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 // ignore-tidy-filelength
  19
  20 use crate::astconv::{AstConv, SizedByDefault};
  21 use crate::bounds::Bounds;
  22 use crate::check::intrinsic::intrinsic_operation_unsafety;
  23 use crate::constrained_generic_params as cgp;
  24 use crate::errors;
  25 use crate::middle::resolve_lifetime as rl;
  26 use rustc_ast as ast;
  27 use rustc_ast::{MetaItemKind, NestedMetaItem};
  28 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  29 use rustc_data_structures::captures::Captures;
  30 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  31 use rustc_errors::{struct_span_err, Applicability};
  32 use rustc_hir as hir;
  33 use rustc_hir::def::{CtorKind, DefKind, Res};
  34 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  35 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  36 use rustc_hir::weak_lang_items;
  37 use rustc_hir::{GenericParamKind, HirId, Node};
  38 use rustc_middle::hir::map::blocks::FnLikeNode;
  39 use rustc_middle::hir::map::Map;
  40 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  41 use rustc_middle::mir::mono::Linkage;
  42 use rustc_middle::ty::query::Providers;
  43 use rustc_middle::ty::subst::InternalSubsts;
  44 use rustc_middle::ty::util::Discr;
  45 use rustc_middle::ty::util::IntTypeExt;
  46 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  47 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
  48 use rustc_session::lint;
  49 use rustc_session::parse::feature_err;
  50 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  51 use rustc_span::{Span, DUMMY_SP};
  52 use rustc_target::spec::{abi, SanitizerSet};
  53 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  54 use std::iter;
  55
  56 mod item_bounds;
  57 mod type_of;
  58
  59 struct OnlySelfBounds(bool);
  60
  61 ///////////////////////////////////////////////////////////////////////////
  62 // Main entry point
  63
  64 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  65     tcx.hir().visit_item_likes_in_module(
  66         module_def_id,
  67         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  68     );
  69 }
  70
  71 pub fn provide(providers: &mut Providers) {
  72     *providers = Providers {
  73         opt_const_param_of: type_of::opt_const_param_of,
  74         type_of: type_of::type_of,
  75         item_bounds: item_bounds::item_bounds,
  76         explicit_item_bounds: item_bounds::explicit_item_bounds,
  77         generics_of,
  78         predicates_of,
  79         predicates_defined_on,
  80         explicit_predicates_of,
  81         super_predicates_of,
  82         super_predicates_that_define_assoc_type,
  83         trait_explicit_predicates_and_bounds,
  84         type_param_predicates,
  85         trait_def,
  86         adt_def,
  87         fn_sig,
  88         impl_trait_ref,
  89         impl_polarity,
  90         is_foreign_item,
  91         static_mutability,
  92         generator_kind,
  93         codegen_fn_attrs,
  94         collect_mod_item_types,
  95         ..*providers
  96     };
  97 }
  98
  99 ///////////////////////////////////////////////////////////////////////////
 100
 101 /// Context specific to some particular item. This is what implements
 102 /// `AstConv`. It has information about the predicates that are defined
 103 /// on the trait. Unfortunately, this predicate information is
 104 /// available in various different forms at various points in the
 105 /// process. So we can't just store a pointer to e.g., the AST or the
 106 /// parsed ty form, we have to be more flexible. To this end, the
 107 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 108 /// `get_type_parameter_bounds` requests, drawing the information from
 109 /// the AST (`hir::Generics`), recursively.
 110 pub struct ItemCtxt<'tcx> {
 111     tcx: TyCtxt<'tcx>,
 112     item_def_id: DefId,
 113 }
 114
 115 ///////////////////////////////////////////////////////////////////////////
 116
 117 #[derive(Default)]
 118 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 119
 120 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 121     type Map = intravisit::ErasedMap<'v>;
 122
 123     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 124         NestedVisitorMap::None
 125     }
 126     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 127         if let hir::TyKind::Infer = t.kind {
 128             self.0.push(t.span);
 129         }
 130         intravisit::walk_ty(self, t)
 131     }
 132 }
 133
 134 struct CollectItemTypesVisitor<'tcx> {
 135     tcx: TyCtxt<'tcx>,
 136 }
 137
 138 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 139 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 140 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 141 crate fn placeholder_type_error(
 142     tcx: TyCtxt<'tcx>,
 143     span: Option<Span>,
 144     generics: &[hir::GenericParam<'_>],
 145     placeholder_types: Vec<Span>,
 146     suggest: bool,
 147     hir_ty: Option<&hir::Ty<'_>>,
 148     kind: &'static str,
 149 ) {
 150     if placeholder_types.is_empty() {
 151         return;
 152     }
 153
 154     let type_name = generics.next_type_param_name(None);
 155     let mut sugg: Vec<_> =
 156         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 157
 158     if generics.is_empty() {
 159         if let Some(span) = span {
 160             sugg.push((span, format!("<{}>", type_name)));
 161         }
 162     } else if let Some(arg) = generics
 163         .iter()
 164         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 165     {
 166         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 167         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 168         sugg.push((arg.span, (*type_name).to_string()));
 169     } else {
 170         let last = generics.iter().last().unwrap();
 171         sugg.push((
 172             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 173             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 174             format!(", {}", type_name),
 175         ));
 176     }
 177
 178     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);
 179
 180     // Suggest, but only if it is not a function in const or static
 181     if suggest {
 182         let mut is_fn = false;
 183         let mut is_const_or_static = false;
 184
 185         if let Some(hir_ty) = hir_ty {
 186             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 187                 is_fn = true;
 188
 189                 // Check if parent is const or static
 190                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 191                 let parent_node = tcx.hir().get(parent_id);
 192
 193                 is_const_or_static = match parent_node {
 194                     Node::Item(&hir::Item {
 195                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 196                         ..
 197                     })
 198                     | Node::TraitItem(&hir::TraitItem {
 199                         kind: hir::TraitItemKind::Const(..),
 200                         ..
 201                     })
 202                     | Node::ImplItem(&hir::ImplItem {
 203                         kind: hir::ImplItemKind::Const(..), ..
 204                     }) => true,
 205                     _ => false,
 206                 };
 207             }
 208         }
 209
 210         // if function is wrapped around a const or static,
 211         // then don't show the suggestion
 212         if !(is_fn && is_const_or_static) {
 213             err.multipart_suggestion(
 214                 "use type parameters instead",
 215                 sugg,
 216                 Applicability::HasPlaceholders,
 217             );
 218         }
 219     }
 220     err.emit();
 221 }
 222
 223 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 224     let (generics, suggest) = match &item.kind {
 225         hir::ItemKind::Union(_, generics)
 226         | hir::ItemKind::Enum(_, generics)
 227         | hir::ItemKind::TraitAlias(generics, _)
 228         | hir::ItemKind::Trait(_, _, generics, ..)
 229         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 230         | hir::ItemKind::Struct(_, generics) => (generics, true),
 231         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 232         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 233         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 234         _ => return,
 235     };
 236
 237     let mut visitor = PlaceholderHirTyCollector::default();
 238     visitor.visit_item(item);
 239
 240     placeholder_type_error(
 241         tcx,
 242         Some(generics.span),
 243         generics.params,
 244         visitor.0,
 245         suggest,
 246         None,
 247         item.kind.descr(),
 248     );
 249 }
 250
 251 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 252     type Map = Map<'tcx>;
 253
 254     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 255         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 256     }
 257
 258     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 259         convert_item(self.tcx, item.item_id());
 260         reject_placeholder_type_signatures_in_item(self.tcx, item);
 261         intravisit::walk_item(self, item);
 262     }
 263
 264     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 265         for param in generics.params {
 266             match param.kind {
 267                 hir::GenericParamKind::Lifetime { .. } => {}
 268                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 269                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 270                     self.tcx.ensure().type_of(def_id);
 271                 }
 272                 hir::GenericParamKind::Type { .. } => {}
 273                 hir::GenericParamKind::Const { default, .. } => {
 274                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 275                     self.tcx.ensure().type_of(def_id);
 276                     if let Some(default) = default {
 277                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 278                         // need to store default and type of default
 279                         self.tcx.ensure().type_of(default_def_id);
 280                         self.tcx.ensure().const_param_default(def_id);
 281                     }
 282                 }
 283             }
 284         }
 285         intravisit::walk_generics(self, generics);
 286     }
 287
 288     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 289         if let hir::ExprKind::Closure(..) = expr.kind {
 290             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 291             self.tcx.ensure().generics_of(def_id);
 292             self.tcx.ensure().type_of(def_id);
 293         }
 294         intravisit::walk_expr(self, expr);
 295     }
 296
 297     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 298         convert_trait_item(self.tcx, trait_item.trait_item_id());
 299         intravisit::walk_trait_item(self, trait_item);
 300     }
 301
 302     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 303         convert_impl_item(self.tcx, impl_item.impl_item_id());
 304         intravisit::walk_impl_item(self, impl_item);
 305     }
 306 }
 307
 308 ///////////////////////////////////////////////////////////////////////////
 309 // Utility types and common code for the above passes.
 310
 311 fn bad_placeholder_type(
 312     tcx: TyCtxt<'tcx>,
 313     mut spans: Vec<Span>,
 314     kind: &'static str,
 315 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 316     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 317
 318     spans.sort();
 319     let mut err = struct_span_err!(
 320         tcx.sess,
 321         spans.clone(),
 322         E0121,
 323         "the type placeholder `_` is not allowed within types on item signatures for {}",
 324         kind
 325     );
 326     for span in spans {
 327         err.span_label(span, "not allowed in type signatures");
 328     }
 329     err
 330 }
 331
 332 impl ItemCtxt<'tcx> {
 333     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 334         ItemCtxt { tcx, item_def_id }
 335     }
 336
 337     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 338         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 339     }
 340
 341     pub fn hir_id(&self) -> hir::HirId {
 342         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 343     }
 344
 345     pub fn node(&self) -> hir::Node<'tcx> {
 346         self.tcx.hir().get(self.hir_id())
 347     }
 348 }
 349
 350 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 351     fn tcx(&self) -> TyCtxt<'tcx> {
 352         self.tcx
 353     }
 354
 355     fn item_def_id(&self) -> Option<DefId> {
 356         Some(self.item_def_id)
 357     }
 358
 359     fn default_constness_for_trait_bounds(&self) -> hir::Constness {
 360         if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
 361             fn_like.constness()
 362         } else {
 363             hir::Constness::NotConst
 364         }
 365     }
 366
 367     fn get_type_parameter_bounds(
 368         &self,
 369         span: Span,
 370         def_id: DefId,
 371         assoc_name: Ident,
 372     ) -> ty::GenericPredicates<'tcx> {
 373         self.tcx.at(span).type_param_predicates((
 374             self.item_def_id,
 375             def_id.expect_local(),
 376             assoc_name,
 377         ))
 378     }
 379
 380     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 381         None
 382     }
 383
 384     fn allow_ty_infer(&self) -> bool {
 385         false
 386     }
 387
 388     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 389         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 390     }
 391
 392     fn ct_infer(
 393         &self,
 394         ty: Ty<'tcx>,
 395         _: Option<&ty::GenericParamDef>,
 396         span: Span,
 397     ) -> &'tcx Const<'tcx> {
 398         bad_placeholder_type(self.tcx(), vec![span], "generic").emit();
 399         // Typeck doesn't expect erased regions to be returned from `type_of`.
 400         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 401             ty::ReErased => self.tcx.lifetimes.re_static,
 402             _ => r,
 403         });
 404         self.tcx().const_error(ty)
 405     }
 406
 407     fn projected_ty_from_poly_trait_ref(
 408         &self,
 409         span: Span,
 410         item_def_id: DefId,
 411         item_segment: &hir::PathSegment<'_>,
 412         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 413     ) -> Ty<'tcx> {
 414         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 415             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 416                 self,
 417                 self.tcx,
 418                 span,
 419                 item_def_id,
 420                 item_segment,
 421                 trait_ref.substs,
 422             );
 423             self.tcx().mk_projection(item_def_id, item_substs)
 424         } else {
 425             // There are no late-bound regions; we can just ignore the binder.
