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::Attribute;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::map::Map;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         default_anon_const_substs: type_of::default_anon_const_substs,
  72         type_of: type_of::type_of,
  73         item_bounds: item_bounds::item_bounds,
  74         explicit_item_bounds: item_bounds::explicit_item_bounds,
  75         generics_of,
  76         predicates_of,
  77         predicates_defined_on,
  78         explicit_predicates_of,
  79         super_predicates_of,
  80         super_predicates_that_define_assoc_type,
  81         trait_explicit_predicates_and_bounds,
  82         type_param_predicates,
  83         trait_def,
  84         adt_def,
  85         fn_sig,
  86         impl_trait_ref,
  87         impl_polarity,
  88         is_foreign_item,
  89         static_mutability,
  90         generator_kind,
  91         codegen_fn_attrs,
  92         collect_mod_item_types,
  93         should_inherit_track_caller,
  94         ..*providers
  95     };
  96 }
  97
  98 ///////////////////////////////////////////////////////////////////////////
  99
 100 /// Context specific to some particular item. This is what implements
 101 /// `AstConv`. It has information about the predicates that are defined
 102 /// on the trait. Unfortunately, this predicate information is
 103 /// available in various different forms at various points in the
 104 /// process. So we can't just store a pointer to e.g., the AST or the
 105 /// parsed ty form, we have to be more flexible. To this end, the
 106 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 107 /// `get_type_parameter_bounds` requests, drawing the information from
 108 /// the AST (`hir::Generics`), recursively.
 109 pub struct ItemCtxt<'tcx> {
 110     tcx: TyCtxt<'tcx>,
 111     item_def_id: DefId,
 112 }
 113
 114 ///////////////////////////////////////////////////////////////////////////
 115
 116 #[derive(Default)]
 117 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 118
 119 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 120     type Map = intravisit::ErasedMap<'v>;
 121
 122     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 123         NestedVisitorMap::None
 124     }
 125     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 126         if let hir::TyKind::Infer = t.kind {
 127             self.0.push(t.span);
 128         }
 129         intravisit::walk_ty(self, t)
 130     }
 131     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 132         match generic_arg {
 133             hir::GenericArg::Infer(inf) => {
 134                 self.0.push(inf.span);
 135                 intravisit::walk_inf(self, inf);
 136             }
 137             hir::GenericArg::Type(t) => self.visit_ty(t),
 138             _ => {}
 139         }
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder(tcx, "type", placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty {
 193             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 194                 is_fn = true;
 195
 196                 // Check if parent is const or static
 197                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 198                 let parent_node = tcx.hir().get(parent_id);
 199
 200                 is_const_or_static = matches!(
 201                     parent_node,
 202                     Node::Item(&hir::Item {
 203                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 204                         ..
 205                     }) | Node::TraitItem(&hir::TraitItem {
 206                         kind: hir::TraitItemKind::Const(..),
 207                         ..
 208                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 209                 );
 210             }
 211         }
 212
 213         // if function is wrapped around a const or static,
 214         // then don't show the suggestion
 215         if !(is_fn && is_const_or_static) {
 216             err.multipart_suggestion(
 217                 "use type parameters instead",
 218                 sugg,
 219                 Applicability::HasPlaceholders,
 220             );
 221         }
 222     }
 223     err.emit();
 224 }
 225
 226 fn reject_placeholder_type_signatures_in_item<'tcx>(
 227     tcx: TyCtxt<'tcx>,
 228     item: &'tcx hir::Item<'tcx>,
 229 ) {
 230     let (generics, suggest) = match &item.kind {
 231         hir::ItemKind::Union(_, generics)
 232         | hir::ItemKind::Enum(_, generics)
 233         | hir::ItemKind::TraitAlias(generics, _)
 234         | hir::ItemKind::Trait(_, _, generics, ..)
 235         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 236         | hir::ItemKind::Struct(_, generics) => (generics, true),
 237         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 238         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 239         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 240         _ => return,
 241     };
 242
 243     let mut visitor = PlaceholderHirTyCollector::default();
 244     visitor.visit_item(item);
 245
 246     placeholder_type_error(
 247         tcx,
 248         Some(generics.span),
 249         generics.params,
 250         visitor.0,
 251         suggest,
 252         None,
 253         item.kind.descr(),
 254     );
 255 }
 256
 257 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 258     type Map = Map<'tcx>;
 259
 260     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 261         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 262     }
 263
 264     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 265         convert_item(self.tcx, item.item_id());
 266         reject_placeholder_type_signatures_in_item(self.tcx, item);
 267         intravisit::walk_item(self, item);
 268     }
 269
 270     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 271         for param in generics.params {
 272             match param.kind {
 273                 hir::GenericParamKind::Lifetime { .. } => {}
 274                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 275                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 276                     self.tcx.ensure().type_of(def_id);
 277                 }
 278                 hir::GenericParamKind::Type { .. } => {}
 279                 hir::GenericParamKind::Const { default, .. } => {
 280                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 281                     self.tcx.ensure().type_of(def_id);
 282                     if let Some(default) = default {
 283                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 284                         // need to store default and type of default
 285                         self.tcx.ensure().type_of(default_def_id);
 286                         self.tcx.ensure().const_param_default(def_id);
 287                     }
 288                 }
 289             }
 290         }
 291         intravisit::walk_generics(self, generics);
 292     }
 293
 294     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 295         if let hir::ExprKind::Closure(..) = expr.kind {
 296             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 297             self.tcx.ensure().generics_of(def_id);
 298             self.tcx.ensure().type_of(def_id);
 299         }
 300         intravisit::walk_expr(self, expr);
 301     }
 302
 303     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 304         convert_trait_item(self.tcx, trait_item.trait_item_id());
 305         intravisit::walk_trait_item(self, trait_item);
 306     }
 307
 308     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 309         convert_impl_item(self.tcx, impl_item.impl_item_id());
 310         intravisit::walk_impl_item(self, impl_item);
 311     }
 312 }
 313
 314 ///////////////////////////////////////////////////////////////////////////
 315 // Utility types and common code for the above passes.
 316
 317 fn bad_placeholder<'tcx>(
 318     tcx: TyCtxt<'tcx>,
 319     placeholder_kind: &'static str,
 320     mut spans: Vec<Span>,
 321     kind: &'static str,
 322 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 323     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 324
 325     spans.sort();
 326     let mut err = struct_span_err!(
 327         tcx.sess,
 328         spans.clone(),
 329         E0121,
 330         "the {} placeholder `_` is not allowed within types on item signatures for {}",
 331         placeholder_kind,
 332         kind
 333     );
 334     for span in spans {
 335         err.span_label(span, "not allowed in type signatures");
 336     }
 337     err
 338 }
 339
 340 impl<'tcx> ItemCtxt<'tcx> {
 341     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 342         ItemCtxt { tcx, item_def_id }
 343     }
 344
 345     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 346         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 347     }
 348
 349     pub fn hir_id(&self) -> hir::HirId {
 350         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 351     }
 352
 353     pub fn node(&self) -> hir::Node<'tcx> {
 354         self.tcx.hir().get(self.hir_id())
 355     }
 356 }
 357
 358 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 359     fn tcx(&self) -> TyCtxt<'tcx> {
 360         self.tcx
 361     }
 362
 363     fn item_def_id(&self) -> Option<DefId> {
 364         Some(self.item_def_id)
 365     }
 366
 367     fn get_type_parameter_bounds(
 368         &self,
 369         span: Span,
 370         def_id: DefId,
 371         assoc_name: Ident,
 372     ) -> ty::GenericPredicates<'tcx> {
 373         self.tcx.at(span).type_param_predicates((
 374             self.item_def_id,
 375             def_id.expect_local(),
 376             assoc_name,
 377         ))
 378     }
 379
 380     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 381         None
 382     }
 383
 384     fn allow_ty_infer(&self) -> bool {
 385         false
 386     }
 387
 388     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 389         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 390     }
 391
 392     fn ct_infer(
 393         &self,
 394         ty: Ty<'tcx>,
 395         _: Option<&ty::GenericParamDef>,
 396         span: Span,
 397     ) -> &'tcx Const<'tcx> {
 398         bad_placeholder(self.tcx(), "const", vec![span], "generic").emit();
 399         // Typeck doesn't expect erased regions to be returned from `type_of`.
 400         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 401             ty::ReErased => self.tcx.lifetimes.re_static,
 402             _ => r,
 403         });
 404         self.tcx().const_error(ty)
 405     }
 406
 407     fn projected_ty_from_poly_trait_ref(
 408         &self,
 409         span: Span,
 410         item_def_id: DefId,
 411         item_segment: &hir::PathSegment<'_>,
 412         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 413     ) -> Ty<'tcx> {
 414         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 415             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 416                 self,
 417                 self.tcx,
 418                 span,
 419                 item_def_id,
 420                 item_segment,
 421                 trait_ref.substs,
 422             );
 423             self.tcx().mk_projection(item_def_id, item_substs)
 424         } else {
 425             // There are no late-bound regions; we can just ignore the binder.
 426             let mut err = struct_span_err!(
 427                 self.tcx().sess,
 428                 span,
 429                 E0212,
 430                 "cannot use the associated type of a trait \
 431                  with uninferred generic parameters"
 432             );
 433
 434             match self.node() {
 435                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 436                     let item =
 437                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_did(self.hir_id()));
 438                     match &item.kind {
 439                         hir::ItemKind::Enum(_, generics)
 440                         | hir::ItemKind::Struct(_, generics)
 441                         | hir::ItemKind::Union(_, generics) => {
 442                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 443                             let (lt_sp, sugg) = match generics.params {
 444                                 [] => (generics.span, format!("<{}>", lt_name)),
 445                                 [bound, ..] => {
 446                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 447                                 }
 448                             };
 449                             let suggestions = vec![
 450                                 (lt_sp, sugg),
 451                                 (
 452                                     span.with_hi(item_segment.ident.span.lo()),
 453                                     format!(
 454                                         "{}::",
 455                                         // Replace the existing lifetimes with a new named lifetime.
 456                                         self.tcx
 457                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 458                                                 self.tcx.mk_region(ty::ReEarlyBound(
 459                                                     ty::EarlyBoundRegion {
 460                                                         def_id: item_def_id,
 461                                                         index: 0,
 462                                                         name: Symbol::intern(&lt_name),
 463                                                     },
 464                                                 ))
 465                                             })
 466                                             .0,
 467                                     ),
 468                                 ),
 469                             ];
 470                             err.multipart_suggestion(
 471                                 "use a fully qualified path with explicit lifetimes",
 472                                 suggestions,
 473                                 Applicability::MaybeIncorrect,
 474                             );
 475                         }
 476                         _ => {}
 477                     }
 478                 }
 479                 hir::Node::Item(hir::Item {
 480                     kind:
 481                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 482                     ..
 483                 }) => {}
 484                 hir::Node::Item(_)
 485                 | hir::Node::ForeignItem(_)
 486                 | hir::Node::TraitItem(_)
 487                 | hir::Node::ImplItem(_) => {
 488                     err.span_suggestion_verbose(
 489                         span.with_hi(item_segment.ident.span.lo()),
 490                         "use a fully qualified path with inferred lifetimes",
 491                         format!(
 492                             "{}::",
 493                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 494                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 495                         ),
 496                         Applicability::MaybeIncorrect,
 497                     );
 498                 }
 499                 _ => {}
 500             }
 501             err.emit();
 502             self.tcx().ty_error()
 503         }
 504     }
 505
 506     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 507         // Types in item signatures are not normalized to avoid undue dependencies.
 508         ty
 509     }
 510
 511     fn set_tainted_by_errors(&self) {
 512         // There's no obvious place to track this, so just let it go.
