compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::Attribute;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::map::Map;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         default_anon_const_substs: type_of::default_anon_const_substs,
  72         type_of: type_of::type_of,
  73         item_bounds: item_bounds::item_bounds,
  74         explicit_item_bounds: item_bounds::explicit_item_bounds,
  75         generics_of,
  76         predicates_of,
  77         predicates_defined_on,
  78         explicit_predicates_of,
  79         super_predicates_of,
  80         super_predicates_that_define_assoc_type,
  81         trait_explicit_predicates_and_bounds,
  82         type_param_predicates,
  83         trait_def,
  84         adt_def,
  85         fn_sig,
  86         impl_trait_ref,
  87         impl_polarity,
  88         is_foreign_item,
  89         static_mutability,
  90         generator_kind,
  91         codegen_fn_attrs,
  92         collect_mod_item_types,
  93         should_inherit_track_caller,
  94         ..*providers
  95     };
  96 }
  97
  98 ///////////////////////////////////////////////////////////////////////////
  99
 100 /// Context specific to some particular item. This is what implements
 101 /// `AstConv`. It has information about the predicates that are defined
 102 /// on the trait. Unfortunately, this predicate information is
 103 /// available in various different forms at various points in the
 104 /// process. So we can't just store a pointer to e.g., the AST or the
 105 /// parsed ty form, we have to be more flexible. To this end, the
 106 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 107 /// `get_type_parameter_bounds` requests, drawing the information from
 108 /// the AST (`hir::Generics`), recursively.
 109 pub struct ItemCtxt<'tcx> {
 110     tcx: TyCtxt<'tcx>,
 111     item_def_id: DefId,
 112 }
 113
 114 ///////////////////////////////////////////////////////////////////////////
 115
 116 #[derive(Default)]
 117 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 118
 119 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 120     type Map = intravisit::ErasedMap<'v>;
 121
 122     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 123         NestedVisitorMap::None
 124     }
 125     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 126         if let hir::TyKind::Infer = t.kind {
 127             self.0.push(t.span);
 128         }
 129         intravisit::walk_ty(self, t)
 130     }
 131     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 132         match generic_arg {
 133             hir::GenericArg::Infer(inf) => {
 134                 self.0.push(inf.span);
 135                 intravisit::walk_inf(self, inf);
 136             }
 137             hir::GenericArg::Type(t) => self.visit_ty(t),
 138             _ => {}
 139         }
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty {
 193             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 194                 is_fn = true;
 195
 196                 // Check if parent is const or static
 197                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 198                 let parent_node = tcx.hir().get(parent_id);
 199
 200                 is_const_or_static = matches!(
 201                     parent_node,
 202                     Node::Item(&hir::Item {
 203                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 204                         ..
 205                     }) | Node::TraitItem(&hir::TraitItem {
 206                         kind: hir::TraitItemKind::Const(..),
 207                         ..
 208                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 209                 );
 210             }
 211         }
 212
 213         // if function is wrapped around a const or static,
 214         // then don't show the suggestion
 215         if !(is_fn && is_const_or_static) {
 216             err.multipart_suggestion(
 217                 "use type parameters instead",
 218                 sugg,
 219                 Applicability::HasPlaceholders,
 220             );
 221         }
 222     }
 223     err.emit();
 224 }
 225
 226 fn reject_placeholder_type_signatures_in_item<'tcx>(
 227     tcx: TyCtxt<'tcx>,
 228     item: &'tcx hir::Item<'tcx>,
 229 ) {
 230     let (generics, suggest) = match &item.kind {
 231         hir::ItemKind::Union(_, generics)
 232         | hir::ItemKind::Enum(_, generics)
 233         | hir::ItemKind::TraitAlias(generics, _)
 234         | hir::ItemKind::Trait(_, _, generics, ..)
 235         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 236         | hir::ItemKind::Struct(_, generics) => (generics, true),
 237         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 238         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 239         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 240         _ => return,
 241     };
 242
 243     let mut visitor = PlaceholderHirTyCollector::default();
 244     visitor.visit_item(item);
 245
 246     placeholder_type_error(
 247         tcx,
 248         Some(generics.span),
 249         generics.params,
 250         visitor.0,
 251         suggest,
 252         None,
 253         item.kind.descr(),
 254     );
 255 }
 256
 257 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 258     type Map = Map<'tcx>;
 259
 260     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 261         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 262     }
 263
 264     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 265         convert_item(self.tcx, item.item_id());
 266         reject_placeholder_type_signatures_in_item(self.tcx, item);
 267         intravisit::walk_item(self, item);
 268     }
 269
 270     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 271         for param in generics.params {
 272             match param.kind {
 273                 hir::GenericParamKind::Lifetime { .. } => {}
 274                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 275                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 276                     self.tcx.ensure().type_of(def_id);
 277                 }
 278                 hir::GenericParamKind::Type { .. } => {}
 279                 hir::GenericParamKind::Const { default, .. } => {
 280                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 281                     self.tcx.ensure().type_of(def_id);
 282                     if let Some(default) = default {
 283                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 284                         // need to store default and type of default
 285                         self.tcx.ensure().type_of(default_def_id);
 286                         self.tcx.ensure().const_param_default(def_id);
 287                     }
 288                 }
 289             }
 290         }
 291         intravisit::walk_generics(self, generics);
 292     }
 293
 294     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 295         if let hir::ExprKind::Closure(..) = expr.kind {
 296             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 297             self.tcx.ensure().generics_of(def_id);
 298             self.tcx.ensure().type_of(def_id);
 299         }
 300         intravisit::walk_expr(self, expr);
 301     }
 302
 303     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 304         convert_trait_item(self.tcx, trait_item.trait_item_id());
 305         intravisit::walk_trait_item(self, trait_item);
 306     }
 307
 308     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 309         convert_impl_item(self.tcx, impl_item.impl_item_id());
 310         intravisit::walk_impl_item(self, impl_item);
 311     }
 312 }
 313
 314 ///////////////////////////////////////////////////////////////////////////
 315 // Utility types and common code for the above passes.
 316
 317 fn bad_placeholder_type<'tcx>(
 318     tcx: TyCtxt<'tcx>,
 319     mut spans: Vec<Span>,
 320     kind: &'static str,
 321 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 322     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 323
 324     spans.sort();
 325     let mut err = struct_span_err!(
 326         tcx.sess,
 327         spans.clone(),
 328         E0121,
 329         "the type placeholder `_` is not allowed within types on item signatures for {}",
 330         kind
 331     );
 332     for span in spans {
 333         err.span_label(span, "not allowed in type signatures");
 334     }
 335     err
 336 }
 337
 338 impl<'tcx> ItemCtxt<'tcx> {
 339     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 340         ItemCtxt { tcx, item_def_id }
 341     }
 342
 343     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 344         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 345     }
 346
 347     pub fn hir_id(&self) -> hir::HirId {
 348         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 349     }
 350
 351     pub fn node(&self) -> hir::Node<'tcx> {
 352         self.tcx.hir().get(self.hir_id())
 353     }
 354 }
 355
 356 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 357     fn tcx(&self) -> TyCtxt<'tcx> {
 358         self.tcx
 359     }
 360
 361     fn item_def_id(&self) -> Option<DefId> {
 362         Some(self.item_def_id)
 363     }
 364
 365     fn get_type_parameter_bounds(
 366         &self,
 367         span: Span,
 368         def_id: DefId,
 369         assoc_name: Ident,
 370     ) -> ty::GenericPredicates<'tcx> {
 371         self.tcx.at(span).type_param_predicates((
 372             self.item_def_id,
 373             def_id.expect_local(),
 374             assoc_name,
 375         ))
 376     }
 377
 378     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 379         None
 380     }
 381
 382     fn allow_ty_infer(&self) -> bool {
 383         false
 384     }
 385
 386     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 387         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 388     }
 389
 390     fn ct_infer(
 391         &self,
 392         ty: Ty<'tcx>,
 393         _: Option<&ty::GenericParamDef>,
 394         span: Span,
 395     ) -> &'tcx Const<'tcx> {
 396         bad_placeholder_type(self.tcx(), vec![span], "generic").emit();
 397         // Typeck doesn't expect erased regions to be returned from `type_of`.
 398         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 399             ty::ReErased => self.tcx.lifetimes.re_static,
 400             _ => r,
 401         });
 402         self.tcx().const_error(ty)
 403     }
 404
 405     fn projected_ty_from_poly_trait_ref(
 406         &self,
 407         span: Span,
 408         item_def_id: DefId,
 409         item_segment: &hir::PathSegment<'_>,
 410         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 411     ) -> Ty<'tcx> {
 412         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 413             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 414                 self,
 415                 self.tcx,
 416                 span,
 417                 item_def_id,
 418                 item_segment,
 419                 trait_ref.substs,
 420             );
 421             self.tcx().mk_projection(item_def_id, item_substs)
 422         } else {
 423             // There are no late-bound regions; we can just ignore the binder.
 424             let mut err = struct_span_err!(
 425                 self.tcx().sess,
 426                 span,
 427                 E0212,
 428                 "cannot use the associated type of a trait \
 429                  with uninferred generic parameters"
 430             );
 431
 432             match self.node() {
 433                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 434                     let item =
 435                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_did(self.hir_id()));
 436                     match &item.kind {
 437                         hir::ItemKind::Enum(_, generics)
 438                         | hir::ItemKind::Struct(_, generics)
 439                         | hir::ItemKind::Union(_, generics) => {
 440                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 441                             let (lt_sp, sugg) = match generics.params {
 442                                 [] => (generics.span, format!("<{}>", lt_name)),
 443                                 [bound, ..] => {
 444                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 445                                 }
 446                             };
 447                             let suggestions = vec![
 448                                 (lt_sp, sugg),
 449                                 (
 450                                     span.with_hi(item_segment.ident.span.lo()),
 451                                     format!(
 452                                         "{}::",
 453                                         // Replace the existing lifetimes with a new named lifetime.
 454                                         self.tcx
 455                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 456                                                 self.tcx.mk_region(ty::ReEarlyBound(
 457                                                     ty::EarlyBoundRegion {
 458                                                         def_id: item_def_id,
 459                                                         index: 0,
 460                                                         name: Symbol::intern(&lt_name),
 461                                                     },
 462                                                 ))
 463                                             })
 464                                             .0,
 465                                     ),
 466                                 ),
 467                             ];
 468                             err.multipart_suggestion(
 469                                 "use a fully qualified path with explicit lifetimes",
 470                                 suggestions,
 471                                 Applicability::MaybeIncorrect,
 472                             );
 473                         }
 474                         _ => {}
 475                     }
 476                 }
 477                 hir::Node::Item(hir::Item {
 478                     kind:
 479                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 480                     ..
 481                 }) => {}
 482                 hir::Node::Item(_)
 483                 | hir::Node::ForeignItem(_)
 484                 | hir::Node::TraitItem(_)
 485                 | hir::Node::ImplItem(_) => {
 486                     err.span_suggestion_verbose(
 487                         span.with_hi(item_segment.ident.span.lo()),
 488                         "use a fully qualified path with inferred lifetimes",
 489                         format!(
 490                             "{}::",
 491                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 492                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 493                         ),
 494                         Applicability::MaybeIncorrect,
 495                     );
 496                 }
 497                 _ => {}
 498             }
 499             err.emit();
 500             self.tcx().ty_error()
 501         }
 502     }
 503
 504     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 505         // Types in item signatures are not normalized to avoid undue dependencies.
 506         ty
 507     }
 508
 509     fn set_tainted_by_errors(&self) {
 510         // There's no obvious place to track this, so just let it go.
 511     }
 512
 513     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 514         // There's no place to record types from signatures?
