as_str().to_string())
 529             } else {
 530                 None
 531             }
 532         })
 533         .chain(generics.params.iter().filter_map(|param| {
 534             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 535                 Some(param.name.ident().as_str().to_string())
 536             } else {
 537                 None
 538             }
 539         }))
 540         .collect::<FxHashSet<String>>();
 541
 542     let a_to_z_repeat_n = |n| {
 543         (b'a'..=b'z').map(move |c| {
 544             let mut s = '\''.to_string();
 545             s.extend(std::iter::repeat(char::from(c)).take(n));
 546             s
 547         })
 548     };
 549
 550     // If all single char lifetime names are present, we wrap around and double the chars.
 551     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 552 }
 553
 554 /// Returns the predicates defined on `item_def_id` of the form
 555 /// `X: Foo` where `X` is the type parameter `def_id`.
 556 fn type_param_predicates(
 557     tcx: TyCtxt<'_>,
 558     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 559 ) -> ty::GenericPredicates<'_> {
 560     use rustc_hir::*;
 561
 562     // In the AST, bounds can derive from two places. Either
 563     // written inline like `<T: Foo>` or in a where-clause like
 564     // `where T: Foo`.
 565
 566     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 567     let param_owner = tcx.hir().ty_param_owner(param_id);
 568     let generics = tcx.generics_of(param_owner);
 569     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 570     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 571
 572     // Don't look for bounds where the type parameter isn't in scope.
 573     let parent = if item_def_id == param_owner.to_def_id() {
 574         None
 575     } else {
 576         tcx.generics_of(item_def_id).parent
 577     };
 578
 579     let mut result = parent
 580         .map(|parent| {
 581             let icx = ItemCtxt::new(tcx, parent);
 582             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 583         })
 584         .unwrap_or_default();
 585     let mut extend = None;
 586
 587     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 588     let ast_generics = match tcx.hir().get(item_hir_id) {
 589         Node::TraitItem(item) => &item.generics,
 590
 591         Node::ImplItem(item) => &item.generics,
 592
 593         Node::Item(item) => {
 594             match item.kind {
 595                 ItemKind::Fn(.., ref generics, _)
 596                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 597                 | ItemKind::TyAlias(_, ref generics)
 598                 | ItemKind::OpaqueTy(OpaqueTy {
 599                     ref generics,
 600                     origin: hir::OpaqueTyOrigin::TyAlias,
 601                     ..
 602                 })
 603                 | ItemKind::Enum(_, ref generics)
 604                 | ItemKind::Struct(_, ref generics)
 605                 | ItemKind::Union(_, ref generics) => generics,
 606                 ItemKind::Trait(_, _, ref generics, ..) => {
 607                     // Implied `Self: Trait` and supertrait bounds.
 608                     if param_id == item_hir_id {
 609                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 610                         extend =
 611                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 612                     }
 613                     generics
 614                 }
 615                 _ => return result,
 616             }
 617         }
 618
 619         Node::ForeignItem(item) => match item.kind {
 620             ForeignItemKind::Fn(_, _, ref generics) => generics,
 621             _ => return result,
 622         },
 623
 624         _ => return result,
 625     };
 626
 627     let icx = ItemCtxt::new(tcx, item_def_id);
 628     let extra_predicates = extend.into_iter().chain(
 629         icx.type_parameter_bounds_in_generics(
 630             ast_generics,
 631             param_id,
 632             ty,
 633             OnlySelfBounds(true),
 634             Some(assoc_name),
 635         )
 636         .into_iter()
 637         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 638             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 639             _ => false,
 640         }),
 641     );
 642     result.predicates =
 643         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 644     result
 645 }
 646
 647 impl<'tcx> ItemCtxt<'tcx> {
 648     /// Finds bounds from `hir::Generics`. This requires scanning through the
 649     /// AST. We do this to avoid having to convert *all* the bounds, which
 650     /// would create artificial cycles. Instead, we can only convert the
 651     /// bounds for a type parameter `X` if `X::Foo` is used.
 652     fn type_parameter_bounds_in_generics(
 653         &self,
 654         ast_generics: &'tcx hir::Generics<'tcx>,
 655         param_id: hir::HirId,
 656         ty: Ty<'tcx>,
 657         only_self_bounds: OnlySelfBounds,
 658         assoc_name: Option<Ident>,
 659     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 660         let from_ty_params = ast_generics
 661             .params
 662             .iter()
 663             .filter_map(|param| match param.kind {
 664                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 665                     if param.hir_id == param_id =>
 666                 {
 667                     Some(&param.bounds)
 668                 }
 669                 _ => None,
 670             })
 671             .flat_map(|bounds| bounds.iter())
 672             .filter(|b| match assoc_name {
 673                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 674                 None => true,
 675             })
 676             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 677
 678         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 679         let from_where_clauses = ast_generics
 680             .where_clause
 681             .predicates
 682             .iter()
 683             .filter_map(|wp| match *wp {
 684                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 685                 _ => None,
 686             })
 687             .flat_map(|bp| {
 688                 let bt = if bp.is_param_bound(param_def_id) {
 689                     Some(ty)
 690                 } else if !only_self_bounds.0 {
 691                     Some(self.to_ty(bp.bounded_ty))
 692                 } else {
 693                     None
 694                 };
 695                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 696
 697                 bp.bounds
 698                     .iter()
 699                     .filter(|b| match assoc_name {
 700                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 701                         None => true,
 702                     })
 703                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 704             })
 705             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 706
 707         from_ty_params.chain(from_where_clauses).collect()
 708     }
 709
 710     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 711         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 712
 713         match b {
 714             hir::GenericBound::Trait(poly_trait_ref, _) => {
 715                 let trait_ref = &poly_trait_ref.trait_ref;
 716                 if let Some(trait_did) = trait_ref.trait_def_id() {
 717                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 718                 } else {
 719                     false
 720                 }
 721             }
 722             _ => false,
 723         }
 724     }
 725 }
 726
 727 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 728     let it = tcx.hir().item(item_id);
 729     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 730     let def_id = item_id.def_id;
 731
 732     match it.kind {
 733         // These don't define types.
 734         hir::ItemKind::ExternCrate(_)
 735         | hir::ItemKind::Use(..)
 736         | hir::ItemKind::Macro(_)
 737         | hir::ItemKind::Mod(_)
 738         | hir::ItemKind::GlobalAsm(_) => {}
 739         hir::ItemKind::ForeignMod { items, .. } => {
 740             for item in items {
 741                 let item = tcx.hir().foreign_item(item.id);
 742                 tcx.ensure().generics_of(item.def_id);
 743                 tcx.ensure().type_of(item.def_id);
 744                 tcx.ensure().predicates_of(item.def_id);
 745                 match item.kind {
 746                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 747                     hir::ForeignItemKind::Static(..) => {
 748                         let mut visitor = HirPlaceholderCollector::default();
 749                         visitor.visit_foreign_item(item);
 750                         placeholder_type_error(
 751                             tcx,
 752                             None,
 753                             &[],
 754                             visitor.0,
 755                             false,
 756                             None,
 757                             "static variable",
 758                         );
 759                     }
 760                     _ => (),
 761                 }
 762             }
 763         }
 764         hir::ItemKind::Enum(ref enum_definition, _) => {
 765             tcx.ensure().generics_of(def_id);
 766             tcx.ensure().type_of(def_id);
 767             tcx.ensure().predicates_of(def_id);
 768             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 769         }
 770         hir::ItemKind::Impl { .. } => {
 771             tcx.ensure().generics_of(def_id);
 772             tcx.ensure().type_of(def_id);
 773             tcx.ensure().impl_trait_ref(def_id);
 774             tcx.ensure().predicates_of(def_id);
 775         }
 776         hir::ItemKind::Trait(..) => {
 777             tcx.ensure().generics_of(def_id);
 778             tcx.ensure().trait_def(def_id);
 779             tcx.at(it.span).super_predicates_of(def_id);
 780             tcx.ensure().predicates_of(def_id);
 781         }
 782         hir::ItemKind::TraitAlias(..) => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.at(it.span).super_predicates_of(def_id);
 785             tcx.ensure().predicates_of(def_id);
 786         }
 787         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 788             tcx.ensure().generics_of(def_id);
 789             tcx.ensure().type_of(def_id);
 790             tcx.ensure().predicates_of(def_id);
 791
 792             for f in struct_def.fields() {
 793                 let def_id = tcx.hir().local_def_id(f.hir_id);
 794                 tcx.ensure().generics_of(def_id);
 795                 tcx.ensure().type_of(def_id);
 796                 tcx.ensure().predicates_of(def_id);
 797             }
 798
 799             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 800                 convert_variant_ctor(tcx, ctor_hir_id);
 801             }
 802         }
 803
 804         // Desugared from `impl Trait`, so visited by the function's return type.
