compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind};
  31 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::nested_filter;
  36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  37 use rustc_middle::mir::mono::Linkage;
  38 use rustc_middle::ty::query::Providers;
  39 use rustc_middle::ty::subst::InternalSubsts;
  40 use rustc_middle::ty::util::Discr;
  41 use rustc_middle::ty::util::IntTypeExt;
  42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  43 use rustc_middle::ty::{ReprOptions, ToPredicate};
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50 use std::iter;
  51
  52 mod item_bounds;
  53 mod type_of;
  54
  55 struct OnlySelfBounds(bool);
  56
  57 ///////////////////////////////////////////////////////////////////////////
  58 // Main entry point
  59
  60 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  61     tcx.hir().visit_item_likes_in_module(
  62         module_def_id,
  63         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  64     );
  65 }
  66
  67 pub fn provide(providers: &mut Providers) {
  68     *providers = Providers {
  69         opt_const_param_of: type_of::opt_const_param_of,
  70         type_of: type_of::type_of,
  71         item_bounds: item_bounds::item_bounds,
  72         explicit_item_bounds: item_bounds::explicit_item_bounds,
  73         generics_of,
  74         predicates_of,
  75         predicates_defined_on,
  76         explicit_predicates_of,
  77         super_predicates_of,
  78         super_predicates_that_define_assoc_type,
  79         trait_explicit_predicates_and_bounds,
  80         type_param_predicates,
  81         trait_def,
  82         adt_def,
  83         fn_sig,
  84         impl_trait_ref,
  85         impl_polarity,
  86         is_foreign_item,
  87         generator_kind,
  88         codegen_fn_attrs,
  89         asm_target_features,
  90         collect_mod_item_types,
  91         should_inherit_track_caller,
  92         ..*providers
  93     };
  94 }
  95
  96 ///////////////////////////////////////////////////////////////////////////
  97
  98 /// Context specific to some particular item. This is what implements
  99 /// `AstConv`. It has information about the predicates that are defined
 100 /// on the trait. Unfortunately, this predicate information is
 101 /// available in various different forms at various points in the
 102 /// process. So we can't just store a pointer to e.g., the AST or the
 103 /// parsed ty form, we have to be more flexible. To this end, the
 104 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 105 /// `get_type_parameter_bounds` requests, drawing the information from
 106 /// the AST (`hir::Generics`), recursively.
 107 pub struct ItemCtxt<'tcx> {
 108     tcx: TyCtxt<'tcx>,
 109     item_def_id: DefId,
 110 }
 111
 112 ///////////////////////////////////////////////////////////////////////////
 113
 114 #[derive(Default)]
 115 crate struct HirPlaceholderCollector(crate Vec<Span>);
 116
 117 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 118     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 119         if let hir::TyKind::Infer = t.kind {
 120             self.0.push(t.span);
 121         }
 122         intravisit::walk_ty(self, t)
 123     }
 124     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 125         match generic_arg {
 126             hir::GenericArg::Infer(inf) => {
 127                 self.0.push(inf.span);
 128                 intravisit::walk_inf(self, inf);
 129             }
 130             hir::GenericArg::Type(t) => self.visit_ty(t),
 131             _ => {}
 132         }
 133     }
 134     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 135         if let &hir::ArrayLen::Infer(_, span) = length {
 136             self.0.push(span);
 137         }
 138         intravisit::walk_array_len(self, length)
 139     }
 140 }
 141
 142 struct CollectItemTypesVisitor<'tcx> {
 143     tcx: TyCtxt<'tcx>,
 144 }
 145
 146 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 147 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 148 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 149 crate fn placeholder_type_error<'tcx>(
 150     tcx: TyCtxt<'tcx>,
 151     generics: Option<&hir::Generics<'_>>,
 152     placeholder_types: Vec<Span>,
 153     suggest: bool,
 154     hir_ty: Option<&hir::Ty<'_>>,
 155     kind: &'static str,
 156 ) {
 157     if placeholder_types.is_empty() {
 158         return;
 159     }
 160
 161     placeholder_type_error_diag(tcx, generics, placeholder_types, vec![], suggest, hir_ty, kind)
 162         .emit();
 163 }
 164
 165 crate fn placeholder_type_error_diag<'tcx>(
 166     tcx: TyCtxt<'tcx>,
 167     generics: Option<&hir::Generics<'_>>,
 168     placeholder_types: Vec<Span>,
 169     additional_spans: Vec<Span>,
 170     suggest: bool,
 171     hir_ty: Option<&hir::Ty<'_>>,
 172     kind: &'static str,
 173 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 174     if placeholder_types.is_empty() {
 175         return bad_placeholder(tcx, additional_spans, kind);
 176     }
 177
 178     let params = generics.map(|g| g.params).unwrap_or_default();
 179     let type_name = params.next_type_param_name(None);
 180     let mut sugg: Vec<_> =
 181         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 182
 183     if let Some(generics) = generics {
 184         if let Some(arg) = params.iter().find(|arg| {
 185             matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. }))
 186         }) {
 187             // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 188             // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 189             sugg.push((arg.span, (*type_name).to_string()));
 190         } else if let Some(span) = generics.span_for_param_suggestion() {
 191             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 192             sugg.push((span, format!(", {}", type_name)));
 193         } else {
 194             sugg.push((generics.span, format!("<{}>", type_name)));
 195         }
 196     }
 197
 198     let mut err =
 199         bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
 200
 201     // Suggest, but only if it is not a function in const or static
 202     if suggest {
 203         let mut is_fn = false;
 204         let mut is_const_or_static = false;
 205
 206         if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
 207             is_fn = true;
 208
 209             // Check if parent is const or static
 210             let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 211             let parent_node = tcx.hir().get(parent_id);
 212
 213             is_const_or_static = matches!(
 214                 parent_node,
 215                 Node::Item(&hir::Item {
 216                     kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 217                     ..
 218                 }) | Node::TraitItem(&hir::TraitItem {
 219                     kind: hir::TraitItemKind::Const(..),
 220                     ..
 221                 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 222             );
 223         }
 224
 225         // if function is wrapped around a const or static,
 226         // then don't show the suggestion
 227         if !(is_fn && is_const_or_static) {
 228             err.multipart_suggestion(
 229                 "use type parameters instead",
 230                 sugg,
 231                 Applicability::HasPlaceholders,
 232             );
 233         }
 234     }
 235
 236     err
 237 }
 238
 239 fn reject_placeholder_type_signatures_in_item<'tcx>(
 240     tcx: TyCtxt<'tcx>,
 241     item: &'tcx hir::Item<'tcx>,
 242 ) {
 243     let (generics, suggest) = match &item.kind {
 244         hir::ItemKind::Union(_, generics)
 245         | hir::ItemKind::Enum(_, generics)
 246         | hir::ItemKind::TraitAlias(generics, _)
 247         | hir::ItemKind::Trait(_, _, generics, ..)
 248         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 249         | hir::ItemKind::Struct(_, generics) => (generics, true),
 250         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 251         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 252         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 253         _ => return,
 254     };
 255
 256     let mut visitor = HirPlaceholderCollector::default();
 257     visitor.visit_item(item);
 258
 259     placeholder_type_error(tcx, Some(generics), visitor.0, suggest, None, item.kind.descr());
 260 }
 261
 262 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 263     type NestedFilter = nested_filter::OnlyBodies;
 264
 265     fn nested_visit_map(&mut self) -> Self::Map {
 266         self.tcx.hir()
 267     }
 268
 269     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 270         convert_item(self.tcx, item.item_id());
 271         reject_placeholder_type_signatures_in_item(self.tcx, item);
 272         intravisit::walk_item(self, item);
 273     }
 274
 275     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 276         for param in generics.params {
 277             match param.kind {
 278                 hir::GenericParamKind::Lifetime { .. } => {}
 279                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 280                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 281                     self.tcx.ensure().type_of(def_id);
 282                 }
 283                 hir::GenericParamKind::Type { .. } => {}
 284                 hir::GenericParamKind::Const { default, .. } => {
 285                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 286                     self.tcx.ensure().type_of(def_id);
 287                     if let Some(default) = default {
 288                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 289                         // need to store default and type of default
 290                         self.tcx.ensure().type_of(default_def_id);
 291                         self.tcx.ensure().const_param_default(def_id);
 292                     }
 293                 }
 294             }
 295         }
 296         intravisit::walk_generics(self, generics);
 297     }
 298
 299     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 300         if let hir::ExprKind::Closure(..) = expr.kind {
 301             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 302             self.tcx.ensure().generics_of(def_id);
 303             // We do not call `type_of` for closures here as that
 304             // depends on typecheck and would therefore hide
 305             // any further errors in case one typeck fails.
 306         }
 307         intravisit::walk_expr(self, expr);
 308     }
 309
 310     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 311         convert_trait_item(self.tcx, trait_item.trait_item_id());
 312         intravisit::walk_trait_item(self, trait_item);
 313     }
 314
 315     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 316         convert_impl_item(self.tcx, impl_item.impl_item_id());
 317         intravisit::walk_impl_item(self, impl_item);
 318     }
 319 }
 320
 321 ///////////////////////////////////////////////////////////////////////////
 322 // Utility types and common code for the above passes.
 323
 324 fn bad_placeholder<'tcx>(
 325     tcx: TyCtxt<'tcx>,
 326     mut spans: Vec<Span>,
 327     kind: &'static str,
 328 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 329     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 330
 331     spans.sort();
 332     let mut err = struct_span_err!(
 333         tcx.sess,
 334         spans.clone(),
 335         E0121,
 336         "the placeholder `_` is not allowed within types on item signatures for {}",
 337         kind
 338     );
 339     for span in spans {
 340         err.span_label(span, "not allowed in type signatures");
 341     }
 342     err
 343 }
 344
 345 impl<'tcx> ItemCtxt<'tcx> {
 346     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 347         ItemCtxt { tcx, item_def_id }
 348     }
 349
 350     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 351         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 352     }
 353
 354     pub fn hir_id(&self) -> hir::HirId {
 355         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 356     }
 357
 358     pub fn node(&self) -> hir::Node<'tcx> {
 359         self.tcx.hir().get(self.hir_id())
 360     }
 361 }
 362
 363 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 364     fn tcx(&self) -> TyCtxt<'tcx> {
 365         self.tcx
 366     }
 367
 368     fn item_def_id(&self) -> Option<DefId> {
 369         Some(self.item_def_id)
 370     }
 371
 372     fn get_type_parameter_bounds(
 373         &self,
 374         span: Span,
 375         def_id: DefId,
 376         assoc_name: Ident,
 377     ) -> ty::GenericPredicates<'tcx> {
 378         self.tcx.at(span).type_param_predicates((
 379             self.item_def_id,
 380             def_id.expect_local(),
 381             assoc_name,
 382         ))
 383     }
 384
 385     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 386         None
 387     }
 388
 389     fn allow_ty_infer(&self) -> bool {
 390         false
 391     }
 392
 393     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 394         self.tcx().ty_error_with_message(span, "bad placeholder type")
 395     }
 396
 397     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 398         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
 399             ty::ReErased => self.tcx.lifetimes.re_static,
 400             _ => r,
 401         });
 402         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 403     }
 404
 405     fn projected_ty_from_poly_trait_ref(
 406         &self,
 407         span: Span,
 408         item_def_id: DefId,
 409         item_segment: &hir::PathSegment<'_>,
 410         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 411     ) -> Ty<'tcx> {
 412         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 413             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 414                 self,
 415                 self.tcx,
 416                 span,
 417                 item_def_id,
 418                 item_segment,
 419                 trait_ref.substs,
 420             );
 421             self.tcx().mk_projection(item_def_id, item_substs)
 422         } else {
 423             // There are no late-bound regions; we can just ignore the binder.
 424             let mut err = struct_span_err!(
 425                 self.tcx().sess,
 426                 span,
 427                 E0212,
 428                 "cannot use the associated type of a trait \
 429                  with uninferred generic parameters"
 430             );
 431
 432             match self.node() {
 433                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 434                     let item =
 435                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 436                     match &item.kind {
 437                         hir::ItemKind::Enum(_, generics)
 438                         | hir::ItemKind::Struct(_, generics)
 439                         | hir::ItemKind::Union(_, generics) => {
 440                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 441                             let (lt_sp, sugg) = match generics.params {
 442                                 [] => (generics.span, format!("<{}>", lt_name)),
 443                                 [bound, ..] => {
 444                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 445                                 }
 446                             };
 447                             let suggestions = vec![
 448                                 (lt_sp, sugg),
 449                                 (
 450                                     span.with_hi(item_segment.ident.span.lo()),
 451                                     format!(
 452                                         "{}::",
 453                                         // Replace the existing lifetimes with a new named lifetime.
