compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind};
  31 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::map::Map;
  36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  37 use rustc_middle::mir::mono::Linkage;
  38 use rustc_middle::ty::query::Providers;
  39 use rustc_middle::ty::subst::InternalSubsts;
  40 use rustc_middle::ty::util::Discr;
  41 use rustc_middle::ty::util::IntTypeExt;
  42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  43 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50 use std::iter;
  51
  52 mod item_bounds;
  53 mod type_of;
  54
  55 struct OnlySelfBounds(bool);
  56
  57 ///////////////////////////////////////////////////////////////////////////
  58 // Main entry point
  59
  60 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  61     tcx.hir().visit_item_likes_in_module(
  62         module_def_id,
  63         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  64     );
  65 }
  66
  67 pub fn provide(providers: &mut Providers) {
  68     *providers = Providers {
  69         opt_const_param_of: type_of::opt_const_param_of,
  70         default_anon_const_substs: type_of::default_anon_const_substs,
  71         type_of: type_of::type_of,
  72         item_bounds: item_bounds::item_bounds,
  73         explicit_item_bounds: item_bounds::explicit_item_bounds,
  74         generics_of,
  75         predicates_of,
  76         predicates_defined_on,
  77         explicit_predicates_of,
  78         super_predicates_of,
  79         super_predicates_that_define_assoc_type,
  80         trait_explicit_predicates_and_bounds,
  81         type_param_predicates,
  82         trait_def,
  83         adt_def,
  84         fn_sig,
  85         impl_trait_ref,
  86         impl_polarity,
  87         is_foreign_item,
  88         static_mutability,
  89         generator_kind,
  90         codegen_fn_attrs,
  91         collect_mod_item_types,
  92         should_inherit_track_caller,
  93         ..*providers
  94     };
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98
  99 /// Context specific to some particular item. This is what implements
 100 /// `AstConv`. It has information about the predicates that are defined
 101 /// on the trait. Unfortunately, this predicate information is
 102 /// available in various different forms at various points in the
 103 /// process. So we can't just store a pointer to e.g., the AST or the
 104 /// parsed ty form, we have to be more flexible. To this end, the
 105 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 106 /// `get_type_parameter_bounds` requests, drawing the information from
 107 /// the AST (`hir::Generics`), recursively.
 108 pub struct ItemCtxt<'tcx> {
 109     tcx: TyCtxt<'tcx>,
 110     item_def_id: DefId,
 111 }
 112
 113 ///////////////////////////////////////////////////////////////////////////
 114
 115 #[derive(Default)]
 116 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 117
 118 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 119     type Map = intravisit::ErasedMap<'v>;
 120
 121     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 122         NestedVisitorMap::None
 123     }
 124     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 125         if let hir::TyKind::Infer = t.kind {
 126             self.0.push(t.span);
 127         }
 128         intravisit::walk_ty(self, t)
 129     }
 130     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 131         match generic_arg {
 132             hir::GenericArg::Infer(inf) => {
 133                 self.0.push(inf.span);
 134                 intravisit::walk_inf(self, inf);
 135             }
 136             hir::GenericArg::Type(t) => self.visit_ty(t),
 137             _ => {}
 138         }
 139     }
 140 }
 141
 142 struct CollectItemTypesVisitor<'tcx> {
 143     tcx: TyCtxt<'tcx>,
 144 }
 145
 146 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 147 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 148 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 149 crate fn placeholder_type_error<'tcx>(
 150     tcx: TyCtxt<'tcx>,
 151     span: Option<Span>,
 152     generics: &[hir::GenericParam<'_>],
 153     placeholder_types: Vec<Span>,
 154     suggest: bool,
 155     hir_ty: Option<&hir::Ty<'_>>,
 156     kind: &'static str,
 157 ) {
 158     if placeholder_types.is_empty() {
 159         return;
 160     }
 161
 162     let type_name = generics.next_type_param_name(None);
 163     let mut sugg: Vec<_> =
 164         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 165
 166     if generics.is_empty() {
 167         if let Some(span) = span {
 168             sugg.push((span, format!("<{}>", type_name)));
 169         }
 170     } else if let Some(arg) = generics
 171         .iter()
 172         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 173     {
 174         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 175         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 176         sugg.push((arg.span, (*type_name).to_string()));
 177     } else {
 178         let last = generics.iter().last().unwrap();
 179         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 180         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 181         sugg.push((span, format!(", {}", type_name)));
 182     }
 183
 184     let mut err = bad_placeholder(tcx, "type", placeholder_types, kind);
 185
 186     // Suggest, but only if it is not a function in const or static
 187     if suggest {
 188         let mut is_fn = false;
 189         let mut is_const_or_static = false;
 190
 191         if let Some(hir_ty) = hir_ty {
 192             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 193                 is_fn = true;
 194
 195                 // Check if parent is const or static
 196                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 197                 let parent_node = tcx.hir().get(parent_id);
 198
 199                 is_const_or_static = matches!(
 200                     parent_node,
 201                     Node::Item(&hir::Item {
 202                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 203                         ..
 204                     }) | Node::TraitItem(&hir::TraitItem {
 205                         kind: hir::TraitItemKind::Const(..),
 206                         ..
 207                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 208                 );
 209             }
 210         }
 211
 212         // if function is wrapped around a const or static,
 213         // then don't show the suggestion
 214         if !(is_fn && is_const_or_static) {
 215             err.multipart_suggestion(
 216                 "use type parameters instead",
 217                 sugg,
 218                 Applicability::HasPlaceholders,
 219             );
 220         }
 221     }
 222     err.emit();
 223 }
 224
 225 fn reject_placeholder_type_signatures_in_item<'tcx>(
 226     tcx: TyCtxt<'tcx>,
 227     item: &'tcx hir::Item<'tcx>,
 228 ) {
 229     let (generics, suggest) = match &item.kind {
 230         hir::ItemKind::Union(_, generics)
 231         | hir::ItemKind::Enum(_, generics)
 232         | hir::ItemKind::TraitAlias(generics, _)
 233         | hir::ItemKind::Trait(_, _, generics, ..)
 234         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 235         | hir::ItemKind::Struct(_, generics) => (generics, true),
 236         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 237         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 238         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 239         _ => return,
 240     };
 241
 242     let mut visitor = PlaceholderHirTyCollector::default();
 243     visitor.visit_item(item);
 244
 245     placeholder_type_error(
 246         tcx,
 247         Some(generics.span),
 248         generics.params,
 249         visitor.0,
 250         suggest,
 251         None,
 252         item.kind.descr(),
 253     );
 254 }
 255
 256 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 257     type Map = Map<'tcx>;
 258
 259     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 260         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 261     }
 262
 263     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 264         convert_item(self.tcx, item.item_id());
 265         reject_placeholder_type_signatures_in_item(self.tcx, item);
 266         intravisit::walk_item(self, item);
 267     }
 268
 269     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 270         for param in generics.params {
 271             match param.kind {
 272                 hir::GenericParamKind::Lifetime { .. } => {}
 273                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 274                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 275                     self.tcx.ensure().type_of(def_id);
 276                 }
 277                 hir::GenericParamKind::Type { .. } => {}
 278                 hir::GenericParamKind::Const { default, .. } => {
 279                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 280                     self.tcx.ensure().type_of(def_id);
 281                     if let Some(default) = default {
 282                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 283                         // need to store default and type of default
 284                         self.tcx.ensure().type_of(default_def_id);
 285                         self.tcx.ensure().const_param_default(def_id);
 286                     }
 287                 }
 288             }
 289         }
 290         intravisit::walk_generics(self, generics);
 291     }
 292
 293     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 294         if let hir::ExprKind::Closure(..) = expr.kind {
 295             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 296             self.tcx.ensure().generics_of(def_id);
 297             // We do not call `type_of` for closures here as that
 298             // depends on typecheck and would therefore hide
 299             // any further errors in case one typeck fails.
 300         }
 301         intravisit::walk_expr(self, expr);
 302     }
 303
 304     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 305         convert_trait_item(self.tcx, trait_item.trait_item_id());
 306         intravisit::walk_trait_item(self, trait_item);
 307     }
 308
 309     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 310         convert_impl_item(self.tcx, impl_item.impl_item_id());
 311         intravisit::walk_impl_item(self, impl_item);
 312     }
 313 }
 314
 315 ///////////////////////////////////////////////////////////////////////////
 316 // Utility types and common code for the above passes.
 317
 318 fn bad_placeholder<'tcx>(
 319     tcx: TyCtxt<'tcx>,
 320     placeholder_kind: &'static str,
 321     mut spans: Vec<Span>,
 322     kind: &'static str,
 323 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 324     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 325
 326     spans.sort();
 327     let mut err = struct_span_err!(
 328         tcx.sess,
 329         spans.clone(),
 330         E0121,
 331         "the {} placeholder `_` is not allowed within types on item signatures for {}",
 332         placeholder_kind,
 333         kind
 334     );
 335     for span in spans {
 336         err.span_label(span, "not allowed in type signatures");
 337     }
 338     err
 339 }
 340
 341 impl<'tcx> ItemCtxt<'tcx> {
 342     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 343         ItemCtxt { tcx, item_def_id }
 344     }
 345
 346     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 347         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 348     }
 349
 350     pub fn hir_id(&self) -> hir::HirId {
 351         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 352     }
 353
 354     pub fn node(&self) -> hir::Node<'tcx> {
 355         self.tcx.hir().get(self.hir_id())
 356     }
 357 }
 358
 359 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 360     fn tcx(&self) -> TyCtxt<'tcx> {
 361         self.tcx
 362     }
 363
 364     fn item_def_id(&self) -> Option<DefId> {
 365         Some(self.item_def_id)
 366     }
 367
 368     fn get_type_parameter_bounds(
 369         &self,
 370         span: Span,
 371         def_id: DefId,
 372         assoc_name: Ident,
 373     ) -> ty::GenericPredicates<'tcx> {
 374         self.tcx.at(span).type_param_predicates((
 375             self.item_def_id,
 376             def_id.expect_local(),
 377             assoc_name,
 378         ))
 379     }
 380
 381     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 382         None
 383     }
 384
 385     fn allow_ty_infer(&self) -> bool {
 386         false
 387     }
 388
 389     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 390         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 391     }
 392
 393     fn ct_infer(
 394         &self,
 395         ty: Ty<'tcx>,
 396         _: Option<&ty::GenericParamDef>,
 397         span: Span,
 398     ) -> &'tcx Const<'tcx> {
 399         bad_placeholder(self.tcx(), "const", vec![span], "generic").emit();
 400         // Typeck doesn't expect erased regions to be returned from `type_of`.
 401         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 402             ty::ReErased => self.tcx.lifetimes.re_static,
 403             _ => r,
 404         });
 405         self.tcx().const_error(ty)
 406     }
 407
 408     fn projected_ty_from_poly_trait_ref(
 409         &self,
 410         span: Span,
 411         item_def_id: DefId,
 412         item_segment: &hir::PathSegment<'_>,
 413         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 414     ) -> Ty<'tcx> {
 415         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 416             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 417                 self,
 418                 self.tcx,
 419                 span,
 420                 item_def_id,
 421                 item_segment,
 422                 trait_ref.substs,
 423             );
 424             self.tcx().mk_projection(item_def_id, item_substs)
 425         } else {
 426             // There are no late-bound regions; we can just ignore the binder.
 427             let mut err = struct_span_err!(
 428                 self.tcx().sess,
 429                 span,
 430                 E0212,
 431                 "cannot use the associated type of a trait \
 432                  with uninferred generic parameters"
 433             );
 434
 435             match self.node() {
 436                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 437                     let item =
 438                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_did(self.hir_id()));
 439                     match &item.kind {
 440                         hir::ItemKind::Enum(_, generics)
 441                         | hir::ItemKind::Struct(_, generics)
 442                         | hir::ItemKind::Union(_, generics) => {
 443                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 444                             let (lt_sp, sugg) = match generics.params {
 445                                 [] => (generics.span, format!("<{}>", lt_name)),
 446                                 [bound, ..] => {
 447                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 448                                 }
 449                             };
 450                             let suggestions = vec![
 451                                 (lt_sp, sugg),
 452                                 (
 453                                     span.with_hi(item_segment.ident.span.lo()),
 454                                     format!(
 455                                         "{}::",
 456                                         // Replace the existing lifetimes with a new named lifetime.