 805         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 806             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 807             ..
 808         }) => {}
 809
 810         // Don't call `type_of` on opaque types, since that depends on type
 811         // checking function bodies. `check_item_type` ensures that it's called
 812         // instead.
 813         hir::ItemKind::OpaqueTy(..) => {
 814             tcx.ensure().generics_of(def_id);
 815             tcx.ensure().predicates_of(def_id);
 816             tcx.ensure().explicit_item_bounds(def_id);
 817         }
 818         hir::ItemKind::TyAlias(..)
 819         | hir::ItemKind::Static(..)
 820         | hir::ItemKind::Const(..)
 821         | hir::ItemKind::Fn(..) => {
 822             tcx.ensure().generics_of(def_id);
 823             tcx.ensure().type_of(def_id);
 824             tcx.ensure().predicates_of(def_id);
 825             match it.kind {
 826                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 827                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 828                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 829                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 830                     if let hir::TyKind::TraitObject(..) = ty.kind {
 831                         let mut visitor = HirPlaceholderCollector::default();
 832                         visitor.visit_item(it);
 833                         placeholder_type_error(
 834                             tcx,
 835                             None,
 836                             &[],
 837                             visitor.0,
 838                             false,
 839                             None,
 840                             it.kind.descr(),
 841                         );
 842                     }
 843                 }
 844                 _ => (),
 845             }
 846         }
 847     }
 848 }
 849
 850 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 851     let trait_item = tcx.hir().trait_item(trait_item_id);
 852     tcx.ensure().generics_of(trait_item_id.def_id);
 853
 854     match trait_item.kind {
 855         hir::TraitItemKind::Fn(..) => {
 856             tcx.ensure().type_of(trait_item_id.def_id);
 857             tcx.ensure().fn_sig(trait_item_id.def_id);
 858         }
 859
 860         hir::TraitItemKind::Const(.., Some(_)) => {
 861             tcx.ensure().type_of(trait_item_id.def_id);
 862         }
 863
 864         hir::TraitItemKind::Const(..) => {
 865             tcx.ensure().type_of(trait_item_id.def_id);
 866             // Account for `const C: _;`.
 867             let mut visitor = HirPlaceholderCollector::default();
 868             visitor.visit_trait_item(trait_item);
 869             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 870         }
 871
 872         hir::TraitItemKind::Type(_, Some(_)) => {
 873             tcx.ensure().item_bounds(trait_item_id.def_id);
 874             tcx.ensure().type_of(trait_item_id.def_id);
 875             // Account for `type T = _;`.
 876             let mut visitor = HirPlaceholderCollector::default();
 877             visitor.visit_trait_item(trait_item);
 878             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 879         }
 880
 881         hir::TraitItemKind::Type(_, None) => {
 882             tcx.ensure().item_bounds(trait_item_id.def_id);
 883             // #74612: Visit and try to find bad placeholders
 884             // even if there is no concrete type.
 885             let mut visitor = HirPlaceholderCollector::default();
 886             visitor.visit_trait_item(trait_item);
 887
 888             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 889         }
 890     };
 891
 892     tcx.ensure().predicates_of(trait_item_id.def_id);
 893 }
 894
 895 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 896     let def_id = impl_item_id.def_id;
 897     tcx.ensure().generics_of(def_id);
 898     tcx.ensure().type_of(def_id);
 899     tcx.ensure().predicates_of(def_id);
 900     let impl_item = tcx.hir().impl_item(impl_item_id);
 901     match impl_item.kind {
 902         hir::ImplItemKind::Fn(..) => {
 903             tcx.ensure().fn_sig(def_id);
 904         }
 905         hir::ImplItemKind::TyAlias(_) => {
 906             // Account for `type T = _;`
 907             let mut visitor = HirPlaceholderCollector::default();
 908             visitor.visit_impl_item(impl_item);
 909
 910             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 911         }
 912         hir::ImplItemKind::Const(..) => {}
 913     }
 914 }
 915
 916 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 917     let def_id = tcx.hir().local_def_id(ctor_id);
 918     tcx.ensure().generics_of(def_id);
 919     tcx.ensure().type_of(def_id);
 920     tcx.ensure().predicates_of(def_id);
 921 }
 922
 923 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 924     let def = tcx.adt_def(def_id);
 925     let repr_type = def.repr.discr_type();
 926     let initial = repr_type.initial_discriminant(tcx);
 927     let mut prev_discr = None::<Discr<'_>>;
 928
 929     // fill the discriminant values and field types
 930     for variant in variants {
 931         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 932         prev_discr = Some(
 933             if let Some(ref e) = variant.disr_expr {
 934                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 935                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 936             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 937                 Some(discr)
 938             } else {
 939                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 940                     .span_label(
 941                         variant.span,
 942                         format!("overflowed on value after {}", prev_discr.unwrap()),
 943                     )
 944                     .note(&format!(
 945                         "explicitly set `{} = {}` if that is desired outcome",
 946                         variant.ident, wrapped_discr
 947                     ))
 948                     .emit();
 949                 None
 950             }
 951             .unwrap_or(wrapped_discr),
 952         );
 953
 954         for f in variant.data.fields() {
 955             let def_id = tcx.hir().local_def_id(f.hir_id);
 956             tcx.ensure().generics_of(def_id);
 957             tcx.ensure().type_of(def_id);
 958             tcx.ensure().predicates_of(def_id);
 959         }
 960
 961         // Convert the ctor, if any. This also registers the variant as
 962         // an item.
 963         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 964             convert_variant_ctor(tcx, ctor_hir_id);
 965         }
 966     }
 967 }
 968
 969 fn convert_variant(
 970     tcx: TyCtxt<'_>,
 971     variant_did: Option<LocalDefId>,
 972     ctor_did: Option<LocalDefId>,
 973     ident: Ident,
 974     discr: ty::VariantDiscr,
 975     def: &hir::VariantData<'_>,
 976     adt_kind: ty::AdtKind,
 977     parent_did: LocalDefId,
 978 ) -> ty::VariantDef {
 979     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 980     let fields = def
 981         .fields()
 982         .iter()
 983         .map(|f| {
 984             let fid = tcx.hir().local_def_id(f.hir_id);
 985             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 986             if let Some(prev_span) = dup_span {
 987                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 988                     field_name: f.ident,
 989                     span: f.span,
 990                     prev_span,
 991                 });
 992             } else {
 993                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 994             }
 995
 996             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 997         })
 998         .collect();
 999     let recovered = match def {
1000         hir::VariantData::Struct(_, r) => *r,
1001         _ => false,
1002     };
1003     ty::VariantDef::new(
1004         ident.name,
1005         variant_did.map(LocalDefId::to_def_id),
1006         ctor_did.map(LocalDefId::to_def_id),
1007         discr,
1008         fields,
1009         CtorKind::from_hir(def),
1010         adt_kind,
1011         parent_did.to_def_id(),
1012         recovered,
1013         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1014             || variant_did.map_or(false, |variant_did| {
1015                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1016             }),
1017     )
1018 }
1019
1020 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1021     use rustc_hir::*;
1022
1023     let def_id = def_id.expect_local();
1024     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1025     let item = match tcx.hir().get(hir_id) {
1026         Node::Item(item) => item,
1027         _ => bug!(),
1028     };
1029
1030     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1031     let (kind, variants) = match item.kind {
1032         ItemKind::Enum(ref def, _) => {
1033             let mut distance_from_explicit = 0;
1034             let variants = def
1035                 .variants
1036                 .iter()
1037                 .map(|v| {
1038                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1039                     let ctor_did =
1040                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1041
1042                     let discr = if let Some(ref e) = v.disr_expr {
1043                         distance_from_explicit = 0;
1044                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1045                     } else {
1046                         ty::VariantDiscr::Relative(distance_from_explicit)
1047                     };
1048                     distance_from_explicit += 1;
1049
1050                     convert_variant(
1051                         tcx,
1052                         variant_did,
1053                         ctor_did,
1054                         v.ident,
1055                         discr,
1056                         &v.data,
1057                         AdtKind::Enum,
1058                         def_id,
1059                     )
1060                 })
1061                 .collect();
1062
1063             (AdtKind::Enum, variants)
1064         }
1065         ItemKind::Struct(ref def, _) => {
1066             let variant_did = None::<LocalDefId>;
1067             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1068
1069             let variants = std::iter::once(convert_variant(
1070                 tcx,
1071                 variant_did,
1072                 ctor_did,
1073                 item.ident,
1074                 ty::VariantDiscr::Relative(0),
1075                 def,
1076                 AdtKind::Struct,
1077                 def_id,
1078             ))
1079             .collect();
1080
1081             (AdtKind::Struct, variants)
1082         }
1083         ItemKind::Union(ref def, _) => {
1084             let variant_did = None;
1085             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1086
1087             let variants = std::iter::once(convert_variant(
1088                 tcx,
1089                 variant_did,
1090                 ctor_did,
1091                 item.ident,
1092                 ty::VariantDiscr::Relative(0),
1093                 def,
1094                 AdtKind::Union,
1095                 def_id,
1096             ))
1097             .collect();
1098
1099             (AdtKind::Union, variants)
1100         }
1101         _ => bug!(),
1102     };
1103     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1104 }
1105
1106 /// Ensures that the super-predicates of the trait with a `DefId`
1107 /// of `trait_def_id` are converted and stored. This also ensures that
1108 /// the transitive super-predicates are converted.
