compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind};
  31 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::nested_filter;
  36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  37 use rustc_middle::mir::mono::Linkage;
  38 use rustc_middle::ty::query::Providers;
  39 use rustc_middle::ty::subst::InternalSubsts;
  40 use rustc_middle::ty::util::Discr;
  41 use rustc_middle::ty::util::IntTypeExt;
  42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  43 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50 use std::iter;
  51
  52 mod item_bounds;
  53 mod type_of;
  54
  55 struct OnlySelfBounds(bool);
  56
  57 ///////////////////////////////////////////////////////////////////////////
  58 // Main entry point
  59
  60 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  61     tcx.hir().visit_item_likes_in_module(
  62         module_def_id,
  63         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  64     );
  65 }
  66
  67 pub fn provide(providers: &mut Providers) {
  68     *providers = Providers {
  69         opt_const_param_of: type_of::opt_const_param_of,
  70         type_of: type_of::type_of,
  71         item_bounds: item_bounds::item_bounds,
  72         explicit_item_bounds: item_bounds::explicit_item_bounds,
  73         generics_of,
  74         predicates_of,
  75         predicates_defined_on,
  76         explicit_predicates_of,
  77         super_predicates_of,
  78         super_predicates_that_define_assoc_type,
  79         trait_explicit_predicates_and_bounds,
  80         type_param_predicates,
  81         trait_def,
  82         adt_def,
  83         fn_sig,
  84         impl_trait_ref,
  85         impl_polarity,
  86         is_foreign_item,
  87         static_mutability,
  88         generator_kind,
  89         codegen_fn_attrs,
  90         collect_mod_item_types,
  91         should_inherit_track_caller,
  92         ..*providers
  93     };
  94 }
  95
  96 ///////////////////////////////////////////////////////////////////////////
  97
  98 /// Context specific to some particular item. This is what implements
  99 /// `AstConv`. It has information about the predicates that are defined
 100 /// on the trait. Unfortunately, this predicate information is
 101 /// available in various different forms at various points in the
 102 /// process. So we can't just store a pointer to e.g., the AST or the
 103 /// parsed ty form, we have to be more flexible. To this end, the
 104 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 105 /// `get_type_parameter_bounds` requests, drawing the information from
 106 /// the AST (`hir::Generics`), recursively.
 107 pub struct ItemCtxt<'tcx> {
 108     tcx: TyCtxt<'tcx>,
 109     item_def_id: DefId,
 110 }
 111
 112 ///////////////////////////////////////////////////////////////////////////
 113
 114 #[derive(Default)]
 115 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 116
 117 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 118     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 119         if let hir::TyKind::Infer = t.kind {
 120             self.0.push(t.span);
 121         }
 122         intravisit::walk_ty(self, t)
 123     }
 124     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 125         match generic_arg {
 126             hir::GenericArg::Infer(inf) => {
 127                 self.0.push(inf.span);
 128                 intravisit::walk_inf(self, inf);
 129             }
 130             hir::GenericArg::Type(t) => self.visit_ty(t),
 131             _ => {}
 132         }
 133     }
 134 }
 135
 136 struct CollectItemTypesVisitor<'tcx> {
 137     tcx: TyCtxt<'tcx>,
 138 }
 139
 140 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 141 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 142 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 143 crate fn placeholder_type_error<'tcx>(
 144     tcx: TyCtxt<'tcx>,
 145     span: Option<Span>,
 146     generics: &[hir::GenericParam<'_>],
 147     placeholder_types: Vec<Span>,
 148     suggest: bool,
 149     hir_ty: Option<&hir::Ty<'_>>,
 150     kind: &'static str,
 151 ) {
 152     if placeholder_types.is_empty() {
 153         return;
 154     }
 155
 156     let type_name = generics.next_type_param_name(None);
 157     let mut sugg: Vec<_> =
 158         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 159
 160     if generics.is_empty() {
 161         if let Some(span) = span {
 162             sugg.push((span, format!("<{}>", type_name)));
 163         }
 164     } else if let Some(arg) = generics
 165         .iter()
 166         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 167     {
 168         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 169         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 170         sugg.push((arg.span, (*type_name).to_string()));
 171     } else {
 172         let last = generics.iter().last().unwrap();
 173         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 174         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 175         sugg.push((span, format!(", {}", type_name)));
 176     }
 177
 178     let mut err = bad_placeholder(tcx, "type", placeholder_types, kind);
 179
 180     // Suggest, but only if it is not a function in const or static
 181     if suggest {
 182         let mut is_fn = false;
 183         let mut is_const_or_static = false;
 184
 185         if let Some(hir_ty) = hir_ty {
 186             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 187                 is_fn = true;
 188
 189                 // Check if parent is const or static
 190                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 191                 let parent_node = tcx.hir().get(parent_id);
 192
 193                 is_const_or_static = matches!(
 194                     parent_node,
 195                     Node::Item(&hir::Item {
 196                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 197                         ..
 198                     }) | Node::TraitItem(&hir::TraitItem {
 199                         kind: hir::TraitItemKind::Const(..),
 200                         ..
 201                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 202                 );
 203             }
 204         }
 205
 206         // if function is wrapped around a const or static,
 207         // then don't show the suggestion
 208         if !(is_fn && is_const_or_static) {
 209             err.multipart_suggestion(
 210                 "use type parameters instead",
 211                 sugg,
 212                 Applicability::HasPlaceholders,
 213             );
 214         }
 215     }
 216     err.emit();
 217 }
 218
 219 fn reject_placeholder_type_signatures_in_item<'tcx>(
 220     tcx: TyCtxt<'tcx>,
 221     item: &'tcx hir::Item<'tcx>,
 222 ) {
 223     let (generics, suggest) = match &item.kind {
 224         hir::ItemKind::Union(_, generics)
 225         | hir::ItemKind::Enum(_, generics)
 226         | hir::ItemKind::TraitAlias(generics, _)
 227         | hir::ItemKind::Trait(_, _, generics, ..)
 228         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 229         | hir::ItemKind::Struct(_, generics) => (generics, true),
 230         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 231         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 232         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 233         _ => return,
 234     };
 235
 236     let mut visitor = PlaceholderHirTyCollector::default();
 237     visitor.visit_item(item);
 238
 239     placeholder_type_error(
 240         tcx,
 241         Some(generics.span),
 242         generics.params,
 243         visitor.0,
 244         suggest,
 245         None,
 246         item.kind.descr(),
 247     );
 248 }
 249
 250 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 251     type NestedFilter = nested_filter::OnlyBodies;
 252
 253     fn nested_visit_map(&mut self) -> Self::Map {
 254         self.tcx.hir()
 255     }
 256
 257     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 258         convert_item(self.tcx, item.item_id());
 259         reject_placeholder_type_signatures_in_item(self.tcx, item);
 260         intravisit::walk_item(self, item);
 261     }
 262
 263     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 264         for param in generics.params {
 265             match param.kind {
 266                 hir::GenericParamKind::Lifetime { .. } => {}
 267                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 268                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 269                     self.tcx.ensure().type_of(def_id);
 270                 }
 271                 hir::GenericParamKind::Type { .. } => {}
 272                 hir::GenericParamKind::Const { default, .. } => {
 273                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 274                     self.tcx.ensure().type_of(def_id);
 275                     if let Some(default) = default {
 276                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 277                         // need to store default and type of default
 278                         self.tcx.ensure().type_of(default_def_id);
 279                         self.tcx.ensure().const_param_default(def_id);
 280                     }
 281                 }
 282             }
 283         }
 284         intravisit::walk_generics(self, generics);
 285     }
 286
 287     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 288         if let hir::ExprKind::Closure(..) = expr.kind {
 289             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 290             self.tcx.ensure().generics_of(def_id);
 291             // We do not call `type_of` for closures here as that
 292             // depends on typecheck and would therefore hide
 293             // any further errors in case one typeck fails.
 294         }
 295         intravisit::walk_expr(self, expr);
 296     }
 297
 298     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 299         convert_trait_item(self.tcx, trait_item.trait_item_id());
 300         intravisit::walk_trait_item(self, trait_item);
 301     }
 302
 303     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 304         convert_impl_item(self.tcx, impl_item.impl_item_id());
 305         intravisit::walk_impl_item(self, impl_item);
 306     }
 307 }
 308
 309 ///////////////////////////////////////////////////////////////////////////
 310 // Utility types and common code for the above passes.
 311
 312 fn bad_placeholder<'tcx>(
 313     tcx: TyCtxt<'tcx>,
 314     placeholder_kind: &'static str,
 315     mut spans: Vec<Span>,
 316     kind: &'static str,
 317 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 318     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 319
 320     spans.sort();
 321     let mut err = struct_span_err!(
 322         tcx.sess,
 323         spans.clone(),
 324         E0121,
 325         "the {} placeholder `_` is not allowed within types on item signatures for {}",
 326         placeholder_kind,
 327         kind
 328     );
 329     for span in spans {
 330         err.span_label(span, "not allowed in type signatures");
 331     }
 332     err
 333 }
 334
 335 impl<'tcx> ItemCtxt<'tcx> {
 336     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 337         ItemCtxt { tcx, item_def_id }
 338     }
 339
 340     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 341         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 342     }
 343
 344     pub fn hir_id(&self) -> hir::HirId {
 345         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 346     }
 347
 348     pub fn node(&self) -> hir::Node<'tcx> {
 349         self.tcx.hir().get(self.hir_id())
 350     }
 351 }
 352
 353 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 354     fn tcx(&self) -> TyCtxt<'tcx> {
 355         self.tcx
 356     }
 357
 358     fn item_def_id(&self) -> Option<DefId> {
 359         Some(self.item_def_id)
 360     }
 361
 362     fn get_type_parameter_bounds(
 363         &self,
 364         span: Span,
 365         def_id: DefId,
 366         assoc_name: Ident,
 367     ) -> ty::GenericPredicates<'tcx> {
 368         self.tcx.at(span).type_param_predicates((
 369             self.item_def_id,
 370             def_id.expect_local(),
 371             assoc_name,
 372         ))
 373     }
 374
 375     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 376         None
 377     }
 378
 379     fn allow_ty_infer(&self) -> bool {
 380         false
 381     }
 382
 383     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 384         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 385     }
 386
 387     fn ct_infer(
 388         &self,
 389         ty: Ty<'tcx>,
 390         _: Option<&ty::GenericParamDef>,
 391         span: Span,
 392     ) -> &'tcx Const<'tcx> {
 393         bad_placeholder(self.tcx(), "const", vec![span], "generic").emit();
 394         // Typeck doesn't expect erased regions to be returned from `type_of`.