 513     }
 514
 515     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 516         // There's no place to record types from signatures?
 517     }
 518 }
 519
 520 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 521 fn get_new_lifetime_name<'tcx>(
 522     tcx: TyCtxt<'tcx>,
 523     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 524     generics: &hir::Generics<'tcx>,
 525 ) -> String {
 526     let existing_lifetimes = tcx
 527         .collect_referenced_late_bound_regions(&poly_trait_ref)
 528         .into_iter()
 529         .filter_map(|lt| {
 530             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 531                 Some(name.as_str().to_string())
 532             } else {
 533                 None
 534             }
 535         })
 536         .chain(generics.params.iter().filter_map(|param| {
 537             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 538                 Some(param.name.ident().as_str().to_string())
 539             } else {
 540                 None
 541             }
 542         }))
 543         .collect::<FxHashSet<String>>();
 544
 545     let a_to_z_repeat_n = |n| {
 546         (b'a'..=b'z').map(move |c| {
 547             let mut s = '\''.to_string();
 548             s.extend(std::iter::repeat(char::from(c)).take(n));
 549             s
 550         })
 551     };
 552
 553     // If all single char lifetime names are present, we wrap around and double the chars.
 554     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 555 }
 556
 557 /// Returns the predicates defined on `item_def_id` of the form
 558 /// `X: Foo` where `X` is the type parameter `def_id`.
 559 fn type_param_predicates(
 560     tcx: TyCtxt<'_>,
 561     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 562 ) -> ty::GenericPredicates<'_> {
 563     use rustc_hir::*;
 564
 565     // In the AST, bounds can derive from two places. Either
 566     // written inline like `<T: Foo>` or in a where-clause like
 567     // `where T: Foo`.
 568
 569     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 570     let param_owner = tcx.hir().ty_param_owner(param_id);
 571     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 572     let generics = tcx.generics_of(param_owner_def_id);
 573     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 574     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 575
 576     // Don't look for bounds where the type parameter isn't in scope.
 577     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 578         None
 579     } else {
 580         tcx.generics_of(item_def_id).parent
 581     };
 582
 583     let mut result = parent
 584         .map(|parent| {
 585             let icx = ItemCtxt::new(tcx, parent);
 586             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 587         })
 588         .unwrap_or_default();
 589     let mut extend = None;
 590
 591     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 592     let ast_generics = match tcx.hir().get(item_hir_id) {
 593         Node::TraitItem(item) => &item.generics,
 594
 595         Node::ImplItem(item) => &item.generics,
 596
 597         Node::Item(item) => {
 598             match item.kind {
 599                 ItemKind::Fn(.., ref generics, _)
 600                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 601                 | ItemKind::TyAlias(_, ref generics)
 602                 | ItemKind::OpaqueTy(OpaqueTy {
 603                     ref generics,
 604                     origin: hir::OpaqueTyOrigin::TyAlias,
 605                     ..
 606                 })
 607                 | ItemKind::Enum(_, ref generics)
 608                 | ItemKind::Struct(_, ref generics)
 609                 | ItemKind::Union(_, ref generics) => generics,
 610                 ItemKind::Trait(_, _, ref generics, ..) => {
 611                     // Implied `Self: Trait` and supertrait bounds.
 612                     if param_id == item_hir_id {
 613                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 614                         extend =
 615                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 616                     }
 617                     generics
 618                 }
 619                 _ => return result,
 620             }
 621         }
 622
 623         Node::ForeignItem(item) => match item.kind {
 624             ForeignItemKind::Fn(_, _, ref generics) => generics,
 625             _ => return result,
 626         },
 627
 628         _ => return result,
 629     };
 630
 631     let icx = ItemCtxt::new(tcx, item_def_id);
 632     let extra_predicates = extend.into_iter().chain(
 633         icx.type_parameter_bounds_in_generics(
 634             ast_generics,
 635             param_id,
 636             ty,
 637             OnlySelfBounds(true),
 638             Some(assoc_name),
 639         )
 640         .into_iter()
 641         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 642             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 643             _ => false,
 644         }),
 645     );
 646     result.predicates =
 647         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 648     result
 649 }
 650
 651 impl<'tcx> ItemCtxt<'tcx> {
 652     /// Finds bounds from `hir::Generics`. This requires scanning through the
 653     /// AST. We do this to avoid having to convert *all* the bounds, which
 654     /// would create artificial cycles. Instead, we can only convert the
 655     /// bounds for a type parameter `X` if `X::Foo` is used.
 656     fn type_parameter_bounds_in_generics(
 657         &self,
 658         ast_generics: &'tcx hir::Generics<'tcx>,
 659         param_id: hir::HirId,
 660         ty: Ty<'tcx>,
 661         only_self_bounds: OnlySelfBounds,
 662         assoc_name: Option<Ident>,
 663     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 664         let from_ty_params = ast_generics
 665             .params
 666             .iter()
 667             .filter_map(|param| match param.kind {
 668                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 669                 _ => None,
 670             })
 671             .flat_map(|bounds| bounds.iter())
 672             .filter(|b| match assoc_name {
 673                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 674                 None => true,
 675             })
 676             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 677
 678         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 679         let from_where_clauses = ast_generics
 680             .where_clause
 681             .predicates
 682             .iter()
 683             .filter_map(|wp| match *wp {
 684                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 685                 _ => None,
 686             })
 687             .flat_map(|bp| {
 688                 let bt = if bp.is_param_bound(param_def_id) {
 689                     Some(ty)
 690                 } else if !only_self_bounds.0 {
 691                     Some(self.to_ty(bp.bounded_ty))
 692                 } else {
 693                     None
 694                 };
 695                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 696
 697                 bp.bounds
 698                     .iter()
 699                     .filter(|b| match assoc_name {
 700                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 701                         None => true,
 702                     })
 703                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 704             })
 705             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 706
 707         from_ty_params.chain(from_where_clauses).collect()
 708     }
 709
 710     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 711         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 712
 713         match b {
 714             hir::GenericBound::Trait(poly_trait_ref, _) => {
 715                 let trait_ref = &poly_trait_ref.trait_ref;
 716                 if let Some(trait_did) = trait_ref.trait_def_id() {
 717                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 718                 } else {
 719                     false
 720                 }
 721             }
 722             _ => false,
 723         }
 724     }
 725 }
 726
 727 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 728     let it = tcx.hir().item(item_id);
 729     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 730     let def_id = item_id.def_id;
 731
 732     match it.kind {
 733         // These don't define types.
 734         hir::ItemKind::ExternCrate(_)
 735         | hir::ItemKind::Use(..)
 736         | hir::ItemKind::Macro(_)
 737         | hir::ItemKind::Mod(_)
 738         | hir::ItemKind::GlobalAsm(_) => {}
 739         hir::ItemKind::ForeignMod { items, .. } => {
 740             for item in items {
 741                 let item = tcx.hir().foreign_item(item.id);
 742                 tcx.ensure().generics_of(item.def_id);
 743                 tcx.ensure().type_of(item.def_id);
 744                 tcx.ensure().predicates_of(item.def_id);
 745                 match item.kind {
 746                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 747                     hir::ForeignItemKind::Static(..) => {
 748                         let mut visitor = PlaceholderHirTyCollector::default();
 749                         visitor.visit_foreign_item(item);
 750                         placeholder_type_error(
 751                             tcx,
 752                             None,
 753                             &[],
 754                             visitor.0,
 755                             false,
 756                             None,
 757                             "static variable",
 758                         );
 759                     }
 760                     _ => (),
 761                 }
 762             }
 763         }
 764         hir::ItemKind::Enum(ref enum_definition, _) => {
 765             tcx.ensure().generics_of(def_id);
 766             tcx.ensure().type_of(def_id);
 767             tcx.ensure().predicates_of(def_id);
 768             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 769         }
 770         hir::ItemKind::Impl { .. } => {
 771             tcx.ensure().generics_of(def_id);
 772             tcx.ensure().type_of(def_id);
 773             tcx.ensure().impl_trait_ref(def_id);
 774             tcx.ensure().predicates_of(def_id);
 775         }
 776         hir::ItemKind::Trait(..) => {
 777             tcx.ensure().generics_of(def_id);
 778             tcx.ensure().trait_def(def_id);
 779             tcx.at(it.span).super_predicates_of(def_id);
 780             tcx.ensure().predicates_of(def_id);
 781         }
 782         hir::ItemKind::TraitAlias(..) => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.at(it.span).super_predicates_of(def_id);
 785             tcx.ensure().predicates_of(def_id);
 786         }
 787         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 788             tcx.ensure().generics_of(def_id);
 789             tcx.ensure().type_of(def_id);
 790             tcx.ensure().predicates_of(def_id);
 791
 792             for f in struct_def.fields() {
 793                 let def_id = tcx.hir().local_def_id(f.hir_id);
 794                 tcx.ensure().generics_of(def_id);
 795                 tcx.ensure().type_of(def_id);
 796                 tcx.ensure().predicates_of(def_id);
 797             }
 798
 799             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 800                 convert_variant_ctor(tcx, ctor_hir_id);
 801             }
 802         }
 803
 804         // Desugared from `impl Trait`, so visited by the function's return type.
 805         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 806             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 807             ..
 808         }) => {}
 809
 810         // Don't call `type_of` on opaque types, since that depends on type
 811         // checking function bodies. `check_item_type` ensures that it's called
 812         // instead.
 813         hir::ItemKind::OpaqueTy(..) => {
 814             tcx.ensure().generics_of(def_id);
 815             tcx.ensure().predicates_of(def_id);
 816             tcx.ensure().explicit_item_bounds(def_id);
 817         }
 818         hir::ItemKind::TyAlias(..)
 819         | hir::ItemKind::Static(..)
 820         | hir::ItemKind::Const(..)
 821         | hir::ItemKind::Fn(..) => {
 822             tcx.ensure().generics_of(def_id);
 823             tcx.ensure().type_of(def_id);
 824             tcx.ensure().predicates_of(def_id);
 825             match it.kind {
 826                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 827                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 828                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 829                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 830                     if let hir::TyKind::TraitObject(..) = ty.kind {
 831                         let mut visitor = PlaceholderHirTyCollector::default();
 832                         visitor.visit_item(it);
 833                         placeholder_type_error(
 834                             tcx,
 835                             None,
 836                             &[],
 837                             visitor.0,
 838                             false,
 839                             None,
 840                             it.kind.descr(),
 841                         );
 842                     }
 843                 }
 844                 _ => (),
 845             }
 846         }
 847     }
 848 }
 849
 850 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 851     let trait_item = tcx.hir().trait_item(trait_item_id);
 852     tcx.ensure().generics_of(trait_item_id.def_id);
 853
 854     match trait_item.kind {
 855         hir::TraitItemKind::Fn(..) => {
 856             tcx.ensure().type_of(trait_item_id.def_id);
 857             tcx.ensure().fn_sig(trait_item_id.def_id);
 858         }
 859
 860         hir::TraitItemKind::Const(.., Some(_)) => {
 861             tcx.ensure().type_of(trait_item_id.def_id);
 862         }
 863
 864         hir::TraitItemKind::Const(..) => {
 865             tcx.ensure().type_of(trait_item_id.def_id);
 866             // Account for `const C: _;`.
 867             let mut visitor = PlaceholderHirTyCollector::default();
 868             visitor.visit_trait_item(trait_item);
 869             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 870         }
 871
 872         hir::TraitItemKind::Type(_, Some(_)) => {
 873             tcx.ensure().item_bounds(trait_item_id.def_id);
 874             tcx.ensure().type_of(trait_item_id.def_id);
 875             // Account for `type T = _;`.