1109 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1110     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1111     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1112 }
1113
1114 /// Ensures that the super-predicates of the trait with a `DefId`
1115 /// of `trait_def_id` are converted and stored. This also ensures that
1116 /// the transitive super-predicates are converted.
1117 fn super_predicates_that_define_assoc_type(
1118     tcx: TyCtxt<'_>,
1119     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1120 ) -> ty::GenericPredicates<'_> {
1121     debug!(
1122         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1123         trait_def_id, assoc_name
1124     );
1125     if trait_def_id.is_local() {
1126         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1127         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1128
1129         let item = match tcx.hir().get(trait_hir_id) {
1130             Node::Item(item) => item,
1131             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1132         };
1133
1134         let (generics, bounds) = match item.kind {
1135             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1136             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1137             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1138         };
1139
1140         let icx = ItemCtxt::new(tcx, trait_def_id);
1141
1142         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1143         let self_param_ty = tcx.types.self_param;
1144         let superbounds1 = if let Some(assoc_name) = assoc_name {
1145             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1146                 &icx,
1147                 self_param_ty,
1148                 bounds,
1149                 assoc_name,
1150             )
1151         } else {
1152             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1153         };
1154
1155         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1156
1157         // Convert any explicit superbounds in the where-clause,
1158         // e.g., `trait Foo where Self: Bar`.
1159         // In the case of trait aliases, however, we include all bounds in the where-clause,
1160         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1161         // as one of its "superpredicates".
1162         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1163         let superbounds2 = icx.type_parameter_bounds_in_generics(
1164             generics,
1165             item.hir_id(),
1166             self_param_ty,
1167             OnlySelfBounds(!is_trait_alias),
1168             assoc_name,
1169         );
1170
1171         // Combine the two lists to form the complete set of superbounds:
1172         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1173
1174         // Now require that immediate supertraits are converted,
1175         // which will, in turn, reach indirect supertraits.
1176         if assoc_name.is_none() {
1177             // Now require that immediate supertraits are converted,
1178             // which will, in turn, reach indirect supertraits.
1179             for &(pred, span) in superbounds {
1180                 debug!("superbound: {:?}", pred);
1181                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1182                     tcx.at(span).super_predicates_of(bound.def_id());
1183                 }
1184             }
1185         }
1186
1187         ty::GenericPredicates { parent: None, predicates: superbounds }
1188     } else {
1189         // if `assoc_name` is None, then the query should've been redirected to an
1190         // external provider
1191         assert!(assoc_name.is_some());
1192         tcx.super_predicates_of(trait_def_id)
1193     }
1194 }
1195
1196 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1197     let item = tcx.hir().expect_item(def_id.expect_local());
1198
1199     let (is_auto, unsafety, items) = match item.kind {
1200         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1201             (is_auto == hir::IsAuto::Yes, unsafety, items)
1202         }
1203         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1204         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1205     };
1206
1207     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1208     if paren_sugar && !tcx.features().unboxed_closures {
1209         tcx.sess
1210             .struct_span_err(
1211                 item.span,
1212                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1213                  which traits can use parenthetical notation",
1214             )
1215             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1216             .emit();
1217     }
1218
1219     let is_marker = tcx.has_attr(def_id, sym::marker);
1220     let skip_array_during_method_dispatch =
1221         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1222     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1223         ty::trait_def::TraitSpecializationKind::Marker
1224     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1225         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1226     } else {
1227         ty::trait_def::TraitSpecializationKind::None
1228     };
1229     let def_path_hash = tcx.def_path_hash(def_id);
1230
1231     let must_implement_one_of = tcx
1232         .get_attrs(def_id)
1233         .iter()
1234         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1235         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1236         // and that they are all identifiers
1237         .and_then(|attr| match attr.meta_item_list() {
1238             Some(items) if items.len() < 2 => {
1239                 tcx.sess
1240                     .struct_span_err(
1241                         attr.span,
1242                         "the `#[rustc_must_implement_one_of]` attribute must be \
1243                         used with at least 2 args",
1244                     )
1245                     .emit();
1246
1247                 None
1248             }
1249             Some(items) => items
1250                 .into_iter()
1251                 .map(|item| item.ident().ok_or(item.span()))
1252                 .collect::<Result<Box<[_]>, _>>()
1253                 .map_err(|span| {
1254                     tcx.sess
1255                         .struct_span_err(span, "must be a name of an associated function")
1256                         .emit();
1257                 })
1258                 .ok()
1259                 .zip(Some(attr.span)),
1260             // Error is reported by `rustc_attr!`
1261             None => None,
1262         })
1263         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1264         // functions in the trait with default implementations
1265         .and_then(|(list, attr_span)| {
1266             let errors = list.iter().filter_map(|ident| {
1267                 let item = items.iter().find(|item| item.ident == *ident);
1268
1269                 match item {
1270                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1271                         if !item.defaultness.has_value() {
1272                             tcx.sess
1273                                 .struct_span_err(
1274                                     item.span,
1275                                     "This function doesn't have a default implementation",
1276                                 )
1277                                 .span_note(attr_span, "required by this annotation")
1278                                 .emit();
1279
1280                             return Some(());
1281                         }
1282
1283                         return None;
1284                     }
1285                     Some(item) => tcx
1286                         .sess
1287                         .struct_span_err(item.span, "Not a function")
1288                         .span_note(attr_span, "required by this annotation")
1289                         .note(
1290                             "All `#[rustc_must_implement_one_of]` arguments \
1291                             must be associated function names",
1292                         )
1293                         .emit(),
1294                     None => tcx
1295                         .sess
1296                         .struct_span_err(ident.span, "Function not found in this trait")
1297                         .emit(),
1298                 }
1299
1300                 Some(())
1301             });
1302
1303             (errors.count() == 0).then_some(list)
1304         })
1305         // Check for duplicates
1306         .and_then(|list| {
1307             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1308             let mut no_dups = true;
1309
1310             for ident in &*list {
1311                 if let Some(dup) = set.insert(ident.name, ident.span) {
1312                     tcx.sess
1313                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1314                         .note(
1315                             "All `#[rustc_must_implement_one_of]` arguments \
1316                             must be unique",
1317                         )
1318                         .emit();
1319
1320                     no_dups = false;
1321                 }
1322             }
1323
1324             no_dups.then_some(list)
1325         });
1326
1327     ty::TraitDef::new(
1328         def_id,
1329         unsafety,
1330         paren_sugar,
1331         is_auto,
1332         is_marker,
1333         skip_array_during_method_dispatch,
1334         spec_kind,
1335         def_path_hash,
1336         must_implement_one_of,
1337     )
1338 }
1339
1340 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1341     struct LateBoundRegionsDetector<'tcx> {
1342         tcx: TyCtxt<'tcx>,
1343         outer_index: ty::DebruijnIndex,
1344         has_late_bound_regions: Option<Span>,
1345     }
1346
1347     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1348         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1349             if self.has_late_bound_regions.is_some() {
1350                 return;
1351             }
1352             match ty.kind {
1353                 hir::TyKind::BareFn(..) => {
1354                     self.outer_index.shift_in(1);
1355                     intravisit::walk_ty(self, ty);
1356                     self.outer_index.shift_out(1);
1357                 }
1358                 _ => intravisit::walk_ty(self, ty),
1359             }
1360         }
1361
1362         fn visit_poly_trait_ref(
1363             &mut self,
1364             tr: &'tcx hir::PolyTraitRef<'tcx>,
1365             m: hir::TraitBoundModifier,
1366         ) {
1367             if self.has_late_bound_regions.is_some() {
1368                 return;
1369             }
1370             self.outer_index.shift_in(1);
1371             intravisit::walk_poly_trait_ref(self, tr, m);
1372             self.outer_index.shift_out(1);
1373         }
1374
1375         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1376             if self.has_late_bound_regions.is_some() {
1377                 return;
1378             }
1379
1380             match self.tcx.named_region(lt.hir_id) {
1381                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1382                 Some(
1383                     rl::Region::LateBound(debruijn, _, _, _)
1384                     | rl::Region::LateBoundAnon(debruijn, _, _),
1385                 ) if debruijn < self.outer_index => {}
1386                 Some(
1387                     rl::Region::LateBound(..)