 395         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 396             ty::ReErased => self.tcx.lifetimes.re_static,
 397             _ => r,
 398         });
 399         self.tcx().const_error(ty)
 400     }
 401
 402     fn projected_ty_from_poly_trait_ref(
 403         &self,
 404         span: Span,
 405         item_def_id: DefId,
 406         item_segment: &hir::PathSegment<'_>,
 407         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 408     ) -> Ty<'tcx> {
 409         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 410             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 411                 self,
 412                 self.tcx,
 413                 span,
 414                 item_def_id,
 415                 item_segment,
 416                 trait_ref.substs,
 417             );
 418             self.tcx().mk_projection(item_def_id, item_substs)
 419         } else {
 420             // There are no late-bound regions; we can just ignore the binder.
 421             let mut err = struct_span_err!(
 422                 self.tcx().sess,
 423                 span,
 424                 E0212,
 425                 "cannot use the associated type of a trait \
 426                  with uninferred generic parameters"
 427             );
 428
 429             match self.node() {
 430                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 431                     let item =
 432                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 433                     match &item.kind {
 434                         hir::ItemKind::Enum(_, generics)
 435                         | hir::ItemKind::Struct(_, generics)
 436                         | hir::ItemKind::Union(_, generics) => {
 437                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 438                             let (lt_sp, sugg) = match generics.params {
 439                                 [] => (generics.span, format!("<{}>", lt_name)),
 440                                 [bound, ..] => {
 441                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 442                                 }
 443                             };
 444                             let suggestions = vec![
 445                                 (lt_sp, sugg),
 446                                 (
 447                                     span.with_hi(item_segment.ident.span.lo()),
 448                                     format!(
 449                                         "{}::",
 450                                         // Replace the existing lifetimes with a new named lifetime.
 451                                         self.tcx
 452                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 453                                                 self.tcx.mk_region(ty::ReEarlyBound(
 454                                                     ty::EarlyBoundRegion {
 455                                                         def_id: item_def_id,
 456                                                         index: 0,
 457                                                         name: Symbol::intern(&lt_name),
 458                                                     },
 459                                                 ))
 460                                             })
 461                                             .0,
 462                                     ),
 463                                 ),
 464                             ];
 465                             err.multipart_suggestion(
 466                                 "use a fully qualified path with explicit lifetimes",
 467                                 suggestions,
 468                                 Applicability::MaybeIncorrect,
 469                             );
 470                         }
 471                         _ => {}
 472                     }
 473                 }
 474                 hir::Node::Item(hir::Item {
 475                     kind:
 476                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 477                     ..
 478                 }) => {}
 479                 hir::Node::Item(_)
 480                 | hir::Node::ForeignItem(_)
 481                 | hir::Node::TraitItem(_)
 482                 | hir::Node::ImplItem(_) => {
 483                     err.span_suggestion_verbose(
 484                         span.with_hi(item_segment.ident.span.lo()),
 485                         "use a fully qualified path with inferred lifetimes",
 486                         format!(
 487                             "{}::",
 488                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 489                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 490                         ),
 491                         Applicability::MaybeIncorrect,
 492                     );
 493                 }
 494                 _ => {}
 495             }
 496             err.emit();
 497             self.tcx().ty_error()
 498         }
 499     }
 500
 501     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 502         // Types in item signatures are not normalized to avoid undue dependencies.
 503         ty
 504     }
 505
 506     fn set_tainted_by_errors(&self) {
 507         // There's no obvious place to track this, so just let it go.
 508     }
 509
 510     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 511         // There's no place to record types from signatures?
 512     }
 513 }
 514
 515 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 516 fn get_new_lifetime_name<'tcx>(
 517     tcx: TyCtxt<'tcx>,
 518     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 519     generics: &hir::Generics<'tcx>,
 520 ) -> String {
 521     let existing_lifetimes = tcx
 522         .collect_referenced_late_bound_regions(&poly_trait_ref)
 523         .into_iter()
 524         .filter_map(|lt| {
 525             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 526                 Some(name.as_str().to_string())
 527             } else {
 528                 None
 529             }
 530         })
 531         .chain(generics.params.iter().filter_map(|param| {
 532             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 533                 Some(param.name.ident().as_str().to_string())
 534             } else {
 535                 None
 536             }
 537         }))
 538         .collect::<FxHashSet<String>>();
 539
 540     let a_to_z_repeat_n = |n| {
 541         (b'a'..=b'z').map(move |c| {
 542             let mut s = '\''.to_string();
 543             s.extend(std::iter::repeat(char::from(c)).take(n));
 544             s
 545         })
 546     };
 547
 548     // If all single char lifetime names are present, we wrap around and double the chars.
 549     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 550 }
 551
 552 /// Returns the predicates defined on `item_def_id` of the form
 553 /// `X: Foo` where `X` is the type parameter `def_id`.
 554 fn type_param_predicates(
 555     tcx: TyCtxt<'_>,
 556     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 557 ) -> ty::GenericPredicates<'_> {
 558     use rustc_hir::*;
 559
 560     // In the AST, bounds can derive from two places. Either
 561     // written inline like `<T: Foo>` or in a where-clause like
 562     // `where T: Foo`.
 563
 564     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 565     let param_owner = tcx.hir().ty_param_owner(param_id);
 566     let generics = tcx.generics_of(param_owner);
 567     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 568     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 569
 570     // Don't look for bounds where the type parameter isn't in scope.
 571     let parent = if item_def_id == param_owner.to_def_id() {
 572         None
 573     } else {
 574         tcx.generics_of(item_def_id).parent
 575     };
 576
 577     let mut result = parent
 578         .map(|parent| {
 579             let icx = ItemCtxt::new(tcx, parent);
 580             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 581         })
 582         .unwrap_or_default();
 583     let mut extend = None;
 584
 585     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 586     let ast_generics = match tcx.hir().get(item_hir_id) {
 587         Node::TraitItem(item) => &item.generics,
 588
 589         Node::ImplItem(item) => &item.generics,
 590
 591         Node::Item(item) => {
 592             match item.kind {
 593                 ItemKind::Fn(.., ref generics, _)
 594                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 595                 | ItemKind::TyAlias(_, ref generics)
 596                 | ItemKind::OpaqueTy(OpaqueTy {
 597                     ref generics,
 598                     origin: hir::OpaqueTyOrigin::TyAlias,
 599                     ..
 600                 })
 601                 | ItemKind::Enum(_, ref generics)
 602                 | ItemKind::Struct(_, ref generics)
 603                 | ItemKind::Union(_, ref generics) => generics,
 604                 ItemKind::Trait(_, _, ref generics, ..) => {
 605                     // Implied `Self: Trait` and supertrait bounds.
 606                     if param_id == item_hir_id {
 607                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 608                         extend =
 609                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 610                     }
 611                     generics
 612                 }
 613                 _ => return result,
 614             }
 615         }
 616
 617         Node::ForeignItem(item) => match item.kind {
 618             ForeignItemKind::Fn(_, _, ref generics) => generics,
 619             _ => return result,
 620         },
 621
 622         _ => return result,
 623     };
 624
 625     let icx = ItemCtxt::new(tcx, item_def_id);
 626     let extra_predicates = extend.into_iter().chain(
 627         icx.type_parameter_bounds_in_generics(
 628             ast_generics,
 629             param_id,
 630             ty,
 631             OnlySelfBounds(true),
 632             Some(assoc_name),
 633         )
 634         .into_iter()
 635         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 636             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 637             _ => false,
 638         }),
 639     );
 640     result.predicates =
 641         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 642     result
 643 }
 644
 645 impl<'tcx> ItemCtxt<'tcx> {
 646     /// Finds bounds from `hir::Generics`. This requires scanning through the
 647     /// AST. We do this to avoid having to convert *all* the bounds, which
 648     /// would create artificial cycles. Instead, we can only convert the
 649     /// bounds for a type parameter `X` if `X::Foo` is used.