 876             let mut visitor = PlaceholderHirTyCollector::default();
 877             visitor.visit_trait_item(trait_item);
 878             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 879         }
 880
 881         hir::TraitItemKind::Type(_, None) => {
 882             tcx.ensure().item_bounds(trait_item_id.def_id);
 883             // #74612: Visit and try to find bad placeholders
 884             // even if there is no concrete type.
 885             let mut visitor = PlaceholderHirTyCollector::default();
 886             visitor.visit_trait_item(trait_item);
 887
 888             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 889         }
 890     };
 891
 892     tcx.ensure().predicates_of(trait_item_id.def_id);
 893 }
 894
 895 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 896     let def_id = impl_item_id.def_id;
 897     tcx.ensure().generics_of(def_id);
 898     tcx.ensure().type_of(def_id);
 899     tcx.ensure().predicates_of(def_id);
 900     let impl_item = tcx.hir().impl_item(impl_item_id);
 901     match impl_item.kind {
 902         hir::ImplItemKind::Fn(..) => {
 903             tcx.ensure().fn_sig(def_id);
 904         }
 905         hir::ImplItemKind::TyAlias(_) => {
 906             // Account for `type T = _;`
 907             let mut visitor = PlaceholderHirTyCollector::default();
 908             visitor.visit_impl_item(impl_item);
 909
 910             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 911         }
 912         hir::ImplItemKind::Const(..) => {}
 913     }
 914 }
 915
 916 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 917     let def_id = tcx.hir().local_def_id(ctor_id);
 918     tcx.ensure().generics_of(def_id);
 919     tcx.ensure().type_of(def_id);
 920     tcx.ensure().predicates_of(def_id);
 921 }
 922
 923 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 924     let def = tcx.adt_def(def_id);
 925     let repr_type = def.repr.discr_type();
 926     let initial = repr_type.initial_discriminant(tcx);
 927     let mut prev_discr = None::<Discr<'_>>;
 928
 929     // fill the discriminant values and field types
 930     for variant in variants {
 931         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 932         prev_discr = Some(
 933             if let Some(ref e) = variant.disr_expr {
 934                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 935                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 936             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 937                 Some(discr)
 938             } else {
 939                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 940                     .span_label(
 941                         variant.span,
 942                         format!("overflowed on value after {}", prev_discr.unwrap()),
 943                     )
 944                     .note(&format!(
 945                         "explicitly set `{} = {}` if that is desired outcome",
 946                         variant.ident, wrapped_discr
 947                     ))
 948                     .emit();
 949                 None
 950             }
 951             .unwrap_or(wrapped_discr),
 952         );
 953
 954         for f in variant.data.fields() {
 955             let def_id = tcx.hir().local_def_id(f.hir_id);
 956             tcx.ensure().generics_of(def_id);
 957             tcx.ensure().type_of(def_id);
 958             tcx.ensure().predicates_of(def_id);
 959         }
 960
 961         // Convert the ctor, if any. This also registers the variant as
 962         // an item.
 963         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 964             convert_variant_ctor(tcx, ctor_hir_id);
 965         }
 966     }
 967 }
 968
 969 fn convert_variant(
 970     tcx: TyCtxt<'_>,
 971     variant_did: Option<LocalDefId>,
 972     ctor_did: Option<LocalDefId>,
 973     ident: Ident,
 974     discr: ty::VariantDiscr,
 975     def: &hir::VariantData<'_>,
 976     adt_kind: ty::AdtKind,
 977     parent_did: LocalDefId,
 978 ) -> ty::VariantDef {
 979     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 980     let fields = def
 981         .fields()
 982         .iter()
 983         .map(|f| {
 984             let fid = tcx.hir().local_def_id(f.hir_id);
 985             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 986             if let Some(prev_span) = dup_span {
 987                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 988                     field_name: f.ident,
 989                     span: f.span,
 990                     prev_span,
 991                 });
 992             } else {
 993                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 994             }
 995
 996             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 997         })
 998         .collect();
 999     let recovered = match def {
1000         hir::VariantData::Struct(_, r) => *r,
1001         _ => false,
1002     };
1003     ty::VariantDef::new(
1004         ident,
1005         variant_did.map(LocalDefId::to_def_id),
1006         ctor_did.map(LocalDefId::to_def_id),
1007         discr,
1008         fields,
1009         CtorKind::from_hir(def),
1010         adt_kind,
1011         parent_did.to_def_id(),
1012         recovered,
1013         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1014             || variant_did.map_or(false, |variant_did| {
1015                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1016             }),
1017     )
1018 }
1019
1020 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1021     use rustc_hir::*;
1022
1023     let def_id = def_id.expect_local();
1024     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1025     let item = match tcx.hir().get(hir_id) {
1026         Node::Item(item) => item,
1027         _ => bug!(),
1028     };
1029
1030     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1031     let (kind, variants) = match item.kind {
1032         ItemKind::Enum(ref def, _) => {
1033             let mut distance_from_explicit = 0;
1034             let variants = def
1035                 .variants
1036                 .iter()
1037                 .map(|v| {
1038                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1039                     let ctor_did =
1040                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1041
1042                     let discr = if let Some(ref e) = v.disr_expr {
1043                         distance_from_explicit = 0;
1044                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1045                     } else {
1046                         ty::VariantDiscr::Relative(distance_from_explicit)
1047                     };
1048                     distance_from_explicit += 1;
1049
1050                     convert_variant(
1051                         tcx,
1052                         variant_did,
1053                         ctor_did,
1054                         v.ident,
1055                         discr,
1056                         &v.data,
1057                         AdtKind::Enum,
1058                         def_id,
1059                     )
1060                 })
1061                 .collect();
1062
1063             (AdtKind::Enum, variants)
1064         }
1065         ItemKind::Struct(ref def, _) => {
1066             let variant_did = None::<LocalDefId>;
1067             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1068
1069             let variants = std::iter::once(convert_variant(
1070                 tcx,
1071                 variant_did,
1072                 ctor_did,
1073                 item.ident,
1074                 ty::VariantDiscr::Relative(0),
1075                 def,
1076                 AdtKind::Struct,
1077                 def_id,
1078             ))
1079             .collect();
1080
1081             (AdtKind::Struct, variants)
1082         }
1083         ItemKind::Union(ref def, _) => {
1084             let variant_did = None;
1085             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1086
1087             let variants = std::iter::once(convert_variant(
1088                 tcx,
1089                 variant_did,
1090                 ctor_did,
1091                 item.ident,
1092                 ty::VariantDiscr::Relative(0),
1093                 def,
1094                 AdtKind::Union,
1095                 def_id,
1096             ))
1097             .collect();
1098
1099             (AdtKind::Union, variants)
1100         }
1101         _ => bug!(),
1102     };
1103     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1104 }
1105
1106 /// Ensures that the super-predicates of the trait with a `DefId`
1107 /// of `trait_def_id` are converted and stored. This also ensures that
1108 /// the transitive super-predicates are converted.
1109 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1110     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1111     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1112 }
1113
1114 /// Ensures that the super-predicates of the trait with a `DefId`
1115 /// of `trait_def_id` are converted and stored. This also ensures that
1116 /// the transitive super-predicates are converted.
1117 fn super_predicates_that_define_assoc_type(
1118     tcx: TyCtxt<'_>,
1119     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1120 ) -> ty::GenericPredicates<'_> {
1121     debug!(
1122         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1123         trait_def_id, assoc_name
1124     );
1125     if trait_def_id.is_local() {
1126         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1127         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1128
1129         let item = match tcx.hir().get(trait_hir_id) {
1130             Node::Item(item) => item,
1131             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1132         };
1133
1134         let (generics, bounds) = match item.kind {
1135             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1136             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1137             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1138         };
1139
1140         let icx = ItemCtxt::new(tcx, trait_def_id);
1141
1142         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1143         let self_param_ty = tcx.types.self_param;
1144         let superbounds1 = if let Some(assoc_name) = assoc_name {
1145             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1146                 &icx,
1147                 self_param_ty,
1148                 bounds,
1149                 assoc_name,
1150             )
1151         } else {
1152             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1153         };
1154
1155         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1156
1157         // Convert any explicit superbounds in the where-clause,
1158         // e.g., `trait Foo where Self: Bar`.
1159         // In the case of trait aliases, however, we include all bounds in the where-clause,
1160         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1161         // as one of its "superpredicates".
1162         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1163         let superbounds2 = icx.type_parameter_bounds_in_generics(
1164             generics,
1165             item.hir_id(),
1166             self_param_ty,
1167             OnlySelfBounds(!is_trait_alias),
1168             assoc_name,
1169         );
1170
1171         // Combine the two lists to form the complete set of superbounds:
1172         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1173
1174         // Now require that immediate supertraits are converted,
1175         // which will, in turn, reach indirect supertraits.
1176         if assoc_name.is_none() {
1177             // Now require that immediate supertraits are converted,
1178             // which will, in turn, reach indirect supertraits.
1179             for &(pred, span) in superbounds {
1180                 debug!("superbound: {:?}", pred);
1181                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1182                     tcx.at(span).super_predicates_of(bound.def_id());
1183                 }
1184             }
1185         }
1186
1187         ty::GenericPredicates { parent: None, predicates: superbounds }
1188     } else {
1189         // if `assoc_name` is None, then the query should've been redirected to an
1190         // external provider
1191         assert!(assoc_name.is_some());
1192         tcx.super_predicates_of(trait_def_id)
1193     }
1194 }
1195
1196 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1197     let item = tcx.hir().expect_item(def_id.expect_local());
1198
1199     let (is_auto, unsafety) = match item.kind {
1200         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1201         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1202         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1203     };
1204
1205     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1206     if paren_sugar && !tcx.features().unboxed_closures {
1207         tcx.sess
1208             .struct_span_err(
1209                 item.span,
1210                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1211                  which traits can use parenthetical notation",
1212             )
1213             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1214             .emit();
1215     }
1216
1217     let is_marker = tcx.has_attr(def_id, sym::marker);
1218     let skip_array_during_method_dispatch =
1219         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1220     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1221         ty::trait_def::TraitSpecializationKind::Marker
1222     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1223         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1224     } else {
1225         ty::trait_def::TraitSpecializationKind::None
1226     };
1227     let def_path_hash = tcx.def_path_hash(def_id);
1228     ty::TraitDef::new(
1229         def_id,
1230         unsafety,
1231         paren_sugar,
1232         is_auto,
1233         is_marker,
1234         skip_array_during_method_dispatch,
1235         spec_kind,
1236         def_path_hash,
1237     )
1238 }
1239
1240 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1241     struct LateBoundRegionsDetector<'tcx> {
1242         tcx: TyCtxt<'tcx>,
1243         outer_index: ty::DebruijnIndex,
1244         has_late_bound_regions: Option<Span>,
1245     }
1246
1247     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1248         type Map = intravisit::ErasedMap<'tcx>;
1249
1250         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1251             NestedVisitorMap::None
1252         }
1253
1254         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1255             if self.has_late_bound_regions.is_some() {
1256                 return;
1257             }
1258             match ty.kind {
1259                 hir::TyKind::BareFn(..) => {
1260                     self.outer_index.shift_in(1);
1261                     intravisit::walk_ty(self, ty);
1262                     self.outer_index.shift_out(1);
1263                 }
1264                 _ => intravisit::walk_ty(self, ty),
1265             }
1266         }
1267
1268         fn visit_poly_trait_ref(
1269             &mut self,
1270             tr: &'tcx hir::PolyTraitRef<'tcx>,
1271             m: hir::TraitBoundModifier,
1272         ) {
1273             if self.has_late_bound_regions.is_some() {
1274                 return;
1275             }
1276             self.outer_index.shift_in(1);
1277             intravisit::walk_poly_trait_ref(self, tr, m);
1278             self.outer_index.shift_out(1);
1279         }
1280
1281         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1282             if self.has_late_bound_regions.is_some() {
1283                 return;
1284             }
1285
1286             match self.tcx.named_region(lt.hir_id) {
1287                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1288                 Some(
1289                     rl::Region::LateBound(debruijn, _, _, _)
1290                     | rl::Region::LateBoundAnon(debruijn, _, _),
1291                 ) if debruijn < self.outer_index => {}
1292                 Some(
1293                     rl::Region::LateBound(..)