 426             let mut err = struct_span_err!(
 427                 self.tcx().sess,
 428                 span,
 429                 E0212,
 430                 "cannot use the associated type of a trait \
 431                  with uninferred generic parameters"
 432             );
 433
 434             match self.node() {
 435                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 436                     let item =
 437                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 438                     match &item.kind {
 439                         hir::ItemKind::Enum(_, generics)
 440                         | hir::ItemKind::Struct(_, generics)
 441                         | hir::ItemKind::Union(_, generics) => {
 442                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 443                             let (lt_sp, sugg) = match generics.params {
 444                                 [] => (generics.span, format!("<{}>", lt_name)),
 445                                 [bound, ..] => {
 446                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 447                                 }
 448                             };
 449                             let suggestions = vec![
 450                                 (lt_sp, sugg),
 451                                 (
 452                                     span,
 453                                     format!(
 454                                         "{}::{}",
 455                                         // Replace the existing lifetimes with a new named lifetime.
 456                                         self.tcx
 457                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 458                                                 self.tcx.mk_region(ty::ReEarlyBound(
 459                                                     ty::EarlyBoundRegion {
 460                                                         def_id: item_def_id,
 461                                                         index: 0,
 462                                                         name: Symbol::intern(&lt_name),
 463                                                     },
 464                                                 ))
 465                                             })
 466                                             .0,
 467                                         item_segment.ident
 468                                     ),
 469                                 ),
 470                             ];
 471                             err.multipart_suggestion(
 472                                 "use a fully qualified path with explicit lifetimes",
 473                                 suggestions,
 474                                 Applicability::MaybeIncorrect,
 475                             );
 476                         }
 477                         _ => {}
 478                     }
 479                 }
 480                 hir::Node::Item(hir::Item {
 481                     kind:
 482                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 483                     ..
 484                 }) => {}
 485                 hir::Node::Item(_)
 486                 | hir::Node::ForeignItem(_)
 487                 | hir::Node::TraitItem(_)
 488                 | hir::Node::ImplItem(_) => {
 489                     err.span_suggestion(
 490                         span,
 491                         "use a fully qualified path with inferred lifetimes",
 492                         format!(
 493                             "{}::{}",
 494                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 495                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 496                             item_segment.ident
 497                         ),
 498                         Applicability::MaybeIncorrect,
 499                     );
 500                 }
 501                 _ => {}
 502             }
 503             err.emit();
 504             self.tcx().ty_error()
 505         }
 506     }
 507
 508     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 509         // Types in item signatures are not normalized to avoid undue dependencies.
 510         ty
 511     }
 512
 513     fn set_tainted_by_errors(&self) {
 514         // There's no obvious place to track this, so just let it go.
 515     }
 516
 517     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 518         // There's no place to record types from signatures?
 519     }
 520 }
 521
 522 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 523 fn get_new_lifetime_name<'tcx>(
 524     tcx: TyCtxt<'tcx>,
 525     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 526     generics: &hir::Generics<'tcx>,
 527 ) -> String {
 528     let existing_lifetimes = tcx
 529         .collect_referenced_late_bound_regions(&poly_trait_ref)
 530         .into_iter()
 531         .filter_map(|lt| {
 532             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 533                 Some(name.as_str().to_string())
 534             } else {
 535                 None
 536             }
 537         })
 538         .chain(generics.params.iter().filter_map(|param| {
 539             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 540                 Some(param.name.ident().as_str().to_string())
 541             } else {
 542                 None
 543             }
 544         }))
 545         .collect::<FxHashSet<String>>();
 546
 547     let a_to_z_repeat_n = |n| {
 548         (b'a'..=b'z').map(move |c| {
 549             let mut s = '\''.to_string();
 550             s.extend(std::iter::repeat(char::from(c)).take(n));
 551             s
 552         })
 553     };
 554
 555     // If all single char lifetime names are present, we wrap around and double the chars.
 556     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 557 }
 558
 559 /// Returns the predicates defined on `item_def_id` of the form
 560 /// `X: Foo` where `X` is the type parameter `def_id`.
 561 fn type_param_predicates(
 562     tcx: TyCtxt<'_>,
 563     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 564 ) -> ty::GenericPredicates<'_> {
 565     use rustc_hir::*;
 566
 567     // In the AST, bounds can derive from two places. Either
 568     // written inline like `<T: Foo>` or in a where-clause like
 569     // `where T: Foo`.
 570
 571     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 572     let param_owner = tcx.hir().ty_param_owner(param_id);
 573     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 574     let generics = tcx.generics_of(param_owner_def_id);
 575     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 576     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 577
 578     // Don't look for bounds where the type parameter isn't in scope.
 579     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 580         None
 581     } else {
 582         tcx.generics_of(item_def_id).parent
 583     };
 584
 585     let mut result = parent
 586         .map(|parent| {
 587             let icx = ItemCtxt::new(tcx, parent);
 588             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 589         })
 590         .unwrap_or_default();
 591     let mut extend = None;
 592
 593     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 594     let ast_generics = match tcx.hir().get(item_hir_id) {
 595         Node::TraitItem(item) => &item.generics,
 596
 597         Node::ImplItem(item) => &item.generics,
 598
 599         Node::Item(item) => {
 600             match item.kind {
 601                 ItemKind::Fn(.., ref generics, _)
 602                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 603                 | ItemKind::TyAlias(_, ref generics)
 604                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 605                 | ItemKind::Enum(_, ref generics)
 606                 | ItemKind::Struct(_, ref generics)
 607                 | ItemKind::Union(_, ref generics) => generics,
 608                 ItemKind::Trait(_, _, ref generics, ..) => {
 609                     // Implied `Self: Trait` and supertrait bounds.
 610                     if param_id == item_hir_id {
 611                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 612                         extend =
 613                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 614                     }
 615                     generics
 616                 }
 617                 _ => return result,
 618             }
 619         }
 620
 621         Node::ForeignItem(item) => match item.kind {
 622             ForeignItemKind::Fn(_, _, ref generics) => generics,
 623             _ => return result,
 624         },
 625
 626         _ => return result,
 627     };
 628
 629     let icx = ItemCtxt::new(tcx, item_def_id);
 630     let extra_predicates = extend.into_iter().chain(
 631         icx.type_parameter_bounds_in_generics(
 632             ast_generics,
 633             param_id,
 634             ty,
 635             OnlySelfBounds(true),
 636             Some(assoc_name),
 637         )
 638         .into_iter()
 639         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 640             ty::PredicateKind::Trait(data, _) => data.self_ty().is_param(index),
 641             _ => false,
 642         }),
 643     );
 644     result.predicates =
 645         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 646     result
 647 }
 648
 649 impl ItemCtxt<'tcx> {
 650     /// Finds bounds from `hir::Generics`. This requires scanning through the
 651     /// AST. We do this to avoid having to convert *all* the bounds, which
 652     /// would create artificial cycles. Instead, we can only convert the
 653     /// bounds for a type parameter `X` if `X::Foo` is used.
 654     fn type_parameter_bounds_in_generics(
 655         &self,
 656         ast_generics: &'tcx hir::Generics<'tcx>,
 657         param_id: hir::HirId,
 658         ty: Ty<'tcx>,
 659         only_self_bounds: OnlySelfBounds,
 660         assoc_name: Option<Ident>,
 661     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 662         let constness = self.default_constness_for_trait_bounds();
 663         let from_ty_params = ast_generics
 664             .params
 665             .iter()
 666             .filter_map(|param| match param.kind {
 667                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 668                 _ => None,
 669             })
 670             .flat_map(|bounds| bounds.iter())
 671             .filter(|b| match assoc_name {
 672                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 673                 None => true,
 674             })
 675             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 676
 677         let from_where_clauses = ast_generics
 678             .where_clause
 679             .predicates
 680             .iter()
 681             .filter_map(|wp| match *wp {
 682                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 683                 _ => None,
 684             })
 685             .flat_map(|bp| {
 686                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 687                     Some(ty)
 688                 } else if !only_self_bounds.0 {
 689                     Some(self.to_ty(&bp.bounded_ty))
 690                 } else {
 691                     None
 692                 };
 693                 bp.bounds
 694                     .iter()
 695                     .filter(|b| match assoc_name {
 696                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 697                         None => true,
 698                     })
 699                     .filter_map(move |b| bt.map(|bt| (bt, b)))
 700             })
 701             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 702
 703         from_ty_params.chain(from_where_clauses).collect()
 704     }
 705
 706     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 707         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 708
 709         match b {
 710             hir::GenericBound::Trait(poly_trait_ref, _) => {
 711                 let trait_ref = &poly_trait_ref.trait_ref;
 712                 if let Some(trait_did) = trait_ref.trait_def_id() {
 713                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 714                 } else {
 715                     false
 716                 }
 717             }
 718             _ => false,
 719         }
 720     }
 721 }
 722
 723 /// Tests whether this is the AST for a reference to the type
 724 /// parameter with ID `param_id`. We use this so as to avoid running
 725 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 726 /// conversion of the type to avoid inducing unnecessary cycles.
 727 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 728     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 729         match path.res {
 730             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 731                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 732             }
 733             _ => false,
 734         }
 735     } else {
 736         false
 737     }
 738 }
 739
 740 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 741     let it = tcx.hir().item(item_id);
 742     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 743     let def_id = item_id.def_id;
 744
 745     match it.kind {
 746         // These don't define types.
 747         hir::ItemKind::ExternCrate(_)
 748         | hir::ItemKind::Use(..)
 749         | hir::ItemKind::Mod(_)
 750         | hir::ItemKind::GlobalAsm(_) => {}
 751         hir::ItemKind::ForeignMod { items, .. } => {
 752             for item in items {
 753                 let item = tcx.hir().foreign_item(item.id);
 754                 tcx.ensure().generics_of(item.def_id);
 755                 tcx.ensure().type_of(item.def_id);
 756                 tcx.ensure().predicates_of(item.def_id);
 757                 match item.kind {
 758                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 759                     hir::ForeignItemKind::Static(..) => {
 760                         let mut visitor = PlaceholderHirTyCollector::default();
 761                         visitor.visit_foreign_item(item);
 762                         placeholder_type_error(
 763                             tcx,
 764                             None,
 765                             &[],
 766                             visitor.0,
 767                             false,
 768                             None,
 769                             "static variable",
 770                         );
 771                     }
 772                     _ => (),
 773                 }
 774             }
 775         }
 776         hir::ItemKind::Enum(ref enum_definition, _) => {
 777             tcx.ensure().generics_of(def_id);
 778             tcx.ensure().type_of(def_id);
 779             tcx.ensure().predicates_of(def_id);
 780             convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
 781         }
 782         hir::ItemKind::Impl { .. } => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.ensure().type_of(def_id);
 785             tcx.ensure().impl_trait_ref(def_id);
 786             tcx.ensure().predicates_of(def_id);
 787         }
 788         hir::ItemKind::Trait(..) => {
 789             tcx.ensure().generics_of(def_id);
 790             tcx.ensure().trait_def(def_id);
 791             tcx.at(it.span).super_predicates_of(def_id);
 792             tcx.ensure().predicates_of(def_id);
 793         }
 794         hir::ItemKind::TraitAlias(..) => {
 795             tcx.ensure().generics_of(def_id);
 796             tcx.at(it.span).super_predicates_of(def_id);
 797             tcx.ensure().predicates_of(def_id);
 798         }
 799         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 800             tcx.ensure().generics_of(def_id);
 801             tcx.ensure().type_of(def_id);
 802             tcx.ensure().predicates_of(def_id);
 803
 804             for f in struct_def.fields() {
 805                 let def_id = tcx.hir().local_def_id(f.hir_id);
 806                 tcx.ensure().generics_of(def_id);
 807                 tcx.ensure().type_of(def_id);
 808                 tcx.ensure().predicates_of(def_id);
 809             }
 810
 811             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 812                 convert_variant_ctor(tcx, ctor_hir_id);
 813             }
 814         }
 815
 816         // Desugared from `impl Trait`, so visited by the function's return type.
 817         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 818
 819         // Don't call `type_of` on opaque types, since that depends on type
 820         // checking function bodies. `check_item_type` ensures that it's called
 821         // instead.
 822         hir::ItemKind::OpaqueTy(..) => {
 823             tcx.ensure().generics_of(def_id);
 824             tcx.ensure().predicates_of(def_id);
 825             tcx.ensure().explicit_item_bounds(def_id);
 826         }
 827         hir::ItemKind::TyAlias(..)
 828         | hir::ItemKind::Static(..)
