compiler/rustc_typeck/src/collect.rs

   1 // ignore-tidy-filelength
   2 //! "Collection" is the process of determining the type and other external
   3 //! details of each item in Rust. Collection is specifically concerned
   4 //! with *inter-procedural* things -- for example, for a function
   5 //! definition, collection will figure out the type and signature of the
   6 //! function, but it will not visit the *body* of the function in any way,
   7 //! nor examine type annotations on local variables (that's the job of
   8 //! type *checking*).
   9 //!
  10 //! Collecting is ultimately defined by a bundle of queries that
  11 //! inquire after various facts about the items in the crate (e.g.,
  12 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  13 //! for the full set.
  14 //!
  15 //! At present, however, we do run collection across all items in the
  16 //! crate as a kind of pass. This should eventually be factored away.
  17
  18 use crate::astconv::AstConv;
  19 use crate::bounds::Bounds;
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::errors;
  23 use crate::middle::resolve_lifetime as rl;
  24 use rustc_ast as ast;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::nested_filter;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         type_of: type_of::type_of,
  72         item_bounds: item_bounds::item_bounds,
  73         explicit_item_bounds: item_bounds::explicit_item_bounds,
  74         generics_of,
  75         predicates_of,
  76         predicates_defined_on,
  77         explicit_predicates_of,
  78         super_predicates_of,
  79         super_predicates_that_define_assoc_type,
  80         trait_explicit_predicates_and_bounds,
  81         type_param_predicates,
  82         trait_def,
  83         adt_def,
  84         fn_sig,
  85         impl_trait_ref,
  86         impl_polarity,
  87         is_foreign_item,
  88         generator_kind,
  89         codegen_fn_attrs,
  90         asm_target_features,
  91         collect_mod_item_types,
  92         should_inherit_track_caller,
  93         ..*providers
  94     };
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98
  99 /// Context specific to some particular item. This is what implements
 100 /// `AstConv`. It has information about the predicates that are defined
 101 /// on the trait. Unfortunately, this predicate information is
 102 /// available in various different forms at various points in the
 103 /// process. So we can't just store a pointer to e.g., the AST or the
 104 /// parsed ty form, we have to be more flexible. To this end, the
 105 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 106 /// `get_type_parameter_bounds` requests, drawing the information from
 107 /// the AST (`hir::Generics`), recursively.
 108 pub struct ItemCtxt<'tcx> {
 109     tcx: TyCtxt<'tcx>,
 110     item_def_id: DefId,
 111 }
 112
 113 ///////////////////////////////////////////////////////////////////////////
 114
 115 #[derive(Default)]
 116 crate struct HirPlaceholderCollector(crate Vec<Span>);
 117
 118 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 119     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 120         if let hir::TyKind::Infer = t.kind {
 121             self.0.push(t.span);
 122         }
 123         intravisit::walk_ty(self, t)
 124     }
 125     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 126         match generic_arg {
 127             hir::GenericArg::Infer(inf) => {
 128                 self.0.push(inf.span);
 129                 intravisit::walk_inf(self, inf);
 130             }
 131             hir::GenericArg::Type(t) => self.visit_ty(t),
 132             _ => {}
 133         }
 134     }
 135     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 136         if let &hir::ArrayLen::Infer(_, span) = length {
 137             self.0.push(span);
 138         }
 139         intravisit::walk_array_len(self, length)
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder(tcx, placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty && 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         // if function is wrapped around a const or static,
 212         // then don't show the suggestion
 213         if !(is_fn && is_const_or_static) {
 214             err.multipart_suggestion(
 215                 "use type parameters instead",
 216                 sugg,
 217                 Applicability::HasPlaceholders,
 218             );
 219         }
 220     }
 221     err.emit();
 222 }
 223
 224 fn reject_placeholder_type_signatures_in_item<'tcx>(
 225     tcx: TyCtxt<'tcx>,
 226     item: &'tcx hir::Item<'tcx>,
 227 ) {
 228     let (generics, suggest) = match &item.kind {
 229         hir::ItemKind::Union(_, generics)
 230         | hir::ItemKind::Enum(_, generics)
 231         | hir::ItemKind::TraitAlias(generics, _)
 232         | hir::ItemKind::Trait(_, _, generics, ..)
 233         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 234         | hir::ItemKind::Struct(_, generics) => (generics, true),
 235         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 236         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 237         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 238         _ => return,
 239     };
 240
 241     let mut visitor = HirPlaceholderCollector::default();
 242     visitor.visit_item(item);
 243
 244     placeholder_type_error(
 245         tcx,
 246         Some(generics.span),
 247         generics.params,
 248         visitor.0,
 249         suggest,
 250         None,
 251         item.kind.descr(),
 252     );
 253 }
 254
 255 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 256     type NestedFilter = nested_filter::OnlyBodies;
 257
 258     fn nested_visit_map(&mut self) -> Self::Map {
 259         self.tcx.hir()
 260     }
 261
 262     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 263         convert_item(self.tcx, item.item_id());
 264         reject_placeholder_type_signatures_in_item(self.tcx, item);
 265         intravisit::walk_item(self, item);
 266     }
 267
 268     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 269         for param in generics.params {
 270             match param.kind {
 271                 hir::GenericParamKind::Lifetime { .. } => {}
 272                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 273                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 274                     self.tcx.ensure().type_of(def_id);
 275                 }
 276                 hir::GenericParamKind::Type { .. } => {}
 277                 hir::GenericParamKind::Const { default, .. } => {
 278                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 279                     self.tcx.ensure().type_of(def_id);
 280                     if let Some(default) = default {
 281                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 282                         // need to store default and type of default
 283                         self.tcx.ensure().type_of(default_def_id);
 284                         self.tcx.ensure().const_param_default(def_id);
 285                     }
 286                 }
 287             }
 288         }
 289         intravisit::walk_generics(self, generics);
 290     }
 291
 292     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 293         if let hir::ExprKind::Closure(..) = expr.kind {
 294             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 295             self.tcx.ensure().generics_of(def_id);
 296             // We do not call `type_of` for closures here as that
 297             // depends on typecheck and would therefore hide
 298             // any further errors in case one typeck fails.
 299         }
 300         intravisit::walk_expr(self, expr);
 301     }
 302
 303     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 304         convert_trait_item(self.tcx, trait_item.trait_item_id());
 305         intravisit::walk_trait_item(self, trait_item);
 306     }
 307
 308     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 309         convert_impl_item(self.tcx, impl_item.impl_item_id());
 310         intravisit::walk_impl_item(self, impl_item);
 311     }
 312 }
 313
 314 ///////////////////////////////////////////////////////////////////////////
 315 // Utility types and common code for the above passes.
 316
 317 fn bad_placeholder<'tcx>(
 318     tcx: TyCtxt<'tcx>,
 319     mut spans: Vec<Span>,
 320     kind: &'static str,
 321 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 322     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 323
 324     spans.sort();
 325     let mut err = struct_span_err!(
 326         tcx.sess,
 327         spans.clone(),
 328         E0121,
 329         "the placeholder `_` is not allowed within types on item signatures for {}",
 330         kind
 331     );
 332     for span in spans {
 333         err.span_label(span, "not allowed in type signatures");
 334     }
 335     err
 336 }
 337
 338 impl<'tcx> ItemCtxt<'tcx> {
 339     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 340         ItemCtxt { tcx, item_def_id }
 341     }
 342
 343     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 344         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 345     }
 346
 347     pub fn hir_id(&self) -> hir::HirId {
 348         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 349     }
 350
 351     pub fn node(&self) -> hir::Node<'tcx> {
 352         self.tcx.hir().get(self.hir_id())
 353     }
 354 }
 355
 356 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 357     fn tcx(&self) -> TyCtxt<'tcx> {
 358         self.tcx
 359     }
 360
 361     fn item_def_id(&self) -> Option<DefId> {
 362         Some(self.item_def_id)
 363     }
 364
 365     fn get_type_parameter_bounds(
 366         &self,
 367         span: Span,
 368         def_id: DefId,
 369         assoc_name: Ident,
 370     ) -> ty::GenericPredicates<'tcx> {
 371         self.tcx.at(span).type_param_predicates((
 372             self.item_def_id,
 373             def_id.expect_local(),
 374             assoc_name,
 375         ))
 376     }
 377
 378     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 379         None
 380     }
 381
 382     fn allow_ty_infer(&self) -> bool {
 383         false
 384     }
 385
 386     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 387         self.tcx().ty_error_with_message(span, "bad placeholder type")
 388     }
 389
 390     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 391         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
 392             ty::ReErased => self.tcx.lifetimes.re_static,
 393             _ => r,
 394         });
 395         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 396     }
 397
 398     fn projected_ty_from_poly_trait_ref(
 399         &self,
 400         span: Span,
 401         item_def_id: DefId,
 402         item_segment: &hir::PathSegment<'_>,
 403         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 404     ) -> Ty<'tcx> {
 405         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 406             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 407                 self,
 408                 self.tcx,
 409                 span,
 410                 item_def_id,
 411                 item_segment,
 412                 trait_ref.substs,
 413             );
 414             self.tcx().mk_projection(item_def_id, item_substs)
 415         } else {
 416             // There are no late-bound regions; we can just ignore the binder.
 417             let mut err = struct_span_err!(
 418                 self.tcx().sess,
 419                 span,
 420                 E0212,
 421                 "cannot use the associated type of a trait \
 422                  with uninferred generic parameters"
 423             );
 424
 425             match self.node() {
 426                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 427                     let item =
 428                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 429                     match &item.kind {
 430                         hir::ItemKind::Enum(_, generics)
 431                         | hir::ItemKind::Struct(_, generics)
 432                         | hir::ItemKind::Union(_, generics) => {
 433                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 434                             let (lt_sp, sugg) = match generics.params {
 435                                 [] => (generics.span, format!("<{}>", lt_name)),
 436                                 [bound, ..] => {
 437                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 438                                 }
 439                             };
 440                             let suggestions = vec![
 441                                 (lt_sp, sugg),
 442                                 (
 443                                     span.with_hi(item_segment.ident.span.lo()),
 444                                     format!(
 445                                         "{}::",
 446                                         // Replace the existing lifetimes with a new named lifetime.
 447                                         self.tcx
 448                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 449                                                 self.tcx.mk_region(ty::ReEarlyBound(
 450                                                     ty::EarlyBoundRegion {
 451                                                         def_id: item_def_id,
 452                                                         index: 0,
 453                                                         name: Symbol::intern(&lt_name),
 454                                                     },
 455                                                 ))
 456                                             })
 457                                             .0,
 458                                     ),
 459                                 ),
 460                             ];
 461                             err.multipart_suggestion(
 462                                 "use a fully qualified path with explicit lifetimes",
 463                                 suggestions,
 464                                 Applicability::MaybeIncorrect,
 465                             );
 466                         }
 467                         _ => {}
 468                     }
 469                 }
 470                 hir::Node::Item(hir::Item {
 471                     kind:
 472                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 473                     ..
 474                 }) => {}
 475                 hir::Node::Item(_)
 476                 | hir::Node::ForeignItem(_)
 477                 | hir::Node::TraitItem(_)
 478                 | hir::Node::ImplItem(_) => {
 479                     err.span_suggestion_verbose(
 480                         span.with_hi(item_segment.ident.span.lo()),
 481                         "use a fully qualified path with inferred lifetimes",
 482                         format!(
 483                             "{}::",
 484                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 485                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 486                         ),
 487                         Applicability::MaybeIncorrect,
 488                     );
 489                 }
 490                 _ => {}
 491             }
 492             err.emit();
 493             self.tcx().ty_error()
 494         }
 495     }
 496
 497     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 498         // Types in item signatures are not normalized to avoid undue dependencies.
 499         ty
 500     }
 501
 502     fn set_tainted_by_errors(&self) {
 503         // There's no obvious place to track this, so just let it go.
 504     }
 505
 506     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 507         // There's no place to record types from signatures?