1294                     | rl::Region::LateBoundAnon(..)
1295                     | rl::Region::Free(..),
1296                 )
1297                 | None => {
1298                     self.has_late_bound_regions = Some(lt.span);
1299                 }
1300             }
1301         }
1302     }
1303
1304     fn has_late_bound_regions<'tcx>(
1305         tcx: TyCtxt<'tcx>,
1306         generics: &'tcx hir::Generics<'tcx>,
1307         decl: &'tcx hir::FnDecl<'tcx>,
1308     ) -> Option<Span> {
1309         let mut visitor = LateBoundRegionsDetector {
1310             tcx,
1311             outer_index: ty::INNERMOST,
1312             has_late_bound_regions: None,
1313         };
1314         for param in generics.params {
1315             if let GenericParamKind::Lifetime { .. } = param.kind {
1316                 if tcx.is_late_bound(param.hir_id) {
1317                     return Some(param.span);
1318                 }
1319             }
1320         }
1321         visitor.visit_fn_decl(decl);
1322         visitor.has_late_bound_regions
1323     }
1324
1325     match node {
1326         Node::TraitItem(item) => match item.kind {
1327             hir::TraitItemKind::Fn(ref sig, _) => {
1328                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1329             }
1330             _ => None,
1331         },
1332         Node::ImplItem(item) => match item.kind {
1333             hir::ImplItemKind::Fn(ref sig, _) => {
1334                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1335             }
1336             _ => None,
1337         },
1338         Node::ForeignItem(item) => match item.kind {
1339             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1340                 has_late_bound_regions(tcx, generics, fn_decl)
1341             }
1342             _ => None,
1343         },
1344         Node::Item(item) => match item.kind {
1345             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1346                 has_late_bound_regions(tcx, generics, sig.decl)
1347             }
1348             _ => None,
1349         },
1350         _ => None,
1351     }
1352 }
1353
1354 struct AnonConstInParamTyDetector {
1355     in_param_ty: bool,
1356     found_anon_const_in_param_ty: bool,
1357     ct: HirId,
1358 }
1359
1360 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1361     type Map = intravisit::ErasedMap<'v>;
1362
1363     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1364         NestedVisitorMap::None
1365     }
1366
1367     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1368         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1369             let prev = self.in_param_ty;
1370             self.in_param_ty = true;
1371             self.visit_ty(ty);
1372             self.in_param_ty = prev;
1373         }
1374     }
1375
1376     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1377         if self.in_param_ty && self.ct == c.hir_id {
1378             self.found_anon_const_in_param_ty = true;
1379         } else {
1380             intravisit::walk_anon_const(self, c)
1381         }
1382     }
1383 }
1384
1385 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1386     use rustc_hir::*;
1387
1388     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1389
1390     let node = tcx.hir().get(hir_id);
1391     let parent_def_id = match node {
1392         Node::ImplItem(_)
1393         | Node::TraitItem(_)
1394         | Node::Variant(_)
1395         | Node::Ctor(..)
1396         | Node::Field(_) => {
1397             let parent_id = tcx.hir().get_parent_item(hir_id);
1398             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1399         }
1400         // FIXME(#43408) always enable this once `lazy_normalization` is
1401         // stable enough and does not need a feature gate anymore.
1402         Node::AnonConst(_) => {
1403             let parent_id = tcx.hir().get_parent_item(hir_id);
1404             let parent_def_id = tcx.hir().local_def_id(parent_id);
1405
1406             let mut in_param_ty = false;
1407             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1408                 if let Some(generics) = node.generics() {
1409                     let mut visitor = AnonConstInParamTyDetector {
1410                         in_param_ty: false,
1411                         found_anon_const_in_param_ty: false,
1412                         ct: hir_id,
1413                     };
1414
1415                     visitor.visit_generics(generics);
1416                     in_param_ty = visitor.found_anon_const_in_param_ty;
1417                     break;
1418                 }
1419             }
1420
1421             if in_param_ty {
1422                 // We do not allow generic parameters in anon consts if we are inside
1423                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1424                 None
1425             } else if tcx.lazy_normalization() {
1426                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1427                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1428                     //
1429                     // struct Foo<const N: usize = { .. }>;
1430                     //        ^^^       ^          ^^^^^^ def id of this anon const
1431                     //        ^         ^ param_id
1432                     //        ^ parent_def_id
1433                     //
1434                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1435                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1436                     //
1437                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1438                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1439                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1440                     //
1441                     // We fix this by having this function return the parent's generics ourselves and truncating the
1442                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1443                     //
1444                     // For the above code example that means we want `substs: []`
1445                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1446                     // the def id of the `{ N + 1 }` anon const
1447                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1448                     //
1449                     // This has some implications for how we get the predicates available to the anon const
1450                     // see `explicit_predicates_of` for more information on this
1451                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1452                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1453                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1454                     // In the above example this would be .params[..N#0]
1455                     let params = generics.params[..param_def_idx as usize].to_owned();
1456                     let param_def_id_to_index =
1457                         params.iter().map(|param| (param.def_id, param.index)).collect();
1458
1459                     return ty::Generics {
1460                         // we set the parent of these generics to be our parent's parent so that we
1461                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1462                         // struct Foo<const N: usize, const M: usize = { ... }>;
1463                         parent: generics.parent,
1464                         parent_count: generics.parent_count,
1465                         params,
1466                         param_def_id_to_index,
1467                         has_self: generics.has_self,
1468                         has_late_bound_regions: generics.has_late_bound_regions,
1469                     };
1470                 }
1471
1472                 // HACK(eddyb) this provides the correct generics when
1473                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1474                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1475                 //
1476                 // Note that we do not supply the parent generics when using
1477                 // `min_const_generics`.
1478                 Some(parent_def_id.to_def_id())
1479             } else {
1480                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1481                 match parent_node {
1482                     // HACK(eddyb) this provides the correct generics for repeat
1483                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1484                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1485                     // as they shouldn't be able to cause query cycle errors.
1486                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1487                         if constant.hir_id() == hir_id =>
1488                     {
1489                         Some(parent_def_id.to_def_id())
1490                     }
1491                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1492                         if constant.hir_id == hir_id =>
1493                     {
1494                         Some(parent_def_id.to_def_id())
1495                     }
1496                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1497                         Some(tcx.typeck_root_def_id(def_id))
1498                     }
1499                     _ => None,
1500                 }
1501             }
1502         }
1503         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1504             Some(tcx.typeck_root_def_id(def_id))
1505         }
1506         Node::Item(item) => match item.kind {
1507             ItemKind::OpaqueTy(hir::OpaqueTy {
1508                 origin:
1509                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1510                 ..
1511             }) => Some(fn_def_id.to_def_id()),
1512             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1513                 let parent_id = tcx.hir().get_parent_item(hir_id);
1514                 assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1515                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1516                 // Opaque types are always nested within another item, and
1517                 // inherit the generics of the item.
1518                 Some(tcx.hir().local_def_id(parent_id).to_def_id())
1519             }
1520             _ => None,
1521         },
1522         _ => None,
1523     };
1524
1525     let mut opt_self = None;
1526     let mut allow_defaults = false;
1527
1528     let no_generics = hir::Generics::empty();
1529     let ast_generics = match node {
1530         Node::TraitItem(item) => &item.generics,
1531
1532         Node::ImplItem(item) => &item.generics,
1533
1534         Node::Item(item) => {
1535             match item.kind {
1536                 ItemKind::Fn(.., ref generics, _)
1537                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1538
1539                 ItemKind::TyAlias(_, ref generics)
1540                 | ItemKind::Enum(_, ref generics)
1541                 | ItemKind::Struct(_, ref generics)
1542                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1543                 | ItemKind::Union(_, ref generics) => {
1544                     allow_defaults = true;
1545                     generics
1546                 }
1547
1548                 ItemKind::Trait(_, _, ref generics, ..)
1549                 | ItemKind::TraitAlias(ref generics, ..) => {
1550                     // Add in the self type parameter.
1551                     //
1552                     // Something of a hack: use the node id for the trait, also as
1553                     // the node id for the Self type parameter.
1554                     let param_id = item.def_id;
1555
1556                     opt_self = Some(ty::GenericParamDef {
1557                         index: 0,
1558                         name: kw::SelfUpper,
1559                         def_id: param_id.to_def_id(),
1560                         pure_wrt_drop: false,
1561                         kind: ty::GenericParamDefKind::Type {
1562                             has_default: false,
1563                             object_lifetime_default: rl::Set1::Empty,
1564                             synthetic: false,
1565                         },
1566                     });
1567
1568                     allow_defaults = true;
1569                     generics
1570                 }
1571
1572                 _ => &no_generics,
1573             }
1574         }
1575
1576         Node::ForeignItem(item) => match item.kind {
1577             ForeignItemKind::Static(..) => &no_generics,
1578             ForeignItemKind::Fn(_, _, ref generics) => generics,
1579             ForeignItemKind::Type => &no_generics,
1580         },
1581
1582         _ => &no_generics,
1583     };
1584
1585     let has_self = opt_self.is_some();
1586     let mut parent_has_self = false;
1587     let mut own_start = has_self as u32;
1588     let parent_count = parent_def_id.map_or(0, |def_id| {
1589         let generics = tcx.generics_of(def_id);
1590         assert!(!has_self);
1591         parent_has_self = generics.has_self;
1592         own_start = generics.count() as u32;
1593         generics.parent_count + generics.params.len()
1594     });
1595
1596     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1597
1598     if let Some(opt_self) = opt_self {
1599         params.push(opt_self);
1600     }
1601
1602     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1603     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1604         name: param.name.ident().name,
1605         index: own_start + i as u32,
1606         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1607         pure_wrt_drop: param.pure_wrt_drop,
1608         kind: ty::GenericParamDefKind::Lifetime,
1609     }));
1610
1611     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1612
1613     // Now create the real type and const parameters.
1614     let type_start = own_start - has_self as u32 + params.len() as u32;
1615     let mut i = 0;
1616
1617     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1618         GenericParamKind::Lifetime { .. } => None,
1619         GenericParamKind::Type { ref default, synthetic, .. } => {
1620             if !allow_defaults && default.is_some() {
1621                 if !tcx.features().default_type_parameter_fallback {
1622                     tcx.struct_span_lint_hir(
1623                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1624                         param.hir_id,
1625                         param.span,
1626                         |lint| {
1627                             lint.build(
1628                                 "defaults for type parameters are only allowed in \
1629                                  `struct`, `enum`, `type`, or `trait` definitions",
1630                             )
1631                             .emit();
1632                         },
1633                     );
1634                 }
1635             }
1636
1637             let kind = ty::GenericParamDefKind::Type {
1638                 has_default: default.is_some(),
1639                 object_lifetime_default: object_lifetime_defaults
1640                     .as_ref()
1641                     .map_or(rl::Set1::Empty, |o| o[i]),
1642                 synthetic,
1643             };
1644
1645             let param_def = ty::GenericParamDef {
1646                 index: type_start + i as u32,
1647                 name: param.name.ident().name,
1648                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1649                 pure_wrt_drop: param.pure_wrt_drop,
1650                 kind,
1651             };
1652             i += 1;
1653             Some(param_def)
1654         }
1655         GenericParamKind::Const { default, .. } => {
1656             if !allow_defaults && default.is_some() {
1657                 tcx.sess.span_err(
1658                     param.span,
1659                     "defaults for const parameters are only allowed in \
1660                     `struct`, `enum`, `type`, or `trait` definitions",
1661                 );
1662             }
1663
1664             let param_def = ty::GenericParamDef {
1665                 index: type_start + i as u32,
1666                 name: param.name.ident().name,
1667                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1668                 pure_wrt_drop: param.pure_wrt_drop,
1669                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1670             };
1671             i += 1;
1672             Some(param_def)
1673         }
1674     }));
1675
1676     // provide junk type parameter defs - the only place that
1677     // cares about anything but the length is instantiation,
1678     // and we don't do that for closures.