 829         | hir::ItemKind::Const(..)
 830         | hir::ItemKind::Fn(..) => {
 831             tcx.ensure().generics_of(def_id);
 832             tcx.ensure().type_of(def_id);
 833             tcx.ensure().predicates_of(def_id);
 834             match it.kind {
 835                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 836                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 837                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 838                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 839                     if let hir::TyKind::TraitObject(..) = ty.kind {
 840                         let mut visitor = PlaceholderHirTyCollector::default();
 841                         visitor.visit_item(it);
 842                         placeholder_type_error(
 843                             tcx,
 844                             None,
 845                             &[],
 846                             visitor.0,
 847                             false,
 848                             None,
 849                             it.kind.descr(),
 850                         );
 851                     }
 852                 }
 853                 _ => (),
 854             }
 855         }
 856     }
 857 }
 858
 859 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 860     let trait_item = tcx.hir().trait_item(trait_item_id);
 861     tcx.ensure().generics_of(trait_item_id.def_id);
 862
 863     match trait_item.kind {
 864         hir::TraitItemKind::Fn(..) => {
 865             tcx.ensure().type_of(trait_item_id.def_id);
 866             tcx.ensure().fn_sig(trait_item_id.def_id);
 867         }
 868
 869         hir::TraitItemKind::Const(.., Some(_)) => {
 870             tcx.ensure().type_of(trait_item_id.def_id);
 871         }
 872
 873         hir::TraitItemKind::Const(..) => {
 874             tcx.ensure().type_of(trait_item_id.def_id);
 875             // Account for `const C: _;`.
 876             let mut visitor = PlaceholderHirTyCollector::default();
 877             visitor.visit_trait_item(trait_item);
 878             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 879         }
 880
 881         hir::TraitItemKind::Type(_, Some(_)) => {
 882             tcx.ensure().item_bounds(trait_item_id.def_id);
 883             tcx.ensure().type_of(trait_item_id.def_id);
 884             // Account for `type T = _;`.
 885             let mut visitor = PlaceholderHirTyCollector::default();
 886             visitor.visit_trait_item(trait_item);
 887             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 888         }
 889
 890         hir::TraitItemKind::Type(_, None) => {
 891             tcx.ensure().item_bounds(trait_item_id.def_id);
 892             // #74612: Visit and try to find bad placeholders
 893             // even if there is no concrete type.
 894             let mut visitor = PlaceholderHirTyCollector::default();
 895             visitor.visit_trait_item(trait_item);
 896
 897             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 898         }
 899     };
 900
 901     tcx.ensure().predicates_of(trait_item_id.def_id);
 902 }
 903
 904 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 905     let def_id = impl_item_id.def_id;
 906     tcx.ensure().generics_of(def_id);
 907     tcx.ensure().type_of(def_id);
 908     tcx.ensure().predicates_of(def_id);
 909     let impl_item = tcx.hir().impl_item(impl_item_id);
 910     match impl_item.kind {
 911         hir::ImplItemKind::Fn(..) => {
 912             tcx.ensure().fn_sig(def_id);
 913         }
 914         hir::ImplItemKind::TyAlias(_) => {
 915             // Account for `type T = _;`
 916             let mut visitor = PlaceholderHirTyCollector::default();
 917             visitor.visit_impl_item(impl_item);
 918
 919             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 920         }
 921         hir::ImplItemKind::Const(..) => {}
 922     }
 923 }
 924
 925 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 926     let def_id = tcx.hir().local_def_id(ctor_id);
 927     tcx.ensure().generics_of(def_id);
 928     tcx.ensure().type_of(def_id);
 929     tcx.ensure().predicates_of(def_id);
 930 }
 931
 932 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 933     let def = tcx.adt_def(def_id);
 934     let repr_type = def.repr.discr_type();
 935     let initial = repr_type.initial_discriminant(tcx);
 936     let mut prev_discr = None::<Discr<'_>>;
 937
 938     // fill the discriminant values and field types
 939     for variant in variants {
 940         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 941         prev_discr = Some(
 942             if let Some(ref e) = variant.disr_expr {
 943                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 944                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 945             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 946                 Some(discr)
 947             } else {
 948                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 949                     .span_label(
 950                         variant.span,
 951                         format!("overflowed on value after {}", prev_discr.unwrap()),
 952                     )
 953                     .note(&format!(
 954                         "explicitly set `{} = {}` if that is desired outcome",
 955                         variant.ident, wrapped_discr
 956                     ))
 957                     .emit();
 958                 None
 959             }
 960             .unwrap_or(wrapped_discr),
 961         );
 962
 963         for f in variant.data.fields() {
 964             let def_id = tcx.hir().local_def_id(f.hir_id);
 965             tcx.ensure().generics_of(def_id);
 966             tcx.ensure().type_of(def_id);
 967             tcx.ensure().predicates_of(def_id);
 968         }
 969
 970         // Convert the ctor, if any. This also registers the variant as
 971         // an item.
 972         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 973             convert_variant_ctor(tcx, ctor_hir_id);
 974         }
 975     }
 976 }
 977
 978 fn convert_variant(
 979     tcx: TyCtxt<'_>,
 980     variant_did: Option<LocalDefId>,
 981     ctor_did: Option<LocalDefId>,
 982     ident: Ident,
 983     discr: ty::VariantDiscr,
 984     def: &hir::VariantData<'_>,
 985     adt_kind: ty::AdtKind,
 986     parent_did: LocalDefId,
 987 ) -> ty::VariantDef {
 988     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 989     let fields = def
 990         .fields()
 991         .iter()
 992         .map(|f| {
 993             let fid = tcx.hir().local_def_id(f.hir_id);
 994             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 995             if let Some(prev_span) = dup_span {
 996                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 997                     field_name: f.ident,
 998                     span: f.span,
 999                     prev_span,
1000                 });
1001             } else {
1002                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
1003             }
1004
1005             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
1006         })
1007         .collect();
1008     let recovered = match def {
1009         hir::VariantData::Struct(_, r) => *r,
1010         _ => false,
1011     };
1012     ty::VariantDef::new(
1013         ident,
1014         variant_did.map(LocalDefId::to_def_id),
1015         ctor_did.map(LocalDefId::to_def_id),
1016         discr,
1017         fields,
1018         CtorKind::from_hir(def),
1019         adt_kind,
1020         parent_did.to_def_id(),
1021         recovered,
1022         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1023             || variant_did.map_or(false, |variant_did| {
1024                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1025             }),
1026     )
1027 }
1028
1029 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1030     use rustc_hir::*;
1031
1032     let def_id = def_id.expect_local();
1033     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1034     let item = match tcx.hir().get(hir_id) {
1035         Node::Item(item) => item,
1036         _ => bug!(),
1037     };
1038
1039     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1040     let (kind, variants) = match item.kind {
1041         ItemKind::Enum(ref def, _) => {
1042             let mut distance_from_explicit = 0;
1043             let variants = def
1044                 .variants
1045                 .iter()
1046                 .map(|v| {
1047                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1048                     let ctor_did =
1049                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1050
1051                     let discr = if let Some(ref e) = v.disr_expr {
1052                         distance_from_explicit = 0;
1053                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1054                     } else {
1055                         ty::VariantDiscr::Relative(distance_from_explicit)
1056                     };
1057                     distance_from_explicit += 1;
1058
1059                     convert_variant(
1060                         tcx,
1061                         variant_did,
1062                         ctor_did,
1063                         v.ident,
1064                         discr,
1065                         &v.data,
1066                         AdtKind::Enum,
1067                         def_id,
1068                     )
1069                 })
1070                 .collect();
1071
1072             (AdtKind::Enum, variants)
1073         }
1074         ItemKind::Struct(ref def, _) => {
1075             let variant_did = None::<LocalDefId>;
1076             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1077
1078             let variants = std::iter::once(convert_variant(
1079                 tcx,
1080                 variant_did,
1081                 ctor_did,
1082                 item.ident,
1083                 ty::VariantDiscr::Relative(0),
1084                 def,
1085                 AdtKind::Struct,
1086                 def_id,
1087             ))
1088             .collect();
1089
1090             (AdtKind::Struct, variants)
1091         }
1092         ItemKind::Union(ref def, _) => {
1093             let variant_did = None;
1094             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1095
1096             let variants = std::iter::once(convert_variant(
1097                 tcx,
1098                 variant_did,
1099                 ctor_did,
1100                 item.ident,
1101                 ty::VariantDiscr::Relative(0),
1102                 def,
1103                 AdtKind::Union,
1104                 def_id,
1105             ))
1106             .collect();
1107
1108             (AdtKind::Union, variants)
1109         }
1110         _ => bug!(),
1111     };
1112     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1113 }
1114
1115 /// Ensures that the super-predicates of the trait with a `DefId`
1116 /// of `trait_def_id` are converted and stored. This also ensures that
1117 /// the transitive super-predicates are converted.
1118 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1119     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1120     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1121 }
1122
1123 /// Ensures that the super-predicates of the trait with a `DefId`
1124 /// of `trait_def_id` are converted and stored. This also ensures that
1125 /// the transitive super-predicates are converted.
1126 fn super_predicates_that_define_assoc_type(
1127     tcx: TyCtxt<'_>,
1128     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1129 ) -> ty::GenericPredicates<'_> {
1130     debug!(
1131         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1132         trait_def_id, assoc_name
1133     );
1134     if trait_def_id.is_local() {
1135         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1136         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1137
1138         let item = match tcx.hir().get(trait_hir_id) {
1139             Node::Item(item) => item,
1140             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1141         };
1142
1143         let (generics, bounds) = match item.kind {
1144             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1145             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1146             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1147         };
1148
1149         let icx = ItemCtxt::new(tcx, trait_def_id);
1150
1151         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1152         let self_param_ty = tcx.types.self_param;
1153         let superbounds1 = if let Some(assoc_name) = assoc_name {
1154             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1155                 &icx,
1156                 self_param_ty,
1157                 &bounds,
1158                 SizedByDefault::No,
1159                 item.span,
1160                 assoc_name,
1161             )
1162         } else {
1163             <dyn AstConv<'_>>::compute_bounds(
1164                 &icx,
1165                 self_param_ty,
1166                 &bounds,
1167                 SizedByDefault::No,
1168                 item.span,
1169             )
1170         };
1171
1172         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1173
1174         // Convert any explicit superbounds in the where-clause,
1175         // e.g., `trait Foo where Self: Bar`.
1176         // In the case of trait aliases, however, we include all bounds in the where-clause,
1177         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1178         // as one of its "superpredicates".
1179         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1180         let superbounds2 = icx.type_parameter_bounds_in_generics(
1181             generics,
1182             item.hir_id(),
1183             self_param_ty,
1184             OnlySelfBounds(!is_trait_alias),
1185             assoc_name,
1186         );
1187
1188         // Combine the two lists to form the complete set of superbounds:
1189         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1190
1191         // Now require that immediate supertraits are converted,
1192         // which will, in turn, reach indirect supertraits.
1193         if assoc_name.is_none() {
1194             // Now require that immediate supertraits are converted,
1195             // which will, in turn, reach indirect supertraits.
