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};
  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     placeholder_type_error_diag(
 164         tcx,
 165         span,
 166         generics,
 167         placeholder_types,
 168         vec![],
 169         suggest,
 170         hir_ty,
 171         kind,
 172     )
 173     .emit();
 174 }
 175
 176 crate fn placeholder_type_error_diag<'tcx>(
 177     tcx: TyCtxt<'tcx>,
 178     span: Option<Span>,
 179     generics: &[hir::GenericParam<'_>],
 180     placeholder_types: Vec<Span>,
 181     additional_spans: Vec<Span>,
 182     suggest: bool,
 183     hir_ty: Option<&hir::Ty<'_>>,
 184     kind: &'static str,
 185 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 186     if placeholder_types.is_empty() {
 187         return bad_placeholder(tcx, additional_spans, kind);
 188     }
 189
 190     let type_name = generics.next_type_param_name(None);
 191     let mut sugg: Vec<_> =
 192         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 193
 194     if generics.is_empty() {
 195         if let Some(span) = span {
 196             sugg.push((span, format!("<{}>", type_name)));
 197         }
 198     } else if let Some(arg) = generics
 199         .iter()
 200         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 201     {
 202         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 203         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 204         sugg.push((arg.span, (*type_name).to_string()));
 205     } else {
 206         let last = generics.iter().last().unwrap();
 207         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 208         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 209         sugg.push((span, format!(", {}", type_name)));
 210     }
 211
 212     let mut err =
 213         bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
 214
 215     // Suggest, but only if it is not a function in const or static
 216     if suggest {
 217         let mut is_fn = false;
 218         let mut is_const_or_static = false;
 219
 220         if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
 221             is_fn = true;
 222
 223             // Check if parent is const or static
 224             let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 225             let parent_node = tcx.hir().get(parent_id);
 226
 227             is_const_or_static = matches!(
 228                 parent_node,
 229                 Node::Item(&hir::Item {
 230                     kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 231                     ..
 232                 }) | Node::TraitItem(&hir::TraitItem {
 233                     kind: hir::TraitItemKind::Const(..),
 234                     ..
 235                 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 236             );
 237         }
 238
 239         // if function is wrapped around a const or static,
 240         // then don't show the suggestion
 241         if !(is_fn && is_const_or_static) {
 242             err.multipart_suggestion(
 243                 "use type parameters instead",
 244                 sugg,
 245                 Applicability::HasPlaceholders,
 246             );
 247         }
 248     }
 249
 250     err
 251 }
 252
 253 fn reject_placeholder_type_signatures_in_item<'tcx>(
 254     tcx: TyCtxt<'tcx>,
 255     item: &'tcx hir::Item<'tcx>,
 256 ) {
 257     let (generics, suggest) = match &item.kind {
 258         hir::ItemKind::Union(_, generics)
 259         | hir::ItemKind::Enum(_, generics)
 260         | hir::ItemKind::TraitAlias(generics, _)
 261         | hir::ItemKind::Trait(_, _, generics, ..)
 262         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 263         | hir::ItemKind::Struct(_, generics) => (generics, true),
 264         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 265         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 266         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 267         _ => return,
 268     };
 269
 270     let mut visitor = HirPlaceholderCollector::default();
 271     visitor.visit_item(item);
 272
 273     placeholder_type_error(
 274         tcx,
 275         Some(generics.span),
 276         generics.params,
 277         visitor.0,
 278         suggest,
 279         None,
 280         item.kind.descr(),
 281     );
 282 }
 283
 284 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 285     type NestedFilter = nested_filter::OnlyBodies;
 286
 287     fn nested_visit_map(&mut self) -> Self::Map {
 288         self.tcx.hir()
 289     }
 290
 291     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 292         convert_item(self.tcx, item.item_id());
 293         reject_placeholder_type_signatures_in_item(self.tcx, item);
 294         intravisit::walk_item(self, item);
 295     }
 296
 297     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 298         for param in generics.params {
 299             match param.kind {
 300                 hir::GenericParamKind::Lifetime { .. } => {}
 301                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 302                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 303                     self.tcx.ensure().type_of(def_id);
 304                 }
 305                 hir::GenericParamKind::Type { .. } => {}
 306                 hir::GenericParamKind::Const { default, .. } => {
 307                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 308                     self.tcx.ensure().type_of(def_id);
 309                     if let Some(default) = default {
 310                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 311                         // need to store default and type of default
 312                         self.tcx.ensure().type_of(default_def_id);
 313                         self.tcx.ensure().const_param_default(def_id);
 314                     }
 315                 }
 316             }
 317         }
 318         intravisit::walk_generics(self, generics);
 319     }
 320
 321     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 322         if let hir::ExprKind::Closure(..) = expr.kind {
 323             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 324             self.tcx.ensure().generics_of(def_id);
 325             // We do not call `type_of` for closures here as that
 326             // depends on typecheck and would therefore hide
 327             // any further errors in case one typeck fails.
 328         }
 329         intravisit::walk_expr(self, expr);
 330     }
 331
 332     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 333         convert_trait_item(self.tcx, trait_item.trait_item_id());
 334         intravisit::walk_trait_item(self, trait_item);
 335     }
 336
 337     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 338         convert_impl_item(self.tcx, impl_item.impl_item_id());
 339         intravisit::walk_impl_item(self, impl_item);
 340     }
 341 }
 342
 343 ///////////////////////////////////////////////////////////////////////////
 344 // Utility types and common code for the above passes.
 345
 346 fn bad_placeholder<'tcx>(
 347     tcx: TyCtxt<'tcx>,
 348     mut spans: Vec<Span>,
 349     kind: &'static str,
 350 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 351     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 352
 353     spans.sort();
 354     let mut err = struct_span_err!(
 355         tcx.sess,
 356         spans.clone(),
 357         E0121,
 358         "the placeholder `_` is not allowed within types on item signatures for {}",
 359         kind
 360     );
 361     for span in spans {
 362         err.span_label(span, "not allowed in type signatures");
 363     }
 364     err
 365 }
 366
 367 impl<'tcx> ItemCtxt<'tcx> {
 368     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 369         ItemCtxt { tcx, item_def_id }
 370     }
 371
 372     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 373         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 374     }
 375
 376     pub fn hir_id(&self) -> hir::HirId {
 377         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 378     }
 379
 380     pub fn node(&self) -> hir::Node<'tcx> {
 381         self.tcx.hir().get(self.hir_id())
 382     }
 383 }
 384
 385 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 386     fn tcx(&self) -> TyCtxt<'tcx> {
 387         self.tcx
 388     }
 389
 390     fn item_def_id(&self) -> Option<DefId> {
 391         Some(self.item_def_id)
 392     }
 393
 394     fn get_type_parameter_bounds(
 395         &self,
 396         span: Span,
 397         def_id: DefId,
 398         assoc_name: Ident,
 399     ) -> ty::GenericPredicates<'tcx> {
 400         self.tcx.at(span).type_param_predicates((
 401             self.item_def_id,
 402             def_id.expect_local(),
 403             assoc_name,
 404         ))
 405     }
 406
 407     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 408         None
 409     }
 410
 411     fn allow_ty_infer(&self) -> bool {
 412         false
 413     }
 414
 415     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 416         self.tcx().ty_error_with_message(span, "bad placeholder type")
 417     }
 418
 419     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 420         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
 421             ty::ReErased => self.tcx.lifetimes.re_static,
 422             _ => r,
 423         });
 424         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 425     }
 426
 427     fn projected_ty_from_poly_trait_ref(
 428         &self,
 429         span: Span,
 430         item_def_id: DefId,
 431         item_segment: &hir::PathSegment<'_>,
 432         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 433     ) -> Ty<'tcx> {
 434         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 435             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 436                 self,
 437                 self.tcx,
 438                 span,
 439                 item_def_id,
 440                 item_segment,
 441                 trait_ref.substs,
 442             );
 443             self.tcx().mk_projection(item_def_id, item_substs)
 444         } else {
 445             // There are no late-bound regions; we can just ignore the binder.
 446             let mut err = struct_span_err!(
 447                 self.tcx().sess,
 448                 span,
 449                 E0212,
 450                 "cannot use the associated type of a trait \
 451                  with uninferred generic parameters"
 452             );
 453
 454             match self.node() {
 455                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 456                     let item =
 457                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 458                     match &item.kind {
 459                         hir::ItemKind::Enum(_, generics)
 460                         | hir::ItemKind::Struct(_, generics)
 461                         | hir::ItemKind::Union(_, generics) => {
 462                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 463                             let (lt_sp, sugg) = match generics.params {
 464                                 [] => (generics.span, format!("<{}>", lt_name)),
 465                                 [bound, ..] => {
 466                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 467                                 }
 468                             };
 469                             let suggestions = vec![
 470                                 (lt_sp, sugg),
 471                                 (
 472                                     span.with_hi(item_segment.ident.span.lo()),
 473                                     format!(
 474                                         "{}::",
 475                                         // Replace the existing lifetimes with a new named lifetime.
 476                                         self.tcx
 477                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 478                                                 self.tcx.mk_region(ty::ReEarlyBound(
 479                                                     ty::EarlyBoundRegion {
 480                                                         def_id: item_def_id,
 481                                                         index: 0,
 482                                                         name: Symbol::intern(&lt_name),
 483                                                     },
 484                                                 ))
 485                                             })
 486                                             .0,
 487                                     ),
 488                                 ),
 489                             ];
 490                             err.multipart_suggestion(
 491                                 "use a fully qualified path with explicit lifetimes",
 492                                 suggestions,
 493                                 Applicability::MaybeIncorrect,
 494                             );
 495                         }
 496                         _ => {}
 497                     }
 498                 }
 499                 hir::Node::Item(hir::Item {
 500                     kind:
 501                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 502                     ..
 503                 }) => {}
 504                 hir::Node::Item(_)
 505                 | hir::Node::ForeignItem(_)
 506                 | hir::Node::TraitItem(_)
 507                 | hir::Node::ImplItem(_) => {
 508                     err.span_suggestion_verbose(
 509                         span.with_hi(item_segment.ident.span.lo()),
 510                         "use a fully qualified path with inferred lifetimes",
 511                         format!(
 512                             "{}::",
 513                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 514                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 515                         ),
 516                         Applicability::MaybeIncorrect,
 517                     );
 518                 }
 519                 _ => {}
 520             }
 521             err.emit();
 522             self.tcx().ty_error()
 523         }
 524     }
 525
 526     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 527         // Types in item signatures are not normalized to avoid undue dependencies.
 528         ty
 529     }
 530
 531     fn set_tainted_by_errors(&self) {
 532         // There's no obvious place to track this, so just let it go.
 533     }
 534
 535     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 536         // There's no place to record types from signatures?
 537     }
 538 }
 539
 540 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 541 fn get_new_lifetime_name<'tcx>(
 542     tcx: TyCtxt<'tcx>,
 543     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 544     generics: &hir::Generics<'tcx>,
 545 ) -> String {
 546     let existing_lifetimes = tcx
 547         .collect_referenced_late_bound_regions(&poly_trait_ref)
 548         .into_iter()
 549         .filter_map(|lt| {
 550             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 551                 Some(name.as_str().to_string())
 552             } else {
 553                 None
 554             }
 555         })
 556         .chain(generics.params.iter().filter_map(|param| {
 557             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 558                 Some(param.name.ident().as_str().to_string())
 559             } else {
 560                 None
 561             }
 562         }))
 563         .collect::<FxHashSet<String>>();
 564
 565     let a_to_z_repeat_n = |n| {
 566         (b'a'..=b'z').map(move |c| {
 567             let mut s = '\''.to_string();
 568             s.extend(std::iter::repeat(char::from(c)).take(n));
 569             s
 570         })
 571     };
 572
 573     // If all single char lifetime names are present, we wrap around and double the chars.
 574     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 575 }
 576
 577 /// Returns the predicates defined on `item_def_id` of the form
 578 /// `X: Foo` where `X` is the type parameter `def_id`.
 579 fn type_param_predicates(
 580     tcx: TyCtxt<'_>,
 581     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 582 ) -> ty::GenericPredicates<'_> {
 583     use rustc_hir::*;
 584
 585     // In the AST, bounds can derive from two places. Either
 586     // written inline like `<T: Foo>` or in a where-clause like
 587     // `where T: Foo`.