 515     }
 516 }
 517
 518 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 519 fn get_new_lifetime_name<'tcx>(
 520     tcx: TyCtxt<'tcx>,
 521     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 522     generics: &hir::Generics<'tcx>,
 523 ) -> String {
 524     let existing_lifetimes = tcx
 525         .collect_referenced_late_bound_regions(&poly_trait_ref)
 526         .into_iter()
 527         .filter_map(|lt| {
 528             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 529                 Some(name.as_str().to_string())
 530             } else {
 531                 None
 532             }
 533         })
 534         .chain(generics.params.iter().filter_map(|param| {
 535             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 536                 Some(param.name.ident().as_str().to_string())
 537             } else {
 538                 None
 539             }
 540         }))
 541         .collect::<FxHashSet<String>>();
 542
 543     let a_to_z_repeat_n = |n| {
 544         (b'a'..=b'z').map(move |c| {
 545             let mut s = '\''.to_string();
 546             s.extend(std::iter::repeat(char::from(c)).take(n));
 547             s
 548         })
 549     };
 550
 551     // If all single char lifetime names are present, we wrap around and double the chars.
 552     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 553 }
 554
 555 /// Returns the predicates defined on `item_def_id` of the form
 556 /// `X: Foo` where `X` is the type parameter `def_id`.
 557 fn type_param_predicates(
 558     tcx: TyCtxt<'_>,
 559     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 560 ) -> ty::GenericPredicates<'_> {
 561     use rustc_hir::*;
 562
 563     // In the AST, bounds can derive from two places. Either
 564     // written inline like `<T: Foo>` or in a where-clause like
 565     // `where T: Foo`.
 566
 567     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 568     let param_owner = tcx.hir().ty_param_owner(param_id);
 569     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 570     let generics = tcx.generics_of(param_owner_def_id);
 571     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 572     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 573
 574     // Don't look for bounds where the type parameter isn't in scope.
 575     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 576         None
 577     } else {
 578         tcx.generics_of(item_def_id).parent
 579     };
 580
 581     let mut result = parent
 582         .map(|parent| {
 583             let icx = ItemCtxt::new(tcx, parent);
 584             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 585         })
 586         .unwrap_or_default();
 587     let mut extend = None;
 588
 589     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 590     let ast_generics = match tcx.hir().get(item_hir_id) {
 591         Node::TraitItem(item) => &item.generics,
 592
 593         Node::ImplItem(item) => &item.generics,
 594
 595         Node::Item(item) => {
 596             match item.kind {
 597                 ItemKind::Fn(.., ref generics, _)
 598                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 599                 | ItemKind::TyAlias(_, ref generics)
 600                 | ItemKind::OpaqueTy(OpaqueTy {
 601                     ref generics,
 602                     origin: hir::OpaqueTyOrigin::TyAlias,
 603                     ..
 604                 })
 605                 | ItemKind::Enum(_, ref generics)
 606                 | ItemKind::Struct(_, ref generics)
 607                 | ItemKind::Union(_, ref generics) => generics,
 608                 ItemKind::Trait(_, _, ref generics, ..) => {
 609                     // Implied `Self: Trait` and supertrait bounds.
 610                     if param_id == item_hir_id {
 611                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 612                         extend =
 613                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 614                     }
 615                     generics
 616                 }
 617                 _ => return result,
 618             }
 619         }
 620
 621         Node::ForeignItem(item) => match item.kind {
 622             ForeignItemKind::Fn(_, _, ref generics) => generics,
 623             _ => return result,
 624         },
 625
 626         _ => return result,
 627     };
 628
 629     let icx = ItemCtxt::new(tcx, item_def_id);
 630     let extra_predicates = extend.into_iter().chain(
 631         icx.type_parameter_bounds_in_generics(
 632             ast_generics,
 633             param_id,
 634             ty,
 635             OnlySelfBounds(true),
 636             Some(assoc_name),
 637         )
 638         .into_iter()
 639         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 640             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 641             _ => false,
 642         }),
 643     );
 644     result.predicates =
 645         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 646     result
 647 }
 648
 649 impl<'tcx> ItemCtxt<'tcx> {
 650     /// Finds bounds from `hir::Generics`. This requires scanning through the
 651     /// AST. We do this to avoid having to convert *all* the bounds, which
 652     /// would create artificial cycles. Instead, we can only convert the
 653     /// bounds for a type parameter `X` if `X::Foo` is used.
 654     fn type_parameter_bounds_in_generics(
 655         &self,
 656         ast_generics: &'tcx hir::Generics<'tcx>,
 657         param_id: hir::HirId,
 658         ty: Ty<'tcx>,
 659         only_self_bounds: OnlySelfBounds,
 660         assoc_name: Option<Ident>,
 661     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 662         let from_ty_params = ast_generics
 663             .params
 664             .iter()
 665             .filter_map(|param| match param.kind {
 666                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 667                 _ => None,
 668             })
 669             .flat_map(|bounds| bounds.iter())
 670             .filter(|b| match assoc_name {
 671                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 672                 None => true,
 673             })
 674             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 675
 676         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 677         let from_where_clauses = ast_generics
 678             .where_clause
 679             .predicates
 680             .iter()
 681             .filter_map(|wp| match *wp {
 682                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 683                 _ => None,
 684             })
 685             .flat_map(|bp| {
 686                 let bt = if bp.is_param_bound(param_def_id) {
 687                     Some(ty)
 688                 } else if !only_self_bounds.0 {
 689                     Some(self.to_ty(bp.bounded_ty))
 690                 } else {
 691                     None
 692                 };
 693                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 694
 695                 bp.bounds
 696                     .iter()
 697                     .filter(|b| match assoc_name {
 698                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 699                         None => true,
 700                     })
 701                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 702             })
 703             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 704
 705         from_ty_params.chain(from_where_clauses).collect()
 706     }
 707
 708     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 709         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 710
 711         match b {
 712             hir::GenericBound::Trait(poly_trait_ref, _) => {
 713                 let trait_ref = &poly_trait_ref.trait_ref;
 714                 if let Some(trait_did) = trait_ref.trait_def_id() {
 715                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 716                 } else {
 717                     false
 718                 }
 719             }
 720             _ => false,
 721         }
 722     }
 723 }
 724
 725 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 726     let it = tcx.hir().item(item_id);
 727     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 728     let def_id = item_id.def_id;
 729
 730     match it.kind {
 731         // These don't define types.
 732         hir::ItemKind::ExternCrate(_)
 733         | hir::ItemKind::Use(..)
 734         | hir::ItemKind::Macro(_)
 735         | hir::ItemKind::Mod(_)
 736         | hir::ItemKind::GlobalAsm(_) => {}
 737         hir::ItemKind::ForeignMod { items, .. } => {
 738             for item in items {
 739                 let item = tcx.hir().foreign_item(item.id);
 740                 tcx.ensure().generics_of(item.def_id);
 741                 tcx.ensure().type_of(item.def_id);
 742                 tcx.ensure().predicates_of(item.def_id);
 743                 match item.kind {
 744                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 745                     hir::ForeignItemKind::Static(..) => {
 746                         let mut visitor = PlaceholderHirTyCollector::default();
 747                         visitor.visit_foreign_item(item);
 748                         placeholder_type_error(
 749                             tcx,
 750                             None,
 751                             &[],
 752                             visitor.0,
 753                             false,
 754                             None,
 755                             "static variable",
 756                         );
 757                     }
 758                     _ => (),
 759                 }
 760             }
 761         }
 762         hir::ItemKind::Enum(ref enum_definition, _) => {
 763             tcx.ensure().generics_of(def_id);
 764             tcx.ensure().type_of(def_id);
 765             tcx.ensure().predicates_of(def_id);
 766             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 767         }
 768         hir::ItemKind::Impl { .. } => {
 769             tcx.ensure().generics_of(def_id);
 770             tcx.ensure().type_of(def_id);
 771             tcx.ensure().impl_trait_ref(def_id);
 772             tcx.ensure().predicates_of(def_id);
 773         }
 774         hir::ItemKind::Trait(..) => {
 775             tcx.ensure().generics_of(def_id);
 776             tcx.ensure().trait_def(def_id);
 777             tcx.at(it.span).super_predicates_of(def_id);
 778             tcx.ensure().predicates_of(def_id);
 779         }
 780         hir::ItemKind::TraitAlias(..) => {
 781             tcx.ensure().generics_of(def_id);
 782             tcx.at(it.span).super_predicates_of(def_id);
 783             tcx.ensure().predicates_of(def_id);
 784         }
 785         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 786             tcx.ensure().generics_of(def_id);
 787             tcx.ensure().type_of(def_id);
 788             tcx.ensure().predicates_of(def_id);
 789
 790             for f in struct_def.fields() {
 791                 let def_id = tcx.hir().local_def_id(f.hir_id);
 792                 tcx.ensure().generics_of(def_id);
 793                 tcx.ensure().type_of(def_id);
 794                 tcx.ensure().predicates_of(def_id);
 795             }
 796
 797             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 798                 convert_variant_ctor(tcx, ctor_hir_id);
 799             }
 800         }
 801
 802         // Desugared from `impl Trait`, so visited by the function's return type.
 803         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 804             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 805             ..
 806         }) => {}
 807
 808         // Don't call `type_of` on opaque types, since that depends on type
 809         // checking function bodies. `check_item_type` ensures that it's called
 810         // instead.
 811         hir::ItemKind::OpaqueTy(..) => {
 812             tcx.ensure().generics_of(def_id);
 813             tcx.ensure().predicates_of(def_id);
 814             tcx.ensure().explicit_item_bounds(def_id);
 815         }
 816         hir::ItemKind::TyAlias(..)
 817         | hir::ItemKind::Static(..)
 818         | hir::ItemKind::Const(..)
 819         | hir::ItemKind::Fn(..) => {
 820             tcx.ensure().generics_of(def_id);
 821             tcx.ensure().type_of(def_id);
 822             tcx.ensure().predicates_of(def_id);
 823             match it.kind {
 824                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 825                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 826                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 827                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 828                     if let hir::TyKind::TraitObject(..) = ty.kind {
 829                         let mut visitor = PlaceholderHirTyCollector::default();
 830                         visitor.visit_item(it);
 831                         placeholder_type_error(
 832                             tcx,
 833                             None,
 834                             &[],
 835                             visitor.0,
 836                             false,
 837                             None,
 838                             it.kind.descr(),
 839                         );
 840                     }
 841                 }
 842                 _ => (),
 843             }
 844         }
 845     }
 846 }
 847
 848 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 849     let trait_item = tcx.hir().trait_item(trait_item_id);
 850     tcx.ensure().generics_of(trait_item_id.def_id);
 851
 852     match trait_item.kind {
 853         hir::TraitItemKind::Fn(..) => {
 854             tcx.ensure().type_of(trait_item_id.def_id);
 855             tcx.ensure().fn_sig(trait_item_id.def_id);
 856         }
 857
 858         hir::TraitItemKind::Const(.., Some(_)) => {
 859             tcx.ensure().type_of(trait_item_id.def_id);
 860         }
 861
 862         hir::TraitItemKind::Const(..) => {
 863             tcx.ensure().type_of(trait_item_id.def_id);
 864             // Account for `const C: _;`.
 865             let mut visitor = PlaceholderHirTyCollector::default();
 866             visitor.visit_trait_item(trait_item);
 867             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 868         }
 869
 870         hir::TraitItemKind::Type(_, Some(_)) => {
 871             tcx.ensure().item_bounds(trait_item_id.def_id);
 872             tcx.ensure().type_of(trait_item_id.def_id);
 873             // Account for `type T = _;`.
