compiler/rustc_typeck/src/collect.rs

   1 // ignore-tidy-filelength
   2 //! "Collection" is the process of determining the type and other external
   3 //! details of each item in Rust. Collection is specifically concerned
   4 //! with *inter-procedural* things -- for example, for a function
   5 //! definition, collection will figure out the type and signature of the
   6 //! function, but it will not visit the *body* of the function in any way,
   7 //! nor examine type annotations on local variables (that's the job of
   8 //! type *checking*).
   9 //!
  10 //! Collecting is ultimately defined by a bundle of queries that
  11 //! inquire after various facts about the items in the crate (e.g.,
  12 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  13 //! for the full set.
  14 //!
  15 //! At present, however, we do run collection across all items in the
  16 //! crate as a kind of pass. This should eventually be factored away.
  17
  18 use crate::astconv::{AstConv, SizedByDefault};
  19 use crate::bounds::Bounds;
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::errors;
  23 use crate::middle::resolve_lifetime as rl;
  24 use rustc_ast as ast;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind, Res};
  32 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::map::blocks::FnLikeNode;
  37 use rustc_middle::hir::map::Map;
  38 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  39 use rustc_middle::mir::mono::Linkage;
  40 use rustc_middle::ty::query::Providers;
  41 use rustc_middle::ty::subst::InternalSubsts;
  42 use rustc_middle::ty::util::Discr;
  43 use rustc_middle::ty::util::IntTypeExt;
  44 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  45 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
  46 use rustc_session::config::SanitizerSet;
  47 use rustc_session::lint;
  48 use rustc_session::parse::feature_err;
  49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  50 use rustc_span::{Span, DUMMY_SP};
  51 use rustc_target::spec::abi;
  52 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  53
  54 mod item_bounds;
  55 mod type_of;
  56
  57 struct OnlySelfBounds(bool);
  58
  59 ///////////////////////////////////////////////////////////////////////////
  60 // Main entry point
  61
  62 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  63     tcx.hir().visit_item_likes_in_module(
  64         module_def_id,
  65         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  66     );
  67 }
  68
  69 pub fn provide(providers: &mut Providers) {
  70     *providers = Providers {
  71         opt_const_param_of: type_of::opt_const_param_of,
  72         type_of: type_of::type_of,
  73         item_bounds: item_bounds::item_bounds,
  74         explicit_item_bounds: item_bounds::explicit_item_bounds,
  75         generics_of,
  76         predicates_of,
  77         predicates_defined_on,
  78         projection_ty_from_predicates,
  79         explicit_predicates_of,
  80         super_predicates_of,
  81         super_predicates_that_define_assoc_type,
  82         trait_explicit_predicates_and_bounds,
  83         type_param_predicates,
  84         trait_def,
  85         adt_def,
  86         fn_sig,
  87         impl_trait_ref,
  88         impl_polarity,
  89         is_foreign_item,
  90         static_mutability,
  91         generator_kind,
  92         codegen_fn_attrs,
  93         collect_mod_item_types,
  94         ..*providers
  95     };
  96 }
  97
  98 ///////////////////////////////////////////////////////////////////////////
  99
 100 /// Context specific to some particular item. This is what implements
 101 /// `AstConv`. It has information about the predicates that are defined
 102 /// on the trait. Unfortunately, this predicate information is
 103 /// available in various different forms at various points in the
 104 /// process. So we can't just store a pointer to e.g., the AST or the
 105 /// parsed ty form, we have to be more flexible. To this end, the
 106 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 107 /// `get_type_parameter_bounds` requests, drawing the information from
 108 /// the AST (`hir::Generics`), recursively.
 109 pub struct ItemCtxt<'tcx> {
 110     tcx: TyCtxt<'tcx>,
 111     item_def_id: DefId,
 112 }
 113
 114 ///////////////////////////////////////////////////////////////////////////
 115
 116 #[derive(Default)]
 117 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 118
 119 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 120     type Map = intravisit::ErasedMap<'v>;
 121
 122     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 123         NestedVisitorMap::None
 124     }
 125     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 126         if let hir::TyKind::Infer = t.kind {
 127             self.0.push(t.span);
 128         }
 129         intravisit::walk_ty(self, t)
 130     }
 131 }
 132
 133 struct CollectItemTypesVisitor<'tcx> {
 134     tcx: TyCtxt<'tcx>,
 135 }
 136
 137 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 138 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 139 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 140 crate fn placeholder_type_error(
 141     tcx: TyCtxt<'tcx>,
 142     span: Option<Span>,
 143     generics: &[hir::GenericParam<'_>],
 144     placeholder_types: Vec<Span>,
 145     suggest: bool,
 146     hir_ty: Option<&hir::Ty<'_>>,
 147 ) {
 148     if placeholder_types.is_empty() {
 149         return;
 150     }
 151
 152     let type_name = generics.next_type_param_name(None);
 153     let mut sugg: Vec<_> =
 154         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 155
 156     if generics.is_empty() {
 157         if let Some(span) = span {
 158             sugg.push((span, format!("<{}>", type_name)));
 159         }
 160     } else if let Some(arg) = generics
 161         .iter()
 162         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 163     {
 164         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 165         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 166         sugg.push((arg.span, (*type_name).to_string()));
 167     } else {
 168         let last = generics.iter().last().unwrap();
 169         sugg.push((
 170             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 171             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 172             format!(", {}", type_name),
 173         ));
 174     }
 175
 176     let mut err = bad_placeholder_type(tcx, placeholder_types);
 177
 178     // Suggest, but only if it is not a function in const or static
 179     if suggest {
 180         let mut is_fn = false;
 181         let mut is_const = false;
 182         let mut is_static = false;
 183
 184         if let Some(hir_ty) = hir_ty {
 185             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 186                 is_fn = true;
 187
 188                 // Check if parent is const or static
 189                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 190                 let parent_node = tcx.hir().get(parent_id);
 191
 192                 if let hir::Node::Item(item) = parent_node {
 193                     if let hir::ItemKind::Const(_, _) = item.kind {
 194                         is_const = true;
 195                     } else if let hir::ItemKind::Static(_, _, _) = item.kind {
 196                         is_static = true;
 197                     }
 198                 }
 199             }
 200         }
 201
 202         // if function is wrapped around a const or static,
 203         // then don't show the suggestion
 204         if !(is_fn && (is_const || is_static)) {
 205             err.multipart_suggestion(
 206                 "use type parameters instead",
 207                 sugg,
 208                 Applicability::HasPlaceholders,
 209             );
 210         }
 211     }
 212     err.emit();
 213 }
 214
 215 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 216     let (generics, suggest) = match &item.kind {
 217         hir::ItemKind::Union(_, generics)
 218         | hir::ItemKind::Enum(_, generics)
 219         | hir::ItemKind::TraitAlias(generics, _)
 220         | hir::ItemKind::Trait(_, _, generics, ..)
 221         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 222         | hir::ItemKind::Struct(_, generics) => (generics, true),
 223         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 224         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 225         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 226         _ => return,
 227     };
 228
 229     let mut visitor = PlaceholderHirTyCollector::default();
 230     visitor.visit_item(item);
 231
 232     placeholder_type_error(tcx, Some(generics.span), generics.params, visitor.0, suggest, None);
 233 }
 234
 235 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 236     type Map = Map<'tcx>;
 237
 238     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 239         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 240     }
 241
 242     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 243         convert_item(self.tcx, item.item_id());
 244         reject_placeholder_type_signatures_in_item(self.tcx, item);
 245         intravisit::walk_item(self, item);
 246     }
 247
 248     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 249         for param in generics.params {
 250             match param.kind {
 251                 hir::GenericParamKind::Lifetime { .. } => {}
 252                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 253                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 254                     self.tcx.ensure().type_of(def_id);
 255                 }
 256                 hir::GenericParamKind::Type { .. } => {}
 257                 hir::GenericParamKind::Const { default, .. } => {
 258                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 259                     self.tcx.ensure().type_of(def_id);
 260                     if let Some(default) = default {
 261                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 262                         // need to store default and type of default
 263                         self.tcx.ensure().type_of(default_def_id);
 264                         self.tcx.ensure().const_param_default(def_id);
 265                     }
 266                 }
 267             }
 268         }
 269         intravisit::walk_generics(self, generics);
 270     }
 271
 272     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 273         if let hir::ExprKind::Closure(..) = expr.kind {
 274             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 275             self.tcx.ensure().generics_of(def_id);
 276             self.tcx.ensure().type_of(def_id);
 277         }
 278         intravisit::walk_expr(self, expr);
 279     }
 280
 281     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 282         convert_trait_item(self.tcx, trait_item.trait_item_id());
 283         intravisit::walk_trait_item(self, trait_item);
 284     }
 285
 286     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 287         convert_impl_item(self.tcx, impl_item.impl_item_id());
 288         intravisit::walk_impl_item(self, impl_item);
 289     }
 290 }
 291
 292 ///////////////////////////////////////////////////////////////////////////
 293 // Utility types and common code for the above passes.
 294
 295 fn bad_placeholder_type(
 296     tcx: TyCtxt<'tcx>,
 297     mut spans: Vec<Span>,
 298 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 299     spans.sort();
 300     let mut err = struct_span_err!(
 301         tcx.sess,
 302         spans.clone(),
 303         E0121,
 304         "the type placeholder `_` is not allowed within types on item signatures",
 305     );
 306     for span in spans {
 307         err.span_label(span, "not allowed in type signatures");
 308     }
 309     err
 310 }
 311
 312 impl ItemCtxt<'tcx> {
 313     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 314         ItemCtxt { tcx, item_def_id }
 315     }
 316
 317     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 318         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 319     }
 320
 321     pub fn hir_id(&self) -> hir::HirId {
 322         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 323     }
 324
 325     pub fn node(&self) -> hir::Node<'tcx> {
 326         self.tcx.hir().get(self.hir_id())
 327     }
 328 }
 329
 330 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 331     fn tcx(&self) -> TyCtxt<'tcx> {
 332         self.tcx
 333     }
 334
 335     fn item_def_id(&self) -> Option<DefId> {
 336         Some(self.item_def_id)
 337     }
 338
 339     fn default_constness_for_trait_bounds(&self) -> hir::Constness {
 340         if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
 341             fn_like.constness()
 342         } else {
 343             hir::Constness::NotConst
 344         }
 345     }
 346
 347     fn get_type_parameter_bounds(
 348         &self,
 349         span: Span,
 350         def_id: DefId,
 351         assoc_name: Ident,
 352     ) -> ty::GenericPredicates<'tcx> {
 353         self.tcx.at(span).type_param_predicates((
 354             self.item_def_id,
 355             def_id.expect_local(),
 356             assoc_name,
 357         ))
 358     }
 359
 360     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 361         None
 362     }
 363
 364     fn allow_ty_infer(&self) -> bool {
 365         false
 366     }
 367
 368     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 369         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 370     }
 371
 372     fn ct_infer(
 373         &self,
 374         ty: Ty<'tcx>,
 375         _: Option<&ty::GenericParamDef>,
 376         span: Span,
 377     ) -> &'tcx Const<'tcx> {
 378         bad_placeholder_type(self.tcx(), vec![span]).emit();
 379         // Typeck doesn't expect erased regions to be returned from `type_of`.
 380         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 381             ty::ReErased => self.tcx.lifetimes.re_static,
 382             _ => r,
 383         });
 384         self.tcx().const_error(ty)
 385     }
 386
 387     fn projected_ty_from_poly_trait_ref(
 388         &self,
 389         span: Span,
 390         item_def_id: DefId,
 391         item_segment: &hir::PathSegment<'_>,
 392         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 393     ) -> Ty<'tcx> {
 394         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 395             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 396                 self,
 397                 self.tcx,
 398                 span,
 399                 item_def_id,
 400                 item_segment,
 401                 trait_ref.substs,
 402             );
 403             self.tcx().mk_projection(item_def_id, item_substs)
 404         } else {
 405             // There are no late-bound regions; we can just ignore the binder.