 650     fn type_parameter_bounds_in_generics(
 651         &self,
 652         ast_generics: &'tcx hir::Generics<'tcx>,
 653         param_id: hir::HirId,
 654         ty: Ty<'tcx>,
 655         only_self_bounds: OnlySelfBounds,
 656         assoc_name: Option<Ident>,
 657     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 658         let from_ty_params = ast_generics
 659             .params
 660             .iter()
 661             .filter_map(|param| match param.kind {
 662                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 663                     if param.hir_id == param_id =>
 664                 {
 665                     Some(&param.bounds)
 666                 }
 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(), name: f.ident.name, 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.name,
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, items) = match item.kind {
1198         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1199             (is_auto == hir::IsAuto::Yes, unsafety, items)
1200         }
1201         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1202         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1203     };
1204
1205     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1206     if paren_sugar && !tcx.features().unboxed_closures {
1207         tcx.sess
1208             .struct_span_err(
1209                 item.span,
1210                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1211                  which traits can use parenthetical notation",
1212             )
1213             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1214             .emit();
1215     }
1216
1217     let is_marker = tcx.has_attr(def_id, sym::marker);
1218     let skip_array_during_method_dispatch =
1219         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1220     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1221         ty::trait_def::TraitSpecializationKind::Marker
1222     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1223         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1224     } else {
1225         ty::trait_def::TraitSpecializationKind::None
1226     };
1227     let def_path_hash = tcx.def_path_hash(def_id);
1228
1229     let must_implement_one_of = tcx
1230         .get_attrs(def_id)
1231         .iter()
1232         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1233         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1234         // and that they are all identifiers
1235         .and_then(|attr| match attr.meta_item_list() {
1236             Some(items) if items.len() < 2 => {
1237                 tcx.sess
1238                     .struct_span_err(
1239                         attr.span,
1240                         "the `#[rustc_must_implement_one_of]` attribute must be \
1241                         used with at least 2 args",
1242                     )
1243                     .emit();
1244
1245                 None
1246             }
1247             Some(items) => items
1248                 .into_iter()
1249                 .map(|item| item.ident().ok_or(item.span()))
1250                 .collect::<Result<Box<[_]>, _>>()
1251                 .map_err(|span| {
1252                     tcx.sess
1253                         .struct_span_err(span, "must be a name of an associated function")
1254                         .emit();
1255                 })
1256                 .ok()
1257                 .zip(Some(attr.span)),
1258             // Error is reported by `rustc_attr!`
1259             None => None,
1260         })
1261         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1262         // functions in the trait with default implementations
1263         .and_then(|(list, attr_span)| {
1264             let errors = list.iter().filter_map(|ident| {
1265                 let item = items.iter().find(|item| item.ident == *ident);
1266
1267                 match item {
1268                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1269                         if !item.defaultness.has_value() {
1270                             tcx.sess
1271                                 .struct_span_err(
1272                                     item.span,
1273                                     "This function doesn't have a default implementation",
1274                                 )
1275                                 .span_note(attr_span, "required by this annotation")
1276                                 .emit();
1277
1278                             return Some(());
1279                         }
1280
1281                         return None;
1282                     }
1283                     Some(item) => tcx
1284                         .sess
1285                         .struct_span_err(item.span, "Not a function")
1286                         .span_note(attr_span, "required by this annotation")
1287                         .note(
1288                             "All `#[rustc_must_implement_one_of]` arguments \
1289                             must be associated function names",
1290                         )
1291                         .emit(),
1292                     None => tcx
1293                         .sess
1294                         .struct_span_err(ident.span, "Function not found in this trait")
1295                         .emit(),
1296                 }
1297
1298                 Some(())
1299             });
1300
1301             (errors.count() == 0).then_some(list)
1302         })
1303         // Check for duplicates
1304         .and_then(|list| {
1305             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1306             let mut no_dups = true;
1307
1308             for ident in &*list {
1309                 if let Some(dup) = set.insert(ident.name, ident.span) {
1310                     tcx.sess
1311                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1312                         .note(
1313                             "All `#[rustc_must_implement_one_of]` arguments \
1314                             must be unique",
1315                         )
1316                         .emit();
1317
1318                     no_dups = false;
1319                 }
1320             }
1321
1322             no_dups.then_some(list)
1323         });
1324
1325     ty::TraitDef::new(
1326         def_id,
1327         unsafety,
1328         paren_sugar,
1329         is_auto,
1330         is_marker,
1331         skip_array_during_method_dispatch,
1332         spec_kind,
1333         def_path_hash,
1334         must_implement_one_of,
1335     )
1336 }
1337
1338 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1339     struct LateBoundRegionsDetector<'tcx> {
1340         tcx: TyCtxt<'tcx>,
1341         outer_index: ty::DebruijnIndex,
1342         has_late_bound_regions: Option<Span>,
1343     }
1344
1345     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1346         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1347             if self.has_late_bound_regions.is_some() {
1348                 return;
1349             }
1350             match ty.kind {
1351                 hir::TyKind::BareFn(..) => {
1352                     self.outer_index.shift_in(1);
1353                     intravisit::walk_ty(self, ty);
1354                     self.outer_index.shift_out(1);
1355                 }
1356                 _ => intravisit::walk_ty(self, ty),
1357             }
1358         }
1359
1360         fn visit_poly_trait_ref(
1361             &mut self,
1362             tr: &'tcx hir::PolyTraitRef<'tcx>,
1363             m: hir::TraitBoundModifier,
1364         ) {
1365             if self.has_late_bound_regions.is_some() {
1366                 return;
1367             }
1368             self.outer_index.shift_in(1);
1369             intravisit::walk_poly_trait_ref(self, tr, m);
1370             self.outer_index.shift_out(1);
1371         }
1372
1373         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1374             if self.has_late_bound_regions.is_some() {
1375                 return;
1376             }
1377
1378             match self.tcx.named_region(lt.hir_id) {
1379                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1380                 Some(
1381                     rl::Region::LateBound(debruijn, _, _, _)
1382                     | rl::Region::LateBoundAnon(debruijn, _, _),
1383                 ) if debruijn < self.outer_index => {}
1384                 Some(
1385                     rl::Region::LateBound(..)
1386                     | rl::Region::LateBoundAnon(..)
1387                     | rl::Region::Free(..),
1388                 )
1389                 | None => {
1390                     self.has_late_bound_regions = Some(lt.span);
1391                 }
1392             }
1393         }
1394     }
1395
1396     fn has_late_bound_regions<'tcx>(
1397         tcx: TyCtxt<'tcx>,
1398         generics: &'tcx hir::Generics<'tcx>,
1399         decl: &'tcx hir::FnDecl<'tcx>,
1400     ) -> Option<Span> {
1401         let mut visitor = LateBoundRegionsDetector {
1402             tcx,
1403             outer_index: ty::INNERMOST,
1404             has_late_bound_regions: None,
1405         };
1406         for param in generics.params {
1407             if let GenericParamKind::Lifetime { .. } = param.kind {
1408                 if tcx.is_late_bound(param.hir_id) {
1409                     return Some(param.span);
1410                 }
1411             }
1412         }
1413         visitor.visit_fn_decl(decl);
1414         visitor.has_late_bound_regions
1415     }
1416
1417     match node {
1418         Node::TraitItem(item) => match item.kind {
1419             hir::TraitItemKind::Fn(ref sig, _) => {
1420                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1421             }
1422             _ => None,
1423         },
1424         Node::ImplItem(item) => match item.kind {
1425             hir::ImplItemKind::Fn(ref sig, _) => {
1426                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1427             }
1428             _ => None,
1429         },
1430         Node::ForeignItem(item) => match item.kind {
1431             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1432                 has_late_bound_regions(tcx, generics, fn_decl)
1433             }
1434             _ => None,
1435         },
1436         Node::Item(item) => match item.kind {
1437             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1438                 has_late_bound_regions(tcx, generics, sig.decl)
1439             }
1440             _ => None,
1441         },
1442         _ => None,
1443     }
1444 }
1445
1446 struct AnonConstInParamTyDetector {
1447     in_param_ty: bool,
1448     found_anon_const_in_param_ty: bool,
1449     ct: HirId,
1450 }
1451
1452 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1453     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1454         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1455             let prev = self.in_param_ty;
1456             self.in_param_ty = true;
1457             self.visit_ty(ty);
1458             self.in_param_ty = prev;
1459         }
1460     }
1461
1462     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1463         if self.in_param_ty && self.ct == c.hir_id {
1464             self.found_anon_const_in_param_ty = true;
1465         } else {
1466             intravisit::walk_anon_const(self, c)
1467         }
1468     }
1469 }
1470
1471 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1472     use rustc_hir::*;
1473
1474     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1475
1476     let node = tcx.hir().get(hir_id);
1477     let parent_def_id = match node {
1478         Node::ImplItem(_)
1479         | Node::TraitItem(_)
1480         | Node::Variant(_)
1481         | Node::Ctor(..)
1482         | Node::Field(_) => {
1483             let parent_id = tcx.hir().get_parent_item(hir_id);
1484             Some(parent_id.to_def_id())
1485         }
1486         // FIXME(#43408) always enable this once `lazy_normalization` is
1487         // stable enough and does not need a feature gate anymore.
1488         Node::AnonConst(_) => {
1489             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1490
1491             let mut in_param_ty = false;
1492             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1493                 if let Some(generics) = node.generics() {
1494                     let mut visitor = AnonConstInParamTyDetector {
1495                         in_param_ty: false,
1496                         found_anon_const_in_param_ty: false,
1497                         ct: hir_id,
1498                     };
1499
1500                     visitor.visit_generics(generics);
1501                     in_param_ty = visitor.found_anon_const_in_param_ty;
1502                     break;
1503                 }
1504             }
1505
1506             if in_param_ty {
1507                 // We do not allow generic parameters in anon consts if we are inside
1508                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1509                 None
1510             } else if tcx.lazy_normalization() {
1511                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1512                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1513                     //
1514                     // struct Foo<const N: usize = { .. }>;
1515                     //        ^^^       ^          ^^^^^^ def id of this anon const
1516                     //        ^         ^ param_id
1517                     //        ^ parent_def_id
1518                     //
1519                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1520                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1521                     //
1522                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1523                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1524                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1525                     //
1526                     // We fix this by having this function return the parent's generics ourselves and truncating the
1527                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1528                     //
1529                     // For the above code example that means we want `substs: []`
1530                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1531                     // the def id of the `{ N + 1 }` anon const
1532                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1533                     //
1534                     // This has some implications for how we get the predicates available to the anon const
1535                     // see `explicit_predicates_of` for more information on this
1536                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1537                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1538                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1539                     // In the above example this would be .params[..N#0]
1540                     let params = generics.params[..param_def_idx as usize].to_owned();
1541                     let param_def_id_to_index =
1542                         params.iter().map(|param| (param.def_id, param.index)).collect();
1543
1544                     return ty::Generics {
1545                         // we set the parent of these generics to be our parent's parent so that we
1546                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1547                         // struct Foo<const N: usize, const M: usize = { ... }>;
1548                         parent: generics.parent,
1549                         parent_count: generics.parent_count,
1550                         params,
1551                         param_def_id_to_index,
1552                         has_self: generics.has_self,
1553                         has_late_bound_regions: generics.has_late_bound_regions,
1554                     };
1555                 }
1556
1557                 // HACK(eddyb) this provides the correct generics when
1558                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1559                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1560                 //
1561                 // Note that we do not supply the parent generics when using
1562                 // `min_const_generics`.
1563                 Some(parent_def_id.to_def_id())
1564             } else {
1565                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1566                 match parent_node {
1567                     // HACK(eddyb) this provides the correct generics for repeat
1568                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1569                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1570                     // as they shouldn't be able to cause query cycle errors.
1571                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1572                         if constant.hir_id() == hir_id =>
1573                     {
1574                         Some(parent_def_id.to_def_id())
1575                     }
1576                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1577                         if constant.hir_id == hir_id =>
1578                     {
1579                         Some(parent_def_id.to_def_id())
1580                     }
1581                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1582                         Some(tcx.typeck_root_def_id(def_id))
1583                     }
1584                     _ => None,
1585                 }
1586             }
1587         }
1588         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1589             Some(tcx.typeck_root_def_id(def_id))
1590         }
1591         Node::Item(item) => match item.kind {
1592             ItemKind::OpaqueTy(hir::OpaqueTy {
1593                 origin:
1594                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1595                 ..