 874             let mut visitor = PlaceholderHirTyCollector::default();
 875             visitor.visit_trait_item(trait_item);
 876             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 877         }
 878
 879         hir::TraitItemKind::Type(_, None) => {
 880             tcx.ensure().item_bounds(trait_item_id.def_id);
 881             // #74612: Visit and try to find bad placeholders
 882             // even if there is no concrete type.
 883             let mut visitor = PlaceholderHirTyCollector::default();
 884             visitor.visit_trait_item(trait_item);
 885
 886             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 887         }
 888     };
 889
 890     tcx.ensure().predicates_of(trait_item_id.def_id);
 891 }
 892
 893 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 894     let def_id = impl_item_id.def_id;
 895     tcx.ensure().generics_of(def_id);
 896     tcx.ensure().type_of(def_id);
 897     tcx.ensure().predicates_of(def_id);
 898     let impl_item = tcx.hir().impl_item(impl_item_id);
 899     match impl_item.kind {
 900         hir::ImplItemKind::Fn(..) => {
 901             tcx.ensure().fn_sig(def_id);
 902         }
 903         hir::ImplItemKind::TyAlias(_) => {
 904             // Account for `type T = _;`
 905             let mut visitor = PlaceholderHirTyCollector::default();
 906             visitor.visit_impl_item(impl_item);
 907
 908             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 909         }
 910         hir::ImplItemKind::Const(..) => {}
 911     }
 912 }
 913
 914 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 915     let def_id = tcx.hir().local_def_id(ctor_id);
 916     tcx.ensure().generics_of(def_id);
 917     tcx.ensure().type_of(def_id);
 918     tcx.ensure().predicates_of(def_id);
 919 }
 920
 921 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 922     let def = tcx.adt_def(def_id);
 923     let repr_type = def.repr.discr_type();
 924     let initial = repr_type.initial_discriminant(tcx);
 925     let mut prev_discr = None::<Discr<'_>>;
 926
 927     // fill the discriminant values and field types
 928     for variant in variants {
 929         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 930         prev_discr = Some(
 931             if let Some(ref e) = variant.disr_expr {
 932                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 933                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 934             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 935                 Some(discr)
 936             } else {
 937                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 938                     .span_label(
 939                         variant.span,
 940                         format!("overflowed on value after {}", prev_discr.unwrap()),
 941                     )
 942                     .note(&format!(
 943                         "explicitly set `{} = {}` if that is desired outcome",
 944                         variant.ident, wrapped_discr
 945                     ))
 946                     .emit();
 947                 None
 948             }
 949             .unwrap_or(wrapped_discr),
 950         );
 951
 952         for f in variant.data.fields() {
 953             let def_id = tcx.hir().local_def_id(f.hir_id);
 954             tcx.ensure().generics_of(def_id);
 955             tcx.ensure().type_of(def_id);
 956             tcx.ensure().predicates_of(def_id);
 957         }
 958
 959         // Convert the ctor, if any. This also registers the variant as
 960         // an item.
 961         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 962             convert_variant_ctor(tcx, ctor_hir_id);
 963         }
 964     }
 965 }
 966
 967 fn convert_variant(
 968     tcx: TyCtxt<'_>,
 969     variant_did: Option<LocalDefId>,
 970     ctor_did: Option<LocalDefId>,
 971     ident: Ident,
 972     discr: ty::VariantDiscr,
 973     def: &hir::VariantData<'_>,
 974     adt_kind: ty::AdtKind,
 975     parent_did: LocalDefId,
 976 ) -> ty::VariantDef {
 977     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 978     let fields = def
 979         .fields()
 980         .iter()
 981         .map(|f| {
 982             let fid = tcx.hir().local_def_id(f.hir_id);
 983             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 984             if let Some(prev_span) = dup_span {
 985                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 986                     field_name: f.ident,
 987                     span: f.span,
 988                     prev_span,
 989                 });
 990             } else {
 991                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 992             }
 993
 994             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 995         })
 996         .collect();
 997     let recovered = match def {
 998         hir::VariantData::Struct(_, r) => *r,
 999         _ => false,
1000     };
1001     ty::VariantDef::new(
1002         ident,
1003         variant_did.map(LocalDefId::to_def_id),
1004         ctor_did.map(LocalDefId::to_def_id),
1005         discr,
1006         fields,
1007         CtorKind::from_hir(def),
1008         adt_kind,
1009         parent_did.to_def_id(),
1010         recovered,
1011         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1012             || variant_did.map_or(false, |variant_did| {
1013                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1014             }),
1015     )
1016 }
1017
1018 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1019     use rustc_hir::*;
1020
1021     let def_id = def_id.expect_local();
1022     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1023     let item = match tcx.hir().get(hir_id) {
1024         Node::Item(item) => item,
1025         _ => bug!(),
1026     };
1027
1028     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1029     let (kind, variants) = match item.kind {
1030         ItemKind::Enum(ref def, _) => {
1031             let mut distance_from_explicit = 0;
1032             let variants = def
1033                 .variants
1034                 .iter()
1035                 .map(|v| {
1036                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1037                     let ctor_did =
1038                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1039
1040                     let discr = if let Some(ref e) = v.disr_expr {
1041                         distance_from_explicit = 0;
1042                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1043                     } else {
1044                         ty::VariantDiscr::Relative(distance_from_explicit)
1045                     };
1046                     distance_from_explicit += 1;
1047
1048                     convert_variant(
1049                         tcx,
1050                         variant_did,
1051                         ctor_did,
1052                         v.ident,
1053                         discr,
1054                         &v.data,
1055                         AdtKind::Enum,
1056                         def_id,
1057                     )
1058                 })
1059                 .collect();
1060
1061             (AdtKind::Enum, variants)
1062         }
1063         ItemKind::Struct(ref def, _) => {
1064             let variant_did = None::<LocalDefId>;
1065             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1066
1067             let variants = std::iter::once(convert_variant(
1068                 tcx,
1069                 variant_did,
1070                 ctor_did,
1071                 item.ident,
1072                 ty::VariantDiscr::Relative(0),
1073                 def,
1074                 AdtKind::Struct,
1075                 def_id,
1076             ))
1077             .collect();
1078
1079             (AdtKind::Struct, variants)
1080         }
1081         ItemKind::Union(ref def, _) => {
1082             let variant_did = None;
1083             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1084
1085             let variants = std::iter::once(convert_variant(
1086                 tcx,
1087                 variant_did,
1088                 ctor_did,
1089                 item.ident,
1090                 ty::VariantDiscr::Relative(0),
1091                 def,
1092                 AdtKind::Union,
1093                 def_id,
1094             ))
1095             .collect();
1096
1097             (AdtKind::Union, variants)
1098         }
1099         _ => bug!(),
1100     };
1101     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1102 }
1103
1104 /// Ensures that the super-predicates of the trait with a `DefId`
1105 /// of `trait_def_id` are converted and stored. This also ensures that
1106 /// the transitive super-predicates are converted.
1107 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1108     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1109     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1110 }
1111
1112 /// Ensures that the super-predicates of the trait with a `DefId`
1113 /// of `trait_def_id` are converted and stored. This also ensures that
1114 /// the transitive super-predicates are converted.
1115 fn super_predicates_that_define_assoc_type(
1116     tcx: TyCtxt<'_>,
1117     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1118 ) -> ty::GenericPredicates<'_> {
1119     debug!(
1120         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1121         trait_def_id, assoc_name
1122     );
1123     if trait_def_id.is_local() {
1124         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1125         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1126
1127         let item = match tcx.hir().get(trait_hir_id) {
1128             Node::Item(item) => item,
1129             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1130         };
1131
1132         let (generics, bounds) = match item.kind {
1133             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1134             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1135             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1136         };
1137
1138         let icx = ItemCtxt::new(tcx, trait_def_id);
1139
1140         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1141         let self_param_ty = tcx.types.self_param;
1142         let superbounds1 = if let Some(assoc_name) = assoc_name {
1143             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1144                 &icx,
1145                 self_param_ty,
1146                 bounds,
1147                 assoc_name,
1148             )
1149         } else {
1150             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1151         };
1152
1153         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1154
1155         // Convert any explicit superbounds in the where-clause,
1156         // e.g., `trait Foo where Self: Bar`.
1157         // In the case of trait aliases, however, we include all bounds in the where-clause,
1158         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1159         // as one of its "superpredicates".
1160         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1161         let superbounds2 = icx.type_parameter_bounds_in_generics(
1162             generics,
1163             item.hir_id(),
1164             self_param_ty,
1165             OnlySelfBounds(!is_trait_alias),
1166             assoc_name,
1167         );
1168
1169         // Combine the two lists to form the complete set of superbounds:
1170         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1171
1172         // Now require that immediate supertraits are converted,
1173         // which will, in turn, reach indirect supertraits.
1174         if assoc_name.is_none() {
1175             // Now require that immediate supertraits are converted,
1176             // which will, in turn, reach indirect supertraits.
1177             for &(pred, span) in superbounds {
1178                 debug!("superbound: {:?}", pred);
1179                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1180                     tcx.at(span).super_predicates_of(bound.def_id());
1181                 }
1182             }
1183         }
1184
1185         ty::GenericPredicates { parent: None, predicates: superbounds }
1186     } else {
1187         // if `assoc_name` is None, then the query should've been redirected to an
1188         // external provider
1189         assert!(assoc_name.is_some());
1190         tcx.super_predicates_of(trait_def_id)
1191     }
1192 }
1193
1194 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1195     let item = tcx.hir().expect_item(def_id.expect_local());
1196
1197     let (is_auto, unsafety) = match item.kind {
1198         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1199         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1200         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1201     };
1202
1203     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1204     if paren_sugar && !tcx.features().unboxed_closures {
1205         tcx.sess
1206             .struct_span_err(
1207                 item.span,
1208                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1209                  which traits can use parenthetical notation",
1210             )
1211             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1212             .emit();
1213     }
1214
1215     let is_marker = tcx.has_attr(def_id, sym::marker);
1216     let skip_array_during_method_dispatch =
1217         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1218     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1219         ty::trait_def::TraitSpecializationKind::Marker
1220     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1221         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1222     } else {
1223         ty::trait_def::TraitSpecializationKind::None
1224     };
1225     let def_path_hash = tcx.def_path_hash(def_id);
1226     ty::TraitDef::new(
1227         def_id,
1228         unsafety,
1229         paren_sugar,
1230         is_auto,
1231         is_marker,
1232         skip_array_during_method_dispatch,
1233         spec_kind,
1234         def_path_hash,
1235     )
1236 }
1237
1238 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1239     struct LateBoundRegionsDetector<'tcx> {
1240         tcx: TyCtxt<'tcx>,
1241         outer_index: ty::DebruijnIndex,
1242         has_late_bound_regions: Option<Span>,
1243     }
1244
1245     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1246         type Map = intravisit::ErasedMap<'tcx>;
1247
1248         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1249             NestedVisitorMap::None
1250         }
1251
1252         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1253             if self.has_late_bound_regions.is_some() {
1254                 return;
1255             }
1256             match ty.kind {
1257                 hir::TyKind::BareFn(..) => {
1258                     self.outer_index.shift_in(1);
1259                     intravisit::walk_ty(self, ty);
1260                     self.outer_index.shift_out(1);
1261                 }
1262                 _ => intravisit::walk_ty(self, ty),
1263             }
1264         }
1265
1266         fn visit_poly_trait_ref(
1267             &mut self,
1268             tr: &'tcx hir::PolyTraitRef<'tcx>,
1269             m: hir::TraitBoundModifier,
1270         ) {
1271             if self.has_late_bound_regions.is_some() {
1272                 return;
1273             }
1274             self.outer_index.shift_in(1);
1275             intravisit::walk_poly_trait_ref(self, tr, m);
1276             self.outer_index.shift_out(1);
1277         }
1278
1279         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1280             if self.has_late_bound_regions.is_some() {
1281                 return;
1282             }
1283
1284             match self.tcx.named_region(lt.hir_id) {
1285                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1286                 Some(
1287                     rl::Region::LateBound(debruijn, _, _, _)
1288                     | rl::Region::LateBoundAnon(debruijn, _, _),
1289                 ) if debruijn < self.outer_index => {}
1290                 Some(
1291                     rl::Region::LateBound(..)
