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