1679     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1680         let dummy_args = if gen.is_some() {
1681             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1682         } else {
1683             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1684         };
1685
1686         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1687             index: type_start + i as u32,
1688             name: Symbol::intern(arg),
1689             def_id,
1690             pure_wrt_drop: false,
1691             kind: ty::GenericParamDefKind::Type {
1692                 has_default: false,
1693                 object_lifetime_default: rl::Set1::Empty,
1694                 synthetic: false,
1695             },
1696         }));
1697     }
1698
1699     // provide junk type parameter defs for const blocks.
1700     if let Node::AnonConst(_) = node {
1701         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1702         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1703             params.push(ty::GenericParamDef {
1704                 index: type_start,
1705                 name: Symbol::intern("<const_ty>"),
1706                 def_id,
1707                 pure_wrt_drop: false,
1708                 kind: ty::GenericParamDefKind::Type {
1709                     has_default: false,
1710                     object_lifetime_default: rl::Set1::Empty,
1711                     synthetic: false,
1712                 },
1713             });
1714         }
1715     }
1716
1717     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1718
1719     ty::Generics {
1720         parent: parent_def_id,
1721         parent_count,
1722         params,
1723         param_def_id_to_index,
1724         has_self: has_self || parent_has_self,
1725         has_late_bound_regions: has_late_bound_regions(tcx, node),
1726     }
1727 }
1728
1729 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1730     generic_args.iter().any(|arg| match arg {
1731         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1732         hir::GenericArg::Infer(_) => true,
1733         _ => false,
1734     })
1735 }
1736
1737 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1738 /// use inference to provide suggestions for the appropriate type if possible.
1739 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1740     use hir::TyKind::*;
1741     match &ty.kind {
1742         Infer => true,
1743         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1744         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1745         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1746         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1747         Path(hir::QPath::TypeRelative(ty, segment)) => {
1748             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1749         }
1750         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1751             ty_opt.map_or(false, is_suggestable_infer_ty)
1752                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1753         }
1754         _ => false,
1755     }
1756 }
1757
1758 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1759     if let hir::FnRetTy::Return(ty) = output {
1760         if is_suggestable_infer_ty(ty) {
1761             return Some(&*ty);
1762         }
1763     }
1764     None
1765 }
1766
1767 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1768     use rustc_hir::Node::*;
1769     use rustc_hir::*;
1770
1771     let def_id = def_id.expect_local();
1772     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1773
1774     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1775
1776     match tcx.hir().get(hir_id) {
1777         TraitItem(hir::TraitItem {
1778             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1779             ident,
1780             generics,
1781             ..
1782         })
1783         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1784         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1785             match get_infer_ret_ty(&sig.decl.output) {
1786                 Some(ty) => {
1787                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1788                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1789                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1790                         ty::ReErased => tcx.lifetimes.re_static,
1791                         _ => r,
1792                     });
1793                     let fn_sig = ty::Binder::dummy(fn_sig);
1794
1795                     let mut visitor = PlaceholderHirTyCollector::default();
1796                     visitor.visit_ty(ty);
1797                     let mut diag = bad_placeholder(tcx, "type", visitor.0, "return type");
1798                     let ret_ty = fn_sig.skip_binder().output();
1799                     if !ret_ty.references_error() {
1800                         if !ret_ty.is_closure() {
1801                             let ret_ty_str = match ret_ty.kind() {
1802                                 // Suggest a function pointer return type instead of a unique function definition
1803                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1804                                 // syntax)
1805                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1806                                 _ => ret_ty.to_string(),
1807                             };
1808                             diag.span_suggestion(
1809                                 ty.span,
1810                                 "replace with the correct return type",
1811                                 ret_ty_str,
1812                                 Applicability::MaybeIncorrect,
1813                             );
1814                         } else {
1815                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1816                             // to prevent the user from getting a papercut while trying to use the unique closure
1817                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1818                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1819                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1820                         }
1821                     }
1822                     diag.emit();
1823
1824                     fn_sig
1825                 }
1826                 None => <dyn AstConv<'_>>::ty_of_fn(
1827                     &icx,
1828                     hir_id,
1829                     sig.header.unsafety,
1830                     sig.header.abi,
1831                     sig.decl,
1832                     generics,
1833                     Some(ident.span),
1834                     None,
1835                 ),
1836             }
1837         }
1838
1839         TraitItem(hir::TraitItem {
1840             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1841             ident,
1842             generics,
1843             ..
1844         }) => <dyn AstConv<'_>>::ty_of_fn(
1845             &icx,
1846             hir_id,
1847             header.unsafety,
1848             header.abi,
1849             decl,
1850             generics,
1851             Some(ident.span),
1852             None,
1853         ),
1854
1855         ForeignItem(&hir::ForeignItem {
1856             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1857         }) => {
1858             let abi = tcx.hir().get_foreign_abi(hir_id);
1859             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1860         }
1861
1862         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1863             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1864             let inputs =
1865                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1866             ty::Binder::dummy(tcx.mk_fn_sig(
1867                 inputs,
1868                 ty,
1869                 false,
1870                 hir::Unsafety::Normal,
1871                 abi::Abi::Rust,
1872             ))
1873         }
1874
1875         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1876             // Closure signatures are not like other function
1877             // signatures and cannot be accessed through `fn_sig`. For
1878             // example, a closure signature excludes the `self`
1879             // argument. In any case they are embedded within the
1880             // closure type as part of the `ClosureSubsts`.
1881             //
1882             // To get the signature of a closure, you should use the
1883             // `sig` method on the `ClosureSubsts`:
1884             //
1885             //    substs.as_closure().sig(def_id, tcx)
1886             bug!(
1887                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1888             );
1889         }
1890
1891         x => {
1892             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1893         }
1894     }
1895 }
1896
1897 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1898     let icx = ItemCtxt::new(tcx, def_id);
1899     match tcx.hir().expect_item(def_id.expect_local()).kind {
1900         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1901             let selfty = tcx.type_of(def_id);
1902             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1903         }),
1904         _ => bug!(),
1905     }
1906 }
1907
1908 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1909     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1910     let item = tcx.hir().expect_item(def_id.expect_local());
1911     match &item.kind {
1912         hir::ItemKind::Impl(hir::Impl {
1913             polarity: hir::ImplPolarity::Negative(span),
1914             of_trait,
1915             ..
1916         }) => {
1917             if is_rustc_reservation {
1918                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1919                 tcx.sess.span_err(span, "reservation impls can't be negative");
1920             }
1921             ty::ImplPolarity::Negative
1922         }
1923         hir::ItemKind::Impl(hir::Impl {
1924             polarity: hir::ImplPolarity::Positive,
1925             of_trait: None,
1926             ..
1927         }) => {
1928             if is_rustc_reservation {
1929                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1930             }
1931             ty::ImplPolarity::Positive
1932         }
1933         hir::ItemKind::Impl(hir::Impl {
1934             polarity: hir::ImplPolarity::Positive,
1935             of_trait: Some(_),
1936             ..
1937         }) => {
1938             if is_rustc_reservation {
1939                 ty::ImplPolarity::Reservation
1940             } else {
1941                 ty::ImplPolarity::Positive
1942             }
1943         }
1944         item => bug!("impl_polarity: {:?} not an impl", item),
1945     }
1946 }
1947
1948 /// Returns the early-bound lifetimes declared in this generics
1949 /// listing. For anything other than fns/methods, this is just all
1950 /// the lifetimes that are declared. For fns or methods, we have to
1951 /// screen out those that do not appear in any where-clauses etc using
1952 /// `resolve_lifetime::early_bound_lifetimes`.
1953 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1954     tcx: TyCtxt<'tcx>,
1955     generics: &'a hir::Generics<'a>,
1956 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1957     generics.params.iter().filter(move |param| match param.kind {
1958         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1959         _ => false,
1960     })
1961 }
1962
1963 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1964 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1965 /// inferred constraints concerning which regions outlive other regions.
1966 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1967     debug!("predicates_defined_on({:?})", def_id);
1968     let mut result = tcx.explicit_predicates_of(def_id);
1969     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1970     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1971     if !inferred_outlives.is_empty() {
1972         debug!(
1973             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1974             def_id, inferred_outlives,
1975         );
1976         if result.predicates.is_empty() {
1977             result.predicates = inferred_outlives;
1978         } else {
1979             result.predicates = tcx
1980                 .arena
1981                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1982         }
1983     }
1984
1985     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1986     result
1987 }
1988
1989 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1990 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1991 /// `Self: Trait` predicates for traits.
1992 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1993     let mut result = tcx.predicates_defined_on(def_id);
1994
1995     if tcx.is_trait(def_id) {
1996         // For traits, add `Self: Trait` predicate. This is
1997         // not part of the predicates that a user writes, but it
1998         // is something that one must prove in order to invoke a
1999         // method or project an associated type.
2000         //
2001         // In the chalk setup, this predicate is not part of the
2002         // "predicates" for a trait item. But it is useful in
2003         // rustc because if you directly (e.g.) invoke a trait
2004         // method like `Trait::method(...)`, you must naturally
2005         // prove that the trait applies to the types that were
2006         // used, and adding the predicate into this list ensures
2007         // that this is done.
2008         //
2009         // We use a DUMMY_SP here as a way to signal trait bounds that come
2010         // from the trait itself that *shouldn't* be shown as the source of
2011         // an obligation and instead be skipped. Otherwise we'd use
2012         // `tcx.def_span(def_id);`
2013         let span = rustc_span::DUMMY_SP;
2014         result.predicates =
2015             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2016                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2017                 span,
2018             ))));
2019     }
2020     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2021     result
2022 }
2023
2024 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2025 /// N.B., this does not include any implied/inferred constraints.
2026 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2027     use rustc_hir::*;
2028
2029     debug!("explicit_predicates_of(def_id={:?})", def_id);
2030
2031     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2032     let node = tcx.hir().get(hir_id);
2033
2034     let mut is_trait = None;
2035     let mut is_default_impl_trait = None;
2036
2037     let icx = ItemCtxt::new(tcx, def_id);
2038
2039     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2040
2041     // We use an `IndexSet` to preserves order of insertion.
2042     // Preserving the order of insertion is important here so as not to break UI tests.
2043     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2044
2045     let ast_generics = match node {
2046         Node::TraitItem(item) => &item.generics,
2047
2048         Node::ImplItem(item) => &item.generics,
2049
2050         Node::Item(item) => {
2051             match item.kind {
2052                 ItemKind::Impl(ref impl_) => {
2053                     if impl_.defaultness.is_default() {
2054                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2055                     }
2056                     &impl_.generics
2057                 }
2058                 ItemKind::Fn(.., ref generics, _)
2059                 | ItemKind::TyAlias(_, ref generics)
2060                 | ItemKind::Enum(_, ref generics)
2061                 | ItemKind::Struct(_, ref generics)
2062                 | ItemKind::Union(_, ref generics) => generics,
2063
2064                 ItemKind::Trait(_, _, ref generics, ..) => {
2065                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2066                     generics
2067                 }
2068                 ItemKind::TraitAlias(ref generics, _) => {
2069                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2070                     generics
2071                 }
2072                 ItemKind::OpaqueTy(OpaqueTy {
2073                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2074                     ..