 588
 589     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 590     let param_owner = tcx.hir().ty_param_owner(def_id);
 591     let generics = tcx.generics_of(param_owner);
 592     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 593     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 594
 595     // Don't look for bounds where the type parameter isn't in scope.
 596     let parent = if item_def_id == param_owner.to_def_id() {
 597         None
 598     } else {
 599         tcx.generics_of(item_def_id).parent
 600     };
 601
 602     let mut result = parent
 603         .map(|parent| {
 604             let icx = ItemCtxt::new(tcx, parent);
 605             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 606         })
 607         .unwrap_or_default();
 608     let mut extend = None;
 609
 610     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 611     let ast_generics = match tcx.hir().get(item_hir_id) {
 612         Node::TraitItem(item) => &item.generics,
 613
 614         Node::ImplItem(item) => &item.generics,
 615
 616         Node::Item(item) => {
 617             match item.kind {
 618                 ItemKind::Fn(.., ref generics, _)
 619                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 620                 | ItemKind::TyAlias(_, ref generics)
 621                 | ItemKind::OpaqueTy(OpaqueTy {
 622                     ref generics,
 623                     origin: hir::OpaqueTyOrigin::TyAlias,
 624                     ..
 625                 })
 626                 | ItemKind::Enum(_, ref generics)
 627                 | ItemKind::Struct(_, ref generics)
 628                 | ItemKind::Union(_, ref generics) => generics,
 629                 ItemKind::Trait(_, _, ref generics, ..) => {
 630                     // Implied `Self: Trait` and supertrait bounds.
 631                     if param_id == item_hir_id {
 632                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 633                         extend =
 634                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 635                     }
 636                     generics
 637                 }
 638                 _ => return result,
 639             }
 640         }
 641
 642         Node::ForeignItem(item) => match item.kind {
 643             ForeignItemKind::Fn(_, _, ref generics) => generics,
 644             _ => return result,
 645         },
 646
 647         _ => return result,
 648     };
 649
 650     let icx = ItemCtxt::new(tcx, item_def_id);
 651     let extra_predicates = extend.into_iter().chain(
 652         icx.type_parameter_bounds_in_generics(
 653             ast_generics,
 654             param_id,
 655             ty,
 656             OnlySelfBounds(true),
 657             Some(assoc_name),
 658         )
 659         .into_iter()
 660         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 661             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 662             _ => false,
 663         }),
 664     );
 665     result.predicates =
 666         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 667     result
 668 }
 669
 670 impl<'tcx> ItemCtxt<'tcx> {
 671     /// Finds bounds from `hir::Generics`. This requires scanning through the
 672     /// AST. We do this to avoid having to convert *all* the bounds, which
 673     /// would create artificial cycles. Instead, we can only convert the
 674     /// bounds for a type parameter `X` if `X::Foo` is used.
 675     fn type_parameter_bounds_in_generics(
 676         &self,
 677         ast_generics: &'tcx hir::Generics<'tcx>,
 678         param_id: hir::HirId,
 679         ty: Ty<'tcx>,
 680         only_self_bounds: OnlySelfBounds,
 681         assoc_name: Option<Ident>,
 682     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 683         let from_ty_params = ast_generics
 684             .params
 685             .iter()
 686             .filter_map(|param| match param.kind {
 687                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 688                     if param.hir_id == param_id =>
 689                 {
 690                     Some(&param.bounds)
 691                 }
 692                 _ => None,
 693             })
 694             .flat_map(|bounds| bounds.iter())
 695             .filter(|b| match assoc_name {
 696                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 697                 None => true,
 698             })
 699             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 700
 701         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 702         let from_where_clauses = ast_generics
 703             .where_clause
 704             .predicates
 705             .iter()
 706             .filter_map(|wp| match *wp {
 707                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 708                 _ => None,
 709             })
 710             .flat_map(|bp| {
 711                 let bt = if bp.is_param_bound(param_def_id) {
 712                     Some(ty)
 713                 } else if !only_self_bounds.0 {
 714                     Some(self.to_ty(bp.bounded_ty))
 715                 } else {
 716                     None
 717                 };
 718                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 719
 720                 bp.bounds
 721                     .iter()
 722                     .filter(|b| match assoc_name {
 723                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 724                         None => true,
 725                     })
 726                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 727             })
 728             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 729
 730         from_ty_params.chain(from_where_clauses).collect()
 731     }
 732
 733     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 734         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 735
 736         match b {
 737             hir::GenericBound::Trait(poly_trait_ref, _) => {
 738                 let trait_ref = &poly_trait_ref.trait_ref;
 739                 if let Some(trait_did) = trait_ref.trait_def_id() {
 740                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 741                 } else {
 742                     false
 743                 }
 744             }
 745             _ => false,
 746         }
 747     }
 748 }
 749
 750 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 751     let it = tcx.hir().item(item_id);
 752     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 753     let def_id = item_id.def_id;
 754
 755     match it.kind {
 756         // These don't define types.
 757         hir::ItemKind::ExternCrate(_)
 758         | hir::ItemKind::Use(..)
 759         | hir::ItemKind::Macro(..)
 760         | hir::ItemKind::Mod(_)
 761         | hir::ItemKind::GlobalAsm(_) => {}
 762         hir::ItemKind::ForeignMod { items, .. } => {
 763             for item in items {
 764                 let item = tcx.hir().foreign_item(item.id);
 765                 tcx.ensure().generics_of(item.def_id);
 766                 tcx.ensure().type_of(item.def_id);
 767                 tcx.ensure().predicates_of(item.def_id);
 768                 match item.kind {
 769                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 770                     hir::ForeignItemKind::Static(..) => {
 771                         let mut visitor = HirPlaceholderCollector::default();
 772                         visitor.visit_foreign_item(item);
 773                         placeholder_type_error(
 774                             tcx,
 775                             None,
 776                             &[],
 777                             visitor.0,
 778                             false,
 779                             None,
 780                             "static variable",
 781                         );
 782                     }
 783                     _ => (),
 784                 }
 785             }
 786         }
 787         hir::ItemKind::Enum(ref enum_definition, _) => {
 788             tcx.ensure().generics_of(def_id);
 789             tcx.ensure().type_of(def_id);
 790             tcx.ensure().predicates_of(def_id);
 791             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 792         }
 793         hir::ItemKind::Impl { .. } => {
 794             tcx.ensure().generics_of(def_id);
 795             tcx.ensure().type_of(def_id);
 796             tcx.ensure().impl_trait_ref(def_id);
 797             tcx.ensure().predicates_of(def_id);
 798         }
 799         hir::ItemKind::Trait(..) => {
 800             tcx.ensure().generics_of(def_id);
 801             tcx.ensure().trait_def(def_id);
 802             tcx.at(it.span).super_predicates_of(def_id);
 803             tcx.ensure().predicates_of(def_id);
 804         }
 805         hir::ItemKind::TraitAlias(..) => {
 806             tcx.ensure().generics_of(def_id);
 807             tcx.at(it.span).super_predicates_of(def_id);
 808             tcx.ensure().predicates_of(def_id);
 809         }
 810         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 811             tcx.ensure().generics_of(def_id);
 812             tcx.ensure().type_of(def_id);
 813             tcx.ensure().predicates_of(def_id);
 814
 815             for f in struct_def.fields() {
 816                 let def_id = tcx.hir().local_def_id(f.hir_id);
 817                 tcx.ensure().generics_of(def_id);
 818                 tcx.ensure().type_of(def_id);
 819                 tcx.ensure().predicates_of(def_id);
 820             }
 821
 822             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 823                 convert_variant_ctor(tcx, ctor_hir_id);
 824             }
 825         }
 826
 827         // Desugared from `impl Trait`, so visited by the function's return type.
 828         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 829             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 830             ..
 831         }) => {}
 832
 833         // Don't call `type_of` on opaque types, since that depends on type
 834         // checking function bodies. `check_item_type` ensures that it's called
 835         // instead.
 836         hir::ItemKind::OpaqueTy(..) => {
 837             tcx.ensure().generics_of(def_id);
 838             tcx.ensure().predicates_of(def_id);
 839             tcx.ensure().explicit_item_bounds(def_id);
 840         }
 841         hir::ItemKind::TyAlias(..)
 842         | hir::ItemKind::Static(..)
 843         | hir::ItemKind::Const(..)
 844         | hir::ItemKind::Fn(..) => {
 845             tcx.ensure().generics_of(def_id);
 846             tcx.ensure().type_of(def_id);
 847             tcx.ensure().predicates_of(def_id);
 848             match it.kind {
 849                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 850                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 851                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 852                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 853                     if let hir::TyKind::TraitObject(..) = ty.kind {
 854                         let mut visitor = HirPlaceholderCollector::default();
 855                         visitor.visit_item(it);
 856                         placeholder_type_error(
 857                             tcx,
 858                             None,
 859                             &[],
 860                             visitor.0,
 861                             false,
 862                             None,
 863                             it.kind.descr(),
 864                         );
 865                     }
 866                 }
 867                 _ => (),
 868             }
 869         }
 870     }
 871 }
 872
 873 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 874     let trait_item = tcx.hir().trait_item(trait_item_id);
 875     tcx.ensure().generics_of(trait_item_id.def_id);
 876
 877     match trait_item.kind {
 878         hir::TraitItemKind::Fn(..) => {
 879             tcx.ensure().type_of(trait_item_id.def_id);
 880             tcx.ensure().fn_sig(trait_item_id.def_id);
 881         }
 882
 883         hir::TraitItemKind::Const(.., Some(_)) => {
 884             tcx.ensure().type_of(trait_item_id.def_id);
 885         }
 886
 887         hir::TraitItemKind::Const(..) => {
 888             tcx.ensure().type_of(trait_item_id.def_id);
 889             // Account for `const C: _;`.
 890             let mut visitor = HirPlaceholderCollector::default();
 891             visitor.visit_trait_item(trait_item);
 892             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 893         }
 894
 895         hir::TraitItemKind::Type(_, Some(_)) => {
 896             tcx.ensure().item_bounds(trait_item_id.def_id);
 897             tcx.ensure().type_of(trait_item_id.def_id);
 898             // Account for `type T = _;`.
 899             let mut visitor = HirPlaceholderCollector::default();
 900             visitor.visit_trait_item(trait_item);
 901             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 902         }
 903
 904         hir::TraitItemKind::Type(_, None) => {
 905             tcx.ensure().item_bounds(trait_item_id.def_id);
 906             // #74612: Visit and try to find bad placeholders
 907             // even if there is no concrete type.
 908             let mut visitor = HirPlaceholderCollector::default();
 909             visitor.visit_trait_item(trait_item);
 910
 911             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 912         }
 913     };
 914
 915     tcx.ensure().predicates_of(trait_item_id.def_id);
 916 }
 917
 918 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 919     let def_id = impl_item_id.def_id;
 920     tcx.ensure().generics_of(def_id);
 921     tcx.ensure().type_of(def_id);
 922     tcx.ensure().predicates_of(def_id);
 923     let impl_item = tcx.hir().impl_item(impl_item_id);
 924     match impl_item.kind {
 925         hir::ImplItemKind::Fn(..) => {
 926             tcx.ensure().fn_sig(def_id);
 927         }
 928         hir::ImplItemKind::TyAlias(_) => {
 929             // Account for `type T = _;`
 930             let mut visitor = HirPlaceholderCollector::default();
 931             visitor.visit_impl_item(impl_item);
 932
 933             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 934         }
 935         hir::ImplItemKind::Const(..) => {}
 936     }
 937 }
 938
 939 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 940     let def_id = tcx.hir().local_def_id(ctor_id);
 941     tcx.ensure().generics_of(def_id);
 942     tcx.ensure().type_of(def_id);
 943     tcx.ensure().predicates_of(def_id);
 944 }
 945
 946 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 947     let def = tcx.adt_def(def_id);
 948     let repr_type = def.repr().discr_type();
 949     let initial = repr_type.initial_discriminant(tcx);
 950     let mut prev_discr = None::<Discr<'_>>;
 951
 952     // fill the discriminant values and field types
 953     for variant in variants {
 954         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 955         prev_discr = Some(
 956             if let Some(ref e) = variant.disr_expr {
 957                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 958                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 959             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 960                 Some(discr)
 961             } else {
 962                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 963                     .span_label(
 964                         variant.span,
 965                         format!("overflowed on value after {}", prev_discr.unwrap()),
 966                     )
 967                     .note(&format!(
 968                         "explicitly set `{} = {}` if that is desired outcome",
 969                         variant.ident, wrapped_discr
 970                     ))
 971                     .emit();
 972                 None
 973             }
 974             .unwrap_or(wrapped_discr),
 975         );
 976
 977         for f in variant.data.fields() {
 978             let def_id = tcx.hir().local_def_id(f.hir_id);
 979             tcx.ensure().generics_of(def_id);
 980             tcx.ensure().type_of(def_id);
 981             tcx.ensure().predicates_of(def_id);
 982         }
 983
 984         // Convert the ctor, if any. This also registers the variant as
 985         // an item.