1196             for &(pred, span) in superbounds {
1197                 debug!("superbound: {:?}", pred);
1198                 if let ty::PredicateKind::Trait(bound, _) = pred.kind().skip_binder() {
1199                     tcx.at(span).super_predicates_of(bound.def_id());
1200                 }
1201             }
1202         }
1203
1204         ty::GenericPredicates { parent: None, predicates: superbounds }
1205     } else {
1206         // if `assoc_name` is None, then the query should've been redirected to an
1207         // external provider
1208         assert!(assoc_name.is_some());
1209         tcx.super_predicates_of(trait_def_id)
1210     }
1211 }
1212
1213 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1214     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1215     let item = tcx.hir().expect_item(hir_id);
1216
1217     let (is_auto, unsafety) = match item.kind {
1218         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1219         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1220         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1221     };
1222
1223     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1224     if paren_sugar && !tcx.features().unboxed_closures {
1225         tcx.sess
1226             .struct_span_err(
1227                 item.span,
1228                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1229                  which traits can use parenthetical notation",
1230             )
1231             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1232             .emit();
1233     }
1234
1235     let is_marker = tcx.has_attr(def_id, sym::marker);
1236     let skip_array_during_method_dispatch =
1237         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1238     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1239         ty::trait_def::TraitSpecializationKind::Marker
1240     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1241         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1242     } else {
1243         ty::trait_def::TraitSpecializationKind::None
1244     };
1245     let def_path_hash = tcx.def_path_hash(def_id);
1246     ty::TraitDef::new(
1247         def_id,
1248         unsafety,
1249         paren_sugar,
1250         is_auto,
1251         is_marker,
1252         skip_array_during_method_dispatch,
1253         spec_kind,
1254         def_path_hash,
1255     )
1256 }
1257
1258 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1259     struct LateBoundRegionsDetector<'tcx> {
1260         tcx: TyCtxt<'tcx>,
1261         outer_index: ty::DebruijnIndex,
1262         has_late_bound_regions: Option<Span>,
1263     }
1264
1265     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1266         type Map = intravisit::ErasedMap<'tcx>;
1267
1268         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1269             NestedVisitorMap::None
1270         }
1271
1272         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1273             if self.has_late_bound_regions.is_some() {
1274                 return;
1275             }
1276             match ty.kind {
1277                 hir::TyKind::BareFn(..) => {
1278                     self.outer_index.shift_in(1);
1279                     intravisit::walk_ty(self, ty);
1280                     self.outer_index.shift_out(1);
1281                 }
1282                 _ => intravisit::walk_ty(self, ty),
1283             }
1284         }
1285
1286         fn visit_poly_trait_ref(
1287             &mut self,
1288             tr: &'tcx hir::PolyTraitRef<'tcx>,
1289             m: hir::TraitBoundModifier,
1290         ) {
1291             if self.has_late_bound_regions.is_some() {
1292                 return;
1293             }
1294             self.outer_index.shift_in(1);
1295             intravisit::walk_poly_trait_ref(self, tr, m);
1296             self.outer_index.shift_out(1);
1297         }
1298
1299         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1300             if self.has_late_bound_regions.is_some() {
1301                 return;
1302             }
1303
1304             match self.tcx.named_region(lt.hir_id) {
1305                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1306                 Some(
1307                     rl::Region::LateBound(debruijn, _, _, _)
1308                     | rl::Region::LateBoundAnon(debruijn, _, _),
1309                 ) if debruijn < self.outer_index => {}
1310                 Some(
1311                     rl::Region::LateBound(..)
1312                     | rl::Region::LateBoundAnon(..)
1313                     | rl::Region::Free(..),
1314                 )
1315                 | None => {
1316                     self.has_late_bound_regions = Some(lt.span);
1317                 }
1318             }
1319         }
1320     }
1321
1322     fn has_late_bound_regions<'tcx>(
1323         tcx: TyCtxt<'tcx>,
1324         generics: &'tcx hir::Generics<'tcx>,
1325         decl: &'tcx hir::FnDecl<'tcx>,
1326     ) -> Option<Span> {
1327         let mut visitor = LateBoundRegionsDetector {
1328             tcx,
1329             outer_index: ty::INNERMOST,
1330             has_late_bound_regions: None,
1331         };
1332         for param in generics.params {
1333             if let GenericParamKind::Lifetime { .. } = param.kind {
1334                 if tcx.is_late_bound(param.hir_id) {
1335                     return Some(param.span);
1336                 }
1337             }
1338         }
1339         visitor.visit_fn_decl(decl);
1340         visitor.has_late_bound_regions
1341     }
1342
1343     match node {
1344         Node::TraitItem(item) => match item.kind {
1345             hir::TraitItemKind::Fn(ref sig, _) => {
1346                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1347             }
1348             _ => None,
1349         },
1350         Node::ImplItem(item) => match item.kind {
1351             hir::ImplItemKind::Fn(ref sig, _) => {
1352                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1353             }
1354             _ => None,
1355         },
1356         Node::ForeignItem(item) => match item.kind {
1357             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1358                 has_late_bound_regions(tcx, generics, fn_decl)
1359             }
1360             _ => None,
1361         },
1362         Node::Item(item) => match item.kind {
1363             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1364                 has_late_bound_regions(tcx, generics, &sig.decl)
1365             }
1366             _ => None,
1367         },
1368         _ => None,
1369     }
1370 }
1371
1372 struct AnonConstInParamTyDetector {
1373     in_param_ty: bool,
1374     found_anon_const_in_param_ty: bool,
1375     ct: HirId,
1376 }
1377
1378 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1379     type Map = intravisit::ErasedMap<'v>;
1380
1381     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1382         NestedVisitorMap::None
1383     }
1384
1385     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1386         if let GenericParamKind::Const { ref ty, default: _ } = p.kind {
1387             let prev = self.in_param_ty;
1388             self.in_param_ty = true;
1389             self.visit_ty(ty);
1390             self.in_param_ty = prev;
1391         }
1392     }
1393
1394     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1395         if self.in_param_ty && self.ct == c.hir_id {
1396             self.found_anon_const_in_param_ty = true;
1397         } else {
1398             intravisit::walk_anon_const(self, c)
1399         }
1400     }
1401 }
1402
1403 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1404     use rustc_hir::*;
1405
1406     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1407
1408     let node = tcx.hir().get(hir_id);
1409     let parent_def_id = match node {
1410         Node::ImplItem(_)
1411         | Node::TraitItem(_)
1412         | Node::Variant(_)
1413         | Node::Ctor(..)
1414         | Node::Field(_) => {
1415             let parent_id = tcx.hir().get_parent_item(hir_id);
1416             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1417         }
1418         // FIXME(#43408) always enable this once `lazy_normalization` is
1419         // stable enough and does not need a feature gate anymore.
1420         Node::AnonConst(_) => {
1421             let parent_id = tcx.hir().get_parent_item(hir_id);
1422             let parent_def_id = tcx.hir().local_def_id(parent_id);
1423
1424             let mut in_param_ty = false;
1425             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1426                 if let Some(generics) = node.generics() {
1427                     let mut visitor = AnonConstInParamTyDetector {
1428                         in_param_ty: false,
1429                         found_anon_const_in_param_ty: false,
1430                         ct: hir_id,
1431                     };
1432
1433                     visitor.visit_generics(generics);
1434                     in_param_ty = visitor.found_anon_const_in_param_ty;
1435                     break;
1436                 }
1437             }
1438
1439             if in_param_ty {
1440                 // We do not allow generic parameters in anon consts if we are inside
1441                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1442                 None
1443             } else if tcx.lazy_normalization() {
1444                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1445                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1446                     //
1447                     // struct Foo<const N: usize = { .. }>;
1448                     //        ^^^       ^          ^^^^^^ def id of this anon const
1449                     //        ^         ^ param_id
1450                     //        ^ parent_def_id
1451                     //
1452                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1453                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1454                     //
1455                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1456                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1457                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1458                     //
1459                     // We fix this by having this function return the parent's generics ourselves and truncating the
1460                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1461                     //
1462                     // For the above code example that means we want `substs: []`
1463                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1464                     // the def id of the `{ N + 1 }` anon const
1465                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1466                     //
1467                     // This has some implications for how we get the predicates available to the anon const
1468                     // see `explicit_predicates_of` for more information on this
1469                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1470                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1471                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1472                     // In the above example this would be .params[..N#0]
1473                     let params = generics.params[..param_def_idx as usize].to_owned();
1474                     let param_def_id_to_index =
1475                         params.iter().map(|param| (param.def_id, param.index)).collect();
1476
1477                     return ty::Generics {
1478                         // we set the parent of these generics to be our parent's parent so that we
1479                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1480                         // struct Foo<const N: usize, const M: usize = { ... }>;
1481                         parent: generics.parent,
1482                         parent_count: generics.parent_count,
1483                         params,
1484                         param_def_id_to_index,
1485                         has_self: generics.has_self,
1486                         has_late_bound_regions: generics.has_late_bound_regions,
1487                     };
1488                 }
1489
1490                 // HACK(eddyb) this provides the correct generics when
1491                 // `feature(const_generics)` is enabled, so that const expressions
1492                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1493                 //
1494                 // Note that we do not supply the parent generics when using
1495                 // `min_const_generics`.
1496                 Some(parent_def_id.to_def_id())
1497             } else {
1498                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1499                 match parent_node {
1500                     // HACK(eddyb) this provides the correct generics for repeat
1501                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1502                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1503                     // as they shouldn't be able to cause query cycle errors.
1504                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1505                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1506                         if constant.hir_id == hir_id =>
1507                     {
1508                         Some(parent_def_id.to_def_id())
1509                     }
1510
1511                     _ => None,
1512                 }
1513             }
1514         }
1515         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1516             Some(tcx.closure_base_def_id(def_id))
1517         }
1518         Node::Item(item) => match item.kind {
1519             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1520                 impl_trait_fn.or_else(|| {
1521                     let parent_id = tcx.hir().get_parent_item(hir_id);
1522                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1523                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1524                     // Opaque types are always nested within another item, and
1525                     // inherit the generics of the item.
1526                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1527                 })
1528             }
1529             _ => None,
1530         },
1531         _ => None,
1532     };
1533
1534     let mut opt_self = None;
1535     let mut allow_defaults = false;
1536
1537     let no_generics = hir::Generics::empty();
1538     let ast_generics = match node {
1539         Node::TraitItem(item) => &item.generics,
1540
1541         Node::ImplItem(item) => &item.generics,
1542
1543         Node::Item(item) => {
1544             match item.kind {
1545                 ItemKind::Fn(.., ref generics, _)
1546                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1547
1548                 ItemKind::TyAlias(_, ref generics)
1549                 | ItemKind::Enum(_, ref generics)
1550                 | ItemKind::Struct(_, ref generics)
1551                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1552                 | ItemKind::Union(_, ref generics) => {
1553                     allow_defaults = true;
1554                     generics
1555                 }
1556
1557                 ItemKind::Trait(_, _, ref generics, ..)
1558                 | ItemKind::TraitAlias(ref generics, ..) => {
1559                     // Add in the self type parameter.
1560                     //
1561                     // Something of a hack: use the node id for the trait, also as
1562                     // the node id for the Self type parameter.
1563                     let param_id = item.def_id;
1564
1565                     opt_self = Some(ty::GenericParamDef {
1566                         index: 0,
1567                         name: kw::SelfUpper,
1568                         def_id: param_id.to_def_id(),
1569                         pure_wrt_drop: false,
1570                         kind: ty::GenericParamDefKind::Type {
1571                             has_default: false,
1572                             object_lifetime_default: rl::Set1::Empty,
1573                             synthetic: None,
1574                         },
1575                     });
1576
1577                     allow_defaults = true;
1578                     generics
1579                 }
1580
1581                 _ => &no_generics,
1582             }
1583         }
1584
1585         Node::ForeignItem(item) => match item.kind {
1586             ForeignItemKind::Static(..) => &no_generics,
1587             ForeignItemKind::Fn(_, _, ref generics) => generics,
1588             ForeignItemKind::Type => &no_generics,
1589         },
1590
1591         _ => &no_generics,
1592     };
1593
1594     let has_self = opt_self.is_some();
1595     let mut parent_has_self = false;
1596     let mut own_start = has_self as u32;
1597     let parent_count = parent_def_id.map_or(0, |def_id| {
1598         let generics = tcx.generics_of(def_id);
1599         assert_eq!(has_self, false);
1600         parent_has_self = generics.has_self;
1601         own_start = generics.count() as u32;
1602         generics.parent_count + generics.params.len()
1603     });
1604
1605     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1606
1607     if let Some(opt_self) = opt_self {
1608         params.push(opt_self);
1609     }
1610
1611     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1612     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1613         name: param.name.ident().name,
1614         index: own_start + i as u32,
1615         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1616         pure_wrt_drop: param.pure_wrt_drop,
1617         kind: ty::GenericParamDefKind::Lifetime,
1618     }));
1619
1620     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1621
1622     // Now create the real type and const parameters.