 457                                         self.tcx
 458                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 459                                                 self.tcx.mk_region(ty::ReEarlyBound(
 460                                                     ty::EarlyBoundRegion {
 461                                                         def_id: item_def_id,
 462                                                         index: 0,
 463                                                         name: Symbol::intern(&lt_name),
 464                                                     },
 465                                                 ))
 466                                             })
 467                                             .0,
 468                                     ),
 469                                 ),
 470                             ];
 471                             err.multipart_suggestion(
 472                                 "use a fully qualified path with explicit lifetimes",
 473                                 suggestions,
 474                                 Applicability::MaybeIncorrect,
 475                             );
 476                         }
 477                         _ => {}
 478                     }
 479                 }
 480                 hir::Node::Item(hir::Item {
 481                     kind:
 482                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 483                     ..
 484                 }) => {}
 485                 hir::Node::Item(_)
 486                 | hir::Node::ForeignItem(_)
 487                 | hir::Node::TraitItem(_)
 488                 | hir::Node::ImplItem(_) => {
 489                     err.span_suggestion_verbose(
 490                         span.with_hi(item_segment.ident.span.lo()),
 491                         "use a fully qualified path with inferred lifetimes",
 492                         format!(
 493                             "{}::",
 494                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 495                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 496                         ),
 497                         Applicability::MaybeIncorrect,
 498                     );
 499                 }
 500                 _ => {}
 501             }
 502             err.emit();
 503             self.tcx().ty_error()
 504         }
 505     }
 506
 507     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 508         // Types in item signatures are not normalized to avoid undue dependencies.
 509         ty
 510     }
 511
 512     fn set_tainted_by_errors(&self) {
 513         // There's no obvious place to track this, so just let it go.
 514     }
 515
 516     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 517         // There's no place to record types from signatures?
 518     }
 519 }
 520
 521 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 522 fn get_new_lifetime_name<'tcx>(
 523     tcx: TyCtxt<'tcx>,
 524     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 525     generics: &hir::Generics<'tcx>,
 526 ) -> String {
 527     let existing_lifetimes = tcx
 528         .collect_referenced_late_bound_regions(&poly_trait_ref)
 529         .into_iter()
 530         .filter_map(|lt| {
 531             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 532                 Some(name.as_str().to_string())
 533             } else {
 534                 None
 535             }
 536         })
 537         .chain(generics.params.iter().filter_map(|param| {
 538             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 539                 Some(param.name.ident().as_str().to_string())
 540             } else {
 541                 None
 542             }
 543         }))
 544         .collect::<FxHashSet<String>>();
 545
 546     let a_to_z_repeat_n = |n| {
 547         (b'a'..=b'z').map(move |c| {
 548             let mut s = '\''.to_string();
 549             s.extend(std::iter::repeat(char::from(c)).take(n));
 550             s
 551         })
 552     };
 553
 554     // If all single char lifetime names are present, we wrap around and double the chars.
 555     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 556 }
 557
 558 /// Returns the predicates defined on `item_def_id` of the form
 559 /// `X: Foo` where `X` is the type parameter `def_id`.
 560 fn type_param_predicates(
 561     tcx: TyCtxt<'_>,
 562     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 563 ) -> ty::GenericPredicates<'_> {
 564     use rustc_hir::*;
 565
 566     // In the AST, bounds can derive from two places. Either
 567     // written inline like `<T: Foo>` or in a where-clause like
 568     // `where T: Foo`.
 569
 570     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 571     let param_owner = tcx.hir().ty_param_owner(param_id);
 572     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 573     let generics = tcx.generics_of(param_owner_def_id);
 574     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 575     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 576
 577     // Don't look for bounds where the type parameter isn't in scope.
 578     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 579         None
 580     } else {
 581         tcx.generics_of(item_def_id).parent
 582     };
 583
 584     let mut result = parent
 585         .map(|parent| {
 586             let icx = ItemCtxt::new(tcx, parent);
 587             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 588         })
 589         .unwrap_or_default();
 590     let mut extend = None;
 591
 592     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 593     let ast_generics = match tcx.hir().get(item_hir_id) {
 594         Node::TraitItem(item) => &item.generics,
 595
 596         Node::ImplItem(item) => &item.generics,
 597
 598         Node::Item(item) => {
 599             match item.kind {
 600                 ItemKind::Fn(.., ref generics, _)
 601                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 602                 | ItemKind::TyAlias(_, ref generics)
 603                 | ItemKind::OpaqueTy(OpaqueTy {
 604                     ref generics,
 605                     origin: hir::OpaqueTyOrigin::TyAlias,
 606                     ..
 607                 })
 608                 | ItemKind::Enum(_, ref generics)
 609                 | ItemKind::Struct(_, ref generics)
 610                 | ItemKind::Union(_, ref generics) => generics,
 611                 ItemKind::Trait(_, _, ref generics, ..) => {
 612                     // Implied `Self: Trait` and supertrait bounds.
 613                     if param_id == item_hir_id {
 614                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 615                         extend =
 616                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 617                     }
 618                     generics
 619                 }
 620                 _ => return result,
 621             }
 622         }
 623
 624         Node::ForeignItem(item) => match item.kind {
 625             ForeignItemKind::Fn(_, _, ref generics) => generics,
 626             _ => return result,
 627         },
 628
 629         _ => return result,
 630     };
 631
 632     let icx = ItemCtxt::new(tcx, item_def_id);
 633     let extra_predicates = extend.into_iter().chain(
 634         icx.type_parameter_bounds_in_generics(
 635             ast_generics,
 636             param_id,
 637             ty,
 638             OnlySelfBounds(true),
 639             Some(assoc_name),
 640         )
 641         .into_iter()
 642         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 643             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 644             _ => false,
 645         }),
 646     );
 647     result.predicates =
 648         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 649     result
 650 }
 651
 652 impl<'tcx> ItemCtxt<'tcx> {
 653     /// Finds bounds from `hir::Generics`. This requires scanning through the
 654     /// AST. We do this to avoid having to convert *all* the bounds, which
 655     /// would create artificial cycles. Instead, we can only convert the
 656     /// bounds for a type parameter `X` if `X::Foo` is used.
 657     fn type_parameter_bounds_in_generics(
 658         &self,
 659         ast_generics: &'tcx hir::Generics<'tcx>,
 660         param_id: hir::HirId,
 661         ty: Ty<'tcx>,
 662         only_self_bounds: OnlySelfBounds,
 663         assoc_name: Option<Ident>,
 664     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 665         let from_ty_params = ast_generics
 666             .params
 667             .iter()
 668             .filter_map(|param| match param.kind {
 669                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 670                 _ => None,
 671             })
 672             .flat_map(|bounds| bounds.iter())
 673             .filter(|b| match assoc_name {
 674                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 675                 None => true,
 676             })
 677             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 678
 679         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 680         let from_where_clauses = ast_generics
 681             .where_clause
 682             .predicates
 683             .iter()
 684             .filter_map(|wp| match *wp {
 685                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 686                 _ => None,
 687             })
 688             .flat_map(|bp| {
 689                 let bt = if bp.is_param_bound(param_def_id) {
 690                     Some(ty)
 691                 } else if !only_self_bounds.0 {
 692                     Some(self.to_ty(bp.bounded_ty))
 693                 } else {
 694                     None
 695                 };
 696                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 697
 698                 bp.bounds
 699                     .iter()
 700                     .filter(|b| match assoc_name {
 701                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 702                         None => true,
 703                     })
 704                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 705             })
 706             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 707
 708         from_ty_params.chain(from_where_clauses).collect()
 709     }
 710
 711     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 712         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 713
 714         match b {
 715             hir::GenericBound::Trait(poly_trait_ref, _) => {
 716                 let trait_ref = &poly_trait_ref.trait_ref;
 717                 if let Some(trait_did) = trait_ref.trait_def_id() {
 718                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 719                 } else {
 720                     false
 721                 }
 722             }
 723             _ => false,
 724         }
 725     }
 726 }
 727
 728 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 729     let it = tcx.hir().item(item_id);
 730     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 731     let def_id = item_id.def_id;
 732
 733     match it.kind {
 734         // These don't define types.
 735         hir::ItemKind::ExternCrate(_)
 736         | hir::ItemKind::Use(..)
 737         | hir::ItemKind::Macro(_)
 738         | hir::ItemKind::Mod(_)
 739         | hir::ItemKind::GlobalAsm(_) => {}
 740         hir::ItemKind::ForeignMod { items, .. } => {
 741             for item in items {
 742                 let item = tcx.hir().foreign_item(item.id);
 743                 tcx.ensure().generics_of(item.def_id);
 744                 tcx.ensure().type_of(item.def_id);
 745                 tcx.ensure().predicates_of(item.def_id);
 746                 match item.kind {
 747                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 748                     hir::ForeignItemKind::Static(..) => {
 749                         let mut visitor = PlaceholderHirTyCollector::default();
 750                         visitor.visit_foreign_item(item);
 751                         placeholder_type_error(
 752                             tcx,
 753                             None,
 754                             &[],
 755                             visitor.0,
 756                             false,
 757                             None,
 758                             "static variable",
 759                         );
 760                     }
 761                     _ => (),
 762                 }
 763             }
 764         }
 765         hir::ItemKind::Enum(ref enum_definition, _) => {
 766             tcx.ensure().generics_of(def_id);
 767             tcx.ensure().type_of(def_id);
 768             tcx.ensure().predicates_of(def_id);
 769             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 770         }
 771         hir::ItemKind::Impl { .. } => {
 772             tcx.ensure().generics_of(def_id);
 773             tcx.ensure().type_of(def_id);
 774             tcx.ensure().impl_trait_ref(def_id);
 775             tcx.ensure().predicates_of(def_id);
 776         }
 777         hir::ItemKind::Trait(..) => {
 778             tcx.ensure().generics_of(def_id);
 779             tcx.ensure().trait_def(def_id);
 780             tcx.at(it.span).super_predicates_of(def_id);
 781             tcx.ensure().predicates_of(def_id);
 782         }
 783         hir::ItemKind::TraitAlias(..) => {
 784             tcx.ensure().generics_of(def_id);
 785             tcx.at(it.span).super_predicates_of(def_id);
 786             tcx.ensure().predicates_of(def_id);
 787         }
 788         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 789             tcx.ensure().generics_of(def_id);
 790             tcx.ensure().type_of(def_id);
 791             tcx.ensure().predicates_of(def_id);
 792
 793             for f in struct_def.fields() {
 794                 let def_id = tcx.hir().local_def_id(f.hir_id);
 795                 tcx.ensure().generics_of(def_id);
 796                 tcx.ensure().type_of(def_id);
 797                 tcx.ensure().predicates_of(def_id);
 798             }
 799
 800             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 801                 convert_variant_ctor(tcx, ctor_hir_id);
 802             }
 803         }
 804
 805         // Desugared from `impl Trait`, so visited by the function's return type.
 806         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 807             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 808             ..
 809         }) => {}
 810
 811         // Don't call `type_of` on opaque types, since that depends on type
 812         // checking function bodies. `check_item_type` ensures that it's called
 813         // instead.
 814         hir::ItemKind::OpaqueTy(..) => {
 815             tcx.ensure().generics_of(def_id);
 816             tcx.ensure().predicates_of(def_id);
 817             tcx.ensure().explicit_item_bounds(def_id);
 818         }
 819         hir::ItemKind::TyAlias(..)