1596             }) => Some(fn_def_id.to_def_id()),
1597             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1598                 let parent_id = tcx.hir().get_parent_item(hir_id);
1599                 assert_ne!(parent_id, CRATE_DEF_ID);
1600                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1601                 // Opaque types are always nested within another item, and
1602                 // inherit the generics of the item.
1603                 Some(parent_id.to_def_id())
1604             }
1605             _ => None,
1606         },
1607         _ => None,
1608     };
1609
1610     let mut opt_self = None;
1611     let mut allow_defaults = false;
1612
1613     let no_generics = hir::Generics::empty();
1614     let ast_generics = match node {
1615         Node::TraitItem(item) => &item.generics,
1616
1617         Node::ImplItem(item) => &item.generics,
1618
1619         Node::Item(item) => {
1620             match item.kind {
1621                 ItemKind::Fn(.., ref generics, _)
1622                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1623
1624                 ItemKind::TyAlias(_, ref generics)
1625                 | ItemKind::Enum(_, ref generics)
1626                 | ItemKind::Struct(_, ref generics)
1627                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1628                 | ItemKind::Union(_, ref generics) => {
1629                     allow_defaults = true;
1630                     generics
1631                 }
1632
1633                 ItemKind::Trait(_, _, ref generics, ..)
1634                 | ItemKind::TraitAlias(ref generics, ..) => {
1635                     // Add in the self type parameter.
1636                     //
1637                     // Something of a hack: use the node id for the trait, also as
1638                     // the node id for the Self type parameter.
1639                     let param_id = item.def_id;
1640
1641                     opt_self = Some(ty::GenericParamDef {
1642                         index: 0,
1643                         name: kw::SelfUpper,
1644                         def_id: param_id.to_def_id(),
1645                         pure_wrt_drop: false,
1646                         kind: ty::GenericParamDefKind::Type {
1647                             has_default: false,
1648                             object_lifetime_default: rl::Set1::Empty,
1649                             synthetic: false,
1650                         },
1651                     });
1652
1653                     allow_defaults = true;
1654                     generics
1655                 }
1656
1657                 _ => &no_generics,
1658             }
1659         }
1660
1661         Node::ForeignItem(item) => match item.kind {
1662             ForeignItemKind::Static(..) => &no_generics,
1663             ForeignItemKind::Fn(_, _, ref generics) => generics,
1664             ForeignItemKind::Type => &no_generics,
1665         },
1666
1667         _ => &no_generics,
1668     };
1669
1670     let has_self = opt_self.is_some();
1671     let mut parent_has_self = false;
1672     let mut own_start = has_self as u32;
1673     let parent_count = parent_def_id.map_or(0, |def_id| {
1674         let generics = tcx.generics_of(def_id);
1675         assert!(!has_self);
1676         parent_has_self = generics.has_self;
1677         own_start = generics.count() as u32;
1678         generics.parent_count + generics.params.len()
1679     });
1680
1681     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1682
1683     if let Some(opt_self) = opt_self {
1684         params.push(opt_self);
1685     }
1686
1687     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1688     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1689         name: param.name.ident().name,
1690         index: own_start + i as u32,
1691         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1692         pure_wrt_drop: param.pure_wrt_drop,
1693         kind: ty::GenericParamDefKind::Lifetime,
1694     }));
1695
1696     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1697
1698     // Now create the real type and const parameters.
1699     let type_start = own_start - has_self as u32 + params.len() as u32;
1700     let mut i = 0;
1701
1702     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1703         GenericParamKind::Lifetime { .. } => None,
1704         GenericParamKind::Type { ref default, synthetic, .. } => {
1705             if !allow_defaults && default.is_some() {
1706                 if !tcx.features().default_type_parameter_fallback {
1707                     tcx.struct_span_lint_hir(
1708                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1709                         param.hir_id,
1710                         param.span,
1711                         |lint| {
1712                             lint.build(
1713                                 "defaults for type parameters are only allowed in \
1714                                  `struct`, `enum`, `type`, or `trait` definitions",
1715                             )
1716                             .emit();
1717                         },
1718                     );
1719                 }
1720             }
1721
1722             let kind = ty::GenericParamDefKind::Type {
1723                 has_default: default.is_some(),
1724                 object_lifetime_default: object_lifetime_defaults
1725                     .as_ref()
1726                     .map_or(rl::Set1::Empty, |o| o[i]),
1727                 synthetic,
1728             };
1729
1730             let param_def = ty::GenericParamDef {
1731                 index: type_start + i as u32,
1732                 name: param.name.ident().name,
1733                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1734                 pure_wrt_drop: param.pure_wrt_drop,
1735                 kind,
1736             };
1737             i += 1;
1738             Some(param_def)
1739         }
1740         GenericParamKind::Const { default, .. } => {
1741             if !allow_defaults && default.is_some() {
1742                 tcx.sess.span_err(
1743                     param.span,
1744                     "defaults for const parameters are only allowed in \
1745                     `struct`, `enum`, `type`, or `trait` definitions",
1746                 );
1747             }
1748
1749             let param_def = ty::GenericParamDef {
1750                 index: type_start + i as u32,
1751                 name: param.name.ident().name,
1752                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1753                 pure_wrt_drop: param.pure_wrt_drop,
1754                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1755             };
1756             i += 1;
1757             Some(param_def)
1758         }
1759     }));
1760
1761     // provide junk type parameter defs - the only place that
1762     // cares about anything but the length is instantiation,
1763     // and we don't do that for closures.
1764     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1765         let dummy_args = if gen.is_some() {
1766             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1767         } else {
1768             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1769         };
1770
1771         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1772             index: type_start + i as u32,
1773             name: Symbol::intern(arg),
1774             def_id,
1775             pure_wrt_drop: false,
1776             kind: ty::GenericParamDefKind::Type {
1777                 has_default: false,
1778                 object_lifetime_default: rl::Set1::Empty,
1779                 synthetic: false,
1780             },
1781         }));
1782     }
1783
1784     // provide junk type parameter defs for const blocks.
1785     if let Node::AnonConst(_) = node {
1786         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1787         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1788             params.push(ty::GenericParamDef {
1789                 index: type_start,
1790                 name: Symbol::intern("<const_ty>"),
1791                 def_id,
1792                 pure_wrt_drop: false,
1793                 kind: ty::GenericParamDefKind::Type {
1794                     has_default: false,
1795                     object_lifetime_default: rl::Set1::Empty,
1796                     synthetic: false,
1797                 },
1798             });
1799         }
1800     }
1801
1802     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1803
1804     ty::Generics {
1805         parent: parent_def_id,
1806         parent_count,
1807         params,
1808         param_def_id_to_index,
1809         has_self: has_self || parent_has_self,
1810         has_late_bound_regions: has_late_bound_regions(tcx, node),
1811     }
1812 }
1813
1814 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1815     generic_args.iter().any(|arg| match arg {
1816         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1817         hir::GenericArg::Infer(_) => true,
1818         _ => false,
1819     })
1820 }
1821
1822 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1823 /// use inference to provide suggestions for the appropriate type if possible.
1824 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1825     use hir::TyKind::*;
1826     match &ty.kind {
1827         Infer => true,
1828         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1829         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1830         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1831         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1832         Path(hir::QPath::TypeRelative(ty, segment)) => {
1833             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1834         }
1835         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1836             ty_opt.map_or(false, is_suggestable_infer_ty)
1837                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1838         }
1839         _ => false,
1840     }
1841 }
1842
1843 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1844     if let hir::FnRetTy::Return(ty) = output {
1845         if is_suggestable_infer_ty(ty) {
1846             return Some(&*ty);
1847         }
1848     }
1849     None
1850 }
1851
1852 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1853     use rustc_hir::Node::*;
1854     use rustc_hir::*;
1855
1856     let def_id = def_id.expect_local();
1857     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1858
1859     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1860
1861     match tcx.hir().get(hir_id) {
1862         TraitItem(hir::TraitItem {
1863             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1864             ident,
1865             generics,
1866             ..
1867         })
1868         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1869         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1870             match get_infer_ret_ty(&sig.decl.output) {
1871                 Some(ty) => {
1872                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1873                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1874                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1875                         ty::ReErased => tcx.lifetimes.re_static,
1876                         _ => r,
1877                     });
1878                     let fn_sig = ty::Binder::dummy(fn_sig);
1879
1880                     let mut visitor = PlaceholderHirTyCollector::default();
1881                     visitor.visit_ty(ty);
1882                     let mut diag = bad_placeholder(tcx, "type", visitor.0, "return type");
1883                     let ret_ty = fn_sig.skip_binder().output();
1884                     if !ret_ty.references_error() {
1885                         if !ret_ty.is_closure() {
1886                             let ret_ty_str = match ret_ty.kind() {
1887                                 // Suggest a function pointer return type instead of a unique function definition
1888                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1889                                 // syntax)
1890                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1891                                 _ => ret_ty.to_string(),
1892                             };
1893                             diag.span_suggestion(
1894                                 ty.span,
1895                                 "replace with the correct return type",
1896                                 ret_ty_str,
1897                                 Applicability::MaybeIncorrect,
1898                             );
1899                         } else {
1900                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1901                             // to prevent the user from getting a papercut while trying to use the unique closure
1902                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1903                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1904                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1905                         }
1906                     }
1907                     diag.emit();
1908
1909                     fn_sig
1910                 }
1911                 None => <dyn AstConv<'_>>::ty_of_fn(
1912                     &icx,
1913                     hir_id,
1914                     sig.header.unsafety,
1915                     sig.header.abi,
1916                     sig.decl,
1917                     generics,
1918                     Some(ident.span),
1919                     None,
1920                 ),
1921             }
1922         }
1923
1924         TraitItem(hir::TraitItem {
1925             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1926             ident,
1927             generics,
1928             ..