 454                                         self.tcx
 455                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 456                                                 self.tcx.mk_region(ty::ReEarlyBound(
 457                                                     ty::EarlyBoundRegion {
 458                                                         def_id: item_def_id,
 459                                                         index: 0,
 460                                                         name: Symbol::intern(&lt_name),
 461                                                     },
 462                                                 ))
 463                                             })
 464                                             .0,
 465                                     ),
 466                                 ),
 467                             ];
 468                             err.multipart_suggestion(
 469                                 "use a fully qualified path with explicit lifetimes",
 470                                 suggestions,
 471                                 Applicability::MaybeIncorrect,
 472                             );
 473                         }
 474                         _ => {}
 475                     }
 476                 }
 477                 hir::Node::Item(hir::Item {
 478                     kind:
 479                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 480                     ..
 481                 }) => {}
 482                 hir::Node::Item(_)
 483                 | hir::Node::ForeignItem(_)
 484                 | hir::Node::TraitItem(_)
 485                 | hir::Node::ImplItem(_) => {
 486                     err.span_suggestion_verbose(
 487                         span.with_hi(item_segment.ident.span.lo()),
 488                         "use a fully qualified path with inferred lifetimes",
 489                         format!(
 490                             "{}::",
 491                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 492                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 493                         ),
 494                         Applicability::MaybeIncorrect,
 495                     );
 496                 }
 497                 _ => {}
 498             }
 499             err.emit();
 500             self.tcx().ty_error()
 501         }
 502     }
 503
 504     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 505         // Types in item signatures are not normalized to avoid undue dependencies.
 506         ty
 507     }
 508
 509     fn set_tainted_by_errors(&self) {
 510         // There's no obvious place to track this, so just let it go.
 511     }
 512
 513     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 514         // There's no place to record types from signatures?
 515     }
 516 }
 517
 518 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 519 fn get_new_lifetime_name<'tcx>(
 520     tcx: TyCtxt<'tcx>,
 521     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 522     generics: &hir::Generics<'tcx>,
 523 ) -> String {
 524     let existing_lifetimes = tcx
 525         .collect_referenced_late_bound_regions(&poly_trait_ref)
 526         .into_iter()
 527         .filter_map(|lt| {
 528             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 529                 Some(name.as_str().to_string())
 530             } else {
 531                 None
 532             }
 533         })
 534         .chain(generics.params.iter().filter_map(|param| {
 535             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 536                 Some(param.name.ident().as_str().to_string())
 537             } else {
 538                 None
 539             }
 540         }))
 541         .collect::<FxHashSet<String>>();
 542
 543     let a_to_z_repeat_n = |n| {
 544         (b'a'..=b'z').map(move |c| {
 545             let mut s = '\''.to_string();
 546             s.extend(std::iter::repeat(char::from(c)).take(n));
 547             s
 548         })
 549     };
 550
 551     // If all single char lifetime names are present, we wrap around and double the chars.
 552     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 553 }
 554
 555 /// Returns the predicates defined on `item_def_id` of the form
 556 /// `X: Foo` where `X` is the type parameter `def_id`.
 557 fn type_param_predicates(
 558     tcx: TyCtxt<'_>,
 559     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 560 ) -> ty::GenericPredicates<'_> {
 561     use rustc_hir::*;
 562
 563     // In the AST, bounds can derive from two places. Either
 564     // written inline like `<T: Foo>` or in a where-clause like
 565     // `where T: Foo`.
 566
 567     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 568     let param_owner = tcx.hir().ty_param_owner(def_id);
 569     let generics = tcx.generics_of(param_owner);
 570     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 571     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 572
 573     // Don't look for bounds where the type parameter isn't in scope.
 574     let parent = if item_def_id == param_owner.to_def_id() {
 575         None
 576     } else {
 577         tcx.generics_of(item_def_id).parent
 578     };
 579
 580     let mut result = parent
 581         .map(|parent| {
 582             let icx = ItemCtxt::new(tcx, parent);
 583             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 584         })
 585         .unwrap_or_default();
 586     let mut extend = None;
 587
 588     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 589     let ast_generics = match tcx.hir().get(item_hir_id) {
 590         Node::TraitItem(item) => &item.generics,
 591
 592         Node::ImplItem(item) => &item.generics,
 593
 594         Node::Item(item) => {
 595             match item.kind {
 596                 ItemKind::Fn(.., ref generics, _)
 597                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 598                 | ItemKind::TyAlias(_, ref generics)
 599                 | ItemKind::OpaqueTy(OpaqueTy {
 600                     ref generics,
 601                     origin: hir::OpaqueTyOrigin::TyAlias,
 602                     ..
 603                 })
 604                 | ItemKind::Enum(_, ref generics)
 605                 | ItemKind::Struct(_, ref generics)
 606                 | ItemKind::Union(_, ref generics) => generics,
 607                 ItemKind::Trait(_, _, ref generics, ..) => {
 608                     // Implied `Self: Trait` and supertrait bounds.
 609                     if param_id == item_hir_id {
 610                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 611                         extend =
 612                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 613                     }
 614                     generics
 615                 }
 616                 _ => return result,
 617             }
 618         }
 619
 620         Node::ForeignItem(item) => match item.kind {
 621             ForeignItemKind::Fn(_, _, ref generics) => generics,
 622             _ => return result,
 623         },
 624
 625         _ => return result,
 626     };
 627
 628     let icx = ItemCtxt::new(tcx, item_def_id);
 629     let extra_predicates = extend.into_iter().chain(
 630         icx.type_parameter_bounds_in_generics(
 631             ast_generics,
 632             param_id,
 633             ty,
 634             OnlySelfBounds(true),
 635             Some(assoc_name),
 636         )
 637         .into_iter()
 638         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 639             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 640             _ => false,
 641         }),
 642     );
 643     result.predicates =
 644         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 645     result
 646 }
 647
 648 impl<'tcx> ItemCtxt<'tcx> {
 649     /// Finds bounds from `hir::Generics`. This requires scanning through the
 650     /// AST. We do this to avoid having to convert *all* the bounds, which
 651     /// would create artificial cycles. Instead, we can only convert the
 652     /// bounds for a type parameter `X` if `X::Foo` is used.
 653     fn type_parameter_bounds_in_generics(
 654         &self,
 655         ast_generics: &'tcx hir::Generics<'tcx>,
 656         param_id: hir::HirId,
 657         ty: Ty<'tcx>,
 658         only_self_bounds: OnlySelfBounds,
 659         assoc_name: Option<Ident>,
 660     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 661         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 662         ast_generics
 663             .predicates
 664             .iter()
 665             .filter_map(|wp| match *wp {
 666                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 667                 _ => None,
 668             })
 669             .flat_map(|bp| {
 670                 let bt = if bp.is_param_bound(param_def_id) {
 671                     Some(ty)
 672                 } else if !only_self_bounds.0 {
 673                     Some(self.to_ty(bp.bounded_ty))
 674                 } else {
 675                     None
 676                 };
 677                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 678
 679                 bp.bounds
 680                     .iter()
 681                     .filter(|b| match assoc_name {
 682                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 683                         None => true,
 684                     })
 685                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 686             })
 687             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars))
 688             .collect()
 689     }
 690
 691     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 692         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 693
 694         match b {
 695             hir::GenericBound::Trait(poly_trait_ref, _) => {
 696                 let trait_ref = &poly_trait_ref.trait_ref;
 697                 if let Some(trait_did) = trait_ref.trait_def_id() {
 698                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 699                 } else {
 700                     false
 701                 }
 702             }
 703             _ => false,
 704         }
 705     }
 706 }
 707
 708 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 709     let it = tcx.hir().item(item_id);
 710     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 711     let def_id = item_id.def_id;
 712
 713     match it.kind {
 714         // These don't define types.
 715         hir::ItemKind::ExternCrate(_)
 716         | hir::ItemKind::Use(..)
 717         | hir::ItemKind::Macro(..)
 718         | hir::ItemKind::Mod(_)
 719         | hir::ItemKind::GlobalAsm(_) => {}
 720         hir::ItemKind::ForeignMod { items, .. } => {
 721             for item in items {
 722                 let item = tcx.hir().foreign_item(item.id);
 723                 tcx.ensure().generics_of(item.def_id);
 724                 tcx.ensure().type_of(item.def_id);
 725                 tcx.ensure().predicates_of(item.def_id);
 726                 match item.kind {
 727                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 728                     hir::ForeignItemKind::Static(..) => {
 729                         let mut visitor = HirPlaceholderCollector::default();
 730                         visitor.visit_foreign_item(item);
 731                         placeholder_type_error(
 732                             tcx,
 733                             None,
 734                             visitor.0,
 735                             false,
 736                             None,
 737                             "static variable",
 738                         );
 739                     }
 740                     _ => (),
 741                 }
 742             }
 743         }
 744         hir::ItemKind::Enum(ref enum_definition, _) => {
 745             tcx.ensure().generics_of(def_id);
 746             tcx.ensure().type_of(def_id);
 747             tcx.ensure().predicates_of(def_id);
 748             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 749         }
 750         hir::ItemKind::Impl { .. } => {
 751             tcx.ensure().generics_of(def_id);
 752             tcx.ensure().type_of(def_id);
 753             tcx.ensure().impl_trait_ref(def_id);
 754             tcx.ensure().predicates_of(def_id);
 755         }
 756         hir::ItemKind::Trait(..) => {
 757             tcx.ensure().generics_of(def_id);
 758             tcx.ensure().trait_def(def_id);
 759             tcx.at(it.span).super_predicates_of(def_id);
 760             tcx.ensure().predicates_of(def_id);
 761         }
 762         hir::ItemKind::TraitAlias(..) => {
 763             tcx.ensure().generics_of(def_id);
 764             tcx.at(it.span).super_predicates_of(def_id);
 765             tcx.ensure().predicates_of(def_id);
 766         }
 767         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 768             tcx.ensure().generics_of(def_id);
 769             tcx.ensure().type_of(def_id);
 770             tcx.ensure().predicates_of(def_id);
 771
 772             for f in struct_def.fields() {
 773                 let def_id = tcx.hir().local_def_id(f.hir_id);
 774                 tcx.ensure().generics_of(def_id);
 775                 tcx.ensure().type_of(def_id);
 776                 tcx.ensure().predicates_of(def_id);
 777             }
 778
 779             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 780                 convert_variant_ctor(tcx, ctor_hir_id);
 781             }
 782         }
 783
 784         // Desugared from `impl Trait`, so visited by the function's return type.
 785         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 786             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 787             ..
 788         }) => {}
 789
 790         // Don't call `type_of` on opaque types, since that depends on type
 791         // checking function bodies. `check_item_type` ensures that it's called
 792         // instead.
 793         hir::ItemKind::OpaqueTy(..) => {
 794             tcx.ensure().generics_of(def_id);
 795             tcx.ensure().predicates_of(def_id);
 796             tcx.ensure().explicit_item_bounds(def_id);
 797         }
 798         hir::ItemKind::TyAlias(..)
 799         | hir::ItemKind::Static(..)
 800         | hir::ItemKind::Const(..)
 801         | hir::ItemKind::Fn(..) => {
 802             tcx.ensure().generics_of(def_id);
 803             tcx.ensure().type_of(def_id);
 804             tcx.ensure().predicates_of(def_id);
 805             match it.kind {
 806                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 807                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 808                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 809                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 810                     if let hir::TyKind::TraitObject(..) = ty.kind {
 811                         let mut visitor = HirPlaceholderCollector::default();
 812                         visitor.visit_item(it);
 813                         placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr());
 814                     }
 815                 }
 816                 _ => (),
 817             }
 818         }
 819     }
 820 }
 821
 822 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 823     let trait_item = tcx.hir().trait_item(trait_item_id);
 824     tcx.ensure().generics_of(trait_item_id.def_id);
 825
 826     match trait_item.kind {
 827         hir::TraitItemKind::Fn(..) => {
 828             tcx.ensure().type_of(trait_item_id.def_id);
 829             tcx.ensure().fn_sig(trait_item_id.def_id);
 830         }
 831
 832         hir::TraitItemKind::Const(.., Some(_)) => {
 833             tcx.ensure().type_of(trait_item_id.def_id);
 834         }
 835
 836         hir::TraitItemKind::Const(..) => {
 837             tcx.ensure().type_of(trait_item_id.def_id);
 838             // Account for `const C: _;`.