2075                 }) => {
2076                     // return-position impl trait
2077                     //
2078                     // We don't inherit predicates from the parent here:
2079                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2080                     // then the return type is `f::<'static, T>::{{opaque}}`.
2081                     //
2082                     // If we inherited the predicates of `f` then we would
2083                     // require that `T: 'static` to show that the return
2084                     // type is well-formed.
2085                     //
2086                     // The only way to have something with this opaque type
2087                     // is from the return type of the containing function,
2088                     // which will ensure that the function's predicates
2089                     // hold.
2090                     return ty::GenericPredicates { parent: None, predicates: &[] };
2091                 }
2092                 ItemKind::OpaqueTy(OpaqueTy {
2093                     ref generics,
2094                     origin: hir::OpaqueTyOrigin::TyAlias,
2095                     ..
2096                 }) => {
2097                     // type-alias impl trait
2098                     generics
2099                 }
2100
2101                 _ => NO_GENERICS,
2102             }
2103         }
2104
2105         Node::ForeignItem(item) => match item.kind {
2106             ForeignItemKind::Static(..) => NO_GENERICS,
2107             ForeignItemKind::Fn(_, _, ref generics) => generics,
2108             ForeignItemKind::Type => NO_GENERICS,
2109         },
2110
2111         _ => NO_GENERICS,
2112     };
2113
2114     let generics = tcx.generics_of(def_id);
2115     let parent_count = generics.parent_count as u32;
2116     let has_own_self = generics.has_self && parent_count == 0;
2117
2118     // Below we'll consider the bounds on the type parameters (including `Self`)
2119     // and the explicit where-clauses, but to get the full set of predicates
2120     // on a trait we need to add in the supertrait bounds and bounds found on
2121     // associated types.
2122     if let Some(_trait_ref) = is_trait {
2123         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2124     }
2125
2126     // In default impls, we can assume that the self type implements
2127     // the trait. So in:
2128     //
2129     //     default impl Foo for Bar { .. }
2130     //
2131     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2132     // (see below). Recall that a default impl is not itself an impl, but rather a
2133     // set of defaults that can be incorporated into another impl.
2134     if let Some(trait_ref) = is_default_impl_trait {
2135         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2136     }
2137
2138     // Collect the region predicates that were declared inline as
2139     // well. In the case of parameters declared on a fn or method, we
2140     // have to be careful to only iterate over early-bound regions.
2141     let mut index = parent_count + has_own_self as u32;
2142     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2143         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2144             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2145             index,
2146             name: param.name.ident().name,
2147         }));
2148         index += 1;
2149
2150         match param.kind {
2151             GenericParamKind::Lifetime { .. } => {
2152                 param.bounds.iter().for_each(|bound| match bound {
2153                     hir::GenericBound::Outlives(lt) => {
2154                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2155                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2156                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2157                     }
2158                     _ => bug!(),
2159                 });
2160             }
2161             _ => bug!(),
2162         }
2163     }
2164
2165     // Collect the predicates that were written inline by the user on each
2166     // type parameter (e.g., `<T: Foo>`).
2167     for param in ast_generics.params {
2168         match param.kind {
2169             // We already dealt with early bound lifetimes above.
2170             GenericParamKind::Lifetime { .. } => (),
2171             GenericParamKind::Type { .. } => {
2172                 let name = param.name.ident().name;
2173                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2174                 index += 1;
2175
2176                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2177                 // Params are implicitly sized unless a `?Sized` bound is found
2178                 <dyn AstConv<'_>>::add_implicitly_sized(
2179                     &icx,
2180                     &mut bounds,
2181                     param.bounds,
2182                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2183                     param.span,
2184                 );
2185                 predicates.extend(bounds.predicates(tcx, param_ty));
2186             }
2187             GenericParamKind::Const { .. } => {
2188                 // Bounds on const parameters are currently not possible.
2189                 debug_assert!(param.bounds.is_empty());
2190                 index += 1;
2191             }
2192         }
2193     }
2194
2195     // Add in the bounds that appear in the where-clause.
2196     let where_clause = &ast_generics.where_clause;
2197     for predicate in where_clause.predicates {
2198         match predicate {
2199             hir::WherePredicate::BoundPredicate(bound_pred) => {
2200                 let ty = icx.to_ty(bound_pred.bounded_ty);
2201                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2202
2203                 // Keep the type around in a dummy predicate, in case of no bounds.
2204                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2205                 // is still checked for WF.
2206                 if bound_pred.bounds.is_empty() {
2207                     if let ty::Param(_) = ty.kind() {
2208                         // This is a `where T:`, which can be in the HIR from the
2209                         // transformation that moves `?Sized` to `T`'s declaration.
2210                         // We can skip the predicate because type parameters are
2211                         // trivially WF, but also we *should*, to avoid exposing
2212                         // users who never wrote `where Type:,` themselves, to
2213                         // compiler/tooling bugs from not handling WF predicates.
2214                     } else {
2215                         let span = bound_pred.bounded_ty.span;
2216                         let re_root_empty = tcx.lifetimes.re_root_empty;
2217                         let predicate = ty::Binder::bind_with_vars(
2218                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2219                                 ty,
2220                                 re_root_empty,
2221                             )),
2222                             bound_vars,
2223                         );
2224                         predicates.insert((predicate.to_predicate(tcx), span));
2225                     }
2226                 }
2227
2228                 let mut bounds = Bounds::default();
2229                 <dyn AstConv<'_>>::add_bounds(
2230                     &icx,
2231                     ty,
2232                     bound_pred.bounds.iter(),
2233                     &mut bounds,
2234                     bound_vars,
2235                 );
2236                 predicates.extend(bounds.predicates(tcx, ty));
2237             }
2238
2239             hir::WherePredicate::RegionPredicate(region_pred) => {
2240                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2241                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2242                     let (r2, span) = match bound {
2243                         hir::GenericBound::Outlives(lt) => {
2244                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2245                         }
2246                         _ => bug!(),
2247                     };
2248                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2249                         ty::OutlivesPredicate(r1, r2),
2250                     ))
2251                     .to_predicate(icx.tcx);
2252
2253                     (pred, span)
2254                 }))
2255             }
2256
2257             hir::WherePredicate::EqPredicate(..) => {
2258                 // FIXME(#20041)
2259             }
2260         }
2261     }
2262
2263     if tcx.features().generic_const_exprs {
2264         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2265     }
2266
2267     let mut predicates: Vec<_> = predicates.into_iter().collect();
2268
2269     // Subtle: before we store the predicates into the tcx, we
2270     // sort them so that predicates like `T: Foo<Item=U>` come
2271     // before uses of `U`.  This avoids false ambiguity errors
2272     // in trait checking. See `setup_constraining_predicates`
2273     // for details.
2274     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2275         let self_ty = tcx.type_of(def_id);
2276         let trait_ref = tcx.impl_trait_ref(def_id);
2277         cgp::setup_constraining_predicates(
2278             tcx,
2279             &mut predicates,
2280             trait_ref,
2281             &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref),
2282         );
2283     }
2284
2285     let result = ty::GenericPredicates {
2286         parent: generics.parent,
2287         predicates: tcx.arena.alloc_from_iter(predicates),
2288     };
2289     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2290     result
2291 }
2292
2293 fn const_evaluatable_predicates_of<'tcx>(
2294     tcx: TyCtxt<'tcx>,
2295     def_id: LocalDefId,
2296 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2297     struct ConstCollector<'tcx> {
2298         tcx: TyCtxt<'tcx>,
2299         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2300     }
2301
2302     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2303         type Map = Map<'tcx>;
2304
2305         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2306             intravisit::NestedVisitorMap::None
2307         }
2308
2309         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2310             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2311             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2312             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2313                 assert_eq!(uv.promoted, None);
2314                 let span = self.tcx.hir().span(c.hir_id);
2315                 self.preds.insert((
2316                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2317                         .to_predicate(self.tcx),
2318                     span,
2319                 ));
2320             }
2321         }
2322
2323         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2324             // Do not look into const param defaults,
2325             // these get checked when they are actually instantiated.
2326             //
2327             // We do not want the following to error:
2328             //
2329             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2330             //     struct Bar<const N: usize>(Foo<N, 3>);
2331         }
2332     }
2333
2334     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2335     let node = tcx.hir().get(hir_id);
2336
2337     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2338     if let hir::Node::Item(item) = node {
2339         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2340             if let Some(of_trait) = &impl_.of_trait {
2341                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2342                 collector.visit_trait_ref(of_trait);
2343             }
2344
2345             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2346             collector.visit_ty(impl_.self_ty);
2347         }
2348     }
2349
2350     if let Some(generics) = node.generics() {
2351         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2352         collector.visit_generics(generics);
2353     }
2354
2355     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2356         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2357         collector.visit_fn_decl(fn_sig.decl);
2358     }
2359     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2360
2361     collector.preds
2362 }
2363
2364 fn trait_explicit_predicates_and_bounds(
2365     tcx: TyCtxt<'_>,
2366     def_id: LocalDefId,
2367 ) -> ty::GenericPredicates<'_> {
2368     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2369     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2370 }
2371
2372 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2373     let def_kind = tcx.def_kind(def_id);
2374     if let DefKind::Trait = def_kind {
2375         // Remove bounds on associated types from the predicates, they will be
2376         // returned by `explicit_item_bounds`.
2377         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2378         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2379
2380         let is_assoc_item_ty = |ty: Ty<'_>| {
2381             // For a predicate from a where clause to become a bound on an
2382             // associated type:
2383             // * It must use the identity substs of the item.
2384             //     * Since any generic parameters on the item are not in scope,
2385             //       this means that the item is not a GAT, and its identity
2386             //       substs are the same as the trait's.
2387             // * It must be an associated type for this trait (*not* a
2388             //   supertrait).
2389             if let ty::Projection(projection) = ty.kind() {
2390                 projection.substs == trait_identity_substs
2391                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2392             } else {
2393                 false
2394             }
2395         };
2396
2397         let predicates: Vec<_> = predicates_and_bounds
2398             .predicates
2399             .iter()
2400             .copied()
2401             .filter(|(pred, _)| match pred.kind().skip_binder() {
2402                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2403                 ty::PredicateKind::Projection(proj) => {
2404                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2405                 }
2406                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2407                 _ => true,
2408             })
2409             .collect();
2410         if predicates.len() == predicates_and_bounds.predicates.len() {
2411             predicates_and_bounds
2412         } else {
2413             ty::GenericPredicates {
2414                 parent: predicates_and_bounds.parent,
2415                 predicates: tcx.arena.alloc_slice(&predicates),
2416             }
2417         }
2418     } else {
2419         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2420             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2421             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2422                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2423                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2424                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2425                 //
2426                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2427                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2428                 //        ^^^                                             explicit_predicates_of on
2429                 //        parent item we dont have set as the
2430                 //        parent of generics returned by `generics_of`
2431                 //
2432                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2433                 let item_id = tcx.hir().get_parent_item(hir_id);
2434                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2435                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2436                 return tcx.explicit_predicates_of(item_def_id);
2437             }
2438         }
2439         gather_explicit_predicates_of(tcx, def_id)
2440     }
2441 }
2442
2443 /// Converts a specific `GenericBound` from the AST into a set of
2444 /// predicates that apply to the self type. A vector is returned
2445 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2446 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2447 /// and `<T as Bar>::X == i32`).