1929         }) => <dyn AstConv<'_>>::ty_of_fn(
1930             &icx,
1931             hir_id,
1932             header.unsafety,
1933             header.abi,
1934             decl,
1935             generics,
1936             Some(ident.span),
1937             None,
1938         ),
1939
1940         ForeignItem(&hir::ForeignItem {
1941             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1942         }) => {
1943             let abi = tcx.hir().get_foreign_abi(hir_id);
1944             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1945         }
1946
1947         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1948             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1949             let inputs =
1950                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1951             ty::Binder::dummy(tcx.mk_fn_sig(
1952                 inputs,
1953                 ty,
1954                 false,
1955                 hir::Unsafety::Normal,
1956                 abi::Abi::Rust,
1957             ))
1958         }
1959
1960         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1961             // Closure signatures are not like other function
1962             // signatures and cannot be accessed through `fn_sig`. For
1963             // example, a closure signature excludes the `self`
1964             // argument. In any case they are embedded within the
1965             // closure type as part of the `ClosureSubsts`.
1966             //
1967             // To get the signature of a closure, you should use the
1968             // `sig` method on the `ClosureSubsts`:
1969             //
1970             //    substs.as_closure().sig(def_id, tcx)
1971             bug!(
1972                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1973             );
1974         }
1975
1976         x => {
1977             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1978         }
1979     }
1980 }
1981
1982 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1983     let icx = ItemCtxt::new(tcx, def_id);
1984     match tcx.hir().expect_item(def_id.expect_local()).kind {
1985         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1986             let selfty = tcx.type_of(def_id);
1987             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1988         }),
1989         _ => bug!(),
1990     }
1991 }
1992
1993 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1994     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1995     let item = tcx.hir().expect_item(def_id.expect_local());
1996     match &item.kind {
1997         hir::ItemKind::Impl(hir::Impl {
1998             polarity: hir::ImplPolarity::Negative(span),
1999             of_trait,
2000             ..
2001         }) => {
2002             if is_rustc_reservation {
2003                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2004                 tcx.sess.span_err(span, "reservation impls can't be negative");
2005             }
2006             ty::ImplPolarity::Negative
2007         }
2008         hir::ItemKind::Impl(hir::Impl {
2009             polarity: hir::ImplPolarity::Positive,
2010             of_trait: None,
2011             ..
2012         }) => {
2013             if is_rustc_reservation {
2014                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2015             }
2016             ty::ImplPolarity::Positive
2017         }
2018         hir::ItemKind::Impl(hir::Impl {
2019             polarity: hir::ImplPolarity::Positive,
2020             of_trait: Some(_),
2021             ..
2022         }) => {
2023             if is_rustc_reservation {
2024                 ty::ImplPolarity::Reservation
2025             } else {
2026                 ty::ImplPolarity::Positive
2027             }
2028         }
2029         item => bug!("impl_polarity: {:?} not an impl", item),
2030     }
2031 }
2032
2033 /// Returns the early-bound lifetimes declared in this generics
2034 /// listing. For anything other than fns/methods, this is just all
2035 /// the lifetimes that are declared. For fns or methods, we have to
2036 /// screen out those that do not appear in any where-clauses etc using
2037 /// `resolve_lifetime::early_bound_lifetimes`.
2038 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2039     tcx: TyCtxt<'tcx>,
2040     generics: &'a hir::Generics<'a>,
2041 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2042     generics.params.iter().filter(move |param| match param.kind {
2043         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2044         _ => false,
2045     })
2046 }
2047
2048 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2049 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2050 /// inferred constraints concerning which regions outlive other regions.
2051 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2052     debug!("predicates_defined_on({:?})", def_id);
2053     let mut result = tcx.explicit_predicates_of(def_id);
2054     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2055     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2056     if !inferred_outlives.is_empty() {
2057         debug!(
2058             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2059             def_id, inferred_outlives,
2060         );
2061         if result.predicates.is_empty() {
2062             result.predicates = inferred_outlives;
2063         } else {
2064             result.predicates = tcx
2065                 .arena
2066                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2067         }
2068     }
2069
2070     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2071     result
2072 }
2073
2074 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2075 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2076 /// `Self: Trait` predicates for traits.
2077 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2078     let mut result = tcx.predicates_defined_on(def_id);
2079
2080     if tcx.is_trait(def_id) {
2081         // For traits, add `Self: Trait` predicate. This is
2082         // not part of the predicates that a user writes, but it
2083         // is something that one must prove in order to invoke a
2084         // method or project an associated type.
2085         //
2086         // In the chalk setup, this predicate is not part of the
2087         // "predicates" for a trait item. But it is useful in
2088         // rustc because if you directly (e.g.) invoke a trait
2089         // method like `Trait::method(...)`, you must naturally
2090         // prove that the trait applies to the types that were
2091         // used, and adding the predicate into this list ensures
2092         // that this is done.
2093         //
2094         // We use a DUMMY_SP here as a way to signal trait bounds that come
2095         // from the trait itself that *shouldn't* be shown as the source of
2096         // an obligation and instead be skipped. Otherwise we'd use
2097         // `tcx.def_span(def_id);`
2098         let span = rustc_span::DUMMY_SP;
2099         result.predicates =
2100             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2101                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2102                 span,
2103             ))));
2104     }
2105     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2106     result
2107 }
2108
2109 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2110 /// N.B., this does not include any implied/inferred constraints.
2111 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2112     use rustc_hir::*;
2113
2114     debug!("explicit_predicates_of(def_id={:?})", def_id);
2115
2116     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2117     let node = tcx.hir().get(hir_id);
2118
2119     let mut is_trait = None;
2120     let mut is_default_impl_trait = None;
2121
2122     let icx = ItemCtxt::new(tcx, def_id);
2123
2124     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2125
2126     // We use an `IndexSet` to preserves order of insertion.
2127     // Preserving the order of insertion is important here so as not to break UI tests.
2128     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2129
2130     let ast_generics = match node {
2131         Node::TraitItem(item) => &item.generics,
2132
2133         Node::ImplItem(item) => &item.generics,
2134
2135         Node::Item(item) => {
2136             match item.kind {
2137                 ItemKind::Impl(ref impl_) => {
2138                     if impl_.defaultness.is_default() {
2139                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2140                     }
2141                     &impl_.generics
2142                 }
2143                 ItemKind::Fn(.., ref generics, _)
2144                 | ItemKind::TyAlias(_, ref generics)
2145                 | ItemKind::Enum(_, ref generics)
2146                 | ItemKind::Struct(_, ref generics)
2147                 | ItemKind::Union(_, ref generics) => generics,
2148
2149                 ItemKind::Trait(_, _, ref generics, ..) => {
2150                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2151                     generics
2152                 }
2153                 ItemKind::TraitAlias(ref generics, _) => {
2154                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2155                     generics
2156                 }
2157                 ItemKind::OpaqueTy(OpaqueTy {
2158                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2159                     ..
2160                 }) => {
2161                     // return-position impl trait
2162                     //
2163                     // We don't inherit predicates from the parent here:
2164                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2165                     // then the return type is `f::<'static, T>::{{opaque}}`.
2166                     //
2167                     // If we inherited the predicates of `f` then we would
2168                     // require that `T: 'static` to show that the return
2169                     // type is well-formed.
2170                     //
2171                     // The only way to have something with this opaque type
2172                     // is from the return type of the containing function,
2173                     // which will ensure that the function's predicates
2174                     // hold.
2175                     return ty::GenericPredicates { parent: None, predicates: &[] };
2176                 }
2177                 ItemKind::OpaqueTy(OpaqueTy {
2178                     ref generics,
2179                     origin: hir::OpaqueTyOrigin::TyAlias,
2180                     ..
2181                 }) => {
2182                     // type-alias impl trait
2183                     generics
2184                 }
2185
2186                 _ => NO_GENERICS,
2187             }
2188         }
2189
2190         Node::ForeignItem(item) => match item.kind {
2191             ForeignItemKind::Static(..) => NO_GENERICS,
2192             ForeignItemKind::Fn(_, _, ref generics) => generics,
2193             ForeignItemKind::Type => NO_GENERICS,
2194         },
2195
2196         _ => NO_GENERICS,
2197     };
2198
2199     let generics = tcx.generics_of(def_id);
2200     let parent_count = generics.parent_count as u32;
2201     let has_own_self = generics.has_self && parent_count == 0;
2202
2203     // Below we'll consider the bounds on the type parameters (including `Self`)
2204     // and the explicit where-clauses, but to get the full set of predicates
2205     // on a trait we need to add in the supertrait bounds and bounds found on
2206     // associated types.
2207     if let Some(_trait_ref) = is_trait {
2208         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2209     }
2210
2211     // In default impls, we can assume that the self type implements
2212     // the trait. So in:
2213     //
2214     //     default impl Foo for Bar { .. }
2215     //
2216     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2217     // (see below). Recall that a default impl is not itself an impl, but rather a
2218     // set of defaults that can be incorporated into another impl.
2219     if let Some(trait_ref) = is_default_impl_trait {
2220         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2221     }
2222
2223     // Collect the region predicates that were declared inline as
2224     // well. In the case of parameters declared on a fn or method, we
2225     // have to be careful to only iterate over early-bound regions.
2226     let mut index = parent_count + has_own_self as u32;
2227     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2228         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2229             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2230             index,
2231             name: param.name.ident().name,
2232         }));
2233         index += 1;
2234
2235         match param.kind {
2236             GenericParamKind::Lifetime { .. } => {
2237                 param.bounds.iter().for_each(|bound| match bound {
2238                     hir::GenericBound::Outlives(lt) => {
2239                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2240                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2241                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2242                     }
2243                     _ => bug!(),
2244                 });
2245             }
2246             _ => bug!(),
2247         }
2248     }
2249
2250     // Collect the predicates that were written inline by the user on each
2251     // type parameter (e.g., `<T: Foo>`).
2252     for param in ast_generics.params {
2253         match param.kind {
2254             // We already dealt with early bound lifetimes above.
2255             GenericParamKind::Lifetime { .. } => (),
2256             GenericParamKind::Type { .. } => {
2257                 let name = param.name.ident().name;
2258                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2259                 index += 1;
2260
2261                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2262                 // Params are implicitly sized unless a `?Sized` bound is found
2263                 <dyn AstConv<'_>>::add_implicitly_sized(
2264                     &icx,
2265                     &mut bounds,
2266                     param.bounds,
2267                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2268                     param.span,
2269                 );
2270                 predicates.extend(bounds.predicates(tcx, param_ty));
2271             }
2272             GenericParamKind::Const { .. } => {
2273                 // Bounds on const parameters are currently not possible.