1388                     | rl::Region::LateBoundAnon(..)
1389                     | rl::Region::Free(..),
1390                 )
1391                 | None => {
1392                     self.has_late_bound_regions = Some(lt.span);
1393                 }
1394             }
1395         }
1396     }
1397
1398     fn has_late_bound_regions<'tcx>(
1399         tcx: TyCtxt<'tcx>,
1400         generics: &'tcx hir::Generics<'tcx>,
1401         decl: &'tcx hir::FnDecl<'tcx>,
1402     ) -> Option<Span> {
1403         let mut visitor = LateBoundRegionsDetector {
1404             tcx,
1405             outer_index: ty::INNERMOST,
1406             has_late_bound_regions: None,
1407         };
1408         for param in generics.params {
1409             if let GenericParamKind::Lifetime { .. } = param.kind {
1410                 if tcx.is_late_bound(param.hir_id) {
1411                     return Some(param.span);
1412                 }
1413             }
1414         }
1415         visitor.visit_fn_decl(decl);
1416         visitor.has_late_bound_regions
1417     }
1418
1419     match node {
1420         Node::TraitItem(item) => match item.kind {
1421             hir::TraitItemKind::Fn(ref sig, _) => {
1422                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1423             }
1424             _ => None,
1425         },
1426         Node::ImplItem(item) => match item.kind {
1427             hir::ImplItemKind::Fn(ref sig, _) => {
1428                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1429             }
1430             _ => None,
1431         },
1432         Node::ForeignItem(item) => match item.kind {
1433             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1434                 has_late_bound_regions(tcx, generics, fn_decl)
1435             }
1436             _ => None,
1437         },
1438         Node::Item(item) => match item.kind {
1439             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1440                 has_late_bound_regions(tcx, generics, sig.decl)
1441             }
1442             _ => None,
1443         },
1444         _ => None,
1445     }
1446 }
1447
1448 struct AnonConstInParamTyDetector {
1449     in_param_ty: bool,
1450     found_anon_const_in_param_ty: bool,
1451     ct: HirId,
1452 }
1453
1454 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1455     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1456         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1457             let prev = self.in_param_ty;
1458             self.in_param_ty = true;
1459             self.visit_ty(ty);
1460             self.in_param_ty = prev;
1461         }
1462     }
1463
1464     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1465         if self.in_param_ty && self.ct == c.hir_id {
1466             self.found_anon_const_in_param_ty = true;
1467         } else {
1468             intravisit::walk_anon_const(self, c)
1469         }
1470     }
1471 }
1472
1473 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1474     use rustc_hir::*;
1475
1476     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1477
1478     let node = tcx.hir().get(hir_id);
1479     let parent_def_id = match node {
1480         Node::ImplItem(_)
1481         | Node::TraitItem(_)
1482         | Node::Variant(_)
1483         | Node::Ctor(..)
1484         | Node::Field(_) => {
1485             let parent_id = tcx.hir().get_parent_item(hir_id);
1486             Some(parent_id.to_def_id())
1487         }
1488         // FIXME(#43408) always enable this once `lazy_normalization` is
1489         // stable enough and does not need a feature gate anymore.
1490         Node::AnonConst(_) => {
1491             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1492
1493             let mut in_param_ty = false;
1494             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1495                 if let Some(generics) = node.generics() {
1496                     let mut visitor = AnonConstInParamTyDetector {
1497                         in_param_ty: false,
1498                         found_anon_const_in_param_ty: false,
1499                         ct: hir_id,
1500                     };
1501
1502                     visitor.visit_generics(generics);
1503                     in_param_ty = visitor.found_anon_const_in_param_ty;
1504                     break;
1505                 }
1506             }
1507
1508             if in_param_ty {
1509                 // We do not allow generic parameters in anon consts if we are inside
1510                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1511                 None
1512             } else if tcx.lazy_normalization() {
1513                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1514                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1515                     //
1516                     // struct Foo<const N: usize = { .. }>;
1517                     //        ^^^       ^          ^^^^^^ def id of this anon const
1518                     //        ^         ^ param_id
1519                     //        ^ parent_def_id
1520                     //
1521                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1522                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1523                     //
1524                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1525                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1526                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1527                     //
1528                     // We fix this by having this function return the parent's generics ourselves and truncating the
1529                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1530                     //
1531                     // For the above code example that means we want `substs: []`
1532                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1533                     // the def id of the `{ N + 1 }` anon const
1534                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1535                     //
1536                     // This has some implications for how we get the predicates available to the anon const
1537                     // see `explicit_predicates_of` for more information on this
1538                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1539                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1540                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1541                     // In the above example this would be .params[..N#0]
1542                     let params = generics.params[..param_def_idx as usize].to_owned();
1543                     let param_def_id_to_index =
1544                         params.iter().map(|param| (param.def_id, param.index)).collect();
1545
1546                     return ty::Generics {
1547                         // we set the parent of these generics to be our parent's parent so that we
1548                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1549                         // struct Foo<const N: usize, const M: usize = { ... }>;
1550                         parent: generics.parent,
1551                         parent_count: generics.parent_count,
1552                         params,
1553                         param_def_id_to_index,
1554                         has_self: generics.has_self,
1555                         has_late_bound_regions: generics.has_late_bound_regions,
1556                     };
1557                 }
1558
1559                 // HACK(eddyb) this provides the correct generics when
1560                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1561                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1562                 //
1563                 // Note that we do not supply the parent generics when using
1564                 // `min_const_generics`.
1565                 Some(parent_def_id.to_def_id())
1566             } else {
1567                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1568                 match parent_node {
1569                     // HACK(eddyb) this provides the correct generics for repeat
1570                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1571                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1572                     // as they shouldn't be able to cause query cycle errors.
1573                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1574                         if constant.hir_id() == hir_id =>
1575                     {
1576                         Some(parent_def_id.to_def_id())
1577                     }
1578                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1579                         if constant.hir_id == hir_id =>
1580                     {
1581                         Some(parent_def_id.to_def_id())
1582                     }
1583                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1584                         Some(tcx.typeck_root_def_id(def_id))
1585                     }
1586                     _ => None,
1587                 }
1588             }
1589         }
1590         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1591             Some(tcx.typeck_root_def_id(def_id))
1592         }
1593         Node::Item(item) => match item.kind {
1594             ItemKind::OpaqueTy(hir::OpaqueTy {
1595                 origin:
1596                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1597                 ..