 839             let mut visitor = HirPlaceholderCollector::default();
 840             visitor.visit_trait_item(trait_item);
 841             placeholder_type_error(tcx, None, visitor.0, false, None, "constant");
 842         }
 843
 844         hir::TraitItemKind::Type(_, Some(_)) => {
 845             tcx.ensure().item_bounds(trait_item_id.def_id);
 846             tcx.ensure().type_of(trait_item_id.def_id);
 847             // Account for `type T = _;`.
 848             let mut visitor = HirPlaceholderCollector::default();
 849             visitor.visit_trait_item(trait_item);
 850             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 851         }
 852
 853         hir::TraitItemKind::Type(_, None) => {
 854             tcx.ensure().item_bounds(trait_item_id.def_id);
 855             // #74612: Visit and try to find bad placeholders
 856             // even if there is no concrete type.
 857             let mut visitor = HirPlaceholderCollector::default();
 858             visitor.visit_trait_item(trait_item);
 859
 860             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 861         }
 862     };
 863
 864     tcx.ensure().predicates_of(trait_item_id.def_id);
 865 }
 866
 867 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 868     let def_id = impl_item_id.def_id;
 869     tcx.ensure().generics_of(def_id);
 870     tcx.ensure().type_of(def_id);
 871     tcx.ensure().predicates_of(def_id);
 872     let impl_item = tcx.hir().impl_item(impl_item_id);
 873     match impl_item.kind {
 874         hir::ImplItemKind::Fn(..) => {
 875             tcx.ensure().fn_sig(def_id);
 876         }
 877         hir::ImplItemKind::TyAlias(_) => {
 878             // Account for `type T = _;`
 879             let mut visitor = HirPlaceholderCollector::default();
 880             visitor.visit_impl_item(impl_item);
 881
 882             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 883         }
 884         hir::ImplItemKind::Const(..) => {}
 885     }
 886 }
 887
 888 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 889     let def_id = tcx.hir().local_def_id(ctor_id);
 890     tcx.ensure().generics_of(def_id);
 891     tcx.ensure().type_of(def_id);
 892     tcx.ensure().predicates_of(def_id);
 893 }
 894
 895 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 896     let def = tcx.adt_def(def_id);
 897     let repr_type = def.repr().discr_type();
 898     let initial = repr_type.initial_discriminant(tcx);
 899     let mut prev_discr = None::<Discr<'_>>;
 900
 901     // fill the discriminant values and field types
 902     for variant in variants {
 903         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 904         prev_discr = Some(
 905             if let Some(ref e) = variant.disr_expr {
 906                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 907                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 908             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 909                 Some(discr)
 910             } else {
 911                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 912                     .span_label(
 913                         variant.span,
 914                         format!("overflowed on value after {}", prev_discr.unwrap()),
 915                     )
 916                     .note(&format!(
 917                         "explicitly set `{} = {}` if that is desired outcome",
 918                         variant.ident, wrapped_discr
 919                     ))
 920                     .emit();
 921                 None
 922             }
 923             .unwrap_or(wrapped_discr),
 924         );
 925
 926         for f in variant.data.fields() {
 927             let def_id = tcx.hir().local_def_id(f.hir_id);
 928             tcx.ensure().generics_of(def_id);
 929             tcx.ensure().type_of(def_id);
 930             tcx.ensure().predicates_of(def_id);
 931         }
 932
 933         // Convert the ctor, if any. This also registers the variant as
 934         // an item.
 935         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 936             convert_variant_ctor(tcx, ctor_hir_id);
 937         }
 938     }
 939 }
 940
 941 fn convert_variant(
 942     tcx: TyCtxt<'_>,
 943     variant_did: Option<LocalDefId>,
 944     ctor_did: Option<LocalDefId>,
 945     ident: Ident,
 946     discr: ty::VariantDiscr,
 947     def: &hir::VariantData<'_>,
 948     adt_kind: ty::AdtKind,
 949     parent_did: LocalDefId,
 950 ) -> ty::VariantDef {
 951     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 952     let fields = def
 953         .fields()
 954         .iter()
 955         .map(|f| {
 956             let fid = tcx.hir().local_def_id(f.hir_id);
 957             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 958             if let Some(prev_span) = dup_span {
 959                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 960                     field_name: f.ident,
 961                     span: f.span,
 962                     prev_span,
 963                 });
 964             } else {
 965                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 966             }
 967
 968             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 969         })
 970         .collect();
 971     let recovered = match def {
 972         hir::VariantData::Struct(_, r) => *r,
 973         _ => false,
 974     };
 975     ty::VariantDef::new(
 976         ident.name,
 977         variant_did.map(LocalDefId::to_def_id),
 978         ctor_did.map(LocalDefId::to_def_id),
 979         discr,
 980         fields,
 981         CtorKind::from_hir(def),
 982         adt_kind,
 983         parent_did.to_def_id(),
 984         recovered,
 985         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
 986             || variant_did.map_or(false, |variant_did| {
 987                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
 988             }),
 989     )
 990 }
 991
 992 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
 993     use rustc_hir::*;
 994
 995     let def_id = def_id.expect_local();
 996     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
 997     let Node::Item(item) = tcx.hir().get(hir_id) else {
 998         bug!();
 999     };
1000
1001     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1002     let (kind, variants) = match item.kind {
1003         ItemKind::Enum(ref def, _) => {
1004             let mut distance_from_explicit = 0;
1005             let variants = def
1006                 .variants
1007                 .iter()
1008                 .map(|v| {
1009                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1010                     let ctor_did =
1011                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1012
1013                     let discr = if let Some(ref e) = v.disr_expr {
1014                         distance_from_explicit = 0;
1015                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1016                     } else {
1017                         ty::VariantDiscr::Relative(distance_from_explicit)
1018                     };
1019                     distance_from_explicit += 1;
1020
1021                     convert_variant(
1022                         tcx,
1023                         variant_did,
1024                         ctor_did,
1025                         v.ident,
1026                         discr,
1027                         &v.data,
1028                         AdtKind::Enum,
1029                         def_id,
1030                     )
1031                 })
1032                 .collect();
1033
1034             (AdtKind::Enum, variants)
1035         }
1036         ItemKind::Struct(ref def, _) => {
1037             let variant_did = None::<LocalDefId>;
1038             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1039
1040             let variants = std::iter::once(convert_variant(
1041                 tcx,
1042                 variant_did,
1043                 ctor_did,
1044                 item.ident,
1045                 ty::VariantDiscr::Relative(0),
1046                 def,
1047                 AdtKind::Struct,
1048                 def_id,
1049             ))
1050             .collect();
1051
1052             (AdtKind::Struct, variants)
1053         }
1054         ItemKind::Union(ref def, _) => {
1055             let variant_did = None;
1056             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1057
1058             let variants = std::iter::once(convert_variant(
1059                 tcx,
1060                 variant_did,
1061                 ctor_did,
1062                 item.ident,
1063                 ty::VariantDiscr::Relative(0),
1064                 def,
1065                 AdtKind::Union,
1066                 def_id,
1067             ))
1068             .collect();
1069
1070             (AdtKind::Union, variants)
1071         }
1072         _ => bug!(),
1073     };
1074     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1075 }
1076
1077 /// Ensures that the super-predicates of the trait with a `DefId`
1078 /// of `trait_def_id` are converted and stored. This also ensures that
1079 /// the transitive super-predicates are converted.
1080 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1081     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1082     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1083 }
1084
1085 /// Ensures that the super-predicates of the trait with a `DefId`
1086 /// of `trait_def_id` are converted and stored. This also ensures that
1087 /// the transitive super-predicates are converted.
1088 fn super_predicates_that_define_assoc_type(
1089     tcx: TyCtxt<'_>,
1090     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1091 ) -> ty::GenericPredicates<'_> {
1092     debug!(
1093         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1094         trait_def_id, assoc_name
1095     );
1096     if trait_def_id.is_local() {
1097         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1098         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1099
1100         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1101             bug!("trait_node_id {} is not an item", trait_hir_id);
1102         };
1103
1104         let (generics, bounds) = match item.kind {
1105             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1106             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1107             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1108         };
1109
1110         let icx = ItemCtxt::new(tcx, trait_def_id);
1111
1112         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1113         let self_param_ty = tcx.types.self_param;
1114         let superbounds1 = if let Some(assoc_name) = assoc_name {
1115             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1116                 &icx,
1117                 self_param_ty,
1118                 bounds,
1119                 assoc_name,
1120             )
1121         } else {
1122             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1123         };
1124
1125         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1126
1127         // Convert any explicit superbounds in the where-clause,
1128         // e.g., `trait Foo where Self: Bar`.
1129         // In the case of trait aliases, however, we include all bounds in the where-clause,
1130         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1131         // as one of its "superpredicates".
1132         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1133         let superbounds2 = icx.type_parameter_bounds_in_generics(
1134             generics,
1135             item.hir_id(),
1136             self_param_ty,
1137             OnlySelfBounds(!is_trait_alias),
1138             assoc_name,
1139         );
1140
1141         // Combine the two lists to form the complete set of superbounds:
1142         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1143
1144         // Now require that immediate supertraits are converted,
1145         // which will, in turn, reach indirect supertraits.
1146         if assoc_name.is_none() {
1147             // Now require that immediate supertraits are converted,
1148             // which will, in turn, reach indirect supertraits.
1149             for &(pred, span) in superbounds {
1150                 debug!("superbound: {:?}", pred);
1151                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1152                     tcx.at(span).super_predicates_of(bound.def_id());
1153                 }
1154             }
1155         }
1156
1157         ty::GenericPredicates { parent: None, predicates: superbounds }
1158     } else {
1159         // if `assoc_name` is None, then the query should've been redirected to an
1160         // external provider
1161         assert!(assoc_name.is_some());
1162         tcx.super_predicates_of(trait_def_id)
1163     }
1164 }
1165
1166 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1167     let item = tcx.hir().expect_item(def_id.expect_local());
1168
1169     let (is_auto, unsafety, items) = match item.kind {
1170         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1171             (is_auto == hir::IsAuto::Yes, unsafety, items)
1172         }
1173         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1174         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1175     };
1176
1177     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1178     if paren_sugar && !tcx.features().unboxed_closures {
1179         tcx.sess
1180             .struct_span_err(
1181                 item.span,
1182                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1183                  which traits can use parenthetical notation",
1184             )
1185             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1186             .emit();
1187     }
1188
1189     let is_marker = tcx.has_attr(def_id, sym::marker);
1190     let skip_array_during_method_dispatch =
1191         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1192     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1193         ty::trait_def::TraitSpecializationKind::Marker
1194     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1195         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1196     } else {
1197         ty::trait_def::TraitSpecializationKind::None
1198     };
1199     let must_implement_one_of = tcx
1200         .get_attrs(def_id)
1201         .iter()
1202         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1203         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1204         // and that they are all identifiers
1205         .and_then(|attr| match attr.meta_item_list() {
1206             Some(items) if items.len() < 2 => {
1207                 tcx.sess
1208                     .struct_span_err(
1209                         attr.span,
1210                         "the `#[rustc_must_implement_one_of]` attribute must be \
1211                         used with at least 2 args",
1212                     )
1213                     .emit();
1214
1215                 None
1216             }
1217             Some(items) => items
1218                 .into_iter()
1219                 .map(|item| item.ident().ok_or(item.span()))
1220                 .collect::<Result<Box<[_]>, _>>()
1221                 .map_err(|span| {
1222                     tcx.sess
1223                         .struct_span_err(span, "must be a name of an associated function")
1224                         .emit();
1225                 })
1226                 .ok()
1227                 .zip(Some(attr.span)),
1228             // Error is reported by `rustc_attr!`
1229             None => None,
1230         })
1231         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1232         // functions in the trait with default implementations
1233         .and_then(|(list, attr_span)| {
1234             let errors = list.iter().filter_map(|ident| {
1235                 let item = items.iter().find(|item| item.ident == *ident);
1236
1237                 match item {
1238                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1239                         if !item.defaultness.has_value() {
1240                             tcx.sess
1241                                 .struct_span_err(
1242                                     item.span,
1243                                     "This function doesn't have a default implementation",
1244                                 )
1245                                 .span_note(attr_span, "required by this annotation")
1246                                 .emit();
1247
1248                             return Some(());
1249                         }
1250
1251                         return None;
1252                     }
1253                     Some(item) => {
1254                         tcx.sess
1255                             .struct_span_err(item.span, "Not a function")
1256                             .span_note(attr_span, "required by this annotation")
1257                             .note(
1258                                 "All `#[rustc_must_implement_one_of]` arguments \
1259                             must be associated function names",
1260                             )
1261                             .emit();
1262                     }
1263                     None => {
1264                         tcx.sess
1265                             .struct_span_err(ident.span, "Function not found in this trait")
1266                             .emit();
1267                     }
1268                 }
1269
1270                 Some(())
1271             });
1272
1273             (errors.count() == 0).then_some(list)
1274         })
1275         // Check for duplicates
1276         .and_then(|list| {
1277             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1278             let mut no_dups = true;
1279
1280             for ident in &*list {
1281                 if let Some(dup) = set.insert(ident.name, ident.span) {
1282                     tcx.sess
1283                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1284                         .note(
1285                             "All `#[rustc_must_implement_one_of]` arguments \
1286                             must be unique",
1287                         )
1288                         .emit();
1289
1290                     no_dups = false;
1291                 }
1292             }
1293
1294             no_dups.then_some(list)
1295         });
1296
1297     ty::TraitDef::new(
1298         def_id,
1299         unsafety,
1300         paren_sugar,
1301         is_auto,
1302         is_marker,
1303         skip_array_during_method_dispatch,
1304         spec_kind,
1305         must_implement_one_of,
1306     )
1307 }
1308
1309 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1310     struct LateBoundRegionsDetector<'tcx> {
1311         tcx: TyCtxt<'tcx>,
1312         outer_index: ty::DebruijnIndex,
1313         has_late_bound_regions: Option<Span>,
1314     }
1315
1316     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1317         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1318             if self.has_late_bound_regions.is_some() {
1319                 return;
1320             }
1321             match ty.kind {
1322                 hir::TyKind::BareFn(..) => {
1323                     self.outer_index.shift_in(1);
1324                     intravisit::walk_ty(self, ty);
1325                     self.outer_index.shift_out(1);
1326                 }
1327                 _ => intravisit::walk_ty(self, ty),
1328             }
1329         }
1330
1331         fn visit_poly_trait_ref(
1332             &mut self,
1333             tr: &'tcx hir::PolyTraitRef<'tcx>,
1334             m: hir::TraitBoundModifier,
1335         ) {
1336             if self.has_late_bound_regions.is_some() {
1337                 return;
1338             }
1339             self.outer_index.shift_in(1);
1340             intravisit::walk_poly_trait_ref(self, tr, m);
1341             self.outer_index.shift_out(1);
1342         }
1343
1344         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1345             if self.has_late_bound_regions.is_some() {
1346                 return;
1347             }
1348
1349             match self.tcx.named_region(lt.hir_id) {
1350                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1351                 Some(
1352                     rl::Region::LateBound(debruijn, _, _)
1353                     | rl::Region::LateBoundAnon(debruijn, _, _),
1354                 ) if debruijn < self.outer_index => {}
1355                 Some(
1356                     rl::Region::LateBound(..)