 508     }
 509 }
 510
 511 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 512 fn get_new_lifetime_name<'tcx>(
 513     tcx: TyCtxt<'tcx>,
 514     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 515     generics: &hir::Generics<'tcx>,
 516 ) -> String {
 517     let existing_lifetimes = tcx
 518         .collect_referenced_late_bound_regions(&poly_trait_ref)
 519         .into_iter()
 520         .filter_map(|lt| {
 521             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 522                 Some(name.as_str().to_string())
 523             } else {
 524                 None
 525             }
 526         })
 527         .chain(generics.params.iter().filter_map(|param| {
 528             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 529                 Some(param.name.ident().as_str().to_string())
 530             } else {
 531                 None
 532             }
 533         }))
 534         .collect::<FxHashSet<String>>();
 535
 536     let a_to_z_repeat_n = |n| {
 537         (b'a'..=b'z').map(move |c| {
 538             let mut s = '\''.to_string();
 539             s.extend(std::iter::repeat(char::from(c)).take(n));
 540             s
 541         })
 542     };
 543
 544     // If all single char lifetime names are present, we wrap around and double the chars.
 545     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 546 }
 547
 548 /// Returns the predicates defined on `item_def_id` of the form
 549 /// `X: Foo` where `X` is the type parameter `def_id`.
 550 fn type_param_predicates(
 551     tcx: TyCtxt<'_>,
 552     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 553 ) -> ty::GenericPredicates<'_> {
 554     use rustc_hir::*;
 555
 556     // In the AST, bounds can derive from two places. Either
 557     // written inline like `<T: Foo>` or in a where-clause like
 558     // `where T: Foo`.
 559
 560     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 561     let param_owner = tcx.hir().ty_param_owner(def_id);
 562     let generics = tcx.generics_of(param_owner);
 563     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 564     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 565
 566     // Don't look for bounds where the type parameter isn't in scope.
 567     let parent = if item_def_id == param_owner.to_def_id() {
 568         None
 569     } else {
 570         tcx.generics_of(item_def_id).parent
 571     };
 572
 573     let mut result = parent
 574         .map(|parent| {
 575             let icx = ItemCtxt::new(tcx, parent);
 576             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 577         })
 578         .unwrap_or_default();
 579     let mut extend = None;
 580
 581     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 582     let ast_generics = match tcx.hir().get(item_hir_id) {
 583         Node::TraitItem(item) => &item.generics,
 584
 585         Node::ImplItem(item) => &item.generics,
 586
 587         Node::Item(item) => {
 588             match item.kind {
 589                 ItemKind::Fn(.., ref generics, _)
 590                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 591                 | ItemKind::TyAlias(_, ref generics)
 592                 | ItemKind::OpaqueTy(OpaqueTy {
 593                     ref generics,
 594                     origin: hir::OpaqueTyOrigin::TyAlias,
 595                     ..
 596                 })
 597                 | ItemKind::Enum(_, ref generics)
 598                 | ItemKind::Struct(_, ref generics)
 599                 | ItemKind::Union(_, ref generics) => generics,
 600                 ItemKind::Trait(_, _, ref generics, ..) => {
 601                     // Implied `Self: Trait` and supertrait bounds.
 602                     if param_id == item_hir_id {
 603                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 604                         extend =
 605                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 606                     }
 607                     generics
 608                 }
 609                 _ => return result,
 610             }
 611         }
 612
 613         Node::ForeignItem(item) => match item.kind {
 614             ForeignItemKind::Fn(_, _, ref generics) => generics,
 615             _ => return result,
 616         },
 617
 618         _ => return result,
 619     };
 620
 621     let icx = ItemCtxt::new(tcx, item_def_id);
 622     let extra_predicates = extend.into_iter().chain(
 623         icx.type_parameter_bounds_in_generics(
 624             ast_generics,
 625             param_id,
 626             ty,
 627             OnlySelfBounds(true),
 628             Some(assoc_name),
 629         )
 630         .into_iter()
 631         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 632             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 633             _ => false,
 634         }),
 635     );
 636     result.predicates =
 637         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 638     result
 639 }
 640
 641 impl<'tcx> ItemCtxt<'tcx> {
 642     /// Finds bounds from `hir::Generics`. This requires scanning through the
 643     /// AST. We do this to avoid having to convert *all* the bounds, which
 644     /// would create artificial cycles. Instead, we can only convert the
 645     /// bounds for a type parameter `X` if `X::Foo` is used.
 646     fn type_parameter_bounds_in_generics(
 647         &self,
 648         ast_generics: &'tcx hir::Generics<'tcx>,
 649         param_id: hir::HirId,
 650         ty: Ty<'tcx>,
 651         only_self_bounds: OnlySelfBounds,
 652         assoc_name: Option<Ident>,
 653     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 654         let from_ty_params = ast_generics
 655             .params
 656             .iter()
 657             .filter_map(|param| match param.kind {
 658                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 659                     if param.hir_id == param_id =>
 660                 {
 661                     Some(&param.bounds)
 662                 }
 663                 _ => None,
 664             })
 665             .flat_map(|bounds| bounds.iter())
 666             .filter(|b| match assoc_name {
 667                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 668                 None => true,
 669             })
 670             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 671
 672         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 673         let from_where_clauses = ast_generics
 674             .where_clause
 675             .predicates
 676             .iter()
 677             .filter_map(|wp| match *wp {
 678                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 679                 _ => None,
 680             })
 681             .flat_map(|bp| {
 682                 let bt = if bp.is_param_bound(param_def_id) {
 683                     Some(ty)
 684                 } else if !only_self_bounds.0 {
 685                     Some(self.to_ty(bp.bounded_ty))
 686                 } else {
 687                     None
 688                 };
 689                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 690
 691                 bp.bounds
 692                     .iter()
 693                     .filter(|b| match assoc_name {
 694                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 695                         None => true,
 696                     })
 697                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 698             })
 699             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 700
 701         from_ty_params.chain(from_where_clauses).collect()
 702     }
 703
 704     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 705         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 706
 707         match b {
 708             hir::GenericBound::Trait(poly_trait_ref, _) => {
 709                 let trait_ref = &poly_trait_ref.trait_ref;
 710                 if let Some(trait_did) = trait_ref.trait_def_id() {
 711                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 712                 } else {
 713                     false
 714                 }
 715             }
 716             _ => false,
 717         }
 718     }
 719 }
 720
 721 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 722     let it = tcx.hir().item(item_id);
 723     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 724     let def_id = item_id.def_id;
 725
 726     match it.kind {
 727         // These don't define types.
 728         hir::ItemKind::ExternCrate(_)
 729         | hir::ItemKind::Use(..)
 730         | hir::ItemKind::Macro(..)
 731         | hir::ItemKind::Mod(_)
 732         | hir::ItemKind::GlobalAsm(_) => {}
 733         hir::ItemKind::ForeignMod { items, .. } => {
 734             for item in items {
 735                 let item = tcx.hir().foreign_item(item.id);
 736                 tcx.ensure().generics_of(item.def_id);
 737                 tcx.ensure().type_of(item.def_id);
 738                 tcx.ensure().predicates_of(item.def_id);
 739                 match item.kind {
 740                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 741                     hir::ForeignItemKind::Static(..) => {
 742                         let mut visitor = HirPlaceholderCollector::default();
 743                         visitor.visit_foreign_item(item);
 744                         placeholder_type_error(
 745                             tcx,
 746                             None,
 747                             &[],
 748                             visitor.0,
 749                             false,
 750                             None,
 751                             "static variable",
 752                         );
 753                     }
 754                     _ => (),
 755                 }
 756             }
 757         }
 758         hir::ItemKind::Enum(ref enum_definition, _) => {
 759             tcx.ensure().generics_of(def_id);
 760             tcx.ensure().type_of(def_id);
 761             tcx.ensure().predicates_of(def_id);
 762             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 763         }
 764         hir::ItemKind::Impl { .. } => {
 765             tcx.ensure().generics_of(def_id);
 766             tcx.ensure().type_of(def_id);
 767             tcx.ensure().impl_trait_ref(def_id);
 768             tcx.ensure().predicates_of(def_id);
 769         }
 770         hir::ItemKind::Trait(..) => {
 771             tcx.ensure().generics_of(def_id);
 772             tcx.ensure().trait_def(def_id);
 773             tcx.at(it.span).super_predicates_of(def_id);
 774             tcx.ensure().predicates_of(def_id);
 775         }
 776         hir::ItemKind::TraitAlias(..) => {
 777             tcx.ensure().generics_of(def_id);
 778             tcx.at(it.span).super_predicates_of(def_id);
 779             tcx.ensure().predicates_of(def_id);
 780         }
 781         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 782             tcx.ensure().generics_of(def_id);
 783             tcx.ensure().type_of(def_id);
 784             tcx.ensure().predicates_of(def_id);
 785
 786             for f in struct_def.fields() {
 787                 let def_id = tcx.hir().local_def_id(f.hir_id);
 788                 tcx.ensure().generics_of(def_id);
 789                 tcx.ensure().type_of(def_id);
 790                 tcx.ensure().predicates_of(def_id);
 791             }
 792
 793             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 794                 convert_variant_ctor(tcx, ctor_hir_id);
 795             }
 796         }
 797
 798         // Desugared from `impl Trait`, so visited by the function's return type.
 799         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 800             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 801             ..
 802         }) => {}
 803
 804         // Don't call `type_of` on opaque types, since that depends on type
 805         // checking function bodies. `check_item_type` ensures that it's called
 806         // instead.
 807         hir::ItemKind::OpaqueTy(..) => {
 808             tcx.ensure().generics_of(def_id);
 809             tcx.ensure().predicates_of(def_id);
 810             tcx.ensure().explicit_item_bounds(def_id);
 811         }
 812         hir::ItemKind::TyAlias(..)
 813         | hir::ItemKind::Static(..)
 814         | hir::ItemKind::Const(..)
 815         | hir::ItemKind::Fn(..) => {
 816             tcx.ensure().generics_of(def_id);
 817             tcx.ensure().type_of(def_id);
 818             tcx.ensure().predicates_of(def_id);
 819             match it.kind {
 820                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 821                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 822                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 823                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 824                     if let hir::TyKind::TraitObject(..) = ty.kind {
 825                         let mut visitor = HirPlaceholderCollector::default();
 826                         visitor.visit_item(it);
 827                         placeholder_type_error(
 828                             tcx,
 829                             None,
 830                             &[],
 831                             visitor.0,
 832                             false,
 833                             None,
 834                             it.kind.descr(),
 835                         );
 836                     }
 837                 }
 838                 _ => (),
 839             }
 840         }
 841     }
 842 }
 843
 844 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 845     let trait_item = tcx.hir().trait_item(trait_item_id);
 846     tcx.ensure().generics_of(trait_item_id.def_id);
 847
 848     match trait_item.kind {
 849         hir::TraitItemKind::Fn(..) => {
 850             tcx.ensure().type_of(trait_item_id.def_id);
 851             tcx.ensure().fn_sig(trait_item_id.def_id);
 852         }
 853
 854         hir::TraitItemKind::Const(.., Some(_)) => {
 855             tcx.ensure().type_of(trait_item_id.def_id);
 856         }
 857
 858         hir::TraitItemKind::Const(..) => {
 859             tcx.ensure().type_of(trait_item_id.def_id);
 860             // Account for `const C: _;`.
 861             let mut visitor = HirPlaceholderCollector::default();
 862             visitor.visit_trait_item(trait_item);
 863             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 864         }
 865
 866         hir::TraitItemKind::Type(_, Some(_)) => {
 867             tcx.ensure().item_bounds(trait_item_id.def_id);
 868             tcx.ensure().type_of(trait_item_id.def_id);
 869             // Account for `type T = _;`.
 870             let mut visitor = HirPlaceholderCollector::default();
 871             visitor.visit_trait_item(trait_item);
 872             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 873         }
 874
 875         hir::TraitItemKind::Type(_, None) => {
 876             tcx.ensure().item_bounds(trait_item_id.def_id);
 877             // #74612: Visit and try to find bad placeholders
 878             // even if there is no concrete type.