1623     let type_start = own_start - has_self as u32 + params.len() as u32;
1624     let mut i = 0;
1625
1626     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1627         GenericParamKind::Lifetime { .. } => None,
1628         GenericParamKind::Type { ref default, synthetic, .. } => {
1629             if !allow_defaults && default.is_some() {
1630                 if !tcx.features().default_type_parameter_fallback {
1631                     tcx.struct_span_lint_hir(
1632                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1633                         param.hir_id,
1634                         param.span,
1635                         |lint| {
1636                             lint.build(
1637                                 "defaults for type parameters are only allowed in \
1638                                  `struct`, `enum`, `type`, or `trait` definitions",
1639                             )
1640                             .emit();
1641                         },
1642                     );
1643                 }
1644             }
1645
1646             let kind = ty::GenericParamDefKind::Type {
1647                 has_default: default.is_some(),
1648                 object_lifetime_default: object_lifetime_defaults
1649                     .as_ref()
1650                     .map_or(rl::Set1::Empty, |o| o[i]),
1651                 synthetic,
1652             };
1653
1654             let param_def = ty::GenericParamDef {
1655                 index: type_start + i as u32,
1656                 name: param.name.ident().name,
1657                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1658                 pure_wrt_drop: param.pure_wrt_drop,
1659                 kind,
1660             };
1661             i += 1;
1662             Some(param_def)
1663         }
1664         GenericParamKind::Const { default, .. } => {
1665             if !allow_defaults && default.is_some() {
1666                 tcx.sess.span_err(
1667                     param.span,
1668                     "defaults for const parameters are only allowed in \
1669                     `struct`, `enum`, `type`, or `trait` definitions",
1670                 );
1671             }
1672
1673             let param_def = ty::GenericParamDef {
1674                 index: type_start + i as u32,
1675                 name: param.name.ident().name,
1676                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1677                 pure_wrt_drop: param.pure_wrt_drop,
1678                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1679             };
1680             i += 1;
1681             Some(param_def)
1682         }
1683     }));
1684
1685     // provide junk type parameter defs - the only place that
1686     // cares about anything but the length is instantiation,
1687     // and we don't do that for closures.
1688     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1689         let dummy_args = if gen.is_some() {
1690             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1691         } else {
1692             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1693         };
1694
1695         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1696             index: type_start + i as u32,
1697             name: Symbol::intern(arg),
1698             def_id,
1699             pure_wrt_drop: false,
1700             kind: ty::GenericParamDefKind::Type {
1701                 has_default: false,
1702                 object_lifetime_default: rl::Set1::Empty,
1703                 synthetic: None,
1704             },
1705         }));
1706     }
1707
1708     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1709
1710     ty::Generics {
1711         parent: parent_def_id,
1712         parent_count,
1713         params,
1714         param_def_id_to_index,
1715         has_self: has_self || parent_has_self,
1716         has_late_bound_regions: has_late_bound_regions(tcx, node),
1717     }
1718 }
1719
1720 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1721     generic_args
1722         .iter()
1723         .filter_map(|arg| match arg {
1724             hir::GenericArg::Type(ty) => Some(ty),
1725             _ => None,
1726         })
1727         .any(is_suggestable_infer_ty)
1728 }
1729
1730 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1731 /// use inference to provide suggestions for the appropriate type if possible.
1732 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1733     use hir::TyKind::*;
1734     match &ty.kind {
1735         Infer => true,
1736         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1737         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1738         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1739         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1740         Path(hir::QPath::TypeRelative(ty, segment)) => {
1741             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1742         }
1743         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1744             ty_opt.map_or(false, is_suggestable_infer_ty)
1745                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1746         }
1747         _ => false,
1748     }
1749 }
1750
1751 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1752     if let hir::FnRetTy::Return(ref ty) = output {
1753         if is_suggestable_infer_ty(ty) {
1754             return Some(&**ty);
1755         }
1756     }
1757     None
1758 }
1759
1760 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1761     use rustc_hir::Node::*;
1762     use rustc_hir::*;
1763
1764     let def_id = def_id.expect_local();
1765     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1766
1767     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1768
1769     match tcx.hir().get(hir_id) {
1770         TraitItem(hir::TraitItem {
1771             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1772             ident,
1773             generics,
1774             ..
1775         })
1776         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1777         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1778             match get_infer_ret_ty(&sig.decl.output) {
1779                 Some(ty) => {
1780                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1781                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1782                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1783                         ty::ReErased => tcx.lifetimes.re_static,
1784                         _ => r,
1785                     });
1786                     let fn_sig = ty::Binder::dummy(fn_sig);
1787
1788                     let mut visitor = PlaceholderHirTyCollector::default();
1789                     visitor.visit_ty(ty);
1790                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
1791                     let ret_ty = fn_sig.skip_binder().output();
1792                     if ret_ty != tcx.ty_error() {
1793                         if !ret_ty.is_closure() {
1794                             let ret_ty_str = match ret_ty.kind() {
1795                                 // Suggest a function pointer return type instead of a unique function definition
1796                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1797                                 // syntax)
1798                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1799                                 _ => ret_ty.to_string(),
1800                             };
1801                             diag.span_suggestion(
1802                                 ty.span,
1803                                 "replace with the correct return type",
1804                                 ret_ty_str,
1805                                 Applicability::MaybeIncorrect,
1806                             );
1807                         } else {
1808                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1809                             // to prevent the user from getting a papercut while trying to use the unique closure
1810                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1811                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1812                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1813                         }
1814                     }
1815                     diag.emit();
1816
1817                     fn_sig
1818                 }
1819                 None => <dyn AstConv<'_>>::ty_of_fn(
1820                     &icx,
1821                     hir_id,
1822                     sig.header.unsafety,
1823                     sig.header.abi,
1824                     &sig.decl,
1825                     &generics,
1826                     Some(ident.span),
1827                     None,
1828                 ),
1829             }
1830         }
1831
1832         TraitItem(hir::TraitItem {
1833             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1834             ident,
1835             generics,
1836             ..
1837         }) => <dyn AstConv<'_>>::ty_of_fn(
1838             &icx,
1839             hir_id,
1840             header.unsafety,
1841             header.abi,
1842             decl,
1843             &generics,
1844             Some(ident.span),
1845             None,
1846         ),
1847
1848         ForeignItem(&hir::ForeignItem {
1849             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1850             ident,
1851             ..
1852         }) => {
1853             let abi = tcx.hir().get_foreign_abi(hir_id);
1854             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1855         }
1856
1857         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1858             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1859             let inputs =
1860                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1861             ty::Binder::dummy(tcx.mk_fn_sig(
1862                 inputs,
1863                 ty,
1864                 false,
1865                 hir::Unsafety::Normal,
1866                 abi::Abi::Rust,
1867             ))
1868         }
1869
1870         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1871             // Closure signatures are not like other function
1872             // signatures and cannot be accessed through `fn_sig`. For
1873             // example, a closure signature excludes the `self`
1874             // argument. In any case they are embedded within the
1875             // closure type as part of the `ClosureSubsts`.
1876             //
1877             // To get the signature of a closure, you should use the
1878             // `sig` method on the `ClosureSubsts`:
1879             //
1880             //    substs.as_closure().sig(def_id, tcx)
1881             bug!(
1882                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1883             );
1884         }
1885
1886         x => {
1887             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1888         }
1889     }
1890 }
1891
1892 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1893     let icx = ItemCtxt::new(tcx, def_id);
1894
1895     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1896     match tcx.hir().expect_item(hir_id).kind {
1897         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1898             let selfty = tcx.type_of(def_id);
1899             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1900         }),
1901         _ => bug!(),
1902     }
1903 }
1904
1905 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1906     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1907     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1908     let item = tcx.hir().expect_item(hir_id);
1909     match &item.kind {
1910         hir::ItemKind::Impl(hir::Impl {
1911             polarity: hir::ImplPolarity::Negative(span),
1912             of_trait,
1913             ..
1914         }) => {
1915             if is_rustc_reservation {
1916                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1917                 tcx.sess.span_err(span, "reservation impls can't be negative");
1918             }
1919             ty::ImplPolarity::Negative
1920         }
1921         hir::ItemKind::Impl(hir::Impl {
1922             polarity: hir::ImplPolarity::Positive,
1923             of_trait: None,
1924             ..
1925         }) => {
1926             if is_rustc_reservation {
1927                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1928             }
1929             ty::ImplPolarity::Positive
1930         }
1931         hir::ItemKind::Impl(hir::Impl {
1932             polarity: hir::ImplPolarity::Positive,
1933             of_trait: Some(_),
1934             ..
1935         }) => {
1936             if is_rustc_reservation {
1937                 ty::ImplPolarity::Reservation
1938             } else {
1939                 ty::ImplPolarity::Positive
1940             }
1941         }
1942         item => bug!("impl_polarity: {:?} not an impl", item),
1943     }
1944 }
1945
1946 /// Returns the early-bound lifetimes declared in this generics
1947 /// listing. For anything other than fns/methods, this is just all
1948 /// the lifetimes that are declared. For fns or methods, we have to
1949 /// screen out those that do not appear in any where-clauses etc using
1950 /// `resolve_lifetime::early_bound_lifetimes`.
1951 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1952     tcx: TyCtxt<'tcx>,
1953     generics: &'a hir::Generics<'a>,
1954 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1955     generics.params.iter().filter(move |param| match param.kind {
1956         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1957         _ => false,
1958     })
1959 }
1960
1961 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1962 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1963 /// inferred constraints concerning which regions outlive other regions.
1964 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1965     debug!("predicates_defined_on({:?})", def_id);
1966     let mut result = tcx.explicit_predicates_of(def_id);
1967     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1968     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1969     if !inferred_outlives.is_empty() {
1970         debug!(
1971             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1972             def_id, inferred_outlives,
1973         );
1974         if result.predicates.is_empty() {
1975             result.predicates = inferred_outlives;
1976         } else {
1977             result.predicates = tcx
1978                 .arena
1979                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1980         }
1981     }
1982
1983     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1984     result
1985 }
1986
1987 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1988 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1989 /// `Self: Trait` predicates for traits.
1990 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1991     let mut result = tcx.predicates_defined_on(def_id);
1992
1993     if tcx.is_trait(def_id) {
1994         // For traits, add `Self: Trait` predicate. This is
1995         // not part of the predicates that a user writes, but it
1996         // is something that one must prove in order to invoke a
1997         // method or project an associated type.
1998         //
1999         // In the chalk setup, this predicate is not part of the
2000         // "predicates" for a trait item. But it is useful in
2001         // rustc because if you directly (e.g.) invoke a trait
2002         // method like `Trait::method(...)`, you must naturally
2003         // prove that the trait applies to the types that were
2004         // used, and adding the predicate into this list ensures
2005         // that this is done.
2006         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
2007         result.predicates =
2008             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2009                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2010                 span,
2011             ))));
2012     }
2013     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2014     result
2015 }
2016
2017 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2018 /// N.B., this does not include any implied/inferred constraints.
2019 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2020     use rustc_hir::*;
2021
2022     debug!("explicit_predicates_of(def_id={:?})", def_id);
2023
2024     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2025     let node = tcx.hir().get(hir_id);
2026
2027     let mut is_trait = None;
2028     let mut is_default_impl_trait = None;
2029
2030     let icx = ItemCtxt::new(tcx, def_id);
2031     let constness = icx.default_constness_for_trait_bounds();
2032
2033     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2034
2035     // We use an `IndexSet` to preserves order of insertion.
2036     // Preserving the order of insertion is important here so as not to break UI tests.
2037     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2038
2039     let ast_generics = match node {
2040         Node::TraitItem(item) => &item.generics,
2041
2042         Node::ImplItem(item) => &item.generics,
2043
2044         Node::Item(item) => {
2045             match item.kind {
2046                 ItemKind::Impl(ref impl_) => {
2047                     if impl_.defaultness.is_default() {
2048                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2049                     }
2050                     &impl_.generics
2051                 }
2052                 ItemKind::Fn(.., ref generics, _)
2053                 | ItemKind::TyAlias(_, ref generics)
2054                 | ItemKind::Enum(_, ref generics)
2055                 | ItemKind::Struct(_, ref generics)
2056                 | ItemKind::Union(_, ref generics) => generics,
2057
2058                 ItemKind::Trait(_, _, ref generics, ..) => {
2059                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2060                     generics
2061                 }
2062                 ItemKind::TraitAlias(ref generics, _) => {
2063                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2064                     generics
2065                 }
2066                 ItemKind::OpaqueTy(OpaqueTy {
2067                     bounds: _,
2068                     impl_trait_fn,
2069                     ref generics,
2070                     origin: _,
2071                 }) => {
2072                     if impl_trait_fn.is_some() {
2073                         // return-position impl trait
2074                         //
2075                         // We don't inherit predicates from the parent here:
2076                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2077                         // then the return type is `f::<'static, T>::{{opaque}}`.