2448 fn predicates_from_bound<'tcx>(
2449     astconv: &dyn AstConv<'tcx>,
2450     param_ty: Ty<'tcx>,
2451     bound: &'tcx hir::GenericBound<'tcx>,
2452     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2453 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2454     let mut bounds = Bounds::default();
2455     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2456     bounds.predicates(astconv.tcx(), param_ty)
2457 }
2458
2459 fn compute_sig_of_foreign_fn_decl<'tcx>(
2460     tcx: TyCtxt<'tcx>,
2461     def_id: DefId,
2462     decl: &'tcx hir::FnDecl<'tcx>,
2463     abi: abi::Abi,
2464     ident: Ident,
2465 ) -> ty::PolyFnSig<'tcx> {
2466     let unsafety = if abi == abi::Abi::RustIntrinsic {
2467         intrinsic_operation_unsafety(tcx.item_name(def_id))
2468     } else {
2469         hir::Unsafety::Unsafe
2470     };
2471     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2472     let fty = <dyn AstConv<'_>>::ty_of_fn(
2473         &ItemCtxt::new(tcx, def_id),
2474         hir_id,
2475         unsafety,
2476         abi,
2477         decl,
2478         &hir::Generics::empty(),
2479         Some(ident.span),
2480         None,
2481     );
2482
2483     // Feature gate SIMD types in FFI, since I am not sure that the
2484     // ABIs are handled at all correctly. -huonw
2485     if abi != abi::Abi::RustIntrinsic
2486         && abi != abi::Abi::PlatformIntrinsic
2487         && !tcx.features().simd_ffi
2488     {
2489         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2490             if ty.is_simd() {
2491                 let snip = tcx
2492                     .sess
2493                     .source_map()
2494                     .span_to_snippet(ast_ty.span)
2495                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2496                 tcx.sess
2497                     .struct_span_err(
2498                         ast_ty.span,
2499                         &format!(
2500                             "use of SIMD type{} in FFI is highly experimental and \
2501                              may result in invalid code",
2502                             snip
2503                         ),
2504                     )
2505                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2506                     .emit();
2507             }
2508         };
2509         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2510             check(input, ty)
2511         }
2512         if let hir::FnRetTy::Return(ref ty) = decl.output {
2513             check(ty, fty.output().skip_binder())
2514         }
2515     }
2516
2517     fty
2518 }
2519
2520 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2521     match tcx.hir().get_if_local(def_id) {
2522         Some(Node::ForeignItem(..)) => true,
2523         Some(_) => false,
2524         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2525     }
2526 }
2527
2528 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2529     match tcx.hir().get_if_local(def_id) {
2530         Some(
2531             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2532             | Node::ForeignItem(&hir::ForeignItem {
2533                 kind: hir::ForeignItemKind::Static(_, mutbl),
2534                 ..
2535             }),
2536         ) => Some(mutbl),
2537         Some(_) => None,
2538         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2539     }
2540 }
2541
2542 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2543     match tcx.hir().get_if_local(def_id) {
2544         Some(Node::Expr(&rustc_hir::Expr {
2545             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2546             ..
2547         })) => tcx.hir().body(body_id).generator_kind(),
2548         Some(_) => None,
2549         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2550     }
2551 }
2552
2553 fn from_target_feature(
2554     tcx: TyCtxt<'_>,
2555     id: DefId,
2556     attr: &ast::Attribute,
2557     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2558     target_features: &mut Vec<Symbol>,
2559 ) {
2560     let list = match attr.meta_item_list() {
2561         Some(list) => list,
2562         None => return,
2563     };
2564     let bad_item = |span| {
2565         let msg = "malformed `target_feature` attribute input";
2566         let code = "enable = \"..\"".to_owned();
2567         tcx.sess
2568             .struct_span_err(span, msg)
2569             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2570             .emit();
2571     };
2572     let rust_features = tcx.features();
2573     for item in list {
2574         // Only `enable = ...` is accepted in the meta-item list.
2575         if !item.has_name(sym::enable) {
2576             bad_item(item.span());
2577             continue;
2578         }
2579
2580         // Must be of the form `enable = "..."` (a string).
2581         let value = match item.value_str() {
2582             Some(value) => value,
2583             None => {
2584                 bad_item(item.span());
2585                 continue;
2586             }
2587         };
2588
2589         // We allow comma separation to enable multiple features.
2590         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2591             let feature_gate = match supported_target_features.get(feature) {
2592                 Some(g) => g,
2593                 None => {
2594                     let msg =
2595                         format!("the feature named `{}` is not valid for this target", feature);
2596                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2597                     err.span_label(
2598                         item.span(),
2599                         format!("`{}` is not valid for this target", feature),
2600                     );
2601                     if let Some(stripped) = feature.strip_prefix('+') {
2602                         let valid = supported_target_features.contains_key(stripped);
2603                         if valid {
2604                             err.help("consider removing the leading `+` in the feature name");
2605                         }
2606                     }
2607                     err.emit();
2608                     return None;
2609                 }
2610             };
2611
2612             // Only allow features whose feature gates have been enabled.
2613             let allowed = match feature_gate.as_ref().copied() {
2614                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2615                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2616                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2617                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2618                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2619                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2620                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2621                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2622                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2623                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2624                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2625                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2626                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2627                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2628                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2629                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2630                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2631                 Some(name) => bug!("unknown target feature gate {}", name),
2632                 None => true,
2633             };
2634             if !allowed && id.is_local() {
2635                 feature_err(
2636                     &tcx.sess.parse_sess,
2637                     feature_gate.unwrap(),
2638                     item.span(),
2639                     &format!("the target feature `{}` is currently unstable", feature),
2640                 )
2641                 .emit();
2642             }
2643             Some(Symbol::intern(feature))
2644         }));
2645     }
2646 }
2647
2648 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2649     use rustc_middle::mir::mono::Linkage::*;
2650
2651     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2652     // applicable to variable declarations and may not really make sense for
2653     // Rust code in the first place but allow them anyway and trust that the
2654     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2655     // up in the future.
2656     //
2657     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2658     // and don't have to be, LLVM treats them as no-ops.
2659     match name {
2660         "appending" => Appending,
2661         "available_externally" => AvailableExternally,
2662         "common" => Common,
2663         "extern_weak" => ExternalWeak,
2664         "external" => External,
2665         "internal" => Internal,
2666         "linkonce" => LinkOnceAny,
2667         "linkonce_odr" => LinkOnceODR,
2668         "private" => Private,
2669         "weak" => WeakAny,
2670         "weak_odr" => WeakODR,
2671         _ => {
2672             let span = tcx.hir().span_if_local(def_id);
2673             if let Some(span) = span {
2674                 tcx.sess.span_fatal(span, "invalid linkage specified")
2675             } else {
2676                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2677             }
2678         }
2679     }
2680 }
2681
2682 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2683     let attrs = tcx.get_attrs(id);
2684
2685     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2686     if tcx.should_inherit_track_caller(id) {
2687         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2688     }
2689
2690     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2691     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2692         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2693             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2694         }
2695     }
2696
2697     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2698
2699     let mut inline_span = None;
2700     let mut link_ordinal_span = None;
2701     let mut no_sanitize_span = None;
2702     for attr in attrs.iter() {
2703         if attr.has_name(sym::cold) {
2704             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2705         } else if attr.has_name(sym::rustc_allocator) {
2706             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2707         } else if attr.has_name(sym::ffi_returns_twice) {
2708             if tcx.is_foreign_item(id) {
2709                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2710             } else {
2711                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2712                 struct_span_err!(
2713                     tcx.sess,
2714                     attr.span,
2715                     E0724,
2716                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2717                 )
2718                 .emit();
2719             }
2720         } else if attr.has_name(sym::ffi_pure) {
2721             if tcx.is_foreign_item(id) {
2722                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2723                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2724                     struct_span_err!(
2725                         tcx.sess,
2726                         attr.span,
2727                         E0757,
2728                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2729                     )
2730                     .emit();
2731                 } else {
2732                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2733                 }
2734             } else {
2735                 // `#[ffi_pure]` is only allowed on foreign functions
2736                 struct_span_err!(
2737                     tcx.sess,
2738                     attr.span,
2739                     E0755,
2740                     "`#[ffi_pure]` may only be used on foreign functions"
2741                 )
2742                 .emit();
2743             }
2744         } else if attr.has_name(sym::ffi_const) {
2745             if tcx.is_foreign_item(id) {
2746                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2747             } else {
2748                 // `#[ffi_const]` is only allowed on foreign functions
2749                 struct_span_err!(
2750                     tcx.sess,
2751                     attr.span,
2752                     E0756,
2753                     "`#[ffi_const]` may only be used on foreign functions"
2754                 )
2755                 .emit();
2756             }
2757         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2758             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2759         } else if attr.has_name(sym::naked) {
2760             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2761         } else if attr.has_name(sym::no_mangle) {
2762             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2763         } else if attr.has_name(sym::no_coverage) {
2764             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2765         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2766             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2767         } else if attr.has_name(sym::used) {
2768             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2769         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2770             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2771                 struct_span_err!(
2772                     tcx.sess,
2773                     attr.span,
2774                     E0776,
2775                     "`#[cmse_nonsecure_entry]` requires C ABI"
2776                 )
2777                 .emit();
2778             }
2779             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2780                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2781                     .emit();
2782             }
2783             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2784         } else if attr.has_name(sym::thread_local) {
2785             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2786         } else if attr.has_name(sym::track_caller) {
2787             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2788                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2789                     .emit();
2790             }
2791             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2792                 feature_err(
2793                     &tcx.sess.parse_sess,
2794                     sym::closure_track_caller,
2795                     attr.span,
2796                     "`#[track_caller]` on closures is currently unstable",
2797                 )
2798                 .emit();
2799             }
2800             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2801         } else if attr.has_name(sym::export_name) {
2802             if let Some(s) = attr.value_str() {
2803                 if s.as_str().contains('\0') {
2804                     // `#[export_name = ...]` will be converted to a null-terminated string,
2805                     // so it may not contain any null characters.
2806                     struct_span_err!(
2807                         tcx.sess,
2808                         attr.span,
2809                         E0648,
2810                         "`export_name` may not contain null characters"
2811                     )
2812                     .emit();
2813                 }
2814                 codegen_fn_attrs.export_name = Some(s);
2815             }
2816         } else if attr.has_name(sym::target_feature) {
2817             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2818                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2819                     // The `#[target_feature]` attribute is allowed on
2820                     // WebAssembly targets on all functions, including safe
2821                     // ones. Other targets require that `#[target_feature]` is
2822                     // only applied to unsafe funtions (pending the
2823                     // `target_feature_11` feature) because on most targets
2824                     // execution of instructions that are not supported is
2825                     // considered undefined behavior. For WebAssembly which is a
2826                     // 100% safe target at execution time it's not possible to
2827                     // execute undefined instructions, and even if a future
2828                     // feature was added in some form for this it would be a
2829                     // deterministic trap. There is no undefined behavior when
2830                     // executing WebAssembly so `#[target_feature]` is allowed
2831                     // on safe functions (but again, only for WebAssembly)
2832                     //
2833                     // Note that this is also allowed if `actually_rustdoc` so
2834                     // if a target is documenting some wasm-specific code then
2835                     // it's not spuriously denied.