 879             let mut visitor = HirPlaceholderCollector::default();
 880             visitor.visit_trait_item(trait_item);
 881
 882             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 883         }
 884     };
 885
 886     tcx.ensure().predicates_of(trait_item_id.def_id);
 887 }
 888
 889 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 890     let def_id = impl_item_id.def_id;
 891     tcx.ensure().generics_of(def_id);
 892     tcx.ensure().type_of(def_id);
 893     tcx.ensure().predicates_of(def_id);
 894     let impl_item = tcx.hir().impl_item(impl_item_id);
 895     match impl_item.kind {
 896         hir::ImplItemKind::Fn(..) => {
 897             tcx.ensure().fn_sig(def_id);
 898         }
 899         hir::ImplItemKind::TyAlias(_) => {
 900             // Account for `type T = _;`
 901             let mut visitor = HirPlaceholderCollector::default();
 902             visitor.visit_impl_item(impl_item);
 903
 904             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 905         }
 906         hir::ImplItemKind::Const(..) => {}
 907     }
 908 }
 909
 910 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 911     let def_id = tcx.hir().local_def_id(ctor_id);
 912     tcx.ensure().generics_of(def_id);
 913     tcx.ensure().type_of(def_id);
 914     tcx.ensure().predicates_of(def_id);
 915 }
 916
 917 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 918     let def = tcx.adt_def(def_id);
 919     let repr_type = def.repr().discr_type();
 920     let initial = repr_type.initial_discriminant(tcx);
 921     let mut prev_discr = None::<Discr<'_>>;
 922
 923     // fill the discriminant values and field types
 924     for variant in variants {
 925         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 926         prev_discr = Some(
 927             if let Some(ref e) = variant.disr_expr {
 928                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 929                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 930             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 931                 Some(discr)
 932             } else {
 933                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 934                     .span_label(
 935                         variant.span,
 936                         format!("overflowed on value after {}", prev_discr.unwrap()),
 937                     )
 938                     .note(&format!(
 939                         "explicitly set `{} = {}` if that is desired outcome",
 940                         variant.ident, wrapped_discr
 941                     ))
 942                     .emit();
 943                 None
 944             }
 945             .unwrap_or(wrapped_discr),
 946         );
 947
 948         for f in variant.data.fields() {
 949             let def_id = tcx.hir().local_def_id(f.hir_id);
 950             tcx.ensure().generics_of(def_id);
 951             tcx.ensure().type_of(def_id);
 952             tcx.ensure().predicates_of(def_id);
 953         }
 954
 955         // Convert the ctor, if any. This also registers the variant as
 956         // an item.
 957         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 958             convert_variant_ctor(tcx, ctor_hir_id);
 959         }
 960     }
 961 }
 962
 963 fn convert_variant(
 964     tcx: TyCtxt<'_>,
 965     variant_did: Option<LocalDefId>,
 966     ctor_did: Option<LocalDefId>,
 967     ident: Ident,
 968     discr: ty::VariantDiscr,
 969     def: &hir::VariantData<'_>,
 970     adt_kind: ty::AdtKind,
 971     parent_did: LocalDefId,
 972 ) -> ty::VariantDef {
 973     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 974     let fields = def
 975         .fields()
 976         .iter()
 977         .map(|f| {
 978             let fid = tcx.hir().local_def_id(f.hir_id);
 979             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 980             if let Some(prev_span) = dup_span {
 981                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 982                     field_name: f.ident,
 983                     span: f.span,
 984                     prev_span,
 985                 });
 986             } else {
 987                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 988             }
 989
 990             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 991         })
 992         .collect();
 993     let recovered = match def {
 994         hir::VariantData::Struct(_, r) => *r,
 995         _ => false,
 996     };
 997     ty::VariantDef::new(
 998         ident.name,
 999         variant_did.map(LocalDefId::to_def_id),
1000         ctor_did.map(LocalDefId::to_def_id),
1001         discr,
1002         fields,
1003         CtorKind::from_hir(def),
1004         adt_kind,
1005         parent_did.to_def_id(),
1006         recovered,
1007         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1008             || variant_did.map_or(false, |variant_did| {
1009                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1010             }),
1011     )
1012 }
1013
1014 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
1015     use rustc_hir::*;
1016
1017     let def_id = def_id.expect_local();
1018     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1019     let Node::Item(item) = tcx.hir().get(hir_id) else {
1020         bug!();
1021     };
1022
1023     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1024     let (kind, variants) = match item.kind {
1025         ItemKind::Enum(ref def, _) => {
1026             let mut distance_from_explicit = 0;
1027             let variants = def
1028                 .variants
1029                 .iter()
1030                 .map(|v| {
1031                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1032                     let ctor_did =
1033                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1034
1035                     let discr = if let Some(ref e) = v.disr_expr {
1036                         distance_from_explicit = 0;
1037                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1038                     } else {
1039                         ty::VariantDiscr::Relative(distance_from_explicit)
1040                     };
1041                     distance_from_explicit += 1;
1042
1043                     convert_variant(
1044                         tcx,
1045                         variant_did,
1046                         ctor_did,
1047                         v.ident,
1048                         discr,
1049                         &v.data,
1050                         AdtKind::Enum,
1051                         def_id,
1052                     )
1053                 })
1054                 .collect();
1055
1056             (AdtKind::Enum, variants)
1057         }
1058         ItemKind::Struct(ref def, _) => {
1059             let variant_did = None::<LocalDefId>;
1060             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1061
1062             let variants = std::iter::once(convert_variant(
1063                 tcx,
1064                 variant_did,
1065                 ctor_did,
1066                 item.ident,
1067                 ty::VariantDiscr::Relative(0),
1068                 def,
1069                 AdtKind::Struct,
1070                 def_id,
1071             ))
1072             .collect();
1073
1074             (AdtKind::Struct, variants)
1075         }
1076         ItemKind::Union(ref def, _) => {
1077             let variant_did = None;
1078             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1079
1080             let variants = std::iter::once(convert_variant(
1081                 tcx,
1082                 variant_did,
1083                 ctor_did,
1084                 item.ident,
1085                 ty::VariantDiscr::Relative(0),
1086                 def,
1087                 AdtKind::Union,
1088                 def_id,
1089             ))
1090             .collect();
1091
1092             (AdtKind::Union, variants)
1093         }
1094         _ => bug!(),
1095     };
1096     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1097 }
1098
1099 /// Ensures that the super-predicates of the trait with a `DefId`
1100 /// of `trait_def_id` are converted and stored. This also ensures that
1101 /// the transitive super-predicates are converted.
1102 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1103     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1104     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1105 }
1106
1107 /// Ensures that the super-predicates of the trait with a `DefId`
1108 /// of `trait_def_id` are converted and stored. This also ensures that
1109 /// the transitive super-predicates are converted.
1110 fn super_predicates_that_define_assoc_type(
1111     tcx: TyCtxt<'_>,
1112     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1113 ) -> ty::GenericPredicates<'_> {
1114     debug!(
1115         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1116         trait_def_id, assoc_name
1117     );
1118     if trait_def_id.is_local() {
1119         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1120         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1121
1122         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1123             bug!("trait_node_id {} is not an item", trait_hir_id);
1124         };
1125
1126         let (generics, bounds) = match item.kind {
1127             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1128             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1129             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1130         };
1131
1132         let icx = ItemCtxt::new(tcx, trait_def_id);
1133
1134         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1135         let self_param_ty = tcx.types.self_param;
1136         let superbounds1 = if let Some(assoc_name) = assoc_name {
1137             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1138                 &icx,
1139                 self_param_ty,
1140                 bounds,
1141                 assoc_name,
1142             )
1143         } else {
1144             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1145         };
1146
1147         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1148
1149         // Convert any explicit superbounds in the where-clause,
1150         // e.g., `trait Foo where Self: Bar`.
1151         // In the case of trait aliases, however, we include all bounds in the where-clause,
1152         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1153         // as one of its "superpredicates".
1154         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1155         let superbounds2 = icx.type_parameter_bounds_in_generics(
1156             generics,
1157             item.hir_id(),
1158             self_param_ty,
1159             OnlySelfBounds(!is_trait_alias),
1160             assoc_name,
1161         );
1162
1163         // Combine the two lists to form the complete set of superbounds:
1164         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1165
1166         // Now require that immediate supertraits are converted,
1167         // which will, in turn, reach indirect supertraits.
1168         if assoc_name.is_none() {
1169             // Now require that immediate supertraits are converted,
1170             // which will, in turn, reach indirect supertraits.
1171             for &(pred, span) in superbounds {
1172                 debug!("superbound: {:?}", pred);
1173                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1174                     tcx.at(span).super_predicates_of(bound.def_id());
1175                 }
1176             }
1177         }
1178
1179         ty::GenericPredicates { parent: None, predicates: superbounds }
1180     } else {
1181         // if `assoc_name` is None, then the query should've been redirected to an
1182         // external provider
1183         assert!(assoc_name.is_some());
1184         tcx.super_predicates_of(trait_def_id)
1185     }
1186 }
1187
1188 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1189     let item = tcx.hir().expect_item(def_id.expect_local());
1190
1191     let (is_auto, unsafety, items) = match item.kind {
1192         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1193             (is_auto == hir::IsAuto::Yes, unsafety, items)
1194         }
1195         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1196         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1197     };
1198
1199     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1200     if paren_sugar && !tcx.features().unboxed_closures {
1201         tcx.sess
1202             .struct_span_err(
1203                 item.span,
1204                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1205                  which traits can use parenthetical notation",
1206             )
1207             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1208             .emit();
1209     }
1210
1211     let is_marker = tcx.has_attr(def_id, sym::marker);
1212     let skip_array_during_method_dispatch =
1213         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1214     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1215         ty::trait_def::TraitSpecializationKind::Marker
1216     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1217         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1218     } else {
1219         ty::trait_def::TraitSpecializationKind::None
1220     };
1221     let must_implement_one_of = tcx
1222         .get_attrs(def_id)
1223         .iter()
1224         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1225         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1226         // and that they are all identifiers
1227         .and_then(|attr| match attr.meta_item_list() {
1228             Some(items) if items.len() < 2 => {
1229                 tcx.sess
1230                     .struct_span_err(
1231                         attr.span,
1232                         "the `#[rustc_must_implement_one_of]` attribute must be \
1233                         used with at least 2 args",
1234                     )
1235                     .emit();
1236
1237                 None
1238             }
1239             Some(items) => items
1240                 .into_iter()
1241                 .map(|item| item.ident().ok_or(item.span()))
1242                 .collect::<Result<Box<[_]>, _>>()
1243                 .map_err(|span| {
1244                     tcx.sess
1245                         .struct_span_err(span, "must be a name of an associated function")
1246                         .emit();
1247                 })
1248                 .ok()
1249                 .zip(Some(attr.span)),
1250             // Error is reported by `rustc_attr!`
1251             None => None,
1252         })
1253         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1254         // functions in the trait with default implementations
1255         .and_then(|(list, attr_span)| {
1256             let errors = list.iter().filter_map(|ident| {
1257                 let item = items.iter().find(|item| item.ident == *ident);
1258
1259                 match item {
1260                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1261                         if !item.defaultness.has_value() {
1262                             tcx.sess
1263                                 .struct_span_err(
1264                                     item.span,
1265                                     "This function doesn't have a default implementation",
1266                                 )
1267                                 .span_note(attr_span, "required by this annotation")
1268                                 .emit();
1269
1270                             return Some(());
1271                         }
1272
1273                         return None;
1274                     }
1275                     Some(item) => {
1276                         tcx.sess
1277                             .struct_span_err(item.span, "Not a function")
1278                             .span_note(attr_span, "required by this annotation")
1279                             .note(
1280                                 "All `#[rustc_must_implement_one_of]` arguments \
1281                             must be associated function names",
1282                             )
1283                             .emit();
1284                     }
1285                     None => {
1286                         tcx.sess
1287                             .struct_span_err(ident.span, "Function not found in this trait")
1288                             .emit();
1289                     }
1290                 }
1291
1292                 Some(())
1293             });
1294
1295             (errors.count() == 0).then_some(list)
1296         })
1297         // Check for duplicates
1298         .and_then(|list| {
1299             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1300             let mut no_dups = true;
1301
1302             for ident in &*list {
1303                 if let Some(dup) = set.insert(ident.name, ident.span) {
1304                     tcx.sess
1305                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1306                         .note(
1307                             "All `#[rustc_must_implement_one_of]` arguments \
1308                             must be unique",
1309                         )
1310                         .emit();
1311
1312                     no_dups = false;
1313                 }
1314             }
1315
1316             no_dups.then_some(list)
1317         });
1318
1319     ty::TraitDef::new(
1320         def_id,
1321         unsafety,
1322         paren_sugar,
1323         is_auto,
1324         is_marker,
1325         skip_array_during_method_dispatch,
1326         spec_kind,
1327         must_implement_one_of,
1328     )
1329 }
1330
1331 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1332     struct LateBoundRegionsDetector<'tcx> {
1333         tcx: TyCtxt<'tcx>,
1334         outer_index: ty::DebruijnIndex,
1335         has_late_bound_regions: Option<Span>,
1336     }
1337
1338     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1339         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1340             if self.has_late_bound_regions.is_some() {
1341                 return;
1342             }
1343             match ty.kind {
1344                 hir::TyKind::BareFn(..) => {
1345                     self.outer_index.shift_in(1);
1346                     intravisit::walk_ty(self, ty);
1347                     self.outer_index.shift_out(1);
1348                 }
1349                 _ => intravisit::walk_ty(self, ty),
1350             }
1351         }
1352
1353         fn visit_poly_trait_ref(
1354             &mut self,
1355             tr: &'tcx hir::PolyTraitRef<'tcx>,
1356             m: hir::TraitBoundModifier,
1357         ) {
1358             if self.has_late_bound_regions.is_some() {
1359                 return;
1360             }
1361             self.outer_index.shift_in(1);
1362             intravisit::walk_poly_trait_ref(self, tr, m);
1363             self.outer_index.shift_out(1);
1364         }
1365
1366         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1367             if self.has_late_bound_regions.is_some() {
1368                 return;
1369             }
1370
1371             match self.tcx.named_region(lt.hir_id) {
1372                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1373                 Some(
1374                     rl::Region::LateBound(debruijn, _, _)
1375                     | rl::Region::LateBoundAnon(debruijn, _, _),
1376                 ) if debruijn < self.outer_index => {}
1377                 Some(
1378                     rl::Region::LateBound(..)