 820         | hir::ItemKind::Static(..)
 821         | hir::ItemKind::Const(..)
 822         | hir::ItemKind::Fn(..) => {
 823             tcx.ensure().generics_of(def_id);
 824             tcx.ensure().type_of(def_id);
 825             tcx.ensure().predicates_of(def_id);
 826             match it.kind {
 827                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 828                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 829                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 830                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 831                     if let hir::TyKind::TraitObject(..) = ty.kind {
 832                         let mut visitor = PlaceholderHirTyCollector::default();
 833                         visitor.visit_item(it);
 834                         placeholder_type_error(
 835                             tcx,
 836                             None,
 837                             &[],
 838                             visitor.0,
 839                             false,
 840                             None,
 841                             it.kind.descr(),
 842                         );
 843                     }
 844                 }
 845                 _ => (),
 846             }
 847         }
 848     }
 849 }
 850
 851 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 852     let trait_item = tcx.hir().trait_item(trait_item_id);
 853     tcx.ensure().generics_of(trait_item_id.def_id);
 854
 855     match trait_item.kind {
 856         hir::TraitItemKind::Fn(..) => {
 857             tcx.ensure().type_of(trait_item_id.def_id);
 858             tcx.ensure().fn_sig(trait_item_id.def_id);
 859         }
 860
 861         hir::TraitItemKind::Const(.., Some(_)) => {
 862             tcx.ensure().type_of(trait_item_id.def_id);
 863         }
 864
 865         hir::TraitItemKind::Const(..) => {
 866             tcx.ensure().type_of(trait_item_id.def_id);
 867             // Account for `const C: _;`.
 868             let mut visitor = PlaceholderHirTyCollector::default();
 869             visitor.visit_trait_item(trait_item);
 870             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 871         }
 872
 873         hir::TraitItemKind::Type(_, Some(_)) => {
 874             tcx.ensure().item_bounds(trait_item_id.def_id);
 875             tcx.ensure().type_of(trait_item_id.def_id);
 876             // Account for `type T = _;`.
 877             let mut visitor = PlaceholderHirTyCollector::default();
 878             visitor.visit_trait_item(trait_item);
 879             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 880         }
 881
 882         hir::TraitItemKind::Type(_, None) => {
 883             tcx.ensure().item_bounds(trait_item_id.def_id);
 884             // #74612: Visit and try to find bad placeholders
 885             // even if there is no concrete type.
 886             let mut visitor = PlaceholderHirTyCollector::default();
 887             visitor.visit_trait_item(trait_item);
 888
 889             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 890         }
 891     };
 892
 893     tcx.ensure().predicates_of(trait_item_id.def_id);
 894 }
 895
 896 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 897     let def_id = impl_item_id.def_id;
 898     tcx.ensure().generics_of(def_id);
 899     tcx.ensure().type_of(def_id);
 900     tcx.ensure().predicates_of(def_id);
 901     let impl_item = tcx.hir().impl_item(impl_item_id);
 902     match impl_item.kind {
 903         hir::ImplItemKind::Fn(..) => {
 904             tcx.ensure().fn_sig(def_id);
 905         }
 906         hir::ImplItemKind::TyAlias(_) => {
 907             // Account for `type T = _;`
 908             let mut visitor = PlaceholderHirTyCollector::default();
 909             visitor.visit_impl_item(impl_item);
 910
 911             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 912         }
 913         hir::ImplItemKind::Const(..) => {}
 914     }
 915 }
 916
 917 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 918     let def_id = tcx.hir().local_def_id(ctor_id);
 919     tcx.ensure().generics_of(def_id);
 920     tcx.ensure().type_of(def_id);
 921     tcx.ensure().predicates_of(def_id);
 922 }
 923
 924 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 925     let def = tcx.adt_def(def_id);
 926     let repr_type = def.repr.discr_type();
 927     let initial = repr_type.initial_discriminant(tcx);
 928     let mut prev_discr = None::<Discr<'_>>;
 929
 930     // fill the discriminant values and field types
 931     for variant in variants {
 932         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 933         prev_discr = Some(
 934             if let Some(ref e) = variant.disr_expr {
 935                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 936                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 937             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 938                 Some(discr)
 939             } else {
 940                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 941                     .span_label(
 942                         variant.span,
 943                         format!("overflowed on value after {}", prev_discr.unwrap()),
 944                     )
 945                     .note(&format!(
 946                         "explicitly set `{} = {}` if that is desired outcome",
 947                         variant.ident, wrapped_discr
 948                     ))
 949                     .emit();
 950                 None
 951             }
 952             .unwrap_or(wrapped_discr),
 953         );
 954
 955         for f in variant.data.fields() {
 956             let def_id = tcx.hir().local_def_id(f.hir_id);
 957             tcx.ensure().generics_of(def_id);
 958             tcx.ensure().type_of(def_id);
 959             tcx.ensure().predicates_of(def_id);
 960         }
 961
 962         // Convert the ctor, if any. This also registers the variant as
 963         // an item.
 964         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 965             convert_variant_ctor(tcx, ctor_hir_id);
 966         }
 967     }
 968 }
 969
 970 fn convert_variant(
 971     tcx: TyCtxt<'_>,
 972     variant_did: Option<LocalDefId>,
 973     ctor_did: Option<LocalDefId>,
 974     ident: Ident,
 975     discr: ty::VariantDiscr,
 976     def: &hir::VariantData<'_>,
 977     adt_kind: ty::AdtKind,
 978     parent_did: LocalDefId,
 979 ) -> ty::VariantDef {
 980     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 981     let fields = def
 982         .fields()
 983         .iter()
 984         .map(|f| {
 985             let fid = tcx.hir().local_def_id(f.hir_id);
 986             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 987             if let Some(prev_span) = dup_span {
 988                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 989                     field_name: f.ident,
 990                     span: f.span,
 991                     prev_span,
 992                 });
 993             } else {
 994                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 995             }
 996
 997             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 998         })
 999         .collect();
1000     let recovered = match def {
1001         hir::VariantData::Struct(_, r) => *r,
1002         _ => false,
1003     };
1004     ty::VariantDef::new(
1005         ident,
1006         variant_did.map(LocalDefId::to_def_id),
1007         ctor_did.map(LocalDefId::to_def_id),
1008         discr,
1009         fields,
1010         CtorKind::from_hir(def),
1011         adt_kind,
1012         parent_did.to_def_id(),
1013         recovered,
1014         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1015             || variant_did.map_or(false, |variant_did| {
1016                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1017             }),
1018     )
1019 }
1020
1021 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1022     use rustc_hir::*;
1023
1024     let def_id = def_id.expect_local();
1025     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1026     let item = match tcx.hir().get(hir_id) {
1027         Node::Item(item) => item,
1028         _ => bug!(),
1029     };
1030
1031     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1032     let (kind, variants) = match item.kind {
1033         ItemKind::Enum(ref def, _) => {
1034             let mut distance_from_explicit = 0;
1035             let variants = def
1036                 .variants
1037                 .iter()
1038                 .map(|v| {
1039                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1040                     let ctor_did =
1041                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1042
1043                     let discr = if let Some(ref e) = v.disr_expr {
1044                         distance_from_explicit = 0;
1045                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1046                     } else {
1047                         ty::VariantDiscr::Relative(distance_from_explicit)
1048                     };
1049                     distance_from_explicit += 1;
1050
1051                     convert_variant(
1052                         tcx,
1053                         variant_did,
1054                         ctor_did,
1055                         v.ident,
1056                         discr,
1057                         &v.data,
1058                         AdtKind::Enum,
1059                         def_id,
1060                     )
1061                 })
1062                 .collect();
1063
1064             (AdtKind::Enum, variants)
1065         }
1066         ItemKind::Struct(ref def, _) => {
1067             let variant_did = None::<LocalDefId>;
1068             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1069
1070             let variants = std::iter::once(convert_variant(
1071                 tcx,
1072                 variant_did,
1073                 ctor_did,
1074                 item.ident,
1075                 ty::VariantDiscr::Relative(0),
1076                 def,
1077                 AdtKind::Struct,
1078                 def_id,
1079             ))
1080             .collect();
1081
1082             (AdtKind::Struct, variants)
1083         }
1084         ItemKind::Union(ref def, _) => {
1085             let variant_did = None;
1086             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1087
1088             let variants = std::iter::once(convert_variant(
1089                 tcx,
1090                 variant_did,
1091                 ctor_did,
1092                 item.ident,
1093                 ty::VariantDiscr::Relative(0),
1094                 def,
1095                 AdtKind::Union,
1096                 def_id,
1097             ))
1098             .collect();
1099
1100             (AdtKind::Union, variants)
1101         }
1102         _ => bug!(),
1103     };
1104     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1105 }
1106
1107 /// Ensures that the super-predicates of the trait with a `DefId`
1108 /// of `trait_def_id` are converted and stored. This also ensures that
1109 /// the transitive super-predicates are converted.
1110 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1111     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1112     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1113 }
1114
1115 /// Ensures that the super-predicates of the trait with a `DefId`
1116 /// of `trait_def_id` are converted and stored. This also ensures that
1117 /// the transitive super-predicates are converted.
1118 fn super_predicates_that_define_assoc_type(
1119     tcx: TyCtxt<'_>,
1120     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1121 ) -> ty::GenericPredicates<'_> {
1122     debug!(
1123         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1124         trait_def_id, assoc_name
1125     );
1126     if trait_def_id.is_local() {
1127         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1128         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1129
1130         let item = match tcx.hir().get(trait_hir_id) {
1131             Node::Item(item) => item,
1132             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1133         };
1134
1135         let (generics, bounds) = match item.kind {
1136             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1137             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1138             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1139         };
1140
1141         let icx = ItemCtxt::new(tcx, trait_def_id);
1142
1143         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1144         let self_param_ty = tcx.types.self_param;
1145         let superbounds1 = if let Some(assoc_name) = assoc_name {
1146             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1147                 &icx,
1148                 self_param_ty,
1149                 bounds,
1150                 assoc_name,
1151             )
1152         } else {
1153             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1154         };
1155
1156         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1157
1158         // Convert any explicit superbounds in the where-clause,
1159         // e.g., `trait Foo where Self: Bar`.
1160         // In the case of trait aliases, however, we include all bounds in the where-clause,
1161         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1162         // as one of its "superpredicates".
1163         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1164         let superbounds2 = icx.type_parameter_bounds_in_generics(
1165             generics,
1166             item.hir_id(),
1167             self_param_ty,
1168             OnlySelfBounds(!is_trait_alias),
1169             assoc_name,
1170         );
1171
1172         // Combine the two lists to form the complete set of superbounds:
1173         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1174
1175         // Now require that immediate supertraits are converted,
1176         // which will, in turn, reach indirect supertraits.
1177         if assoc_name.is_none() {
1178             // Now require that immediate supertraits are converted,
1179             // which will, in turn, reach indirect supertraits.