1357                     | rl::Region::LateBoundAnon(..)
1358                     | rl::Region::Free(..),
1359                 )
1360                 | None => {
1361                     self.has_late_bound_regions = Some(lt.span);
1362                 }
1363             }
1364         }
1365     }
1366
1367     fn has_late_bound_regions<'tcx>(
1368         tcx: TyCtxt<'tcx>,
1369         def_id: LocalDefId,
1370         generics: &'tcx hir::Generics<'tcx>,
1371         decl: &'tcx hir::FnDecl<'tcx>,
1372     ) -> Option<Span> {
1373         let mut visitor = LateBoundRegionsDetector {
1374             tcx,
1375             outer_index: ty::INNERMOST,
1376             has_late_bound_regions: None,
1377         };
1378         let late_bound_map = tcx.is_late_bound_map(def_id);
1379         let is_late_bound = |id| {
1380             let id = tcx.hir().local_def_id(id);
1381             late_bound_map.map_or(false, |(_, set)| set.contains(&id))
1382         };
1383         for param in generics.params {
1384             if let GenericParamKind::Lifetime { .. } = param.kind {
1385                 if is_late_bound(param.hir_id) {
1386                     return Some(param.span);
1387                 }
1388             }
1389         }
1390         visitor.visit_fn_decl(decl);
1391         visitor.has_late_bound_regions
1392     }
1393
1394     match node {
1395         Node::TraitItem(item) => match item.kind {
1396             hir::TraitItemKind::Fn(ref sig, _) => {
1397                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1398             }
1399             _ => None,
1400         },
1401         Node::ImplItem(item) => match item.kind {
1402             hir::ImplItemKind::Fn(ref sig, _) => {
1403                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1404             }
1405             _ => None,
1406         },
1407         Node::ForeignItem(item) => match item.kind {
1408             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1409                 has_late_bound_regions(tcx, item.def_id, generics, fn_decl)
1410             }
1411             _ => None,
1412         },
1413         Node::Item(item) => match item.kind {
1414             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1415                 has_late_bound_regions(tcx, item.def_id, generics, sig.decl)
1416             }
1417             _ => None,
1418         },
1419         _ => None,
1420     }
1421 }
1422
1423 struct AnonConstInParamTyDetector {
1424     in_param_ty: bool,
1425     found_anon_const_in_param_ty: bool,
1426     ct: HirId,
1427 }
1428
1429 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1430     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1431         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1432             let prev = self.in_param_ty;
1433             self.in_param_ty = true;
1434             self.visit_ty(ty);
1435             self.in_param_ty = prev;
1436         }
1437     }
1438
1439     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1440         if self.in_param_ty && self.ct == c.hir_id {
1441             self.found_anon_const_in_param_ty = true;
1442         } else {
1443             intravisit::walk_anon_const(self, c)
1444         }
1445     }
1446 }
1447
1448 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1449     use rustc_hir::*;
1450
1451     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1452
1453     let node = tcx.hir().get(hir_id);
1454     let parent_def_id = match node {
1455         Node::ImplItem(_)
1456         | Node::TraitItem(_)
1457         | Node::Variant(_)
1458         | Node::Ctor(..)
1459         | Node::Field(_) => {
1460             let parent_id = tcx.hir().get_parent_item(hir_id);
1461             Some(parent_id.to_def_id())
1462         }
1463         // FIXME(#43408) always enable this once `lazy_normalization` is
1464         // stable enough and does not need a feature gate anymore.
1465         Node::AnonConst(_) => {
1466             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1467
1468             let mut in_param_ty = false;
1469             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1470                 if let Some(generics) = node.generics() {
1471                     let mut visitor = AnonConstInParamTyDetector {
1472                         in_param_ty: false,
1473                         found_anon_const_in_param_ty: false,
1474                         ct: hir_id,
1475                     };
1476
1477                     visitor.visit_generics(generics);
1478                     in_param_ty = visitor.found_anon_const_in_param_ty;
1479                     break;
1480                 }
1481             }
1482
1483             if in_param_ty {
1484                 // We do not allow generic parameters in anon consts if we are inside
1485                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1486                 None
1487             } else if tcx.lazy_normalization() {
1488                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1489                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1490                     //
1491                     // struct Foo<const N: usize = { .. }>;
1492                     //        ^^^       ^          ^^^^^^ def id of this anon const
1493                     //        ^         ^ param_id
1494                     //        ^ parent_def_id
1495                     //
1496                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1497                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1498                     //
1499                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1500                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1501                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1502                     //
1503                     // We fix this by having this function return the parent's generics ourselves and truncating the
1504                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1505                     //
1506                     // For the above code example that means we want `substs: []`
1507                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1508                     // the def id of the `{ N + 1 }` anon const
1509                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1510                     //
1511                     // This has some implications for how we get the predicates available to the anon const
1512                     // see `explicit_predicates_of` for more information on this
1513                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1514                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1515                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1516                     // In the above example this would be .params[..N#0]
1517                     let params = generics.params[..param_def_idx as usize].to_owned();
1518                     let param_def_id_to_index =
1519                         params.iter().map(|param| (param.def_id, param.index)).collect();
1520
1521                     return ty::Generics {
1522                         // we set the parent of these generics to be our parent's parent so that we
1523                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1524                         // struct Foo<const N: usize, const M: usize = { ... }>;
1525                         parent: generics.parent,
1526                         parent_count: generics.parent_count,
1527                         params,
1528                         param_def_id_to_index,
1529                         has_self: generics.has_self,
1530                         has_late_bound_regions: generics.has_late_bound_regions,
1531                     };
1532                 }
1533
1534                 // HACK(eddyb) this provides the correct generics when
1535                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1536                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1537                 //
1538                 // Note that we do not supply the parent generics when using
1539                 // `min_const_generics`.
1540                 Some(parent_def_id.to_def_id())
1541             } else {
1542                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1543                 match parent_node {
1544                     // HACK(eddyb) this provides the correct generics for repeat
1545                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1546                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1547                     // as they shouldn't be able to cause query cycle errors.
1548                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1549                         if constant.hir_id() == hir_id =>
1550                     {
1551                         Some(parent_def_id.to_def_id())
1552                     }
1553                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1554                         if constant.hir_id == hir_id =>
1555                     {
1556                         Some(parent_def_id.to_def_id())
1557                     }
1558                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1559                         Some(tcx.typeck_root_def_id(def_id))
1560                     }
1561                     _ => None,
1562                 }
1563             }
1564         }
1565         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1566             Some(tcx.typeck_root_def_id(def_id))
1567         }
1568         Node::Item(item) => match item.kind {
1569             ItemKind::OpaqueTy(hir::OpaqueTy {
1570                 origin:
1571                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1572                 ..
1573             }) => Some(fn_def_id.to_def_id()),
1574             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1575                 let parent_id = tcx.hir().get_parent_item(hir_id);
1576                 assert_ne!(parent_id, CRATE_DEF_ID);
1577                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1578                 // Opaque types are always nested within another item, and
1579                 // inherit the generics of the item.
1580                 Some(parent_id.to_def_id())
1581             }
1582             _ => None,
1583         },
1584         _ => None,
1585     };
1586
1587     let mut opt_self = None;
1588     let mut allow_defaults = false;
1589
1590     let no_generics = hir::Generics::empty();
1591     let ast_generics = match node {
1592         Node::TraitItem(item) => &item.generics,
1593
1594         Node::ImplItem(item) => &item.generics,
1595
1596         Node::Item(item) => {
1597             match item.kind {
1598                 ItemKind::Fn(.., ref generics, _)
1599                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1600
1601                 ItemKind::TyAlias(_, ref generics)
1602                 | ItemKind::Enum(_, ref generics)
1603                 | ItemKind::Struct(_, ref generics)
1604                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1605                 | ItemKind::Union(_, ref generics) => {
1606                     allow_defaults = true;
1607                     generics
1608                 }
1609
1610                 ItemKind::Trait(_, _, ref generics, ..)
1611                 | ItemKind::TraitAlias(ref generics, ..) => {
1612                     // Add in the self type parameter.
1613                     //
1614                     // Something of a hack: use the node id for the trait, also as
1615                     // the node id for the Self type parameter.
1616                     let param_id = item.def_id;
1617
1618                     opt_self = Some(ty::GenericParamDef {
1619                         index: 0,
1620                         name: kw::SelfUpper,
1621                         def_id: param_id.to_def_id(),
1622                         pure_wrt_drop: false,
1623                         kind: ty::GenericParamDefKind::Type {
1624                             has_default: false,
1625                             object_lifetime_default: rl::Set1::Empty,
1626                             synthetic: false,
1627                         },
1628                     });
1629
1630                     allow_defaults = true;
1631                     generics
1632                 }
1633
1634                 _ => &no_generics,
1635             }
1636         }
1637
1638         Node::ForeignItem(item) => match item.kind {
1639             ForeignItemKind::Static(..) => &no_generics,
1640             ForeignItemKind::Fn(_, _, ref generics) => generics,
1641             ForeignItemKind::Type => &no_generics,
1642         },
1643
1644         _ => &no_generics,
1645     };
1646
1647     let has_self = opt_self.is_some();
1648     let mut parent_has_self = false;
1649     let mut own_start = has_self as u32;
1650     let parent_count = parent_def_id.map_or(0, |def_id| {
1651         let generics = tcx.generics_of(def_id);
1652         assert!(!has_self);
1653         parent_has_self = generics.has_self;
1654         own_start = generics.count() as u32;
1655         generics.parent_count + generics.params.len()
1656     });
1657
1658     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1659
1660     if let Some(opt_self) = opt_self {
1661         params.push(opt_self);
1662     }
1663
1664     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics);
1665     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1666         name: param.name.ident().name,
1667         index: own_start + i as u32,
1668         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1669         pure_wrt_drop: param.pure_wrt_drop,
1670         kind: ty::GenericParamDefKind::Lifetime,
1671     }));
1672
1673     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1674
1675     // Now create the real type and const parameters.