1379                     | rl::Region::LateBoundAnon(..)
1380                     | rl::Region::Free(..),
1381                 )
1382                 | None => {
1383                     self.has_late_bound_regions = Some(lt.span);
1384                 }
1385             }
1386         }
1387     }
1388
1389     fn has_late_bound_regions<'tcx>(
1390         tcx: TyCtxt<'tcx>,
1391         def_id: LocalDefId,
1392         generics: &'tcx hir::Generics<'tcx>,
1393         decl: &'tcx hir::FnDecl<'tcx>,
1394     ) -> Option<Span> {
1395         let mut visitor = LateBoundRegionsDetector {
1396             tcx,
1397             outer_index: ty::INNERMOST,
1398             has_late_bound_regions: None,
1399         };
1400         let late_bound_map = tcx.is_late_bound_map(def_id);
1401         let is_late_bound = |id| {
1402             let id = tcx.hir().local_def_id(id);
1403             late_bound_map.map_or(false, |(_, set)| set.contains(&id))
1404         };
1405         for param in generics.params {
1406             if let GenericParamKind::Lifetime { .. } = param.kind {
1407                 if is_late_bound(param.hir_id) {
1408                     return Some(param.span);
1409                 }
1410             }
1411         }
1412         visitor.visit_fn_decl(decl);
1413         visitor.has_late_bound_regions
1414     }
1415
1416     match node {
1417         Node::TraitItem(item) => match item.kind {
1418             hir::TraitItemKind::Fn(ref sig, _) => {
1419                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1420             }
1421             _ => None,
1422         },
1423         Node::ImplItem(item) => match item.kind {
1424             hir::ImplItemKind::Fn(ref sig, _) => {
1425                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1426             }
1427             _ => None,
1428         },
1429         Node::ForeignItem(item) => match item.kind {
1430             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1431                 has_late_bound_regions(tcx, item.def_id, generics, fn_decl)
1432             }
1433             _ => None,
1434         },
1435         Node::Item(item) => match item.kind {
1436             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1437                 has_late_bound_regions(tcx, item.def_id, generics, sig.decl)
1438             }
1439             _ => None,
1440         },
1441         _ => None,
1442     }
1443 }
1444
1445 struct AnonConstInParamTyDetector {
1446     in_param_ty: bool,
1447     found_anon_const_in_param_ty: bool,
1448     ct: HirId,
1449 }
1450
1451 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1452     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1453         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1454             let prev = self.in_param_ty;
1455             self.in_param_ty = true;
1456             self.visit_ty(ty);
1457             self.in_param_ty = prev;
1458         }
1459     }
1460
1461     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1462         if self.in_param_ty && self.ct == c.hir_id {
1463             self.found_anon_const_in_param_ty = true;
1464         } else {
1465             intravisit::walk_anon_const(self, c)
1466         }
1467     }
1468 }
1469
1470 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1471     use rustc_hir::*;
1472
1473     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1474
1475     let node = tcx.hir().get(hir_id);
1476     let parent_def_id = match node {
1477         Node::ImplItem(_)
1478         | Node::TraitItem(_)
1479         | Node::Variant(_)
1480         | Node::Ctor(..)
1481         | Node::Field(_) => {
1482             let parent_id = tcx.hir().get_parent_item(hir_id);
1483             Some(parent_id.to_def_id())
1484         }
1485         // FIXME(#43408) always enable this once `lazy_normalization` is
1486         // stable enough and does not need a feature gate anymore.
1487         Node::AnonConst(_) => {
1488             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1489
1490             let mut in_param_ty = false;
1491             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1492                 if let Some(generics) = node.generics() {
1493                     let mut visitor = AnonConstInParamTyDetector {
1494                         in_param_ty: false,
1495                         found_anon_const_in_param_ty: false,
1496                         ct: hir_id,
1497                     };
1498
1499                     visitor.visit_generics(generics);
1500                     in_param_ty = visitor.found_anon_const_in_param_ty;
1501                     break;
1502                 }
1503             }
1504
1505             if in_param_ty {
1506                 // We do not allow generic parameters in anon consts if we are inside
1507                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1508                 None
1509             } else if tcx.lazy_normalization() {
1510                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1511                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1512                     //
1513                     // struct Foo<const N: usize = { .. }>;
1514                     //        ^^^       ^          ^^^^^^ def id of this anon const
1515                     //        ^         ^ param_id
1516                     //        ^ parent_def_id
1517                     //
1518                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1519                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1520                     //
1521                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1522                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1523                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1524                     //
1525                     // We fix this by having this function return the parent's generics ourselves and truncating the
1526                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1527                     //
1528                     // For the above code example that means we want `substs: []`
1529                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1530                     // the def id of the `{ N + 1 }` anon const
1531                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1532                     //
1533                     // This has some implications for how we get the predicates available to the anon const
1534                     // see `explicit_predicates_of` for more information on this
1535                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1536                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1537                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1538                     // In the above example this would be .params[..N#0]
1539                     let params = generics.params[..param_def_idx as usize].to_owned();
1540                     let param_def_id_to_index =
1541                         params.iter().map(|param| (param.def_id, param.index)).collect();
1542
1543                     return ty::Generics {
1544                         // we set the parent of these generics to be our parent's parent so that we
1545                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1546                         // struct Foo<const N: usize, const M: usize = { ... }>;
1547                         parent: generics.parent,
1548                         parent_count: generics.parent_count,
1549                         params,
1550                         param_def_id_to_index,
1551                         has_self: generics.has_self,
1552                         has_late_bound_regions: generics.has_late_bound_regions,
1553                     };
1554                 }
1555
1556                 // HACK(eddyb) this provides the correct generics when
1557                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1558                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1559                 //
1560                 // Note that we do not supply the parent generics when using
1561                 // `min_const_generics`.
1562                 Some(parent_def_id.to_def_id())
1563             } else {
1564                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1565                 match parent_node {
1566                     // HACK(eddyb) this provides the correct generics for repeat
1567                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1568                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1569                     // as they shouldn't be able to cause query cycle errors.
1570                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1571                         if constant.hir_id() == hir_id =>
1572                     {
1573                         Some(parent_def_id.to_def_id())
1574                     }
1575                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1576                         if constant.hir_id == hir_id =>
1577                     {
1578                         Some(parent_def_id.to_def_id())
1579                     }
1580                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1581                         Some(tcx.typeck_root_def_id(def_id))
1582                     }
1583                     _ => None,
1584                 }
1585             }
1586         }
1587         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1588             Some(tcx.typeck_root_def_id(def_id))
1589         }
1590         Node::Item(item) => match item.kind {
1591             ItemKind::OpaqueTy(hir::OpaqueTy {
1592                 origin:
1593                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1594                 ..
1595             }) => Some(fn_def_id.to_def_id()),
1596             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1597                 let parent_id = tcx.hir().get_parent_item(hir_id);
1598                 assert_ne!(parent_id, CRATE_DEF_ID);
1599                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1600                 // Opaque types are always nested within another item, and
1601                 // inherit the generics of the item.
1602                 Some(parent_id.to_def_id())
1603             }
1604             _ => None,
1605         },
1606         _ => None,
1607     };
1608
1609     let mut opt_self = None;
1610     let mut allow_defaults = false;
1611
1612     let no_generics = hir::Generics::empty();
1613     let ast_generics = match node {
1614         Node::TraitItem(item) => &item.generics,
1615
1616         Node::ImplItem(item) => &item.generics,
1617
1618         Node::Item(item) => {
1619             match item.kind {
1620                 ItemKind::Fn(.., ref generics, _)
1621                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1622
1623                 ItemKind::TyAlias(_, ref generics)
1624                 | ItemKind::Enum(_, ref generics)
1625                 | ItemKind::Struct(_, ref generics)
1626                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1627                 | ItemKind::Union(_, ref generics) => {
1628                     allow_defaults = true;
1629                     generics
1630                 }
1631
1632                 ItemKind::Trait(_, _, ref generics, ..)
1633                 | ItemKind::TraitAlias(ref generics, ..) => {
1634                     // Add in the self type parameter.
1635                     //
1636                     // Something of a hack: use the node id for the trait, also as
1637                     // the node id for the Self type parameter.
1638                     let param_id = item.def_id;
1639
1640                     opt_self = Some(ty::GenericParamDef {
1641                         index: 0,
1642                         name: kw::SelfUpper,
1643                         def_id: param_id.to_def_id(),
1644                         pure_wrt_drop: false,
1645                         kind: ty::GenericParamDefKind::Type {
1646                             has_default: false,
1647                             object_lifetime_default: rl::Set1::Empty,
1648                             synthetic: false,
1649                         },
1650                     });
1651
1652                     allow_defaults = true;
1653                     generics
1654                 }
1655
1656                 _ => &no_generics,
1657             }
1658         }
1659
1660         Node::ForeignItem(item) => match item.kind {
1661             ForeignItemKind::Static(..) => &no_generics,
1662             ForeignItemKind::Fn(_, _, ref generics) => generics,
1663             ForeignItemKind::Type => &no_generics,
1664         },
1665
1666         _ => &no_generics,
1667     };
1668
1669     let has_self = opt_self.is_some();
1670     let mut parent_has_self = false;
1671     let mut own_start = has_self as u32;
1672     let parent_count = parent_def_id.map_or(0, |def_id| {
1673         let generics = tcx.generics_of(def_id);
1674         assert!(!has_self);
1675         parent_has_self = generics.has_self;
1676         own_start = generics.count() as u32;
1677         generics.parent_count + generics.params.len()
1678     });
1679
1680     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1681
1682     if let Some(opt_self) = opt_self {
1683         params.push(opt_self);
1684     }
1685
1686     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics);
1687     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1688         name: param.name.ident().name,
1689         index: own_start + i as u32,
1690         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1691         pure_wrt_drop: param.pure_wrt_drop,
1692         kind: ty::GenericParamDefKind::Lifetime,
1693     }));
1694
1695     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1696
1697     // Now create the real type and const parameters.