 406             let mut err = struct_span_err!(
 407                 self.tcx().sess,
 408                 span,
 409                 E0212,
 410                 "cannot use the associated type of a trait \
 411                  with uninferred generic parameters"
 412             );
 413
 414             match self.node() {
 415                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 416                     let item =
 417                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 418                     match &item.kind {
 419                         hir::ItemKind::Enum(_, generics)
 420                         | hir::ItemKind::Struct(_, generics)
 421                         | hir::ItemKind::Union(_, generics) => {
 422                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 423                             let (lt_sp, sugg) = match generics.params {
 424                                 [] => (generics.span, format!("<{}>", lt_name)),
 425                                 [bound, ..] => {
 426                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 427                                 }
 428                             };
 429                             let suggestions = vec![
 430                                 (lt_sp, sugg),
 431                                 (
 432                                     span,
 433                                     format!(
 434                                         "{}::{}",
 435                                         // Replace the existing lifetimes with a new named lifetime.
 436                                         self.tcx
 437                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 438                                                 self.tcx.mk_region(ty::ReEarlyBound(
 439                                                     ty::EarlyBoundRegion {
 440                                                         def_id: item_def_id,
 441                                                         index: 0,
 442                                                         name: Symbol::intern(&lt_name),
 443                                                     },
 444                                                 ))
 445                                             })
 446                                             .0,
 447                                         item_segment.ident
 448                                     ),
 449                                 ),
 450                             ];
 451                             err.multipart_suggestion(
 452                                 "use a fully qualified path with explicit lifetimes",
 453                                 suggestions,
 454                                 Applicability::MaybeIncorrect,
 455                             );
 456                         }
 457                         _ => {}
 458                     }
 459                 }
 460                 hir::Node::Item(hir::Item {
 461                     kind:
 462                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 463                     ..
 464                 }) => {}
 465                 hir::Node::Item(_)
 466                 | hir::Node::ForeignItem(_)
 467                 | hir::Node::TraitItem(_)
 468                 | hir::Node::ImplItem(_) => {
 469                     err.span_suggestion(
 470                         span,
 471                         "use a fully qualified path with inferred lifetimes",
 472                         format!(
 473                             "{}::{}",
 474                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 475                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 476                             item_segment.ident
 477                         ),
 478                         Applicability::MaybeIncorrect,
 479                     );
 480                 }
 481                 _ => {}
 482             }
 483             err.emit();
 484             self.tcx().ty_error()
 485         }
 486     }
 487
 488     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 489         // Types in item signatures are not normalized to avoid undue dependencies.
 490         ty
 491     }
 492
 493     fn set_tainted_by_errors(&self) {
 494         // There's no obvious place to track this, so just let it go.
 495     }
 496
 497     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 498         // There's no place to record types from signatures?
 499     }
 500 }
 501
 502 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 503 fn get_new_lifetime_name<'tcx>(
 504     tcx: TyCtxt<'tcx>,
 505     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 506     generics: &hir::Generics<'tcx>,
 507 ) -> String {
 508     let existing_lifetimes = tcx
 509         .collect_referenced_late_bound_regions(&poly_trait_ref)
 510         .into_iter()
 511         .filter_map(|lt| {
 512             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 513                 Some(name.as_str().to_string())
 514             } else {
 515                 None
 516             }
 517         })
 518         .chain(generics.params.iter().filter_map(|param| {
 519             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 520                 Some(param.name.ident().as_str().to_string())
 521             } else {
 522                 None
 523             }
 524         }))
 525         .collect::<FxHashSet<String>>();
 526
 527     let a_to_z_repeat_n = |n| {
 528         (b'a'..=b'z').map(move |c| {
 529             let mut s = '\''.to_string();
 530             s.extend(std::iter::repeat(char::from(c)).take(n));
 531             s
 532         })
 533     };
 534
 535     // If all single char lifetime names are present, we wrap around and double the chars.
 536     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 537 }
 538
 539 /// Returns the predicates defined on `item_def_id` of the form
 540 /// `X: Foo` where `X` is the type parameter `def_id`.
 541 fn type_param_predicates(
 542     tcx: TyCtxt<'_>,
 543     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 544 ) -> ty::GenericPredicates<'_> {
 545     use rustc_hir::*;
 546
 547     // In the AST, bounds can derive from two places. Either
 548     // written inline like `<T: Foo>` or in a where-clause like
 549     // `where T: Foo`.
 550
 551     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 552     let param_owner = tcx.hir().ty_param_owner(param_id);
 553     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 554     let generics = tcx.generics_of(param_owner_def_id);
 555     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 556     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 557
 558     // Don't look for bounds where the type parameter isn't in scope.
 559     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 560         None
 561     } else {
 562         tcx.generics_of(item_def_id).parent
 563     };
 564
 565     let mut result = parent
 566         .map(|parent| {
 567             let icx = ItemCtxt::new(tcx, parent);
 568             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 569         })
 570         .unwrap_or_default();
 571     let mut extend = None;
 572
 573     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 574     let ast_generics = match tcx.hir().get(item_hir_id) {
 575         Node::TraitItem(item) => &item.generics,
 576
 577         Node::ImplItem(item) => &item.generics,
 578
 579         Node::Item(item) => {
 580             match item.kind {
 581                 ItemKind::Fn(.., ref generics, _)
 582                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 583                 | ItemKind::TyAlias(_, ref generics)
 584                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 585                 | ItemKind::Enum(_, ref generics)
 586                 | ItemKind::Struct(_, ref generics)
 587                 | ItemKind::Union(_, ref generics) => generics,
 588                 ItemKind::Trait(_, _, ref generics, ..) => {
 589                     // Implied `Self: Trait` and supertrait bounds.
 590                     if param_id == item_hir_id {
 591                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 592                         extend =
 593                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 594                     }
 595                     generics
 596                 }
 597                 _ => return result,
 598             }
 599         }
 600
 601         Node::ForeignItem(item) => match item.kind {
 602             ForeignItemKind::Fn(_, _, ref generics) => generics,
 603             _ => return result,
 604         },
 605
 606         _ => return result,
 607     };
 608
 609     let icx = ItemCtxt::new(tcx, item_def_id);
 610     let extra_predicates = extend.into_iter().chain(
 611         icx.type_parameter_bounds_in_generics(
 612             ast_generics,
 613             param_id,
 614             ty,
 615             OnlySelfBounds(true),
 616             Some(assoc_name),
 617         )
 618         .into_iter()
 619         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 620             ty::PredicateKind::Trait(data, _) => data.self_ty().is_param(index),
 621             _ => false,
 622         }),
 623     );
 624     result.predicates =
 625         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 626     result
 627 }
 628
 629 impl ItemCtxt<'tcx> {
 630     /// Finds bounds from `hir::Generics`. This requires scanning through the
 631     /// AST. We do this to avoid having to convert *all* the bounds, which
 632     /// would create artificial cycles. Instead, we can only convert the
 633     /// bounds for a type parameter `X` if `X::Foo` is used.
 634     fn type_parameter_bounds_in_generics(
 635         &self,
 636         ast_generics: &'tcx hir::Generics<'tcx>,
 637         param_id: hir::HirId,
 638         ty: Ty<'tcx>,
 639         only_self_bounds: OnlySelfBounds,
 640         assoc_name: Option<Ident>,
 641     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 642         let constness = self.default_constness_for_trait_bounds();
 643         let from_ty_params = ast_generics
 644             .params
 645             .iter()
 646             .filter_map(|param| match param.kind {
 647                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 648                 _ => None,
 649             })
 650             .flat_map(|bounds| bounds.iter())
 651             .filter(|b| match assoc_name {
 652                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 653                 None => true,
 654             })
 655             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 656
 657         let from_where_clauses = ast_generics
 658             .where_clause
 659             .predicates
 660             .iter()
 661             .filter_map(|wp| match *wp {
 662                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 663                 _ => None,
 664             })
 665             .flat_map(|bp| {
 666                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 667                     Some(ty)
 668                 } else if !only_self_bounds.0 {
 669                     Some(self.to_ty(&bp.bounded_ty))
 670                 } else {
 671                     None
 672                 };
 673                 bp.bounds
 674                     .iter()
 675                     .filter(|b| match assoc_name {
 676                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 677                         None => true,
 678                     })
 679                     .filter_map(move |b| bt.map(|bt| (bt, b)))
 680             })
 681             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 682
 683         from_ty_params.chain(from_where_clauses).collect()
 684     }
 685
 686     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 687         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 688
 689         match b {
 690             hir::GenericBound::Trait(poly_trait_ref, _) => {
 691                 let trait_ref = &poly_trait_ref.trait_ref;
 692                 if let Some(trait_did) = trait_ref.trait_def_id() {
 693                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 694                 } else {
 695                     false
 696                 }
 697             }
 698             _ => false,
 699         }
 700     }
 701 }
 702
 703 /// Tests whether this is the AST for a reference to the type
 704 /// parameter with ID `param_id`. We use this so as to avoid running
 705 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 706 /// conversion of the type to avoid inducing unnecessary cycles.
 707 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 708     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 709         match path.res {
 710             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 711                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 712             }
 713             _ => false,
 714         }
 715     } else {
 716         false
 717     }
 718 }
 719
 720 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 721     let it = tcx.hir().item(item_id);
 722     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 723     let def_id = item_id.def_id;
 724
 725     match it.kind {
 726         // These don't define types.
 727         hir::ItemKind::ExternCrate(_)
 728         | hir::ItemKind::Use(..)
 729         | hir::ItemKind::Mod(_)
 730         | hir::ItemKind::GlobalAsm(_) => {}
 731         hir::ItemKind::ForeignMod { items, .. } => {
 732             for item in items {
 733                 let item = tcx.hir().foreign_item(item.id);
 734                 tcx.ensure().generics_of(item.def_id);
 735                 tcx.ensure().type_of(item.def_id);
 736                 tcx.ensure().predicates_of(item.def_id);
 737                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 738                     tcx.ensure().fn_sig(item.def_id);
 739                 }
 740             }
 741         }
 742         hir::ItemKind::Enum(ref enum_definition, _) => {
 743             tcx.ensure().generics_of(def_id);
 744             tcx.ensure().type_of(def_id);
 745             tcx.ensure().predicates_of(def_id);
 746             convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
 747         }
 748         hir::ItemKind::Impl { .. } => {
 749             tcx.ensure().generics_of(def_id);
 750             tcx.ensure().type_of(def_id);
 751             tcx.ensure().impl_trait_ref(def_id);
 752             tcx.ensure().predicates_of(def_id);
 753         }
 754         hir::ItemKind::Trait(..) => {
 755             tcx.ensure().generics_of(def_id);
 756             tcx.ensure().trait_def(def_id);
 757             tcx.at(it.span).super_predicates_of(def_id);
 758             tcx.ensure().predicates_of(def_id);
 759         }
 760         hir::ItemKind::TraitAlias(..) => {
 761             tcx.ensure().generics_of(def_id);
 762             tcx.at(it.span).super_predicates_of(def_id);
 763             tcx.ensure().predicates_of(def_id);
 764         }
 765         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 766             tcx.ensure().generics_of(def_id);
 767             tcx.ensure().type_of(def_id);
 768             tcx.ensure().predicates_of(def_id);
 769
 770             for f in struct_def.fields() {
 771                 let def_id = tcx.hir().local_def_id(f.hir_id);
 772                 tcx.ensure().generics_of(def_id);
 773                 tcx.ensure().type_of(def_id);
 774                 tcx.ensure().predicates_of(def_id);
 775             }
 776
 777             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 778                 convert_variant_ctor(tcx, ctor_hir_id);
 779             }
 780         }
 781
 782         // Desugared from `impl Trait`, so visited by the function's return type.