1180             for &(pred, span) in superbounds {
1181                 debug!("superbound: {:?}", pred);
1182                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1183                     tcx.at(span).super_predicates_of(bound.def_id());
1184                 }
1185             }
1186         }
1187
1188         ty::GenericPredicates { parent: None, predicates: superbounds }
1189     } else {
1190         // if `assoc_name` is None, then the query should've been redirected to an
1191         // external provider
1192         assert!(assoc_name.is_some());
1193         tcx.super_predicates_of(trait_def_id)
1194     }
1195 }
1196
1197 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1198     let item = tcx.hir().expect_item(def_id.expect_local());
1199
1200     let (is_auto, unsafety) = match item.kind {
1201         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1202         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1203         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1204     };
1205
1206     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1207     if paren_sugar && !tcx.features().unboxed_closures {
1208         tcx.sess
1209             .struct_span_err(
1210                 item.span,
1211                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1212                  which traits can use parenthetical notation",
1213             )
1214             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1215             .emit();
1216     }
1217
1218     let is_marker = tcx.has_attr(def_id, sym::marker);
1219     let skip_array_during_method_dispatch =
1220         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1221     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1222         ty::trait_def::TraitSpecializationKind::Marker
1223     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1224         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1225     } else {
1226         ty::trait_def::TraitSpecializationKind::None
1227     };
1228     let def_path_hash = tcx.def_path_hash(def_id);
1229     ty::TraitDef::new(
1230         def_id,
1231         unsafety,
1232         paren_sugar,
1233         is_auto,
1234         is_marker,
1235         skip_array_during_method_dispatch,
1236         spec_kind,
1237         def_path_hash,
1238     )
1239 }
1240
1241 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1242     struct LateBoundRegionsDetector<'tcx> {
1243         tcx: TyCtxt<'tcx>,
1244         outer_index: ty::DebruijnIndex,
1245         has_late_bound_regions: Option<Span>,
1246     }
1247
1248     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1249         type Map = intravisit::ErasedMap<'tcx>;
1250
1251         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1252             NestedVisitorMap::None
1253         }
1254
1255         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1256             if self.has_late_bound_regions.is_some() {
1257                 return;
1258             }
1259             match ty.kind {
1260                 hir::TyKind::BareFn(..) => {
1261                     self.outer_index.shift_in(1);
1262                     intravisit::walk_ty(self, ty);
1263                     self.outer_index.shift_out(1);
1264                 }
1265                 _ => intravisit::walk_ty(self, ty),
1266             }
1267         }
1268
1269         fn visit_poly_trait_ref(
1270             &mut self,
1271             tr: &'tcx hir::PolyTraitRef<'tcx>,
1272             m: hir::TraitBoundModifier,
1273         ) {
1274             if self.has_late_bound_regions.is_some() {
1275                 return;
1276             }
1277             self.outer_index.shift_in(1);
1278             intravisit::walk_poly_trait_ref(self, tr, m);
1279             self.outer_index.shift_out(1);
1280         }
1281
1282         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1283             if self.has_late_bound_regions.is_some() {
1284                 return;
1285             }
1286
1287             match self.tcx.named_region(lt.hir_id) {
1288                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1289                 Some(
1290                     rl::Region::LateBound(debruijn, _, _, _)
1291                     | rl::Region::LateBoundAnon(debruijn, _, _),
1292                 ) if debruijn < self.outer_index => {}
1293                 Some(
1294                     rl::Region::LateBound(..)
1295                     | rl::Region::LateBoundAnon(..)
1296                     | rl::Region::Free(..),
1297                 )
1298                 | None => {
1299                     self.has_late_bound_regions = Some(lt.span);
1300                 }
1301             }
1302         }
1303     }
1304
1305     fn has_late_bound_regions<'tcx>(
1306         tcx: TyCtxt<'tcx>,
1307         generics: &'tcx hir::Generics<'tcx>,
1308         decl: &'tcx hir::FnDecl<'tcx>,
1309     ) -> Option<Span> {
1310         let mut visitor = LateBoundRegionsDetector {
1311             tcx,
1312             outer_index: ty::INNERMOST,
1313             has_late_bound_regions: None,
1314         };
1315         for param in generics.params {
1316             if let GenericParamKind::Lifetime { .. } = param.kind {
1317                 if tcx.is_late_bound(param.hir_id) {
1318                     return Some(param.span);
1319                 }
1320             }
1321         }
1322         visitor.visit_fn_decl(decl);
1323         visitor.has_late_bound_regions
1324     }
1325
1326     match node {
1327         Node::TraitItem(item) => match item.kind {
1328             hir::TraitItemKind::Fn(ref sig, _) => {
1329                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1330             }
1331             _ => None,
1332         },
1333         Node::ImplItem(item) => match item.kind {
1334             hir::ImplItemKind::Fn(ref sig, _) => {
1335                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1336             }
1337             _ => None,
1338         },
1339         Node::ForeignItem(item) => match item.kind {
1340             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1341                 has_late_bound_regions(tcx, generics, fn_decl)
1342             }
1343             _ => None,
1344         },
1345         Node::Item(item) => match item.kind {
1346             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1347                 has_late_bound_regions(tcx, generics, sig.decl)
1348             }
1349             _ => None,
1350         },
1351         _ => None,
1352     }
1353 }
1354
1355 struct AnonConstInParamTyDetector {
1356     in_param_ty: bool,
1357     found_anon_const_in_param_ty: bool,
1358     ct: HirId,
1359 }
1360
1361 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1362     type Map = intravisit::ErasedMap<'v>;
1363
1364     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1365         NestedVisitorMap::None
1366     }
1367
1368     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1369         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1370             let prev = self.in_param_ty;
1371             self.in_param_ty = true;
1372             self.visit_ty(ty);
1373             self.in_param_ty = prev;
1374         }
1375     }
1376
1377     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1378         if self.in_param_ty && self.ct == c.hir_id {
1379             self.found_anon_const_in_param_ty = true;
1380         } else {
1381             intravisit::walk_anon_const(self, c)
1382         }
1383     }
1384 }
1385
1386 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1387     use rustc_hir::*;
1388
1389     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1390
1391     let node = tcx.hir().get(hir_id);
1392     let parent_def_id = match node {
1393         Node::ImplItem(_)
1394         | Node::TraitItem(_)
1395         | Node::Variant(_)
1396         | Node::Ctor(..)
1397         | Node::Field(_) => {
1398             let parent_id = tcx.hir().get_parent_item(hir_id);
1399             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1400         }
1401         // FIXME(#43408) always enable this once `lazy_normalization` is
1402         // stable enough and does not need a feature gate anymore.
1403         Node::AnonConst(_) => {
1404             let parent_id = tcx.hir().get_parent_item(hir_id);
1405             let parent_def_id = tcx.hir().local_def_id(parent_id);
1406
1407             let mut in_param_ty = false;
1408             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1409                 if let Some(generics) = node.generics() {
1410                     let mut visitor = AnonConstInParamTyDetector {
1411                         in_param_ty: false,
1412                         found_anon_const_in_param_ty: false,
1413                         ct: hir_id,
1414                     };
1415
1416                     visitor.visit_generics(generics);
1417                     in_param_ty = visitor.found_anon_const_in_param_ty;
1418                     break;
1419                 }
1420             }
1421
1422             if in_param_ty {
1423                 // We do not allow generic parameters in anon consts if we are inside
1424                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1425                 None
1426             } else if tcx.lazy_normalization() {
1427                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1428                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1429                     //
1430                     // struct Foo<const N: usize = { .. }>;
1431                     //        ^^^       ^          ^^^^^^ def id of this anon const
1432                     //        ^         ^ param_id
1433                     //        ^ parent_def_id
1434                     //
1435                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1436                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1437                     //
1438                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1439                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1440                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1441                     //
1442                     // We fix this by having this function return the parent's generics ourselves and truncating the
1443                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1444                     //
1445                     // For the above code example that means we want `substs: []`
1446                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1447                     // the def id of the `{ N + 1 }` anon const
1448                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1449                     //
1450                     // This has some implications for how we get the predicates available to the anon const
1451                     // see `explicit_predicates_of` for more information on this
1452                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1453                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1454                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1455                     // In the above example this would be .params[..N#0]
1456                     let params = generics.params[..param_def_idx as usize].to_owned();
1457                     let param_def_id_to_index =
1458                         params.iter().map(|param| (param.def_id, param.index)).collect();
1459
1460                     return ty::Generics {
1461                         // we set the parent of these generics to be our parent's parent so that we
1462                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1463                         // struct Foo<const N: usize, const M: usize = { ... }>;
1464                         parent: generics.parent,
1465                         parent_count: generics.parent_count,
1466                         params,
1467                         param_def_id_to_index,
1468                         has_self: generics.has_self,
1469                         has_late_bound_regions: generics.has_late_bound_regions,
1470                     };
1471                 }
1472
1473                 // HACK(eddyb) this provides the correct generics when
1474                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1475                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1476                 //
1477                 // Note that we do not supply the parent generics when using
1478                 // `min_const_generics`.
1479                 Some(parent_def_id.to_def_id())
1480             } else {
1481                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1482                 match parent_node {
1483                     // HACK(eddyb) this provides the correct generics for repeat
1484                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1485                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1486                     // as they shouldn't be able to cause query cycle errors.
1487                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1488                         if constant.hir_id() == hir_id =>
1489                     {
1490                         Some(parent_def_id.to_def_id())
1491                     }
1492                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1493                         if constant.hir_id == hir_id =>
1494                     {
1495                         Some(parent_def_id.to_def_id())
1496                     }
1497                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1498                         Some(tcx.typeck_root_def_id(def_id))
1499                     }
1500                     _ => None,
1501                 }
1502             }
1503         }
1504         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1505             Some(tcx.typeck_root_def_id(def_id))
1506         }
1507         Node::Item(item) => match item.kind {
1508             ItemKind::OpaqueTy(hir::OpaqueTy {
1509                 origin:
1510                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1511                 ..
1512             }) => Some(fn_def_id.to_def_id()),
1513             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1514                 let parent_id = tcx.hir().get_parent_item(hir_id);
1515                 assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1516                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1517                 // Opaque types are always nested within another item, and
1518                 // inherit the generics of the item.
1519                 Some(tcx.hir().local_def_id(parent_id).to_def_id())
1520             }
1521             _ => None,
1522         },
1523         _ => None,
1524     };
1525
1526     let mut opt_self = None;
1527     let mut allow_defaults = false;
1528
1529     let no_generics = hir::Generics::empty();
1530     let ast_generics = match node {
1531         Node::TraitItem(item) => &item.generics,
1532
1533         Node::ImplItem(item) => &item.generics,
1534
1535         Node::Item(item) => {
1536             match item.kind {
1537                 ItemKind::Fn(.., ref generics, _)
1538                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1539
1540                 ItemKind::TyAlias(_, ref generics)
1541                 | ItemKind::Enum(_, ref generics)
1542                 | ItemKind::Struct(_, ref generics)
1543                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1544                 | ItemKind::Union(_, ref generics) => {
1545                     allow_defaults = true;
1546                     generics
1547                 }
1548
1549                 ItemKind::Trait(_, _, ref generics, ..)
1550                 | ItemKind::TraitAlias(ref generics, ..) => {
1551                     // Add in the self type parameter.
1552                     //
1553                     // Something of a hack: use the node id for the trait, also as
1554                     // the node id for the Self type parameter.
1555                     let param_id = item.def_id;
1556
1557                     opt_self = Some(ty::GenericParamDef {
1558                         index: 0,
1559                         name: kw::SelfUpper,
1560                         def_id: param_id.to_def_id(),
1561                         pure_wrt_drop: false,
1562                         kind: ty::GenericParamDefKind::Type {
1563                             has_default: false,
1564                             object_lifetime_default: rl::Set1::Empty,
1565                             synthetic: false,
1566                         },
1567                     });
1568
1569                     allow_defaults = true;
1570                     generics
1571                 }
1572
1573                 _ => &no_generics,
1574             }
1575         }
1576
1577         Node::ForeignItem(item) => match item.kind {
1578             ForeignItemKind::Static(..) => &no_generics,
1579             ForeignItemKind::Fn(_, _, ref generics) => generics,
1580             ForeignItemKind::Type => &no_generics,
1581         },
1582
1583         _ => &no_generics,
1584     };
1585
1586     let has_self = opt_self.is_some();
1587     let mut parent_has_self = false;
1588     let mut own_start = has_self as u32;
1589     let parent_count = parent_def_id.map_or(0, |def_id| {
1590         let generics = tcx.generics_of(def_id);
1591         assert!(!has_self);
1592         parent_has_self = generics.has_self;
1593         own_start = generics.count() as u32;
1594         generics.parent_count + generics.params.len()
1595     });
1596
1597     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1598
1599     if let Some(opt_self) = opt_self {
1600         params.push(opt_self);
1601     }
1602
1603     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1604     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1605         name: param.name.ident().name,
1606         index: own_start + i as u32,
1607         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1608         pure_wrt_drop: param.pure_wrt_drop,
1609         kind: ty::GenericParamDefKind::Lifetime,
1610     }));
1611
1612     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1613
1614     // Now create the real type and const parameters.