1698     let type_start = own_start - has_self as u32 + params.len() as u32;
1699     let mut i = 0;
1700
1701     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1702         GenericParamKind::Lifetime { .. } => None,
1703         GenericParamKind::Type { ref default, synthetic, .. } => {
1704             if !allow_defaults && default.is_some() {
1705                 if !tcx.features().default_type_parameter_fallback {
1706                     tcx.struct_span_lint_hir(
1707                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1708                         param.hir_id,
1709                         param.span,
1710                         |lint| {
1711                             lint.build(
1712                                 "defaults for type parameters are only allowed in \
1713                                  `struct`, `enum`, `type`, or `trait` definitions",
1714                             )
1715                             .emit();
1716                         },
1717                     );
1718                 }
1719             }
1720
1721             let kind = ty::GenericParamDefKind::Type {
1722                 has_default: default.is_some(),
1723                 object_lifetime_default: object_lifetime_defaults
1724                     .as_ref()
1725                     .map_or(rl::Set1::Empty, |o| o[i]),
1726                 synthetic,
1727             };
1728
1729             let param_def = ty::GenericParamDef {
1730                 index: type_start + i as u32,
1731                 name: param.name.ident().name,
1732                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1733                 pure_wrt_drop: param.pure_wrt_drop,
1734                 kind,
1735             };
1736             i += 1;
1737             Some(param_def)
1738         }
1739         GenericParamKind::Const { default, .. } => {
1740             if !allow_defaults && default.is_some() {
1741                 tcx.sess.span_err(
1742                     param.span,
1743                     "defaults for const parameters are only allowed in \
1744                     `struct`, `enum`, `type`, or `trait` definitions",
1745                 );
1746             }
1747
1748             let param_def = ty::GenericParamDef {
1749                 index: type_start + i as u32,
1750                 name: param.name.ident().name,
1751                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1752                 pure_wrt_drop: param.pure_wrt_drop,
1753                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1754             };
1755             i += 1;
1756             Some(param_def)
1757         }
1758     }));
1759
1760     // provide junk type parameter defs - the only place that
1761     // cares about anything but the length is instantiation,
1762     // and we don't do that for closures.
1763     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1764         let dummy_args = if gen.is_some() {
1765             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1766         } else {
1767             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1768         };
1769
1770         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1771             index: type_start + i as u32,
1772             name: Symbol::intern(arg),
1773             def_id,
1774             pure_wrt_drop: false,
1775             kind: ty::GenericParamDefKind::Type {
1776                 has_default: false,
1777                 object_lifetime_default: rl::Set1::Empty,
1778                 synthetic: false,
1779             },
1780         }));
1781     }
1782
1783     // provide junk type parameter defs for const blocks.
1784     if let Node::AnonConst(_) = node {
1785         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1786         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1787             params.push(ty::GenericParamDef {
1788                 index: type_start,
1789                 name: Symbol::intern("<const_ty>"),
1790                 def_id,
1791                 pure_wrt_drop: false,
1792                 kind: ty::GenericParamDefKind::Type {
1793                     has_default: false,
1794                     object_lifetime_default: rl::Set1::Empty,
1795                     synthetic: false,
1796                 },
1797             });
1798         }
1799     }
1800
1801     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1802
1803     ty::Generics {
1804         parent: parent_def_id,
1805         parent_count,
1806         params,
1807         param_def_id_to_index,
1808         has_self: has_self || parent_has_self,
1809         has_late_bound_regions: has_late_bound_regions(tcx, node),
1810     }
1811 }
1812
1813 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1814     generic_args.iter().any(|arg| match arg {
1815         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1816         hir::GenericArg::Infer(_) => true,
1817         _ => false,
1818     })
1819 }
1820
1821 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1822 /// use inference to provide suggestions for the appropriate type if possible.
1823 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1824     debug!(?ty);
1825     use hir::TyKind::*;
1826     match &ty.kind {
1827         Infer => true,
1828         Slice(ty) => is_suggestable_infer_ty(ty),
1829         Array(ty, length) => {
1830             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1831         }
1832         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1833         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1834         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1835         Path(hir::QPath::TypeRelative(ty, segment)) => {
1836             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1837         }
1838         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1839             ty_opt.map_or(false, is_suggestable_infer_ty)
1840                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1841         }
1842         _ => false,
1843     }
1844 }
1845
1846 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1847     if let hir::FnRetTy::Return(ty) = output {
1848         if is_suggestable_infer_ty(ty) {
1849             return Some(&*ty);
1850         }
1851     }
1852     None
1853 }
1854
1855 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1856     use rustc_hir::Node::*;
1857     use rustc_hir::*;
1858
1859     let def_id = def_id.expect_local();
1860     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1861
1862     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1863
1864     match tcx.hir().get(hir_id) {
1865         TraitItem(hir::TraitItem {
1866             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1867             ident,
1868             generics,
1869             ..
1870         })
1871         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1872         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1873             match get_infer_ret_ty(&sig.decl.output) {
1874                 Some(ty) => {
1875                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1876                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1877                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1878                         ty::ReErased => tcx.lifetimes.re_static,
1879                         _ => r,
1880                     });
1881                     let fn_sig = ty::Binder::dummy(fn_sig);
1882
1883                     let mut visitor = HirPlaceholderCollector::default();
1884                     visitor.visit_ty(ty);
1885                     let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1886                     let ret_ty = fn_sig.skip_binder().output();
1887                     if !ret_ty.references_error() {
1888                         if !ret_ty.is_closure() {
1889                             let ret_ty_str = match ret_ty.kind() {
1890                                 // Suggest a function pointer return type instead of a unique function definition
1891                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1892                                 // syntax)
1893                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1894                                 _ => ret_ty.to_string(),
1895                             };
1896                             diag.span_suggestion(
1897                                 ty.span,
1898                                 "replace with the correct return type",
1899                                 ret_ty_str,
1900                                 Applicability::MaybeIncorrect,
1901                             );
1902                         } else {
1903                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1904                             // to prevent the user from getting a papercut while trying to use the unique closure
1905                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1906                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1907                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1908                         }
1909                     }
1910                     diag.emit();
1911
1912                     fn_sig
1913                 }
1914                 None => <dyn AstConv<'_>>::ty_of_fn(
1915                     &icx,
1916                     hir_id,
1917                     sig.header.unsafety,
1918                     sig.header.abi,
1919                     sig.decl,
1920                     generics,
1921                     Some(ident.span),
1922                     None,
1923                 ),
1924             }
1925         }
1926
1927         TraitItem(hir::TraitItem {
1928             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1929             ident,
1930             generics,
1931             ..
1932         }) => <dyn AstConv<'_>>::ty_of_fn(
1933             &icx,
1934             hir_id,
1935             header.unsafety,
1936             header.abi,
1937             decl,
1938             generics,
1939             Some(ident.span),
1940             None,
1941         ),
1942
1943         ForeignItem(&hir::ForeignItem {
1944             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1945         }) => {
1946             let abi = tcx.hir().get_foreign_abi(hir_id);
1947             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1948         }
1949
1950         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1951             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1952             let inputs =
1953                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1954             ty::Binder::dummy(tcx.mk_fn_sig(
1955                 inputs,
1956                 ty,
1957                 false,
1958                 hir::Unsafety::Normal,
1959                 abi::Abi::Rust,
1960             ))
1961         }
1962
1963         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1964             // Closure signatures are not like other function
1965             // signatures and cannot be accessed through `fn_sig`. For
1966             // example, a closure signature excludes the `self`
1967             // argument. In any case they are embedded within the
1968             // closure type as part of the `ClosureSubsts`.
1969             //
1970             // To get the signature of a closure, you should use the
1971             // `sig` method on the `ClosureSubsts`:
1972             //
1973             //    substs.as_closure().sig(def_id, tcx)
1974             bug!(
1975                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1976             );
1977         }
1978
1979         x => {
1980             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1981         }
1982     }
1983 }
1984
1985 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1986     let icx = ItemCtxt::new(tcx, def_id);
1987     match tcx.hir().expect_item(def_id.expect_local()).kind {
1988         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1989             let selfty = tcx.type_of(def_id);
1990             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1991         }),
1992         _ => bug!(),
1993     }
1994 }
1995
1996 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1997     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1998     let item = tcx.hir().expect_item(def_id.expect_local());
1999     match &item.kind {
2000         hir::ItemKind::Impl(hir::Impl {
2001             polarity: hir::ImplPolarity::Negative(span),
2002             of_trait,
2003             ..
2004         }) => {
2005             if is_rustc_reservation {
2006                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2007                 tcx.sess.span_err(span, "reservation impls can't be negative");
2008             }
2009             ty::ImplPolarity::Negative
2010         }
2011         hir::ItemKind::Impl(hir::Impl {
2012             polarity: hir::ImplPolarity::Positive,
2013             of_trait: None,
2014             ..
2015         }) => {
2016             if is_rustc_reservation {
2017                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2018             }
2019             ty::ImplPolarity::Positive
2020         }
2021         hir::ItemKind::Impl(hir::Impl {
2022             polarity: hir::ImplPolarity::Positive,
2023             of_trait: Some(_),
2024             ..
2025         }) => {
2026             if is_rustc_reservation {
2027                 ty::ImplPolarity::Reservation
2028             } else {
2029                 ty::ImplPolarity::Positive
2030             }
2031         }
2032         item => bug!("impl_polarity: {:?} not an impl", item),
2033     }
2034 }
2035
2036 /// Returns the early-bound lifetimes declared in this generics
2037 /// listing. For anything other than fns/methods, this is just all
2038 /// the lifetimes that are declared. For fns or methods, we have to
2039 /// screen out those that do not appear in any where-clauses etc using
2040 /// `resolve_lifetime::early_bound_lifetimes`.
2041 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2042     tcx: TyCtxt<'tcx>,
2043     def_id: LocalDefId,
2044     generics: &'a hir::Generics<'a>,
2045 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2046     let late_bound_map = if generics.params.is_empty() {
2047         // This function may be called on `def_id == CRATE_DEF_ID`,
2048         // which makes `is_late_bound_map` ICE.  Don't even try if there
2049         // is no generic parameter.
2050         None
2051     } else {
2052         tcx.is_late_bound_map(def_id)
2053     };
2054     let is_late_bound = move |hir_id| {
2055         let id = tcx.hir().local_def_id(hir_id);
2056         late_bound_map.map_or(false, |(_, set)| set.contains(&id))
2057     };
2058     generics.params.iter().filter(move |param| match param.kind {
2059         GenericParamKind::Lifetime { .. } => !is_late_bound(param.hir_id),
2060         _ => false,
2061     })
2062 }
2063
2064 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2065 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2066 /// inferred constraints concerning which regions outlive other regions.
2067 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2068     debug!("predicates_defined_on({:?})", def_id);
2069     let mut result = tcx.explicit_predicates_of(def_id);
2070     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2071     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2072     if !inferred_outlives.is_empty() {
2073         debug!(
2074             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2075             def_id, inferred_outlives,
2076         );
2077         if result.predicates.is_empty() {
2078             result.predicates = inferred_outlives;
2079         } else {
2080             result.predicates = tcx
2081                 .arena
2082                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2083         }
2084     }
2085
2086     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2087     result
2088 }
2089
2090 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2091 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2092 /// `Self: Trait` predicates for traits.
2093 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2094     let mut result = tcx.predicates_defined_on(def_id);
2095
2096     if tcx.is_trait(def_id) {
2097         // For traits, add `Self: Trait` predicate. This is
2098         // not part of the predicates that a user writes, but it
2099         // is something that one must prove in order to invoke a
2100         // method or project an associated type.
2101         //
2102         // In the chalk setup, this predicate is not part of the
2103         // "predicates" for a trait item. But it is useful in
2104         // rustc because if you directly (e.g.) invoke a trait
2105         // method like `Trait::method(...)`, you must naturally
2106         // prove that the trait applies to the types that were
2107         // used, and adding the predicate into this list ensures
2108         // that this is done.
2109         //
2110         // We use a DUMMY_SP here as a way to signal trait bounds that come
2111         // from the trait itself that *shouldn't* be shown as the source of
2112         // an obligation and instead be skipped. Otherwise we'd use
2113         // `tcx.def_span(def_id);`
2114         let span = rustc_span::DUMMY_SP;
2115         result.predicates =
2116             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2117                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2118                 span,
2119             ))));
2120     }
2121     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2122     result
2123 }
2124
2125 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2126 /// N.B., this does not include any implied/inferred constraints.
2127 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2128     use rustc_hir::*;
2129
2130     debug!("explicit_predicates_of(def_id={:?})", def_id);
2131
2132     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2133     let node = tcx.hir().get(hir_id);
2134
2135     let mut is_trait = None;
2136     let mut is_default_impl_trait = None;
2137
2138     let icx = ItemCtxt::new(tcx, def_id);
2139
2140     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2141
2142     // We use an `IndexSet` to preserves order of insertion.
2143     // Preserving the order of insertion is important here so as not to break UI tests.