1292                     | rl::Region::LateBoundAnon(..)
1293                     | rl::Region::Free(..),
1294                 )
1295                 | None => {
1296                     self.has_late_bound_regions = Some(lt.span);
1297                 }
1298             }
1299         }
1300     }
1301
1302     fn has_late_bound_regions<'tcx>(
1303         tcx: TyCtxt<'tcx>,
1304         generics: &'tcx hir::Generics<'tcx>,
1305         decl: &'tcx hir::FnDecl<'tcx>,
1306     ) -> Option<Span> {
1307         let mut visitor = LateBoundRegionsDetector {
1308             tcx,
1309             outer_index: ty::INNERMOST,
1310             has_late_bound_regions: None,
1311         };
1312         for param in generics.params {
1313             if let GenericParamKind::Lifetime { .. } = param.kind {
1314                 if tcx.is_late_bound(param.hir_id) {
1315                     return Some(param.span);
1316                 }
1317             }
1318         }
1319         visitor.visit_fn_decl(decl);
1320         visitor.has_late_bound_regions
1321     }
1322
1323     match node {
1324         Node::TraitItem(item) => match item.kind {
1325             hir::TraitItemKind::Fn(ref sig, _) => {
1326                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1327             }
1328             _ => None,
1329         },
1330         Node::ImplItem(item) => match item.kind {
1331             hir::ImplItemKind::Fn(ref sig, _) => {
1332                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1333             }
1334             _ => None,
1335         },
1336         Node::ForeignItem(item) => match item.kind {
1337             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1338                 has_late_bound_regions(tcx, generics, fn_decl)
1339             }
1340             _ => None,
1341         },
1342         Node::Item(item) => match item.kind {
1343             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1344                 has_late_bound_regions(tcx, generics, sig.decl)
1345             }
1346             _ => None,
1347         },
1348         _ => None,
1349     }
1350 }
1351
1352 struct AnonConstInParamTyDetector {
1353     in_param_ty: bool,
1354     found_anon_const_in_param_ty: bool,
1355     ct: HirId,
1356 }
1357
1358 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1359     type Map = intravisit::ErasedMap<'v>;
1360
1361     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1362         NestedVisitorMap::None
1363     }
1364
1365     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1366         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1367             let prev = self.in_param_ty;
1368             self.in_param_ty = true;
1369             self.visit_ty(ty);
1370             self.in_param_ty = prev;
1371         }
1372     }
1373
1374     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1375         if self.in_param_ty && self.ct == c.hir_id {
1376             self.found_anon_const_in_param_ty = true;
1377         } else {
1378             intravisit::walk_anon_const(self, c)
1379         }
1380     }
1381 }
1382
1383 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1384     use rustc_hir::*;
1385
1386     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1387
1388     let node = tcx.hir().get(hir_id);
1389     let parent_def_id = match node {
1390         Node::ImplItem(_)
1391         | Node::TraitItem(_)
1392         | Node::Variant(_)
1393         | Node::Ctor(..)
1394         | Node::Field(_) => {
1395             let parent_id = tcx.hir().get_parent_item(hir_id);
1396             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1397         }
1398         // FIXME(#43408) always enable this once `lazy_normalization` is
1399         // stable enough and does not need a feature gate anymore.
1400         Node::AnonConst(_) => {
1401             let parent_id = tcx.hir().get_parent_item(hir_id);
1402             let parent_def_id = tcx.hir().local_def_id(parent_id);
1403
1404             let mut in_param_ty = false;
1405             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1406                 if let Some(generics) = node.generics() {
1407                     let mut visitor = AnonConstInParamTyDetector {
1408                         in_param_ty: false,
1409                         found_anon_const_in_param_ty: false,
1410                         ct: hir_id,
1411                     };
1412
1413                     visitor.visit_generics(generics);
1414                     in_param_ty = visitor.found_anon_const_in_param_ty;
1415                     break;
1416                 }
1417             }
1418
1419             if in_param_ty {
1420                 // We do not allow generic parameters in anon consts if we are inside
1421                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1422                 None
1423             } else if tcx.lazy_normalization() {
1424                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1425                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1426                     //
1427                     // struct Foo<const N: usize = { .. }>;
1428                     //        ^^^       ^          ^^^^^^ def id of this anon const
1429                     //        ^         ^ param_id
1430                     //        ^ parent_def_id
1431                     //
1432                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1433                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1434                     //
1435                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1436                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1437                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1438                     //
1439                     // We fix this by having this function return the parent's generics ourselves and truncating the
1440                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1441                     //
1442                     // For the above code example that means we want `substs: []`
1443                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1444                     // the def id of the `{ N + 1 }` anon const
1445                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1446                     //
1447                     // This has some implications for how we get the predicates available to the anon const
1448                     // see `explicit_predicates_of` for more information on this
1449                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1450                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1451                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1452                     // In the above example this would be .params[..N#0]
1453                     let params = generics.params[..param_def_idx as usize].to_owned();
1454                     let param_def_id_to_index =
1455                         params.iter().map(|param| (param.def_id, param.index)).collect();
1456
1457                     return ty::Generics {
1458                         // we set the parent of these generics to be our parent's parent so that we
1459                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1460                         // struct Foo<const N: usize, const M: usize = { ... }>;
1461                         parent: generics.parent,
1462                         parent_count: generics.parent_count,
1463                         params,
1464                         param_def_id_to_index,
1465                         has_self: generics.has_self,
1466                         has_late_bound_regions: generics.has_late_bound_regions,
1467                     };
1468                 }
1469
1470                 // HACK(eddyb) this provides the correct generics when
1471                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1472                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1473                 //
1474                 // Note that we do not supply the parent generics when using
1475                 // `min_const_generics`.
1476                 Some(parent_def_id.to_def_id())
1477             } else {
1478                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1479                 match parent_node {
1480                     // HACK(eddyb) this provides the correct generics for repeat
1481                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1482                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1483                     // as they shouldn't be able to cause query cycle errors.
1484                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1485                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1486                         if constant.hir_id == hir_id =>
1487                     {
1488                         Some(parent_def_id.to_def_id())
1489                     }
1490                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1491                         Some(tcx.typeck_root_def_id(def_id))
1492                     }
1493                     _ => None,
1494                 }
1495             }
1496         }
1497         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1498             Some(tcx.typeck_root_def_id(def_id))
1499         }
1500         Node::Item(item) => match item.kind {
1501             ItemKind::OpaqueTy(hir::OpaqueTy {
1502                 origin:
1503                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1504                 ..
1505             }) => Some(fn_def_id.to_def_id()),
1506             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1507                 let parent_id = tcx.hir().get_parent_item(hir_id);
1508                 assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1509                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1510                 // Opaque types are always nested within another item, and
1511                 // inherit the generics of the item.
1512                 Some(tcx.hir().local_def_id(parent_id).to_def_id())
1513             }
1514             _ => None,
1515         },
1516         _ => None,
1517     };
1518
1519     let mut opt_self = None;
1520     let mut allow_defaults = false;
1521
1522     let no_generics = hir::Generics::empty();
1523     let ast_generics = match node {
1524         Node::TraitItem(item) => &item.generics,
1525
1526         Node::ImplItem(item) => &item.generics,
1527
1528         Node::Item(item) => {
1529             match item.kind {
1530                 ItemKind::Fn(.., ref generics, _)
1531                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1532
1533                 ItemKind::TyAlias(_, ref generics)
1534                 | ItemKind::Enum(_, ref generics)
1535                 | ItemKind::Struct(_, ref generics)
1536                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1537                 | ItemKind::Union(_, ref generics) => {
1538                     allow_defaults = true;
1539                     generics
1540                 }
1541
1542                 ItemKind::Trait(_, _, ref generics, ..)
1543                 | ItemKind::TraitAlias(ref generics, ..) => {
1544                     // Add in the self type parameter.
1545                     //
1546                     // Something of a hack: use the node id for the trait, also as
1547                     // the node id for the Self type parameter.
1548                     let param_id = item.def_id;
1549
1550                     opt_self = Some(ty::GenericParamDef {
1551                         index: 0,
1552                         name: kw::SelfUpper,
1553                         def_id: param_id.to_def_id(),
1554                         pure_wrt_drop: false,
1555                         kind: ty::GenericParamDefKind::Type {
1556                             has_default: false,
1557                             object_lifetime_default: rl::Set1::Empty,
1558                             synthetic: false,
1559                         },
1560                     });
1561
1562                     allow_defaults = true;
1563                     generics
1564                 }
1565
1566                 _ => &no_generics,
1567             }
1568         }
1569
1570         Node::ForeignItem(item) => match item.kind {
1571             ForeignItemKind::Static(..) => &no_generics,
1572             ForeignItemKind::Fn(_, _, ref generics) => generics,
1573             ForeignItemKind::Type => &no_generics,
1574         },
1575
1576         _ => &no_generics,
1577     };
1578
1579     let has_self = opt_self.is_some();
1580     let mut parent_has_self = false;
1581     let mut own_start = has_self as u32;
1582     let parent_count = parent_def_id.map_or(0, |def_id| {
1583         let generics = tcx.generics_of(def_id);
1584         assert!(!has_self);
1585         parent_has_self = generics.has_self;
1586         own_start = generics.count() as u32;
1587         generics.parent_count + generics.params.len()
1588     });
1589
1590     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1591
1592     if let Some(opt_self) = opt_self {
1593         params.push(opt_self);
1594     }
1595
1596     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1597     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1598         name: param.name.ident().name,
1599         index: own_start + i as u32,
1600         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1601         pure_wrt_drop: param.pure_wrt_drop,
1602         kind: ty::GenericParamDefKind::Lifetime,
1603     }));
1604
1605     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1606
1607     // Now create the real type and const parameters.
1608     let type_start = own_start - has_self as u32 + params.len() as u32;
1609     let mut i = 0;
1610
1611     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1612         GenericParamKind::Lifetime { .. } => None,
1613         GenericParamKind::Type { ref default, synthetic, .. } => {
1614             if !allow_defaults && default.is_some() {
1615                 if !tcx.features().default_type_parameter_fallback {
1616                     tcx.struct_span_lint_hir(
1617                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1618                         param.hir_id,
1619                         param.span,
1620                         |lint| {
1621                             lint.build(
1622                                 "defaults for type parameters are only allowed in \
1623                                  `struct`, `enum`, `type`, or `trait` definitions",
1624                             )
1625                             .emit();
1626                         },
1627                     );
1628                 }
1629             }
1630
1631             let kind = ty::GenericParamDefKind::Type {
1632                 has_default: default.is_some(),
1633                 object_lifetime_default: object_lifetime_defaults
1634                     .as_ref()
1635                     .map_or(rl::Set1::Empty, |o| o[i]),
1636                 synthetic,
1637             };
1638
1639             let param_def = ty::GenericParamDef {
1640                 index: type_start + i as u32,
1641                 name: param.name.ident().name,
1642                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1643                 pure_wrt_drop: param.pure_wrt_drop,
1644                 kind,
1645             };
1646             i += 1;
1647             Some(param_def)
1648         }
1649         GenericParamKind::Const { default, .. } => {
1650             if !allow_defaults && default.is_some() {
1651                 tcx.sess.span_err(
1652                     param.span,
1653                     "defaults for const parameters are only allowed in \
1654                     `struct`, `enum`, `type`, or `trait` definitions",
1655                 );
1656             }
1657
1658             let param_def = ty::GenericParamDef {
1659                 index: type_start + i as u32,
1660                 name: param.name.ident().name,
1661                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1662                 pure_wrt_drop: param.pure_wrt_drop,
1663                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1664             };
1665             i += 1;
1666             Some(param_def)
1667         }
1668     }));
1669
1670     // provide junk type parameter defs - the only place that
1671     // cares about anything but the length is instantiation,
1672     // and we don't do that for closures.