2078                         //
2079                         // If we inherited the predicates of `f` then we would
2080                         // require that `T: 'static` to show that the return
2081                         // type is well-formed.
2082                         //
2083                         // The only way to have something with this opaque type
2084                         // is from the return type of the containing function,
2085                         // which will ensure that the function's predicates
2086                         // hold.
2087                         return ty::GenericPredicates { parent: None, predicates: &[] };
2088                     } else {
2089                         // type-alias impl trait
2090                         generics
2091                     }
2092                 }
2093
2094                 _ => NO_GENERICS,
2095             }
2096         }
2097
2098         Node::ForeignItem(item) => match item.kind {
2099             ForeignItemKind::Static(..) => NO_GENERICS,
2100             ForeignItemKind::Fn(_, _, ref generics) => generics,
2101             ForeignItemKind::Type => NO_GENERICS,
2102         },
2103
2104         _ => NO_GENERICS,
2105     };
2106
2107     let generics = tcx.generics_of(def_id);
2108     let parent_count = generics.parent_count as u32;
2109     let has_own_self = generics.has_self && parent_count == 0;
2110
2111     // Below we'll consider the bounds on the type parameters (including `Self`)
2112     // and the explicit where-clauses, but to get the full set of predicates
2113     // on a trait we need to add in the supertrait bounds and bounds found on
2114     // associated types.
2115     if let Some(_trait_ref) = is_trait {
2116         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2117     }
2118
2119     // In default impls, we can assume that the self type implements
2120     // the trait. So in:
2121     //
2122     //     default impl Foo for Bar { .. }
2123     //
2124     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2125     // (see below). Recall that a default impl is not itself an impl, but rather a
2126     // set of defaults that can be incorporated into another impl.
2127     if let Some(trait_ref) = is_default_impl_trait {
2128         predicates.insert((
2129             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
2130             tcx.def_span(def_id),
2131         ));
2132     }
2133
2134     // Collect the region predicates that were declared inline as
2135     // well. In the case of parameters declared on a fn or method, we
2136     // have to be careful to only iterate over early-bound regions.
2137     let mut index = parent_count + has_own_self as u32;
2138     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2139         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2140             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2141             index,
2142             name: param.name.ident().name,
2143         }));
2144         index += 1;
2145
2146         match param.kind {
2147             GenericParamKind::Lifetime { .. } => {
2148                 param.bounds.iter().for_each(|bound| match bound {
2149                     hir::GenericBound::Outlives(lt) => {
2150                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, &lt, None);
2151                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2152                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2153                     }
2154                     _ => bug!(),
2155                 });
2156             }
2157             _ => bug!(),
2158         }
2159     }
2160
2161     // Collect the predicates that were written inline by the user on each
2162     // type parameter (e.g., `<T: Foo>`).
2163     for param in ast_generics.params {
2164         match param.kind {
2165             // We already dealt with early bound lifetimes above.
2166             GenericParamKind::Lifetime { .. } => (),
2167             GenericParamKind::Type { .. } => {
2168                 let name = param.name.ident().name;
2169                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2170                 index += 1;
2171
2172                 let sized = SizedByDefault::Yes;
2173                 let bounds = <dyn AstConv<'_>>::compute_bounds(
2174                     &icx,
2175                     param_ty,
2176                     &param.bounds,
2177                     sized,
2178                     param.span,
2179                 );
2180                 predicates.extend(bounds.predicates(tcx, param_ty));
2181             }
2182             GenericParamKind::Const { .. } => {
2183                 // Bounds on const parameters are currently not possible.
2184                 debug_assert!(param.bounds.is_empty());
2185                 index += 1;
2186             }
2187         }
2188     }
2189
2190     // Add in the bounds that appear in the where-clause.
2191     let where_clause = &ast_generics.where_clause;
2192     for predicate in where_clause.predicates {
2193         match predicate {
2194             hir::WherePredicate::BoundPredicate(bound_pred) => {
2195                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2196                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2197
2198                 // Keep the type around in a dummy predicate, in case of no bounds.
2199                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2200                 // is still checked for WF.
2201                 if bound_pred.bounds.is_empty() {
2202                     if let ty::Param(_) = ty.kind() {
2203                         // This is a `where T:`, which can be in the HIR from the
2204                         // transformation that moves `?Sized` to `T`'s declaration.
2205                         // We can skip the predicate because type parameters are
2206                         // trivially WF, but also we *should*, to avoid exposing
2207                         // users who never wrote `where Type:,` themselves, to
2208                         // compiler/tooling bugs from not handling WF predicates.
2209                     } else {
2210                         let span = bound_pred.bounded_ty.span;
2211                         let re_root_empty = tcx.lifetimes.re_root_empty;
2212                         let predicate = ty::Binder::bind_with_vars(
2213                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2214                                 ty,
2215                                 re_root_empty,
2216                             )),
2217                             bound_vars,
2218                         );
2219                         predicates.insert((predicate.to_predicate(tcx), span));
2220                     }
2221                 }
2222
2223                 for bound in bound_pred.bounds.iter() {
2224                     match bound {
2225                         hir::GenericBound::Trait(poly_trait_ref, modifier) => {
2226                             let constness = match modifier {
2227                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2228                                 hir::TraitBoundModifier::None => constness,
2229                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
2230                             };
2231
2232                             let mut bounds = Bounds::default();
2233                             let _ = <dyn AstConv<'_>>::instantiate_poly_trait_ref(
2234                                 &icx,
2235                                 &poly_trait_ref.trait_ref,
2236                                 poly_trait_ref.span,
2237                                 constness,
2238                                 ty,
2239                                 &mut bounds,
2240                                 false,
2241                             );
2242                             predicates.extend(bounds.predicates(tcx, ty));
2243                         }
2244
2245                         &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2246                             let mut bounds = Bounds::default();
2247                             <dyn AstConv<'_>>::instantiate_lang_item_trait_ref(
2248                                 &icx,
2249                                 lang_item,
2250                                 span,
2251                                 hir_id,
2252                                 args,
2253                                 ty,
2254                                 &mut bounds,
2255                             );
2256                             predicates.extend(bounds.predicates(tcx, ty));
2257                         }
2258
2259                         hir::GenericBound::Outlives(lifetime) => {
2260                             let region =
2261                                 <dyn AstConv<'_>>::ast_region_to_region(&icx, lifetime, None);
2262                             predicates.insert((
2263                                 ty::Binder::bind_with_vars(
2264                                     ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2265                                         ty, region,
2266                                     )),
2267                                     bound_vars,
2268                                 )
2269                                 .to_predicate(tcx),
2270                                 lifetime.span,
2271                             ));
2272                         }
2273                     }
2274                 }
2275             }
2276
2277             hir::WherePredicate::RegionPredicate(region_pred) => {
2278                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2279                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2280                     let (r2, span) = match bound {
2281                         hir::GenericBound::Outlives(lt) => {
2282                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2283                         }
2284                         _ => bug!(),
2285                     };
2286                     let pred = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
2287                         .to_predicate(icx.tcx);
2288
2289                     (pred, span)
2290                 }))
2291             }
2292
2293             hir::WherePredicate::EqPredicate(..) => {
2294                 // FIXME(#20041)
2295             }
2296         }
2297     }
2298
2299     if tcx.features().const_evaluatable_checked {
2300         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2301     }
2302
2303     let mut predicates: Vec<_> = predicates.into_iter().collect();
2304
2305     // Subtle: before we store the predicates into the tcx, we
2306     // sort them so that predicates like `T: Foo<Item=U>` come
2307     // before uses of `U`.  This avoids false ambiguity errors
2308     // in trait checking. See `setup_constraining_predicates`
2309     // for details.
2310     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2311         let self_ty = tcx.type_of(def_id);
2312         let trait_ref = tcx.impl_trait_ref(def_id);
2313         cgp::setup_constraining_predicates(
2314             tcx,
2315             &mut predicates,
2316             trait_ref,
2317             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2318         );
2319     }
2320
2321     let result = ty::GenericPredicates {
2322         parent: generics.parent,
2323         predicates: tcx.arena.alloc_from_iter(predicates),
2324     };
2325     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2326     result
2327 }
2328
2329 fn const_evaluatable_predicates_of<'tcx>(
2330     tcx: TyCtxt<'tcx>,
2331     def_id: LocalDefId,
2332 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2333     struct ConstCollector<'tcx> {
2334         tcx: TyCtxt<'tcx>,
2335         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2336     }
2337
2338     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2339         type Map = Map<'tcx>;
2340
2341         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2342             intravisit::NestedVisitorMap::None
2343         }
2344
2345         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2346             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2347             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2348             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2349                 assert_eq!(uv.promoted, None);
2350                 let span = self.tcx.hir().span(c.hir_id);
2351                 self.preds.insert((
2352                     ty::PredicateKind::ConstEvaluatable(uv.def, uv.substs).to_predicate(self.tcx),
2353                     span,
2354                 ));
2355             }
2356         }
2357
2358         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2359             // Do not look into const param defaults,
2360             // these get checked when they are actually instantiated.
2361             //
2362             // We do not want the following to error:
2363             //
2364             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2365             //     struct Bar<const N: usize>(Foo<N, 3>);
2366         }
2367     }
2368
2369     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2370     let node = tcx.hir().get(hir_id);
2371
2372     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2373     if let hir::Node::Item(item) = node {
2374         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2375             if let Some(of_trait) = &impl_.of_trait {
2376                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2377                 collector.visit_trait_ref(of_trait);
2378             }
2379
2380             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2381             collector.visit_ty(impl_.self_ty);
2382         }
2383     }
2384
2385     if let Some(generics) = node.generics() {
2386         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2387         collector.visit_generics(generics);
2388     }
2389
2390     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2391         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2392         collector.visit_fn_decl(fn_sig.decl);
2393     }
2394     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2395
2396     collector.preds
2397 }
2398
2399 fn trait_explicit_predicates_and_bounds(
2400     tcx: TyCtxt<'_>,
2401     def_id: LocalDefId,
2402 ) -> ty::GenericPredicates<'_> {
2403     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2404     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2405 }
2406
2407 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2408     let def_kind = tcx.def_kind(def_id);
2409     if let DefKind::Trait = def_kind {
2410         // Remove bounds on associated types from the predicates, they will be
2411         // returned by `explicit_item_bounds`.
2412         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2413         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2414
2415         let is_assoc_item_ty = |ty: Ty<'_>| {
2416             // For a predicate from a where clause to become a bound on an
2417             // associated type:
2418             // * It must use the identity substs of the item.
2419             //     * Since any generic parameters on the item are not in scope,
2420             //       this means that the item is not a GAT, and its identity
2421             //       substs are the same as the trait's.
2422             // * It must be an associated type for this trait (*not* a
2423             //   supertrait).
2424             if let ty::Projection(projection) = ty.kind() {
2425                 projection.substs == trait_identity_substs
2426                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2427             } else {
2428                 false
2429             }
2430         };
2431
2432         let predicates: Vec<_> = predicates_and_bounds
2433             .predicates
2434             .iter()
2435             .copied()
2436             .filter(|(pred, _)| match pred.kind().skip_binder() {
2437                 ty::PredicateKind::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
2438                 ty::PredicateKind::Projection(proj) => {
2439                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2440                 }
2441                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2442                 _ => true,
2443             })
2444             .collect();
2445         if predicates.len() == predicates_and_bounds.predicates.len() {
2446             predicates_and_bounds
2447         } else {
2448             ty::GenericPredicates {
2449                 parent: predicates_and_bounds.parent,
2450                 predicates: tcx.arena.alloc_slice(&predicates),
2451             }
2452         }
2453     } else {
2454         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2455             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2456             if let Some(_) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
2457                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2458                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2459                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2460                 //
2461                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2462                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2463                 //        ^^^                                             explicit_predicates_of on
2464                 //        parent item we dont have set as the
2465                 //        parent of generics returned by `generics_of`
2466                 //
2467                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2468                 let item_id = tcx.hir().get_parent_item(hir_id);
2469                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2470                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2471                 return tcx.explicit_predicates_of(item_def_id);
2472             }
2473         }
2474         gather_explicit_predicates_of(tcx, def_id)
2475     }
2476 }
2477
2478 /// Converts a specific `GenericBound` from the AST into a set of
2479 /// predicates that apply to the self type. A vector is returned
2480 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2481 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2482 /// and `<T as Bar>::X == i32`).