2144     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2145
2146     let ast_generics = match node {
2147         Node::TraitItem(item) => &item.generics,
2148
2149         Node::ImplItem(item) => &item.generics,
2150
2151         Node::Item(item) => {
2152             match item.kind {
2153                 ItemKind::Impl(ref impl_) => {
2154                     if impl_.defaultness.is_default() {
2155                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2156                     }
2157                     &impl_.generics
2158                 }
2159                 ItemKind::Fn(.., ref generics, _)
2160                 | ItemKind::TyAlias(_, ref generics)
2161                 | ItemKind::Enum(_, ref generics)
2162                 | ItemKind::Struct(_, ref generics)
2163                 | ItemKind::Union(_, ref generics) => generics,
2164
2165                 ItemKind::Trait(_, _, ref generics, ..) => {
2166                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2167                     generics
2168                 }
2169                 ItemKind::TraitAlias(ref generics, _) => {
2170                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2171                     generics
2172                 }
2173                 ItemKind::OpaqueTy(OpaqueTy {
2174                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2175                     ..
2176                 }) => {
2177                     // return-position impl trait
2178                     //
2179                     // We don't inherit predicates from the parent here:
2180                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2181                     // then the return type is `f::<'static, T>::{{opaque}}`.
2182                     //
2183                     // If we inherited the predicates of `f` then we would
2184                     // require that `T: 'static` to show that the return
2185                     // type is well-formed.
2186                     //
2187                     // The only way to have something with this opaque type
2188                     // is from the return type of the containing function,
2189                     // which will ensure that the function's predicates
2190                     // hold.
2191                     return ty::GenericPredicates { parent: None, predicates: &[] };
2192                 }
2193                 ItemKind::OpaqueTy(OpaqueTy {
2194                     ref generics,
2195                     origin: hir::OpaqueTyOrigin::TyAlias,
2196                     ..
2197                 }) => {
2198                     // type-alias impl trait
2199                     generics
2200                 }
2201
2202                 _ => NO_GENERICS,
2203             }
2204         }
2205
2206         Node::ForeignItem(item) => match item.kind {
2207             ForeignItemKind::Static(..) => NO_GENERICS,
2208             ForeignItemKind::Fn(_, _, ref generics) => generics,
2209             ForeignItemKind::Type => NO_GENERICS,
2210         },
2211
2212         _ => NO_GENERICS,
2213     };
2214
2215     let generics = tcx.generics_of(def_id);
2216     let parent_count = generics.parent_count as u32;
2217     let has_own_self = generics.has_self && parent_count == 0;
2218
2219     // Below we'll consider the bounds on the type parameters (including `Self`)
2220     // and the explicit where-clauses, but to get the full set of predicates
2221     // on a trait we need to add in the supertrait bounds and bounds found on
2222     // associated types.
2223     if let Some(_trait_ref) = is_trait {
2224         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2225     }
2226
2227     // In default impls, we can assume that the self type implements
2228     // the trait. So in:
2229     //
2230     //     default impl Foo for Bar { .. }
2231     //
2232     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2233     // (see below). Recall that a default impl is not itself an impl, but rather a
2234     // set of defaults that can be incorporated into another impl.
2235     if let Some(trait_ref) = is_default_impl_trait {
2236         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2237     }
2238
2239     // Collect the region predicates that were declared inline as
2240     // well. In the case of parameters declared on a fn or method, we
2241     // have to be careful to only iterate over early-bound regions.
2242     let mut index = parent_count + has_own_self as u32;
2243     for param in early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics) {
2244         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2245             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2246             index,
2247             name: param.name.ident().name,
2248         }));
2249         index += 1;
2250
2251         match param.kind {
2252             GenericParamKind::Lifetime { .. } => {
2253                 param.bounds.iter().for_each(|bound| match bound {
2254                     hir::GenericBound::Outlives(lt) => {
2255                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2256                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2257                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2258                     }
2259                     _ => bug!(),
2260                 });
2261             }
2262             _ => bug!(),
2263         }
2264     }
2265
2266     // Collect the predicates that were written inline by the user on each
2267     // type parameter (e.g., `<T: Foo>`).
2268     for param in ast_generics.params {
2269         match param.kind {
2270             // We already dealt with early bound lifetimes above.
2271             GenericParamKind::Lifetime { .. } => (),
2272             GenericParamKind::Type { .. } => {
2273                 let name = param.name.ident().name;
2274                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2275                 index += 1;
2276
2277                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2278                 // Params are implicitly sized unless a `?Sized` bound is found
2279                 <dyn AstConv<'_>>::add_implicitly_sized(
2280                     &icx,
2281                     &mut bounds,
2282                     param.bounds,
2283                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2284                     param.span,
2285                 );
2286                 predicates.extend(bounds.predicates(tcx, param_ty));
2287             }
2288             GenericParamKind::Const { .. } => {
2289                 // Bounds on const parameters are currently not possible.
2290                 debug_assert!(param.bounds.is_empty());
2291                 index += 1;
2292             }
2293         }
2294     }
2295
2296     // Add in the bounds that appear in the where-clause.
2297     let where_clause = &ast_generics.where_clause;
2298     for predicate in where_clause.predicates {
2299         match predicate {
2300             hir::WherePredicate::BoundPredicate(bound_pred) => {
2301                 let ty = icx.to_ty(bound_pred.bounded_ty);
2302                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2303
2304                 // Keep the type around in a dummy predicate, in case of no bounds.
2305                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2306                 // is still checked for WF.
2307                 if bound_pred.bounds.is_empty() {
2308                     if let ty::Param(_) = ty.kind() {
2309                         // This is a `where T:`, which can be in the HIR from the
2310                         // transformation that moves `?Sized` to `T`'s declaration.
2311                         // We can skip the predicate because type parameters are
2312                         // trivially WF, but also we *should*, to avoid exposing
2313                         // users who never wrote `where Type:,` themselves, to
2314                         // compiler/tooling bugs from not handling WF predicates.
2315                     } else {
2316                         let span = bound_pred.bounded_ty.span;
2317                         let re_root_empty = tcx.lifetimes.re_root_empty;
2318                         let predicate = ty::Binder::bind_with_vars(
2319                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2320                                 ty,
2321                                 re_root_empty,
2322                             )),
2323                             bound_vars,
2324                         );
2325                         predicates.insert((predicate.to_predicate(tcx), span));
2326                     }
2327                 }
2328
2329                 let mut bounds = Bounds::default();
2330                 <dyn AstConv<'_>>::add_bounds(
2331                     &icx,
2332                     ty,
2333                     bound_pred.bounds.iter(),
2334                     &mut bounds,
2335                     bound_vars,
2336                 );
2337                 predicates.extend(bounds.predicates(tcx, ty));
2338             }
2339
2340             hir::WherePredicate::RegionPredicate(region_pred) => {
2341                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2342                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2343                     let (r2, span) = match bound {
2344                         hir::GenericBound::Outlives(lt) => {
2345                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2346                         }
2347                         _ => bug!(),
2348                     };
2349                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2350                         ty::OutlivesPredicate(r1, r2),
2351                     ))
2352                     .to_predicate(icx.tcx);
2353
2354                     (pred, span)
2355                 }))
2356             }
2357
2358             hir::WherePredicate::EqPredicate(..) => {
2359                 // FIXME(#20041)
2360             }
2361         }
2362     }
2363
2364     if tcx.features().generic_const_exprs {
2365         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2366     }
2367
2368     let mut predicates: Vec<_> = predicates.into_iter().collect();
2369
2370     // Subtle: before we store the predicates into the tcx, we
2371     // sort them so that predicates like `T: Foo<Item=U>` come
2372     // before uses of `U`.  This avoids false ambiguity errors
2373     // in trait checking. See `setup_constraining_predicates`
2374     // for details.
2375     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2376         let self_ty = tcx.type_of(def_id);
2377         let trait_ref = tcx.impl_trait_ref(def_id);
2378         cgp::setup_constraining_predicates(
2379             tcx,
2380             &mut predicates,
2381             trait_ref,
2382             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2383         );
2384     }
2385
2386     let result = ty::GenericPredicates {
2387         parent: generics.parent,
2388         predicates: tcx.arena.alloc_from_iter(predicates),
2389     };
2390     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2391     result
2392 }
2393
2394 fn const_evaluatable_predicates_of<'tcx>(
2395     tcx: TyCtxt<'tcx>,
2396     def_id: LocalDefId,
2397 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2398     struct ConstCollector<'tcx> {
2399         tcx: TyCtxt<'tcx>,
2400         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2401     }
2402
2403     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2404         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2405             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2406             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2407             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2408                 assert_eq!(uv.promoted, None);
2409                 let span = self.tcx.hir().span(c.hir_id);
2410                 self.preds.insert((
2411                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2412                         .to_predicate(self.tcx),
2413                     span,
2414                 ));
2415             }
2416         }
2417
2418         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2419             // Do not look into const param defaults,
2420             // these get checked when they are actually instantiated.
2421             //
2422             // We do not want the following to error:
2423             //
2424             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2425             //     struct Bar<const N: usize>(Foo<N, 3>);
2426         }
2427     }
2428
2429     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2430     let node = tcx.hir().get(hir_id);
2431
2432     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2433     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2434         if let Some(of_trait) = &impl_.of_trait {
2435             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2436             collector.visit_trait_ref(of_trait);
2437         }
2438
2439         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2440         collector.visit_ty(impl_.self_ty);
2441     }
2442
2443     if let Some(generics) = node.generics() {
2444         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2445         collector.visit_generics(generics);
2446     }
2447
2448     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2449         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2450         collector.visit_fn_decl(fn_sig.decl);
2451     }
2452     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2453
2454     collector.preds
2455 }
2456
2457 fn trait_explicit_predicates_and_bounds(
2458     tcx: TyCtxt<'_>,
2459     def_id: LocalDefId,
2460 ) -> ty::GenericPredicates<'_> {
2461     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2462     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2463 }
2464
2465 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2466     let def_kind = tcx.def_kind(def_id);
2467     if let DefKind::Trait = def_kind {
2468         // Remove bounds on associated types from the predicates, they will be
2469         // returned by `explicit_item_bounds`.
2470         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2471         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2472
2473         let is_assoc_item_ty = |ty: Ty<'_>| {
2474             // For a predicate from a where clause to become a bound on an
2475             // associated type:
2476             // * It must use the identity substs of the item.
2477             //     * Since any generic parameters on the item are not in scope,
2478             //       this means that the item is not a GAT, and its identity
2479             //       substs are the same as the trait's.
2480             // * It must be an associated type for this trait (*not* a
2481             //   supertrait).
2482             if let ty::Projection(projection) = ty.kind() {
2483                 projection.substs == trait_identity_substs
2484                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2485             } else {
2486                 false
2487             }
2488         };
2489
2490         let predicates: Vec<_> = predicates_and_bounds
2491             .predicates
2492             .iter()
2493             .copied()
2494             .filter(|(pred, _)| match pred.kind().skip_binder() {
2495                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2496                 ty::PredicateKind::Projection(proj) => {
2497                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2498                 }
2499                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2500                 _ => true,
2501             })
2502             .collect();
2503         if predicates.len() == predicates_and_bounds.predicates.len() {
2504             predicates_and_bounds
2505         } else {
2506             ty::GenericPredicates {
2507                 parent: predicates_and_bounds.parent,
2508                 predicates: tcx.arena.alloc_slice(&predicates),
2509             }
2510         }
2511     } else {
2512         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2513             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2514             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2515                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2516                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2517                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2518                 //
2519                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2520                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2521                 //        ^^^                                             explicit_predicates_of on
2522                 //        parent item we dont have set as the
2523                 //        parent of generics returned by `generics_of`
2524                 //
2525                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2526                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2527                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2528                 return tcx.explicit_predicates_of(item_def_id);
2529             }
2530         }
2531         gather_explicit_predicates_of(tcx, def_id)
2532     }
2533 }
2534
2535 /// Converts a specific `GenericBound` from the AST into a set of
2536 /// predicates that apply to the self type. A vector is returned
2537 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2538 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2539 /// and `<T as Bar>::X == i32`).