2274                 debug_assert!(param.bounds.is_empty());
2275                 index += 1;
2276             }
2277         }
2278     }
2279
2280     // Add in the bounds that appear in the where-clause.
2281     let where_clause = &ast_generics.where_clause;
2282     for predicate in where_clause.predicates {
2283         match predicate {
2284             hir::WherePredicate::BoundPredicate(bound_pred) => {
2285                 let ty = icx.to_ty(bound_pred.bounded_ty);
2286                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2287
2288                 // Keep the type around in a dummy predicate, in case of no bounds.
2289                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2290                 // is still checked for WF.
2291                 if bound_pred.bounds.is_empty() {
2292                     if let ty::Param(_) = ty.kind() {
2293                         // This is a `where T:`, which can be in the HIR from the
2294                         // transformation that moves `?Sized` to `T`'s declaration.
2295                         // We can skip the predicate because type parameters are
2296                         // trivially WF, but also we *should*, to avoid exposing
2297                         // users who never wrote `where Type:,` themselves, to
2298                         // compiler/tooling bugs from not handling WF predicates.
2299                     } else {
2300                         let span = bound_pred.bounded_ty.span;
2301                         let re_root_empty = tcx.lifetimes.re_root_empty;
2302                         let predicate = ty::Binder::bind_with_vars(
2303                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2304                                 ty,
2305                                 re_root_empty,
2306                             )),
2307                             bound_vars,
2308                         );
2309                         predicates.insert((predicate.to_predicate(tcx), span));
2310                     }
2311                 }
2312
2313                 let mut bounds = Bounds::default();
2314                 <dyn AstConv<'_>>::add_bounds(
2315                     &icx,
2316                     ty,
2317                     bound_pred.bounds.iter(),
2318                     &mut bounds,
2319                     bound_vars,
2320                 );
2321                 predicates.extend(bounds.predicates(tcx, ty));
2322             }
2323
2324             hir::WherePredicate::RegionPredicate(region_pred) => {
2325                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2326                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2327                     let (r2, span) = match bound {
2328                         hir::GenericBound::Outlives(lt) => {
2329                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2330                         }
2331                         _ => bug!(),
2332                     };
2333                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2334                         ty::OutlivesPredicate(r1, r2),
2335                     ))
2336                     .to_predicate(icx.tcx);
2337
2338                     (pred, span)
2339                 }))
2340             }
2341
2342             hir::WherePredicate::EqPredicate(..) => {
2343                 // FIXME(#20041)
2344             }
2345         }
2346     }
2347
2348     if tcx.features().generic_const_exprs {
2349         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2350     }
2351
2352     let mut predicates: Vec<_> = predicates.into_iter().collect();
2353
2354     // Subtle: before we store the predicates into the tcx, we
2355     // sort them so that predicates like `T: Foo<Item=U>` come
2356     // before uses of `U`.  This avoids false ambiguity errors
2357     // in trait checking. See `setup_constraining_predicates`
2358     // for details.
2359     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2360         let self_ty = tcx.type_of(def_id);
2361         let trait_ref = tcx.impl_trait_ref(def_id);
2362         cgp::setup_constraining_predicates(
2363             tcx,
2364             &mut predicates,
2365             trait_ref,
2366             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2367         );
2368     }
2369
2370     let result = ty::GenericPredicates {
2371         parent: generics.parent,
2372         predicates: tcx.arena.alloc_from_iter(predicates),
2373     };
2374     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2375     result
2376 }
2377
2378 fn const_evaluatable_predicates_of<'tcx>(
2379     tcx: TyCtxt<'tcx>,
2380     def_id: LocalDefId,
2381 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2382     struct ConstCollector<'tcx> {
2383         tcx: TyCtxt<'tcx>,
2384         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2385     }
2386
2387     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2388         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2389             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2390             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2391             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2392                 assert_eq!(uv.promoted, None);
2393                 let span = self.tcx.hir().span(c.hir_id);
2394                 self.preds.insert((
2395                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2396                         .to_predicate(self.tcx),
2397                     span,
2398                 ));
2399             }
2400         }
2401
2402         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2403             // Do not look into const param defaults,
2404             // these get checked when they are actually instantiated.
2405             //
2406             // We do not want the following to error:
2407             //
2408             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2409             //     struct Bar<const N: usize>(Foo<N, 3>);
2410         }
2411     }
2412
2413     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2414     let node = tcx.hir().get(hir_id);
2415
2416     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2417     if let hir::Node::Item(item) = node {
2418         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2419             if let Some(of_trait) = &impl_.of_trait {
2420                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2421                 collector.visit_trait_ref(of_trait);
2422             }
2423
2424             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2425             collector.visit_ty(impl_.self_ty);
2426         }
2427     }
2428
2429     if let Some(generics) = node.generics() {
2430         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2431         collector.visit_generics(generics);
2432     }
2433
2434     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2435         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2436         collector.visit_fn_decl(fn_sig.decl);
2437     }
2438     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2439
2440     collector.preds
2441 }
2442
2443 fn trait_explicit_predicates_and_bounds(
2444     tcx: TyCtxt<'_>,
2445     def_id: LocalDefId,
2446 ) -> ty::GenericPredicates<'_> {
2447     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2448     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2449 }
2450
2451 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2452     let def_kind = tcx.def_kind(def_id);
2453     if let DefKind::Trait = def_kind {
2454         // Remove bounds on associated types from the predicates, they will be
2455         // returned by `explicit_item_bounds`.
2456         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2457         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2458
2459         let is_assoc_item_ty = |ty: Ty<'_>| {
2460             // For a predicate from a where clause to become a bound on an
2461             // associated type:
2462             // * It must use the identity substs of the item.
2463             //     * Since any generic parameters on the item are not in scope,
2464             //       this means that the item is not a GAT, and its identity
2465             //       substs are the same as the trait's.
2466             // * It must be an associated type for this trait (*not* a
2467             //   supertrait).
2468             if let ty::Projection(projection) = ty.kind() {
2469                 projection.substs == trait_identity_substs
2470                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2471             } else {
2472                 false
2473             }
2474         };
2475
2476         let predicates: Vec<_> = predicates_and_bounds
2477             .predicates
2478             .iter()
2479             .copied()
2480             .filter(|(pred, _)| match pred.kind().skip_binder() {
2481                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2482                 ty::PredicateKind::Projection(proj) => {
2483                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2484                 }
2485                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2486                 _ => true,
2487             })
2488             .collect();
2489         if predicates.len() == predicates_and_bounds.predicates.len() {
2490             predicates_and_bounds
2491         } else {
2492             ty::GenericPredicates {
2493                 parent: predicates_and_bounds.parent,
2494                 predicates: tcx.arena.alloc_slice(&predicates),
2495             }
2496         }
2497     } else {
2498         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2499             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2500             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2501                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2502                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2503                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2504                 //
2505                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2506                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2507                 //        ^^^                                             explicit_predicates_of on
2508                 //        parent item we dont have set as the
2509                 //        parent of generics returned by `generics_of`
2510                 //
2511                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2512                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2513                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2514                 return tcx.explicit_predicates_of(item_def_id);
2515             }
2516         }
2517         gather_explicit_predicates_of(tcx, def_id)
2518     }
2519 }
2520
2521 /// Converts a specific `GenericBound` from the AST into a set of
2522 /// predicates that apply to the self type. A vector is returned
2523 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2524 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2525 /// and `<T as Bar>::X == i32`).
2526 fn predicates_from_bound<'tcx>(
2527     astconv: &dyn AstConv<'tcx>,
2528     param_ty: Ty<'tcx>,
2529     bound: &'tcx hir::GenericBound<'tcx>,
2530     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2531 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2532     let mut bounds = Bounds::default();
2533     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2534     bounds.predicates(astconv.tcx(), param_ty).collect()
2535 }
2536
2537 fn compute_sig_of_foreign_fn_decl<'tcx>(
2538     tcx: TyCtxt<'tcx>,
2539     def_id: DefId,
2540     decl: &'tcx hir::FnDecl<'tcx>,
2541     abi: abi::Abi,
2542     ident: Ident,
2543 ) -> ty::PolyFnSig<'tcx> {
2544     let unsafety = if abi == abi::Abi::RustIntrinsic {
2545         intrinsic_operation_unsafety(tcx.item_name(def_id))
2546     } else {
2547         hir::Unsafety::Unsafe
2548     };
2549     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2550     let fty = <dyn AstConv<'_>>::ty_of_fn(
2551         &ItemCtxt::new(tcx, def_id),
2552         hir_id,
2553         unsafety,
2554         abi,
2555         decl,
2556         &hir::Generics::empty(),
2557         Some(ident.span),
2558         None,
2559     );
2560
2561     // Feature gate SIMD types in FFI, since I am not sure that the
2562     // ABIs are handled at all correctly. -huonw
2563     if abi != abi::Abi::RustIntrinsic
2564         && abi != abi::Abi::PlatformIntrinsic
2565         && !tcx.features().simd_ffi
2566     {
2567         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2568             if ty.is_simd() {
2569                 let snip = tcx
2570                     .sess
2571                     .source_map()
2572                     .span_to_snippet(ast_ty.span)
2573                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2574                 tcx.sess
2575                     .struct_span_err(
2576                         ast_ty.span,
2577                         &format!(
2578                             "use of SIMD type{} in FFI is highly experimental and \
2579                              may result in invalid code",
2580                             snip
2581                         ),
2582                     )
2583                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2584                     .emit();
2585             }
2586         };
2587         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2588             check(input, ty)
2589         }
2590         if let hir::FnRetTy::Return(ref ty) = decl.output {
2591             check(ty, fty.output().skip_binder())
2592         }
2593     }
2594
2595     fty
2596 }
2597
2598 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2599     match tcx.hir().get_if_local(def_id) {
2600         Some(Node::ForeignItem(..)) => true,
2601         Some(_) => false,
2602         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2603     }
2604 }
2605
2606 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2607     match tcx.hir().get_if_local(def_id) {
2608         Some(
2609             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2610             | Node::ForeignItem(&hir::ForeignItem {
2611                 kind: hir::ForeignItemKind::Static(_, mutbl),
2612                 ..