1673     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1674         let dummy_args = if gen.is_some() {
1675             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1676         } else {
1677             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1678         };
1679
1680         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1681             index: type_start + i as u32,
1682             name: Symbol::intern(arg),
1683             def_id,
1684             pure_wrt_drop: false,
1685             kind: ty::GenericParamDefKind::Type {
1686                 has_default: false,
1687                 object_lifetime_default: rl::Set1::Empty,
1688                 synthetic: false,
1689             },
1690         }));
1691     }
1692
1693     // provide junk type parameter defs for const blocks.
1694     if let Node::AnonConst(_) = node {
1695         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1696         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1697             params.push(ty::GenericParamDef {
1698                 index: type_start,
1699                 name: Symbol::intern("<const_ty>"),
1700                 def_id,
1701                 pure_wrt_drop: false,
1702                 kind: ty::GenericParamDefKind::Type {
1703                     has_default: false,
1704                     object_lifetime_default: rl::Set1::Empty,
1705                     synthetic: false,
1706                 },
1707             });
1708         }
1709     }
1710
1711     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1712
1713     ty::Generics {
1714         parent: parent_def_id,
1715         parent_count,
1716         params,
1717         param_def_id_to_index,
1718         has_self: has_self || parent_has_self,
1719         has_late_bound_regions: has_late_bound_regions(tcx, node),
1720     }
1721 }
1722
1723 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1724     generic_args.iter().any(|arg| match arg {
1725         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1726         hir::GenericArg::Infer(_) => true,
1727         _ => false,
1728     })
1729 }
1730
1731 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1732 /// use inference to provide suggestions for the appropriate type if possible.
1733 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1734     use hir::TyKind::*;
1735     match &ty.kind {
1736         Infer => true,
1737         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1738         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1739         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1740         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1741         Path(hir::QPath::TypeRelative(ty, segment)) => {
1742             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1743         }
1744         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1745             ty_opt.map_or(false, is_suggestable_infer_ty)
1746                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1747         }
1748         _ => false,
1749     }
1750 }
1751
1752 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1753     if let hir::FnRetTy::Return(ty) = output {
1754         if is_suggestable_infer_ty(ty) {
1755             return Some(&*ty);
1756         }
1757     }
1758     None
1759 }
1760
1761 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1762     use rustc_hir::Node::*;
1763     use rustc_hir::*;
1764
1765     let def_id = def_id.expect_local();
1766     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1767
1768     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1769
1770     match tcx.hir().get(hir_id) {
1771         TraitItem(hir::TraitItem {
1772             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1773             ident,
1774             generics,
1775             ..
1776         })
1777         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1778         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1779             match get_infer_ret_ty(&sig.decl.output) {
1780                 Some(ty) => {
1781                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1782                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1783                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1784                         ty::ReErased => tcx.lifetimes.re_static,
1785                         _ => r,
1786                     });
1787                     let fn_sig = ty::Binder::dummy(fn_sig);
1788
1789                     let mut visitor = PlaceholderHirTyCollector::default();
1790                     visitor.visit_ty(ty);
1791                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
1792                     let ret_ty = fn_sig.skip_binder().output();
1793                     if !ret_ty.references_error() {
1794                         if !ret_ty.is_closure() {
1795                             let ret_ty_str = match ret_ty.kind() {
1796                                 // Suggest a function pointer return type instead of a unique function definition
1797                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1798                                 // syntax)
1799                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1800                                 _ => ret_ty.to_string(),
1801                             };
1802                             diag.span_suggestion(
1803                                 ty.span,
1804                                 "replace with the correct return type",
1805                                 ret_ty_str,
1806                                 Applicability::MaybeIncorrect,
1807                             );
1808                         } else {
1809                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1810                             // to prevent the user from getting a papercut while trying to use the unique closure
1811                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1812                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1813                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1814                         }
1815                     }
1816                     diag.emit();
1817
1818                     fn_sig
1819                 }
1820                 None => <dyn AstConv<'_>>::ty_of_fn(
1821                     &icx,
1822                     hir_id,
1823                     sig.header.unsafety,
1824                     sig.header.abi,
1825                     sig.decl,
1826                     generics,
1827                     Some(ident.span),
1828                     None,
1829                 ),
1830             }
1831         }
1832
1833         TraitItem(hir::TraitItem {
1834             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1835             ident,
1836             generics,
1837             ..
1838         }) => <dyn AstConv<'_>>::ty_of_fn(
1839             &icx,
1840             hir_id,
1841             header.unsafety,
1842             header.abi,
1843             decl,
1844             generics,
1845             Some(ident.span),
1846             None,
1847         ),
1848
1849         ForeignItem(&hir::ForeignItem {
1850             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1851         }) => {
1852             let abi = tcx.hir().get_foreign_abi(hir_id);
1853             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1854         }
1855
1856         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1857             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1858             let inputs =
1859                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1860             ty::Binder::dummy(tcx.mk_fn_sig(
1861                 inputs,
1862                 ty,
1863                 false,
1864                 hir::Unsafety::Normal,
1865                 abi::Abi::Rust,
1866             ))
1867         }
1868
1869         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1870             // Closure signatures are not like other function
1871             // signatures and cannot be accessed through `fn_sig`. For
1872             // example, a closure signature excludes the `self`
1873             // argument. In any case they are embedded within the
1874             // closure type as part of the `ClosureSubsts`.
1875             //
1876             // To get the signature of a closure, you should use the
1877             // `sig` method on the `ClosureSubsts`:
1878             //
1879             //    substs.as_closure().sig(def_id, tcx)
1880             bug!(
1881                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1882             );
1883         }
1884
1885         x => {
1886             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1887         }
1888     }
1889 }
1890
1891 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1892     let icx = ItemCtxt::new(tcx, def_id);
1893     match tcx.hir().expect_item(def_id.expect_local()).kind {
1894         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1895             let selfty = tcx.type_of(def_id);
1896             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1897         }),
1898         _ => bug!(),
1899     }
1900 }
1901
1902 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1903     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1904     let item = tcx.hir().expect_item(def_id.expect_local());
1905     match &item.kind {
1906         hir::ItemKind::Impl(hir::Impl {
1907             polarity: hir::ImplPolarity::Negative(span),
1908             of_trait,
1909             ..
1910         }) => {
1911             if is_rustc_reservation {
1912                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1913                 tcx.sess.span_err(span, "reservation impls can't be negative");
1914             }
1915             ty::ImplPolarity::Negative
1916         }
1917         hir::ItemKind::Impl(hir::Impl {
1918             polarity: hir::ImplPolarity::Positive,
1919             of_trait: None,
1920             ..
1921         }) => {
1922             if is_rustc_reservation {
1923                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1924             }
1925             ty::ImplPolarity::Positive
1926         }
1927         hir::ItemKind::Impl(hir::Impl {
1928             polarity: hir::ImplPolarity::Positive,
1929             of_trait: Some(_),
1930             ..
1931         }) => {
1932             if is_rustc_reservation {
1933                 ty::ImplPolarity::Reservation
1934             } else {
1935                 ty::ImplPolarity::Positive
1936             }
1937         }
1938         item => bug!("impl_polarity: {:?} not an impl", item),
1939     }
1940 }
1941
1942 /// Returns the early-bound lifetimes declared in this generics
1943 /// listing. For anything other than fns/methods, this is just all
1944 /// the lifetimes that are declared. For fns or methods, we have to
1945 /// screen out those that do not appear in any where-clauses etc using
1946 /// `resolve_lifetime::early_bound_lifetimes`.
1947 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1948     tcx: TyCtxt<'tcx>,
1949     generics: &'a hir::Generics<'a>,
1950 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1951     generics.params.iter().filter(move |param| match param.kind {
1952         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1953         _ => false,
1954     })
1955 }
1956
1957 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1958 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1959 /// inferred constraints concerning which regions outlive other regions.
1960 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1961     debug!("predicates_defined_on({:?})", def_id);
1962     let mut result = tcx.explicit_predicates_of(def_id);
1963     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1964     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1965     if !inferred_outlives.is_empty() {
1966         debug!(
1967             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1968             def_id, inferred_outlives,
1969         );
1970         if result.predicates.is_empty() {
1971             result.predicates = inferred_outlives;
1972         } else {
1973             result.predicates = tcx
1974                 .arena
1975                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1976         }
1977     }
1978
1979     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1980     result
1981 }
1982
1983 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1984 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1985 /// `Self: Trait` predicates for traits.
1986 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1987     let mut result = tcx.predicates_defined_on(def_id);
1988
1989     if tcx.is_trait(def_id) {
1990         // For traits, add `Self: Trait` predicate. This is
1991         // not part of the predicates that a user writes, but it
1992         // is something that one must prove in order to invoke a
1993         // method or project an associated type.
1994         //
1995         // In the chalk setup, this predicate is not part of the
1996         // "predicates" for a trait item. But it is useful in
1997         // rustc because if you directly (e.g.) invoke a trait
1998         // method like `Trait::method(...)`, you must naturally
1999         // prove that the trait applies to the types that were
2000         // used, and adding the predicate into this list ensures
2001         // that this is done.
2002         //
2003         // We use a DUMMY_SP here as a way to signal trait bounds that come
2004         // from the trait itself that *shouldn't* be shown as the source of
2005         // an obligation and instead be skipped. Otherwise we'd use
2006         // `tcx.def_span(def_id);`
2007         let span = rustc_span::DUMMY_SP;
2008         result.predicates =
2009             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2010                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2011                 span,
2012             ))));
2013     }
2014     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2015     result
2016 }
2017
2018 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2019 /// N.B., this does not include any implied/inferred constraints.
2020 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2021     use rustc_hir::*;
2022
2023     debug!("explicit_predicates_of(def_id={:?})", def_id);
2024
2025     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2026     let node = tcx.hir().get(hir_id);
2027
2028     let mut is_trait = None;
2029     let mut is_default_impl_trait = None;
2030
2031     let icx = ItemCtxt::new(tcx, def_id);
2032
2033     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2034
2035     // We use an `IndexSet` to preserves order of insertion.
2036     // Preserving the order of insertion is important here so as not to break UI tests.
2037     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2038
2039     let ast_generics = match node {
2040         Node::TraitItem(item) => &item.generics,
2041
2042         Node::ImplItem(item) => &item.generics,
2043
2044         Node::Item(item) => {
2045             match item.kind {
2046                 ItemKind::Impl(ref impl_) => {
2047                     if impl_.defaultness.is_default() {
2048                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2049                     }
2050                     &impl_.generics
2051                 }
2052                 ItemKind::Fn(.., ref generics, _)
2053                 | ItemKind::TyAlias(_, ref generics)
2054                 | ItemKind::Enum(_, ref generics)
2055                 | ItemKind::Struct(_, ref generics)
2056                 | ItemKind::Union(_, ref generics) => generics,
2057
2058                 ItemKind::Trait(_, _, ref generics, ..) => {
2059                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2060                     generics
2061                 }
2062                 ItemKind::TraitAlias(ref generics, _) => {
2063                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2064                     generics
2065                 }
2066                 ItemKind::OpaqueTy(OpaqueTy {
2067                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2068                     ..