1676     let type_start = own_start - has_self as u32 + params.len() as u32;
1677     let mut i = 0;
1678
1679     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1680         GenericParamKind::Lifetime { .. } => None,
1681         GenericParamKind::Type { ref default, synthetic, .. } => {
1682             if !allow_defaults && default.is_some() {
1683                 if !tcx.features().default_type_parameter_fallback {
1684                     tcx.struct_span_lint_hir(
1685                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1686                         param.hir_id,
1687                         param.span,
1688                         |lint| {
1689                             lint.build(
1690                                 "defaults for type parameters are only allowed in \
1691                                  `struct`, `enum`, `type`, or `trait` definitions",
1692                             )
1693                             .emit();
1694                         },
1695                     );
1696                 }
1697             }
1698
1699             let kind = ty::GenericParamDefKind::Type {
1700                 has_default: default.is_some(),
1701                 object_lifetime_default: object_lifetime_defaults
1702                     .as_ref()
1703                     .map_or(rl::Set1::Empty, |o| o[i]),
1704                 synthetic,
1705             };
1706
1707             let param_def = ty::GenericParamDef {
1708                 index: type_start + i as u32,
1709                 name: param.name.ident().name,
1710                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1711                 pure_wrt_drop: param.pure_wrt_drop,
1712                 kind,
1713             };
1714             i += 1;
1715             Some(param_def)
1716         }
1717         GenericParamKind::Const { default, .. } => {
1718             if !allow_defaults && default.is_some() {
1719                 tcx.sess.span_err(
1720                     param.span,
1721                     "defaults for const parameters are only allowed in \
1722                     `struct`, `enum`, `type`, or `trait` definitions",
1723                 );
1724             }
1725
1726             let param_def = ty::GenericParamDef {
1727                 index: type_start + i as u32,
1728                 name: param.name.ident().name,
1729                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1730                 pure_wrt_drop: param.pure_wrt_drop,
1731                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1732             };
1733             i += 1;
1734             Some(param_def)
1735         }
1736     }));
1737
1738     // provide junk type parameter defs - the only place that
1739     // cares about anything but the length is instantiation,
1740     // and we don't do that for closures.
1741     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1742         let dummy_args = if gen.is_some() {
1743             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1744         } else {
1745             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1746         };
1747
1748         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1749             index: type_start + i as u32,
1750             name: Symbol::intern(arg),
1751             def_id,
1752             pure_wrt_drop: false,
1753             kind: ty::GenericParamDefKind::Type {
1754                 has_default: false,
1755                 object_lifetime_default: rl::Set1::Empty,
1756                 synthetic: false,
1757             },
1758         }));
1759     }
1760
1761     // provide junk type parameter defs for const blocks.
1762     if let Node::AnonConst(_) = node {
1763         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1764         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1765             params.push(ty::GenericParamDef {
1766                 index: type_start,
1767                 name: Symbol::intern("<const_ty>"),
1768                 def_id,
1769                 pure_wrt_drop: false,
1770                 kind: ty::GenericParamDefKind::Type {
1771                     has_default: false,
1772                     object_lifetime_default: rl::Set1::Empty,
1773                     synthetic: false,
1774                 },
1775             });
1776         }
1777     }
1778
1779     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1780
1781     ty::Generics {
1782         parent: parent_def_id,
1783         parent_count,
1784         params,
1785         param_def_id_to_index,
1786         has_self: has_self || parent_has_self,
1787         has_late_bound_regions: has_late_bound_regions(tcx, node),
1788     }
1789 }
1790
1791 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1792     generic_args.iter().any(|arg| match arg {
1793         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1794         hir::GenericArg::Infer(_) => true,
1795         _ => false,
1796     })
1797 }
1798
1799 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1800 /// use inference to provide suggestions for the appropriate type if possible.
1801 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1802     debug!(?ty);
1803     use hir::TyKind::*;
1804     match &ty.kind {
1805         Infer => true,
1806         Slice(ty) => is_suggestable_infer_ty(ty),
1807         Array(ty, length) => {
1808             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1809         }
1810         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1811         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1812         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1813         Path(hir::QPath::TypeRelative(ty, segment)) => {
1814             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1815         }
1816         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1817             ty_opt.map_or(false, is_suggestable_infer_ty)
1818                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1819         }
1820         _ => false,
1821     }
1822 }
1823
1824 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1825     if let hir::FnRetTy::Return(ty) = output {
1826         if is_suggestable_infer_ty(ty) {
1827             return Some(&*ty);
1828         }
1829     }
1830     None
1831 }
1832
1833 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1834     use rustc_hir::Node::*;
1835     use rustc_hir::*;
1836
1837     let def_id = def_id.expect_local();
1838     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1839
1840     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1841
1842     match tcx.hir().get(hir_id) {
1843         TraitItem(hir::TraitItem {
1844             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1845             generics,
1846             ..
1847         })
1848         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
1849             infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1850         }
1851
1852         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
1853             // Do not try to inference the return type for a impl method coming from a trait
1854             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1855                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1856                 && i.of_trait.is_some()
1857             {
1858                 <dyn AstConv<'_>>::ty_of_fn(
1859                     &icx,
1860                     hir_id,
1861                     sig.header.unsafety,
1862                     sig.header.abi,
1863                     sig.decl,
1864                     Some(generics),
1865                     None,
1866                 )
1867             } else {
1868                 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1869             }
1870         }
1871
1872         TraitItem(hir::TraitItem {
1873             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1874             generics,
1875             ..
1876         }) => <dyn AstConv<'_>>::ty_of_fn(
1877             &icx,
1878             hir_id,
1879             header.unsafety,
1880             header.abi,
1881             decl,
1882             Some(generics),
1883             None,
1884         ),
1885
1886         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
1887             let abi = tcx.hir().get_foreign_abi(hir_id);
1888             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi)
1889         }
1890
1891         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1892             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1893             let inputs =
1894                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1895             ty::Binder::dummy(tcx.mk_fn_sig(
1896                 inputs,
1897                 ty,
1898                 false,
1899                 hir::Unsafety::Normal,
1900                 abi::Abi::Rust,
1901             ))
1902         }
1903
1904         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1905             // Closure signatures are not like other function
1906             // signatures and cannot be accessed through `fn_sig`. For
1907             // example, a closure signature excludes the `self`
1908             // argument. In any case they are embedded within the
1909             // closure type as part of the `ClosureSubsts`.
1910             //
1911             // To get the signature of a closure, you should use the
1912             // `sig` method on the `ClosureSubsts`:
1913             //
1914             //    substs.as_closure().sig(def_id, tcx)
1915             bug!(
1916                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1917             );
1918         }
1919
1920         x => {
1921             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1922         }
1923     }
1924 }
1925
1926 fn infer_return_ty_for_fn_sig<'tcx>(
1927     tcx: TyCtxt<'tcx>,
1928     sig: &hir::FnSig<'_>,
1929     generics: &hir::Generics<'_>,
1930     def_id: LocalDefId,
1931     icx: &ItemCtxt<'tcx>,
1932 ) -> ty::PolyFnSig<'tcx> {
1933     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1934
1935     match get_infer_ret_ty(&sig.decl.output) {
1936         Some(ty) => {
1937             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1938             // Typeck doesn't expect erased regions to be returned from `type_of`.
1939             let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1940                 ty::ReErased => tcx.lifetimes.re_static,
1941                 _ => r,
1942             });
1943             let fn_sig = ty::Binder::dummy(fn_sig);
1944
1945             let mut visitor = HirPlaceholderCollector::default();
1946             visitor.visit_ty(ty);
1947             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1948             let ret_ty = fn_sig.skip_binder().output();
1949             if ret_ty.is_suggestable(tcx) {
1950                 diag.span_suggestion(
1951                     ty.span,
1952                     "replace with the correct return type",
1953                     ret_ty.to_string(),
1954                     Applicability::MachineApplicable,
1955                 );
1956             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
1957                 let fn_sig = ret_ty.fn_sig(tcx);
1958                 if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable(tcx)) {
1959                     diag.span_suggestion(
1960                         ty.span,
1961                         "replace with the correct return type",
1962                         fn_sig.to_string(),
1963                         Applicability::MachineApplicable,
1964                     );
1965                 }
1966             } else if ret_ty.is_closure() {
1967                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1968                 // to prevent the user from getting a papercut while trying to use the unique closure
1969                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1970                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1971                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1972             }
1973             diag.emit();
1974
1975             fn_sig
1976         }
1977         None => <dyn AstConv<'_>>::ty_of_fn(
1978             icx,
1979             hir_id,
1980             sig.header.unsafety,
1981             sig.header.abi,
1982             sig.decl,
1983             Some(generics),
1984             None,
1985         ),
1986     }
1987 }
1988
1989 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1990     let icx = ItemCtxt::new(tcx, def_id);
1991     match tcx.hir().expect_item(def_id.expect_local()).kind {
1992         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1993             let selfty = tcx.type_of(def_id);
1994             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1995         }),
1996         _ => bug!(),
1997     }
1998 }
1999
2000 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2001     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2002     let item = tcx.hir().expect_item(def_id.expect_local());
2003     match &item.kind {
2004         hir::ItemKind::Impl(hir::Impl {
2005             polarity: hir::ImplPolarity::Negative(span),
2006             of_trait,
2007             ..
2008         }) => {
2009             if is_rustc_reservation {
2010                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2011                 tcx.sess.span_err(span, "reservation impls can't be negative");
2012             }
2013             ty::ImplPolarity::Negative
2014         }
2015         hir::ItemKind::Impl(hir::Impl {
2016             polarity: hir::ImplPolarity::Positive,
2017             of_trait: None,
2018             ..
2019         }) => {
2020             if is_rustc_reservation {
2021                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2022             }
2023             ty::ImplPolarity::Positive
2024         }
2025         hir::ItemKind::Impl(hir::Impl {
2026             polarity: hir::ImplPolarity::Positive,
2027             of_trait: Some(_),
2028             ..
2029         }) => {
2030             if is_rustc_reservation {
2031                 ty::ImplPolarity::Reservation
2032             } else {
2033                 ty::ImplPolarity::Positive
2034             }
2035         }
2036         item => bug!("impl_polarity: {:?} not an impl", item),
2037     }
2038 }
2039
2040 /// Returns the early-bound lifetimes declared in this generics
2041 /// listing. For anything other than fns/methods, this is just all
2042 /// the lifetimes that are declared. For fns or methods, we have to
2043 /// screen out those that do not appear in any where-clauses etc using
2044 /// `resolve_lifetime::early_bound_lifetimes`.
2045 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2046     tcx: TyCtxt<'tcx>,
2047     def_id: LocalDefId,
2048     generics: &'a hir::Generics<'a>,
2049 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2050     let late_bound_map = if generics.params.is_empty() {
2051         // This function may be called on `def_id == CRATE_DEF_ID`,
2052         // which makes `is_late_bound_map` ICE.  Don't even try if there
2053         // is no generic parameter.
2054         None
2055     } else {
2056         tcx.is_late_bound_map(def_id)
2057     };
2058     let is_late_bound = move |hir_id| {
2059         let id = tcx.hir().local_def_id(hir_id);
2060         late_bound_map.map_or(false, |(_, set)| set.contains(&id))
2061     };
2062     generics.params.iter().filter(move |param| match param.kind {
2063         GenericParamKind::Lifetime { .. } => !is_late_bound(param.hir_id),
2064         _ => false,
2065     })
2066 }
2067
2068 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2069 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2070 /// inferred constraints concerning which regions outlive other regions.
2071 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2072     debug!("predicates_defined_on({:?})", def_id);
2073     let mut result = tcx.explicit_predicates_of(def_id);
2074     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2075     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2076     if !inferred_outlives.is_empty() {
2077         debug!(
2078             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2079             def_id, inferred_outlives,
2080         );
2081         if result.predicates.is_empty() {
2082             result.predicates = inferred_outlives;
2083         } else {
2084             result.predicates = tcx
2085                 .arena
2086                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2087         }
2088     }
2089
2090     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2091     result
2092 }
2093
2094 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2095 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2096 /// `Self: Trait` predicates for traits.
2097 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2098     let mut result = tcx.predicates_defined_on(def_id);
2099
2100     if tcx.is_trait(def_id) {
2101         // For traits, add `Self: Trait` predicate. This is
2102         // not part of the predicates that a user writes, but it
2103         // is something that one must prove in order to invoke a
2104         // method or project an associated type.