1598             }) => Some(fn_def_id.to_def_id()),
1599             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1600                 let parent_id = tcx.hir().get_parent_item(hir_id);
1601                 assert_ne!(parent_id, CRATE_DEF_ID);
1602                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1603                 // Opaque types are always nested within another item, and
1604                 // inherit the generics of the item.
1605                 Some(parent_id.to_def_id())
1606             }
1607             _ => None,
1608         },
1609         _ => None,
1610     };
1611
1612     let mut opt_self = None;
1613     let mut allow_defaults = false;
1614
1615     let no_generics = hir::Generics::empty();
1616     let ast_generics = match node {
1617         Node::TraitItem(item) => &item.generics,
1618
1619         Node::ImplItem(item) => &item.generics,
1620
1621         Node::Item(item) => {
1622             match item.kind {
1623                 ItemKind::Fn(.., ref generics, _)
1624                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1625
1626                 ItemKind::TyAlias(_, ref generics)
1627                 | ItemKind::Enum(_, ref generics)
1628                 | ItemKind::Struct(_, ref generics)
1629                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1630                 | ItemKind::Union(_, ref generics) => {
1631                     allow_defaults = true;
1632                     generics
1633                 }
1634
1635                 ItemKind::Trait(_, _, ref generics, ..)
1636                 | ItemKind::TraitAlias(ref generics, ..) => {
1637                     // Add in the self type parameter.
1638                     //
1639                     // Something of a hack: use the node id for the trait, also as
1640                     // the node id for the Self type parameter.
1641                     let param_id = item.def_id;
1642
1643                     opt_self = Some(ty::GenericParamDef {
1644                         index: 0,
1645                         name: kw::SelfUpper,
1646                         def_id: param_id.to_def_id(),
1647                         pure_wrt_drop: false,
1648                         kind: ty::GenericParamDefKind::Type {
1649                             has_default: false,
1650                             object_lifetime_default: rl::Set1::Empty,
1651                             synthetic: false,
1652                         },
1653                     });
1654
1655                     allow_defaults = true;
1656                     generics
1657                 }
1658
1659                 _ => &no_generics,
1660             }
1661         }
1662
1663         Node::ForeignItem(item) => match item.kind {
1664             ForeignItemKind::Static(..) => &no_generics,
1665             ForeignItemKind::Fn(_, _, ref generics) => generics,
1666             ForeignItemKind::Type => &no_generics,
1667         },
1668
1669         _ => &no_generics,
1670     };
1671
1672     let has_self = opt_self.is_some();
1673     let mut parent_has_self = false;
1674     let mut own_start = has_self as u32;
1675     let parent_count = parent_def_id.map_or(0, |def_id| {
1676         let generics = tcx.generics_of(def_id);
1677         assert!(!has_self);
1678         parent_has_self = generics.has_self;
1679         own_start = generics.count() as u32;
1680         generics.parent_count + generics.params.len()
1681     });
1682
1683     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1684
1685     if let Some(opt_self) = opt_self {
1686         params.push(opt_self);
1687     }
1688
1689     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1690     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1691         name: param.name.ident().name,
1692         index: own_start + i as u32,
1693         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1694         pure_wrt_drop: param.pure_wrt_drop,
1695         kind: ty::GenericParamDefKind::Lifetime,
1696     }));
1697
1698     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1699
1700     // Now create the real type and const parameters.
1701     let type_start = own_start - has_self as u32 + params.len() as u32;
1702     let mut i = 0;
1703
1704     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1705         GenericParamKind::Lifetime { .. } => None,
1706         GenericParamKind::Type { ref default, synthetic, .. } => {
1707             if !allow_defaults && default.is_some() {
1708                 if !tcx.features().default_type_parameter_fallback {
1709                     tcx.struct_span_lint_hir(
1710                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1711                         param.hir_id,
1712                         param.span,
1713                         |lint| {
1714                             lint.build(
1715                                 "defaults for type parameters are only allowed in \
1716                                  `struct`, `enum`, `type`, or `trait` definitions",
1717                             )
1718                             .emit();
1719                         },
1720                     );
1721                 }
1722             }
1723
1724             let kind = ty::GenericParamDefKind::Type {
1725                 has_default: default.is_some(),
1726                 object_lifetime_default: object_lifetime_defaults
1727                     .as_ref()
1728                     .map_or(rl::Set1::Empty, |o| o[i]),
1729                 synthetic,
1730             };
1731
1732             let param_def = ty::GenericParamDef {
1733                 index: type_start + i as u32,
1734                 name: param.name.ident().name,
1735                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1736                 pure_wrt_drop: param.pure_wrt_drop,
1737                 kind,
1738             };
1739             i += 1;
1740             Some(param_def)
1741         }
1742         GenericParamKind::Const { default, .. } => {
1743             if !allow_defaults && default.is_some() {
1744                 tcx.sess.span_err(
1745                     param.span,
1746                     "defaults for const parameters are only allowed in \
1747                     `struct`, `enum`, `type`, or `trait` definitions",
1748                 );
1749             }
1750
1751             let param_def = ty::GenericParamDef {
1752                 index: type_start + i as u32,
1753                 name: param.name.ident().name,
1754                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1755                 pure_wrt_drop: param.pure_wrt_drop,
1756                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1757             };
1758             i += 1;
1759             Some(param_def)
1760         }
1761     }));
1762
1763     // provide junk type parameter defs - the only place that
1764     // cares about anything but the length is instantiation,
1765     // and we don't do that for closures.
1766     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1767         let dummy_args = if gen.is_some() {
1768             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1769         } else {
1770             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1771         };
1772
1773         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1774             index: type_start + i as u32,
1775             name: Symbol::intern(arg),
1776             def_id,
1777             pure_wrt_drop: false,
1778             kind: ty::GenericParamDefKind::Type {
1779                 has_default: false,
1780                 object_lifetime_default: rl::Set1::Empty,
1781                 synthetic: false,
1782             },
1783         }));
1784     }
1785
1786     // provide junk type parameter defs for const blocks.
1787     if let Node::AnonConst(_) = node {
1788         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1789         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1790             params.push(ty::GenericParamDef {
1791                 index: type_start,
1792                 name: Symbol::intern("<const_ty>"),
1793                 def_id,
1794                 pure_wrt_drop: false,
1795                 kind: ty::GenericParamDefKind::Type {
1796                     has_default: false,
1797                     object_lifetime_default: rl::Set1::Empty,
1798                     synthetic: false,
1799                 },
1800             });
1801         }
1802     }
1803
1804     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1805
1806     ty::Generics {
1807         parent: parent_def_id,
1808         parent_count,
1809         params,
1810         param_def_id_to_index,
1811         has_self: has_self || parent_has_self,
1812         has_late_bound_regions: has_late_bound_regions(tcx, node),
1813     }
1814 }
1815
1816 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1817     generic_args.iter().any(|arg| match arg {
1818         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1819         hir::GenericArg::Infer(_) => true,
1820         _ => false,
1821     })
1822 }
1823
1824 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1825 /// use inference to provide suggestions for the appropriate type if possible.
1826 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1827     debug!(?ty);
1828     use hir::TyKind::*;
1829     match &ty.kind {
1830         Infer => true,
1831         Slice(ty) => is_suggestable_infer_ty(ty),
1832         Array(ty, length) => {
1833             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1834         }
1835         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1836         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1837         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1838         Path(hir::QPath::TypeRelative(ty, segment)) => {
1839             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1840         }
1841         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1842             ty_opt.map_or(false, is_suggestable_infer_ty)
1843                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1844         }
1845         _ => false,
1846     }
1847 }
1848
1849 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1850     if let hir::FnRetTy::Return(ty) = output {
1851         if is_suggestable_infer_ty(ty) {
1852             return Some(&*ty);
1853         }
1854     }
1855     None
1856 }
1857
1858 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1859     use rustc_hir::Node::*;
1860     use rustc_hir::*;
1861
1862     let def_id = def_id.expect_local();
1863     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1864
1865     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1866
1867     match tcx.hir().get(hir_id) {
1868         TraitItem(hir::TraitItem {
1869             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1870             ident,
1871             generics,
1872             ..