 986         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 987             convert_variant_ctor(tcx, ctor_hir_id);
 988         }
 989     }
 990 }
 991
 992 fn convert_variant(
 993     tcx: TyCtxt<'_>,
 994     variant_did: Option<LocalDefId>,
 995     ctor_did: Option<LocalDefId>,
 996     ident: Ident,
 997     discr: ty::VariantDiscr,
 998     def: &hir::VariantData<'_>,
 999     adt_kind: ty::AdtKind,
1000     parent_did: LocalDefId,
1001 ) -> ty::VariantDef {
1002     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
1003     let fields = def
1004         .fields()
1005         .iter()
1006         .map(|f| {
1007             let fid = tcx.hir().local_def_id(f.hir_id);
1008             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
1009             if let Some(prev_span) = dup_span {
1010                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
1011                     field_name: f.ident,
1012                     span: f.span,
1013                     prev_span,
1014                 });
1015             } else {
1016                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
1017             }
1018
1019             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
1020         })
1021         .collect();
1022     let recovered = match def {
1023         hir::VariantData::Struct(_, r) => *r,
1024         _ => false,
1025     };
1026     ty::VariantDef::new(
1027         ident.name,
1028         variant_did.map(LocalDefId::to_def_id),
1029         ctor_did.map(LocalDefId::to_def_id),
1030         discr,
1031         fields,
1032         CtorKind::from_hir(def),
1033         adt_kind,
1034         parent_did.to_def_id(),
1035         recovered,
1036         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1037             || variant_did.map_or(false, |variant_did| {
1038                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1039             }),
1040     )
1041 }
1042
1043 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
1044     use rustc_hir::*;
1045
1046     let def_id = def_id.expect_local();
1047     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1048     let Node::Item(item) = tcx.hir().get(hir_id) else {
1049         bug!();
1050     };
1051
1052     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1053     let (kind, variants) = match item.kind {
1054         ItemKind::Enum(ref def, _) => {
1055             let mut distance_from_explicit = 0;
1056             let variants = def
1057                 .variants
1058                 .iter()
1059                 .map(|v| {
1060                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1061                     let ctor_did =
1062                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1063
1064                     let discr = if let Some(ref e) = v.disr_expr {
1065                         distance_from_explicit = 0;
1066                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1067                     } else {
1068                         ty::VariantDiscr::Relative(distance_from_explicit)
1069                     };
1070                     distance_from_explicit += 1;
1071
1072                     convert_variant(
1073                         tcx,
1074                         variant_did,
1075                         ctor_did,
1076                         v.ident,
1077                         discr,
1078                         &v.data,
1079                         AdtKind::Enum,
1080                         def_id,
1081                     )
1082                 })
1083                 .collect();
1084
1085             (AdtKind::Enum, variants)
1086         }
1087         ItemKind::Struct(ref def, _) => {
1088             let variant_did = None::<LocalDefId>;
1089             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1090
1091             let variants = std::iter::once(convert_variant(
1092                 tcx,
1093                 variant_did,
1094                 ctor_did,
1095                 item.ident,
1096                 ty::VariantDiscr::Relative(0),
1097                 def,
1098                 AdtKind::Struct,
1099                 def_id,
1100             ))
1101             .collect();
1102
1103             (AdtKind::Struct, variants)
1104         }
1105         ItemKind::Union(ref def, _) => {
1106             let variant_did = None;
1107             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1108
1109             let variants = std::iter::once(convert_variant(
1110                 tcx,
1111                 variant_did,
1112                 ctor_did,
1113                 item.ident,
1114                 ty::VariantDiscr::Relative(0),
1115                 def,
1116                 AdtKind::Union,
1117                 def_id,
1118             ))
1119             .collect();
1120
1121             (AdtKind::Union, variants)
1122         }
1123         _ => bug!(),
1124     };
1125     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1126 }
1127
1128 /// Ensures that the super-predicates of the trait with a `DefId`
1129 /// of `trait_def_id` are converted and stored. This also ensures that
1130 /// the transitive super-predicates are converted.
1131 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1132     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1133     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1134 }
1135
1136 /// Ensures that the super-predicates of the trait with a `DefId`
1137 /// of `trait_def_id` are converted and stored. This also ensures that
1138 /// the transitive super-predicates are converted.
1139 fn super_predicates_that_define_assoc_type(
1140     tcx: TyCtxt<'_>,
1141     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1142 ) -> ty::GenericPredicates<'_> {
1143     debug!(
1144         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1145         trait_def_id, assoc_name
1146     );
1147     if trait_def_id.is_local() {
1148         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1149         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1150
1151         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1152             bug!("trait_node_id {} is not an item", trait_hir_id);
1153         };
1154
1155         let (generics, bounds) = match item.kind {
1156             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1157             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1158             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1159         };
1160
1161         let icx = ItemCtxt::new(tcx, trait_def_id);
1162
1163         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1164         let self_param_ty = tcx.types.self_param;
1165         let superbounds1 = if let Some(assoc_name) = assoc_name {
1166             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1167                 &icx,
1168                 self_param_ty,
1169                 bounds,
1170                 assoc_name,
1171             )
1172         } else {
1173             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1174         };
1175
1176         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1177
1178         // Convert any explicit superbounds in the where-clause,
1179         // e.g., `trait Foo where Self: Bar`.
1180         // In the case of trait aliases, however, we include all bounds in the where-clause,
1181         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1182         // as one of its "superpredicates".
1183         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1184         let superbounds2 = icx.type_parameter_bounds_in_generics(
1185             generics,
1186             item.hir_id(),
1187             self_param_ty,
1188             OnlySelfBounds(!is_trait_alias),
1189             assoc_name,
1190         );
1191
1192         // Combine the two lists to form the complete set of superbounds:
1193         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1194
1195         // Now require that immediate supertraits are converted,
1196         // which will, in turn, reach indirect supertraits.
1197         if assoc_name.is_none() {
1198             // Now require that immediate supertraits are converted,
1199             // which will, in turn, reach indirect supertraits.
1200             for &(pred, span) in superbounds {
1201                 debug!("superbound: {:?}", pred);
1202                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1203                     tcx.at(span).super_predicates_of(bound.def_id());
1204                 }
1205             }
1206         }
1207
1208         ty::GenericPredicates { parent: None, predicates: superbounds }
1209     } else {
1210         // if `assoc_name` is None, then the query should've been redirected to an
1211         // external provider
1212         assert!(assoc_name.is_some());
1213         tcx.super_predicates_of(trait_def_id)
1214     }
1215 }
1216
1217 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1218     let item = tcx.hir().expect_item(def_id.expect_local());
1219
1220     let (is_auto, unsafety, items) = match item.kind {
1221         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1222             (is_auto == hir::IsAuto::Yes, unsafety, items)
1223         }
1224         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1225         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1226     };
1227
1228     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1229     if paren_sugar && !tcx.features().unboxed_closures {
1230         tcx.sess
1231             .struct_span_err(
1232                 item.span,
1233                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1234                  which traits can use parenthetical notation",
1235             )
1236             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1237             .emit();
1238     }
1239
1240     let is_marker = tcx.has_attr(def_id, sym::marker);
1241     let skip_array_during_method_dispatch =
1242         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1243     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1244         ty::trait_def::TraitSpecializationKind::Marker
1245     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1246         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1247     } else {
1248         ty::trait_def::TraitSpecializationKind::None
1249     };
1250     let must_implement_one_of = tcx
1251         .get_attrs(def_id)
1252         .iter()
1253         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1254         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1255         // and that they are all identifiers
1256         .and_then(|attr| match attr.meta_item_list() {
1257             Some(items) if items.len() < 2 => {
1258                 tcx.sess
1259                     .struct_span_err(
1260                         attr.span,
1261                         "the `#[rustc_must_implement_one_of]` attribute must be \
1262                         used with at least 2 args",
1263                     )
1264                     .emit();
1265
1266                 None
1267             }
1268             Some(items) => items
1269                 .into_iter()
1270                 .map(|item| item.ident().ok_or(item.span()))
1271                 .collect::<Result<Box<[_]>, _>>()
1272                 .map_err(|span| {
1273                     tcx.sess
1274                         .struct_span_err(span, "must be a name of an associated function")
1275                         .emit();
1276                 })
1277                 .ok()
1278                 .zip(Some(attr.span)),
1279             // Error is reported by `rustc_attr!`
1280             None => None,
1281         })
1282         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1283         // functions in the trait with default implementations
1284         .and_then(|(list, attr_span)| {
1285             let errors = list.iter().filter_map(|ident| {
1286                 let item = items.iter().find(|item| item.ident == *ident);
1287
1288                 match item {
1289                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1290                         if !item.defaultness.has_value() {
1291                             tcx.sess
1292                                 .struct_span_err(
1293                                     item.span,
1294                                     "This function doesn't have a default implementation",
1295                                 )
1296                                 .span_note(attr_span, "required by this annotation")
1297                                 .emit();
1298
1299                             return Some(());
1300                         }
1301
1302                         return None;
1303                     }
1304                     Some(item) => {
1305                         tcx.sess
1306                             .struct_span_err(item.span, "Not a function")
1307                             .span_note(attr_span, "required by this annotation")
1308                             .note(
1309                                 "All `#[rustc_must_implement_one_of]` arguments \
1310                             must be associated function names",
1311                             )
1312                             .emit();
1313                     }
1314                     None => {
1315                         tcx.sess
1316                             .struct_span_err(ident.span, "Function not found in this trait")
1317                             .emit();
1318                     }
1319                 }
1320
1321                 Some(())
1322             });
1323
1324             (errors.count() == 0).then_some(list)
1325         })
1326         // Check for duplicates
1327         .and_then(|list| {
1328             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1329             let mut no_dups = true;
1330
1331             for ident in &*list {
1332                 if let Some(dup) = set.insert(ident.name, ident.span) {
1333                     tcx.sess
1334                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1335                         .note(
1336                             "All `#[rustc_must_implement_one_of]` arguments \
1337                             must be unique",
1338                         )
1339                         .emit();
1340
1341                     no_dups = false;
1342                 }
1343             }
1344
1345             no_dups.then_some(list)
1346         });
1347
1348     ty::TraitDef::new(
1349         def_id,
1350         unsafety,
1351         paren_sugar,
1352         is_auto,
1353         is_marker,
1354         skip_array_during_method_dispatch,
1355         spec_kind,
1356         must_implement_one_of,
1357     )
1358 }
1359
1360 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1361     struct LateBoundRegionsDetector<'tcx> {
1362         tcx: TyCtxt<'tcx>,
1363         outer_index: ty::DebruijnIndex,
1364         has_late_bound_regions: Option<Span>,
1365     }
1366
1367     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1368         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1369             if self.has_late_bound_regions.is_some() {
1370                 return;
1371             }
1372             match ty.kind {
1373                 hir::TyKind::BareFn(..) => {
1374                     self.outer_index.shift_in(1);
1375                     intravisit::walk_ty(self, ty);
1376                     self.outer_index.shift_out(1);
1377                 }
1378                 _ => intravisit::walk_ty(self, ty),
1379             }
1380         }
1381
1382         fn visit_poly_trait_ref(
1383             &mut self,
1384             tr: &'tcx hir::PolyTraitRef<'tcx>,
1385             m: hir::TraitBoundModifier,
1386         ) {
1387             if self.has_late_bound_regions.is_some() {
1388                 return;
1389             }
1390             self.outer_index.shift_in(1);
1391             intravisit::walk_poly_trait_ref(self, tr, m);
1392             self.outer_index.shift_out(1);
1393         }
1394
1395         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1396             if self.has_late_bound_regions.is_some() {
1397                 return;
1398             }
1399
1400             match self.tcx.named_region(lt.hir_id) {
1401                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1402                 Some(
1403                     rl::Region::LateBound(debruijn, _, _)
1404                     | rl::Region::LateBoundAnon(debruijn, _, _),
1405                 ) if debruijn < self.outer_index => {}
1406                 Some(
1407                     rl::Region::LateBound(..)