2105         //
2106         // In the chalk setup, this predicate is not part of the
2107         // "predicates" for a trait item. But it is useful in
2108         // rustc because if you directly (e.g.) invoke a trait
2109         // method like `Trait::method(...)`, you must naturally
2110         // prove that the trait applies to the types that were
2111         // used, and adding the predicate into this list ensures
2112         // that this is done.
2113         //
2114         // We use a DUMMY_SP here as a way to signal trait bounds that come
2115         // from the trait itself that *shouldn't* be shown as the source of
2116         // an obligation and instead be skipped. Otherwise we'd use
2117         // `tcx.def_span(def_id);`
2118         let span = rustc_span::DUMMY_SP;
2119         result.predicates =
2120             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2121                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2122                 span,
2123             ))));
2124     }
2125     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2126     result
2127 }
2128
2129 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2130 /// N.B., this does not include any implied/inferred constraints.
2131 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2132     use rustc_hir::*;
2133
2134     debug!("explicit_predicates_of(def_id={:?})", def_id);
2135
2136     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2137     let node = tcx.hir().get(hir_id);
2138
2139     let mut is_trait = None;
2140     let mut is_default_impl_trait = None;
2141
2142     let icx = ItemCtxt::new(tcx, def_id);
2143
2144     const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
2145
2146     // We use an `IndexSet` to preserves order of insertion.
2147     // Preserving the order of insertion is important here so as not to break UI tests.
2148     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2149
2150     let ast_generics = match node {
2151         Node::TraitItem(item) => item.generics,
2152
2153         Node::ImplItem(item) => item.generics,
2154
2155         Node::Item(item) => {
2156             match item.kind {
2157                 ItemKind::Impl(ref impl_) => {
2158                     if impl_.defaultness.is_default() {
2159                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2160                     }
2161                     &impl_.generics
2162                 }
2163                 ItemKind::Fn(.., ref generics, _)
2164                 | ItemKind::TyAlias(_, ref generics)
2165                 | ItemKind::Enum(_, ref generics)
2166                 | ItemKind::Struct(_, ref generics)
2167                 | ItemKind::Union(_, ref generics) => *generics,
2168
2169                 ItemKind::Trait(_, _, ref generics, ..) => {
2170                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2171                     *generics
2172                 }
2173                 ItemKind::TraitAlias(ref generics, _) => {
2174                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2175                     *generics
2176                 }
2177                 ItemKind::OpaqueTy(OpaqueTy {
2178                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2179                     ..
2180                 }) => {
2181                     // return-position impl trait
2182                     //
2183                     // We don't inherit predicates from the parent here:
2184                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2185                     // then the return type is `f::<'static, T>::{{opaque}}`.
2186                     //
2187                     // If we inherited the predicates of `f` then we would
2188                     // require that `T: 'static` to show that the return
2189                     // type is well-formed.
2190                     //
2191                     // The only way to have something with this opaque type
2192                     // is from the return type of the containing function,
2193                     // which will ensure that the function's predicates
2194                     // hold.
2195                     return ty::GenericPredicates { parent: None, predicates: &[] };
2196                 }
2197                 ItemKind::OpaqueTy(OpaqueTy {
2198                     ref generics,
2199                     origin: hir::OpaqueTyOrigin::TyAlias,
2200                     ..
2201                 }) => {
2202                     // type-alias impl trait
2203                     generics
2204                 }
2205
2206                 _ => NO_GENERICS,
2207             }
2208         }
2209
2210         Node::ForeignItem(item) => match item.kind {
2211             ForeignItemKind::Static(..) => NO_GENERICS,
2212             ForeignItemKind::Fn(_, _, ref generics) => *generics,
2213             ForeignItemKind::Type => NO_GENERICS,
2214         },
2215
2216         _ => NO_GENERICS,
2217     };
2218
2219     let generics = tcx.generics_of(def_id);
2220     let parent_count = generics.parent_count as u32;
2221     let has_own_self = generics.has_self && parent_count == 0;
2222
2223     // Below we'll consider the bounds on the type parameters (including `Self`)
2224     // and the explicit where-clauses, but to get the full set of predicates
2225     // on a trait we need to add in the supertrait bounds and bounds found on
2226     // associated types.
2227     if let Some(_trait_ref) = is_trait {
2228         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2229     }
2230
2231     // In default impls, we can assume that the self type implements
2232     // the trait. So in:
2233     //
2234     //     default impl Foo for Bar { .. }
2235     //
2236     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2237     // (see below). Recall that a default impl is not itself an impl, but rather a
2238     // set of defaults that can be incorporated into another impl.
2239     if let Some(trait_ref) = is_default_impl_trait {
2240         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2241     }
2242
2243     // Collect the region predicates that were declared inline as
2244     // well. In the case of parameters declared on a fn or method, we
2245     // have to be careful to only iterate over early-bound regions.
2246     let mut index = parent_count
2247         + has_own_self as u32
2248         + early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics).count() as u32;
2249
2250     // Collect the predicates that were written inline by the user on each
2251     // type parameter (e.g., `<T: Foo>`).
2252     for param in ast_generics.params {
2253         match param.kind {
2254             // We already dealt with early bound lifetimes above.
2255             GenericParamKind::Lifetime { .. } => (),
2256             GenericParamKind::Type { .. } => {
2257                 let name = param.name.ident().name;
2258                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2259                 index += 1;
2260
2261                 let mut bounds = Bounds::default();
2262                 // Params are implicitly sized unless a `?Sized` bound is found
2263                 <dyn AstConv<'_>>::add_implicitly_sized(
2264                     &icx,
2265                     &mut bounds,
2266                     &[],
2267                     Some((param.hir_id, ast_generics.predicates)),
2268                     param.span,
2269                 );
2270                 predicates.extend(bounds.predicates(tcx, param_ty));
2271             }
2272             GenericParamKind::Const { .. } => {
2273                 // Bounds on const parameters are currently not possible.
2274                 index += 1;
2275             }
2276         }
2277     }
2278
2279     // Add in the bounds that appear in the where-clause.
2280     for predicate in ast_generics.predicates {
2281         match predicate {
2282             hir::WherePredicate::BoundPredicate(bound_pred) => {
2283                 let ty = icx.to_ty(bound_pred.bounded_ty);
2284                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2285
2286                 // Keep the type around in a dummy predicate, in case of no bounds.
2287                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2288                 // is still checked for WF.
2289                 if bound_pred.bounds.is_empty() {
2290                     if let ty::Param(_) = ty.kind() {
2291                         // This is a `where T:`, which can be in the HIR from the
2292                         // transformation that moves `?Sized` to `T`'s declaration.
2293                         // We can skip the predicate because type parameters are
2294                         // trivially WF, but also we *should*, to avoid exposing
2295                         // users who never wrote `where Type:,` themselves, to
2296                         // compiler/tooling bugs from not handling WF predicates.
2297                     } else {
2298                         let span = bound_pred.bounded_ty.span;
2299                         let re_root_empty = tcx.lifetimes.re_root_empty;
2300                         let predicate = ty::Binder::bind_with_vars(
2301                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2302                                 ty,
2303                                 re_root_empty,
2304                             )),
2305                             bound_vars,
2306                         );
2307                         predicates.insert((predicate.to_predicate(tcx), span));
2308                     }
2309                 }
2310
2311                 let mut bounds = Bounds::default();
2312                 <dyn AstConv<'_>>::add_bounds(
2313                     &icx,
2314                     ty,
2315                     bound_pred.bounds.iter(),
2316                     &mut bounds,
2317                     bound_vars,
2318                 );
2319                 predicates.extend(bounds.predicates(tcx, ty));
2320             }
2321
2322             hir::WherePredicate::RegionPredicate(region_pred) => {
2323                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2324                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2325                     let (r2, span) = match bound {
2326                         hir::GenericBound::Outlives(lt) => {
2327                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2328                         }
2329                         _ => bug!(),
2330                     };
2331                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2332                         ty::OutlivesPredicate(r1, r2),
2333                     ))
2334                     .to_predicate(icx.tcx);
2335
2336                     (pred, span)
2337                 }))
2338             }
2339
2340             hir::WherePredicate::EqPredicate(..) => {
2341                 // FIXME(#20041)
2342             }
2343         }
2344     }
2345
2346     if tcx.features().generic_const_exprs {
2347         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2348     }
2349
2350     let mut predicates: Vec<_> = predicates.into_iter().collect();
2351
2352     // Subtle: before we store the predicates into the tcx, we
2353     // sort them so that predicates like `T: Foo<Item=U>` come
2354     // before uses of `U`.  This avoids false ambiguity errors
2355     // in trait checking. See `setup_constraining_predicates`
2356     // for details.
2357     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2358         let self_ty = tcx.type_of(def_id);
2359         let trait_ref = tcx.impl_trait_ref(def_id);
2360         cgp::setup_constraining_predicates(
2361             tcx,
2362             &mut predicates,
2363             trait_ref,
2364             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2365         );
2366     }
2367
2368     let result = ty::GenericPredicates {
2369         parent: generics.parent,
2370         predicates: tcx.arena.alloc_from_iter(predicates),
2371     };
2372     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2373     result
2374 }
2375
2376 fn const_evaluatable_predicates_of<'tcx>(
2377     tcx: TyCtxt<'tcx>,
2378     def_id: LocalDefId,
2379 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2380     struct ConstCollector<'tcx> {
2381         tcx: TyCtxt<'tcx>,
2382         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2383     }
2384
2385     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2386         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2387             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2388             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2389             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2390                 assert_eq!(uv.promoted, None);
2391                 let span = self.tcx.hir().span(c.hir_id);
2392                 self.preds.insert((
2393                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2394                         .to_predicate(self.tcx),
2395                     span,
2396                 ));
2397             }
2398         }
2399
2400         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2401             // Do not look into const param defaults,
2402             // these get checked when they are actually instantiated.
2403             //
2404             // We do not want the following to error:
2405             //
2406             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2407             //     struct Bar<const N: usize>(Foo<N, 3>);
2408         }
2409     }
2410
2411     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2412     let node = tcx.hir().get(hir_id);
2413
2414     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2415     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2416         if let Some(of_trait) = &impl_.of_trait {
2417             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2418             collector.visit_trait_ref(of_trait);
2419         }
2420
2421         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2422         collector.visit_ty(impl_.self_ty);
2423     }
2424
2425     if let Some(generics) = node.generics() {
2426         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2427         collector.visit_generics(generics);
2428     }
2429
2430     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2431         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2432         collector.visit_fn_decl(fn_sig.decl);
2433     }
2434     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2435
2436     collector.preds
2437 }
2438
2439 fn trait_explicit_predicates_and_bounds(
2440     tcx: TyCtxt<'_>,
2441     def_id: LocalDefId,
2442 ) -> ty::GenericPredicates<'_> {
2443     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2444     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2445 }
2446
2447 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2448     let def_kind = tcx.def_kind(def_id);
2449     if let DefKind::Trait = def_kind {
2450         // Remove bounds on associated types from the predicates, they will be
2451         // returned by `explicit_item_bounds`.
2452         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2453         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2454
2455         let is_assoc_item_ty = |ty: Ty<'_>| {
2456             // For a predicate from a where clause to become a bound on an
2457             // associated type:
2458             // * It must use the identity substs of the item.
2459             //     * Since any generic parameters on the item are not in scope,
2460             //       this means that the item is not a GAT, and its identity
2461             //       substs are the same as the trait's.
2462             // * It must be an associated type for this trait (*not* a
2463             //   supertrait).
2464             if let ty::Projection(projection) = ty.kind() {
2465                 projection.substs == trait_identity_substs
2466                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2467             } else {
2468                 false
2469             }
2470         };
2471
2472         let predicates: Vec<_> = predicates_and_bounds
2473             .predicates
2474             .iter()
2475             .copied()
2476             .filter(|(pred, _)| match pred.kind().skip_binder() {
2477                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2478                 ty::PredicateKind::Projection(proj) => {
2479                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2480                 }
2481                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2482                 _ => true,
2483             })
2484             .collect();
2485         if predicates.len() == predicates_and_bounds.predicates.len() {
2486             predicates_and_bounds
2487         } else {
2488             ty::GenericPredicates {
2489                 parent: predicates_and_bounds.parent,
2490                 predicates: tcx.arena.alloc_slice(&predicates),
2491             }
2492         }
2493     } else {
2494         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2495             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2496             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2497                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2498                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2499                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2500                 //
2501                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2502                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2503                 //        ^^^                                             explicit_predicates_of on
2504                 //        parent item we dont have set as the
2505                 //        parent of generics returned by `generics_of`
2506                 //
2507                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2508                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2509                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2510                 return tcx.explicit_predicates_of(item_def_id);
2511             }
2512         }
2513         gather_explicit_predicates_of(tcx, def_id)
2514     }
2515 }
2516
2517 /// Converts a specific `GenericBound` from the AST into a set of
2518 /// predicates that apply to the self type. A vector is returned
2519 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2520 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2521 /// and `<T as Bar>::X == i32`).