 783         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 784
 785         // Don't call `type_of` on opaque types, since that depends on type
 786         // checking function bodies. `check_item_type` ensures that it's called
 787         // instead.
 788         hir::ItemKind::OpaqueTy(..) => {
 789             tcx.ensure().generics_of(def_id);
 790             tcx.ensure().predicates_of(def_id);
 791             tcx.ensure().explicit_item_bounds(def_id);
 792         }
 793         hir::ItemKind::TyAlias(..)
 794         | hir::ItemKind::Static(..)
 795         | hir::ItemKind::Const(..)
 796         | hir::ItemKind::Fn(..) => {
 797             tcx.ensure().generics_of(def_id);
 798             tcx.ensure().type_of(def_id);
 799             tcx.ensure().predicates_of(def_id);
 800             match it.kind {
 801                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 802                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 803                 _ => (),
 804             }
 805         }
 806     }
 807 }
 808
 809 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 810     let trait_item = tcx.hir().trait_item(trait_item_id);
 811     tcx.ensure().generics_of(trait_item_id.def_id);
 812
 813     match trait_item.kind {
 814         hir::TraitItemKind::Fn(..) => {
 815             tcx.ensure().type_of(trait_item_id.def_id);
 816             tcx.ensure().fn_sig(trait_item_id.def_id);
 817         }
 818
 819         hir::TraitItemKind::Const(.., Some(_)) => {
 820             tcx.ensure().type_of(trait_item_id.def_id);
 821         }
 822
 823         hir::TraitItemKind::Const(..) => {
 824             tcx.ensure().type_of(trait_item_id.def_id);
 825             // Account for `const C: _;`.
 826             let mut visitor = PlaceholderHirTyCollector::default();
 827             visitor.visit_trait_item(trait_item);
 828             placeholder_type_error(tcx, None, &[], visitor.0, false, None);
 829         }
 830
 831         hir::TraitItemKind::Type(_, Some(_)) => {
 832             tcx.ensure().item_bounds(trait_item_id.def_id);
 833             tcx.ensure().type_of(trait_item_id.def_id);
 834             // Account for `type T = _;`.
 835             let mut visitor = PlaceholderHirTyCollector::default();
 836             visitor.visit_trait_item(trait_item);
 837             placeholder_type_error(tcx, None, &[], visitor.0, false, None);
 838         }
 839
 840         hir::TraitItemKind::Type(_, None) => {
 841             tcx.ensure().item_bounds(trait_item_id.def_id);
 842             // #74612: Visit and try to find bad placeholders
 843             // even if there is no concrete type.
 844             let mut visitor = PlaceholderHirTyCollector::default();
 845             visitor.visit_trait_item(trait_item);
 846
 847             placeholder_type_error(tcx, None, &[], visitor.0, false, None);
 848         }
 849     };
 850
 851     tcx.ensure().predicates_of(trait_item_id.def_id);
 852 }
 853
 854 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 855     let def_id = impl_item_id.def_id;
 856     tcx.ensure().generics_of(def_id);
 857     tcx.ensure().type_of(def_id);
 858     tcx.ensure().predicates_of(def_id);
 859     let impl_item = tcx.hir().impl_item(impl_item_id);
 860     match impl_item.kind {
 861         hir::ImplItemKind::Fn(..) => {
 862             tcx.ensure().fn_sig(def_id);
 863         }
 864         hir::ImplItemKind::TyAlias(_) => {
 865             // Account for `type T = _;`
 866             let mut visitor = PlaceholderHirTyCollector::default();
 867             visitor.visit_impl_item(impl_item);
 868
 869             placeholder_type_error(tcx, None, &[], visitor.0, false, None);
 870         }
 871         hir::ImplItemKind::Const(..) => {}
 872     }
 873 }
 874
 875 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 876     let def_id = tcx.hir().local_def_id(ctor_id);
 877     tcx.ensure().generics_of(def_id);
 878     tcx.ensure().type_of(def_id);
 879     tcx.ensure().predicates_of(def_id);
 880 }
 881
 882 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 883     let def = tcx.adt_def(def_id);
 884     let repr_type = def.repr.discr_type();
 885     let initial = repr_type.initial_discriminant(tcx);
 886     let mut prev_discr = None::<Discr<'_>>;
 887
 888     // fill the discriminant values and field types
 889     for variant in variants {
 890         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 891         prev_discr = Some(
 892             if let Some(ref e) = variant.disr_expr {
 893                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 894                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 895             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 896                 Some(discr)
 897             } else {
 898                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 899                     .span_label(
 900                         variant.span,
 901                         format!("overflowed on value after {}", prev_discr.unwrap()),
 902                     )
 903                     .note(&format!(
 904                         "explicitly set `{} = {}` if that is desired outcome",
 905                         variant.ident, wrapped_discr
 906                     ))
 907                     .emit();
 908                 None
 909             }
 910             .unwrap_or(wrapped_discr),
 911         );
 912
 913         for f in variant.data.fields() {
 914             let def_id = tcx.hir().local_def_id(f.hir_id);
 915             tcx.ensure().generics_of(def_id);
 916             tcx.ensure().type_of(def_id);
 917             tcx.ensure().predicates_of(def_id);
 918         }
 919
 920         // Convert the ctor, if any. This also registers the variant as
 921         // an item.
 922         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 923             convert_variant_ctor(tcx, ctor_hir_id);
 924         }
 925     }
 926 }
 927
 928 fn convert_variant(
 929     tcx: TyCtxt<'_>,
 930     variant_did: Option<LocalDefId>,
 931     ctor_did: Option<LocalDefId>,
 932     ident: Ident,
 933     discr: ty::VariantDiscr,
 934     def: &hir::VariantData<'_>,
 935     adt_kind: ty::AdtKind,
 936     parent_did: LocalDefId,
 937 ) -> ty::VariantDef {
 938     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 939     let fields = def
 940         .fields()
 941         .iter()
 942         .map(|f| {
 943             let fid = tcx.hir().local_def_id(f.hir_id);
 944             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 945             if let Some(prev_span) = dup_span {
 946                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 947                     field_name: f.ident,
 948                     span: f.span,
 949                     prev_span,
 950                 });
 951             } else {
 952                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 953             }
 954
 955             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
 956         })
 957         .collect();
 958     let recovered = match def {
 959         hir::VariantData::Struct(_, r) => *r,
 960         _ => false,
 961     };
 962     ty::VariantDef::new(
 963         ident,
 964         variant_did.map(LocalDefId::to_def_id),
 965         ctor_did.map(LocalDefId::to_def_id),
 966         discr,
 967         fields,
 968         CtorKind::from_hir(def),
 969         adt_kind,
 970         parent_did.to_def_id(),
 971         recovered,
 972         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
 973             || variant_did.map_or(false, |variant_did| {
 974                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
 975             }),
 976     )
 977 }
 978
 979 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 980     use rustc_hir::*;
 981
 982     let def_id = def_id.expect_local();
 983     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
 984     let item = match tcx.hir().get(hir_id) {
 985         Node::Item(item) => item,
 986         _ => bug!(),
 987     };
 988
 989     let repr = ReprOptions::new(tcx, def_id.to_def_id());
 990     let (kind, variants) = match item.kind {
 991         ItemKind::Enum(ref def, _) => {
 992             let mut distance_from_explicit = 0;
 993             let variants = def
 994                 .variants
 995                 .iter()
 996                 .map(|v| {
 997                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 998                     let ctor_did =
 999                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1000
1001                     let discr = if let Some(ref e) = v.disr_expr {
1002                         distance_from_explicit = 0;
1003                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1004                     } else {
1005                         ty::VariantDiscr::Relative(distance_from_explicit)
1006                     };
1007                     distance_from_explicit += 1;
1008
1009                     convert_variant(
1010                         tcx,
1011                         variant_did,
1012                         ctor_did,
1013                         v.ident,
1014                         discr,
1015                         &v.data,
1016                         AdtKind::Enum,
1017                         def_id,
1018                     )
1019                 })
1020                 .collect();
1021
1022             (AdtKind::Enum, variants)
1023         }
1024         ItemKind::Struct(ref def, _) => {
1025             let variant_did = None::<LocalDefId>;
1026             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1027
1028             let variants = std::iter::once(convert_variant(
1029                 tcx,
1030                 variant_did,
1031                 ctor_did,
1032                 item.ident,
1033                 ty::VariantDiscr::Relative(0),
1034                 def,
1035                 AdtKind::Struct,
1036                 def_id,
1037             ))
1038             .collect();
1039
1040             (AdtKind::Struct, variants)
1041         }
1042         ItemKind::Union(ref def, _) => {
1043             let variant_did = None;
1044             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1045
1046             let variants = std::iter::once(convert_variant(
1047                 tcx,
1048                 variant_did,
1049                 ctor_did,
1050                 item.ident,
1051                 ty::VariantDiscr::Relative(0),
1052                 def,
1053                 AdtKind::Union,
1054                 def_id,
1055             ))
1056             .collect();
1057
1058             (AdtKind::Union, variants)
1059         }
1060         _ => bug!(),
1061     };
1062     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1063 }
1064
1065 /// Ensures that the super-predicates of the trait with a `DefId`
1066 /// of `trait_def_id` are converted and stored. This also ensures that
1067 /// the transitive super-predicates are converted.
1068 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1069     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1070     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1071 }
1072
1073 /// Ensures that the super-predicates of the trait with a `DefId`
1074 /// of `trait_def_id` are converted and stored. This also ensures that
1075 /// the transitive super-predicates are converted.
1076 fn super_predicates_that_define_assoc_type(
1077     tcx: TyCtxt<'_>,
1078     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1079 ) -> ty::GenericPredicates<'_> {
1080     debug!(
1081         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1082         trait_def_id, assoc_name
1083     );
1084     if trait_def_id.is_local() {
1085         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1086         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1087
1088         let item = match tcx.hir().get(trait_hir_id) {
1089             Node::Item(item) => item,
1090             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1091         };
1092
1093         let (generics, bounds) = match item.kind {
1094             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1095             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1096             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1097         };
1098
1099         let icx = ItemCtxt::new(tcx, trait_def_id);
1100
1101         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1102         let self_param_ty = tcx.types.self_param;
1103         let superbounds1 = if let Some(assoc_name) = assoc_name {
1104             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1105                 &icx,
1106                 self_param_ty,
1107                 &bounds,
1108                 SizedByDefault::No,
1109                 item.span,
1110                 assoc_name,
1111             )
1112         } else {
1113             <dyn AstConv<'_>>::compute_bounds(
1114                 &icx,
1115                 self_param_ty,
1116                 &bounds,
1117                 SizedByDefault::No,
1118                 item.span,
1119             )
1120         };
1121
1122         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1123
1124         // Convert any explicit superbounds in the where-clause,
1125         // e.g., `trait Foo where Self: Bar`.
1126         // In the case of trait aliases, however, we include all bounds in the where-clause,
1127         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1128         // as one of its "superpredicates".
1129         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1130         let superbounds2 = icx.type_parameter_bounds_in_generics(
1131             generics,
1132             item.hir_id(),
1133             self_param_ty,
1134             OnlySelfBounds(!is_trait_alias),
1135             assoc_name,
1136         );
1137
1138         // Combine the two lists to form the complete set of superbounds:
1139         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1140
1141         // Now require that immediate supertraits are converted,
1142         // which will, in turn, reach indirect supertraits.
1143         if assoc_name.is_none() {
1144             // Now require that immediate supertraits are converted,
1145             // which will, in turn, reach indirect supertraits.