1408                     | rl::Region::LateBoundAnon(..)
1409                     | rl::Region::Free(..),
1410                 )
1411                 | None => {
1412                     self.has_late_bound_regions = Some(lt.span);
1413                 }
1414             }
1415         }
1416     }
1417
1418     fn has_late_bound_regions<'tcx>(
1419         tcx: TyCtxt<'tcx>,
1420         def_id: LocalDefId,
1421         generics: &'tcx hir::Generics<'tcx>,
1422         decl: &'tcx hir::FnDecl<'tcx>,
1423     ) -> Option<Span> {
1424         let mut visitor = LateBoundRegionsDetector {
1425             tcx,
1426             outer_index: ty::INNERMOST,
1427             has_late_bound_regions: None,
1428         };
1429         let late_bound_map = tcx.is_late_bound_map(def_id);
1430         let is_late_bound = |id| {
1431             let id = tcx.hir().local_def_id(id);
1432             late_bound_map.map_or(false, |(_, set)| set.contains(&id))
1433         };
1434         for param in generics.params {
1435             if let GenericParamKind::Lifetime { .. } = param.kind {
1436                 if is_late_bound(param.hir_id) {
1437                     return Some(param.span);
1438                 }
1439             }
1440         }
1441         visitor.visit_fn_decl(decl);
1442         visitor.has_late_bound_regions
1443     }
1444
1445     match node {
1446         Node::TraitItem(item) => match item.kind {
1447             hir::TraitItemKind::Fn(ref sig, _) => {
1448                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1449             }
1450             _ => None,
1451         },
1452         Node::ImplItem(item) => match item.kind {
1453             hir::ImplItemKind::Fn(ref sig, _) => {
1454                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1455             }
1456             _ => None,
1457         },
1458         Node::ForeignItem(item) => match item.kind {
1459             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1460                 has_late_bound_regions(tcx, item.def_id, generics, fn_decl)
1461             }
1462             _ => None,
1463         },
1464         Node::Item(item) => match item.kind {
1465             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1466                 has_late_bound_regions(tcx, item.def_id, generics, sig.decl)
1467             }
1468             _ => None,
1469         },
1470         _ => None,
1471     }
1472 }
1473
1474 struct AnonConstInParamTyDetector {
1475     in_param_ty: bool,
1476     found_anon_const_in_param_ty: bool,
1477     ct: HirId,
1478 }
1479
1480 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1481     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1482         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1483             let prev = self.in_param_ty;
1484             self.in_param_ty = true;
1485             self.visit_ty(ty);
1486             self.in_param_ty = prev;
1487         }
1488     }
1489
1490     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1491         if self.in_param_ty && self.ct == c.hir_id {
1492             self.found_anon_const_in_param_ty = true;
1493         } else {
1494             intravisit::walk_anon_const(self, c)
1495         }
1496     }
1497 }
1498
1499 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1500     use rustc_hir::*;
1501
1502     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1503
1504     let node = tcx.hir().get(hir_id);
1505     let parent_def_id = match node {
1506         Node::ImplItem(_)
1507         | Node::TraitItem(_)
1508         | Node::Variant(_)
1509         | Node::Ctor(..)
1510         | Node::Field(_) => {
1511             let parent_id = tcx.hir().get_parent_item(hir_id);
1512             Some(parent_id.to_def_id())
1513         }
1514         // FIXME(#43408) always enable this once `lazy_normalization` is
1515         // stable enough and does not need a feature gate anymore.
1516         Node::AnonConst(_) => {
1517             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1518
1519             let mut in_param_ty = false;
1520             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1521                 if let Some(generics) = node.generics() {
1522                     let mut visitor = AnonConstInParamTyDetector {
1523                         in_param_ty: false,
1524                         found_anon_const_in_param_ty: false,
1525                         ct: hir_id,
1526                     };
1527
1528                     visitor.visit_generics(generics);
1529                     in_param_ty = visitor.found_anon_const_in_param_ty;
1530                     break;
1531                 }
1532             }
1533
1534             if in_param_ty {
1535                 // We do not allow generic parameters in anon consts if we are inside
1536                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1537                 None
1538             } else if tcx.lazy_normalization() {
1539                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1540                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1541                     //
1542                     // struct Foo<const N: usize = { .. }>;
1543                     //        ^^^       ^          ^^^^^^ def id of this anon const
1544                     //        ^         ^ param_id
1545                     //        ^ parent_def_id
1546                     //
1547                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1548                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1549                     //
1550                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1551                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1552                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1553                     //
1554                     // We fix this by having this function return the parent's generics ourselves and truncating the
1555                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1556                     //
1557                     // For the above code example that means we want `substs: []`
1558                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1559                     // the def id of the `{ N + 1 }` anon const
1560                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1561                     //
1562                     // This has some implications for how we get the predicates available to the anon const
1563                     // see `explicit_predicates_of` for more information on this
1564                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1565                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1566                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1567                     // In the above example this would be .params[..N#0]
1568                     let params = generics.params[..param_def_idx as usize].to_owned();
1569                     let param_def_id_to_index =
1570                         params.iter().map(|param| (param.def_id, param.index)).collect();
1571
1572                     return ty::Generics {
1573                         // we set the parent of these generics to be our parent's parent so that we
1574                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1575                         // struct Foo<const N: usize, const M: usize = { ... }>;
1576                         parent: generics.parent,
1577                         parent_count: generics.parent_count,
1578                         params,
1579                         param_def_id_to_index,
1580                         has_self: generics.has_self,
1581                         has_late_bound_regions: generics.has_late_bound_regions,
1582                     };
1583                 }
1584
1585                 // HACK(eddyb) this provides the correct generics when
1586                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1587                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1588                 //
1589                 // Note that we do not supply the parent generics when using
1590                 // `min_const_generics`.
1591                 Some(parent_def_id.to_def_id())
1592             } else {
1593                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1594                 match parent_node {
1595                     // HACK(eddyb) this provides the correct generics for repeat
1596                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1597                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1598                     // as they shouldn't be able to cause query cycle errors.
1599                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1600                         if constant.hir_id() == hir_id =>
1601                     {
1602                         Some(parent_def_id.to_def_id())
1603                     }
1604                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1605                         if constant.hir_id == hir_id =>
1606                     {
1607                         Some(parent_def_id.to_def_id())
1608                     }
1609                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1610                         Some(tcx.typeck_root_def_id(def_id))
1611                     }
1612                     _ => None,
1613                 }
1614             }
1615         }
1616         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1617             Some(tcx.typeck_root_def_id(def_id))
1618         }
1619         Node::Item(item) => match item.kind {
1620             ItemKind::OpaqueTy(hir::OpaqueTy {
1621                 origin:
1622                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1623                 ..
1624             }) => Some(fn_def_id.to_def_id()),
1625             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1626                 let parent_id = tcx.hir().get_parent_item(hir_id);
1627                 assert_ne!(parent_id, CRATE_DEF_ID);
1628                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1629                 // Opaque types are always nested within another item, and
1630                 // inherit the generics of the item.
1631                 Some(parent_id.to_def_id())
1632             }
1633             _ => None,
1634         },
1635         _ => None,
1636     };
1637
1638     let mut opt_self = None;
1639     let mut allow_defaults = false;
1640
1641     let no_generics = hir::Generics::empty();
1642     let ast_generics = match node {
1643         Node::TraitItem(item) => &item.generics,
1644
1645         Node::ImplItem(item) => &item.generics,
1646
1647         Node::Item(item) => {
1648             match item.kind {
1649                 ItemKind::Fn(.., ref generics, _)
1650                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1651
1652                 ItemKind::TyAlias(_, ref generics)
1653                 | ItemKind::Enum(_, ref generics)
1654                 | ItemKind::Struct(_, ref generics)
1655                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1656                 | ItemKind::Union(_, ref generics) => {
1657                     allow_defaults = true;
1658                     generics
1659                 }
1660
1661                 ItemKind::Trait(_, _, ref generics, ..)
1662                 | ItemKind::TraitAlias(ref generics, ..) => {
1663                     // Add in the self type parameter.
1664                     //
1665                     // Something of a hack: use the node id for the trait, also as
1666                     // the node id for the Self type parameter.
1667                     let param_id = item.def_id;
1668
1669                     opt_self = Some(ty::GenericParamDef {
1670                         index: 0,
1671                         name: kw::SelfUpper,
1672                         def_id: param_id.to_def_id(),
1673                         pure_wrt_drop: false,
1674                         kind: ty::GenericParamDefKind::Type {
1675                             has_default: false,
1676                             object_lifetime_default: rl::Set1::Empty,
1677                             synthetic: false,
1678                         },
1679                     });
1680
1681                     allow_defaults = true;
1682                     generics
1683                 }
1684
1685                 _ => &no_generics,
1686             }
1687         }
1688
1689         Node::ForeignItem(item) => match item.kind {
1690             ForeignItemKind::Static(..) => &no_generics,
1691             ForeignItemKind::Fn(_, _, ref generics) => generics,
1692             ForeignItemKind::Type => &no_generics,
1693         },
1694
1695         _ => &no_generics,
1696     };
1697
1698     let has_self = opt_self.is_some();
1699     let mut parent_has_self = false;
1700     let mut own_start = has_self as u32;
1701     let parent_count = parent_def_id.map_or(0, |def_id| {
1702         let generics = tcx.generics_of(def_id);
1703         assert!(!has_self);
1704         parent_has_self = generics.has_self;
1705         own_start = generics.count() as u32;
1706         generics.parent_count + generics.params.len()
1707     });
1708
1709     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1710
1711     if let Some(opt_self) = opt_self {
1712         params.push(opt_self);
1713     }
1714
1715     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics);
1716     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1717         name: param.name.ident().name,
1718         index: own_start + i as u32,
1719         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1720         pure_wrt_drop: param.pure_wrt_drop,
1721         kind: ty::GenericParamDefKind::Lifetime,
1722     }));
1723
1724     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1725
1726     // Now create the real type and const parameters.
1727     let type_start = own_start - has_self as u32 + params.len() as u32;
1728     let mut i = 0;
1729
1730     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1731         GenericParamKind::Lifetime { .. } => None,
1732         GenericParamKind::Type { ref default, synthetic, .. } => {
1733             if !allow_defaults && default.is_some() {
1734                 if !tcx.features().default_type_parameter_fallback {
1735                     tcx.struct_span_lint_hir(
1736                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1737                         param.hir_id,
1738                         param.span,
1739                         |lint| {
1740                             lint.build(
1741                                 "defaults for type parameters are only allowed in \
1742                                  `struct`, `enum`, `type`, or `trait` definitions",
1743                             )
1744                             .emit();
1745                         },
1746                     );
1747                 }
1748             }
1749
1750             let kind = ty::GenericParamDefKind::Type {
1751                 has_default: default.is_some(),
1752                 object_lifetime_default: object_lifetime_defaults
1753                     .as_ref()
1754                     .map_or(rl::Set1::Empty, |o| o[i]),
1755                 synthetic,
1756             };
1757
1758             let param_def = ty::GenericParamDef {
1759                 index: type_start + i as u32,
1760                 name: param.name.ident().name,
1761                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1762                 pure_wrt_drop: param.pure_wrt_drop,
1763                 kind,
1764             };
1765             i += 1;
1766             Some(param_def)
1767         }
1768         GenericParamKind::Const { default, .. } => {
1769             if !allow_defaults && default.is_some() {
1770                 tcx.sess.span_err(
1771                     param.span,
1772                     "defaults for const parameters are only allowed in \
1773                     `struct`, `enum`, `type`, or `trait` definitions",
1774                 );
1775             }
1776
1777             let param_def = ty::GenericParamDef {
1778                 index: type_start + i as u32,
1779                 name: param.name.ident().name,
1780                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1781                 pure_wrt_drop: param.pure_wrt_drop,
1782                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1783             };
1784             i += 1;
1785             Some(param_def)
1786         }
1787     }));
1788
1789     // provide junk type parameter defs - the only place that
1790     // cares about anything but the length is instantiation,
1791     // and we don't do that for closures.