2522 fn predicates_from_bound<'tcx>(
2523     astconv: &dyn AstConv<'tcx>,
2524     param_ty: Ty<'tcx>,
2525     bound: &'tcx hir::GenericBound<'tcx>,
2526     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2527 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2528     let mut bounds = Bounds::default();
2529     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2530     bounds.predicates(astconv.tcx(), param_ty).collect()
2531 }
2532
2533 fn compute_sig_of_foreign_fn_decl<'tcx>(
2534     tcx: TyCtxt<'tcx>,
2535     def_id: DefId,
2536     decl: &'tcx hir::FnDecl<'tcx>,
2537     abi: abi::Abi,
2538 ) -> ty::PolyFnSig<'tcx> {
2539     let unsafety = if abi == abi::Abi::RustIntrinsic {
2540         intrinsic_operation_unsafety(tcx.item_name(def_id))
2541     } else {
2542         hir::Unsafety::Unsafe
2543     };
2544     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2545     let fty = <dyn AstConv<'_>>::ty_of_fn(
2546         &ItemCtxt::new(tcx, def_id),
2547         hir_id,
2548         unsafety,
2549         abi,
2550         decl,
2551         None,
2552         None,
2553     );
2554
2555     // Feature gate SIMD types in FFI, since I am not sure that the
2556     // ABIs are handled at all correctly. -huonw
2557     if abi != abi::Abi::RustIntrinsic
2558         && abi != abi::Abi::PlatformIntrinsic
2559         && !tcx.features().simd_ffi
2560     {
2561         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2562             if ty.is_simd() {
2563                 let snip = tcx
2564                     .sess
2565                     .source_map()
2566                     .span_to_snippet(ast_ty.span)
2567                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2568                 tcx.sess
2569                     .struct_span_err(
2570                         ast_ty.span,
2571                         &format!(
2572                             "use of SIMD type{} in FFI is highly experimental and \
2573                              may result in invalid code",
2574                             snip
2575                         ),
2576                     )
2577                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2578                     .emit();
2579             }
2580         };
2581         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2582             check(input, *ty)
2583         }
2584         if let hir::FnRetTy::Return(ref ty) = decl.output {
2585             check(ty, fty.output().skip_binder())
2586         }
2587     }
2588
2589     fty
2590 }
2591
2592 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2593     match tcx.hir().get_if_local(def_id) {
2594         Some(Node::ForeignItem(..)) => true,
2595         Some(_) => false,
2596         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2597     }
2598 }
2599
2600 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2601     match tcx.hir().get_if_local(def_id) {
2602         Some(Node::Expr(&rustc_hir::Expr {
2603             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2604             ..
2605         })) => tcx.hir().body(body_id).generator_kind(),
2606         Some(_) => None,
2607         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2608     }
2609 }
2610
2611 fn from_target_feature(
2612     tcx: TyCtxt<'_>,
2613     id: DefId,
2614     attr: &ast::Attribute,
2615     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2616     target_features: &mut Vec<Symbol>,
2617 ) {
2618     let Some(list) = attr.meta_item_list() else { return };
2619     let bad_item = |span| {
2620         let msg = "malformed `target_feature` attribute input";
2621         let code = "enable = \"..\"".to_owned();
2622         tcx.sess
2623             .struct_span_err(span, msg)
2624             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2625             .emit();
2626     };
2627     let rust_features = tcx.features();
2628     for item in list {
2629         // Only `enable = ...` is accepted in the meta-item list.
2630         if !item.has_name(sym::enable) {
2631             bad_item(item.span());
2632             continue;
2633         }
2634
2635         // Must be of the form `enable = "..."` (a string).
2636         let Some(value) = item.value_str() else {
2637             bad_item(item.span());
2638             continue;
2639         };
2640
2641         // We allow comma separation to enable multiple features.
2642         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2643             let Some(feature_gate) = supported_target_features.get(feature) else {
2644                 let msg =
2645                     format!("the feature named `{}` is not valid for this target", feature);
2646                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2647                 err.span_label(
2648                     item.span(),
2649                     format!("`{}` is not valid for this target", feature),
2650                 );
2651                 if let Some(stripped) = feature.strip_prefix('+') {
2652                     let valid = supported_target_features.contains_key(stripped);
2653                     if valid {
2654                         err.help("consider removing the leading `+` in the feature name");
2655                     }
2656                 }
2657                 err.emit();
2658                 return None;
2659             };
2660
2661             // Only allow features whose feature gates have been enabled.
2662             let allowed = match feature_gate.as_ref().copied() {
2663                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2664                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2665                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2666                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2667                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2668                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2669                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2670                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2671                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2672                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2673                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2674                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2675                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2676                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2677                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2678                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2679                 Some(name) => bug!("unknown target feature gate {}", name),
2680                 None => true,
2681             };
2682             if !allowed && id.is_local() {
2683                 feature_err(
2684                     &tcx.sess.parse_sess,
2685                     feature_gate.unwrap(),
2686                     item.span(),
2687                     &format!("the target feature `{}` is currently unstable", feature),
2688                 )
2689                 .emit();
2690             }
2691             Some(Symbol::intern(feature))
2692         }));
2693     }
2694 }
2695
2696 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2697     use rustc_middle::mir::mono::Linkage::*;
2698
2699     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2700     // applicable to variable declarations and may not really make sense for
2701     // Rust code in the first place but allow them anyway and trust that the
2702     // user knows what they're doing. Who knows, unanticipated use cases may pop
2703     // up in the future.
2704     //
2705     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2706     // and don't have to be, LLVM treats them as no-ops.
2707     match name {
2708         "appending" => Appending,
2709         "available_externally" => AvailableExternally,
2710         "common" => Common,
2711         "extern_weak" => ExternalWeak,
2712         "external" => External,
2713         "internal" => Internal,
2714         "linkonce" => LinkOnceAny,
2715         "linkonce_odr" => LinkOnceODR,
2716         "private" => Private,
2717         "weak" => WeakAny,
2718         "weak_odr" => WeakODR,
2719         _ => {
2720             let span = tcx.hir().span_if_local(def_id);
2721             if let Some(span) = span {
2722                 tcx.sess.span_fatal(span, "invalid linkage specified")
2723             } else {
2724                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2725             }
2726         }
2727     }
2728 }
2729
2730 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2731     let attrs = tcx.get_attrs(id);
2732
2733     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2734     if tcx.should_inherit_track_caller(id) {
2735         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2736     }
2737
2738     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2739     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2740         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2741             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2742         }
2743     }
2744
2745     // The panic_no_unwind function called by TerminatorKind::Abort will never
2746     // unwind. If the panic handler that it invokes unwind then it will simply
2747     // call the panic handler again.
2748     if Some(id) == tcx.lang_items().panic_no_unwind() {
2749         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2750     }
2751
2752     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2753
2754     let mut inline_span = None;
2755     let mut link_ordinal_span = None;
2756     let mut no_sanitize_span = None;
2757     for attr in attrs.iter() {
2758         if attr.has_name(sym::cold) {
2759             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2760         } else if attr.has_name(sym::rustc_allocator) {
2761             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2762         } else if attr.has_name(sym::ffi_returns_twice) {
2763             if tcx.is_foreign_item(id) {
2764                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2765             } else {
2766                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2767                 struct_span_err!(
2768                     tcx.sess,
2769                     attr.span,
2770                     E0724,
2771                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2772                 )
2773                 .emit();
2774             }
2775         } else if attr.has_name(sym::ffi_pure) {
2776             if tcx.is_foreign_item(id) {
2777                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2778                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2779                     struct_span_err!(
2780                         tcx.sess,
2781                         attr.span,
2782                         E0757,
2783                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2784                     )
2785                     .emit();
2786                 } else {
2787                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2788                 }
2789             } else {
2790                 // `#[ffi_pure]` is only allowed on foreign functions
2791                 struct_span_err!(
2792                     tcx.sess,
2793                     attr.span,
2794                     E0755,
2795                     "`#[ffi_pure]` may only be used on foreign functions"
2796                 )
2797                 .emit();
2798             }
2799         } else if attr.has_name(sym::ffi_const) {
2800             if tcx.is_foreign_item(id) {
2801                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2802             } else {
2803                 // `#[ffi_const]` is only allowed on foreign functions
2804                 struct_span_err!(
2805                     tcx.sess,
2806                     attr.span,
2807                     E0756,
2808                     "`#[ffi_const]` may only be used on foreign functions"
2809                 )
2810                 .emit();
2811             }
2812         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2813             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2814         } else if attr.has_name(sym::naked) {
2815             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2816         } else if attr.has_name(sym::no_mangle) {
2817             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2818         } else if attr.has_name(sym::no_coverage) {
2819             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2820         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2821             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2822         } else if attr.has_name(sym::used) {
2823             let inner = attr.meta_item_list();
2824             match inner.as_deref() {
2825                 Some([item]) if item.has_name(sym::linker) => {
2826                     if !tcx.features().used_with_arg {
2827                         feature_err(
2828                             &tcx.sess.parse_sess,
2829                             sym::used_with_arg,
2830                             attr.span,
2831                             "`#[used(linker)]` is currently unstable",
2832                         )
2833                         .emit();
2834                     }
2835                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2836                 }
2837                 Some([item]) if item.has_name(sym::compiler) => {
2838                     if !tcx.features().used_with_arg {
2839                         feature_err(
2840                             &tcx.sess.parse_sess,
2841                             sym::used_with_arg,
2842                             attr.span,
2843                             "`#[used(compiler)]` is currently unstable",
2844                         )
2845                         .emit();
2846                     }
2847                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2848                 }
2849                 Some(_) => {
2850                     tcx.sess
2851                         .struct_span_err(
2852                             attr.span,
2853                             "expected `used`, `used(compiler)` or `used(linker)`",
2854                         )
2855                         .emit();
2856                 }
2857                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2858             }
2859         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2860             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2861                 struct_span_err!(
2862                     tcx.sess,
2863                     attr.span,
2864                     E0776,
2865                     "`#[cmse_nonsecure_entry]` requires C ABI"
2866                 )
2867                 .emit();
2868             }
2869             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2870                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2871                     .emit();
2872             }
2873             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2874         } else if attr.has_name(sym::thread_local) {
2875             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2876         } else if attr.has_name(sym::track_caller) {
2877             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2878                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2879                     .emit();
2880             }
2881             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2882                 feature_err(
2883                     &tcx.sess.parse_sess,
2884                     sym::closure_track_caller,
2885                     attr.span,
2886                     "`#[track_caller]` on closures is currently unstable",
2887                 )
2888                 .emit();
2889             }
2890             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2891         } else if attr.has_name(sym::export_name) {
2892             if let Some(s) = attr.value_str() {
2893                 if s.as_str().contains('\0') {
2894                     // `#[export_name = ...]` will be converted to a null-terminated string,
2895                     // so it may not contain any null characters.
2896                     struct_span_err!(
2897                         tcx.sess,
2898                         attr.span,
2899                         E0648,
2900                         "`export_name` may not contain null characters"
2901                     )
2902                     .emit();
2903                 }
2904                 codegen_fn_attrs.export_name = Some(s);
2905             }
2906         } else if attr.has_name(sym::target_feature) {
2907             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2908                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2909                     // The `#[target_feature]` attribute is allowed on
2910                     // WebAssembly targets on all functions, including safe
2911                     // ones. Other targets require that `#[target_feature]` is
2912                     // only applied to unsafe functions (pending the
2913                     // `target_feature_11` feature) because on most targets
2914                     // execution of instructions that are not supported is
2915                     // considered undefined behavior. For WebAssembly which is a
2916                     // 100% safe target at execution time it's not possible to
2917                     // execute undefined instructions, and even if a future
2918                     // feature was added in some form for this it would be a
2919                     // deterministic trap. There is no undefined behavior when
2920                     // executing WebAssembly so `#[target_feature]` is allowed
2921                     // on safe functions (but again, only for WebAssembly)
2922                     //
2923                     // Note that this is also allowed if `actually_rustdoc` so
2924                     // if a target is documenting some wasm-specific code then
2925                     // it's not spuriously denied.