2540 fn predicates_from_bound<'tcx>(
2541     astconv: &dyn AstConv<'tcx>,
2542     param_ty: Ty<'tcx>,
2543     bound: &'tcx hir::GenericBound<'tcx>,
2544     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2545 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2546     let mut bounds = Bounds::default();
2547     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2548     bounds.predicates(astconv.tcx(), param_ty).collect()
2549 }
2550
2551 fn compute_sig_of_foreign_fn_decl<'tcx>(
2552     tcx: TyCtxt<'tcx>,
2553     def_id: DefId,
2554     decl: &'tcx hir::FnDecl<'tcx>,
2555     abi: abi::Abi,
2556     ident: Ident,
2557 ) -> ty::PolyFnSig<'tcx> {
2558     let unsafety = if abi == abi::Abi::RustIntrinsic {
2559         intrinsic_operation_unsafety(tcx.item_name(def_id))
2560     } else {
2561         hir::Unsafety::Unsafe
2562     };
2563     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2564     let fty = <dyn AstConv<'_>>::ty_of_fn(
2565         &ItemCtxt::new(tcx, def_id),
2566         hir_id,
2567         unsafety,
2568         abi,
2569         decl,
2570         &hir::Generics::empty(),
2571         Some(ident.span),
2572         None,
2573     );
2574
2575     // Feature gate SIMD types in FFI, since I am not sure that the
2576     // ABIs are handled at all correctly. -huonw
2577     if abi != abi::Abi::RustIntrinsic
2578         && abi != abi::Abi::PlatformIntrinsic
2579         && !tcx.features().simd_ffi
2580     {
2581         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2582             if ty.is_simd() {
2583                 let snip = tcx
2584                     .sess
2585                     .source_map()
2586                     .span_to_snippet(ast_ty.span)
2587                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2588                 tcx.sess
2589                     .struct_span_err(
2590                         ast_ty.span,
2591                         &format!(
2592                             "use of SIMD type{} in FFI is highly experimental and \
2593                              may result in invalid code",
2594                             snip
2595                         ),
2596                     )
2597                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2598                     .emit();
2599             }
2600         };
2601         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2602             check(input, *ty)
2603         }
2604         if let hir::FnRetTy::Return(ref ty) = decl.output {
2605             check(ty, fty.output().skip_binder())
2606         }
2607     }
2608
2609     fty
2610 }
2611
2612 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2613     match tcx.hir().get_if_local(def_id) {
2614         Some(Node::ForeignItem(..)) => true,
2615         Some(_) => false,
2616         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2617     }
2618 }
2619
2620 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2621     match tcx.hir().get_if_local(def_id) {
2622         Some(Node::Expr(&rustc_hir::Expr {
2623             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2624             ..
2625         })) => tcx.hir().body(body_id).generator_kind(),
2626         Some(_) => None,
2627         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2628     }
2629 }
2630
2631 fn from_target_feature(
2632     tcx: TyCtxt<'_>,
2633     id: DefId,
2634     attr: &ast::Attribute,
2635     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2636     target_features: &mut Vec<Symbol>,
2637 ) {
2638     let Some(list) = attr.meta_item_list() else { return };
2639     let bad_item = |span| {
2640         let msg = "malformed `target_feature` attribute input";
2641         let code = "enable = \"..\"".to_owned();
2642         tcx.sess
2643             .struct_span_err(span, msg)
2644             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2645             .emit();
2646     };
2647     let rust_features = tcx.features();
2648     for item in list {
2649         // Only `enable = ...` is accepted in the meta-item list.
2650         if !item.has_name(sym::enable) {
2651             bad_item(item.span());
2652             continue;
2653         }
2654
2655         // Must be of the form `enable = "..."` (a string).
2656         let Some(value) = item.value_str() else {
2657             bad_item(item.span());
2658             continue;
2659         };
2660
2661         // We allow comma separation to enable multiple features.
2662         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2663             let Some(feature_gate) = supported_target_features.get(feature) else {
2664                 let msg =
2665                     format!("the feature named `{}` is not valid for this target", feature);
2666                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2667                 err.span_label(
2668                     item.span(),
2669                     format!("`{}` is not valid for this target", feature),
2670                 );
2671                 if let Some(stripped) = feature.strip_prefix('+') {
2672                     let valid = supported_target_features.contains_key(stripped);
2673                     if valid {
2674                         err.help("consider removing the leading `+` in the feature name");
2675                     }
2676                 }
2677                 err.emit();
2678                 return None;
2679             };
2680
2681             // Only allow features whose feature gates have been enabled.
2682             let allowed = match feature_gate.as_ref().copied() {
2683                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2684                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2685                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2686                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2687                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2688                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2689                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2690                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2691                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2692                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2693                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2694                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2695                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2696                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2697                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2698                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2699                 Some(name) => bug!("unknown target feature gate {}", name),
2700                 None => true,
2701             };
2702             if !allowed && id.is_local() {
2703                 feature_err(
2704                     &tcx.sess.parse_sess,
2705                     feature_gate.unwrap(),
2706                     item.span(),
2707                     &format!("the target feature `{}` is currently unstable", feature),
2708                 )
2709                 .emit();
2710             }
2711             Some(Symbol::intern(feature))
2712         }));
2713     }
2714 }
2715
2716 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2717     use rustc_middle::mir::mono::Linkage::*;
2718
2719     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2720     // applicable to variable declarations and may not really make sense for
2721     // Rust code in the first place but allow them anyway and trust that the
2722     // user knows what they're doing. Who knows, unanticipated use cases may pop
2723     // up in the future.
2724     //
2725     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2726     // and don't have to be, LLVM treats them as no-ops.
2727     match name {
2728         "appending" => Appending,
2729         "available_externally" => AvailableExternally,
2730         "common" => Common,
2731         "extern_weak" => ExternalWeak,
2732         "external" => External,
2733         "internal" => Internal,
2734         "linkonce" => LinkOnceAny,
2735         "linkonce_odr" => LinkOnceODR,
2736         "private" => Private,
2737         "weak" => WeakAny,
2738         "weak_odr" => WeakODR,
2739         _ => {
2740             let span = tcx.hir().span_if_local(def_id);
2741             if let Some(span) = span {
2742                 tcx.sess.span_fatal(span, "invalid linkage specified")
2743             } else {
2744                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2745             }
2746         }
2747     }
2748 }
2749
2750 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2751     let attrs = tcx.get_attrs(id);
2752
2753     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2754     if tcx.should_inherit_track_caller(id) {
2755         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2756     }
2757
2758     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2759     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2760         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2761             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2762         }
2763     }
2764
2765     // The panic_no_unwind function called by TerminatorKind::Abort will never
2766     // unwind. If the panic handler that it invokes unwind then it will simply
2767     // call the panic handler again.
2768     if Some(id) == tcx.lang_items().panic_no_unwind() {
2769         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2770     }
2771
2772     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2773
2774     let mut inline_span = None;
2775     let mut link_ordinal_span = None;
2776     let mut no_sanitize_span = None;
2777     for attr in attrs.iter() {
2778         if attr.has_name(sym::cold) {
2779             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2780         } else if attr.has_name(sym::rustc_allocator) {
2781             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2782         } else if attr.has_name(sym::ffi_returns_twice) {
2783             if tcx.is_foreign_item(id) {
2784                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2785             } else {
2786                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2787                 struct_span_err!(
2788                     tcx.sess,
2789                     attr.span,
2790                     E0724,
2791                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2792                 )
2793                 .emit();
2794             }
2795         } else if attr.has_name(sym::ffi_pure) {
2796             if tcx.is_foreign_item(id) {
2797                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2798                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2799                     struct_span_err!(
2800                         tcx.sess,
2801                         attr.span,
2802                         E0757,
2803                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2804                     )
2805                     .emit();
2806                 } else {
2807                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2808                 }
2809             } else {
2810                 // `#[ffi_pure]` is only allowed on foreign functions
2811                 struct_span_err!(
2812                     tcx.sess,
2813                     attr.span,
2814                     E0755,
2815                     "`#[ffi_pure]` may only be used on foreign functions"
2816                 )
2817                 .emit();
2818             }
2819         } else if attr.has_name(sym::ffi_const) {
2820             if tcx.is_foreign_item(id) {
2821                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2822             } else {
2823                 // `#[ffi_const]` is only allowed on foreign functions
2824                 struct_span_err!(
2825                     tcx.sess,
2826                     attr.span,
2827                     E0756,
2828                     "`#[ffi_const]` may only be used on foreign functions"
2829                 )
2830                 .emit();
2831             }
2832         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2833             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2834         } else if attr.has_name(sym::naked) {
2835             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2836         } else if attr.has_name(sym::no_mangle) {
2837             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2838         } else if attr.has_name(sym::no_coverage) {
2839             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2840         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2841             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2842         } else if attr.has_name(sym::used) {
2843             let inner = attr.meta_item_list();
2844             match inner.as_deref() {
2845                 Some([item]) if item.has_name(sym::linker) => {
2846                     if !tcx.features().used_with_arg {
2847                         feature_err(
2848                             &tcx.sess.parse_sess,
2849                             sym::used_with_arg,
2850                             attr.span,
2851                             "`#[used(linker)]` is currently unstable",
2852                         )
2853                         .emit();
2854                     }
2855                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2856                 }
2857                 Some([item]) if item.has_name(sym::compiler) => {
2858                     if !tcx.features().used_with_arg {
2859                         feature_err(
2860                             &tcx.sess.parse_sess,
2861                             sym::used_with_arg,
2862                             attr.span,
2863                             "`#[used(compiler)]` is currently unstable",
2864                         )
2865                         .emit();
2866                     }
2867                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2868                 }
2869                 Some(_) => {
2870                     tcx.sess
2871                         .struct_span_err(
2872                             attr.span,
2873                             "expected `used`, `used(compiler)` or `used(linker)`",
2874                         )
2875                         .emit();
2876                 }
2877                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2878             }
2879         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2880             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2881                 struct_span_err!(
2882                     tcx.sess,
2883                     attr.span,
2884                     E0776,
2885                     "`#[cmse_nonsecure_entry]` requires C ABI"
2886                 )
2887                 .emit();
2888             }
2889             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2890                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2891                     .emit();
2892             }
2893             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2894         } else if attr.has_name(sym::thread_local) {
2895             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2896         } else if attr.has_name(sym::track_caller) {
2897             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2898                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2899                     .emit();
2900             }
2901             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2902                 feature_err(
2903                     &tcx.sess.parse_sess,
2904                     sym::closure_track_caller,
2905                     attr.span,
2906                     "`#[track_caller]` on closures is currently unstable",
2907                 )
2908                 .emit();
2909             }
2910             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2911         } else if attr.has_name(sym::export_name) {
2912             if let Some(s) = attr.value_str() {
2913                 if s.as_str().contains('\0') {
2914                     // `#[export_name = ...]` will be converted to a null-terminated string,
2915                     // so it may not contain any null characters.
2916                     struct_span_err!(
2917                         tcx.sess,
2918                         attr.span,
2919                         E0648,
2920                         "`export_name` may not contain null characters"
2921                     )
2922                     .emit();
2923                 }
2924                 codegen_fn_attrs.export_name = Some(s);
2925             }
2926         } else if attr.has_name(sym::target_feature) {
2927             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2928                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2929                     // The `#[target_feature]` attribute is allowed on
2930                     // WebAssembly targets on all functions, including safe
2931                     // ones. Other targets require that `#[target_feature]` is
2932                     // only applied to unsafe functions (pending the
2933                     // `target_feature_11` feature) because on most targets
2934                     // execution of instructions that are not supported is
2935                     // considered undefined behavior. For WebAssembly which is a
2936                     // 100% safe target at execution time it's not possible to
2937                     // execute undefined instructions, and even if a future
2938                     // feature was added in some form for this it would be a
2939                     // deterministic trap. There is no undefined behavior when
2940                     // executing WebAssembly so `#[target_feature]` is allowed
2941                     // on safe functions (but again, only for WebAssembly)
2942                     //
2943                     // Note that this is also allowed if `actually_rustdoc` so
2944                     // if a target is documenting some wasm-specific code then
2945                     // it's not spuriously denied.