2069                 }) => {
2070                     // return-position impl trait
2071                     //
2072                     // We don't inherit predicates from the parent here:
2073                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2074                     // then the return type is `f::<'static, T>::{{opaque}}`.
2075                     //
2076                     // If we inherited the predicates of `f` then we would
2077                     // require that `T: 'static` to show that the return
2078                     // type is well-formed.
2079                     //
2080                     // The only way to have something with this opaque type
2081                     // is from the return type of the containing function,
2082                     // which will ensure that the function's predicates
2083                     // hold.
2084                     return ty::GenericPredicates { parent: None, predicates: &[] };
2085                 }
2086                 ItemKind::OpaqueTy(OpaqueTy {
2087                     ref generics,
2088                     origin: hir::OpaqueTyOrigin::TyAlias,
2089                     ..
2090                 }) => {
2091                     // type-alias impl trait
2092                     generics
2093                 }
2094
2095                 _ => NO_GENERICS,
2096             }
2097         }
2098
2099         Node::ForeignItem(item) => match item.kind {
2100             ForeignItemKind::Static(..) => NO_GENERICS,
2101             ForeignItemKind::Fn(_, _, ref generics) => generics,
2102             ForeignItemKind::Type => NO_GENERICS,
2103         },
2104
2105         _ => NO_GENERICS,
2106     };
2107
2108     let generics = tcx.generics_of(def_id);
2109     let parent_count = generics.parent_count as u32;
2110     let has_own_self = generics.has_self && parent_count == 0;
2111
2112     // Below we'll consider the bounds on the type parameters (including `Self`)
2113     // and the explicit where-clauses, but to get the full set of predicates
2114     // on a trait we need to add in the supertrait bounds and bounds found on
2115     // associated types.
2116     if let Some(_trait_ref) = is_trait {
2117         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2118     }
2119
2120     // In default impls, we can assume that the self type implements
2121     // the trait. So in:
2122     //
2123     //     default impl Foo for Bar { .. }
2124     //
2125     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2126     // (see below). Recall that a default impl is not itself an impl, but rather a
2127     // set of defaults that can be incorporated into another impl.
2128     if let Some(trait_ref) = is_default_impl_trait {
2129         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2130     }
2131
2132     // Collect the region predicates that were declared inline as
2133     // well. In the case of parameters declared on a fn or method, we
2134     // have to be careful to only iterate over early-bound regions.
2135     let mut index = parent_count + has_own_self as u32;
2136     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2137         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2138             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2139             index,
2140             name: param.name.ident().name,
2141         }));
2142         index += 1;
2143
2144         match param.kind {
2145             GenericParamKind::Lifetime { .. } => {
2146                 param.bounds.iter().for_each(|bound| match bound {
2147                     hir::GenericBound::Outlives(lt) => {
2148                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2149                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2150                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2151                     }
2152                     _ => bug!(),
2153                 });
2154             }
2155             _ => bug!(),
2156         }
2157     }
2158
2159     // Collect the predicates that were written inline by the user on each
2160     // type parameter (e.g., `<T: Foo>`).
2161     for param in ast_generics.params {
2162         match param.kind {
2163             // We already dealt with early bound lifetimes above.
2164             GenericParamKind::Lifetime { .. } => (),
2165             GenericParamKind::Type { .. } => {
2166                 let name = param.name.ident().name;
2167                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2168                 index += 1;
2169
2170                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2171                 // Params are implicitly sized unless a `?Sized` bound is found
2172                 <dyn AstConv<'_>>::add_implicitly_sized(
2173                     &icx,
2174                     &mut bounds,
2175                     param.bounds,
2176                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2177                     param.span,
2178                 );
2179                 predicates.extend(bounds.predicates(tcx, param_ty));
2180             }
2181             GenericParamKind::Const { .. } => {
2182                 // Bounds on const parameters are currently not possible.
2183                 debug_assert!(param.bounds.is_empty());
2184                 index += 1;
2185             }
2186         }
2187     }
2188
2189     // Add in the bounds that appear in the where-clause.
2190     let where_clause = &ast_generics.where_clause;
2191     for predicate in where_clause.predicates {
2192         match predicate {
2193             hir::WherePredicate::BoundPredicate(bound_pred) => {
2194                 let ty = icx.to_ty(bound_pred.bounded_ty);
2195                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2196
2197                 // Keep the type around in a dummy predicate, in case of no bounds.
2198                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2199                 // is still checked for WF.
2200                 if bound_pred.bounds.is_empty() {
2201                     if let ty::Param(_) = ty.kind() {
2202                         // This is a `where T:`, which can be in the HIR from the
2203                         // transformation that moves `?Sized` to `T`'s declaration.
2204                         // We can skip the predicate because type parameters are
2205                         // trivially WF, but also we *should*, to avoid exposing
2206                         // users who never wrote `where Type:,` themselves, to
2207                         // compiler/tooling bugs from not handling WF predicates.
2208                     } else {
2209                         let span = bound_pred.bounded_ty.span;
2210                         let re_root_empty = tcx.lifetimes.re_root_empty;
2211                         let predicate = ty::Binder::bind_with_vars(
2212                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2213                                 ty,
2214                                 re_root_empty,
2215                             )),
2216                             bound_vars,
2217                         );
2218                         predicates.insert((predicate.to_predicate(tcx), span));
2219                     }
2220                 }
2221
2222                 let mut bounds = Bounds::default();
2223                 <dyn AstConv<'_>>::add_bounds(
2224                     &icx,
2225                     ty,
2226                     bound_pred.bounds.iter(),
2227                     &mut bounds,
2228                     bound_vars,
2229                 );
2230                 predicates.extend(bounds.predicates(tcx, ty));
2231             }
2232
2233             hir::WherePredicate::RegionPredicate(region_pred) => {
2234                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2235                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2236                     let (r2, span) = match bound {
2237                         hir::GenericBound::Outlives(lt) => {
2238                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2239                         }
2240                         _ => bug!(),
2241                     };
2242                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2243                         ty::OutlivesPredicate(r1, r2),
2244                     ))
2245                     .to_predicate(icx.tcx);
2246
2247                     (pred, span)
2248                 }))
2249             }
2250
2251             hir::WherePredicate::EqPredicate(..) => {
2252                 // FIXME(#20041)
2253             }
2254         }
2255     }
2256
2257     if tcx.features().generic_const_exprs {
2258         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2259     }
2260
2261     let mut predicates: Vec<_> = predicates.into_iter().collect();
2262
2263     // Subtle: before we store the predicates into the tcx, we
2264     // sort them so that predicates like `T: Foo<Item=U>` come
2265     // before uses of `U`.  This avoids false ambiguity errors
2266     // in trait checking. See `setup_constraining_predicates`
2267     // for details.
2268     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2269         let self_ty = tcx.type_of(def_id);
2270         let trait_ref = tcx.impl_trait_ref(def_id);
2271         cgp::setup_constraining_predicates(
2272             tcx,
2273             &mut predicates,
2274             trait_ref,
2275             &mut cgp::parameters_for_impl(tcx, self_ty, trait_ref),
2276         );
2277     }
2278
2279     let result = ty::GenericPredicates {
2280         parent: generics.parent,
2281         predicates: tcx.arena.alloc_from_iter(predicates),
2282     };
2283     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2284     result
2285 }
2286
2287 fn const_evaluatable_predicates_of<'tcx>(
2288     tcx: TyCtxt<'tcx>,
2289     def_id: LocalDefId,
2290 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2291     struct ConstCollector<'tcx> {
2292         tcx: TyCtxt<'tcx>,
2293         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2294     }
2295
2296     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2297         type Map = Map<'tcx>;
2298
2299         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2300             intravisit::NestedVisitorMap::None
2301         }
2302
2303         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2304             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2305             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2306             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2307                 assert_eq!(uv.promoted, None);
2308                 let span = self.tcx.hir().span(c.hir_id);
2309                 self.preds.insert((
2310                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2311                         .to_predicate(self.tcx),
2312                     span,
2313                 ));
2314             }
2315         }
2316
2317         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2318             // Do not look into const param defaults,
2319             // these get checked when they are actually instantiated.
2320             //
2321             // We do not want the following to error:
2322             //
2323             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2324             //     struct Bar<const N: usize>(Foo<N, 3>);
2325         }
2326     }
2327
2328     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2329     let node = tcx.hir().get(hir_id);
2330
2331     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2332     if let hir::Node::Item(item) = node {
2333         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2334             if let Some(of_trait) = &impl_.of_trait {
2335                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2336                 collector.visit_trait_ref(of_trait);
2337             }
2338
2339             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2340             collector.visit_ty(impl_.self_ty);
2341         }
2342     }
2343
2344     if let Some(generics) = node.generics() {
2345         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2346         collector.visit_generics(generics);
2347     }
2348
2349     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2350         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2351         collector.visit_fn_decl(fn_sig.decl);
2352     }
2353     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2354
2355     collector.preds
2356 }
2357
2358 fn trait_explicit_predicates_and_bounds(
2359     tcx: TyCtxt<'_>,
2360     def_id: LocalDefId,
2361 ) -> ty::GenericPredicates<'_> {
2362     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2363     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2364 }
2365
2366 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2367     let def_kind = tcx.def_kind(def_id);
2368     if let DefKind::Trait = def_kind {
2369         // Remove bounds on associated types from the predicates, they will be
2370         // returned by `explicit_item_bounds`.
2371         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2372         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2373
2374         let is_assoc_item_ty = |ty: Ty<'_>| {
2375             // For a predicate from a where clause to become a bound on an
2376             // associated type:
2377             // * It must use the identity substs of the item.
2378             //     * Since any generic parameters on the item are not in scope,
2379             //       this means that the item is not a GAT, and its identity
2380             //       substs are the same as the trait's.
2381             // * It must be an associated type for this trait (*not* a
2382             //   supertrait).
2383             if let ty::Projection(projection) = ty.kind() {
2384                 projection.substs == trait_identity_substs
2385                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2386             } else {
2387                 false
2388             }
2389         };
2390
2391         let predicates: Vec<_> = predicates_and_bounds
2392             .predicates
2393             .iter()
2394             .copied()
2395             .filter(|(pred, _)| match pred.kind().skip_binder() {
2396                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2397                 ty::PredicateKind::Projection(proj) => {
2398                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2399                 }
2400                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2401                 _ => true,
2402             })
2403             .collect();
2404         if predicates.len() == predicates_and_bounds.predicates.len() {
2405             predicates_and_bounds
2406         } else {
2407             ty::GenericPredicates {
2408                 parent: predicates_and_bounds.parent,
2409                 predicates: tcx.arena.alloc_slice(&predicates),
2410             }
2411         }
2412     } else {
2413         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2414             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2415             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2416                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2417                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2418                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2419                 //
2420                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2421                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2422                 //        ^^^                                             explicit_predicates_of on
2423                 //        parent item we dont have set as the
2424                 //        parent of generics returned by `generics_of`
2425                 //
2426                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2427                 let item_id = tcx.hir().get_parent_item(hir_id);
2428                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2429                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2430                 return tcx.explicit_predicates_of(item_def_id);
2431             }
2432         }
2433         gather_explicit_predicates_of(tcx, def_id)
2434     }
2435 }
2436
2437 /// Converts a specific `GenericBound` from the AST into a set of
2438 /// predicates that apply to the self type. A vector is returned
2439 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2440 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2441 /// and `<T as Bar>::X == i32`).