1146             for &(pred, span) in superbounds {
1147                 debug!("superbound: {:?}", pred);
1148                 if let ty::PredicateKind::Trait(bound, _) = pred.kind().skip_binder() {
1149                     tcx.at(span).super_predicates_of(bound.def_id());
1150                 }
1151             }
1152         }
1153
1154         ty::GenericPredicates { parent: None, predicates: superbounds }
1155     } else {
1156         // if `assoc_name` is None, then the query should've been redirected to an
1157         // external provider
1158         assert!(assoc_name.is_some());
1159         tcx.super_predicates_of(trait_def_id)
1160     }
1161 }
1162
1163 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1164     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1165     let item = tcx.hir().expect_item(hir_id);
1166
1167     let (is_auto, unsafety) = match item.kind {
1168         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1169         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1170         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1171     };
1172
1173     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1174     if paren_sugar && !tcx.features().unboxed_closures {
1175         tcx.sess
1176             .struct_span_err(
1177                 item.span,
1178                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1179                  which traits can use parenthetical notation",
1180             )
1181             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1182             .emit();
1183     }
1184
1185     let is_marker = tcx.has_attr(def_id, sym::marker);
1186     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1187         ty::trait_def::TraitSpecializationKind::Marker
1188     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1189         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1190     } else {
1191         ty::trait_def::TraitSpecializationKind::None
1192     };
1193     let def_path_hash = tcx.def_path_hash(def_id);
1194     ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, spec_kind, def_path_hash)
1195 }
1196
1197 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1198     struct LateBoundRegionsDetector<'tcx> {
1199         tcx: TyCtxt<'tcx>,
1200         outer_index: ty::DebruijnIndex,
1201         has_late_bound_regions: Option<Span>,
1202     }
1203
1204     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1205         type Map = intravisit::ErasedMap<'tcx>;
1206
1207         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1208             NestedVisitorMap::None
1209         }
1210
1211         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1212             if self.has_late_bound_regions.is_some() {
1213                 return;
1214             }
1215             match ty.kind {
1216                 hir::TyKind::BareFn(..) => {
1217                     self.outer_index.shift_in(1);
1218                     intravisit::walk_ty(self, ty);
1219                     self.outer_index.shift_out(1);
1220                 }
1221                 _ => intravisit::walk_ty(self, ty),
1222             }
1223         }
1224
1225         fn visit_poly_trait_ref(
1226             &mut self,
1227             tr: &'tcx hir::PolyTraitRef<'tcx>,
1228             m: hir::TraitBoundModifier,
1229         ) {
1230             if self.has_late_bound_regions.is_some() {
1231                 return;
1232             }
1233             self.outer_index.shift_in(1);
1234             intravisit::walk_poly_trait_ref(self, tr, m);
1235             self.outer_index.shift_out(1);
1236         }
1237
1238         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1239             if self.has_late_bound_regions.is_some() {
1240                 return;
1241             }
1242
1243             match self.tcx.named_region(lt.hir_id) {
1244                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1245                 Some(
1246                     rl::Region::LateBound(debruijn, _, _) | rl::Region::LateBoundAnon(debruijn, _),
1247                 ) if debruijn < self.outer_index => {}
1248                 Some(
1249                     rl::Region::LateBound(..)
1250                     | rl::Region::LateBoundAnon(..)
1251                     | rl::Region::Free(..),
1252                 )
1253                 | None => {
1254                     self.has_late_bound_regions = Some(lt.span);
1255                 }
1256             }
1257         }
1258     }
1259
1260     fn has_late_bound_regions<'tcx>(
1261         tcx: TyCtxt<'tcx>,
1262         generics: &'tcx hir::Generics<'tcx>,
1263         decl: &'tcx hir::FnDecl<'tcx>,
1264     ) -> Option<Span> {
1265         let mut visitor = LateBoundRegionsDetector {
1266             tcx,
1267             outer_index: ty::INNERMOST,
1268             has_late_bound_regions: None,
1269         };
1270         for param in generics.params {
1271             if let GenericParamKind::Lifetime { .. } = param.kind {
1272                 if tcx.is_late_bound(param.hir_id) {
1273                     return Some(param.span);
1274                 }
1275             }
1276         }
1277         visitor.visit_fn_decl(decl);
1278         visitor.has_late_bound_regions
1279     }
1280
1281     match node {
1282         Node::TraitItem(item) => match item.kind {
1283             hir::TraitItemKind::Fn(ref sig, _) => {
1284                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1285             }
1286             _ => None,
1287         },
1288         Node::ImplItem(item) => match item.kind {
1289             hir::ImplItemKind::Fn(ref sig, _) => {
1290                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1291             }
1292             _ => None,
1293         },
1294         Node::ForeignItem(item) => match item.kind {
1295             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1296                 has_late_bound_regions(tcx, generics, fn_decl)
1297             }
1298             _ => None,
1299         },
1300         Node::Item(item) => match item.kind {
1301             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1302                 has_late_bound_regions(tcx, generics, &sig.decl)
1303             }
1304             _ => None,
1305         },
1306         _ => None,
1307     }
1308 }
1309
1310 struct AnonConstInParamListDetector {
1311     in_param_list: bool,
1312     found_anon_const_in_list: bool,
1313     ct: HirId,
1314 }
1315
1316 impl<'v> Visitor<'v> for AnonConstInParamListDetector {
1317     type Map = intravisit::ErasedMap<'v>;
1318
1319     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1320         NestedVisitorMap::None
1321     }
1322
1323     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1324         let prev = self.in_param_list;
1325         self.in_param_list = true;
1326         intravisit::walk_generic_param(self, p);
1327         self.in_param_list = prev;
1328     }
1329
1330     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1331         if self.in_param_list && self.ct == c.hir_id {
1332             self.found_anon_const_in_list = true;
1333         } else {
1334             intravisit::walk_anon_const(self, c)
1335         }
1336     }
1337 }
1338
1339 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1340     use rustc_hir::*;
1341
1342     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1343
1344     let node = tcx.hir().get(hir_id);
1345     let parent_def_id = match node {
1346         Node::ImplItem(_)
1347         | Node::TraitItem(_)
1348         | Node::Variant(_)
1349         | Node::Ctor(..)
1350         | Node::Field(_) => {
1351             let parent_id = tcx.hir().get_parent_item(hir_id);
1352             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1353         }
1354         // FIXME(#43408) always enable this once `lazy_normalization` is
1355         // stable enough and does not need a feature gate anymore.
1356         Node::AnonConst(_) => {
1357             let parent_id = tcx.hir().get_parent_item(hir_id);
1358             let parent_def_id = tcx.hir().local_def_id(parent_id);
1359
1360             let mut in_param_list = false;
1361             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1362                 if let Some(generics) = node.generics() {
1363                     let mut visitor = AnonConstInParamListDetector {
1364                         in_param_list: false,
1365                         found_anon_const_in_list: false,
1366                         ct: hir_id,
1367                     };
1368
1369                     visitor.visit_generics(generics);
1370                     in_param_list = visitor.found_anon_const_in_list;
1371                     break;
1372                 }
1373             }
1374
1375             if in_param_list {
1376                 // We do not allow generic parameters in anon consts if we are inside
1377                 // of a param list.
1378                 //
1379                 // This affects both default type bindings, e.g. `struct<T, U = [u8; std::mem::size_of::<T>()]>(T, U)`,
1380                 // and the types of const parameters, e.g. `struct V<const N: usize, const M: [u8; N]>();`.
1381                 None
1382             } else if tcx.lazy_normalization() {
1383                 // HACK(eddyb) this provides the correct generics when
1384                 // `feature(const_generics)` is enabled, so that const expressions
1385                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1386                 //
1387                 // Note that we do not supply the parent generics when using
1388                 // `min_const_generics`.
1389                 Some(parent_def_id.to_def_id())
1390             } else {
1391                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1392                 match parent_node {
1393                     // HACK(eddyb) this provides the correct generics for repeat
1394                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1395                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1396                     // as they shouldn't be able to cause query cycle errors.
1397                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1398                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1399                         if constant.hir_id == hir_id =>
1400                     {
1401                         Some(parent_def_id.to_def_id())
1402                     }
1403
1404                     _ => None,
1405                 }
1406             }
1407         }
1408         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1409             Some(tcx.closure_base_def_id(def_id))
1410         }
1411         Node::Item(item) => match item.kind {
1412             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1413                 impl_trait_fn.or_else(|| {
1414                     let parent_id = tcx.hir().get_parent_item(hir_id);
1415                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1416                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1417                     // Opaque types are always nested within another item, and
1418                     // inherit the generics of the item.
1419                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1420                 })
1421             }
1422             _ => None,
1423         },
1424         _ => None,
1425     };
1426
1427     let mut opt_self = None;
1428     let mut allow_defaults = false;
1429
1430     let no_generics = hir::Generics::empty();
1431     let ast_generics = match node {
1432         Node::TraitItem(item) => &item.generics,
1433
1434         Node::ImplItem(item) => &item.generics,
1435
1436         Node::Item(item) => {
1437             match item.kind {
1438                 ItemKind::Fn(.., ref generics, _)
1439                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1440
1441                 ItemKind::TyAlias(_, ref generics)
1442                 | ItemKind::Enum(_, ref generics)
1443                 | ItemKind::Struct(_, ref generics)
1444                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1445                 | ItemKind::Union(_, ref generics) => {
1446                     allow_defaults = true;
1447                     generics
1448                 }
1449
1450                 ItemKind::Trait(_, _, ref generics, ..)
1451                 | ItemKind::TraitAlias(ref generics, ..) => {
1452                     // Add in the self type parameter.
1453                     //
1454                     // Something of a hack: use the node id for the trait, also as
1455                     // the node id for the Self type parameter.
1456                     let param_id = item.def_id;
1457
1458                     opt_self = Some(ty::GenericParamDef {
1459                         index: 0,
1460                         name: kw::SelfUpper,
1461                         def_id: param_id.to_def_id(),
1462                         pure_wrt_drop: false,
1463                         kind: ty::GenericParamDefKind::Type {
1464                             has_default: false,
1465                             object_lifetime_default: rl::Set1::Empty,
1466                             synthetic: None,
1467                         },
1468                     });
1469
1470                     allow_defaults = true;
1471                     generics
1472                 }
1473
1474                 _ => &no_generics,
1475             }
1476         }
1477
1478         Node::ForeignItem(item) => match item.kind {
1479             ForeignItemKind::Static(..) => &no_generics,
1480             ForeignItemKind::Fn(_, _, ref generics) => generics,
1481             ForeignItemKind::Type => &no_generics,
1482         },
1483
1484         _ => &no_generics,
1485     };
1486
1487     let has_self = opt_self.is_some();
1488     let mut parent_has_self = false;
1489     let mut own_start = has_self as u32;
1490     let parent_count = parent_def_id.map_or(0, |def_id| {
1491         let generics = tcx.generics_of(def_id);
1492         assert_eq!(has_self, false);
1493         parent_has_self = generics.has_self;
1494         own_start = generics.count() as u32;
1495         generics.parent_count + generics.params.len()
1496     });
1497
1498     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1499
1500     if let Some(opt_self) = opt_self {
1501         params.push(opt_self);
1502     }
1503
1504     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1505     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1506         name: param.name.ident().name,
1507         index: own_start + i as u32,
1508         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1509         pure_wrt_drop: param.pure_wrt_drop,
1510         kind: ty::GenericParamDefKind::Lifetime,
1511     }));
1512
1513     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1514
1515     // Now create the real type and const parameters.