1873         })
1874         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1875         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1876             match get_infer_ret_ty(&sig.decl.output) {
1877                 Some(ty) => {
1878                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1879                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1880                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1881                         ty::ReErased => tcx.lifetimes.re_static,
1882                         _ => r,
1883                     });
1884                     let fn_sig = ty::Binder::dummy(fn_sig);
1885
1886                     let mut visitor = HirPlaceholderCollector::default();
1887                     visitor.visit_ty(ty);
1888                     let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1889                     let ret_ty = fn_sig.skip_binder().output();
1890                     if !ret_ty.references_error() {
1891                         if !ret_ty.is_closure() {
1892                             let ret_ty_str = match ret_ty.kind() {
1893                                 // Suggest a function pointer return type instead of a unique function definition
1894                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1895                                 // syntax)
1896                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1897                                 _ => ret_ty.to_string(),
1898                             };
1899                             diag.span_suggestion(
1900                                 ty.span,
1901                                 "replace with the correct return type",
1902                                 ret_ty_str,
1903                                 Applicability::MaybeIncorrect,
1904                             );
1905                         } else {
1906                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1907                             // to prevent the user from getting a papercut while trying to use the unique closure
1908                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1909                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1910                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1911                         }
1912                     }
1913                     diag.emit();
1914
1915                     fn_sig
1916                 }
1917                 None => <dyn AstConv<'_>>::ty_of_fn(
1918                     &icx,
1919                     hir_id,
1920                     sig.header.unsafety,
1921                     sig.header.abi,
1922                     sig.decl,
1923                     generics,
1924                     Some(ident.span),
1925                     None,
1926                 ),
1927             }
1928         }
1929
1930         TraitItem(hir::TraitItem {
1931             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1932             ident,
1933             generics,
1934             ..
1935         }) => <dyn AstConv<'_>>::ty_of_fn(
1936             &icx,
1937             hir_id,
1938             header.unsafety,
1939             header.abi,
1940             decl,
1941             generics,
1942             Some(ident.span),
1943             None,
1944         ),
1945
1946         ForeignItem(&hir::ForeignItem {
1947             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1948         }) => {
1949             let abi = tcx.hir().get_foreign_abi(hir_id);
1950             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1951         }
1952
1953         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1954             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1955             let inputs =
1956                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1957             ty::Binder::dummy(tcx.mk_fn_sig(
1958                 inputs,
1959                 ty,
1960                 false,
1961                 hir::Unsafety::Normal,
1962                 abi::Abi::Rust,
1963             ))
1964         }
1965
1966         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1967             // Closure signatures are not like other function
1968             // signatures and cannot be accessed through `fn_sig`. For
1969             // example, a closure signature excludes the `self`
1970             // argument. In any case they are embedded within the
1971             // closure type as part of the `ClosureSubsts`.
1972             //
1973             // To get the signature of a closure, you should use the
1974             // `sig` method on the `ClosureSubsts`:
1975             //
1976             //    substs.as_closure().sig(def_id, tcx)
1977             bug!(
1978                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1979             );
1980         }
1981
1982         x => {
1983             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1984         }
1985     }
1986 }
1987
1988 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1989     let icx = ItemCtxt::new(tcx, def_id);
1990     match tcx.hir().expect_item(def_id.expect_local()).kind {
1991         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1992             let selfty = tcx.type_of(def_id);
1993             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1994         }),
1995         _ => bug!(),
1996     }
1997 }
1998
1999 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2000     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2001     let item = tcx.hir().expect_item(def_id.expect_local());
2002     match &item.kind {
2003         hir::ItemKind::Impl(hir::Impl {
2004             polarity: hir::ImplPolarity::Negative(span),
2005             of_trait,
2006             ..
2007         }) => {
2008             if is_rustc_reservation {
2009                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2010                 tcx.sess.span_err(span, "reservation impls can't be negative");
2011             }
2012             ty::ImplPolarity::Negative
2013         }
2014         hir::ItemKind::Impl(hir::Impl {
2015             polarity: hir::ImplPolarity::Positive,
2016             of_trait: None,
2017             ..
2018         }) => {
2019             if is_rustc_reservation {
2020                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2021             }
2022             ty::ImplPolarity::Positive
2023         }
2024         hir::ItemKind::Impl(hir::Impl {
2025             polarity: hir::ImplPolarity::Positive,
2026             of_trait: Some(_),
2027             ..
2028         }) => {
2029             if is_rustc_reservation {
2030                 ty::ImplPolarity::Reservation
2031             } else {
2032                 ty::ImplPolarity::Positive
2033             }
2034         }
2035         item => bug!("impl_polarity: {:?} not an impl", item),
2036     }
2037 }
2038
2039 /// Returns the early-bound lifetimes declared in this generics
2040 /// listing. For anything other than fns/methods, this is just all
2041 /// the lifetimes that are declared. For fns or methods, we have to
2042 /// screen out those that do not appear in any where-clauses etc using
2043 /// `resolve_lifetime::early_bound_lifetimes`.
2044 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2045     tcx: TyCtxt<'tcx>,
2046     generics: &'a hir::Generics<'a>,
2047 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2048     generics.params.iter().filter(move |param| match param.kind {
2049         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2050         _ => false,
2051     })
2052 }
2053
2054 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2055 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2056 /// inferred constraints concerning which regions outlive other regions.
2057 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2058     debug!("predicates_defined_on({:?})", def_id);
2059     let mut result = tcx.explicit_predicates_of(def_id);
2060     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2061     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2062     if !inferred_outlives.is_empty() {
2063         debug!(
2064             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2065             def_id, inferred_outlives,
2066         );
2067         if result.predicates.is_empty() {
2068             result.predicates = inferred_outlives;
2069         } else {
2070             result.predicates = tcx
2071                 .arena
2072                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2073         }
2074     }
2075
2076     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2077     result
2078 }
2079
2080 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2081 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2082 /// `Self: Trait` predicates for traits.
2083 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2084     let mut result = tcx.predicates_defined_on(def_id);
2085
2086     if tcx.is_trait(def_id) {
2087         // For traits, add `Self: Trait` predicate. This is
2088         // not part of the predicates that a user writes, but it
2089         // is something that one must prove in order to invoke a
2090         // method or project an associated type.
2091         //
2092         // In the chalk setup, this predicate is not part of the
2093         // "predicates" for a trait item. But it is useful in
2094         // rustc because if you directly (e.g.) invoke a trait
2095         // method like `Trait::method(...)`, you must naturally
2096         // prove that the trait applies to the types that were
2097         // used, and adding the predicate into this list ensures
2098         // that this is done.
2099         //
2100         // We use a DUMMY_SP here as a way to signal trait bounds that come
2101         // from the trait itself that *shouldn't* be shown as the source of
2102         // an obligation and instead be skipped. Otherwise we'd use
2103         // `tcx.def_span(def_id);`
2104         let span = rustc_span::DUMMY_SP;
2105         result.predicates =
2106             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2107                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2108                 span,
2109             ))));
2110     }
2111     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2112     result
2113 }
2114
2115 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2116 /// N.B., this does not include any implied/inferred constraints.
2117 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2118     use rustc_hir::*;
2119
2120     debug!("explicit_predicates_of(def_id={:?})", def_id);
2121
2122     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2123     let node = tcx.hir().get(hir_id);
2124
2125     let mut is_trait = None;
2126     let mut is_default_impl_trait = None;
2127
2128     let icx = ItemCtxt::new(tcx, def_id);
2129
2130     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2131
2132     // We use an `IndexSet` to preserves order of insertion.
2133     // Preserving the order of insertion is important here so as not to break UI tests.
2134     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2135
2136     let ast_generics = match node {
2137         Node::TraitItem(item) => &item.generics,
2138
2139         Node::ImplItem(item) => &item.generics,
2140
2141         Node::Item(item) => {
2142             match item.kind {
2143                 ItemKind::Impl(ref impl_) => {
2144                     if impl_.defaultness.is_default() {
2145                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2146                     }
2147                     &impl_.generics
2148                 }
2149                 ItemKind::Fn(.., ref generics, _)
2150                 | ItemKind::TyAlias(_, ref generics)
2151                 | ItemKind::Enum(_, ref generics)
2152                 | ItemKind::Struct(_, ref generics)
2153                 | ItemKind::Union(_, ref generics) => generics,
2154
2155                 ItemKind::Trait(_, _, ref generics, ..) => {
2156                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2157                     generics
2158                 }
2159                 ItemKind::TraitAlias(ref generics, _) => {
2160                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2161                     generics
2162                 }
2163                 ItemKind::OpaqueTy(OpaqueTy {
2164                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2165                     ..