2926                 } else if !tcx.features().target_feature_11 {
2927                     let mut err = feature_err(
2928                         &tcx.sess.parse_sess,
2929                         sym::target_feature_11,
2930                         attr.span,
2931                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2932                     );
2933                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2934                     err.emit();
2935                 } else if let Some(local_id) = id.as_local() {
2936                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2937                 }
2938             }
2939             from_target_feature(
2940                 tcx,
2941                 id,
2942                 attr,
2943                 supported_target_features,
2944                 &mut codegen_fn_attrs.target_features,
2945             );
2946         } else if attr.has_name(sym::linkage) {
2947             if let Some(val) = attr.value_str() {
2948                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2949             }
2950         } else if attr.has_name(sym::link_section) {
2951             if let Some(val) = attr.value_str() {
2952                 if val.as_str().bytes().any(|b| b == 0) {
2953                     let msg = format!(
2954                         "illegal null byte in link_section \
2955                          value: `{}`",
2956                         &val
2957                     );
2958                     tcx.sess.span_err(attr.span, &msg);
2959                 } else {
2960                     codegen_fn_attrs.link_section = Some(val);
2961                 }
2962             }
2963         } else if attr.has_name(sym::link_name) {
2964             codegen_fn_attrs.link_name = attr.value_str();
2965         } else if attr.has_name(sym::link_ordinal) {
2966             link_ordinal_span = Some(attr.span);
2967             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2968                 codegen_fn_attrs.link_ordinal = ordinal;
2969             }
2970         } else if attr.has_name(sym::no_sanitize) {
2971             no_sanitize_span = Some(attr.span);
2972             if let Some(list) = attr.meta_item_list() {
2973                 for item in list.iter() {
2974                     if item.has_name(sym::address) {
2975                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2976                     } else if item.has_name(sym::cfi) {
2977                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2978                     } else if item.has_name(sym::memory) {
2979                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2980                     } else if item.has_name(sym::memtag) {
2981                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
2982                     } else if item.has_name(sym::thread) {
2983                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2984                     } else if item.has_name(sym::hwaddress) {
2985                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2986                     } else {
2987                         tcx.sess
2988                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2989                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
2990                             .emit();
2991                     }
2992                 }
2993             }
2994         } else if attr.has_name(sym::instruction_set) {
2995             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2996                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2997                     [NestedMetaItem::MetaItem(set)] => {
2998                         let segments =
2999                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3000                         match segments.as_slice() {
3001                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3002                                 if !tcx.sess.target.has_thumb_interworking {
3003                                     struct_span_err!(
3004                                         tcx.sess.diagnostic(),
3005                                         attr.span,
3006                                         E0779,
3007                                         "target does not support `#[instruction_set]`"
3008                                     )
3009                                     .emit();
3010                                     None
3011                                 } else if segments[1] == sym::a32 {
3012                                     Some(InstructionSetAttr::ArmA32)
3013                                 } else if segments[1] == sym::t32 {
3014                                     Some(InstructionSetAttr::ArmT32)
3015                                 } else {
3016                                     unreachable!()
3017                                 }
3018                             }
3019                             _ => {
3020                                 struct_span_err!(
3021                                     tcx.sess.diagnostic(),
3022                                     attr.span,
3023                                     E0779,
3024                                     "invalid instruction set specified",
3025                                 )
3026                                 .emit();
3027                                 None
3028                             }
3029                         }
3030                     }
3031                     [] => {
3032                         struct_span_err!(
3033                             tcx.sess.diagnostic(),
3034                             attr.span,
3035                             E0778,
3036                             "`#[instruction_set]` requires an argument"
3037                         )
3038                         .emit();
3039                         None
3040                     }
3041                     _ => {
3042                         struct_span_err!(
3043                             tcx.sess.diagnostic(),
3044                             attr.span,
3045                             E0779,
3046                             "cannot specify more than one instruction set"
3047                         )
3048                         .emit();
3049                         None
3050                     }
3051                 },
3052                 _ => {
3053                     struct_span_err!(
3054                         tcx.sess.diagnostic(),
3055                         attr.span,
3056                         E0778,
3057                         "must specify an instruction set"
3058                     )
3059                     .emit();
3060                     None
3061                 }
3062             };
3063         } else if attr.has_name(sym::repr) {
3064             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3065                 Some(items) => match items.as_slice() {
3066                     [item] => match item.name_value_literal() {
3067                         Some((sym::align, literal)) => {
3068                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3069
3070                             match alignment {
3071                                 Ok(align) => Some(align),
3072                                 Err(msg) => {
3073                                     struct_span_err!(
3074                                         tcx.sess.diagnostic(),
3075                                         attr.span,
3076                                         E0589,
3077                                         "invalid `repr(align)` attribute: {}",
3078                                         msg
3079                                     )
3080                                     .emit();
3081
3082                                     None
3083                                 }
3084                             }
3085                         }
3086                         _ => None,
3087                     },
3088                     [] => None,
3089                     _ => None,
3090                 },
3091                 None => None,
3092             };
3093         }
3094     }
3095
3096     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3097         if !attr.has_name(sym::inline) {
3098             return ia;
3099         }
3100         match attr.meta_kind() {
3101             Some(MetaItemKind::Word) => InlineAttr::Hint,
3102             Some(MetaItemKind::List(ref items)) => {
3103                 inline_span = Some(attr.span);
3104                 if items.len() != 1 {
3105                     struct_span_err!(
3106                         tcx.sess.diagnostic(),
3107                         attr.span,
3108                         E0534,
3109                         "expected one argument"
3110                     )
3111                     .emit();
3112                     InlineAttr::None
3113                 } else if list_contains_name(&items, sym::always) {
3114                     InlineAttr::Always
3115                 } else if list_contains_name(&items, sym::never) {
3116                     InlineAttr::Never
3117                 } else {
3118                     struct_span_err!(
3119                         tcx.sess.diagnostic(),
3120                         items[0].span(),
3121                         E0535,
3122                         "invalid argument"
3123                     )
3124                     .emit();
3125
3126                     InlineAttr::None
3127                 }
3128             }
3129             Some(MetaItemKind::NameValue(_)) => ia,
3130             None => ia,
3131         }
3132     });
3133
3134     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3135         if !attr.has_name(sym::optimize) {
3136             return ia;
3137         }
3138         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3139         match attr.meta_kind() {
3140             Some(MetaItemKind::Word) => {
3141                 err(attr.span, "expected one argument");
3142                 ia
3143             }
3144             Some(MetaItemKind::List(ref items)) => {
3145                 inline_span = Some(attr.span);
3146                 if items.len() != 1 {
3147                     err(attr.span, "expected one argument");
3148                     OptimizeAttr::None
3149                 } else if list_contains_name(&items, sym::size) {
3150                     OptimizeAttr::Size
3151                 } else if list_contains_name(&items, sym::speed) {
3152                     OptimizeAttr::Speed
3153                 } else {
3154                     err(items[0].span(), "invalid argument");
3155                     OptimizeAttr::None
3156                 }
3157             }
3158             Some(MetaItemKind::NameValue(_)) => ia,
3159             None => ia,
3160         }
3161     });
3162
3163     // #73631: closures inherit `#[target_feature]` annotations
3164     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3165         let owner_id = tcx.parent(id).expect("closure should have a parent");
3166         codegen_fn_attrs
3167             .target_features
3168             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3169     }
3170
3171     // If a function uses #[target_feature] it can't be inlined into general
3172     // purpose functions as they wouldn't have the right target features
3173     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3174     // respected.
3175     if !codegen_fn_attrs.target_features.is_empty() {
3176         if codegen_fn_attrs.inline == InlineAttr::Always {
3177             if let Some(span) = inline_span {
3178                 tcx.sess.span_err(
3179                     span,
3180                     "cannot use `#[inline(always)]` with \
3181                      `#[target_feature]`",
3182                 );
3183             }
3184         }
3185     }
3186
3187     if !codegen_fn_attrs.no_sanitize.is_empty() {
3188         if codegen_fn_attrs.inline == InlineAttr::Always {
3189             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3190                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3191                 tcx.struct_span_lint_hir(
3192                     lint::builtin::INLINE_NO_SANITIZE,
3193                     hir_id,
3194                     no_sanitize_span,
3195                     |lint| {
3196                         lint.build("`no_sanitize` will have no effect after inlining")
3197                             .span_note(inline_span, "inlining requested here")
3198                             .emit();
3199                     },
3200                 )
3201             }
3202         }
3203     }
3204
3205     // Weak lang items have the same semantics as "std internal" symbols in the
3206     // sense that they're preserved through all our LTO passes and only
3207     // strippable by the linker.
3208     //
3209     // Additionally weak lang items have predetermined symbol names.
3210     if tcx.is_weak_lang_item(id) {
3211         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3212     }
3213     if let Some(name) = weak_lang_items::link_name(attrs) {
3214         codegen_fn_attrs.export_name = Some(name);
3215         codegen_fn_attrs.link_name = Some(name);
3216     }
3217     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3218
3219     // Internal symbols to the standard library all have no_mangle semantics in
3220     // that they have defined symbol names present in the function name. This
3221     // also applies to weak symbols where they all have known symbol names.
3222     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3223         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3224     }
3225
3226     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3227     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3228     // intrinsic functions.
3229     if let Some(name) = &codegen_fn_attrs.link_name {
3230         if name.as_str().starts_with("llvm.") {
3231             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3232         }
3233     }
3234
3235     codegen_fn_attrs
3236 }
3237
3238 /// Computes the set of target features used in a function for the purposes of
3239 /// inline assembly.
3240 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, id: DefId) -> &'tcx FxHashSet<Symbol> {
3241     let mut target_features = tcx.sess.target_features.clone();
3242     let attrs = tcx.codegen_fn_attrs(id);
3243     target_features.extend(&attrs.target_features);
3244     match attrs.instruction_set {
3245         None => {}
3246         Some(InstructionSetAttr::ArmA32) => {
3247             target_features.remove(&sym::thumb_mode);
3248         }
3249         Some(InstructionSetAttr::ArmT32) => {
3250             target_features.insert(sym::thumb_mode);
3251         }
3252     }
3253     tcx.arena.alloc(target_features)
3254 }
3255
3256 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3257 /// applied to the method prototype.
3258 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3259     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3260         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3261         && let Some(trait_item) = impl_item.trait_item_def_id
3262     {
3263         return tcx
3264             .codegen_fn_attrs(trait_item)
3265             .flags
3266             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3267     }
3268
3269     false
3270 }
3271
3272 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3273     use rustc_ast::{Lit, LitIntType, LitKind};
3274     let meta_item_list = attr.meta_item_list();
3275     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3276     let sole_meta_list = match meta_item_list {
3277         Some([item]) => item.literal(),
3278         Some(_) => {
3279             tcx.sess
3280                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3281                 .note("the attribute requires exactly one argument")
3282                 .emit();
3283             return None;
3284         }
3285         _ => None,
3286     };
3287     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3288         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3289         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3290         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3291         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3292         //
3293         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3294         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3295         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3296         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3297         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3298         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3299         // about LINK.EXE failing.)
3300         if *ordinal <= u16::MAX as u128 {
3301             Some(*ordinal as u16)
3302         } else {
3303             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3304             tcx.sess
3305                 .struct_span_err(attr.span, &msg)
3306                 .note("the value may not exceed `u16::MAX`")
3307                 .emit();
3308             None
3309         }
3310     } else {
3311         tcx.sess
3312             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3313             .note("an unsuffixed integer value, e.g., `1`, is expected")
3314             .emit();
3315         None
3316     }
3317 }
3318
3319 fn check_link_name_xor_ordinal(
3320     tcx: TyCtxt<'_>,
3321     codegen_fn_attrs: &CodegenFnAttrs,
3322     inline_span: Option<Span>,
3323 ) {
3324     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3325         return;
3326     }
3327     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3328     if let Some(span) = inline_span {
3329         tcx.sess.span_err(span, msg);
3330     } else {
3331         tcx.sess.err(msg);
3332     }
3333 }
3334
3335 /// Checks the function annotated with `#[target_feature]` is not a safe
3336 /// trait method implementation, reporting an error if it is.
3337 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3338     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3339     let node = tcx.hir().get(hir_id);
3340     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3341         let parent_id = tcx.hir().get_parent_item(hir_id);
3342         let parent_item = tcx.hir().expect_item(parent_id);
3343         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3344             tcx.sess
3345                 .struct_span_err(
3346                     attr_span,
3347                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3348                 )
3349                 .span_label(attr_span, "cannot be applied to safe trait method")
3350                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3351                 .emit();
3352         }
3353     }
3354 }