2613             }),
2614         ) => Some(mutbl),
2615         Some(_) => None,
2616         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2617     }
2618 }
2619
2620 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2621     match tcx.hir().get_if_local(def_id) {
2622         Some(Node::Expr(&rustc_hir::Expr {
2623             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2624             ..
2625         })) => tcx.hir().body(body_id).generator_kind(),
2626         Some(_) => None,
2627         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2628     }
2629 }
2630
2631 fn from_target_feature(
2632     tcx: TyCtxt<'_>,
2633     id: DefId,
2634     attr: &ast::Attribute,
2635     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2636     target_features: &mut Vec<Symbol>,
2637 ) {
2638     let list = match attr.meta_item_list() {
2639         Some(list) => list,
2640         None => return,
2641     };
2642     let bad_item = |span| {
2643         let msg = "malformed `target_feature` attribute input";
2644         let code = "enable = \"..\"".to_owned();
2645         tcx.sess
2646             .struct_span_err(span, msg)
2647             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2648             .emit();
2649     };
2650     let rust_features = tcx.features();
2651     for item in list {
2652         // Only `enable = ...` is accepted in the meta-item list.
2653         if !item.has_name(sym::enable) {
2654             bad_item(item.span());
2655             continue;
2656         }
2657
2658         // Must be of the form `enable = "..."` (a string).
2659         let value = match item.value_str() {
2660             Some(value) => value,
2661             None => {
2662                 bad_item(item.span());
2663                 continue;
2664             }
2665         };
2666
2667         // We allow comma separation to enable multiple features.
2668         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2669             let feature_gate = match supported_target_features.get(feature) {
2670                 Some(g) => g,
2671                 None => {
2672                     let msg =
2673                         format!("the feature named `{}` is not valid for this target", feature);
2674                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2675                     err.span_label(
2676                         item.span(),
2677                         format!("`{}` is not valid for this target", feature),
2678                     );
2679                     if let Some(stripped) = feature.strip_prefix('+') {
2680                         let valid = supported_target_features.contains_key(stripped);
2681                         if valid {
2682                             err.help("consider removing the leading `+` in the feature name");
2683                         }
2684                     }
2685                     err.emit();
2686                     return None;
2687                 }
2688             };
2689
2690             // Only allow features whose feature gates have been enabled.
2691             let allowed = match feature_gate.as_ref().copied() {
2692                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2693                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2694                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2695                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2696                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2697                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2698                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2699                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2700                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2701                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2702                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2703                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2704                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2705                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2706                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2707                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2708                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2709                 Some(name) => bug!("unknown target feature gate {}", name),
2710                 None => true,
2711             };
2712             if !allowed && id.is_local() {
2713                 feature_err(
2714                     &tcx.sess.parse_sess,
2715                     feature_gate.unwrap(),
2716                     item.span(),
2717                     &format!("the target feature `{}` is currently unstable", feature),
2718                 )
2719                 .emit();
2720             }
2721             Some(Symbol::intern(feature))
2722         }));
2723     }
2724 }
2725
2726 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2727     use rustc_middle::mir::mono::Linkage::*;
2728
2729     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2730     // applicable to variable declarations and may not really make sense for
2731     // Rust code in the first place but allow them anyway and trust that the
2732     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2733     // up in the future.
2734     //
2735     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2736     // and don't have to be, LLVM treats them as no-ops.
2737     match name {
2738         "appending" => Appending,
2739         "available_externally" => AvailableExternally,
2740         "common" => Common,
2741         "extern_weak" => ExternalWeak,
2742         "external" => External,
2743         "internal" => Internal,
2744         "linkonce" => LinkOnceAny,
2745         "linkonce_odr" => LinkOnceODR,
2746         "private" => Private,
2747         "weak" => WeakAny,
2748         "weak_odr" => WeakODR,
2749         _ => {
2750             let span = tcx.hir().span_if_local(def_id);
2751             if let Some(span) = span {
2752                 tcx.sess.span_fatal(span, "invalid linkage specified")
2753             } else {
2754                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2755             }
2756         }
2757     }
2758 }
2759
2760 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2761     let attrs = tcx.get_attrs(id);
2762
2763     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2764     if tcx.should_inherit_track_caller(id) {
2765         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2766     }
2767
2768     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2769     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2770         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2771             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2772         }
2773     }
2774
2775     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2776
2777     let mut inline_span = None;
2778     let mut link_ordinal_span = None;
2779     let mut no_sanitize_span = None;
2780     for attr in attrs.iter() {
2781         if attr.has_name(sym::cold) {
2782             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2783         } else if attr.has_name(sym::rustc_allocator) {
2784             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2785         } else if attr.has_name(sym::ffi_returns_twice) {
2786             if tcx.is_foreign_item(id) {
2787                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2788             } else {
2789                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2790                 struct_span_err!(
2791                     tcx.sess,
2792                     attr.span,
2793                     E0724,
2794                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2795                 )
2796                 .emit();
2797             }
2798         } else if attr.has_name(sym::ffi_pure) {
2799             if tcx.is_foreign_item(id) {
2800                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2801                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2802                     struct_span_err!(
2803                         tcx.sess,
2804                         attr.span,
2805                         E0757,
2806                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2807                     )
2808                     .emit();
2809                 } else {
2810                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2811                 }
2812             } else {
2813                 // `#[ffi_pure]` is only allowed on foreign functions
2814                 struct_span_err!(
2815                     tcx.sess,
2816                     attr.span,
2817                     E0755,
2818                     "`#[ffi_pure]` may only be used on foreign functions"
2819                 )
2820                 .emit();
2821             }
2822         } else if attr.has_name(sym::ffi_const) {
2823             if tcx.is_foreign_item(id) {
2824                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2825             } else {
2826                 // `#[ffi_const]` is only allowed on foreign functions
2827                 struct_span_err!(
2828                     tcx.sess,
2829                     attr.span,
2830                     E0756,
2831                     "`#[ffi_const]` may only be used on foreign functions"
2832                 )
2833                 .emit();
2834             }
2835         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2836             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2837         } else if attr.has_name(sym::naked) {
2838             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2839         } else if attr.has_name(sym::no_mangle) {
2840             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2841         } else if attr.has_name(sym::no_coverage) {
2842             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2843         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2844             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2845         } else if attr.has_name(sym::used) {
2846             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2847         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2848             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2849                 struct_span_err!(
2850                     tcx.sess,
2851                     attr.span,
2852                     E0776,
2853                     "`#[cmse_nonsecure_entry]` requires C ABI"
2854                 )
2855                 .emit();
2856             }
2857             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2858                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2859                     .emit();
2860             }
2861             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2862         } else if attr.has_name(sym::thread_local) {
2863             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2864         } else if attr.has_name(sym::track_caller) {
2865             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2866                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2867                     .emit();
2868             }
2869             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2870                 feature_err(
2871                     &tcx.sess.parse_sess,
2872                     sym::closure_track_caller,
2873                     attr.span,
2874                     "`#[track_caller]` on closures is currently unstable",
2875                 )
2876                 .emit();
2877             }
2878             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2879         } else if attr.has_name(sym::export_name) {
2880             if let Some(s) = attr.value_str() {
2881                 if s.as_str().contains('\0') {
2882                     // `#[export_name = ...]` will be converted to a null-terminated string,
2883                     // so it may not contain any null characters.
2884                     struct_span_err!(
2885                         tcx.sess,
2886                         attr.span,
2887                         E0648,
2888                         "`export_name` may not contain null characters"
2889                     )
2890                     .emit();
2891                 }
2892                 codegen_fn_attrs.export_name = Some(s);
2893             }
2894         } else if attr.has_name(sym::target_feature) {
2895             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2896                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2897                     // The `#[target_feature]` attribute is allowed on
2898                     // WebAssembly targets on all functions, including safe
2899                     // ones. Other targets require that `#[target_feature]` is
2900                     // only applied to unsafe funtions (pending the
2901                     // `target_feature_11` feature) because on most targets
2902                     // execution of instructions that are not supported is
2903                     // considered undefined behavior. For WebAssembly which is a
2904                     // 100% safe target at execution time it's not possible to
2905                     // execute undefined instructions, and even if a future
2906                     // feature was added in some form for this it would be a
2907                     // deterministic trap. There is no undefined behavior when
2908                     // executing WebAssembly so `#[target_feature]` is allowed
2909                     // on safe functions (but again, only for WebAssembly)
2910                     //
2911                     // Note that this is also allowed if `actually_rustdoc` so
2912                     // if a target is documenting some wasm-specific code then
2913                     // it's not spuriously denied.