1615     let type_start = own_start - has_self as u32 + params.len() as u32;
1616     let mut i = 0;
1617
1618     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1619         GenericParamKind::Lifetime { .. } => None,
1620         GenericParamKind::Type { ref default, synthetic, .. } => {
1621             if !allow_defaults && default.is_some() {
1622                 if !tcx.features().default_type_parameter_fallback {
1623                     tcx.struct_span_lint_hir(
1624                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1625                         param.hir_id,
1626                         param.span,
1627                         |lint| {
1628                             lint.build(
1629                                 "defaults for type parameters are only allowed in \
1630                                  `struct`, `enum`, `type`, or `trait` definitions",
1631                             )
1632                             .emit();
1633                         },
1634                     );
1635                 }
1636             }
1637
1638             let kind = ty::GenericParamDefKind::Type {
1639                 has_default: default.is_some(),
1640                 object_lifetime_default: object_lifetime_defaults
1641                     .as_ref()
1642                     .map_or(rl::Set1::Empty, |o| o[i]),
1643                 synthetic,
1644             };
1645
1646             let param_def = ty::GenericParamDef {
1647                 index: type_start + i as u32,
1648                 name: param.name.ident().name,
1649                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1650                 pure_wrt_drop: param.pure_wrt_drop,
1651                 kind,
1652             };
1653             i += 1;
1654             Some(param_def)
1655         }
1656         GenericParamKind::Const { default, .. } => {
1657             if !allow_defaults && default.is_some() {
1658                 tcx.sess.span_err(
1659                     param.span,
1660                     "defaults for const parameters are only allowed in \
1661                     `struct`, `enum`, `type`, or `trait` definitions",
1662                 );
1663             }
1664
1665             let param_def = ty::GenericParamDef {
1666                 index: type_start + i as u32,
1667                 name: param.name.ident().name,
1668                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1669                 pure_wrt_drop: param.pure_wrt_drop,
1670                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1671             };
1672             i += 1;
1673             Some(param_def)
1674         }
1675     }));
1676
1677     // provide junk type parameter defs - the only place that
1678     // cares about anything but the length is instantiation,
1679     // and we don't do that for closures.
1680     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1681         let dummy_args = if gen.is_some() {
1682             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1683         } else {
1684             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1685         };
1686
1687         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1688             index: type_start + i as u32,
1689             name: Symbol::intern(arg),
1690             def_id,
1691             pure_wrt_drop: false,
1692             kind: ty::GenericParamDefKind::Type {
1693                 has_default: false,
1694                 object_lifetime_default: rl::Set1::Empty,
1695                 synthetic: false,
1696             },
1697         }));
1698     }
1699
1700     // provide junk type parameter defs for const blocks.
1701     if let Node::AnonConst(_) = node {
1702         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1703         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1704             params.push(ty::GenericParamDef {
1705                 index: type_start,
1706                 name: Symbol::intern("<const_ty>"),
1707                 def_id,
1708                 pure_wrt_drop: false,
1709                 kind: ty::GenericParamDefKind::Type {
1710                     has_default: false,
1711                     object_lifetime_default: rl::Set1::Empty,
1712                     synthetic: false,
1713                 },
1714             });
1715         }
1716     }
1717
1718     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1719
1720     ty::Generics {
1721         parent: parent_def_id,
1722         parent_count,
1723         params,
1724         param_def_id_to_index,
1725         has_self: has_self || parent_has_self,
1726         has_late_bound_regions: has_late_bound_regions(tcx, node),
1727     }
1728 }
1729
1730 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1731     generic_args.iter().any(|arg| match arg {
1732         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1733         hir::GenericArg::Infer(_) => true,
1734         _ => false,
1735     })
1736 }
1737
1738 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1739 /// use inference to provide suggestions for the appropriate type if possible.
1740 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1741     use hir::TyKind::*;
1742     match &ty.kind {
1743         Infer => true,
1744         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1745         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1746         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1747         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1748         Path(hir::QPath::TypeRelative(ty, segment)) => {
1749             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1750         }
1751         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1752             ty_opt.map_or(false, is_suggestable_infer_ty)
1753                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1754         }
1755         _ => false,
1756     }
1757 }
1758
1759 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1760     if let hir::FnRetTy::Return(ty) = output {
1761         if is_suggestable_infer_ty(ty) {
1762             return Some(&*ty);
1763         }
1764     }
1765     None
1766 }
1767
1768 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1769     use rustc_hir::Node::*;
1770     use rustc_hir::*;
1771
1772     let def_id = def_id.expect_local();
1773     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1774
1775     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1776
1777     match tcx.hir().get(hir_id) {
1778         TraitItem(hir::TraitItem {
1779             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1780             ident,
1781             generics,
1782             ..
1783         })
1784         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1785         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1786             match get_infer_ret_ty(&sig.decl.output) {
1787                 Some(ty) => {
1788                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1789                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1790                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1791                         ty::ReErased => tcx.lifetimes.re_static,
1792                         _ => r,
1793                     });
1794                     let fn_sig = ty::Binder::dummy(fn_sig);
1795
1796                     let mut visitor = PlaceholderHirTyCollector::default();
1797                     visitor.visit_ty(ty);
1798                     let mut diag = bad_placeholder(tcx, "type", visitor.0, "return type");
1799                     let ret_ty = fn_sig.skip_binder().output();
1800                     if !ret_ty.references_error() {
1801                         if !ret_ty.is_closure() {
1802                             let ret_ty_str = match ret_ty.kind() {
1803                                 // Suggest a function pointer return type instead of a unique function definition
1804                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1805                                 // syntax)
1806                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1807                                 _ => ret_ty.to_string(),
1808                             };
1809                             diag.span_suggestion(
1810                                 ty.span,
1811                                 "replace with the correct return type",
1812                                 ret_ty_str,
1813                                 Applicability::MaybeIncorrect,
1814                             );
1815                         } else {
1816                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1817                             // to prevent the user from getting a papercut while trying to use the unique closure
1818                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1819                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1820                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1821                         }
1822                     }
1823                     diag.emit();
1824
1825                     fn_sig
1826                 }
1827                 None => <dyn AstConv<'_>>::ty_of_fn(
1828                     &icx,
1829                     hir_id,
1830                     sig.header.unsafety,
1831                     sig.header.abi,
1832                     sig.decl,
1833                     generics,
1834                     Some(ident.span),
1835                     None,
1836                 ),
1837             }
1838         }
1839
1840         TraitItem(hir::TraitItem {
1841             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1842             ident,
1843             generics,
1844             ..
1845         }) => <dyn AstConv<'_>>::ty_of_fn(
1846             &icx,
1847             hir_id,
1848             header.unsafety,
1849             header.abi,
1850             decl,
1851             generics,
1852             Some(ident.span),
1853             None,
1854         ),
1855
1856         ForeignItem(&hir::ForeignItem {
1857             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1858         }) => {
1859             let abi = tcx.hir().get_foreign_abi(hir_id);
1860             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1861         }
1862
1863         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1864             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1865             let inputs =
1866                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1867             ty::Binder::dummy(tcx.mk_fn_sig(
1868                 inputs,
1869                 ty,
1870                 false,
1871                 hir::Unsafety::Normal,
1872                 abi::Abi::Rust,
1873             ))
1874         }
1875
1876         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1877             // Closure signatures are not like other function
1878             // signatures and cannot be accessed through `fn_sig`. For
1879             // example, a closure signature excludes the `self`
1880             // argument. In any case they are embedded within the
1881             // closure type as part of the `ClosureSubsts`.
1882             //
1883             // To get the signature of a closure, you should use the
1884             // `sig` method on the `ClosureSubsts`:
1885             //
1886             //    substs.as_closure().sig(def_id, tcx)
1887             bug!(
1888                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1889             );
1890         }
1891
1892         x => {
1893             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1894         }
1895     }
1896 }
1897
1898 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1899     let icx = ItemCtxt::new(tcx, def_id);
1900     match tcx.hir().expect_item(def_id.expect_local()).kind {
1901         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1902             let selfty = tcx.type_of(def_id);
1903             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1904         }),
1905         _ => bug!(),
1906     }
1907 }
1908
1909 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1910     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1911     let item = tcx.hir().expect_item(def_id.expect_local());
1912     match &item.kind {
1913         hir::ItemKind::Impl(hir::Impl {
1914             polarity: hir::ImplPolarity::Negative(span),
1915             of_trait,
1916             ..
1917         }) => {
1918             if is_rustc_reservation {
1919                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1920                 tcx.sess.span_err(span, "reservation impls can't be negative");
1921             }
1922             ty::ImplPolarity::Negative
1923         }
1924         hir::ItemKind::Impl(hir::Impl {
1925             polarity: hir::ImplPolarity::Positive,
1926             of_trait: None,
1927             ..
1928         }) => {
1929             if is_rustc_reservation {
1930                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1931             }
1932             ty::ImplPolarity::Positive
1933         }
1934         hir::ItemKind::Impl(hir::Impl {
1935             polarity: hir::ImplPolarity::Positive,
1936             of_trait: Some(_),
1937             ..
1938         }) => {
1939             if is_rustc_reservation {
1940                 ty::ImplPolarity::Reservation
1941             } else {
1942                 ty::ImplPolarity::Positive
1943             }
1944         }
1945         item => bug!("impl_polarity: {:?} not an impl", item),
1946     }
1947 }
1948
1949 /// Returns the early-bound lifetimes declared in this generics
1950 /// listing. For anything other than fns/methods, this is just all
1951 /// the lifetimes that are declared. For fns or methods, we have to
1952 /// screen out those that do not appear in any where-clauses etc using
1953 /// `resolve_lifetime::early_bound_lifetimes`.
1954 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1955     tcx: TyCtxt<'tcx>,
1956     generics: &'a hir::Generics<'a>,
1957 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1958     generics.params.iter().filter(move |param| match param.kind {
1959         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1960         _ => false,
1961     })
1962 }
1963
1964 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1965 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1966 /// inferred constraints concerning which regions outlive other regions.
1967 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1968     debug!("predicates_defined_on({:?})", def_id);
1969     let mut result = tcx.explicit_predicates_of(def_id);
1970     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1971     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1972     if !inferred_outlives.is_empty() {
1973         debug!(
1974             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1975             def_id, inferred_outlives,
1976         );
1977         if result.predicates.is_empty() {
1978             result.predicates = inferred_outlives;
1979         } else {
1980             result.predicates = tcx
1981                 .arena
1982                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1983         }
1984     }
1985
1986     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1987     result
1988 }
1989
1990 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1991 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1992 /// `Self: Trait` predicates for traits.
1993 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1994     let mut result = tcx.predicates_defined_on(def_id);
1995
1996     if tcx.is_trait(def_id) {
1997         // For traits, add `Self: Trait` predicate. This is
1998         // not part of the predicates that a user writes, but it
1999         // is something that one must prove in order to invoke a
2000         // method or project an associated type.
2001         //
2002         // In the chalk setup, this predicate is not part of the
2003         // "predicates" for a trait item. But it is useful in
2004         // rustc because if you directly (e.g.) invoke a trait
2005         // method like `Trait::method(...)`, you must naturally
2006         // prove that the trait applies to the types that were
2007         // used, and adding the predicate into this list ensures
2008         // that this is done.
2009         //
2010         // We use a DUMMY_SP here as a way to signal trait bounds that come
2011         // from the trait itself that *shouldn't* be shown as the source of
2012         // an obligation and instead be skipped. Otherwise we'd use
2013         // `tcx.def_span(def_id);`
2014         let span = rustc_span::DUMMY_SP;
2015         result.predicates =
2016             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2017                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2018                 span,
2019             ))));
2020     }
2021     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2022     result
2023 }
2024
2025 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2026 /// N.B., this does not include any implied/inferred constraints.