1792     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1793         let dummy_args = if gen.is_some() {
1794             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1795         } else {
1796             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1797         };
1798
1799         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1800             index: type_start + i as u32,
1801             name: Symbol::intern(arg),
1802             def_id,
1803             pure_wrt_drop: false,
1804             kind: ty::GenericParamDefKind::Type {
1805                 has_default: false,
1806                 object_lifetime_default: rl::Set1::Empty,
1807                 synthetic: false,
1808             },
1809         }));
1810     }
1811
1812     // provide junk type parameter defs for const blocks.
1813     if let Node::AnonConst(_) = node {
1814         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1815         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1816             params.push(ty::GenericParamDef {
1817                 index: type_start,
1818                 name: Symbol::intern("<const_ty>"),
1819                 def_id,
1820                 pure_wrt_drop: false,
1821                 kind: ty::GenericParamDefKind::Type {
1822                     has_default: false,
1823                     object_lifetime_default: rl::Set1::Empty,
1824                     synthetic: false,
1825                 },
1826             });
1827         }
1828     }
1829
1830     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1831
1832     ty::Generics {
1833         parent: parent_def_id,
1834         parent_count,
1835         params,
1836         param_def_id_to_index,
1837         has_self: has_self || parent_has_self,
1838         has_late_bound_regions: has_late_bound_regions(tcx, node),
1839     }
1840 }
1841
1842 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1843     generic_args.iter().any(|arg| match arg {
1844         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1845         hir::GenericArg::Infer(_) => true,
1846         _ => false,
1847     })
1848 }
1849
1850 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1851 /// use inference to provide suggestions for the appropriate type if possible.
1852 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1853     debug!(?ty);
1854     use hir::TyKind::*;
1855     match &ty.kind {
1856         Infer => true,
1857         Slice(ty) => is_suggestable_infer_ty(ty),
1858         Array(ty, length) => {
1859             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1860         }
1861         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1862         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1863         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1864         Path(hir::QPath::TypeRelative(ty, segment)) => {
1865             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1866         }
1867         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1868             ty_opt.map_or(false, is_suggestable_infer_ty)
1869                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1870         }
1871         _ => false,
1872     }
1873 }
1874
1875 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1876     if let hir::FnRetTy::Return(ty) = output {
1877         if is_suggestable_infer_ty(ty) {
1878             return Some(&*ty);
1879         }
1880     }
1881     None
1882 }
1883
1884 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1885     use rustc_hir::Node::*;
1886     use rustc_hir::*;
1887
1888     let def_id = def_id.expect_local();
1889     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1890
1891     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1892
1893     match tcx.hir().get(hir_id) {
1894         TraitItem(hir::TraitItem {
1895             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1896             ident,
1897             generics,
1898             ..
1899         })
1900         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1901             infer_return_ty_for_fn_sig(tcx, sig, *ident, generics, def_id, &icx)
1902         }
1903
1904         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. }) => {
1905             // Do not try to inference the return type for a impl method coming from a trait
1906             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1907                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1908                 && i.of_trait.is_some()
1909             {
1910                 <dyn AstConv<'_>>::ty_of_fn(
1911                     &icx,
1912                     hir_id,
1913                     sig.header.unsafety,
1914                     sig.header.abi,
1915                     sig.decl,
1916                     generics,
1917                     Some(ident.span),
1918                     None,
1919                 )
1920             } else {
1921                 infer_return_ty_for_fn_sig(tcx, sig, *ident, generics, def_id, &icx)
1922             }
1923         }
1924
1925         TraitItem(hir::TraitItem {
1926             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1927             ident,
1928             generics,
1929             ..
1930         }) => <dyn AstConv<'_>>::ty_of_fn(
1931             &icx,
1932             hir_id,
1933             header.unsafety,
1934             header.abi,
1935             decl,
1936             generics,
1937             Some(ident.span),
1938             None,
1939         ),
1940
1941         ForeignItem(&hir::ForeignItem {
1942             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1943         }) => {
1944             let abi = tcx.hir().get_foreign_abi(hir_id);
1945             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1946         }
1947
1948         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1949             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1950             let inputs =
1951                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1952             ty::Binder::dummy(tcx.mk_fn_sig(
1953                 inputs,
1954                 ty,
1955                 false,
1956                 hir::Unsafety::Normal,
1957                 abi::Abi::Rust,
1958             ))
1959         }
1960
1961         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1962             // Closure signatures are not like other function
1963             // signatures and cannot be accessed through `fn_sig`. For
1964             // example, a closure signature excludes the `self`
1965             // argument. In any case they are embedded within the
1966             // closure type as part of the `ClosureSubsts`.
1967             //
1968             // To get the signature of a closure, you should use the
1969             // `sig` method on the `ClosureSubsts`:
1970             //
1971             //    substs.as_closure().sig(def_id, tcx)
1972             bug!(
1973                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1974             );
1975         }
1976
1977         x => {
1978             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1979         }
1980     }
1981 }
1982
1983 fn infer_return_ty_for_fn_sig<'tcx>(
1984     tcx: TyCtxt<'tcx>,
1985     sig: &hir::FnSig<'_>,
1986     ident: Ident,
1987     generics: &hir::Generics<'_>,
1988     def_id: LocalDefId,
1989     icx: &ItemCtxt<'tcx>,
1990 ) -> ty::PolyFnSig<'tcx> {
1991     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1992
1993     match get_infer_ret_ty(&sig.decl.output) {
1994         Some(ty) => {
1995             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1996             // Typeck doesn't expect erased regions to be returned from `type_of`.
1997             let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1998                 ty::ReErased => tcx.lifetimes.re_static,
1999                 _ => r,
2000             });
2001             let fn_sig = ty::Binder::dummy(fn_sig);
2002
2003             let mut visitor = HirPlaceholderCollector::default();
2004             visitor.visit_ty(ty);
2005             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
2006             let ret_ty = fn_sig.skip_binder().output();
2007             if ret_ty.is_suggestable(tcx) {
2008                 diag.span_suggestion(
2009                     ty.span,
2010                     "replace with the correct return type",
2011                     ret_ty.to_string(),
2012                     Applicability::MachineApplicable,
2013                 );
2014             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
2015                 let fn_sig = ret_ty.fn_sig(tcx);
2016                 if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable(tcx)) {
2017                     diag.span_suggestion(
2018                         ty.span,
2019                         "replace with the correct return type",
2020                         fn_sig.to_string(),
2021                         Applicability::MachineApplicable,
2022                     );
2023                 }
2024             } else if ret_ty.is_closure() {
2025                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
2026                 // to prevent the user from getting a papercut while trying to use the unique closure
2027                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
2028                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
2029                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
2030             }
2031             diag.emit();
2032
2033             fn_sig
2034         }
2035         None => <dyn AstConv<'_>>::ty_of_fn(
2036             icx,
2037             hir_id,
2038             sig.header.unsafety,
2039             sig.header.abi,
2040             sig.decl,
2041             generics,
2042             Some(ident.span),
2043             None,
2044         ),
2045     }
2046 }
2047
2048 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
2049     let icx = ItemCtxt::new(tcx, def_id);
2050     match tcx.hir().expect_item(def_id.expect_local()).kind {
2051         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
2052             let selfty = tcx.type_of(def_id);
2053             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
2054         }),
2055         _ => bug!(),
2056     }
2057 }
2058
2059 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2060     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2061     let item = tcx.hir().expect_item(def_id.expect_local());
2062     match &item.kind {
2063         hir::ItemKind::Impl(hir::Impl {
2064             polarity: hir::ImplPolarity::Negative(span),
2065             of_trait,
2066             ..
2067         }) => {
2068             if is_rustc_reservation {
2069                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2070                 tcx.sess.span_err(span, "reservation impls can't be negative");
2071             }
2072             ty::ImplPolarity::Negative
2073         }
2074         hir::ItemKind::Impl(hir::Impl {
2075             polarity: hir::ImplPolarity::Positive,
2076             of_trait: None,
2077             ..
2078         }) => {
2079             if is_rustc_reservation {
2080                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2081             }
2082             ty::ImplPolarity::Positive
2083         }
2084         hir::ItemKind::Impl(hir::Impl {
2085             polarity: hir::ImplPolarity::Positive,
2086             of_trait: Some(_),
2087             ..
2088         }) => {
2089             if is_rustc_reservation {
2090                 ty::ImplPolarity::Reservation
2091             } else {
2092                 ty::ImplPolarity::Positive
2093             }
2094         }
2095         item => bug!("impl_polarity: {:?} not an impl", item),
2096     }
2097 }
2098
2099 /// Returns the early-bound lifetimes declared in this generics
2100 /// listing. For anything other than fns/methods, this is just all
2101 /// the lifetimes that are declared. For fns or methods, we have to
2102 /// screen out those that do not appear in any where-clauses etc using
2103 /// `resolve_lifetime::early_bound_lifetimes`.
2104 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2105     tcx: TyCtxt<'tcx>,
2106     def_id: LocalDefId,
2107     generics: &'a hir::Generics<'a>,
2108 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2109     let late_bound_map = if generics.params.is_empty() {
2110         // This function may be called on `def_id == CRATE_DEF_ID`,
2111         // which makes `is_late_bound_map` ICE.  Don't even try if there
2112         // is no generic parameter.
2113         None
2114     } else {
2115         tcx.is_late_bound_map(def_id)
2116     };
2117     let is_late_bound = move |hir_id| {
2118         let id = tcx.hir().local_def_id(hir_id);
2119         late_bound_map.map_or(false, |(_, set)| set.contains(&id))
2120     };
2121     generics.params.iter().filter(move |param| match param.kind {
2122         GenericParamKind::Lifetime { .. } => !is_late_bound(param.hir_id),
2123         _ => false,
2124     })
2125 }
2126
2127 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2128 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2129 /// inferred constraints concerning which regions outlive other regions.
2130 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2131     debug!("predicates_defined_on({:?})", def_id);
2132     let mut result = tcx.explicit_predicates_of(def_id);
2133     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2134     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2135     if !inferred_outlives.is_empty() {
2136         debug!(
2137             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2138             def_id, inferred_outlives,
2139         );
2140         if result.predicates.is_empty() {
2141             result.predicates = inferred_outlives;
2142         } else {
2143             result.predicates = tcx
2144                 .arena
2145                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2146         }
2147     }
2148
2149     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2150     result
2151 }
2152
2153 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2154 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2155 /// `Self: Trait` predicates for traits.
2156 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2157     let mut result = tcx.predicates_defined_on(def_id);
2158
2159     if tcx.is_trait(def_id) {
2160         // For traits, add `Self: Trait` predicate. This is
2161         // not part of the predicates that a user writes, but it
2162         // is something that one must prove in order to invoke a
2163         // method or project an associated type.
2164         //
2165         // In the chalk setup, this predicate is not part of the
2166         // "predicates" for a trait item. But it is useful in
2167         // rustc because if you directly (e.g.) invoke a trait
2168         // method like `Trait::method(...)`, you must naturally
2169         // prove that the trait applies to the types that were
2170         // used, and adding the predicate into this list ensures
2171         // that this is done.
2172         //
2173         // We use a DUMMY_SP here as a way to signal trait bounds that come
2174         // from the trait itself that *shouldn't* be shown as the source of
2175         // an obligation and instead be skipped. Otherwise we'd use
2176         // `tcx.def_span(def_id);`
2177         let span = rustc_span::DUMMY_SP;
2178         result.predicates =
2179             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2180                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2181                 span,
2182             ))));
2183     }
2184     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2185     result
2186 }
2187
2188 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2189 /// N.B., this does not include any implied/inferred constraints.
2190 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2191     use rustc_hir::*;
2192
2193     debug!("explicit_predicates_of(def_id={:?})", def_id);
2194
2195     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2196     let node = tcx.hir().get(hir_id);
2197
2198     let mut is_trait = None;
2199     let mut is_default_impl_trait = None;
2200
2201     let icx = ItemCtxt::new(tcx, def_id);
2202
2203     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2204
2205     // We use an `IndexSet` to preserves order of insertion.
2206     // Preserving the order of insertion is important here so as not to break UI tests.