1516     let type_start = own_start - has_self as u32 + params.len() as u32;
1517     let mut i = 0;
1518
1519     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1520         GenericParamKind::Lifetime { .. } => None,
1521         GenericParamKind::Type { ref default, synthetic, .. } => {
1522             if !allow_defaults && default.is_some() {
1523                 if !tcx.features().default_type_parameter_fallback {
1524                     tcx.struct_span_lint_hir(
1525                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1526                         param.hir_id,
1527                         param.span,
1528                         |lint| {
1529                             lint.build(
1530                                 "defaults for type parameters are only allowed in \
1531                                  `struct`, `enum`, `type`, or `trait` definitions",
1532                             )
1533                             .emit();
1534                         },
1535                     );
1536                 }
1537             }
1538
1539             let kind = ty::GenericParamDefKind::Type {
1540                 has_default: default.is_some(),
1541                 object_lifetime_default: object_lifetime_defaults
1542                     .as_ref()
1543                     .map_or(rl::Set1::Empty, |o| o[i]),
1544                 synthetic,
1545             };
1546
1547             let param_def = ty::GenericParamDef {
1548                 index: type_start + i as u32,
1549                 name: param.name.ident().name,
1550                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1551                 pure_wrt_drop: param.pure_wrt_drop,
1552                 kind,
1553             };
1554             i += 1;
1555             Some(param_def)
1556         }
1557         GenericParamKind::Const { default, .. } => {
1558             if !allow_defaults && default.is_some() {
1559                 tcx.sess.span_err(
1560                     param.span,
1561                     "defaults for const parameters are only allowed in \
1562                     `struct`, `enum`, `type`, or `trait` definitions",
1563                 );
1564             }
1565
1566             let param_def = ty::GenericParamDef {
1567                 index: type_start + i as u32,
1568                 name: param.name.ident().name,
1569                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1570                 pure_wrt_drop: param.pure_wrt_drop,
1571                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1572             };
1573             i += 1;
1574             Some(param_def)
1575         }
1576     }));
1577
1578     // provide junk type parameter defs - the only place that
1579     // cares about anything but the length is instantiation,
1580     // and we don't do that for closures.
1581     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1582         let dummy_args = if gen.is_some() {
1583             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1584         } else {
1585             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1586         };
1587
1588         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1589             index: type_start + i as u32,
1590             name: Symbol::intern(arg),
1591             def_id,
1592             pure_wrt_drop: false,
1593             kind: ty::GenericParamDefKind::Type {
1594                 has_default: false,
1595                 object_lifetime_default: rl::Set1::Empty,
1596                 synthetic: None,
1597             },
1598         }));
1599     }
1600
1601     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1602
1603     ty::Generics {
1604         parent: parent_def_id,
1605         parent_count,
1606         params,
1607         param_def_id_to_index,
1608         has_self: has_self || parent_has_self,
1609         has_late_bound_regions: has_late_bound_regions(tcx, node),
1610     }
1611 }
1612
1613 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1614     generic_args
1615         .iter()
1616         .filter_map(|arg| match arg {
1617             hir::GenericArg::Type(ty) => Some(ty),
1618             _ => None,
1619         })
1620         .any(is_suggestable_infer_ty)
1621 }
1622
1623 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1624 /// use inference to provide suggestions for the appropriate type if possible.
1625 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1626     use hir::TyKind::*;
1627     match &ty.kind {
1628         Infer => true,
1629         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1630         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1631         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1632         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1633         Path(hir::QPath::TypeRelative(ty, segment)) => {
1634             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1635         }
1636         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1637             ty_opt.map_or(false, is_suggestable_infer_ty)
1638                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1639         }
1640         _ => false,
1641     }
1642 }
1643
1644 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1645     if let hir::FnRetTy::Return(ref ty) = output {
1646         if is_suggestable_infer_ty(ty) {
1647             return Some(&**ty);
1648         }
1649     }
1650     None
1651 }
1652
1653 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1654     use rustc_hir::Node::*;
1655     use rustc_hir::*;
1656
1657     let def_id = def_id.expect_local();
1658     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1659
1660     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1661
1662     match tcx.hir().get(hir_id) {
1663         TraitItem(hir::TraitItem {
1664             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1665             ident,
1666             generics,
1667             ..
1668         })
1669         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1670         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1671             match get_infer_ret_ty(&sig.decl.output) {
1672                 Some(ty) => {
1673                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1674                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1675                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1676                         ty::ReErased => tcx.lifetimes.re_static,
1677                         _ => r,
1678                     });
1679
1680                     let mut visitor = PlaceholderHirTyCollector::default();
1681                     visitor.visit_ty(ty);
1682                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1683                     let ret_ty = fn_sig.output();
1684                     if ret_ty != tcx.ty_error() {
1685                         if !ret_ty.is_closure() {
1686                             let ret_ty_str = match ret_ty.kind() {
1687                                 // Suggest a function pointer return type instead of a unique function definition
1688                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1689                                 // syntax)
1690                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1691                                 _ => ret_ty.to_string(),
1692                             };
1693                             diag.span_suggestion(
1694                                 ty.span,
1695                                 "replace with the correct return type",
1696                                 ret_ty_str,
1697                                 Applicability::MaybeIncorrect,
1698                             );
1699                         } else {
1700                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1701                             // to prevent the user from getting a papercut while trying to use the unique closure
1702                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1703                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1704                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1705                         }
1706                     }
1707                     diag.emit();
1708
1709                     ty::Binder::bind(fn_sig)
1710                 }
1711                 None => <dyn AstConv<'_>>::ty_of_fn(
1712                     &icx,
1713                     sig.header.unsafety,
1714                     sig.header.abi,
1715                     &sig.decl,
1716                     &generics,
1717                     Some(ident.span),
1718                     None,
1719                 ),
1720             }
1721         }
1722
1723         TraitItem(hir::TraitItem {
1724             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1725             ident,
1726             generics,
1727             ..
1728         }) => <dyn AstConv<'_>>::ty_of_fn(
1729             &icx,
1730             header.unsafety,
1731             header.abi,
1732             decl,
1733             &generics,
1734             Some(ident.span),
1735             None,
1736         ),
1737
1738         ForeignItem(&hir::ForeignItem {
1739             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1740             ident,
1741             ..
1742         }) => {
1743             let abi = tcx.hir().get_foreign_abi(hir_id);
1744             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1745         }
1746
1747         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1748             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1749             let inputs =
1750                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1751             ty::Binder::bind(tcx.mk_fn_sig(
1752                 inputs,
1753                 ty,
1754                 false,
1755                 hir::Unsafety::Normal,
1756                 abi::Abi::Rust,
1757             ))
1758         }
1759
1760         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1761             // Closure signatures are not like other function
1762             // signatures and cannot be accessed through `fn_sig`. For
1763             // example, a closure signature excludes the `self`
1764             // argument. In any case they are embedded within the
1765             // closure type as part of the `ClosureSubsts`.
1766             //
1767             // To get the signature of a closure, you should use the
1768             // `sig` method on the `ClosureSubsts`:
1769             //
1770             //    substs.as_closure().sig(def_id, tcx)
1771             bug!(
1772                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1773             );
1774         }
1775
1776         x => {
1777             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1778         }
1779     }
1780 }
1781
1782 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1783     let icx = ItemCtxt::new(tcx, def_id);
1784
1785     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1786     match tcx.hir().expect_item(hir_id).kind {
1787         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1788             let selfty = tcx.type_of(def_id);
1789             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1790         }),
1791         _ => bug!(),
1792     }
1793 }
1794
1795 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1796     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1797     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1798     let item = tcx.hir().expect_item(hir_id);
1799     match &item.kind {
1800         hir::ItemKind::Impl(hir::Impl {
1801             polarity: hir::ImplPolarity::Negative(span),
1802             of_trait,
1803             ..
1804         }) => {
1805             if is_rustc_reservation {
1806                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1807                 tcx.sess.span_err(span, "reservation impls can't be negative");
1808             }
1809             ty::ImplPolarity::Negative
1810         }
1811         hir::ItemKind::Impl(hir::Impl {
1812             polarity: hir::ImplPolarity::Positive,
1813             of_trait: None,
1814             ..
1815         }) => {
1816             if is_rustc_reservation {
1817                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1818             }
1819             ty::ImplPolarity::Positive
1820         }
1821         hir::ItemKind::Impl(hir::Impl {
1822             polarity: hir::ImplPolarity::Positive,
1823             of_trait: Some(_),
1824             ..
1825         }) => {
1826             if is_rustc_reservation {
1827                 ty::ImplPolarity::Reservation
1828             } else {
1829                 ty::ImplPolarity::Positive
1830             }
1831         }
1832         item => bug!("impl_polarity: {:?} not an impl", item),
1833     }
1834 }
1835
1836 /// Returns the early-bound lifetimes declared in this generics
1837 /// listing. For anything other than fns/methods, this is just all
1838 /// the lifetimes that are declared. For fns or methods, we have to
1839 /// screen out those that do not appear in any where-clauses etc using
1840 /// `resolve_lifetime::early_bound_lifetimes`.
1841 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1842     tcx: TyCtxt<'tcx>,
1843     generics: &'a hir::Generics<'a>,
1844 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1845     generics.params.iter().filter(move |param| match param.kind {
1846         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1847         _ => false,
1848     })
1849 }
1850
1851 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1852 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1853 /// inferred constraints concerning which regions outlive other regions.
1854 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1855     debug!("predicates_defined_on({:?})", def_id);
1856     let mut result = tcx.explicit_predicates_of(def_id);
1857     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1858     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1859     if !inferred_outlives.is_empty() {
1860         debug!(
1861             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1862             def_id, inferred_outlives,
1863         );
1864         if result.predicates.is_empty() {
1865             result.predicates = inferred_outlives;
1866         } else {
1867             result.predicates = tcx
1868                 .arena
1869                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1870         }
1871     }
1872
1873     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1874     result
1875 }
1876
1877 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1878 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1879 /// `Self: Trait` predicates for traits.
1880 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1881     let mut result = tcx.predicates_defined_on(def_id);
1882
1883     if tcx.is_trait(def_id) {
1884         // For traits, add `Self: Trait` predicate. This is
1885         // not part of the predicates that a user writes, but it
1886         // is something that one must prove in order to invoke a
1887         // method or project an associated type.
1888         //
1889         // In the chalk setup, this predicate is not part of the
1890         // "predicates" for a trait item. But it is useful in
1891         // rustc because if you directly (e.g.) invoke a trait
1892         // method like `Trait::method(...)`, you must naturally
1893         // prove that the trait applies to the types that were
1894         // used, and adding the predicate into this list ensures
1895         // that this is done.
1896         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
1897         result.predicates =
1898             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
1899                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
1900                 span,
1901             ))));
1902     }
1903     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1904     result
1905 }
1906
1907 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1908 /// N.B., this does not include any implied/inferred constraints.
1909 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1910     use rustc_hir::*;
1911
1912     debug!("explicit_predicates_of(def_id={:?})", def_id);
1913
1914     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1915     let node = tcx.hir().get(hir_id);
1916
1917     let mut is_trait = None;
1918     let mut is_default_impl_trait = None;
1919
1920     let icx = ItemCtxt::new(tcx, def_id);
1921     let constness = icx.default_constness_for_trait_bounds();
1922
1923     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
1924
1925     // We use an `IndexSet` to preserves order of insertion.
1926     // Preserving the order of insertion is important here so as not to break UI tests.
1927     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
1928
1929     let ast_generics = match node {
1930         Node::TraitItem(item) => &item.generics,
1931
1932         Node::ImplItem(item) => &item.generics,
1933
1934         Node::Item(item) => {
1935             match item.kind {
1936                 ItemKind::Impl(ref impl_) => {
1937                     if impl_.defaultness.is_default() {
1938                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
1939                     }
1940                     &impl_.generics
1941                 }
1942                 ItemKind::Fn(.., ref generics, _)
1943                 | ItemKind::TyAlias(_, ref generics)
1944                 | ItemKind::Enum(_, ref generics)
1945                 | ItemKind::Struct(_, ref generics)
1946                 | ItemKind::Union(_, ref generics) => generics,
1947
1948                 ItemKind::Trait(_, _, ref generics, ..) => {
1949                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1950                     generics
1951                 }
1952                 ItemKind::TraitAlias(ref generics, _) => {
1953                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
1954                     generics
1955                 }
1956                 ItemKind::OpaqueTy(OpaqueTy {
1957                     bounds: _,
1958                     impl_trait_fn,
1959                     ref generics,
1960                     origin: _,
1961                 }) => {
1962                     if impl_trait_fn.is_some() {
1963                         // return-position impl trait
1964                         //
1965                         // We don't inherit predicates from the parent here:
1966                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
1967                         // then the return type is `f::<'static, T>::{{opaque}}`.