2027 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2028     use rustc_hir::*;
2029
2030     debug!("explicit_predicates_of(def_id={:?})", def_id);
2031
2032     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2033     let node = tcx.hir().get(hir_id);
2034
2035     let mut is_trait = None;
2036     let mut is_default_impl_trait = None;
2037
2038     let icx = ItemCtxt::new(tcx, def_id);
2039
2040     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2041
2042     // We use an `IndexSet` to preserves order of insertion.
2043     // Preserving the order of insertion is important here so as not to break UI tests.
2044     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2045
2046     let ast_generics = match node {
2047         Node::TraitItem(item) => &item.generics,
2048
2049         Node::ImplItem(item) => &item.generics,
2050
2051         Node::Item(item) => {
2052             match item.kind {
2053                 ItemKind::Impl(ref impl_) => {
2054                     if impl_.defaultness.is_default() {
2055                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2056                     }
2057                     &impl_.generics
2058                 }
2059                 ItemKind::Fn(.., ref generics, _)
2060                 | ItemKind::TyAlias(_, ref generics)
2061                 | ItemKind::Enum(_, ref generics)
2062                 | ItemKind::Struct(_, ref generics)
2063                 | ItemKind::Union(_, ref generics) => generics,
2064
2065                 ItemKind::Trait(_, _, ref generics, ..) => {
2066                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2067                     generics
2068                 }
2069                 ItemKind::TraitAlias(ref generics, _) => {
2070                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2071                     generics
2072                 }
2073                 ItemKind::OpaqueTy(OpaqueTy {
2074                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2075                     ..
2076                 }) => {
2077                     // return-position impl trait
2078                     //
2079                     // We don't inherit predicates from the parent here:
2080                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2081                     // then the return type is `f::<'static, T>::{{opaque}}`.
2082                     //
2083                     // If we inherited the predicates of `f` then we would
2084                     // require that `T: 'static` to show that the return
2085                     // type is well-formed.
2086                     //
2087                     // The only way to have something with this opaque type
2088                     // is from the return type of the containing function,
2089                     // which will ensure that the function's predicates
2090                     // hold.
2091                     return ty::GenericPredicates { parent: None, predicates: &[] };
2092                 }
2093                 ItemKind::OpaqueTy(OpaqueTy {
2094                     ref generics,
2095                     origin: hir::OpaqueTyOrigin::TyAlias,
2096                     ..
2097                 }) => {
2098                     // type-alias impl trait
2099                     generics
2100                 }
2101
2102                 _ => NO_GENERICS,
2103             }
2104         }
2105
2106         Node::ForeignItem(item) => match item.kind {
2107             ForeignItemKind::Static(..) => NO_GENERICS,
2108             ForeignItemKind::Fn(_, _, ref generics) => generics,
2109             ForeignItemKind::Type => NO_GENERICS,
2110         },
2111
2112         _ => NO_GENERICS,
2113     };
2114
2115     let generics = tcx.generics_of(def_id);
2116     let parent_count = generics.parent_count as u32;
2117     let has_own_self = generics.has_self && parent_count == 0;
2118
2119     // Below we'll consider the bounds on the type parameters (including `Self`)
2120     // and the explicit where-clauses, but to get the full set of predicates
2121     // on a trait we need to add in the supertrait bounds and bounds found on
2122     // associated types.
2123     if let Some(_trait_ref) = is_trait {
2124         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2125     }
2126
2127     // In default impls, we can assume that the self type implements
2128     // the trait. So in:
2129     //
2130     //     default impl Foo for Bar { .. }
2131     //
2132     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2133     // (see below). Recall that a default impl is not itself an impl, but rather a
2134     // set of defaults that can be incorporated into another impl.
2135     if let Some(trait_ref) = is_default_impl_trait {
2136         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2137     }
2138
2139     // Collect the region predicates that were declared inline as
2140     // well. In the case of parameters declared on a fn or method, we
2141     // have to be careful to only iterate over early-bound regions.
2142     let mut index = parent_count + has_own_self as u32;
2143     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2144         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2145             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2146             index,
2147             name: param.name.ident().name,
2148         }));
2149         index += 1;
2150
2151         match param.kind {
2152             GenericParamKind::Lifetime { .. } => {
2153                 param.bounds.iter().for_each(|bound| match bound {
2154                     hir::GenericBound::Outlives(lt) => {
2155                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2156                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2157                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2158                     }
2159                     _ => bug!(),
2160                 });
2161             }
2162             _ => bug!(),
2163         }
2164     }
2165
2166     // Collect the predicates that were written inline by the user on each
2167     // type parameter (e.g., `<T: Foo>`).
2168     for param in ast_generics.params {
2169         match param.kind {
2170             // We already dealt with early bound lifetimes above.
2171             GenericParamKind::Lifetime { .. } => (),
2172             GenericParamKind::Type { .. } => {
2173                 let name = param.name.ident().name;
2174                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2175                 index += 1;
2176
2177                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2178                 // Params are implicitly sized unless a `?Sized` bound is found
2179                 <dyn AstConv<'_>>::add_implicitly_sized(
2180                     &icx,
2181                     &mut bounds,
2182                     param.bounds,
2183                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2184                     param.span,
2185                 );
2186                 predicates.extend(bounds.predicates(tcx, param_ty));
2187             }
2188             GenericParamKind::Const { .. } => {
2189                 // Bounds on const parameters are currently not possible.
2190                 debug_assert!(param.bounds.is_empty());
2191                 index += 1;
2192             }
2193         }
2194     }
2195
2196     // Add in the bounds that appear in the where-clause.
2197     let where_clause = &ast_generics.where_clause;
2198     for predicate in where_clause.predicates {
2199         match predicate {
2200             hir::WherePredicate::BoundPredicate(bound_pred) => {
2201                 let ty = icx.to_ty(bound_pred.bounded_ty);
2202                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2203
2204                 // Keep the type around in a dummy predicate, in case of no bounds.
2205                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2206                 // is still checked for WF.
2207                 if bound_pred.bounds.is_empty() {
2208                     if let ty::Param(_) = ty.kind() {
2209                         // This is a `where T:`, which can be in the HIR from the
2210                         // transformation that moves `?Sized` to `T`'s declaration.
2211                         // We can skip the predicate because type parameters are
2212                         // trivially WF, but also we *should*, to avoid exposing
2213                         // users who never wrote `where Type:,` themselves, to
2214                         // compiler/tooling bugs from not handling WF predicates.
2215                     } else {
2216                         let span = bound_pred.bounded_ty.span;
2217                         let re_root_empty = tcx.lifetimes.re_root_empty;
2218                         let predicate = ty::Binder::bind_with_vars(
2219                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2220                                 ty,
2221                                 re_root_empty,
2222                             )),
2223                             bound_vars,
2224                         );
2225                         predicates.insert((predicate.to_predicate(tcx), span));
2226                     }
2227                 }
2228
2229                 let mut bounds = Bounds::default();
2230                 <dyn AstConv<'_>>::add_bounds(
2231                     &icx,
2232                     ty,
2233                     bound_pred.bounds.iter(),
2234                     &mut bounds,
2235                     bound_vars,
2236                 );
2237                 predicates.extend(bounds.predicates(tcx, ty));
2238             }
2239
2240             hir::WherePredicate::RegionPredicate(region_pred) => {
2241                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2242                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2243                     let (r2, span) = match bound {
2244                         hir::GenericBound::Outlives(lt) => {
2245                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2246                         }
2247                         _ => bug!(),
2248                     };
2249                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2250                         ty::OutlivesPredicate(r1, r2),
2251                     ))
2252                     .to_predicate(icx.tcx);
2253
2254                     (pred, span)
2255                 }))
2256             }
2257
2258             hir::WherePredicate::EqPredicate(..) => {
2259                 // FIXME(#20041)
2260             }
2261         }
2262     }
2263
2264     if tcx.features().generic_const_exprs {
2265         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2266     }
2267
2268     let mut predicates: Vec<_> = predicates.into_iter().collect();
2269
2270     // Subtle: before we store the predicates into the tcx, we
2271     // sort them so that predicates like `T: Foo<Item=U>` come
2272     // before uses of `U`.  This avoids false ambiguity errors
2273     // in trait checking. See `setup_constraining_predicates`
2274     // for details.
2275     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2276         let self_ty = tcx.type_of(def_id);
2277         let trait_ref = tcx.impl_trait_ref(def_id);
2278         cgp::setup_constraining_predicates(
2279             tcx,
2280             &mut predicates,
2281             trait_ref,
2282             &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref),
2283         );
2284     }
2285
2286     let result = ty::GenericPredicates {
2287         parent: generics.parent,
2288         predicates: tcx.arena.alloc_from_iter(predicates),
2289     };
2290     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2291     result
2292 }
2293
2294 fn const_evaluatable_predicates_of<'tcx>(
2295     tcx: TyCtxt<'tcx>,
2296     def_id: LocalDefId,
2297 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2298     struct ConstCollector<'tcx> {
2299         tcx: TyCtxt<'tcx>,
2300         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2301     }
2302
2303     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2304         type Map = Map<'tcx>;
2305
2306         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2307             intravisit::NestedVisitorMap::None
2308         }
2309
2310         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2311             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2312             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2313             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2314                 assert_eq!(uv.promoted, None);
2315                 let span = self.tcx.hir().span(c.hir_id);
2316                 self.preds.insert((
2317                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2318                         .to_predicate(self.tcx),
2319                     span,
2320                 ));
2321             }
2322         }
2323
2324         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2325             // Do not look into const param defaults,
2326             // these get checked when they are actually instantiated.
2327             //
2328             // We do not want the following to error:
2329             //
2330             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2331             //     struct Bar<const N: usize>(Foo<N, 3>);
2332         }
2333     }
2334
2335     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2336     let node = tcx.hir().get(hir_id);
2337
2338     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2339     if let hir::Node::Item(item) = node {
2340         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2341             if let Some(of_trait) = &impl_.of_trait {
2342                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2343                 collector.visit_trait_ref(of_trait);
2344             }
2345
2346             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2347             collector.visit_ty(impl_.self_ty);
2348         }
2349     }
2350
2351     if let Some(generics) = node.generics() {
2352         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2353         collector.visit_generics(generics);
2354     }
2355
2356     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2357         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2358         collector.visit_fn_decl(fn_sig.decl);
2359     }
2360     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2361
2362     collector.preds
2363 }
2364
2365 fn trait_explicit_predicates_and_bounds(
2366     tcx: TyCtxt<'_>,
2367     def_id: LocalDefId,
2368 ) -> ty::GenericPredicates<'_> {
2369     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2370     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2371 }
2372
2373 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2374     let def_kind = tcx.def_kind(def_id);
2375     if let DefKind::Trait = def_kind {
2376         // Remove bounds on associated types from the predicates, they will be
2377         // returned by `explicit_item_bounds`.
2378         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2379         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2380
2381         let is_assoc_item_ty = |ty: Ty<'_>| {
2382             // For a predicate from a where clause to become a bound on an
2383             // associated type:
2384             // * It must use the identity substs of the item.
2385             //     * Since any generic parameters on the item are not in scope,
2386             //       this means that the item is not a GAT, and its identity
2387             //       substs are the same as the trait's.
2388             // * It must be an associated type for this trait (*not* a
2389             //   supertrait).