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::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     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2782
2783     let mut inline_span = None;
2784     let mut link_ordinal_span = None;
2785     let mut no_sanitize_span = None;
2786     for attr in attrs.iter() {
2787         if attr.has_name(sym::cold) {
2788             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2789         } else if attr.has_name(sym::rustc_allocator) {
2790             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2791         } else if attr.has_name(sym::ffi_returns_twice) {
2792             if tcx.is_foreign_item(id) {
2793                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2794             } else {
2795                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2796                 struct_span_err!(
2797                     tcx.sess,
2798                     attr.span,
2799                     E0724,
2800                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2801                 )
2802                 .emit();
2803             }
2804         } else if attr.has_name(sym::ffi_pure) {
2805             if tcx.is_foreign_item(id) {
2806                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2807                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2808                     struct_span_err!(
2809                         tcx.sess,
2810                         attr.span,
2811                         E0757,
2812                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2813                     )
2814                     .emit();
2815                 } else {
2816                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2817                 }
2818             } else {
2819                 // `#[ffi_pure]` is only allowed on foreign functions
2820                 struct_span_err!(
2821                     tcx.sess,
2822                     attr.span,
2823                     E0755,
2824                     "`#[ffi_pure]` may only be used on foreign functions"
2825                 )
2826                 .emit();
2827             }
2828         } else if attr.has_name(sym::ffi_const) {
2829             if tcx.is_foreign_item(id) {
2830                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2831             } else {
2832                 // `#[ffi_const]` is only allowed on foreign functions
2833                 struct_span_err!(
2834                     tcx.sess,
2835                     attr.span,
2836                     E0756,
2837                     "`#[ffi_const]` may only be used on foreign functions"
2838                 )
2839                 .emit();
2840             }
2841         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2842             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2843         } else if attr.has_name(sym::naked) {
2844             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2845         } else if attr.has_name(sym::no_mangle) {
2846             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2847         } else if attr.has_name(sym::no_coverage) {
2848             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2849         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2850             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2851         } else if attr.has_name(sym::used) {
2852             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2853         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2854             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2855                 struct_span_err!(
2856                     tcx.sess,
2857                     attr.span,
2858                     E0776,
2859                     "`#[cmse_nonsecure_entry]` requires C ABI"
2860                 )
2861                 .emit();
2862             }
2863             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2864                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2865                     .emit();
2866             }
2867             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2868         } else if attr.has_name(sym::thread_local) {
2869             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2870         } else if attr.has_name(sym::track_caller) {
2871             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2872                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2873                     .emit();
2874             }
2875             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2876                 feature_err(
2877                     &tcx.sess.parse_sess,
2878                     sym::closure_track_caller,
2879                     attr.span,
2880                     "`#[track_caller]` on closures is currently unstable",
2881                 )
2882                 .emit();
2883             }
2884             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2885         } else if attr.has_name(sym::export_name) {
2886             if let Some(s) = attr.value_str() {
2887                 if s.as_str().contains('\0') {
2888                     // `#[export_name = ...]` will be converted to a null-terminated string,
2889                     // so it may not contain any null characters.
2890                     struct_span_err!(
2891                         tcx.sess,
2892                         attr.span,
2893                         E0648,
2894                         "`export_name` may not contain null characters"
2895                     )
2896                     .emit();
2897                 }
2898                 codegen_fn_attrs.export_name = Some(s);
2899             }
2900         } else if attr.has_name(sym::target_feature) {
2901             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2902                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2903                     // The `#[target_feature]` attribute is allowed on
2904                     // WebAssembly targets on all functions, including safe
2905                     // ones. Other targets require that `#[target_feature]` is
2906                     // only applied to unsafe funtions (pending the
2907                     // `target_feature_11` feature) because on most targets
2908                     // execution of instructions that are not supported is
2909                     // considered undefined behavior. For WebAssembly which is a
2910                     // 100% safe target at execution time it's not possible to
2911                     // execute undefined instructions, and even if a future
2912                     // feature was added in some form for this it would be a
2913                     // deterministic trap. There is no undefined behavior when
2914                     // executing WebAssembly so `#[target_feature]` is allowed
2915                     // on safe functions (but again, only for WebAssembly)
2916                     //
2917                     // Note that this is also allowed if `actually_rustdoc` so
2918                     // if a target is documenting some wasm-specific code then
2919                     // it's not spuriously denied.
2920                 } else if !tcx.features().target_feature_11 {
2921                     let mut err = feature_err(
2922                         &tcx.sess.parse_sess,
2923                         sym::target_feature_11,
2924                         attr.span,
2925                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2926                     );
2927                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2928                     err.emit();
2929                 } else if let Some(local_id) = id.as_local() {
2930                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2931                 }
2932             }
2933             from_target_feature(
2934                 tcx,
2935                 id,
2936                 attr,
2937                 supported_target_features,
2938                 &mut codegen_fn_attrs.target_features,
2939             );
2940         } else if attr.has_name(sym::linkage) {
2941             if let Some(val) = attr.value_str() {
2942                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2943             }
2944         } else if attr.has_name(sym::link_section) {
2945             if let Some(val) = attr.value_str() {
2946                 if val.as_str().bytes().any(|b| b == 0) {
2947                     let msg = format!(
2948                         "illegal null byte in link_section \
2949                          value: `{}`",
2950                         &val
2951                     );
2952                     tcx.sess.span_err(attr.span, &msg);
2953                 } else {
2954                     codegen_fn_attrs.link_section = Some(val);
2955                 }
2956             }
2957         } else if attr.has_name(sym::link_name) {
2958             codegen_fn_attrs.link_name = attr.value_str();
2959         } else if attr.has_name(sym::link_ordinal) {
2960             link_ordinal_span = Some(attr.span);
2961             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2962                 codegen_fn_attrs.link_ordinal = ordinal;
2963             }
2964         } else if attr.has_name(sym::no_sanitize) {
2965             no_sanitize_span = Some(attr.span);
2966             if let Some(list) = attr.meta_item_list() {
2967                 for item in list.iter() {
2968                     if item.has_name(sym::address) {
2969                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2970                     } else if item.has_name(sym::cfi) {
2971                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2972                     } else if item.has_name(sym::memory) {
2973                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2974                     } else if item.has_name(sym::thread) {
2975                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2976                     } else if item.has_name(sym::hwaddress) {
2977                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2978                     } else {
2979                         tcx.sess
2980                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2981                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2982                             .emit();
2983                     }
2984                 }
2985             }
2986         } else if attr.has_name(sym::instruction_set) {
2987             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2988                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2989                     [NestedMetaItem::MetaItem(set)] => {
2990                         let segments =
2991                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2992                         match segments.as_slice() {
2993                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2994                                 if !tcx.sess.target.has_thumb_interworking {
2995                                     struct_span_err!(
2996                                         tcx.sess.diagnostic(),
2997                                         attr.span,
2998                                         E0779,
2999                                         "target does not support `#[instruction_set]`"
3000                                     )
3001                                     .emit();
3002                                     None
3003                                 } else if segments[1] == sym::a32 {
3004                                     Some(InstructionSetAttr::ArmA32)
3005                                 } else if segments[1] == sym::t32 {
3006                                     Some(InstructionSetAttr::ArmT32)
3007                                 } else {
3008                                     unreachable!()
3009                                 }
3010                             }
3011                             _ => {
3012                                 struct_span_err!(
3013                                     tcx.sess.diagnostic(),
3014                                     attr.span,
3015                                     E0779,
3016                                     "invalid instruction set specified",
3017                                 )
3018                                 .emit();
3019                                 None
3020                             }
3021                         }
3022                     }
3023                     [] => {
3024                         struct_span_err!(