2483 fn predicates_from_bound<'tcx>(
2484     astconv: &dyn AstConv<'tcx>,
2485     param_ty: Ty<'tcx>,
2486     bound: &'tcx hir::GenericBound<'tcx>,
2487     constness: hir::Constness,
2488 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2489     match *bound {
2490         hir::GenericBound::Trait(ref tr, modifier) => {
2491             let constness = match modifier {
2492                 hir::TraitBoundModifier::Maybe => return vec![],
2493                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2494                 hir::TraitBoundModifier::None => constness,
2495             };
2496
2497             let mut bounds = Bounds::default();
2498             let _ = astconv.instantiate_poly_trait_ref(
2499                 &tr.trait_ref,
2500                 tr.span,
2501                 constness,
2502                 param_ty,
2503                 &mut bounds,
2504                 false,
2505             );
2506             bounds.predicates(astconv.tcx(), param_ty)
2507         }
2508         hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2509             let mut bounds = Bounds::default();
2510             astconv.instantiate_lang_item_trait_ref(
2511                 lang_item,
2512                 span,
2513                 hir_id,
2514                 args,
2515                 param_ty,
2516                 &mut bounds,
2517             );
2518             bounds.predicates(astconv.tcx(), param_ty)
2519         }
2520         hir::GenericBound::Outlives(ref lifetime) => {
2521             let region = astconv.ast_region_to_region(lifetime, None);
2522             let pred = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2523                 .to_predicate(astconv.tcx());
2524             vec![(pred, lifetime.span)]
2525         }
2526     }
2527 }
2528
2529 fn compute_sig_of_foreign_fn_decl<'tcx>(
2530     tcx: TyCtxt<'tcx>,
2531     def_id: DefId,
2532     decl: &'tcx hir::FnDecl<'tcx>,
2533     abi: abi::Abi,
2534     ident: Ident,
2535 ) -> ty::PolyFnSig<'tcx> {
2536     let unsafety = if abi == abi::Abi::RustIntrinsic {
2537         intrinsic_operation_unsafety(tcx.item_name(def_id))
2538     } else {
2539         hir::Unsafety::Unsafe
2540     };
2541     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2542     let fty = <dyn AstConv<'_>>::ty_of_fn(
2543         &ItemCtxt::new(tcx, def_id),
2544         hir_id,
2545         unsafety,
2546         abi,
2547         decl,
2548         &hir::Generics::empty(),
2549         Some(ident.span),
2550         None,
2551     );
2552
2553     // Feature gate SIMD types in FFI, since I am not sure that the
2554     // ABIs are handled at all correctly. -huonw
2555     if abi != abi::Abi::RustIntrinsic
2556         && abi != abi::Abi::PlatformIntrinsic
2557         && !tcx.features().simd_ffi
2558     {
2559         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2560             if ty.is_simd() {
2561                 let snip = tcx
2562                     .sess
2563                     .source_map()
2564                     .span_to_snippet(ast_ty.span)
2565                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2566                 tcx.sess
2567                     .struct_span_err(
2568                         ast_ty.span,
2569                         &format!(
2570                             "use of SIMD type{} in FFI is highly experimental and \
2571                              may result in invalid code",
2572                             snip
2573                         ),
2574                     )
2575                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2576                     .emit();
2577             }
2578         };
2579         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2580             check(&input, ty)
2581         }
2582         if let hir::FnRetTy::Return(ref ty) = decl.output {
2583             check(&ty, fty.output().skip_binder())
2584         }
2585     }
2586
2587     fty
2588 }
2589
2590 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2591     match tcx.hir().get_if_local(def_id) {
2592         Some(Node::ForeignItem(..)) => true,
2593         Some(_) => false,
2594         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2595     }
2596 }
2597
2598 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2599     match tcx.hir().get_if_local(def_id) {
2600         Some(
2601             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2602             | Node::ForeignItem(&hir::ForeignItem {
2603                 kind: hir::ForeignItemKind::Static(_, mutbl),
2604                 ..
2605             }),
2606         ) => Some(mutbl),
2607         Some(_) => None,
2608         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2609     }
2610 }
2611
2612 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2613     match tcx.hir().get_if_local(def_id) {
2614         Some(Node::Expr(&rustc_hir::Expr {
2615             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2616             ..
2617         })) => tcx.hir().body(body_id).generator_kind(),
2618         Some(_) => None,
2619         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2620     }
2621 }
2622
2623 fn from_target_feature(
2624     tcx: TyCtxt<'_>,
2625     id: DefId,
2626     attr: &ast::Attribute,
2627     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2628     target_features: &mut Vec<Symbol>,
2629 ) {
2630     let list = match attr.meta_item_list() {
2631         Some(list) => list,
2632         None => return,
2633     };
2634     let bad_item = |span| {
2635         let msg = "malformed `target_feature` attribute input";
2636         let code = "enable = \"..\"".to_owned();
2637         tcx.sess
2638             .struct_span_err(span, &msg)
2639             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2640             .emit();
2641     };
2642     let rust_features = tcx.features();
2643     for item in list {
2644         // Only `enable = ...` is accepted in the meta-item list.
2645         if !item.has_name(sym::enable) {
2646             bad_item(item.span());
2647             continue;
2648         }
2649
2650         // Must be of the form `enable = "..."` (a string).
2651         let value = match item.value_str() {
2652             Some(value) => value,
2653             None => {
2654                 bad_item(item.span());
2655                 continue;
2656             }
2657         };
2658
2659         // We allow comma separation to enable multiple features.
2660         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2661             let feature_gate = match supported_target_features.get(feature) {
2662                 Some(g) => g,
2663                 None => {
2664                     let msg =
2665                         format!("the feature named `{}` is not valid for this target", feature);
2666                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2667                     err.span_label(
2668                         item.span(),
2669                         format!("`{}` is not valid for this target", feature),
2670                     );
2671                     if let Some(stripped) = feature.strip_prefix('+') {
2672                         let valid = supported_target_features.contains_key(stripped);
2673                         if valid {
2674                             err.help("consider removing the leading `+` in the feature name");
2675                         }
2676                     }
2677                     err.emit();
2678                     return None;
2679                 }
2680             };
2681
2682             // Only allow features whose feature gates have been enabled.
2683             let allowed = match feature_gate.as_ref().copied() {
2684                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2685                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2686                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2687                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2688                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2689                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2690                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2691                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2692                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2693                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2694                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2695                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2696                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2697                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2698                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2699                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2700                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2701                 Some(name) => bug!("unknown target feature gate {}", name),
2702                 None => true,
2703             };
2704             if !allowed && id.is_local() {
2705                 feature_err(
2706                     &tcx.sess.parse_sess,
2707                     feature_gate.unwrap(),
2708                     item.span(),
2709                     &format!("the target feature `{}` is currently unstable", feature),
2710                 )
2711                 .emit();
2712             }
2713             Some(Symbol::intern(feature))
2714         }));
2715     }
2716 }
2717
2718 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2719     use rustc_middle::mir::mono::Linkage::*;
2720
2721     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2722     // applicable to variable declarations and may not really make sense for
2723     // Rust code in the first place but allow them anyway and trust that the
2724     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2725     // up in the future.
2726     //
2727     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2728     // and don't have to be, LLVM treats them as no-ops.
2729     match name {
2730         "appending" => Appending,
2731         "available_externally" => AvailableExternally,
2732         "common" => Common,
2733         "extern_weak" => ExternalWeak,
2734         "external" => External,
2735         "internal" => Internal,
2736         "linkonce" => LinkOnceAny,
2737         "linkonce_odr" => LinkOnceODR,
2738         "private" => Private,
2739         "weak" => WeakAny,
2740         "weak_odr" => WeakODR,
2741         _ => {
2742             let span = tcx.hir().span_if_local(def_id);
2743             if let Some(span) = span {
2744                 tcx.sess.span_fatal(span, "invalid linkage specified")
2745             } else {
2746                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2747             }
2748         }
2749     }
2750 }
2751
2752 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2753     let attrs = tcx.get_attrs(id);
2754
2755     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2756     if should_inherit_track_caller(tcx, id) {
2757         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2758     }
2759
2760     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2761
2762     let mut inline_span = None;
2763     let mut link_ordinal_span = None;
2764     let mut no_sanitize_span = None;
2765     for attr in attrs.iter() {
2766         if tcx.sess.check_name(attr, sym::cold) {
2767             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2768         } else if tcx.sess.check_name(attr, sym::rustc_allocator) {
2769             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2770         } else if tcx.sess.check_name(attr, sym::unwind) {
2771             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2772         } else if tcx.sess.check_name(attr, sym::ffi_returns_twice) {
2773             if tcx.is_foreign_item(id) {
2774                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2775             } else {
2776                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2777                 struct_span_err!(
2778                     tcx.sess,
2779                     attr.span,
2780                     E0724,
2781                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2782                 )
2783                 .emit();
2784             }
2785         } else if tcx.sess.check_name(attr, sym::ffi_pure) {
2786             if tcx.is_foreign_item(id) {
2787                 if attrs.iter().any(|a| tcx.sess.check_name(a, sym::ffi_const)) {
2788                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2789                     struct_span_err!(
2790                         tcx.sess,
2791                         attr.span,
2792                         E0757,
2793                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2794                     )
2795                     .emit();
2796                 } else {
2797                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2798                 }
2799             } else {
2800                 // `#[ffi_pure]` is only allowed on foreign functions
2801                 struct_span_err!(
2802                     tcx.sess,
2803                     attr.span,
2804                     E0755,
2805                     "`#[ffi_pure]` may only be used on foreign functions"
2806                 )
2807                 .emit();
2808             }
2809         } else if tcx.sess.check_name(attr, sym::ffi_const) {
2810             if tcx.is_foreign_item(id) {
2811                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2812             } else {
2813                 // `#[ffi_const]` is only allowed on foreign functions
2814                 struct_span_err!(
2815                     tcx.sess,
2816                     attr.span,
2817                     E0756,
2818                     "`#[ffi_const]` may only be used on foreign functions"
2819                 )
2820                 .emit();
2821             }
2822         } else if tcx.sess.check_name(attr, sym::rustc_allocator_nounwind) {
2823             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2824         } else if tcx.sess.check_name(attr, sym::naked) {
2825             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2826         } else if tcx.sess.check_name(attr, sym::no_mangle) {
2827             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2828         } else if tcx.sess.check_name(attr, sym::no_coverage) {
2829             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2830         } else if tcx.sess.check_name(attr, sym::rustc_std_internal_symbol) {
2831             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2832         } else if tcx.sess.check_name(attr, sym::used) {
2833             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2834         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
2835             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2836                 struct_span_err!(
2837                     tcx.sess,
2838                     attr.span,
2839                     E0776,
2840                     "`#[cmse_nonsecure_entry]` requires C ABI"
2841                 )
2842                 .emit();
2843             }
2844             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2845                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2846                     .emit();
2847             }
2848             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2849         } else if tcx.sess.check_name(attr, sym::thread_local) {
2850             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2851         } else if tcx.sess.check_name(attr, sym::track_caller) {
2852             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2853                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2854                     .emit();
2855             }
2856             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2857         } else if tcx.sess.check_name(attr, sym::export_name) {
2858             if let Some(s) = attr.value_str() {
2859                 if s.as_str().contains('\0') {
2860                     // `#[export_name = ...]` will be converted to a null-terminated string,
2861                     // so it may not contain any null characters.
2862                     struct_span_err!(
2863                         tcx.sess,
2864                         attr.span,
2865                         E0648,
2866                         "`export_name` may not contain null characters"
2867                     )
2868                     .emit();
2869                 }
2870                 codegen_fn_attrs.export_name = Some(s);
2871             }
2872         } else if tcx.sess.check_name(attr, sym::target_feature) {
2873             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2874                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2875                     // The `#[target_feature]` attribute is allowed on
2876                     // WebAssembly targets on all functions, including safe
2877                     // ones. Other targets require that `#[target_feature]` is
2878                     // only applied to unsafe funtions (pending the
2879                     // `target_feature_11` feature) because on most targets
2880                     // execution of instructions that are not supported is
2881                     // considered undefined behavior. For WebAssembly which is a
2882                     // 100% safe target at execution time it's not possible to
2883                     // execute undefined instructions, and even if a future
2884                     // feature was added in some form for this it would be a
2885                     // deterministic trap. There is no undefined behavior when
2886                     // executing WebAssembly so `#[target_feature]` is allowed
2887                     // on safe functions (but again, only for WebAssembly)
2888                     //
2889                     // Note that this is also allowed if `actually_rustdoc` so
2890                     // if a target is documenting some wasm-specific code then
2891                     // it's not spuriously denied.