2390             if let ty::Projection(projection) = ty.kind() {
2391                 projection.substs == trait_identity_substs
2392                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2393             } else {
2394                 false
2395             }
2396         };
2397
2398         let predicates: Vec<_> = predicates_and_bounds
2399             .predicates
2400             .iter()
2401             .copied()
2402             .filter(|(pred, _)| match pred.kind().skip_binder() {
2403                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2404                 ty::PredicateKind::Projection(proj) => {
2405                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2406                 }
2407                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2408                 _ => true,
2409             })
2410             .collect();
2411         if predicates.len() == predicates_and_bounds.predicates.len() {
2412             predicates_and_bounds
2413         } else {
2414             ty::GenericPredicates {
2415                 parent: predicates_and_bounds.parent,
2416                 predicates: tcx.arena.alloc_slice(&predicates),
2417             }
2418         }
2419     } else {
2420         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2421             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2422             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2423                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2424                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2425                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2426                 //
2427                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2428                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2429                 //        ^^^                                             explicit_predicates_of on
2430                 //        parent item we dont have set as the
2431                 //        parent of generics returned by `generics_of`
2432                 //
2433                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2434                 let item_id = tcx.hir().get_parent_item(hir_id);
2435                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2436                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2437                 return tcx.explicit_predicates_of(item_def_id);
2438             }
2439         }
2440         gather_explicit_predicates_of(tcx, def_id)
2441     }
2442 }
2443
2444 /// Converts a specific `GenericBound` from the AST into a set of
2445 /// predicates that apply to the self type. A vector is returned
2446 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2447 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2448 /// and `<T as Bar>::X == i32`).
2449 fn predicates_from_bound<'tcx>(
2450     astconv: &dyn AstConv<'tcx>,
2451     param_ty: Ty<'tcx>,
2452     bound: &'tcx hir::GenericBound<'tcx>,
2453     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2454 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2455     let mut bounds = Bounds::default();
2456     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2457     bounds.predicates(astconv.tcx(), param_ty)
2458 }
2459
2460 fn compute_sig_of_foreign_fn_decl<'tcx>(
2461     tcx: TyCtxt<'tcx>,
2462     def_id: DefId,
2463     decl: &'tcx hir::FnDecl<'tcx>,
2464     abi: abi::Abi,
2465     ident: Ident,
2466 ) -> ty::PolyFnSig<'tcx> {
2467     let unsafety = if abi == abi::Abi::RustIntrinsic {
2468         intrinsic_operation_unsafety(tcx.item_name(def_id))
2469     } else {
2470         hir::Unsafety::Unsafe
2471     };
2472     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2473     let fty = <dyn AstConv<'_>>::ty_of_fn(
2474         &ItemCtxt::new(tcx, def_id),
2475         hir_id,
2476         unsafety,
2477         abi,
2478         decl,
2479         &hir::Generics::empty(),
2480         Some(ident.span),
2481         None,
2482     );
2483
2484     // Feature gate SIMD types in FFI, since I am not sure that the
2485     // ABIs are handled at all correctly. -huonw
2486     if abi != abi::Abi::RustIntrinsic
2487         && abi != abi::Abi::PlatformIntrinsic
2488         && !tcx.features().simd_ffi
2489     {
2490         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2491             if ty.is_simd() {
2492                 let snip = tcx
2493                     .sess
2494                     .source_map()
2495                     .span_to_snippet(ast_ty.span)
2496                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2497                 tcx.sess
2498                     .struct_span_err(
2499                         ast_ty.span,
2500                         &format!(
2501                             "use of SIMD type{} in FFI is highly experimental and \
2502                              may result in invalid code",
2503                             snip
2504                         ),
2505                     )
2506                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2507                     .emit();
2508             }
2509         };
2510         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2511             check(input, ty)
2512         }
2513         if let hir::FnRetTy::Return(ref ty) = decl.output {
2514             check(ty, fty.output().skip_binder())
2515         }
2516     }
2517
2518     fty
2519 }
2520
2521 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2522     match tcx.hir().get_if_local(def_id) {
2523         Some(Node::ForeignItem(..)) => true,
2524         Some(_) => false,
2525         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2526     }
2527 }
2528
2529 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2530     match tcx.hir().get_if_local(def_id) {
2531         Some(
2532             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2533             | Node::ForeignItem(&hir::ForeignItem {
2534                 kind: hir::ForeignItemKind::Static(_, mutbl),
2535                 ..
2536             }),
2537         ) => Some(mutbl),
2538         Some(_) => None,
2539         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2540     }
2541 }
2542
2543 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2544     match tcx.hir().get_if_local(def_id) {
2545         Some(Node::Expr(&rustc_hir::Expr {
2546             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2547             ..
2548         })) => tcx.hir().body(body_id).generator_kind(),
2549         Some(_) => None,
2550         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2551     }
2552 }
2553
2554 fn from_target_feature(
2555     tcx: TyCtxt<'_>,
2556     id: DefId,
2557     attr: &ast::Attribute,
2558     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2559     target_features: &mut Vec<Symbol>,
2560 ) {
2561     let list = match attr.meta_item_list() {
2562         Some(list) => list,
2563         None => return,
2564     };
2565     let bad_item = |span| {
2566         let msg = "malformed `target_feature` attribute input";
2567         let code = "enable = \"..\"".to_owned();
2568         tcx.sess
2569             .struct_span_err(span, msg)
2570             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2571             .emit();
2572     };
2573     let rust_features = tcx.features();
2574     for item in list {
2575         // Only `enable = ...` is accepted in the meta-item list.
2576         if !item.has_name(sym::enable) {
2577             bad_item(item.span());
2578             continue;
2579         }
2580
2581         // Must be of the form `enable = "..."` (a string).
2582         let value = match item.value_str() {
2583             Some(value) => value,
2584             None => {
2585                 bad_item(item.span());
2586                 continue;
2587             }
2588         };
2589
2590         // We allow comma separation to enable multiple features.
2591         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2592             let feature_gate = match supported_target_features.get(feature) {
2593                 Some(g) => g,
2594                 None => {
2595                     let msg =
2596                         format!("the feature named `{}` is not valid for this target", feature);
2597                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2598                     err.span_label(
2599                         item.span(),
2600                         format!("`{}` is not valid for this target", feature),
2601                     );
2602                     if let Some(stripped) = feature.strip_prefix('+') {
2603                         let valid = supported_target_features.contains_key(stripped);
2604                         if valid {
2605                             err.help("consider removing the leading `+` in the feature name");
2606                         }
2607                     }
2608                     err.emit();
2609                     return None;
2610                 }
2611             };
2612
2613             // Only allow features whose feature gates have been enabled.
2614             let allowed = match feature_gate.as_ref().copied() {
2615                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2616                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2617                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2618                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2619                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2620                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2621                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2622                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2623                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2624                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2625                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2626                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2627                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2628                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2629                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2630                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2631                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2632                 Some(name) => bug!("unknown target feature gate {}", name),
2633                 None => true,
2634             };
2635             if !allowed && id.is_local() {
2636                 feature_err(
2637                     &tcx.sess.parse_sess,
2638                     feature_gate.unwrap(),
2639                     item.span(),
2640                     &format!("the target feature `{}` is currently unstable", feature),
2641                 )
2642                 .emit();
2643             }
2644             Some(Symbol::intern(feature))
2645         }));
2646     }
2647 }
2648
2649 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2650     use rustc_middle::mir::mono::Linkage::*;
2651
2652     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2653     // applicable to variable declarations and may not really make sense for
2654     // Rust code in the first place but allow them anyway and trust that the
2655     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2656     // up in the future.
2657     //
2658     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2659     // and don't have to be, LLVM treats them as no-ops.
2660     match name {
2661         "appending" => Appending,
2662         "available_externally" => AvailableExternally,
2663         "common" => Common,
2664         "extern_weak" => ExternalWeak,
2665         "external" => External,
2666         "internal" => Internal,
2667         "linkonce" => LinkOnceAny,
2668         "linkonce_odr" => LinkOnceODR,
2669         "private" => Private,
2670         "weak" => WeakAny,
2671         "weak_odr" => WeakODR,
2672         _ => {
2673             let span = tcx.hir().span_if_local(def_id);
2674             if let Some(span) = span {
2675                 tcx.sess.span_fatal(span, "invalid linkage specified")
2676             } else {
2677                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2678             }
2679         }
2680     }
2681 }
2682
2683 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2684     let attrs = tcx.get_attrs(id);
2685
2686     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2687     if tcx.should_inherit_track_caller(id) {
2688         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2689     }
2690
2691     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2692     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2693         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2694             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2695         }
2696     }
2697
2698     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2699
2700     let mut inline_span = None;
2701     let mut link_ordinal_span = None;
2702     let mut no_sanitize_span = None;
2703     for attr in attrs.iter() {
2704         if attr.has_name(sym::cold) {
2705             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2706         } else if attr.has_name(sym::rustc_allocator) {
2707             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2708         } else if attr.has_name(sym::ffi_returns_twice) {
2709             if tcx.is_foreign_item(id) {
2710                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2711             } else {
2712                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2713                 struct_span_err!(
2714                     tcx.sess,
2715                     attr.span,
2716                     E0724,
2717                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2718                 )
2719                 .emit();
2720             }
2721         } else if attr.has_name(sym::ffi_pure) {
2722             if tcx.is_foreign_item(id) {
2723                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2724                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2725                     struct_span_err!(
2726                         tcx.sess,
2727                         attr.span,
2728                         E0757,
2729                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2730                     )
2731                     .emit();
2732                 } else {
2733                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2734                 }
2735             } else {
2736                 // `#[ffi_pure]` is only allowed on foreign functions
2737                 struct_span_err!(
2738                     tcx.sess,
2739                     attr.span,
2740                     E0755,
2741                     "`#[ffi_pure]` may only be used on foreign functions"
2742                 )
2743                 .emit();
2744             }
2745         } else if attr.has_name(sym::ffi_const) {
2746             if tcx.is_foreign_item(id) {
2747                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2748             } else {
2749                 // `#[ffi_const]` is only allowed on foreign functions
2750                 struct_span_err!(
2751                     tcx.sess,
2752                     attr.span,
2753                     E0756,
2754                     "`#[ffi_const]` may only be used on foreign functions"
2755                 )
2756                 .emit();
2757             }
2758         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2759             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2760         } else if attr.has_name(sym::naked) {
2761             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2762         } else if attr.has_name(sym::no_mangle) {
2763             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2764         } else if attr.has_name(sym::no_coverage) {
2765             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2766         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2767             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2768         } else if attr.has_name(sym::used) {
2769             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2770         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2771             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2772                 struct_span_err!(
2773                     tcx.sess,
2774                     attr.span,
2775                     E0776,
2776                     "`#[cmse_nonsecure_entry]` requires C ABI"
2777                 )
2778                 .emit();
2779             }
2780             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2781                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2782                     .emit();
2783             }
2784             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2785         } else if attr.has_name(sym::thread_local) {
2786             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2787         } else if attr.has_name(sym::track_caller) {
2788             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2789                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2790                     .emit();
2791             }
2792             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2793                 feature_err(
2794                     &tcx.sess.parse_sess,
2795                     sym::closure_track_caller,
2796                     attr.span,
2797                     "`#[track_caller]` on closures is currently unstable",
2798                 )
2799                 .emit();
2800             }
2801             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2802         } else if attr.has_name(sym::export_name) {
2803             if let Some(s) = attr.value_str() {
2804                 if s.as_str().contains('\0') {
2805                     // `#[export_name = ...]` will be converted to a null-terminated string,
2806                     // so it may not contain any null characters.
2807                     struct_span_err!(
2808                         tcx.sess,
2809                         attr.span,
2810                         E0648,
2811                         "`export_name` may not contain null characters"
2812                     )
2813                     .emit();
2814                 }
2815                 codegen_fn_attrs.export_name = Some(s);
2816             }
2817         } else if attr.has_name(sym::target_feature) {
2818             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2819                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2820                     // The `#[target_feature]` attribute is allowed on
2821                     // WebAssembly targets on all functions, including safe
2822                     // ones. Other targets require that `#[target_feature]` is
2823                     // only applied to unsafe funtions (pending the
2824                     // `target_feature_11` feature) because on most targets
2825                     // execution of instructions that are not supported is
2826                     // considered undefined behavior. For WebAssembly which is a
2827                     // 100% safe target at execution time it's not possible to
2828                     // execute undefined instructions, and even if a future
2829                     // feature was added in some form for this it would be a
2830                     // deterministic trap. There is no undefined behavior when
2831                     // executing WebAssembly so `#[target_feature]` is allowed
2832                     // on safe functions (but again, only for WebAssembly)
2833                     //
2834                     // Note that this is also allowed if `actually_rustdoc` so
2835                     // if a target is documenting some wasm-specific code then
2836                     // it's not spuriously denied.