2207     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2208
2209     let ast_generics = match node {
2210         Node::TraitItem(item) => &item.generics,
2211
2212         Node::ImplItem(item) => &item.generics,
2213
2214         Node::Item(item) => {
2215             match item.kind {
2216                 ItemKind::Impl(ref impl_) => {
2217                     if impl_.defaultness.is_default() {
2218                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2219                     }
2220                     &impl_.generics
2221                 }
2222                 ItemKind::Fn(.., ref generics, _)
2223                 | ItemKind::TyAlias(_, ref generics)
2224                 | ItemKind::Enum(_, ref generics)
2225                 | ItemKind::Struct(_, ref generics)
2226                 | ItemKind::Union(_, ref generics) => generics,
2227
2228                 ItemKind::Trait(_, _, ref generics, ..) => {
2229                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2230                     generics
2231                 }
2232                 ItemKind::TraitAlias(ref generics, _) => {
2233                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2234                     generics
2235                 }
2236                 ItemKind::OpaqueTy(OpaqueTy {
2237                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2238                     ..
2239                 }) => {
2240                     // return-position impl trait
2241                     //
2242                     // We don't inherit predicates from the parent here:
2243                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2244                     // then the return type is `f::<'static, T>::{{opaque}}`.
2245                     //
2246                     // If we inherited the predicates of `f` then we would
2247                     // require that `T: 'static` to show that the return
2248                     // type is well-formed.
2249                     //
2250                     // The only way to have something with this opaque type
2251                     // is from the return type of the containing function,
2252                     // which will ensure that the function's predicates
2253                     // hold.
2254                     return ty::GenericPredicates { parent: None, predicates: &[] };
2255                 }
2256                 ItemKind::OpaqueTy(OpaqueTy {
2257                     ref generics,
2258                     origin: hir::OpaqueTyOrigin::TyAlias,
2259                     ..
2260                 }) => {
2261                     // type-alias impl trait
2262                     generics
2263                 }
2264
2265                 _ => NO_GENERICS,
2266             }
2267         }
2268
2269         Node::ForeignItem(item) => match item.kind {
2270             ForeignItemKind::Static(..) => NO_GENERICS,
2271             ForeignItemKind::Fn(_, _, ref generics) => generics,
2272             ForeignItemKind::Type => NO_GENERICS,
2273         },
2274
2275         _ => NO_GENERICS,
2276     };
2277
2278     let generics = tcx.generics_of(def_id);
2279     let parent_count = generics.parent_count as u32;
2280     let has_own_self = generics.has_self && parent_count == 0;
2281
2282     // Below we'll consider the bounds on the type parameters (including `Self`)
2283     // and the explicit where-clauses, but to get the full set of predicates
2284     // on a trait we need to add in the supertrait bounds and bounds found on
2285     // associated types.
2286     if let Some(_trait_ref) = is_trait {
2287         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2288     }
2289
2290     // In default impls, we can assume that the self type implements
2291     // the trait. So in:
2292     //
2293     //     default impl Foo for Bar { .. }
2294     //
2295     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2296     // (see below). Recall that a default impl is not itself an impl, but rather a
2297     // set of defaults that can be incorporated into another impl.
2298     if let Some(trait_ref) = is_default_impl_trait {
2299         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2300     }
2301
2302     // Collect the region predicates that were declared inline as
2303     // well. In the case of parameters declared on a fn or method, we
2304     // have to be careful to only iterate over early-bound regions.
2305     let mut index = parent_count + has_own_self as u32;
2306     for param in early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics) {
2307         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2308             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2309             index,
2310             name: param.name.ident().name,
2311         }));
2312         index += 1;
2313
2314         match param.kind {
2315             GenericParamKind::Lifetime { .. } => {
2316                 param.bounds.iter().for_each(|bound| match bound {
2317                     hir::GenericBound::Outlives(lt) => {
2318                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2319                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2320                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2321                     }
2322                     _ => bug!(),
2323                 });
2324             }
2325             _ => bug!(),
2326         }
2327     }
2328
2329     // Collect the predicates that were written inline by the user on each
2330     // type parameter (e.g., `<T: Foo>`).
2331     for param in ast_generics.params {
2332         match param.kind {
2333             // We already dealt with early bound lifetimes above.
2334             GenericParamKind::Lifetime { .. } => (),
2335             GenericParamKind::Type { .. } => {
2336                 let name = param.name.ident().name;
2337                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2338                 index += 1;
2339
2340                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2341                 // Params are implicitly sized unless a `?Sized` bound is found
2342                 <dyn AstConv<'_>>::add_implicitly_sized(
2343                     &icx,
2344                     &mut bounds,
2345                     param.bounds,
2346                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2347                     param.span,
2348                 );
2349                 predicates.extend(bounds.predicates(tcx, param_ty));
2350             }
2351             GenericParamKind::Const { .. } => {
2352                 // Bounds on const parameters are currently not possible.
2353                 debug_assert!(param.bounds.is_empty());
2354                 index += 1;
2355             }
2356         }
2357     }
2358
2359     // Add in the bounds that appear in the where-clause.
2360     let where_clause = &ast_generics.where_clause;
2361     for predicate in where_clause.predicates {
2362         match predicate {
2363             hir::WherePredicate::BoundPredicate(bound_pred) => {
2364                 let ty = icx.to_ty(bound_pred.bounded_ty);
2365                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2366
2367                 // Keep the type around in a dummy predicate, in case of no bounds.
2368                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2369                 // is still checked for WF.
2370                 if bound_pred.bounds.is_empty() {
2371                     if let ty::Param(_) = ty.kind() {
2372                         // This is a `where T:`, which can be in the HIR from the
2373                         // transformation that moves `?Sized` to `T`'s declaration.
2374                         // We can skip the predicate because type parameters are
2375                         // trivially WF, but also we *should*, to avoid exposing
2376                         // users who never wrote `where Type:,` themselves, to
2377                         // compiler/tooling bugs from not handling WF predicates.
2378                     } else {
2379                         let span = bound_pred.bounded_ty.span;
2380                         let re_root_empty = tcx.lifetimes.re_root_empty;
2381                         let predicate = ty::Binder::bind_with_vars(
2382                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2383                                 ty,
2384                                 re_root_empty,
2385                             )),
2386                             bound_vars,
2387                         );
2388                         predicates.insert((predicate.to_predicate(tcx), span));
2389                     }
2390                 }
2391
2392                 let mut bounds = Bounds::default();
2393                 <dyn AstConv<'_>>::add_bounds(
2394                     &icx,
2395                     ty,
2396                     bound_pred.bounds.iter(),
2397                     &mut bounds,
2398                     bound_vars,
2399                 );
2400                 predicates.extend(bounds.predicates(tcx, ty));
2401             }
2402
2403             hir::WherePredicate::RegionPredicate(region_pred) => {
2404                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2405                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2406                     let (r2, span) = match bound {
2407                         hir::GenericBound::Outlives(lt) => {
2408                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2409                         }
2410                         _ => bug!(),
2411                     };
2412                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2413                         ty::OutlivesPredicate(r1, r2),
2414                     ))
2415                     .to_predicate(icx.tcx);
2416
2417                     (pred, span)
2418                 }))
2419             }
2420
2421             hir::WherePredicate::EqPredicate(..) => {
2422                 // FIXME(#20041)
2423             }
2424         }
2425     }
2426
2427     if tcx.features().generic_const_exprs {
2428         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2429     }
2430
2431     let mut predicates: Vec<_> = predicates.into_iter().collect();
2432
2433     // Subtle: before we store the predicates into the tcx, we
2434     // sort them so that predicates like `T: Foo<Item=U>` come
2435     // before uses of `U`.  This avoids false ambiguity errors
2436     // in trait checking. See `setup_constraining_predicates`
2437     // for details.
2438     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2439         let self_ty = tcx.type_of(def_id);
2440         let trait_ref = tcx.impl_trait_ref(def_id);
2441         cgp::setup_constraining_predicates(
2442             tcx,
2443             &mut predicates,
2444             trait_ref,
2445             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2446         );
2447     }
2448
2449     let result = ty::GenericPredicates {
2450         parent: generics.parent,
2451         predicates: tcx.arena.alloc_from_iter(predicates),
2452     };
2453     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2454     result
2455 }
2456
2457 fn const_evaluatable_predicates_of<'tcx>(
2458     tcx: TyCtxt<'tcx>,
2459     def_id: LocalDefId,
2460 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2461     struct ConstCollector<'tcx> {
2462         tcx: TyCtxt<'tcx>,
2463         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2464     }
2465
2466     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2467         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2468             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2469             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2470             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2471                 assert_eq!(uv.promoted, None);
2472                 let span = self.tcx.hir().span(c.hir_id);
2473                 self.preds.insert((
2474                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2475                         .to_predicate(self.tcx),
2476                     span,
2477                 ));
2478             }
2479         }
2480
2481         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2482             // Do not look into const param defaults,
2483             // these get checked when they are actually instantiated.
2484             //
2485             // We do not want the following to error:
2486             //
2487             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2488             //     struct Bar<const N: usize>(Foo<N, 3>);
2489         }
2490     }
2491
2492     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2493     let node = tcx.hir().get(hir_id);
2494
2495     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2496     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2497         if let Some(of_trait) = &impl_.of_trait {
2498             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2499             collector.visit_trait_ref(of_trait);
2500         }
2501
2502         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2503         collector.visit_ty(impl_.self_ty);
2504     }
2505
2506     if let Some(generics) = node.generics() {
2507         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2508         collector.visit_generics(generics);
2509     }
2510
2511     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2512         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2513         collector.visit_fn_decl(fn_sig.decl);
2514     }
2515     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2516
2517     collector.preds
2518 }
2519
2520 fn trait_explicit_predicates_and_bounds(
2521     tcx: TyCtxt<'_>,
2522     def_id: LocalDefId,
2523 ) -> ty::GenericPredicates<'_> {
2524     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2525     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2526 }
2527
2528 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2529     let def_kind = tcx.def_kind(def_id);
2530     if let DefKind::Trait = def_kind {
2531         // Remove bounds on associated types from the predicates, they will be
2532         // returned by `explicit_item_bounds`.
2533         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2534         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2535
2536         let is_assoc_item_ty = |ty: Ty<'_>| {
2537             // For a predicate from a where clause to become a bound on an
2538             // associated type:
2539             // * It must use the identity substs of the item.
2540             //     * Since any generic parameters on the item are not in scope,
2541             //       this means that the item is not a GAT, and its identity
2542             //       substs are the same as the trait's.
2543             // * It must be an associated type for this trait (*not* a
2544             //   supertrait).
2545             if let ty::Projection(projection) = ty.kind() {
2546                 projection.substs == trait_identity_substs
2547                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2548             } else {
2549                 false
2550             }
2551         };
2552
2553         let predicates: Vec<_> = predicates_and_bounds
2554             .predicates
2555             .iter()
2556             .copied()
2557             .filter(|(pred, _)| match pred.kind().skip_binder() {
2558                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2559                 ty::PredicateKind::Projection(proj) => {
2560                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2561                 }
2562                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2563                 _ => true,
2564             })
2565             .collect();
2566         if predicates.len() == predicates_and_bounds.predicates.len() {
2567             predicates_and_bounds
2568         } else {
2569             ty::GenericPredicates {
2570                 parent: predicates_and_bounds.parent,
2571                 predicates: tcx.arena.alloc_slice(&predicates),
2572             }
2573         }
2574     } else {
2575         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2576             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2577             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2578                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2579                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2580                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2581                 //
2582                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2583                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2584                 //        ^^^                                             explicit_predicates_of on
2585                 //        parent item we dont have set as the
2586                 //        parent of generics returned by `generics_of`
2587                 //
2588                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2589                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2590                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2591                 return tcx.explicit_predicates_of(item_def_id);
2592             }
2593         }
2594         gather_explicit_predicates_of(tcx, def_id)
2595     }
2596 }
2597
2598 /// Converts a specific `GenericBound` from the AST into a set of
2599 /// predicates that apply to the self type. A vector is returned
2600 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2601 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2602 /// and `<T as Bar>::X == i32`).