1968                         //
1969                         // If we inherited the predicates of `f` then we would
1970                         // require that `T: 'static` to show that the return
1971                         // type is well-formed.
1972                         //
1973                         // The only way to have something with this opaque type
1974                         // is from the return type of the containing function,
1975                         // which will ensure that the function's predicates
1976                         // hold.
1977                         return ty::GenericPredicates { parent: None, predicates: &[] };
1978                     } else {
1979                         // type-alias impl trait
1980                         generics
1981                     }
1982                 }
1983
1984                 _ => NO_GENERICS,
1985             }
1986         }
1987
1988         Node::ForeignItem(item) => match item.kind {
1989             ForeignItemKind::Static(..) => NO_GENERICS,
1990             ForeignItemKind::Fn(_, _, ref generics) => generics,
1991             ForeignItemKind::Type => NO_GENERICS,
1992         },
1993
1994         _ => NO_GENERICS,
1995     };
1996
1997     let generics = tcx.generics_of(def_id);
1998     let parent_count = generics.parent_count as u32;
1999     let has_own_self = generics.has_self && parent_count == 0;
2000
2001     // Below we'll consider the bounds on the type parameters (including `Self`)
2002     // and the explicit where-clauses, but to get the full set of predicates
2003     // on a trait we need to add in the supertrait bounds and bounds found on
2004     // associated types.
2005     if let Some(_trait_ref) = is_trait {
2006         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2007     }
2008
2009     // In default impls, we can assume that the self type implements
2010     // the trait. So in:
2011     //
2012     //     default impl Foo for Bar { .. }
2013     //
2014     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2015     // (see below). Recall that a default impl is not itself an impl, but rather a
2016     // set of defaults that can be incorporated into another impl.
2017     if let Some(trait_ref) = is_default_impl_trait {
2018         predicates.insert((
2019             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
2020             tcx.def_span(def_id),
2021         ));
2022     }
2023
2024     // Collect the region predicates that were declared inline as
2025     // well. In the case of parameters declared on a fn or method, we
2026     // have to be careful to only iterate over early-bound regions.
2027     let mut index = parent_count + has_own_self as u32;
2028     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2029         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2030             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2031             index,
2032             name: param.name.ident().name,
2033         }));
2034         index += 1;
2035
2036         match param.kind {
2037             GenericParamKind::Lifetime { .. } => {
2038                 param.bounds.iter().for_each(|bound| match bound {
2039                     hir::GenericBound::Outlives(lt) => {
2040                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, &lt, None);
2041                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2042                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2043                     }
2044                     _ => bug!(),
2045                 });
2046             }
2047             _ => bug!(),
2048         }
2049     }
2050
2051     // Collect the predicates that were written inline by the user on each
2052     // type parameter (e.g., `<T: Foo>`).
2053     for param in ast_generics.params {
2054         match param.kind {
2055             // We already dealt with early bound lifetimes above.
2056             GenericParamKind::Lifetime { .. } => (),
2057             GenericParamKind::Type { .. } => {
2058                 let name = param.name.ident().name;
2059                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2060                 index += 1;
2061
2062                 let sized = SizedByDefault::Yes;
2063                 let bounds = <dyn AstConv<'_>>::compute_bounds(
2064                     &icx,
2065                     param_ty,
2066                     &param.bounds,
2067                     sized,
2068                     param.span,
2069                 );
2070                 predicates.extend(bounds.predicates(tcx, param_ty));
2071             }
2072             GenericParamKind::Const { .. } => {
2073                 // Bounds on const parameters are currently not possible.
2074                 debug_assert!(param.bounds.is_empty());
2075                 index += 1;
2076             }
2077         }
2078     }
2079
2080     // Add in the bounds that appear in the where-clause.
2081     let where_clause = &ast_generics.where_clause;
2082     for predicate in where_clause.predicates {
2083         match predicate {
2084             hir::WherePredicate::BoundPredicate(bound_pred) => {
2085                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2086
2087                 // Keep the type around in a dummy predicate, in case of no bounds.
2088                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2089                 // is still checked for WF.
2090                 if bound_pred.bounds.is_empty() {
2091                     if let ty::Param(_) = ty.kind() {
2092                         // This is a `where T:`, which can be in the HIR from the
2093                         // transformation that moves `?Sized` to `T`'s declaration.
2094                         // We can skip the predicate because type parameters are
2095                         // trivially WF, but also we *should*, to avoid exposing
2096                         // users who never wrote `where Type:,` themselves, to
2097                         // compiler/tooling bugs from not handling WF predicates.
2098                     } else {
2099                         let span = bound_pred.bounded_ty.span;
2100                         let re_root_empty = tcx.lifetimes.re_root_empty;
2101                         let predicate = ty::Binder::bind(ty::PredicateKind::TypeOutlives(
2102                             ty::OutlivesPredicate(ty, re_root_empty),
2103                         ));
2104                         predicates.insert((predicate.to_predicate(tcx), span));
2105                     }
2106                 }
2107
2108                 for bound in bound_pred.bounds.iter() {
2109                     match bound {
2110                         hir::GenericBound::Trait(poly_trait_ref, modifier) => {
2111                             let constness = match modifier {
2112                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2113                                 hir::TraitBoundModifier::None => constness,
2114                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
2115                             };
2116
2117                             let mut bounds = Bounds::default();
2118                             let _ = <dyn AstConv<'_>>::instantiate_poly_trait_ref(
2119                                 &icx,
2120                                 &poly_trait_ref,
2121                                 constness,
2122                                 ty,
2123                                 &mut bounds,
2124                             );
2125                             predicates.extend(bounds.predicates(tcx, ty));
2126                         }
2127
2128                         &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2129                             let mut bounds = Bounds::default();
2130                             <dyn AstConv<'_>>::instantiate_lang_item_trait_ref(
2131                                 &icx,
2132                                 lang_item,
2133                                 span,
2134                                 hir_id,
2135                                 args,
2136                                 ty,
2137                                 &mut bounds,
2138                             );
2139                             predicates.extend(bounds.predicates(tcx, ty));
2140                         }
2141
2142                         hir::GenericBound::Outlives(lifetime) => {
2143                             let region =
2144                                 <dyn AstConv<'_>>::ast_region_to_region(&icx, lifetime, None);
2145                             predicates.insert((
2146                                 ty::Binder::bind(ty::PredicateKind::TypeOutlives(
2147                                     ty::OutlivesPredicate(ty, region),
2148                                 ))
2149                                 .to_predicate(tcx),
2150                                 lifetime.span,
2151                             ));
2152                         }
2153                     }
2154                 }
2155             }
2156
2157             hir::WherePredicate::RegionPredicate(region_pred) => {
2158                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2159                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2160                     let (r2, span) = match bound {
2161                         hir::GenericBound::Outlives(lt) => {
2162                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2163                         }
2164                         _ => bug!(),
2165                     };
2166                     let pred = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
2167                         .to_predicate(icx.tcx);
2168
2169                     (pred, span)
2170                 }))
2171             }
2172
2173             hir::WherePredicate::EqPredicate(..) => {
2174                 // FIXME(#20041)
2175             }
2176         }
2177     }
2178
2179     if tcx.features().const_evaluatable_checked {
2180         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2181     }
2182
2183     let mut predicates: Vec<_> = predicates.into_iter().collect();
2184
2185     // Subtle: before we store the predicates into the tcx, we
2186     // sort them so that predicates like `T: Foo<Item=U>` come
2187     // before uses of `U`.  This avoids false ambiguity errors
2188     // in trait checking. See `setup_constraining_predicates`
2189     // for details.
2190     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2191         let self_ty = tcx.type_of(def_id);
2192         let trait_ref = tcx.impl_trait_ref(def_id);
2193         cgp::setup_constraining_predicates(
2194             tcx,
2195             &mut predicates,
2196             trait_ref,
2197             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2198         );
2199     }
2200
2201     let result = ty::GenericPredicates {
2202         parent: generics.parent,
2203         predicates: tcx.arena.alloc_from_iter(predicates),
2204     };
2205     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2206     result
2207 }
2208
2209 fn const_evaluatable_predicates_of<'tcx>(
2210     tcx: TyCtxt<'tcx>,
2211     def_id: LocalDefId,
2212 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2213     struct ConstCollector<'tcx> {
2214         tcx: TyCtxt<'tcx>,
2215         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2216     }
2217
2218     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2219         type Map = Map<'tcx>;
2220
2221         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2222             intravisit::NestedVisitorMap::None
2223         }
2224
2225         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2226             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2227             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2228             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2229                 assert_eq!(uv.promoted, None);
2230                 let span = self.tcx.hir().span(c.hir_id);
2231                 self.preds.insert((
2232                     ty::PredicateKind::ConstEvaluatable(uv.def, uv.substs).to_predicate(self.tcx),
2233                     span,
2234                 ));
2235             }
2236         }
2237     }
2238
2239     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2240     let node = tcx.hir().get(hir_id);
2241
2242     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2243     if let hir::Node::Item(item) = node {
2244         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2245             if let Some(of_trait) = &impl_.of_trait {
2246                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2247                 collector.visit_trait_ref(of_trait);
2248             }
2249
2250             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2251             collector.visit_ty(impl_.self_ty);
2252         }
2253     }
2254
2255     if let Some(generics) = node.generics() {
2256         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2257         collector.visit_generics(generics);
2258     }
2259
2260     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2261         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2262         collector.visit_fn_decl(fn_sig.decl);
2263     }
2264     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2265
2266     collector.preds
2267 }
2268
2269 fn trait_explicit_predicates_and_bounds(
2270     tcx: TyCtxt<'_>,
2271     def_id: LocalDefId,
2272 ) -> ty::GenericPredicates<'_> {
2273     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2274     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2275 }
2276
2277 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2278     if let DefKind::Trait = tcx.def_kind(def_id) {
2279         // Remove bounds on associated types from the predicates, they will be
2280         // returned by `explicit_item_bounds`.
2281         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2282         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2283
2284         let is_assoc_item_ty = |ty: Ty<'_>| {
2285             // For a predicate from a where clause to become a bound on an
2286             // associated type:
2287             // * It must use the identity substs of the item.
2288             //     * Since any generic parameters on the item are not in scope,
2289             //       this means that the item is not a GAT, and its identity
2290             //       substs are the same as the trait's.
2291             // * It must be an associated type for this trait (*not* a
2292             //   supertrait).
2293             if let ty::Projection(projection) = ty.kind() {
2294                 projection.substs == trait_identity_substs
2295                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2296             } else {
2297                 false
2298             }
2299         };
2300
2301         let predicates: Vec<_> = predicates_and_bounds
2302             .predicates
2303             .iter()
2304             .copied()
2305             .filter(|(pred, _)| match pred.kind().skip_binder() {
2306                 ty::PredicateKind::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
2307                 ty::PredicateKind::Projection(proj) => {
2308                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2309                 }
2310                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2311                 _ => true,
2312             })
2313             .collect();
2314         if predicates.len() == predicates_and_bounds.predicates.len() {
2315             predicates_and_bounds
2316         } else {
2317             ty::GenericPredicates {
2318                 parent: predicates_and_bounds.parent,
2319                 predicates: tcx.arena.alloc_slice(&predicates),
2320             }
2321         }
2322     } else {
2323         gather_explicit_predicates_of(tcx, def_id)
2324     }
2325 }
2326
2327 fn projection_ty_from_predicates(
2328     tcx: TyCtxt<'tcx>,
2329     key: (
2330         // ty_def_id
2331         DefId,
2332         // def_id of `N` in `<T as Trait>::N`
2333         DefId,
2334     ),
2335 ) -> Option<ty::ProjectionTy<'tcx>> {
2336     let (ty_def_id, item_def_id) = key;
2337     let mut projection_ty = None;
2338     for (predicate, _) in tcx.predicates_of(ty_def_id).predicates {
2339         if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder()
2340         {
2341             if item_def_id == projection_predicate.projection_ty.item_def_id {
2342                 projection_ty = Some(projection_predicate.projection_ty);
2343                 break;
2344             }
2345         }
2346     }
2347     projection_ty
2348 }
2349
2350 /// Converts a specific `GenericBound` from the AST into a set of
2351 /// predicates that apply to the self type. A vector is returned
2352 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2353 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2354 /// and `<T as Bar>::X == i32`).