2442 fn predicates_from_bound<'tcx>(
2443     astconv: &dyn AstConv<'tcx>,
2444     param_ty: Ty<'tcx>,
2445     bound: &'tcx hir::GenericBound<'tcx>,
2446     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2447 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2448     let mut bounds = Bounds::default();
2449     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2450     bounds.predicates(astconv.tcx(), param_ty)
2451 }
2452
2453 fn compute_sig_of_foreign_fn_decl<'tcx>(
2454     tcx: TyCtxt<'tcx>,
2455     def_id: DefId,
2456     decl: &'tcx hir::FnDecl<'tcx>,
2457     abi: abi::Abi,
2458     ident: Ident,
2459 ) -> ty::PolyFnSig<'tcx> {
2460     let unsafety = if abi == abi::Abi::RustIntrinsic {
2461         intrinsic_operation_unsafety(tcx.item_name(def_id))
2462     } else {
2463         hir::Unsafety::Unsafe
2464     };
2465     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2466     let fty = <dyn AstConv<'_>>::ty_of_fn(
2467         &ItemCtxt::new(tcx, def_id),
2468         hir_id,
2469         unsafety,
2470         abi,
2471         decl,
2472         &hir::Generics::empty(),
2473         Some(ident.span),
2474         None,
2475     );
2476
2477     // Feature gate SIMD types in FFI, since I am not sure that the
2478     // ABIs are handled at all correctly. -huonw
2479     if abi != abi::Abi::RustIntrinsic
2480         && abi != abi::Abi::PlatformIntrinsic
2481         && !tcx.features().simd_ffi
2482     {
2483         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2484             if ty.is_simd() {
2485                 let snip = tcx
2486                     .sess
2487                     .source_map()
2488                     .span_to_snippet(ast_ty.span)
2489                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2490                 tcx.sess
2491                     .struct_span_err(
2492                         ast_ty.span,
2493                         &format!(
2494                             "use of SIMD type{} in FFI is highly experimental and \
2495                              may result in invalid code",
2496                             snip
2497                         ),
2498                     )
2499                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2500                     .emit();
2501             }
2502         };
2503         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2504             check(input, ty)
2505         }
2506         if let hir::FnRetTy::Return(ref ty) = decl.output {
2507             check(ty, fty.output().skip_binder())
2508         }
2509     }
2510
2511     fty
2512 }
2513
2514 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2515     match tcx.hir().get_if_local(def_id) {
2516         Some(Node::ForeignItem(..)) => true,
2517         Some(_) => false,
2518         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2519     }
2520 }
2521
2522 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2523     match tcx.hir().get_if_local(def_id) {
2524         Some(
2525             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2526             | Node::ForeignItem(&hir::ForeignItem {
2527                 kind: hir::ForeignItemKind::Static(_, mutbl),
2528                 ..
2529             }),
2530         ) => Some(mutbl),
2531         Some(_) => None,
2532         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2533     }
2534 }
2535
2536 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2537     match tcx.hir().get_if_local(def_id) {
2538         Some(Node::Expr(&rustc_hir::Expr {
2539             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2540             ..
2541         })) => tcx.hir().body(body_id).generator_kind(),
2542         Some(_) => None,
2543         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2544     }
2545 }
2546
2547 fn from_target_feature(
2548     tcx: TyCtxt<'_>,
2549     id: DefId,
2550     attr: &ast::Attribute,
2551     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2552     target_features: &mut Vec<Symbol>,
2553 ) {
2554     let list = match attr.meta_item_list() {
2555         Some(list) => list,
2556         None => return,
2557     };
2558     let bad_item = |span| {
2559         let msg = "malformed `target_feature` attribute input";
2560         let code = "enable = \"..\"".to_owned();
2561         tcx.sess
2562             .struct_span_err(span, msg)
2563             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2564             .emit();
2565     };
2566     let rust_features = tcx.features();
2567     for item in list {
2568         // Only `enable = ...` is accepted in the meta-item list.
2569         if !item.has_name(sym::enable) {
2570             bad_item(item.span());
2571             continue;
2572         }
2573
2574         // Must be of the form `enable = "..."` (a string).
2575         let value = match item.value_str() {
2576             Some(value) => value,
2577             None => {
2578                 bad_item(item.span());
2579                 continue;
2580             }
2581         };
2582
2583         // We allow comma separation to enable multiple features.
2584         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2585             let feature_gate = match supported_target_features.get(feature) {
2586                 Some(g) => g,
2587                 None => {
2588                     let msg =
2589                         format!("the feature named `{}` is not valid for this target", feature);
2590                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2591                     err.span_label(
2592                         item.span(),
2593                         format!("`{}` is not valid for this target", feature),
2594                     );
2595                     if let Some(stripped) = feature.strip_prefix('+') {
2596                         let valid = supported_target_features.contains_key(stripped);
2597                         if valid {
2598                             err.help("consider removing the leading `+` in the feature name");
2599                         }
2600                     }
2601                     err.emit();
2602                     return None;
2603                 }
2604             };
2605
2606             // Only allow features whose feature gates have been enabled.
2607             let allowed = match feature_gate.as_ref().copied() {
2608                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2609                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2610                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2611                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2612                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2613                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2614                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2615                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2616                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2617                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2618                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2619                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2620                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2621                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2622                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2623                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2624                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2625                 Some(name) => bug!("unknown target feature gate {}", name),
2626                 None => true,
2627             };
2628             if !allowed && id.is_local() {
2629                 feature_err(
2630                     &tcx.sess.parse_sess,
2631                     feature_gate.unwrap(),
2632                     item.span(),
2633                     &format!("the target feature `{}` is currently unstable", feature),
2634                 )
2635                 .emit();
2636             }
2637             Some(Symbol::intern(feature))
2638         }));
2639     }
2640 }
2641
2642 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2643     use rustc_middle::mir::mono::Linkage::*;
2644
2645     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2646     // applicable to variable declarations and may not really make sense for
2647     // Rust code in the first place but allow them anyway and trust that the
2648     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2649     // up in the future.
2650     //
2651     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2652     // and don't have to be, LLVM treats them as no-ops.
2653     match name {
2654         "appending" => Appending,
2655         "available_externally" => AvailableExternally,
2656         "common" => Common,
2657         "extern_weak" => ExternalWeak,
2658         "external" => External,
2659         "internal" => Internal,
2660         "linkonce" => LinkOnceAny,
2661         "linkonce_odr" => LinkOnceODR,
2662         "private" => Private,
2663         "weak" => WeakAny,
2664         "weak_odr" => WeakODR,
2665         _ => {
2666             let span = tcx.hir().span_if_local(def_id);
2667             if let Some(span) = span {
2668                 tcx.sess.span_fatal(span, "invalid linkage specified")
2669             } else {
2670                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2671             }
2672         }
2673     }
2674 }
2675
2676 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2677     let attrs = tcx.get_attrs(id);
2678
2679     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2680     if tcx.should_inherit_track_caller(id) {
2681         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2682     }
2683
2684     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2685     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2686         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2687             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2688         }
2689     }
2690
2691     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2692
2693     let mut inline_span = None;
2694     let mut link_ordinal_span = None;
2695     let mut no_sanitize_span = None;
2696     for attr in attrs.iter() {
2697         if attr.has_name(sym::cold) {
2698             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2699         } else if attr.has_name(sym::rustc_allocator) {
2700             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2701         } else if attr.has_name(sym::ffi_returns_twice) {
2702             if tcx.is_foreign_item(id) {
2703                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2704             } else {
2705                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2706                 struct_span_err!(
2707                     tcx.sess,
2708                     attr.span,
2709                     E0724,
2710                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2711                 )
2712                 .emit();
2713             }
2714         } else if attr.has_name(sym::ffi_pure) {
2715             if tcx.is_foreign_item(id) {
2716                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2717                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2718                     struct_span_err!(
2719                         tcx.sess,
2720                         attr.span,
2721                         E0757,
2722                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2723                     )
2724                     .emit();
2725                 } else {
2726                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2727                 }
2728             } else {
2729                 // `#[ffi_pure]` is only allowed on foreign functions
2730                 struct_span_err!(
2731                     tcx.sess,
2732                     attr.span,
2733                     E0755,
2734                     "`#[ffi_pure]` may only be used on foreign functions"
2735                 )
2736                 .emit();
2737             }
2738         } else if attr.has_name(sym::ffi_const) {
2739             if tcx.is_foreign_item(id) {
2740                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2741             } else {
2742                 // `#[ffi_const]` is only allowed on foreign functions
2743                 struct_span_err!(
2744                     tcx.sess,
2745                     attr.span,
2746                     E0756,
2747                     "`#[ffi_const]` may only be used on foreign functions"
2748                 )
2749                 .emit();
2750             }
2751         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2752             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2753         } else if attr.has_name(sym::naked) {
2754             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2755         } else if attr.has_name(sym::no_mangle) {
2756             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2757         } else if attr.has_name(sym::no_coverage) {
2758             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2759         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2760             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2761         } else if attr.has_name(sym::used) {
2762             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2763         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2764             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2765                 struct_span_err!(
2766                     tcx.sess,
2767                     attr.span,
2768                     E0776,
2769                     "`#[cmse_nonsecure_entry]` requires C ABI"
2770                 )
2771                 .emit();
2772             }
2773             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2774                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2775                     .emit();
2776             }
2777             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2778         } else if attr.has_name(sym::thread_local) {
2779             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2780         } else if attr.has_name(sym::track_caller) {
2781             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2782                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2783                     .emit();
2784             }
2785             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2786                 feature_err(
2787                     &tcx.sess.parse_sess,
2788                     sym::closure_track_caller,
2789                     attr.span,
2790                     "`#[track_caller]` on closures is currently unstable",
2791                 )
2792                 .emit();
2793             }
2794             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2795         } else if attr.has_name(sym::export_name) {
2796             if let Some(s) = attr.value_str() {
2797                 if s.as_str().contains('\0') {
2798                     // `#[export_name = ...]` will be converted to a null-terminated string,
2799                     // so it may not contain any null characters.
2800                     struct_span_err!(
2801                         tcx.sess,
2802                         attr.span,
2803                         E0648,
2804                         "`export_name` may not contain null characters"
2805                     )
2806                     .emit();
2807                 }
2808                 codegen_fn_attrs.export_name = Some(s);
2809             }
2810         } else if attr.has_name(sym::target_feature) {
2811             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2812                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2813                     // The `#[target_feature]` attribute is allowed on
2814                     // WebAssembly targets on all functions, including safe
2815                     // ones. Other targets require that `#[target_feature]` is
2816                     // only applied to unsafe funtions (pending the
2817                     // `target_feature_11` feature) because on most targets
2818                     // execution of instructions that are not supported is
2819                     // considered undefined behavior. For WebAssembly which is a
2820                     // 100% safe target at execution time it's not possible to
2821                     // execute undefined instructions, and even if a future
2822                     // feature was added in some form for this it would be a
2823                     // deterministic trap. There is no undefined behavior when
2824                     // executing WebAssembly so `#[target_feature]` is allowed
2825                     // on safe functions (but again, only for WebAssembly)
2826                     //
2827                     // Note that this is also allowed if `actually_rustdoc` so
2828                     // if a target is documenting some wasm-specific code then
2829                     // it's not spuriously denied.