2603 fn predicates_from_bound<'tcx>(
2604     astconv: &dyn AstConv<'tcx>,
2605     param_ty: Ty<'tcx>,
2606     bound: &'tcx hir::GenericBound<'tcx>,
2607     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2608 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2609     let mut bounds = Bounds::default();
2610     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2611     bounds.predicates(astconv.tcx(), param_ty).collect()
2612 }
2613
2614 fn compute_sig_of_foreign_fn_decl<'tcx>(
2615     tcx: TyCtxt<'tcx>,
2616     def_id: DefId,
2617     decl: &'tcx hir::FnDecl<'tcx>,
2618     abi: abi::Abi,
2619     ident: Ident,
2620 ) -> ty::PolyFnSig<'tcx> {
2621     let unsafety = if abi == abi::Abi::RustIntrinsic {
2622         intrinsic_operation_unsafety(tcx.item_name(def_id))
2623     } else {
2624         hir::Unsafety::Unsafe
2625     };
2626     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2627     let fty = <dyn AstConv<'_>>::ty_of_fn(
2628         &ItemCtxt::new(tcx, def_id),
2629         hir_id,
2630         unsafety,
2631         abi,
2632         decl,
2633         &hir::Generics::empty(),
2634         Some(ident.span),
2635         None,
2636     );
2637
2638     // Feature gate SIMD types in FFI, since I am not sure that the
2639     // ABIs are handled at all correctly. -huonw
2640     if abi != abi::Abi::RustIntrinsic
2641         && abi != abi::Abi::PlatformIntrinsic
2642         && !tcx.features().simd_ffi
2643     {
2644         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2645             if ty.is_simd() {
2646                 let snip = tcx
2647                     .sess
2648                     .source_map()
2649                     .span_to_snippet(ast_ty.span)
2650                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2651                 tcx.sess
2652                     .struct_span_err(
2653                         ast_ty.span,
2654                         &format!(
2655                             "use of SIMD type{} in FFI is highly experimental and \
2656                              may result in invalid code",
2657                             snip
2658                         ),
2659                     )
2660                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2661                     .emit();
2662             }
2663         };
2664         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2665             check(input, *ty)
2666         }
2667         if let hir::FnRetTy::Return(ref ty) = decl.output {
2668             check(ty, fty.output().skip_binder())
2669         }
2670     }
2671
2672     fty
2673 }
2674
2675 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2676     match tcx.hir().get_if_local(def_id) {
2677         Some(Node::ForeignItem(..)) => true,
2678         Some(_) => false,
2679         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2680     }
2681 }
2682
2683 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2684     match tcx.hir().get_if_local(def_id) {
2685         Some(Node::Expr(&rustc_hir::Expr {
2686             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2687             ..
2688         })) => tcx.hir().body(body_id).generator_kind(),
2689         Some(_) => None,
2690         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2691     }
2692 }
2693
2694 fn from_target_feature(
2695     tcx: TyCtxt<'_>,
2696     id: DefId,
2697     attr: &ast::Attribute,
2698     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2699     target_features: &mut Vec<Symbol>,
2700 ) {
2701     let Some(list) = attr.meta_item_list() else { return };
2702     let bad_item = |span| {
2703         let msg = "malformed `target_feature` attribute input";
2704         let code = "enable = \"..\"".to_owned();
2705         tcx.sess
2706             .struct_span_err(span, msg)
2707             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2708             .emit();
2709     };
2710     let rust_features = tcx.features();
2711     for item in list {
2712         // Only `enable = ...` is accepted in the meta-item list.
2713         if !item.has_name(sym::enable) {
2714             bad_item(item.span());
2715             continue;
2716         }
2717
2718         // Must be of the form `enable = "..."` (a string).
2719         let Some(value) = item.value_str() else {
2720             bad_item(item.span());
2721             continue;
2722         };
2723
2724         // We allow comma separation to enable multiple features.
2725         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2726             let Some(feature_gate) = supported_target_features.get(feature) else {
2727                 let msg =
2728                     format!("the feature named `{}` is not valid for this target", feature);
2729                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2730                 err.span_label(
2731                     item.span(),
2732                     format!("`{}` is not valid for this target", feature),
2733                 );
2734                 if let Some(stripped) = feature.strip_prefix('+') {
2735                     let valid = supported_target_features.contains_key(stripped);
2736                     if valid {
2737                         err.help("consider removing the leading `+` in the feature name");
2738                     }
2739                 }
2740                 err.emit();
2741                 return None;
2742             };
2743
2744             // Only allow features whose feature gates have been enabled.
2745             let allowed = match feature_gate.as_ref().copied() {
2746                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2747                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2748                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2749                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2750                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2751                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2752                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2753                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2754                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2755                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2756                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2757                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2758                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2759                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2760                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2761                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2762                 Some(name) => bug!("unknown target feature gate {}", name),
2763                 None => true,
2764             };
2765             if !allowed && id.is_local() {
2766                 feature_err(
2767                     &tcx.sess.parse_sess,
2768                     feature_gate.unwrap(),
2769                     item.span(),
2770                     &format!("the target feature `{}` is currently unstable", feature),
2771                 )
2772                 .emit();
2773             }
2774             Some(Symbol::intern(feature))
2775         }));
2776     }
2777 }
2778
2779 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2780     use rustc_middle::mir::mono::Linkage::*;
2781
2782     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2783     // applicable to variable declarations and may not really make sense for
2784     // Rust code in the first place but allow them anyway and trust that the
2785     // user knows what they're doing. Who knows, unanticipated use cases may pop
2786     // up in the future.
2787     //
2788     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2789     // and don't have to be, LLVM treats them as no-ops.
2790     match name {
2791         "appending" => Appending,
2792         "available_externally" => AvailableExternally,
2793         "common" => Common,
2794         "extern_weak" => ExternalWeak,
2795         "external" => External,
2796         "internal" => Internal,
2797         "linkonce" => LinkOnceAny,
2798         "linkonce_odr" => LinkOnceODR,
2799         "private" => Private,
2800         "weak" => WeakAny,
2801         "weak_odr" => WeakODR,
2802         _ => {
2803             let span = tcx.hir().span_if_local(def_id);
2804             if let Some(span) = span {
2805                 tcx.sess.span_fatal(span, "invalid linkage specified")
2806             } else {
2807                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2808             }
2809         }
2810     }
2811 }
2812
2813 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2814     let attrs = tcx.get_attrs(id);
2815
2816     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2817     if tcx.should_inherit_track_caller(id) {
2818         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2819     }
2820
2821     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2822     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2823         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2824             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2825         }
2826     }
2827
2828     // The panic_no_unwind function called by TerminatorKind::Abort will never
2829     // unwind. If the panic handler that it invokes unwind then it will simply
2830     // call the panic handler again.
2831     if Some(id) == tcx.lang_items().panic_no_unwind() {
2832         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2833     }
2834
2835     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2836
2837     let mut inline_span = None;
2838     let mut link_ordinal_span = None;
2839     let mut no_sanitize_span = None;
2840     for attr in attrs.iter() {
2841         if attr.has_name(sym::cold) {
2842             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2843         } else if attr.has_name(sym::rustc_allocator) {
2844             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2845         } else if attr.has_name(sym::ffi_returns_twice) {
2846             if tcx.is_foreign_item(id) {
2847                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2848             } else {
2849                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2850                 struct_span_err!(
2851                     tcx.sess,
2852                     attr.span,
2853                     E0724,
2854                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2855                 )
2856                 .emit();
2857             }
2858         } else if attr.has_name(sym::ffi_pure) {
2859             if tcx.is_foreign_item(id) {
2860                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2861                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2862                     struct_span_err!(
2863                         tcx.sess,
2864                         attr.span,
2865                         E0757,
2866                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2867                     )
2868                     .emit();
2869                 } else {
2870                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2871                 }
2872             } else {
2873                 // `#[ffi_pure]` is only allowed on foreign functions
2874                 struct_span_err!(
2875                     tcx.sess,
2876                     attr.span,
2877                     E0755,
2878                     "`#[ffi_pure]` may only be used on foreign functions"
2879                 )
2880                 .emit();
2881             }
2882         } else if attr.has_name(sym::ffi_const) {
2883             if tcx.is_foreign_item(id) {
2884                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2885             } else {
2886                 // `#[ffi_const]` is only allowed on foreign functions
2887                 struct_span_err!(
2888                     tcx.sess,
2889                     attr.span,
2890                     E0756,
2891                     "`#[ffi_const]` may only be used on foreign functions"
2892                 )
2893                 .emit();
2894             }
2895         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2896             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2897         } else if attr.has_name(sym::naked) {
2898             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2899         } else if attr.has_name(sym::no_mangle) {
2900             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2901         } else if attr.has_name(sym::no_coverage) {
2902             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2903         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2904             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2905         } else if attr.has_name(sym::used) {
2906             let inner = attr.meta_item_list();
2907             match inner.as_deref() {
2908                 Some([item]) if item.has_name(sym::linker) => {
2909                     if !tcx.features().used_with_arg {
2910                         feature_err(
2911                             &tcx.sess.parse_sess,
2912                             sym::used_with_arg,
2913                             attr.span,
2914                             "`#[used(linker)]` is currently unstable",
2915                         )
2916                         .emit();
2917                     }
2918                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2919                 }
2920                 Some([item]) if item.has_name(sym::compiler) => {
2921                     if !tcx.features().used_with_arg {
2922                         feature_err(
2923                             &tcx.sess.parse_sess,
2924                             sym::used_with_arg,
2925                             attr.span,
2926                             "`#[used(compiler)]` is currently unstable",
2927                         )
2928                         .emit();
2929                     }
2930                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2931                 }
2932                 Some(_) => {
2933                     tcx.sess
2934                         .struct_span_err(
2935                             attr.span,
2936                             "expected `used`, `used(compiler)` or `used(linker)`",
2937                         )
2938                         .emit();
2939                 }
2940                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2941             }
2942         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2943             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2944                 struct_span_err!(
2945                     tcx.sess,
2946                     attr.span,
2947                     E0776,
2948                     "`#[cmse_nonsecure_entry]` requires C ABI"
2949                 )
2950                 .emit();
2951             }
2952             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2953                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2954                     .emit();
2955             }
2956             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2957         } else if attr.has_name(sym::thread_local) {
2958             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2959         } else if attr.has_name(sym::track_caller) {
2960             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2961                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2962                     .emit();
2963             }
2964             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2965                 feature_err(
2966                     &tcx.sess.parse_sess,
2967                     sym::closure_track_caller,
2968                     attr.span,
2969                     "`#[track_caller]` on closures is currently unstable",
2970                 )
2971                 .emit();
2972             }
2973             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2974         } else if attr.has_name(sym::export_name) {
2975             if let Some(s) = attr.value_str() {
2976                 if s.as_str().contains('\0') {
2977                     // `#[export_name = ...]` will be converted to a null-terminated string,
2978                     // so it may not contain any null characters.
2979                     struct_span_err!(
2980                         tcx.sess,
2981                         attr.span,
2982                         E0648,
2983                         "`export_name` may not contain null characters"
2984                     )
2985                     .emit();
2986                 }
2987                 codegen_fn_attrs.export_name = Some(s);
2988             }
2989         } else if attr.has_name(sym::target_feature) {
2990             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2991                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2992                     // The `#[target_feature]` attribute is allowed on
2993                     // WebAssembly targets on all functions, including safe
2994                     // ones. Other targets require that `#[target_feature]` is
2995                     // only applied to unsafe functions (pending the
2996                     // `target_feature_11` feature) because on most targets
2997                     // execution of instructions that are not supported is
2998                     // considered undefined behavior. For WebAssembly which is a
2999                     // 100% safe target at execution time it's not possible to
3000                     // execute undefined instructions, and even if a future
3001                     // feature was added in some form for this it would be a
3002                     // deterministic trap. There is no undefined behavior when
3003                     // executing WebAssembly so `#[target_feature]` is allowed
3004                     // on safe functions (but again, only for WebAssembly)
3005                     //
3006                     // Note that this is also allowed if `actually_rustdoc` so
3007                     // if a target is documenting some wasm-specific code then
3008                     // it's not spuriously denied.