3025                             tcx.sess.diagnostic(),
3026                             attr.span,
3027                             E0778,
3028                             "`#[instruction_set]` requires an argument"
3029                         )
3030                         .emit();
3031                         None
3032                     }
3033                     _ => {
3034                         struct_span_err!(
3035                             tcx.sess.diagnostic(),
3036                             attr.span,
3037                             E0779,
3038                             "cannot specify more than one instruction set"
3039                         )
3040                         .emit();
3041                         None
3042                     }
3043                 },
3044                 _ => {
3045                     struct_span_err!(
3046                         tcx.sess.diagnostic(),
3047                         attr.span,
3048                         E0778,
3049                         "must specify an instruction set"
3050                     )
3051                     .emit();
3052                     None
3053                 }
3054             };
3055         } else if attr.has_name(sym::repr) {
3056             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3057                 Some(items) => match items.as_slice() {
3058                     [item] => match item.name_value_literal() {
3059                         Some((sym::align, literal)) => {
3060                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3061
3062                             match alignment {
3063                                 Ok(align) => Some(align),
3064                                 Err(msg) => {
3065                                     struct_span_err!(
3066                                         tcx.sess.diagnostic(),
3067                                         attr.span,
3068                                         E0589,
3069                                         "invalid `repr(align)` attribute: {}",
3070                                         msg
3071                                     )
3072                                     .emit();
3073
3074                                     None
3075                                 }
3076                             }
3077                         }
3078                         _ => None,
3079                     },
3080                     [] => None,
3081                     _ => None,
3082                 },
3083                 None => None,
3084             };
3085         }
3086     }
3087
3088     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3089         if !attr.has_name(sym::inline) {
3090             return ia;
3091         }
3092         match attr.meta_kind() {
3093             Some(MetaItemKind::Word) => InlineAttr::Hint,
3094             Some(MetaItemKind::List(ref items)) => {
3095                 inline_span = Some(attr.span);
3096                 if items.len() != 1 {
3097                     struct_span_err!(
3098                         tcx.sess.diagnostic(),
3099                         attr.span,
3100                         E0534,
3101                         "expected one argument"
3102                     )
3103                     .emit();
3104                     InlineAttr::None
3105                 } else if list_contains_name(&items, sym::always) {
3106                     InlineAttr::Always
3107                 } else if list_contains_name(&items, sym::never) {
3108                     InlineAttr::Never
3109                 } else {
3110                     struct_span_err!(
3111                         tcx.sess.diagnostic(),
3112                         items[0].span(),
3113                         E0535,
3114                         "invalid argument"
3115                     )
3116                     .emit();
3117
3118                     InlineAttr::None
3119                 }
3120             }
3121             Some(MetaItemKind::NameValue(_)) => ia,
3122             None => ia,
3123         }
3124     });
3125
3126     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3127         if !attr.has_name(sym::optimize) {
3128             return ia;
3129         }
3130         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3131         match attr.meta_kind() {
3132             Some(MetaItemKind::Word) => {
3133                 err(attr.span, "expected one argument");
3134                 ia
3135             }
3136             Some(MetaItemKind::List(ref items)) => {
3137                 inline_span = Some(attr.span);
3138                 if items.len() != 1 {
3139                     err(attr.span, "expected one argument");
3140                     OptimizeAttr::None
3141                 } else if list_contains_name(&items, sym::size) {
3142                     OptimizeAttr::Size
3143                 } else if list_contains_name(&items, sym::speed) {
3144                     OptimizeAttr::Speed
3145                 } else {
3146                     err(items[0].span(), "invalid argument");
3147                     OptimizeAttr::None
3148                 }
3149             }
3150             Some(MetaItemKind::NameValue(_)) => ia,
3151             None => ia,
3152         }
3153     });
3154
3155     // #73631: closures inherit `#[target_feature]` annotations
3156     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3157         let owner_id = tcx.parent(id).expect("closure should have a parent");
3158         codegen_fn_attrs
3159             .target_features
3160             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3161     }
3162
3163     // If a function uses #[target_feature] it can't be inlined into general
3164     // purpose functions as they wouldn't have the right target features
3165     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3166     // respected.
3167     if !codegen_fn_attrs.target_features.is_empty() {
3168         if codegen_fn_attrs.inline == InlineAttr::Always {
3169             if let Some(span) = inline_span {
3170                 tcx.sess.span_err(
3171                     span,
3172                     "cannot use `#[inline(always)]` with \
3173                      `#[target_feature]`",
3174                 );
3175             }
3176         }
3177     }
3178
3179     if !codegen_fn_attrs.no_sanitize.is_empty() {
3180         if codegen_fn_attrs.inline == InlineAttr::Always {
3181             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3182                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3183                 tcx.struct_span_lint_hir(
3184                     lint::builtin::INLINE_NO_SANITIZE,
3185                     hir_id,
3186                     no_sanitize_span,
3187                     |lint| {
3188                         lint.build("`no_sanitize` will have no effect after inlining")
3189                             .span_note(inline_span, "inlining requested here")
3190                             .emit();
3191                     },
3192                 )
3193             }
3194         }
3195     }
3196
3197     // Weak lang items have the same semantics as "std internal" symbols in the
3198     // sense that they're preserved through all our LTO passes and only
3199     // strippable by the linker.
3200     //
3201     // Additionally weak lang items have predetermined symbol names.
3202     if tcx.is_weak_lang_item(id) {
3203         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3204     }
3205     if let Some(name) = weak_lang_items::link_name(attrs) {
3206         codegen_fn_attrs.export_name = Some(name);
3207         codegen_fn_attrs.link_name = Some(name);
3208     }
3209     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3210
3211     // Internal symbols to the standard library all have no_mangle semantics in
3212     // that they have defined symbol names present in the function name. This
3213     // also applies to weak symbols where they all have known symbol names.
3214     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3215         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3216     }
3217
3218     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3219     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3220     // intrinsic functions.
3221     if let Some(name) = &codegen_fn_attrs.link_name {
3222         if name.as_str().starts_with("llvm.") {
3223             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3224         }
3225     }
3226
3227     codegen_fn_attrs
3228 }
3229
3230 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3231 /// applied to the method prototype.
3232 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3233     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3234         if let ty::AssocItemContainer::ImplContainer(_) = impl_item.container {
3235             if let Some(trait_item) = impl_item.trait_item_def_id {
3236                 return tcx
3237                     .codegen_fn_attrs(trait_item)
3238                     .flags
3239                     .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3240             }
3241         }
3242     }
3243
3244     false
3245 }
3246
3247 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3248     use rustc_ast::{Lit, LitIntType, LitKind};
3249     let meta_item_list = attr.meta_item_list();
3250     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3251     let sole_meta_list = match meta_item_list {
3252         Some([item]) => item.literal(),
3253         Some(_) => {
3254             tcx.sess
3255                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3256                 .note("the attribute requires exactly one argument")
3257                 .emit();
3258             return None;
3259         }
3260         _ => None,
3261     };
3262     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3263         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3264         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3265         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3266         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3267         //
3268         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3269         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3270         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3271         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3272         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3273         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3274         // about LINK.EXE failing.)
3275         if *ordinal <= u16::MAX as u128 {
3276             Some(*ordinal as u16)
3277         } else {
3278             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3279             tcx.sess
3280                 .struct_span_err(attr.span, &msg)
3281                 .note("the value may not exceed `u16::MAX`")
3282                 .emit();
3283             None
3284         }
3285     } else {
3286         tcx.sess
3287             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3288             .note("an unsuffixed integer value, e.g., `1`, is expected")
3289             .emit();
3290         None
3291     }
3292 }
3293
3294 fn check_link_name_xor_ordinal(
3295     tcx: TyCtxt<'_>,
3296     codegen_fn_attrs: &CodegenFnAttrs,
3297     inline_span: Option<Span>,
3298 ) {
3299     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3300         return;
3301     }
3302     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3303     if let Some(span) = inline_span {
3304         tcx.sess.span_err(span, msg);
3305     } else {
3306         tcx.sess.err(msg);
3307     }
3308 }
3309
3310 /// Checks the function annotated with `#[target_feature]` is not a safe
3311 /// trait method implementation, reporting an error if it is.
3312 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3313     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3314     let node = tcx.hir().get(hir_id);
3315     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3316         let parent_id = tcx.hir().get_parent_item(hir_id);
3317         let parent_item = tcx.hir().expect_item(parent_id);
3318         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3319             tcx.sess
3320                 .struct_span_err(
3321                     attr_span,
3322                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3323                 )
3324                 .span_label(attr_span, "cannot be applied to safe trait method")
3325                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3326                 .emit();
3327         }
3328     }
3329 }