2837                 } else if !tcx.features().target_feature_11 {
2838                     let mut err = feature_err(
2839                         &tcx.sess.parse_sess,
2840                         sym::target_feature_11,
2841                         attr.span,
2842                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2843                     );
2844                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2845                     err.emit();
2846                 } else if let Some(local_id) = id.as_local() {
2847                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2848                 }
2849             }
2850             from_target_feature(
2851                 tcx,
2852                 id,
2853                 attr,
2854                 supported_target_features,
2855                 &mut codegen_fn_attrs.target_features,
2856             );
2857         } else if attr.has_name(sym::linkage) {
2858             if let Some(val) = attr.value_str() {
2859                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2860             }
2861         } else if attr.has_name(sym::link_section) {
2862             if let Some(val) = attr.value_str() {
2863                 if val.as_str().bytes().any(|b| b == 0) {
2864                     let msg = format!(
2865                         "illegal null byte in link_section \
2866                          value: `{}`",
2867                         &val
2868                     );
2869                     tcx.sess.span_err(attr.span, &msg);
2870                 } else {
2871                     codegen_fn_attrs.link_section = Some(val);
2872                 }
2873             }
2874         } else if attr.has_name(sym::link_name) {
2875             codegen_fn_attrs.link_name = attr.value_str();
2876         } else if attr.has_name(sym::link_ordinal) {
2877             link_ordinal_span = Some(attr.span);
2878             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2879                 codegen_fn_attrs.link_ordinal = ordinal;
2880             }
2881         } else if attr.has_name(sym::no_sanitize) {
2882             no_sanitize_span = Some(attr.span);
2883             if let Some(list) = attr.meta_item_list() {
2884                 for item in list.iter() {
2885                     if item.has_name(sym::address) {
2886                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2887                     } else if item.has_name(sym::cfi) {
2888                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2889                     } else if item.has_name(sym::memory) {
2890                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2891                     } else if item.has_name(sym::thread) {
2892                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2893                     } else if item.has_name(sym::hwaddress) {
2894                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2895                     } else {
2896                         tcx.sess
2897                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2898                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2899                             .emit();
2900                     }
2901                 }
2902             }
2903         } else if attr.has_name(sym::instruction_set) {
2904             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2905                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2906                     [NestedMetaItem::MetaItem(set)] => {
2907                         let segments =
2908                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2909                         match segments.as_slice() {
2910                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2911                                 if !tcx.sess.target.has_thumb_interworking {
2912                                     struct_span_err!(
2913                                         tcx.sess.diagnostic(),
2914                                         attr.span,
2915                                         E0779,
2916                                         "target does not support `#[instruction_set]`"
2917                                     )
2918                                     .emit();
2919                                     None
2920                                 } else if segments[1] == sym::a32 {
2921                                     Some(InstructionSetAttr::ArmA32)
2922                                 } else if segments[1] == sym::t32 {
2923                                     Some(InstructionSetAttr::ArmT32)
2924                                 } else {
2925                                     unreachable!()
2926                                 }
2927                             }
2928                             _ => {
2929                                 struct_span_err!(
2930                                     tcx.sess.diagnostic(),
2931                                     attr.span,
2932                                     E0779,
2933                                     "invalid instruction set specified",
2934                                 )
2935                                 .emit();
2936                                 None
2937                             }
2938                         }
2939                     }
2940                     [] => {
2941                         struct_span_err!(
2942                             tcx.sess.diagnostic(),
2943                             attr.span,
2944                             E0778,
2945                             "`#[instruction_set]` requires an argument"
2946                         )
2947                         .emit();
2948                         None
2949                     }
2950                     _ => {
2951                         struct_span_err!(
2952                             tcx.sess.diagnostic(),
2953                             attr.span,
2954                             E0779,
2955                             "cannot specify more than one instruction set"
2956                         )
2957                         .emit();
2958                         None
2959                     }
2960                 },
2961                 _ => {
2962                     struct_span_err!(
2963                         tcx.sess.diagnostic(),
2964                         attr.span,
2965                         E0778,
2966                         "must specify an instruction set"
2967                     )
2968                     .emit();
2969                     None
2970                 }
2971             };
2972         } else if attr.has_name(sym::repr) {
2973             codegen_fn_attrs.alignment = match attr.meta_item_list() {
2974                 Some(items) => match items.as_slice() {
2975                     [item] => match item.name_value_literal() {
2976                         Some((sym::align, literal)) => {
2977                             let alignment = rustc_attr::parse_alignment(&literal.kind);
2978
2979                             match alignment {
2980                                 Ok(align) => Some(align),
2981                                 Err(msg) => {
2982                                     struct_span_err!(
2983                                         tcx.sess.diagnostic(),
2984                                         attr.span,
2985                                         E0589,
2986                                         "invalid `repr(align)` attribute: {}",
2987                                         msg
2988                                     )
2989                                     .emit();
2990
2991                                     None
2992                                 }
2993                             }
2994                         }
2995                         _ => None,
2996                     },
2997                     [] => None,
2998                     _ => None,
2999                 },
3000                 None => None,
3001             };
3002         }
3003     }
3004
3005     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3006         if !attr.has_name(sym::inline) {
3007             return ia;
3008         }
3009         match attr.meta_kind() {
3010             Some(MetaItemKind::Word) => InlineAttr::Hint,
3011             Some(MetaItemKind::List(ref items)) => {
3012                 inline_span = Some(attr.span);
3013                 if items.len() != 1 {
3014                     struct_span_err!(
3015                         tcx.sess.diagnostic(),
3016                         attr.span,
3017                         E0534,
3018                         "expected one argument"
3019                     )
3020                     .emit();
3021                     InlineAttr::None
3022                 } else if list_contains_name(&items, sym::always) {
3023                     InlineAttr::Always
3024                 } else if list_contains_name(&items, sym::never) {
3025                     InlineAttr::Never
3026                 } else {
3027                     struct_span_err!(
3028                         tcx.sess.diagnostic(),
3029                         items[0].span(),
3030                         E0535,
3031                         "invalid argument"
3032                     )
3033                     .emit();
3034
3035                     InlineAttr::None
3036                 }
3037             }
3038             Some(MetaItemKind::NameValue(_)) => ia,
3039             None => ia,
3040         }
3041     });
3042
3043     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3044         if !attr.has_name(sym::optimize) {
3045             return ia;
3046         }
3047         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3048         match attr.meta_kind() {
3049             Some(MetaItemKind::Word) => {
3050                 err(attr.span, "expected one argument");
3051                 ia
3052             }
3053             Some(MetaItemKind::List(ref items)) => {
3054                 inline_span = Some(attr.span);
3055                 if items.len() != 1 {
3056                     err(attr.span, "expected one argument");
3057                     OptimizeAttr::None
3058                 } else if list_contains_name(&items, sym::size) {
3059                     OptimizeAttr::Size
3060                 } else if list_contains_name(&items, sym::speed) {
3061                     OptimizeAttr::Speed
3062                 } else {
3063                     err(items[0].span(), "invalid argument");
3064                     OptimizeAttr::None
3065                 }
3066             }
3067             Some(MetaItemKind::NameValue(_)) => ia,
3068             None => ia,
3069         }
3070     });
3071
3072     // #73631: closures inherit `#[target_feature]` annotations
3073     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3074         let owner_id = tcx.parent(id).expect("closure should have a parent");
3075         codegen_fn_attrs
3076             .target_features
3077             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3078     }
3079
3080     // If a function uses #[target_feature] it can't be inlined into general
3081     // purpose functions as they wouldn't have the right target features
3082     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3083     // respected.
3084     if !codegen_fn_attrs.target_features.is_empty() {
3085         if codegen_fn_attrs.inline == InlineAttr::Always {
3086             if let Some(span) = inline_span {
3087                 tcx.sess.span_err(
3088                     span,
3089                     "cannot use `#[inline(always)]` with \
3090                      `#[target_feature]`",
3091                 );
3092             }
3093         }
3094     }
3095
3096     if !codegen_fn_attrs.no_sanitize.is_empty() {
3097         if codegen_fn_attrs.inline == InlineAttr::Always {
3098             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3099                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3100                 tcx.struct_span_lint_hir(
3101                     lint::builtin::INLINE_NO_SANITIZE,
3102                     hir_id,
3103                     no_sanitize_span,
3104                     |lint| {
3105                         lint.build("`no_sanitize` will have no effect after inlining")
3106                             .span_note(inline_span, "inlining requested here")
3107                             .emit();
3108                     },
3109                 )
3110             }
3111         }
3112     }
3113
3114     // Weak lang items have the same semantics as "std internal" symbols in the
3115     // sense that they're preserved through all our LTO passes and only
3116     // strippable by the linker.
3117     //
3118     // Additionally weak lang items have predetermined symbol names.
3119     if tcx.is_weak_lang_item(id) {
3120         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3121     }
3122     if let Some(name) = weak_lang_items::link_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_item.container {
3152             if let Some(trait_item) = impl_item.trait_item_def_id {
3153                 return tcx
3154                     .codegen_fn_attrs(trait_item)
3155                     .flags
3156                     .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3157             }
3158         }
3159     }
3160
3161     false
3162 }
3163
3164 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3165     use rustc_ast::{Lit, LitIntType, LitKind};
3166     let meta_item_list = attr.meta_item_list();
3167     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3168     let sole_meta_list = match meta_item_list {
3169         Some([item]) => item.literal(),
3170         Some(_) => {
3171             tcx.sess
3172                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3173                 .note("the attribute requires exactly one argument")
3174                 .emit();
3175             return None;
3176         }
3177         _ => None,
3178     };
3179     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3180         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3181         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3182         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3183         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3184         //
3185         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3186         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3187         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3188         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3189         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3190         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3191         // about LINK.EXE failing.)
3192         if *ordinal <= u16::MAX as u128 {
3193             Some(*ordinal as u16)
3194         } else {
3195             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3196             tcx.sess
3197                 .struct_span_err(attr.span, &msg)
3198                 .note("the value may not exceed `u16::MAX`")
3199                 .emit();
3200             None
3201         }
3202     } else {
3203         tcx.sess
3204             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3205             .note("an unsuffixed integer value, e.g., `1`, is expected")
3206             .emit();
3207         None
3208     }
3209 }
3210
3211 fn check_link_name_xor_ordinal(
3212     tcx: TyCtxt<'_>,
3213     codegen_fn_attrs: &CodegenFnAttrs,
3214     inline_span: Option<Span>,
3215 ) {
3216     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3217         return;
3218     }
3219     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3220     if let Some(span) = inline_span {
3221         tcx.sess.span_err(span, msg);
3222     } else {
3223         tcx.sess.err(msg);
3224     }
3225 }
3226
3227 /// Checks the function annotated with `#[target_feature]` is not a safe
3228 /// trait method implementation, reporting an error if it is.
3229 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3230     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3231     let node = tcx.hir().get(hir_id);
3232     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3233         let parent_id = tcx.hir().get_parent_did(hir_id);
3234         let parent_item = tcx.hir().expect_item(parent_id);
3235         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3236             tcx.sess
3237                 .struct_span_err(
3238                     attr_span,
3239                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3240                 )
3241                 .span_label(attr_span, "cannot be applied to safe trait method")
3242                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3243                 .emit();
3244         }
3245     }
3246 }