2836                 } else if !tcx.features().target_feature_11 {
2837                     let mut err = feature_err(
2838                         &tcx.sess.parse_sess,
2839                         sym::target_feature_11,
2840                         attr.span,
2841                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2842                     );
2843                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2844                     err.emit();
2845                 } else if let Some(local_id) = id.as_local() {
2846                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2847                 }
2848             }
2849             from_target_feature(
2850                 tcx,
2851                 id,
2852                 attr,
2853                 supported_target_features,
2854                 &mut codegen_fn_attrs.target_features,
2855             );
2856         } else if attr.has_name(sym::linkage) {
2857             if let Some(val) = attr.value_str() {
2858                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2859             }
2860         } else if attr.has_name(sym::link_section) {
2861             if let Some(val) = attr.value_str() {
2862                 if val.as_str().bytes().any(|b| b == 0) {
2863                     let msg = format!(
2864                         "illegal null byte in link_section \
2865                          value: `{}`",
2866                         &val
2867                     );
2868                     tcx.sess.span_err(attr.span, &msg);
2869                 } else {
2870                     codegen_fn_attrs.link_section = Some(val);
2871                 }
2872             }
2873         } else if attr.has_name(sym::link_name) {
2874             codegen_fn_attrs.link_name = attr.value_str();
2875         } else if attr.has_name(sym::link_ordinal) {
2876             link_ordinal_span = Some(attr.span);
2877             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2878                 codegen_fn_attrs.link_ordinal = ordinal;
2879             }
2880         } else if attr.has_name(sym::no_sanitize) {
2881             no_sanitize_span = Some(attr.span);
2882             if let Some(list) = attr.meta_item_list() {
2883                 for item in list.iter() {
2884                     if item.has_name(sym::address) {
2885                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2886                     } else if item.has_name(sym::cfi) {
2887                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2888                     } else if item.has_name(sym::memory) {
2889                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2890                     } else if item.has_name(sym::thread) {
2891                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2892                     } else if item.has_name(sym::hwaddress) {
2893                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2894                     } else {
2895                         tcx.sess
2896                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2897                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2898                             .emit();
2899                     }
2900                 }
2901             }
2902         } else if attr.has_name(sym::instruction_set) {
2903             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2904                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2905                     [NestedMetaItem::MetaItem(set)] => {
2906                         let segments =
2907                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2908                         match segments.as_slice() {
2909                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2910                                 if !tcx.sess.target.has_thumb_interworking {
2911                                     struct_span_err!(
2912                                         tcx.sess.diagnostic(),
2913                                         attr.span,
2914                                         E0779,
2915                                         "target does not support `#[instruction_set]`"
2916                                     )
2917                                     .emit();
2918                                     None
2919                                 } else if segments[1] == sym::a32 {
2920                                     Some(InstructionSetAttr::ArmA32)
2921                                 } else if segments[1] == sym::t32 {
2922                                     Some(InstructionSetAttr::ArmT32)
2923                                 } else {
2924                                     unreachable!()
2925                                 }
2926                             }
2927                             _ => {
2928                                 struct_span_err!(
2929                                     tcx.sess.diagnostic(),
2930                                     attr.span,
2931                                     E0779,
2932                                     "invalid instruction set specified",
2933                                 )
2934                                 .emit();
2935                                 None
2936                             }
2937                         }
2938                     }
2939                     [] => {
2940                         struct_span_err!(
2941                             tcx.sess.diagnostic(),
2942                             attr.span,
2943                             E0778,
2944                             "`#[instruction_set]` requires an argument"
2945                         )
2946                         .emit();
2947                         None
2948                     }
2949                     _ => {
2950                         struct_span_err!(
2951                             tcx.sess.diagnostic(),
2952                             attr.span,
2953                             E0779,
2954                             "cannot specify more than one instruction set"
2955                         )
2956                         .emit();
2957                         None
2958                     }
2959                 },
2960                 _ => {
2961                     struct_span_err!(
2962                         tcx.sess.diagnostic(),
2963                         attr.span,
2964                         E0778,
2965                         "must specify an instruction set"
2966                     )
2967                     .emit();
2968                     None
2969                 }
2970             };
2971         } else if attr.has_name(sym::repr) {
2972             codegen_fn_attrs.alignment = match attr.meta_item_list() {
2973                 Some(items) => match items.as_slice() {
2974                     [item] => match item.name_value_literal() {
2975                         Some((sym::align, literal)) => {
2976                             let alignment = rustc_attr::parse_alignment(&literal.kind);
2977
2978                             match alignment {
2979                                 Ok(align) => Some(align),
2980                                 Err(msg) => {
2981                                     struct_span_err!(
2982                                         tcx.sess.diagnostic(),
2983                                         attr.span,
2984                                         E0589,
2985                                         "invalid `repr(align)` attribute: {}",
2986                                         msg
2987                                     )
2988                                     .emit();
2989
2990                                     None
2991                                 }
2992                             }
2993                         }
2994                         _ => None,
2995                     },
2996                     [] => None,
2997                     _ => None,
2998                 },
2999                 None => None,
3000             };
3001         }
3002     }
3003
3004     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3005         if !attr.has_name(sym::inline) {
3006             return ia;
3007         }
3008         match attr.meta_kind() {
3009             Some(MetaItemKind::Word) => InlineAttr::Hint,
3010             Some(MetaItemKind::List(ref items)) => {
3011                 inline_span = Some(attr.span);
3012                 if items.len() != 1 {
3013                     struct_span_err!(
3014                         tcx.sess.diagnostic(),
3015                         attr.span,
3016                         E0534,
3017                         "expected one argument"
3018                     )
3019                     .emit();
3020                     InlineAttr::None
3021                 } else if list_contains_name(&items, sym::always) {
3022                     InlineAttr::Always
3023                 } else if list_contains_name(&items, sym::never) {
3024                     InlineAttr::Never
3025                 } else {
3026                     struct_span_err!(
3027                         tcx.sess.diagnostic(),
3028                         items[0].span(),
3029                         E0535,
3030                         "invalid argument"
3031                     )
3032                     .emit();
3033
3034                     InlineAttr::None
3035                 }
3036             }
3037             Some(MetaItemKind::NameValue(_)) => ia,
3038             None => ia,
3039         }
3040     });
3041
3042     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3043         if !attr.has_name(sym::optimize) {
3044             return ia;
3045         }
3046         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3047         match attr.meta_kind() {
3048             Some(MetaItemKind::Word) => {
3049                 err(attr.span, "expected one argument");
3050                 ia
3051             }
3052             Some(MetaItemKind::List(ref items)) => {
3053                 inline_span = Some(attr.span);
3054                 if items.len() != 1 {
3055                     err(attr.span, "expected one argument");
3056                     OptimizeAttr::None
3057                 } else if list_contains_name(&items, sym::size) {
3058                     OptimizeAttr::Size
3059                 } else if list_contains_name(&items, sym::speed) {
3060                     OptimizeAttr::Speed
3061                 } else {
3062                     err(items[0].span(), "invalid argument");
3063                     OptimizeAttr::None
3064                 }
3065             }
3066             Some(MetaItemKind::NameValue(_)) => ia,
3067             None => ia,
3068         }
3069     });
3070
3071     // #73631: closures inherit `#[target_feature]` annotations
3072     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3073         let owner_id = tcx.parent(id).expect("closure should have a parent");
3074         codegen_fn_attrs
3075             .target_features
3076             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3077     }
3078
3079     // If a function uses #[target_feature] it can't be inlined into general
3080     // purpose functions as they wouldn't have the right target features
3081     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3082     // respected.
3083     if !codegen_fn_attrs.target_features.is_empty() {
3084         if codegen_fn_attrs.inline == InlineAttr::Always {
3085             if let Some(span) = inline_span {
3086                 tcx.sess.span_err(
3087                     span,
3088                     "cannot use `#[inline(always)]` with \
3089                      `#[target_feature]`",
3090                 );
3091             }
3092         }
3093     }
3094
3095     if !codegen_fn_attrs.no_sanitize.is_empty() {
3096         if codegen_fn_attrs.inline == InlineAttr::Always {
3097             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3098                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3099                 tcx.struct_span_lint_hir(
3100                     lint::builtin::INLINE_NO_SANITIZE,
3101                     hir_id,
3102                     no_sanitize_span,
3103                     |lint| {
3104                         lint.build("`no_sanitize` will have no effect after inlining")
3105                             .span_note(inline_span, "inlining requested here")
3106                             .emit();
3107                     },
3108                 )
3109             }
3110         }
3111     }
3112
3113     // Weak lang items have the same semantics as "std internal" symbols in the
3114     // sense that they're preserved through all our LTO passes and only
3115     // strippable by the linker.
3116     //
3117     // Additionally weak lang items have predetermined symbol names.
3118     if tcx.is_weak_lang_item(id) {
3119         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3120     }
3121     let check_name = |attr: &Attribute, sym| attr.has_name(sym);
3122     if let Some(name) = weak_lang_items::link_name(check_name, attrs) {
3123         codegen_fn_attrs.export_name = Some(name);
3124         codegen_fn_attrs.link_name = Some(name);
3125     }
3126     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3127
3128     // Internal symbols to the standard library all have no_mangle semantics in
3129     // that they have defined symbol names present in the function name. This
3130     // also applies to weak symbols where they all have known symbol names.
3131     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3132         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3133     }
3134
3135     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3136     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3137     // intrinsic functions.
3138     if let Some(name) = &codegen_fn_attrs.link_name {
3139         if name.as_str().starts_with("llvm.") {
3140             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3141         }
3142     }
3143
3144     codegen_fn_attrs
3145 }
3146
3147 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3148 /// applied to the method prototype.
3149 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3150     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3151         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3152             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3153                 if let Some(trait_item) = tcx
3154                     .associated_items(trait_def_id)
3155                     .filter_by_name_unhygienic(impl_item.ident.name)
3156                     .find(move |trait_item| {
3157                         trait_item.kind == ty::AssocKind::Fn
3158                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3159                     })
3160                 {
3161                     return tcx
3162                         .codegen_fn_attrs(trait_item.def_id)
3163                         .flags
3164                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3165                 }
3166             }
3167         }
3168     }
3169
3170     false
3171 }
3172
3173 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3174     use rustc_ast::{Lit, LitIntType, LitKind};
3175     let meta_item_list = attr.meta_item_list();
3176     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3177     let sole_meta_list = match meta_item_list {
3178         Some([item]) => item.literal(),
3179         Some(_) => {
3180             tcx.sess
3181                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3182                 .note("the attribute requires exactly one argument")
3183                 .emit();
3184             return None;
3185         }
3186         _ => None,
3187     };
3188     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3189         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3190         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3191         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3192         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3193         //
3194         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3195         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3196         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3197         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3198         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3199         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3200         // about LINK.EXE failing.)
3201         if *ordinal <= u16::MAX as u128 {
3202             Some(*ordinal as u16)
3203         } else {
3204             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3205             tcx.sess
3206                 .struct_span_err(attr.span, &msg)
3207                 .note("the value may not exceed `u16::MAX`")
3208                 .emit();
3209             None
3210         }
3211     } else {
3212         tcx.sess
3213             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3214             .note("an unsuffixed integer value, e.g., `1`, is expected")
3215             .emit();
3216         None
3217     }
3218 }
3219
3220 fn check_link_name_xor_ordinal(
3221     tcx: TyCtxt<'_>,
3222     codegen_fn_attrs: &CodegenFnAttrs,
3223     inline_span: Option<Span>,
3224 ) {
3225     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3226         return;
3227     }
3228     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3229     if let Some(span) = inline_span {
3230         tcx.sess.span_err(span, msg);
3231     } else {
3232         tcx.sess.err(msg);
3233     }
3234 }
3235
3236 /// Checks the function annotated with `#[target_feature]` is not a safe
3237 /// trait method implementation, reporting an error if it is.
3238 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3239     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3240     let node = tcx.hir().get(hir_id);
3241     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3242         let parent_id = tcx.hir().get_parent_did(hir_id);
3243         let parent_item = tcx.hir().expect_item(parent_id);
3244         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3245             tcx.sess
3246                 .struct_span_err(
3247                     attr_span,
3248                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3249                 )
3250                 .span_label(attr_span, "cannot be applied to safe trait method")
3251                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3252                 .emit();
3253         }
3254     }
3255 }