2914                 } else if !tcx.features().target_feature_11 {
2915                     let mut err = feature_err(
2916                         &tcx.sess.parse_sess,
2917                         sym::target_feature_11,
2918                         attr.span,
2919                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2920                     );
2921                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2922                     err.emit();
2923                 } else if let Some(local_id) = id.as_local() {
2924                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2925                 }
2926             }
2927             from_target_feature(
2928                 tcx,
2929                 id,
2930                 attr,
2931                 supported_target_features,
2932                 &mut codegen_fn_attrs.target_features,
2933             );
2934         } else if attr.has_name(sym::linkage) {
2935             if let Some(val) = attr.value_str() {
2936                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2937             }
2938         } else if attr.has_name(sym::link_section) {
2939             if let Some(val) = attr.value_str() {
2940                 if val.as_str().bytes().any(|b| b == 0) {
2941                     let msg = format!(
2942                         "illegal null byte in link_section \
2943                          value: `{}`",
2944                         &val
2945                     );
2946                     tcx.sess.span_err(attr.span, &msg);
2947                 } else {
2948                     codegen_fn_attrs.link_section = Some(val);
2949                 }
2950             }
2951         } else if attr.has_name(sym::link_name) {
2952             codegen_fn_attrs.link_name = attr.value_str();
2953         } else if attr.has_name(sym::link_ordinal) {
2954             link_ordinal_span = Some(attr.span);
2955             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2956                 codegen_fn_attrs.link_ordinal = ordinal;
2957             }
2958         } else if attr.has_name(sym::no_sanitize) {
2959             no_sanitize_span = Some(attr.span);
2960             if let Some(list) = attr.meta_item_list() {
2961                 for item in list.iter() {
2962                     if item.has_name(sym::address) {
2963                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2964                     } else if item.has_name(sym::cfi) {
2965                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2966                     } else if item.has_name(sym::memory) {
2967                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2968                     } else if item.has_name(sym::thread) {
2969                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2970                     } else if item.has_name(sym::hwaddress) {
2971                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2972                     } else {
2973                         tcx.sess
2974                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2975                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2976                             .emit();
2977                     }
2978                 }
2979             }
2980         } else if attr.has_name(sym::instruction_set) {
2981             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2982                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2983                     [NestedMetaItem::MetaItem(set)] => {
2984                         let segments =
2985                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2986                         match segments.as_slice() {
2987                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2988                                 if !tcx.sess.target.has_thumb_interworking {
2989                                     struct_span_err!(
2990                                         tcx.sess.diagnostic(),
2991                                         attr.span,
2992                                         E0779,
2993                                         "target does not support `#[instruction_set]`"
2994                                     )
2995                                     .emit();
2996                                     None
2997                                 } else if segments[1] == sym::a32 {
2998                                     Some(InstructionSetAttr::ArmA32)
2999                                 } else if segments[1] == sym::t32 {
3000                                     Some(InstructionSetAttr::ArmT32)
3001                                 } else {
3002                                     unreachable!()
3003                                 }
3004                             }
3005                             _ => {
3006                                 struct_span_err!(
3007                                     tcx.sess.diagnostic(),
3008                                     attr.span,
3009                                     E0779,
3010                                     "invalid instruction set specified",
3011                                 )
3012                                 .emit();
3013                                 None
3014                             }
3015                         }
3016                     }
3017                     [] => {
3018                         struct_span_err!(
3019                             tcx.sess.diagnostic(),
3020                             attr.span,
3021                             E0778,
3022                             "`#[instruction_set]` requires an argument"
3023                         )
3024                         .emit();
3025                         None
3026                     }
3027                     _ => {
3028                         struct_span_err!(
3029                             tcx.sess.diagnostic(),
3030                             attr.span,
3031                             E0779,
3032                             "cannot specify more than one instruction set"
3033                         )
3034                         .emit();
3035                         None
3036                     }
3037                 },
3038                 _ => {
3039                     struct_span_err!(
3040                         tcx.sess.diagnostic(),
3041                         attr.span,
3042                         E0778,
3043                         "must specify an instruction set"
3044                     )
3045                     .emit();
3046                     None
3047                 }
3048             };
3049         } else if attr.has_name(sym::repr) {
3050             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3051                 Some(items) => match items.as_slice() {
3052                     [item] => match item.name_value_literal() {
3053                         Some((sym::align, literal)) => {
3054                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3055
3056                             match alignment {
3057                                 Ok(align) => Some(align),
3058                                 Err(msg) => {
3059                                     struct_span_err!(
3060                                         tcx.sess.diagnostic(),
3061                                         attr.span,
3062                                         E0589,
3063                                         "invalid `repr(align)` attribute: {}",
3064                                         msg
3065                                     )
3066                                     .emit();
3067
3068                                     None
3069                                 }
3070                             }
3071                         }
3072                         _ => None,
3073                     },
3074                     [] => None,
3075                     _ => None,
3076                 },
3077                 None => None,
3078             };
3079         }
3080     }
3081
3082     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3083         if !attr.has_name(sym::inline) {
3084             return ia;
3085         }
3086         match attr.meta_kind() {
3087             Some(MetaItemKind::Word) => InlineAttr::Hint,
3088             Some(MetaItemKind::List(ref items)) => {
3089                 inline_span = Some(attr.span);
3090                 if items.len() != 1 {
3091                     struct_span_err!(
3092                         tcx.sess.diagnostic(),
3093                         attr.span,
3094                         E0534,
3095                         "expected one argument"
3096                     )
3097                     .emit();
3098                     InlineAttr::None
3099                 } else if list_contains_name(&items, sym::always) {
3100                     InlineAttr::Always
3101                 } else if list_contains_name(&items, sym::never) {
3102                     InlineAttr::Never
3103                 } else {
3104                     struct_span_err!(
3105                         tcx.sess.diagnostic(),
3106                         items[0].span(),
3107                         E0535,
3108                         "invalid argument"
3109                     )
3110                     .emit();
3111
3112                     InlineAttr::None
3113                 }
3114             }
3115             Some(MetaItemKind::NameValue(_)) => ia,
3116             None => ia,
3117         }
3118     });
3119
3120     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3121         if !attr.has_name(sym::optimize) {
3122             return ia;
3123         }
3124         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3125         match attr.meta_kind() {
3126             Some(MetaItemKind::Word) => {
3127                 err(attr.span, "expected one argument");
3128                 ia
3129             }
3130             Some(MetaItemKind::List(ref items)) => {
3131                 inline_span = Some(attr.span);
3132                 if items.len() != 1 {
3133                     err(attr.span, "expected one argument");
3134                     OptimizeAttr::None
3135                 } else if list_contains_name(&items, sym::size) {
3136                     OptimizeAttr::Size
3137                 } else if list_contains_name(&items, sym::speed) {
3138                     OptimizeAttr::Speed
3139                 } else {
3140                     err(items[0].span(), "invalid argument");
3141                     OptimizeAttr::None
3142                 }
3143             }
3144             Some(MetaItemKind::NameValue(_)) => ia,
3145             None => ia,
3146         }
3147     });
3148
3149     // #73631: closures inherit `#[target_feature]` annotations
3150     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3151         let owner_id = tcx.parent(id).expect("closure should have a parent");
3152         codegen_fn_attrs
3153             .target_features
3154             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3155     }
3156
3157     // If a function uses #[target_feature] it can't be inlined into general
3158     // purpose functions as they wouldn't have the right target features
3159     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3160     // respected.
3161     if !codegen_fn_attrs.target_features.is_empty() {
3162         if codegen_fn_attrs.inline == InlineAttr::Always {
3163             if let Some(span) = inline_span {
3164                 tcx.sess.span_err(
3165                     span,
3166                     "cannot use `#[inline(always)]` with \
3167                      `#[target_feature]`",
3168                 );
3169             }
3170         }
3171     }
3172
3173     if !codegen_fn_attrs.no_sanitize.is_empty() {
3174         if codegen_fn_attrs.inline == InlineAttr::Always {
3175             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3176                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3177                 tcx.struct_span_lint_hir(
3178                     lint::builtin::INLINE_NO_SANITIZE,
3179                     hir_id,
3180                     no_sanitize_span,
3181                     |lint| {
3182                         lint.build("`no_sanitize` will have no effect after inlining")
3183                             .span_note(inline_span, "inlining requested here")
3184                             .emit();
3185                     },
3186                 )
3187             }
3188         }
3189     }
3190
3191     // Weak lang items have the same semantics as "std internal" symbols in the
3192     // sense that they're preserved through all our LTO passes and only
3193     // strippable by the linker.
3194     //
3195     // Additionally weak lang items have predetermined symbol names.
3196     if tcx.is_weak_lang_item(id) {
3197         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3198     }
3199     if let Some(name) = weak_lang_items::link_name(attrs) {
3200         codegen_fn_attrs.export_name = Some(name);
3201         codegen_fn_attrs.link_name = Some(name);
3202     }
3203     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3204
3205     // Internal symbols to the standard library all have no_mangle semantics in
3206     // that they have defined symbol names present in the function name. This
3207     // also applies to weak symbols where they all have known symbol names.
3208     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3209         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3210     }
3211
3212     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3213     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3214     // intrinsic functions.
3215     if let Some(name) = &codegen_fn_attrs.link_name {
3216         if name.as_str().starts_with("llvm.") {
3217             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3218         }
3219     }
3220
3221     codegen_fn_attrs
3222 }
3223
3224 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3225 /// applied to the method prototype.
3226 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3227     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3228         if let ty::AssocItemContainer::ImplContainer(_) = impl_item.container {
3229             if let Some(trait_item) = impl_item.trait_item_def_id {
3230                 return tcx
3231                     .codegen_fn_attrs(trait_item)
3232                     .flags
3233                     .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3234             }
3235         }
3236     }
3237
3238     false
3239 }
3240
3241 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3242     use rustc_ast::{Lit, LitIntType, LitKind};
3243     let meta_item_list = attr.meta_item_list();
3244     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3245     let sole_meta_list = match meta_item_list {
3246         Some([item]) => item.literal(),
3247         Some(_) => {
3248             tcx.sess
3249                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3250                 .note("the attribute requires exactly one argument")
3251                 .emit();
3252             return None;
3253         }
3254         _ => None,
3255     };
3256     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3257         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3258         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3259         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3260         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3261         //
3262         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3263         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3264         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3265         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3266         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3267         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3268         // about LINK.EXE failing.)
3269         if *ordinal <= u16::MAX as u128 {
3270             Some(*ordinal as u16)
3271         } else {
3272             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3273             tcx.sess
3274                 .struct_span_err(attr.span, &msg)
3275                 .note("the value may not exceed `u16::MAX`")
3276                 .emit();
3277             None
3278         }
3279     } else {
3280         tcx.sess
3281             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3282             .note("an unsuffixed integer value, e.g., `1`, is expected")
3283             .emit();
3284         None
3285     }
3286 }
3287
3288 fn check_link_name_xor_ordinal(
3289     tcx: TyCtxt<'_>,
3290     codegen_fn_attrs: &CodegenFnAttrs,
3291     inline_span: Option<Span>,
3292 ) {
3293     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3294         return;
3295     }
3296     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3297     if let Some(span) = inline_span {
3298         tcx.sess.span_err(span, msg);
3299     } else {
3300         tcx.sess.err(msg);
3301     }
3302 }
3303
3304 /// Checks the function annotated with `#[target_feature]` is not a safe
3305 /// trait method implementation, reporting an error if it is.
3306 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3307     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3308     let node = tcx.hir().get(hir_id);
3309     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3310         let parent_id = tcx.hir().get_parent_item(hir_id);
3311         let parent_item = tcx.hir().expect_item(parent_id);
3312         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3313             tcx.sess
3314                 .struct_span_err(
3315                     attr_span,
3316                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3317                 )
3318                 .span_label(attr_span, "cannot be applied to safe trait method")
3319                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3320                 .emit();
3321         }
3322     }
3323 }