3009                 } else if !tcx.features().target_feature_11 {
3010                     let mut err = feature_err(
3011                         &tcx.sess.parse_sess,
3012                         sym::target_feature_11,
3013                         attr.span,
3014                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
3015                     );
3016                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
3017                     err.emit();
3018                 } else if let Some(local_id) = id.as_local() {
3019                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
3020                 }
3021             }
3022             from_target_feature(
3023                 tcx,
3024                 id,
3025                 attr,
3026                 supported_target_features,
3027                 &mut codegen_fn_attrs.target_features,
3028             );
3029         } else if attr.has_name(sym::linkage) {
3030             if let Some(val) = attr.value_str() {
3031                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
3032             }
3033         } else if attr.has_name(sym::link_section) {
3034             if let Some(val) = attr.value_str() {
3035                 if val.as_str().bytes().any(|b| b == 0) {
3036                     let msg = format!(
3037                         "illegal null byte in link_section \
3038                          value: `{}`",
3039                         &val
3040                     );
3041                     tcx.sess.span_err(attr.span, &msg);
3042                 } else {
3043                     codegen_fn_attrs.link_section = Some(val);
3044                 }
3045             }
3046         } else if attr.has_name(sym::link_name) {
3047             codegen_fn_attrs.link_name = attr.value_str();
3048         } else if attr.has_name(sym::link_ordinal) {
3049             link_ordinal_span = Some(attr.span);
3050             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
3051                 codegen_fn_attrs.link_ordinal = ordinal;
3052             }
3053         } else if attr.has_name(sym::no_sanitize) {
3054             no_sanitize_span = Some(attr.span);
3055             if let Some(list) = attr.meta_item_list() {
3056                 for item in list.iter() {
3057                     if item.has_name(sym::address) {
3058                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
3059                     } else if item.has_name(sym::cfi) {
3060                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
3061                     } else if item.has_name(sym::memory) {
3062                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
3063                     } else if item.has_name(sym::memtag) {
3064                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
3065                     } else if item.has_name(sym::thread) {
3066                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
3067                     } else if item.has_name(sym::hwaddress) {
3068                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
3069                     } else {
3070                         tcx.sess
3071                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
3072                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
3073                             .emit();
3074                     }
3075                 }
3076             }
3077         } else if attr.has_name(sym::instruction_set) {
3078             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3079                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3080                     [NestedMetaItem::MetaItem(set)] => {
3081                         let segments =
3082                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3083                         match segments.as_slice() {
3084                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3085                                 if !tcx.sess.target.has_thumb_interworking {
3086                                     struct_span_err!(
3087                                         tcx.sess.diagnostic(),
3088                                         attr.span,
3089                                         E0779,
3090                                         "target does not support `#[instruction_set]`"
3091                                     )
3092                                     .emit();
3093                                     None
3094                                 } else if segments[1] == sym::a32 {
3095                                     Some(InstructionSetAttr::ArmA32)
3096                                 } else if segments[1] == sym::t32 {
3097                                     Some(InstructionSetAttr::ArmT32)
3098                                 } else {
3099                                     unreachable!()
3100                                 }
3101                             }
3102                             _ => {
3103                                 struct_span_err!(
3104                                     tcx.sess.diagnostic(),
3105                                     attr.span,
3106                                     E0779,
3107                                     "invalid instruction set specified",
3108                                 )
3109                                 .emit();
3110                                 None
3111                             }
3112                         }
3113                     }
3114                     [] => {
3115                         struct_span_err!(
3116                             tcx.sess.diagnostic(),
3117                             attr.span,
3118                             E0778,
3119                             "`#[instruction_set]` requires an argument"
3120                         )
3121                         .emit();
3122                         None
3123                     }
3124                     _ => {
3125                         struct_span_err!(
3126                             tcx.sess.diagnostic(),
3127                             attr.span,
3128                             E0779,
3129                             "cannot specify more than one instruction set"
3130                         )
3131                         .emit();
3132                         None
3133                     }
3134                 },
3135                 _ => {
3136                     struct_span_err!(
3137                         tcx.sess.diagnostic(),
3138                         attr.span,
3139                         E0778,
3140                         "must specify an instruction set"
3141                     )
3142                     .emit();
3143                     None
3144                 }
3145             };
3146         } else if attr.has_name(sym::repr) {
3147             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3148                 Some(items) => match items.as_slice() {
3149                     [item] => match item.name_value_literal() {
3150                         Some((sym::align, literal)) => {
3151                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3152
3153                             match alignment {
3154                                 Ok(align) => Some(align),
3155                                 Err(msg) => {
3156                                     struct_span_err!(
3157                                         tcx.sess.diagnostic(),
3158                                         attr.span,
3159                                         E0589,
3160                                         "invalid `repr(align)` attribute: {}",
3161                                         msg
3162                                     )
3163                                     .emit();
3164
3165                                     None
3166                                 }
3167                             }
3168                         }
3169                         _ => None,
3170                     },
3171                     [] => None,
3172                     _ => None,
3173                 },
3174                 None => None,
3175             };
3176         }
3177     }
3178
3179     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3180         if !attr.has_name(sym::inline) {
3181             return ia;
3182         }
3183         match attr.meta_kind() {
3184             Some(MetaItemKind::Word) => InlineAttr::Hint,
3185             Some(MetaItemKind::List(ref items)) => {
3186                 inline_span = Some(attr.span);
3187                 if items.len() != 1 {
3188                     struct_span_err!(
3189                         tcx.sess.diagnostic(),
3190                         attr.span,
3191                         E0534,
3192                         "expected one argument"
3193                     )
3194                     .emit();
3195                     InlineAttr::None
3196                 } else if list_contains_name(&items, sym::always) {
3197                     InlineAttr::Always
3198                 } else if list_contains_name(&items, sym::never) {
3199                     InlineAttr::Never
3200                 } else {
3201                     struct_span_err!(
3202                         tcx.sess.diagnostic(),
3203                         items[0].span(),
3204                         E0535,
3205                         "invalid argument"
3206                     )
3207                     .emit();
3208
3209                     InlineAttr::None
3210                 }
3211             }
3212             Some(MetaItemKind::NameValue(_)) => ia,
3213             None => ia,
3214         }
3215     });
3216
3217     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3218         if !attr.has_name(sym::optimize) {
3219             return ia;
3220         }
3221         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3222         match attr.meta_kind() {
3223             Some(MetaItemKind::Word) => {
3224                 err(attr.span, "expected one argument");
3225                 ia
3226             }
3227             Some(MetaItemKind::List(ref items)) => {
3228                 inline_span = Some(attr.span);
3229                 if items.len() != 1 {
3230                     err(attr.span, "expected one argument");
3231                     OptimizeAttr::None
3232                 } else if list_contains_name(&items, sym::size) {
3233                     OptimizeAttr::Size
3234                 } else if list_contains_name(&items, sym::speed) {
3235                     OptimizeAttr::Speed
3236                 } else {
3237                     err(items[0].span(), "invalid argument");
3238                     OptimizeAttr::None
3239                 }
3240             }
3241             Some(MetaItemKind::NameValue(_)) => ia,
3242             None => ia,
3243         }
3244     });
3245
3246     // #73631: closures inherit `#[target_feature]` annotations
3247     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3248         let owner_id = tcx.parent(id).expect("closure should have a parent");
3249         codegen_fn_attrs
3250             .target_features
3251             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3252     }
3253
3254     // If a function uses #[target_feature] it can't be inlined into general
3255     // purpose functions as they wouldn't have the right target features
3256     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3257     // respected.
3258     if !codegen_fn_attrs.target_features.is_empty() {
3259         if codegen_fn_attrs.inline == InlineAttr::Always {
3260             if let Some(span) = inline_span {
3261                 tcx.sess.span_err(
3262                     span,
3263                     "cannot use `#[inline(always)]` with \
3264                      `#[target_feature]`",
3265                 );
3266             }
3267         }
3268     }
3269
3270     if !codegen_fn_attrs.no_sanitize.is_empty() {
3271         if codegen_fn_attrs.inline == InlineAttr::Always {
3272             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3273                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3274                 tcx.struct_span_lint_hir(
3275                     lint::builtin::INLINE_NO_SANITIZE,
3276                     hir_id,
3277                     no_sanitize_span,
3278                     |lint| {
3279                         lint.build("`no_sanitize` will have no effect after inlining")
3280                             .span_note(inline_span, "inlining requested here")
3281                             .emit();
3282                     },
3283                 )
3284             }
3285         }
3286     }
3287
3288     // Weak lang items have the same semantics as "std internal" symbols in the
3289     // sense that they're preserved through all our LTO passes and only
3290     // strippable by the linker.
3291     //
3292     // Additionally weak lang items have predetermined symbol names.
3293     if tcx.is_weak_lang_item(id) {
3294         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3295     }
3296     if let Some(name) = weak_lang_items::link_name(attrs) {
3297         codegen_fn_attrs.export_name = Some(name);
3298         codegen_fn_attrs.link_name = Some(name);
3299     }
3300     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3301
3302     // Internal symbols to the standard library all have no_mangle semantics in
3303     // that they have defined symbol names present in the function name. This
3304     // also applies to weak symbols where they all have known symbol names.
3305     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3306         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3307     }
3308
3309     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3310     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3311     // intrinsic functions.
3312     if let Some(name) = &codegen_fn_attrs.link_name {
3313         if name.as_str().starts_with("llvm.") {
3314             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3315         }
3316     }
3317
3318     codegen_fn_attrs
3319 }
3320
3321 /// Computes the set of target features used in a function for the purposes of
3322 /// inline assembly.
3323 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, id: DefId) -> &'tcx FxHashSet<Symbol> {
3324     let mut target_features = tcx.sess.target_features.clone();
3325     let attrs = tcx.codegen_fn_attrs(id);
3326     target_features.extend(&attrs.target_features);
3327     match attrs.instruction_set {
3328         None => {}
3329         Some(InstructionSetAttr::ArmA32) => {
3330             target_features.remove(&sym::thumb_mode);
3331         }
3332         Some(InstructionSetAttr::ArmT32) => {
3333             target_features.insert(sym::thumb_mode);
3334         }
3335     }
3336     tcx.arena.alloc(target_features)
3337 }
3338
3339 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3340 /// applied to the method prototype.
3341 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3342     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3343         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3344         && let Some(trait_item) = impl_item.trait_item_def_id
3345     {
3346         return tcx
3347             .codegen_fn_attrs(trait_item)
3348             .flags
3349             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3350     }
3351
3352     false
3353 }
3354
3355 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3356     use rustc_ast::{Lit, LitIntType, LitKind};
3357     let meta_item_list = attr.meta_item_list();
3358     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3359     let sole_meta_list = match meta_item_list {
3360         Some([item]) => item.literal(),
3361         Some(_) => {
3362             tcx.sess
3363                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3364                 .note("the attribute requires exactly one argument")
3365                 .emit();
3366             return None;
3367         }
3368         _ => None,
3369     };
3370     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3371         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3372         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3373         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3374         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3375         //
3376         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3377         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3378         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3379         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3380         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3381         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3382         // about LINK.EXE failing.)
3383         if *ordinal <= u16::MAX as u128 {
3384             Some(*ordinal as u16)
3385         } else {
3386             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3387             tcx.sess
3388                 .struct_span_err(attr.span, &msg)
3389                 .note("the value may not exceed `u16::MAX`")
3390                 .emit();
3391             None
3392         }
3393     } else {
3394         tcx.sess
3395             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3396             .note("an unsuffixed integer value, e.g., `1`, is expected")
3397             .emit();
3398         None
3399     }
3400 }
3401
3402 fn check_link_name_xor_ordinal(
3403     tcx: TyCtxt<'_>,
3404     codegen_fn_attrs: &CodegenFnAttrs,
3405     inline_span: Option<Span>,
3406 ) {
3407     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3408         return;
3409     }
3410     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3411     if let Some(span) = inline_span {
3412         tcx.sess.span_err(span, msg);
3413     } else {
3414         tcx.sess.err(msg);
3415     }
3416 }
3417
3418 /// Checks the function annotated with `#[target_feature]` is not a safe
3419 /// trait method implementation, reporting an error if it is.
3420 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3421     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3422     let node = tcx.hir().get(hir_id);
3423     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3424         let parent_id = tcx.hir().get_parent_item(hir_id);
3425         let parent_item = tcx.hir().expect_item(parent_id);
3426         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3427             tcx.sess
3428                 .struct_span_err(
3429                     attr_span,
3430                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3431                 )
3432                 .span_label(attr_span, "cannot be applied to safe trait method")
3433                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3434                 .emit();
3435         }
3436     }
3437 }