2946                 } else if !tcx.features().target_feature_11 {
2947                     let mut err = feature_err(
2948                         &tcx.sess.parse_sess,
2949                         sym::target_feature_11,
2950                         attr.span,
2951                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2952                     );
2953                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2954                     err.emit();
2955                 } else if let Some(local_id) = id.as_local() {
2956                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2957                 }
2958             }
2959             from_target_feature(
2960                 tcx,
2961                 id,
2962                 attr,
2963                 supported_target_features,
2964                 &mut codegen_fn_attrs.target_features,
2965             );
2966         } else if attr.has_name(sym::linkage) {
2967             if let Some(val) = attr.value_str() {
2968                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2969             }
2970         } else if attr.has_name(sym::link_section) {
2971             if let Some(val) = attr.value_str() {
2972                 if val.as_str().bytes().any(|b| b == 0) {
2973                     let msg = format!(
2974                         "illegal null byte in link_section \
2975                          value: `{}`",
2976                         &val
2977                     );
2978                     tcx.sess.span_err(attr.span, &msg);
2979                 } else {
2980                     codegen_fn_attrs.link_section = Some(val);
2981                 }
2982             }
2983         } else if attr.has_name(sym::link_name) {
2984             codegen_fn_attrs.link_name = attr.value_str();
2985         } else if attr.has_name(sym::link_ordinal) {
2986             link_ordinal_span = Some(attr.span);
2987             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2988                 codegen_fn_attrs.link_ordinal = ordinal;
2989             }
2990         } else if attr.has_name(sym::no_sanitize) {
2991             no_sanitize_span = Some(attr.span);
2992             if let Some(list) = attr.meta_item_list() {
2993                 for item in list.iter() {
2994                     if item.has_name(sym::address) {
2995                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2996                     } else if item.has_name(sym::cfi) {
2997                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2998                     } else if item.has_name(sym::memory) {
2999                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
3000                     } else if item.has_name(sym::memtag) {
3001                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
3002                     } else if item.has_name(sym::thread) {
3003                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
3004                     } else if item.has_name(sym::hwaddress) {
3005                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
3006                     } else {
3007                         tcx.sess
3008                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
3009                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
3010                             .emit();
3011                     }
3012                 }
3013             }
3014         } else if attr.has_name(sym::instruction_set) {
3015             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3016                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3017                     [NestedMetaItem::MetaItem(set)] => {
3018                         let segments =
3019                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3020                         match segments.as_slice() {
3021                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3022                                 if !tcx.sess.target.has_thumb_interworking {
3023                                     struct_span_err!(
3024                                         tcx.sess.diagnostic(),
3025                                         attr.span,
3026                                         E0779,
3027                                         "target does not support `#[instruction_set]`"
3028                                     )
3029                                     .emit();
3030                                     None
3031                                 } else if segments[1] == sym::a32 {
3032                                     Some(InstructionSetAttr::ArmA32)
3033                                 } else if segments[1] == sym::t32 {
3034                                     Some(InstructionSetAttr::ArmT32)
3035                                 } else {
3036                                     unreachable!()
3037                                 }
3038                             }
3039                             _ => {
3040                                 struct_span_err!(
3041                                     tcx.sess.diagnostic(),
3042                                     attr.span,
3043                                     E0779,
3044                                     "invalid instruction set specified",
3045                                 )
3046                                 .emit();
3047                                 None
3048                             }
3049                         }
3050                     }
3051                     [] => {
3052                         struct_span_err!(
3053                             tcx.sess.diagnostic(),
3054                             attr.span,
3055                             E0778,
3056                             "`#[instruction_set]` requires an argument"
3057                         )
3058                         .emit();
3059                         None
3060                     }
3061                     _ => {
3062                         struct_span_err!(
3063                             tcx.sess.diagnostic(),
3064                             attr.span,
3065                             E0779,
3066                             "cannot specify more than one instruction set"
3067                         )
3068                         .emit();
3069                         None
3070                     }
3071                 },
3072                 _ => {
3073                     struct_span_err!(
3074                         tcx.sess.diagnostic(),
3075                         attr.span,
3076                         E0778,
3077                         "must specify an instruction set"
3078                     )
3079                     .emit();
3080                     None
3081                 }
3082             };
3083         } else if attr.has_name(sym::repr) {
3084             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3085                 Some(items) => match items.as_slice() {
3086                     [item] => match item.name_value_literal() {
3087                         Some((sym::align, literal)) => {
3088                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3089
3090                             match alignment {
3091                                 Ok(align) => Some(align),
3092                                 Err(msg) => {
3093                                     struct_span_err!(
3094                                         tcx.sess.diagnostic(),
3095                                         attr.span,
3096                                         E0589,
3097                                         "invalid `repr(align)` attribute: {}",
3098                                         msg
3099                                     )
3100                                     .emit();
3101
3102                                     None
3103                                 }
3104                             }
3105                         }
3106                         _ => None,
3107                     },
3108                     [] => None,
3109                     _ => None,
3110                 },
3111                 None => None,
3112             };
3113         }
3114     }
3115
3116     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3117         if !attr.has_name(sym::inline) {
3118             return ia;
3119         }
3120         match attr.meta_kind() {
3121             Some(MetaItemKind::Word) => InlineAttr::Hint,
3122             Some(MetaItemKind::List(ref items)) => {
3123                 inline_span = Some(attr.span);
3124                 if items.len() != 1 {
3125                     struct_span_err!(
3126                         tcx.sess.diagnostic(),
3127                         attr.span,
3128                         E0534,
3129                         "expected one argument"
3130                     )
3131                     .emit();
3132                     InlineAttr::None
3133                 } else if list_contains_name(&items, sym::always) {
3134                     InlineAttr::Always
3135                 } else if list_contains_name(&items, sym::never) {
3136                     InlineAttr::Never
3137                 } else {
3138                     struct_span_err!(
3139                         tcx.sess.diagnostic(),
3140                         items[0].span(),
3141                         E0535,
3142                         "invalid argument"
3143                     )
3144                     .emit();
3145
3146                     InlineAttr::None
3147                 }
3148             }
3149             Some(MetaItemKind::NameValue(_)) => ia,
3150             None => ia,
3151         }
3152     });
3153
3154     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3155         if !attr.has_name(sym::optimize) {
3156             return ia;
3157         }
3158         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3159         match attr.meta_kind() {
3160             Some(MetaItemKind::Word) => {
3161                 err(attr.span, "expected one argument");
3162                 ia
3163             }
3164             Some(MetaItemKind::List(ref items)) => {
3165                 inline_span = Some(attr.span);
3166                 if items.len() != 1 {
3167                     err(attr.span, "expected one argument");
3168                     OptimizeAttr::None
3169                 } else if list_contains_name(&items, sym::size) {
3170                     OptimizeAttr::Size
3171                 } else if list_contains_name(&items, sym::speed) {
3172                     OptimizeAttr::Speed
3173                 } else {
3174                     err(items[0].span(), "invalid argument");
3175                     OptimizeAttr::None
3176                 }
3177             }
3178             Some(MetaItemKind::NameValue(_)) => ia,
3179             None => ia,
3180         }
3181     });
3182
3183     // #73631: closures inherit `#[target_feature]` annotations
3184     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3185         let owner_id = tcx.parent(id).expect("closure should have a parent");
3186         codegen_fn_attrs
3187             .target_features
3188             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3189     }
3190
3191     // If a function uses #[target_feature] it can't be inlined into general
3192     // purpose functions as they wouldn't have the right target features
3193     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3194     // respected.
3195     if !codegen_fn_attrs.target_features.is_empty() {
3196         if codegen_fn_attrs.inline == InlineAttr::Always {
3197             if let Some(span) = inline_span {
3198                 tcx.sess.span_err(
3199                     span,
3200                     "cannot use `#[inline(always)]` with \
3201                      `#[target_feature]`",
3202                 );
3203             }
3204         }
3205     }
3206
3207     if !codegen_fn_attrs.no_sanitize.is_empty() {
3208         if codegen_fn_attrs.inline == InlineAttr::Always {
3209             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3210                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3211                 tcx.struct_span_lint_hir(
3212                     lint::builtin::INLINE_NO_SANITIZE,
3213                     hir_id,
3214                     no_sanitize_span,
3215                     |lint| {
3216                         lint.build("`no_sanitize` will have no effect after inlining")
3217                             .span_note(inline_span, "inlining requested here")
3218                             .emit();
3219                     },
3220                 )
3221             }
3222         }
3223     }
3224
3225     // Weak lang items have the same semantics as "std internal" symbols in the
3226     // sense that they're preserved through all our LTO passes and only
3227     // strippable by the linker.
3228     //
3229     // Additionally weak lang items have predetermined symbol names.
3230     if tcx.is_weak_lang_item(id) {
3231         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3232     }
3233     if let Some(name) = weak_lang_items::link_name(attrs) {
3234         codegen_fn_attrs.export_name = Some(name);
3235         codegen_fn_attrs.link_name = Some(name);
3236     }
3237     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3238
3239     // Internal symbols to the standard library all have no_mangle semantics in
3240     // that they have defined symbol names present in the function name. This
3241     // also applies to weak symbols where they all have known symbol names.
3242     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3243         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3244     }
3245
3246     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3247     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3248     // intrinsic functions.
3249     if let Some(name) = &codegen_fn_attrs.link_name {
3250         if name.as_str().starts_with("llvm.") {
3251             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3252         }
3253     }
3254
3255     codegen_fn_attrs
3256 }
3257
3258 /// Computes the set of target features used in a function for the purposes of
3259 /// inline assembly.
3260 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, id: DefId) -> &'tcx FxHashSet<Symbol> {
3261     let mut target_features = tcx.sess.target_features.clone();
3262     let attrs = tcx.codegen_fn_attrs(id);
3263     target_features.extend(&attrs.target_features);
3264     match attrs.instruction_set {
3265         None => {}
3266         Some(InstructionSetAttr::ArmA32) => {
3267             target_features.remove(&sym::thumb_mode);
3268         }
3269         Some(InstructionSetAttr::ArmT32) => {
3270             target_features.insert(sym::thumb_mode);
3271         }
3272     }
3273     tcx.arena.alloc(target_features)
3274 }
3275
3276 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3277 /// applied to the method prototype.
3278 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3279     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3280         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3281         && let Some(trait_item) = impl_item.trait_item_def_id
3282     {
3283         return tcx
3284             .codegen_fn_attrs(trait_item)
3285             .flags
3286             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3287     }
3288
3289     false
3290 }
3291
3292 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3293     use rustc_ast::{Lit, LitIntType, LitKind};
3294     let meta_item_list = attr.meta_item_list();
3295     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3296     let sole_meta_list = match meta_item_list {
3297         Some([item]) => item.literal(),
3298         Some(_) => {
3299             tcx.sess
3300                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3301                 .note("the attribute requires exactly one argument")
3302                 .emit();
3303             return None;
3304         }
3305         _ => None,
3306     };
3307     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3308         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3309         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3310         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3311         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3312         //
3313         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3314         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3315         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3316         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3317         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3318         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3319         // about LINK.EXE failing.)
3320         if *ordinal <= u16::MAX as u128 {
3321             Some(*ordinal as u16)
3322         } else {
3323             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3324             tcx.sess
3325                 .struct_span_err(attr.span, &msg)
3326                 .note("the value may not exceed `u16::MAX`")
3327                 .emit();
3328             None
3329         }
3330     } else {
3331         tcx.sess
3332             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3333             .note("an unsuffixed integer value, e.g., `1`, is expected")
3334             .emit();
3335         None
3336     }
3337 }
3338
3339 fn check_link_name_xor_ordinal(
3340     tcx: TyCtxt<'_>,
3341     codegen_fn_attrs: &CodegenFnAttrs,
3342     inline_span: Option<Span>,
3343 ) {
3344     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3345         return;
3346     }
3347     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3348     if let Some(span) = inline_span {
3349         tcx.sess.span_err(span, msg);
3350     } else {
3351         tcx.sess.err(msg);
3352     }
3353 }
3354
3355 /// Checks the function annotated with `#[target_feature]` is not a safe
3356 /// trait method implementation, reporting an error if it is.
3357 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3358     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3359     let node = tcx.hir().get(hir_id);
3360     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3361         let parent_id = tcx.hir().get_parent_item(hir_id);
3362         let parent_item = tcx.hir().expect_item(parent_id);
3363         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3364             tcx.sess
3365                 .struct_span_err(
3366                     attr_span,
3367                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3368                 )
3369                 .span_label(attr_span, "cannot be applied to safe trait method")
3370                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3371                 .emit();
3372         }
3373     }
3374 }