2830                 } else if !tcx.features().target_feature_11 {
2831                     let mut err = feature_err(
2832                         &tcx.sess.parse_sess,
2833                         sym::target_feature_11,
2834                         attr.span,
2835                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2836                     );
2837                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2838                     err.emit();
2839                 } else if let Some(local_id) = id.as_local() {
2840                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2841                 }
2842             }
2843             from_target_feature(
2844                 tcx,
2845                 id,
2846                 attr,
2847                 supported_target_features,
2848                 &mut codegen_fn_attrs.target_features,
2849             );
2850         } else if attr.has_name(sym::linkage) {
2851             if let Some(val) = attr.value_str() {
2852                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2853             }
2854         } else if attr.has_name(sym::link_section) {
2855             if let Some(val) = attr.value_str() {
2856                 if val.as_str().bytes().any(|b| b == 0) {
2857                     let msg = format!(
2858                         "illegal null byte in link_section \
2859                          value: `{}`",
2860                         &val
2861                     );
2862                     tcx.sess.span_err(attr.span, &msg);
2863                 } else {
2864                     codegen_fn_attrs.link_section = Some(val);
2865                 }
2866             }
2867         } else if attr.has_name(sym::link_name) {
2868             codegen_fn_attrs.link_name = attr.value_str();
2869         } else if attr.has_name(sym::link_ordinal) {
2870             link_ordinal_span = Some(attr.span);
2871             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2872                 codegen_fn_attrs.link_ordinal = ordinal;
2873             }
2874         } else if attr.has_name(sym::no_sanitize) {
2875             no_sanitize_span = Some(attr.span);
2876             if let Some(list) = attr.meta_item_list() {
2877                 for item in list.iter() {
2878                     if item.has_name(sym::address) {
2879                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2880                     } else if item.has_name(sym::cfi) {
2881                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2882                     } else if item.has_name(sym::memory) {
2883                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2884                     } else if item.has_name(sym::thread) {
2885                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2886                     } else if item.has_name(sym::hwaddress) {
2887                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2888                     } else {
2889                         tcx.sess
2890                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2891                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2892                             .emit();
2893                     }
2894                 }
2895             }
2896         } else if attr.has_name(sym::instruction_set) {
2897             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2898                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2899                     [NestedMetaItem::MetaItem(set)] => {
2900                         let segments =
2901                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2902                         match segments.as_slice() {
2903                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2904                                 if !tcx.sess.target.has_thumb_interworking {
2905                                     struct_span_err!(
2906                                         tcx.sess.diagnostic(),
2907                                         attr.span,
2908                                         E0779,
2909                                         "target does not support `#[instruction_set]`"
2910                                     )
2911                                     .emit();
2912                                     None
2913                                 } else if segments[1] == sym::a32 {
2914                                     Some(InstructionSetAttr::ArmA32)
2915                                 } else if segments[1] == sym::t32 {
2916                                     Some(InstructionSetAttr::ArmT32)
2917                                 } else {
2918                                     unreachable!()
2919                                 }
2920                             }
2921                             _ => {
2922                                 struct_span_err!(
2923                                     tcx.sess.diagnostic(),
2924                                     attr.span,
2925                                     E0779,
2926                                     "invalid instruction set specified",
2927                                 )
2928                                 .emit();
2929                                 None
2930                             }
2931                         }
2932                     }
2933                     [] => {
2934                         struct_span_err!(
2935                             tcx.sess.diagnostic(),
2936                             attr.span,
2937                             E0778,
2938                             "`#[instruction_set]` requires an argument"
2939                         )
2940                         .emit();
2941                         None
2942                     }
2943                     _ => {
2944                         struct_span_err!(
2945                             tcx.sess.diagnostic(),
2946                             attr.span,
2947                             E0779,
2948                             "cannot specify more than one instruction set"
2949                         )
2950                         .emit();
2951                         None
2952                     }
2953                 },
2954                 _ => {
2955                     struct_span_err!(
2956                         tcx.sess.diagnostic(),
2957                         attr.span,
2958                         E0778,
2959                         "must specify an instruction set"
2960                     )
2961                     .emit();
2962                     None
2963                 }
2964             };
2965         } else if attr.has_name(sym::repr) {
2966             codegen_fn_attrs.alignment = match attr.meta_item_list() {
2967                 Some(items) => match items.as_slice() {
2968                     [item] => match item.name_value_literal() {
2969                         Some((sym::align, literal)) => {
2970                             let alignment = rustc_attr::parse_alignment(&literal.kind);
2971
2972                             match alignment {
2973                                 Ok(align) => Some(align),
2974                                 Err(msg) => {
2975                                     struct_span_err!(
2976                                         tcx.sess.diagnostic(),
2977                                         attr.span,
2978                                         E0589,
2979                                         "invalid `repr(align)` attribute: {}",
2980                                         msg
2981                                     )
2982                                     .emit();
2983
2984                                     None
2985                                 }
2986                             }
2987                         }
2988                         _ => None,
2989                     },
2990                     [] => None,
2991                     _ => None,
2992                 },
2993                 None => None,
2994             };
2995         }
2996     }
2997
2998     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2999         if !attr.has_name(sym::inline) {
3000             return ia;
3001         }
3002         match attr.meta_kind() {
3003             Some(MetaItemKind::Word) => InlineAttr::Hint,
3004             Some(MetaItemKind::List(ref items)) => {
3005                 inline_span = Some(attr.span);
3006                 if items.len() != 1 {
3007                     struct_span_err!(
3008                         tcx.sess.diagnostic(),
3009                         attr.span,
3010                         E0534,
3011                         "expected one argument"
3012                     )
3013                     .emit();
3014                     InlineAttr::None
3015                 } else if list_contains_name(&items, sym::always) {
3016                     InlineAttr::Always
3017                 } else if list_contains_name(&items, sym::never) {
3018                     InlineAttr::Never
3019                 } else {
3020                     struct_span_err!(
3021                         tcx.sess.diagnostic(),
3022                         items[0].span(),
3023                         E0535,
3024                         "invalid argument"
3025                     )
3026                     .emit();
3027
3028                     InlineAttr::None
3029                 }
3030             }
3031             Some(MetaItemKind::NameValue(_)) => ia,
3032             None => ia,
3033         }
3034     });
3035
3036     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3037         if !attr.has_name(sym::optimize) {
3038             return ia;
3039         }
3040         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3041         match attr.meta_kind() {
3042             Some(MetaItemKind::Word) => {
3043                 err(attr.span, "expected one argument");
3044                 ia
3045             }
3046             Some(MetaItemKind::List(ref items)) => {
3047                 inline_span = Some(attr.span);
3048                 if items.len() != 1 {
3049                     err(attr.span, "expected one argument");
3050                     OptimizeAttr::None
3051                 } else if list_contains_name(&items, sym::size) {
3052                     OptimizeAttr::Size
3053                 } else if list_contains_name(&items, sym::speed) {
3054                     OptimizeAttr::Speed
3055                 } else {
3056                     err(items[0].span(), "invalid argument");
3057                     OptimizeAttr::None
3058                 }
3059             }
3060             Some(MetaItemKind::NameValue(_)) => ia,
3061             None => ia,
3062         }
3063     });
3064
3065     // #73631: closures inherit `#[target_feature]` annotations
3066     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3067         let owner_id = tcx.parent(id).expect("closure should have a parent");
3068         codegen_fn_attrs
3069             .target_features
3070             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3071     }
3072
3073     // If a function uses #[target_feature] it can't be inlined into general
3074     // purpose functions as they wouldn't have the right target features
3075     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3076     // respected.
3077     if !codegen_fn_attrs.target_features.is_empty() {
3078         if codegen_fn_attrs.inline == InlineAttr::Always {
3079             if let Some(span) = inline_span {
3080                 tcx.sess.span_err(
3081                     span,
3082                     "cannot use `#[inline(always)]` with \
3083                      `#[target_feature]`",
3084                 );
3085             }
3086         }
3087     }
3088
3089     if !codegen_fn_attrs.no_sanitize.is_empty() {
3090         if codegen_fn_attrs.inline == InlineAttr::Always {
3091             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3092                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3093                 tcx.struct_span_lint_hir(
3094                     lint::builtin::INLINE_NO_SANITIZE,
3095                     hir_id,
3096                     no_sanitize_span,
3097                     |lint| {
3098                         lint.build("`no_sanitize` will have no effect after inlining")
3099                             .span_note(inline_span, "inlining requested here")
3100                             .emit();
3101                     },
3102                 )
3103             }
3104         }
3105     }
3106
3107     // Weak lang items have the same semantics as "std internal" symbols in the
3108     // sense that they're preserved through all our LTO passes and only
3109     // strippable by the linker.
3110     //
3111     // Additionally weak lang items have predetermined symbol names.
3112     if tcx.is_weak_lang_item(id) {
3113         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3114     }
3115     let check_name = |attr: &Attribute, sym| attr.has_name(sym);
3116     if let Some(name) = weak_lang_items::link_name(check_name, attrs) {
3117         codegen_fn_attrs.export_name = Some(name);
3118         codegen_fn_attrs.link_name = Some(name);
3119     }
3120     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3121
3122     // Internal symbols to the standard library all have no_mangle semantics in
3123     // that they have defined symbol names present in the function name. This
3124     // also applies to weak symbols where they all have known symbol names.
3125     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3126         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3127     }
3128
3129     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3130     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3131     // intrinsic functions.
3132     if let Some(name) = &codegen_fn_attrs.link_name {
3133         if name.as_str().starts_with("llvm.") {
3134             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3135         }
3136     }
3137
3138     codegen_fn_attrs
3139 }
3140
3141 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3142 /// applied to the method prototype.
3143 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3144     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3145         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3146             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3147                 if let Some(trait_item) = tcx
3148                     .associated_items(trait_def_id)
3149                     .filter_by_name_unhygienic(impl_item.ident.name)
3150                     .find(move |trait_item| {
3151                         trait_item.kind == ty::AssocKind::Fn
3152                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3153                     })
3154                 {
3155                     return tcx
3156                         .codegen_fn_attrs(trait_item.def_id)
3157                         .flags
3158                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3159                 }
3160             }
3161         }
3162     }
3163
3164     false
3165 }
3166
3167 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3168     use rustc_ast::{Lit, LitIntType, LitKind};
3169     let meta_item_list = attr.meta_item_list();
3170     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3171     let sole_meta_list = match meta_item_list {
3172         Some([item]) => item.literal(),
3173         Some(_) => {
3174             tcx.sess
3175                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3176                 .note("the attribute requires exactly one argument")
3177                 .emit();
3178             return None;
3179         }
3180         _ => None,
3181     };
3182     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3183         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3184         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3185         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3186         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3187         //
3188         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3189         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3190         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3191         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3192         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3193         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3194         // about LINK.EXE failing.)
3195         if *ordinal <= u16::MAX as u128 {
3196             Some(*ordinal as u16)
3197         } else {
3198             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3199             tcx.sess
3200                 .struct_span_err(attr.span, &msg)
3201                 .note("the value may not exceed `u16::MAX`")
3202                 .emit();
3203             None
3204         }
3205     } else {
3206         tcx.sess
3207             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3208             .note("an unsuffixed integer value, e.g., `1`, is expected")
3209             .emit();
3210         None
3211     }
3212 }
3213
3214 fn check_link_name_xor_ordinal(
3215     tcx: TyCtxt<'_>,
3216     codegen_fn_attrs: &CodegenFnAttrs,
3217     inline_span: Option<Span>,
3218 ) {
3219     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3220         return;
3221     }
3222     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3223     if let Some(span) = inline_span {
3224         tcx.sess.span_err(span, msg);
3225     } else {
3226         tcx.sess.err(msg);
3227     }
3228 }
3229
3230 /// Checks the function annotated with `#[target_feature]` is not a safe
3231 /// trait method implementation, reporting an error if it is.
3232 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3233     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3234     let node = tcx.hir().get(hir_id);
3235     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3236         let parent_id = tcx.hir().get_parent_did(hir_id);
3237         let parent_item = tcx.hir().expect_item(parent_id);
3238         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3239             tcx.sess
3240                 .struct_span_err(
3241                     attr_span,
3242                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3243                 )
3244                 .span_label(attr_span, "cannot be applied to safe trait method")
3245                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3246                 .emit();
3247         }
3248     }
3249 }