2355 fn predicates_from_bound<'tcx>(
2356     astconv: &dyn AstConv<'tcx>,
2357     param_ty: Ty<'tcx>,
2358     bound: &'tcx hir::GenericBound<'tcx>,
2359     constness: hir::Constness,
2360 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2361     match *bound {
2362         hir::GenericBound::Trait(ref tr, modifier) => {
2363             let constness = match modifier {
2364                 hir::TraitBoundModifier::Maybe => return vec![],
2365                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2366                 hir::TraitBoundModifier::None => constness,
2367             };
2368
2369             let mut bounds = Bounds::default();
2370             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2371             bounds.predicates(astconv.tcx(), param_ty)
2372         }
2373         hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2374             let mut bounds = Bounds::default();
2375             astconv.instantiate_lang_item_trait_ref(
2376                 lang_item,
2377                 span,
2378                 hir_id,
2379                 args,
2380                 param_ty,
2381                 &mut bounds,
2382             );
2383             bounds.predicates(astconv.tcx(), param_ty)
2384         }
2385         hir::GenericBound::Outlives(ref lifetime) => {
2386             let region = astconv.ast_region_to_region(lifetime, None);
2387             let pred = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2388                 .to_predicate(astconv.tcx());
2389             vec![(pred, lifetime.span)]
2390         }
2391     }
2392 }
2393
2394 fn compute_sig_of_foreign_fn_decl<'tcx>(
2395     tcx: TyCtxt<'tcx>,
2396     def_id: DefId,
2397     decl: &'tcx hir::FnDecl<'tcx>,
2398     abi: abi::Abi,
2399     ident: Ident,
2400 ) -> ty::PolyFnSig<'tcx> {
2401     let unsafety = if abi == abi::Abi::RustIntrinsic {
2402         intrinsic_operation_unsafety(tcx.item_name(def_id))
2403     } else {
2404         hir::Unsafety::Unsafe
2405     };
2406     let fty = <dyn AstConv<'_>>::ty_of_fn(
2407         &ItemCtxt::new(tcx, def_id),
2408         unsafety,
2409         abi,
2410         decl,
2411         &hir::Generics::empty(),
2412         Some(ident.span),
2413         None,
2414     );
2415
2416     // Feature gate SIMD types in FFI, since I am not sure that the
2417     // ABIs are handled at all correctly. -huonw
2418     if abi != abi::Abi::RustIntrinsic
2419         && abi != abi::Abi::PlatformIntrinsic
2420         && !tcx.features().simd_ffi
2421     {
2422         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2423             if ty.is_simd() {
2424                 let snip = tcx
2425                     .sess
2426                     .source_map()
2427                     .span_to_snippet(ast_ty.span)
2428                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2429                 tcx.sess
2430                     .struct_span_err(
2431                         ast_ty.span,
2432                         &format!(
2433                             "use of SIMD type{} in FFI is highly experimental and \
2434                              may result in invalid code",
2435                             snip
2436                         ),
2437                     )
2438                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2439                     .emit();
2440             }
2441         };
2442         for (input, ty) in decl.inputs.iter().zip(fty.inputs().skip_binder()) {
2443             check(&input, ty)
2444         }
2445         if let hir::FnRetTy::Return(ref ty) = decl.output {
2446             check(&ty, fty.output().skip_binder())
2447         }
2448     }
2449
2450     fty
2451 }
2452
2453 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2454     match tcx.hir().get_if_local(def_id) {
2455         Some(Node::ForeignItem(..)) => true,
2456         Some(_) => false,
2457         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2458     }
2459 }
2460
2461 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2462     match tcx.hir().get_if_local(def_id) {
2463         Some(
2464             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2465             | Node::ForeignItem(&hir::ForeignItem {
2466                 kind: hir::ForeignItemKind::Static(_, mutbl),
2467                 ..
2468             }),
2469         ) => Some(mutbl),
2470         Some(_) => None,
2471         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2472     }
2473 }
2474
2475 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2476     match tcx.hir().get_if_local(def_id) {
2477         Some(Node::Expr(&rustc_hir::Expr {
2478             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2479             ..
2480         })) => tcx.hir().body(body_id).generator_kind(),
2481         Some(_) => None,
2482         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2483     }
2484 }
2485
2486 fn from_target_feature(
2487     tcx: TyCtxt<'_>,
2488     id: DefId,
2489     attr: &ast::Attribute,
2490     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2491     target_features: &mut Vec<Symbol>,
2492 ) {
2493     let list = match attr.meta_item_list() {
2494         Some(list) => list,
2495         None => return,
2496     };
2497     let bad_item = |span| {
2498         let msg = "malformed `target_feature` attribute input";
2499         let code = "enable = \"..\"".to_owned();
2500         tcx.sess
2501             .struct_span_err(span, &msg)
2502             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2503             .emit();
2504     };
2505     let rust_features = tcx.features();
2506     for item in list {
2507         // Only `enable = ...` is accepted in the meta-item list.
2508         if !item.has_name(sym::enable) {
2509             bad_item(item.span());
2510             continue;
2511         }
2512
2513         // Must be of the form `enable = "..."` (a string).
2514         let value = match item.value_str() {
2515             Some(value) => value,
2516             None => {
2517                 bad_item(item.span());
2518                 continue;
2519             }
2520         };
2521
2522         // We allow comma separation to enable multiple features.
2523         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2524             let feature_gate = match supported_target_features.get(feature) {
2525                 Some(g) => g,
2526                 None => {
2527                     let msg =
2528                         format!("the feature named `{}` is not valid for this target", feature);
2529                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2530                     err.span_label(
2531                         item.span(),
2532                         format!("`{}` is not valid for this target", feature),
2533                     );
2534                     if let Some(stripped) = feature.strip_prefix('+') {
2535                         let valid = supported_target_features.contains_key(stripped);
2536                         if valid {
2537                             err.help("consider removing the leading `+` in the feature name");
2538                         }
2539                     }
2540                     err.emit();
2541                     return None;
2542                 }
2543             };
2544
2545             // Only allow features whose feature gates have been enabled.
2546             let allowed = match feature_gate.as_ref().copied() {
2547                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2548                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2549                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2550                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2551                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2552                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2553                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2554                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2555                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2556                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2557                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2558                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2559                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2560                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2561                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2562                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2563                 Some(name) => bug!("unknown target feature gate {}", name),
2564                 None => true,
2565             };
2566             if !allowed && id.is_local() {
2567                 feature_err(
2568                     &tcx.sess.parse_sess,
2569                     feature_gate.unwrap(),
2570                     item.span(),
2571                     &format!("the target feature `{}` is currently unstable", feature),
2572                 )
2573                 .emit();
2574             }
2575             Some(Symbol::intern(feature))
2576         }));
2577     }
2578 }
2579
2580 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2581     use rustc_middle::mir::mono::Linkage::*;
2582
2583     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2584     // applicable to variable declarations and may not really make sense for
2585     // Rust code in the first place but allow them anyway and trust that the
2586     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2587     // up in the future.
2588     //
2589     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2590     // and don't have to be, LLVM treats them as no-ops.
2591     match name {
2592         "appending" => Appending,
2593         "available_externally" => AvailableExternally,
2594         "common" => Common,
2595         "extern_weak" => ExternalWeak,
2596         "external" => External,
2597         "internal" => Internal,
2598         "linkonce" => LinkOnceAny,
2599         "linkonce_odr" => LinkOnceODR,
2600         "private" => Private,
2601         "weak" => WeakAny,
2602         "weak_odr" => WeakODR,
2603         _ => {
2604             let span = tcx.hir().span_if_local(def_id);
2605             if let Some(span) = span {
2606                 tcx.sess.span_fatal(span, "invalid linkage specified")
2607             } else {
2608                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2609             }
2610         }
2611     }
2612 }
2613
2614 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2615     let attrs = tcx.get_attrs(id);
2616
2617     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2618     if should_inherit_track_caller(tcx, id) {
2619         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2620     }
2621
2622     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2623
2624     let mut inline_span = None;
2625     let mut link_ordinal_span = None;
2626     let mut no_sanitize_span = None;
2627     for attr in attrs.iter() {
2628         if tcx.sess.check_name(attr, sym::cold) {
2629             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2630         } else if tcx.sess.check_name(attr, sym::rustc_allocator) {
2631             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2632         } else if tcx.sess.check_name(attr, sym::unwind) {
2633             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2634         } else if tcx.sess.check_name(attr, sym::ffi_returns_twice) {
2635             if tcx.is_foreign_item(id) {
2636                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2637             } else {
2638                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2639                 struct_span_err!(
2640                     tcx.sess,
2641                     attr.span,
2642                     E0724,
2643                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2644                 )
2645                 .emit();
2646             }
2647         } else if tcx.sess.check_name(attr, sym::ffi_pure) {
2648             if tcx.is_foreign_item(id) {
2649                 if attrs.iter().any(|a| tcx.sess.check_name(a, sym::ffi_const)) {
2650                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2651                     struct_span_err!(
2652                         tcx.sess,
2653                         attr.span,
2654                         E0757,
2655                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2656                     )
2657                     .emit();
2658                 } else {
2659                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2660                 }
2661             } else {
2662                 // `#[ffi_pure]` is only allowed on foreign functions
2663                 struct_span_err!(
2664                     tcx.sess,
2665                     attr.span,
2666                     E0755,
2667                     "`#[ffi_pure]` may only be used on foreign functions"
2668                 )
2669                 .emit();
2670             }
2671         } else if tcx.sess.check_name(attr, sym::ffi_const) {
2672             if tcx.is_foreign_item(id) {
2673                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2674             } else {
2675                 // `#[ffi_const]` is only allowed on foreign functions
2676                 struct_span_err!(
2677                     tcx.sess,
2678                     attr.span,
2679                     E0756,
2680                     "`#[ffi_const]` may only be used on foreign functions"
2681                 )
2682                 .emit();
2683             }
2684         } else if tcx.sess.check_name(attr, sym::rustc_allocator_nounwind) {
2685             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2686         } else if tcx.sess.check_name(attr, sym::naked) {
2687             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2688         } else if tcx.sess.check_name(attr, sym::no_mangle) {
2689             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2690         } else if tcx.sess.check_name(attr, sym::rustc_std_internal_symbol) {
2691             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2692         } else if tcx.sess.check_name(attr, sym::used) {
2693             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2694         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
2695             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2696                 struct_span_err!(
2697                     tcx.sess,
2698                     attr.span,
2699                     E0776,
2700                     "`#[cmse_nonsecure_entry]` requires C ABI"
2701                 )
2702                 .emit();
2703             }
2704             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2705                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2706                     .emit();
2707             }
2708             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2709         } else if tcx.sess.check_name(attr, sym::thread_local) {
2710             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2711         } else if tcx.sess.check_name(attr, sym::track_caller) {
2712             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2713                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2714                     .emit();
2715             }
2716             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2717         } else if tcx.sess.check_name(attr, sym::export_name) {
2718             if let Some(s) = attr.value_str() {
2719                 if s.as_str().contains('\0') {
2720                     // `#[export_name = ...]` will be converted to a null-terminated string,
2721                     // so it may not contain any null characters.