2892                 } else if !tcx.features().target_feature_11 {
2893                     let mut err = feature_err(
2894                         &tcx.sess.parse_sess,
2895                         sym::target_feature_11,
2896                         attr.span,
2897                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2898                     );
2899                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2900                     err.emit();
2901                 } else if let Some(local_id) = id.as_local() {
2902                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2903                 }
2904             }
2905             from_target_feature(
2906                 tcx,
2907                 id,
2908                 attr,
2909                 &supported_target_features,
2910                 &mut codegen_fn_attrs.target_features,
2911             );
2912         } else if tcx.sess.check_name(attr, sym::linkage) {
2913             if let Some(val) = attr.value_str() {
2914                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2915             }
2916         } else if tcx.sess.check_name(attr, sym::link_section) {
2917             if let Some(val) = attr.value_str() {
2918                 if val.as_str().bytes().any(|b| b == 0) {
2919                     let msg = format!(
2920                         "illegal null byte in link_section \
2921                          value: `{}`",
2922                         &val
2923                     );
2924                     tcx.sess.span_err(attr.span, &msg);
2925                 } else {
2926                     codegen_fn_attrs.link_section = Some(val);
2927                 }
2928             }
2929         } else if tcx.sess.check_name(attr, sym::link_name) {
2930             codegen_fn_attrs.link_name = attr.value_str();
2931         } else if tcx.sess.check_name(attr, sym::link_ordinal) {
2932             link_ordinal_span = Some(attr.span);
2933             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2934                 codegen_fn_attrs.link_ordinal = ordinal;
2935             }
2936         } else if tcx.sess.check_name(attr, sym::no_sanitize) {
2937             no_sanitize_span = Some(attr.span);
2938             if let Some(list) = attr.meta_item_list() {
2939                 for item in list.iter() {
2940                     if item.has_name(sym::address) {
2941                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2942                     } else if item.has_name(sym::memory) {
2943                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2944                     } else if item.has_name(sym::thread) {
2945                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2946                     } else if item.has_name(sym::hwaddress) {
2947                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2948                     } else {
2949                         tcx.sess
2950                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2951                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2952                             .emit();
2953                     }
2954                 }
2955             }
2956         } else if tcx.sess.check_name(attr, sym::instruction_set) {
2957             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2958                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2959                     [NestedMetaItem::MetaItem(set)] => {
2960                         let segments =
2961                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2962                         match segments.as_slice() {
2963                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2964                                 if !tcx.sess.target.has_thumb_interworking {
2965                                     struct_span_err!(
2966                                         tcx.sess.diagnostic(),
2967                                         attr.span,
2968                                         E0779,
2969                                         "target does not support `#[instruction_set]`"
2970                                     )
2971                                     .emit();
2972                                     None
2973                                 } else if segments[1] == sym::a32 {
2974                                     Some(InstructionSetAttr::ArmA32)
2975                                 } else if segments[1] == sym::t32 {
2976                                     Some(InstructionSetAttr::ArmT32)
2977                                 } else {
2978                                     unreachable!()
2979                                 }
2980                             }
2981                             _ => {
2982                                 struct_span_err!(
2983                                     tcx.sess.diagnostic(),
2984                                     attr.span,
2985                                     E0779,
2986                                     "invalid instruction set specified",
2987                                 )
2988                                 .emit();
2989                                 None
2990                             }
2991                         }
2992                     }
2993                     [] => {
2994                         struct_span_err!(
2995                             tcx.sess.diagnostic(),
2996                             attr.span,
2997                             E0778,
2998                             "`#[instruction_set]` requires an argument"
2999                         )
3000                         .emit();
3001                         None
3002                     }
3003                     _ => {
3004                         struct_span_err!(
3005                             tcx.sess.diagnostic(),
3006                             attr.span,
3007                             E0779,
3008                             "cannot specify more than one instruction set"
3009                         )
3010                         .emit();
3011                         None
3012                     }
3013                 },
3014                 _ => {
3015                     struct_span_err!(
3016                         tcx.sess.diagnostic(),
3017                         attr.span,
3018                         E0778,
3019                         "must specify an instruction set"
3020                     )
3021                     .emit();
3022                     None
3023                 }
3024             };
3025         } else if tcx.sess.check_name(attr, sym::repr) {
3026             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3027                 Some(items) => match items.as_slice() {
3028                     [item] => match item.name_value_literal() {
3029                         Some((sym::align, literal)) => {
3030                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3031
3032                             match alignment {
3033                                 Ok(align) => Some(align),
3034                                 Err(msg) => {
3035                                     struct_span_err!(
3036                                         tcx.sess.diagnostic(),
3037                                         attr.span,
3038                                         E0589,
3039                                         "invalid `repr(align)` attribute: {}",
3040                                         msg
3041                                     )
3042                                     .emit();
3043
3044                                     None
3045                                 }
3046                             }
3047                         }
3048                         _ => None,
3049                     },
3050                     [] => None,
3051                     _ => None,
3052                 },
3053                 None => None,
3054             };
3055         }
3056     }
3057
3058     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3059         if !attr.has_name(sym::inline) {
3060             return ia;
3061         }
3062         match attr.meta().map(|i| i.kind) {
3063             Some(MetaItemKind::Word) => {
3064                 tcx.sess.mark_attr_used(attr);
3065                 InlineAttr::Hint
3066             }
3067             Some(MetaItemKind::List(ref items)) => {
3068                 tcx.sess.mark_attr_used(attr);
3069                 inline_span = Some(attr.span);
3070                 if items.len() != 1 {
3071                     struct_span_err!(
3072                         tcx.sess.diagnostic(),
3073                         attr.span,
3074                         E0534,
3075                         "expected one argument"
3076                     )
3077                     .emit();
3078                     InlineAttr::None
3079                 } else if list_contains_name(&items[..], sym::always) {
3080                     InlineAttr::Always
3081                 } else if list_contains_name(&items[..], sym::never) {
3082                     InlineAttr::Never
3083                 } else {
3084                     struct_span_err!(
3085                         tcx.sess.diagnostic(),
3086                         items[0].span(),
3087                         E0535,
3088                         "invalid argument"
3089                     )
3090                     .emit();
3091
3092                     InlineAttr::None
3093                 }
3094             }
3095             Some(MetaItemKind::NameValue(_)) => ia,
3096             None => ia,
3097         }
3098     });
3099
3100     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3101         if !attr.has_name(sym::optimize) {
3102             return ia;
3103         }
3104         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3105         match attr.meta().map(|i| i.kind) {
3106             Some(MetaItemKind::Word) => {
3107                 err(attr.span, "expected one argument");
3108                 ia
3109             }
3110             Some(MetaItemKind::List(ref items)) => {
3111                 tcx.sess.mark_attr_used(attr);
3112                 inline_span = Some(attr.span);
3113                 if items.len() != 1 {
3114                     err(attr.span, "expected one argument");
3115                     OptimizeAttr::None
3116                 } else if list_contains_name(&items[..], sym::size) {
3117                     OptimizeAttr::Size
3118                 } else if list_contains_name(&items[..], sym::speed) {
3119                     OptimizeAttr::Speed
3120                 } else {
3121                     err(items[0].span(), "invalid argument");
3122                     OptimizeAttr::None
3123                 }
3124             }
3125             Some(MetaItemKind::NameValue(_)) => ia,
3126             None => ia,
3127         }
3128     });
3129
3130     // #73631: closures inherit `#[target_feature]` annotations
3131     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3132         let owner_id = tcx.parent(id).expect("closure should have a parent");
3133         codegen_fn_attrs
3134             .target_features
3135             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3136     }
3137
3138     // If a function uses #[target_feature] it can't be inlined into general
3139     // purpose functions as they wouldn't have the right target features
3140     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3141     // respected.
3142     if !codegen_fn_attrs.target_features.is_empty() {
3143         if codegen_fn_attrs.inline == InlineAttr::Always {
3144             if let Some(span) = inline_span {
3145                 tcx.sess.span_err(
3146                     span,
3147                     "cannot use `#[inline(always)]` with \
3148                      `#[target_feature]`",
3149                 );
3150             }
3151         }
3152     }
3153
3154     if !codegen_fn_attrs.no_sanitize.is_empty() {
3155         if codegen_fn_attrs.inline == InlineAttr::Always {
3156             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3157                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3158                 tcx.struct_span_lint_hir(
3159                     lint::builtin::INLINE_NO_SANITIZE,
3160                     hir_id,
3161                     no_sanitize_span,
3162                     |lint| {
3163                         lint.build("`no_sanitize` will have no effect after inlining")
3164                             .span_note(inline_span, "inlining requested here")
3165                             .emit();
3166                     },
3167                 )
3168             }
3169         }
3170     }
3171
3172     // Weak lang items have the same semantics as "std internal" symbols in the
3173     // sense that they're preserved through all our LTO passes and only
3174     // strippable by the linker.
3175     //
3176     // Additionally weak lang items have predetermined symbol names.
3177     if tcx.is_weak_lang_item(id) {
3178         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3179     }
3180     let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
3181     if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
3182         codegen_fn_attrs.export_name = Some(name);
3183         codegen_fn_attrs.link_name = Some(name);
3184     }
3185     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3186
3187     // Internal symbols to the standard library all have no_mangle semantics in
3188     // that they have defined symbol names present in the function name. This
3189     // also applies to weak symbols where they all have known symbol names.
3190     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3191         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3192     }
3193
3194     codegen_fn_attrs
3195 }
3196
3197 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3198 /// applied to the method prototype.
3199 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3200     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3201         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3202             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3203                 if let Some(trait_item) = tcx
3204                     .associated_items(trait_def_id)
3205                     .filter_by_name_unhygienic(impl_item.ident.name)
3206                     .find(move |trait_item| {
3207                         trait_item.kind == ty::AssocKind::Fn
3208                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3209                     })
3210                 {
3211                     return tcx
3212                         .codegen_fn_attrs(trait_item.def_id)
3213                         .flags
3214                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3215                 }
3216             }
3217         }
3218     }
3219
3220     false
3221 }
3222
3223 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
3224     use rustc_ast::{Lit, LitIntType, LitKind};
3225     let meta_item_list = attr.meta_item_list();
3226     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3227     let sole_meta_list = match meta_item_list {
3228         Some([item]) => item.literal(),
3229         _ => None,
3230     };
3231     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3232         if *ordinal <= usize::MAX as u128 {
3233             Some(*ordinal as usize)
3234         } else {
3235             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3236             tcx.sess
3237                 .struct_span_err(attr.span, &msg)
3238                 .note("the value may not exceed `usize::MAX`")
3239                 .emit();
3240             None
3241         }
3242     } else {
3243         tcx.sess
3244             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3245             .note("an unsuffixed integer value, e.g., `1`, is expected")
3246             .emit();
3247         None
3248     }
3249 }
3250
3251 fn check_link_name_xor_ordinal(
3252     tcx: TyCtxt<'_>,
3253     codegen_fn_attrs: &CodegenFnAttrs,
3254     inline_span: Option<Span>,
3255 ) {
3256     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3257         return;
3258     }
3259     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3260     if let Some(span) = inline_span {
3261         tcx.sess.span_err(span, msg);
3262     } else {
3263         tcx.sess.err(msg);
3264     }
3265 }
3266
3267 /// Checks the function annotated with `#[target_feature]` is not a safe
3268 /// trait method implementation, reporting an error if it is.
3269 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3270     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3271     let node = tcx.hir().get(hir_id);
3272     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3273         let parent_id = tcx.hir().get_parent_item(hir_id);
3274         let parent_item = tcx.hir().expect_item(parent_id);
3275         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3276             tcx.sess
3277                 .struct_span_err(
3278                     attr_span,
3279                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3280                 )
3281                 .span_label(attr_span, "cannot be applied to safe trait method")
3282                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3283                 .emit();
3284         }
3285     }
3286 }