2722                     struct_span_err!(
2723                         tcx.sess,
2724                         attr.span,
2725                         E0648,
2726                         "`export_name` may not contain null characters"
2727                     )
2728                     .emit();
2729                 }
2730                 codegen_fn_attrs.export_name = Some(s);
2731             }
2732         } else if tcx.sess.check_name(attr, sym::target_feature) {
2733             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2734                 if !tcx.features().target_feature_11 {
2735                     let mut err = feature_err(
2736                         &tcx.sess.parse_sess,
2737                         sym::target_feature_11,
2738                         attr.span,
2739                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2740                     );
2741                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2742                     err.emit();
2743                 } else if let Some(local_id) = id.as_local() {
2744                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2745                 }
2746             }
2747             from_target_feature(
2748                 tcx,
2749                 id,
2750                 attr,
2751                 &supported_target_features,
2752                 &mut codegen_fn_attrs.target_features,
2753             );
2754         } else if tcx.sess.check_name(attr, sym::linkage) {
2755             if let Some(val) = attr.value_str() {
2756                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2757             }
2758         } else if tcx.sess.check_name(attr, sym::link_section) {
2759             if let Some(val) = attr.value_str() {
2760                 if val.as_str().bytes().any(|b| b == 0) {
2761                     let msg = format!(
2762                         "illegal null byte in link_section \
2763                          value: `{}`",
2764                         &val
2765                     );
2766                     tcx.sess.span_err(attr.span, &msg);
2767                 } else {
2768                     codegen_fn_attrs.link_section = Some(val);
2769                 }
2770             }
2771         } else if tcx.sess.check_name(attr, sym::link_name) {
2772             codegen_fn_attrs.link_name = attr.value_str();
2773         } else if tcx.sess.check_name(attr, sym::link_ordinal) {
2774             link_ordinal_span = Some(attr.span);
2775             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2776                 codegen_fn_attrs.link_ordinal = ordinal;
2777             }
2778         } else if tcx.sess.check_name(attr, sym::no_sanitize) {
2779             no_sanitize_span = Some(attr.span);
2780             if let Some(list) = attr.meta_item_list() {
2781                 for item in list.iter() {
2782                     if item.has_name(sym::address) {
2783                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2784                     } else if item.has_name(sym::memory) {
2785                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2786                     } else if item.has_name(sym::thread) {
2787                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2788                     } else if item.has_name(sym::hwaddress) {
2789                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2790                     } else {
2791                         tcx.sess
2792                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2793                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2794                             .emit();
2795                     }
2796                 }
2797             }
2798         } else if tcx.sess.check_name(attr, sym::instruction_set) {
2799             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2800                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2801                     [NestedMetaItem::MetaItem(set)] => {
2802                         let segments =
2803                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2804                         match segments.as_slice() {
2805                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2806                                 if !tcx.sess.target.has_thumb_interworking {
2807                                     struct_span_err!(
2808                                         tcx.sess.diagnostic(),
2809                                         attr.span,
2810                                         E0779,
2811                                         "target does not support `#[instruction_set]`"
2812                                     )
2813                                     .emit();
2814                                     None
2815                                 } else if segments[1] == sym::a32 {
2816                                     Some(InstructionSetAttr::ArmA32)
2817                                 } else if segments[1] == sym::t32 {
2818                                     Some(InstructionSetAttr::ArmT32)
2819                                 } else {
2820                                     unreachable!()
2821                                 }
2822                             }
2823                             _ => {
2824                                 struct_span_err!(
2825                                     tcx.sess.diagnostic(),
2826                                     attr.span,
2827                                     E0779,
2828                                     "invalid instruction set specified",
2829                                 )
2830                                 .emit();
2831                                 None
2832                             }
2833                         }
2834                     }
2835                     [] => {
2836                         struct_span_err!(
2837                             tcx.sess.diagnostic(),
2838                             attr.span,
2839                             E0778,
2840                             "`#[instruction_set]` requires an argument"
2841                         )
2842                         .emit();
2843                         None
2844                     }
2845                     _ => {
2846                         struct_span_err!(
2847                             tcx.sess.diagnostic(),
2848                             attr.span,
2849                             E0779,
2850                             "cannot specify more than one instruction set"
2851                         )
2852                         .emit();
2853                         None
2854                     }
2855                 },
2856                 _ => {
2857                     struct_span_err!(
2858                         tcx.sess.diagnostic(),
2859                         attr.span,
2860                         E0778,
2861                         "must specify an instruction set"
2862                     )
2863                     .emit();
2864                     None
2865                 }
2866             };
2867         }
2868     }
2869
2870     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2871         if !attr.has_name(sym::inline) {
2872             return ia;
2873         }
2874         match attr.meta().map(|i| i.kind) {
2875             Some(MetaItemKind::Word) => {
2876                 tcx.sess.mark_attr_used(attr);
2877                 InlineAttr::Hint
2878             }
2879             Some(MetaItemKind::List(ref items)) => {
2880                 tcx.sess.mark_attr_used(attr);
2881                 inline_span = Some(attr.span);
2882                 if items.len() != 1 {
2883                     struct_span_err!(
2884                         tcx.sess.diagnostic(),
2885                         attr.span,
2886                         E0534,
2887                         "expected one argument"
2888                     )
2889                     .emit();
2890                     InlineAttr::None
2891                 } else if list_contains_name(&items[..], sym::always) {
2892                     if tcx.sess.instrument_coverage() {
2893                         // Fixes Issue #82875. Forced inlining allows LLVM to discard functions
2894                         // marked with `#[inline(always)]`, which can break coverage reporting if
2895                         // that function was referenced from a coverage map.
2896                         //
2897                         // FIXME(#83429): Is there a better place, e.g., in codegen, to check and
2898                         // convert `Always` to `Hint`?
2899                         InlineAttr::Hint
2900                     } else {
2901                         InlineAttr::Always
2902                     }
2903                 } else if list_contains_name(&items[..], sym::never) {
2904                     InlineAttr::Never
2905                 } else {
2906                     struct_span_err!(
2907                         tcx.sess.diagnostic(),
2908                         items[0].span(),
2909                         E0535,
2910                         "invalid argument"
2911                     )
2912                     .emit();
2913
2914                     InlineAttr::None
2915                 }
2916             }
2917             Some(MetaItemKind::NameValue(_)) => ia,
2918             None => ia,
2919         }
2920     });
2921
2922     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2923         if !attr.has_name(sym::optimize) {
2924             return ia;
2925         }
2926         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2927         match attr.meta().map(|i| i.kind) {
2928             Some(MetaItemKind::Word) => {
2929                 err(attr.span, "expected one argument");
2930                 ia
2931             }
2932             Some(MetaItemKind::List(ref items)) => {
2933                 tcx.sess.mark_attr_used(attr);
2934                 inline_span = Some(attr.span);
2935                 if items.len() != 1 {
2936                     err(attr.span, "expected one argument");
2937                     OptimizeAttr::None
2938                 } else if list_contains_name(&items[..], sym::size) {
2939                     OptimizeAttr::Size
2940                 } else if list_contains_name(&items[..], sym::speed) {
2941                     OptimizeAttr::Speed
2942                 } else {
2943                     err(items[0].span(), "invalid argument");
2944                     OptimizeAttr::None
2945                 }
2946             }
2947             Some(MetaItemKind::NameValue(_)) => ia,
2948             None => ia,
2949         }
2950     });
2951
2952     // #73631: closures inherit `#[target_feature]` annotations
2953     if tcx.features().target_feature_11 && tcx.is_closure(id) {
2954         let owner_id = tcx.parent(id).expect("closure should have a parent");
2955         codegen_fn_attrs
2956             .target_features
2957             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
2958     }
2959
2960     // If a function uses #[target_feature] it can't be inlined into general
2961     // purpose functions as they wouldn't have the right target features
2962     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2963     // respected.
2964     if !codegen_fn_attrs.target_features.is_empty() {
2965         if codegen_fn_attrs.inline == InlineAttr::Always {
2966             if let Some(span) = inline_span {
2967                 tcx.sess.span_err(
2968                     span,
2969                     "cannot use `#[inline(always)]` with \
2970                      `#[target_feature]`",
2971                 );
2972             }
2973         }
2974     }
2975
2976     if !codegen_fn_attrs.no_sanitize.is_empty() {
2977         if codegen_fn_attrs.inline == InlineAttr::Always {
2978             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2979                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
2980                 tcx.struct_span_lint_hir(
2981                     lint::builtin::INLINE_NO_SANITIZE,
2982                     hir_id,
2983                     no_sanitize_span,
2984                     |lint| {
2985                         lint.build("`no_sanitize` will have no effect after inlining")
2986                             .span_note(inline_span, "inlining requested here")
2987                             .emit();
2988                     },
2989                 )
2990             }
2991         }
2992     }
2993
2994     // Weak lang items have the same semantics as "std internal" symbols in the
2995     // sense that they're preserved through all our LTO passes and only
2996     // strippable by the linker.
2997     //
2998     // Additionally weak lang items have predetermined symbol names.
2999     if tcx.is_weak_lang_item(id) {
3000         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3001     }
3002     let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
3003     if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
3004         codegen_fn_attrs.export_name = Some(name);
3005         codegen_fn_attrs.link_name = Some(name);
3006     }
3007     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3008
3009     // Internal symbols to the standard library all have no_mangle semantics in
3010     // that they have defined symbol names present in the function name. This
3011     // also applies to weak symbols where they all have known symbol names.
3012     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3013         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3014     }
3015
3016     codegen_fn_attrs
3017 }
3018
3019 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3020 /// applied to the method prototype.
3021 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3022     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3023         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3024             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3025                 if let Some(trait_item) = tcx
3026                     .associated_items(trait_def_id)
3027                     .filter_by_name_unhygienic(impl_item.ident.name)
3028                     .find(move |trait_item| {
3029                         trait_item.kind == ty::AssocKind::Fn
3030                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3031                     })
3032                 {
3033                     return tcx
3034                         .codegen_fn_attrs(trait_item.def_id)
3035                         .flags
3036                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3037                 }
3038             }
3039         }
3040     }
3041
3042     false
3043 }
3044
3045 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
3046     use rustc_ast::{Lit, LitIntType, LitKind};
3047     let meta_item_list = attr.meta_item_list();
3048     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3049     let sole_meta_list = match meta_item_list {
3050         Some([item]) => item.literal(),
3051         _ => None,
3052     };
3053     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3054         if *ordinal <= usize::MAX as u128 {
3055             Some(*ordinal as usize)
3056         } else {
3057             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3058             tcx.sess
3059                 .struct_span_err(attr.span, &msg)
3060                 .note("the value may not exceed `usize::MAX`")
3061                 .emit();
3062             None
3063         }
3064     } else {
3065         tcx.sess
3066             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3067             .note("an unsuffixed integer value, e.g., `1`, is expected")
3068             .emit();
3069         None
3070     }
3071 }
3072
3073 fn check_link_name_xor_ordinal(
3074     tcx: TyCtxt<'_>,
3075     codegen_fn_attrs: &CodegenFnAttrs,
3076     inline_span: Option<Span>,
3077 ) {
3078     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3079         return;
3080     }
3081     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3082     if let Some(span) = inline_span {
3083         tcx.sess.span_err(span, msg);
3084     } else {
3085         tcx.sess.err(msg);
3086     }
3087 }
3088
3089 /// Checks the function annotated with `#[target_feature]` is not a safe
3090 /// trait method implementation, reporting an error if it is.
3091 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3092     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3093     let node = tcx.hir().get(hir_id);
3094     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3095         let parent_id = tcx.hir().get_parent_item(hir_id);
3096         let parent_item = tcx.hir().expect_item(parent_id);
3097         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3098             tcx.sess
3099                 .struct_span_err(
3100                     attr_span,
3101                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3102                 )
3103                 .span_label(attr_span, "cannot be applied to safe trait method")
3104                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3105                 .emit();
3106         }
3107     }
3108 }