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::Map;
  39 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  40 use rustc_middle::mir::mono::Linkage;
  41 use rustc_middle::ty::query::Providers;
  42 use rustc_middle::ty::subst::InternalSubsts;
  43 use rustc_middle::ty::util::Discr;
  44 use rustc_middle::ty::util::IntTypeExt;
  45 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  46 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
  47 use rustc_session::lint;
  48 use rustc_session::parse::feature_err;
  49 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  50 use rustc_span::{Span, DUMMY_SP};
  51 use rustc_target::spec::{abi, SanitizerSet};
  52 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  53 use std::iter;
  54
  55 mod item_bounds;
  56 mod type_of;
  57
  58 struct OnlySelfBounds(bool);
  59
  60 ///////////////////////////////////////////////////////////////////////////
  61 // Main entry point
  62
  63 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  64     tcx.hir().visit_item_likes_in_module(
  65         module_def_id,
  66         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  67     );
  68 }
  69
  70 pub fn provide(providers: &mut Providers) {
  71     *providers = Providers {
  72         opt_const_param_of: type_of::opt_const_param_of,
  73         type_of: type_of::type_of,
  74         item_bounds: item_bounds::item_bounds,
  75         explicit_item_bounds: item_bounds::explicit_item_bounds,
  76         generics_of,
  77         predicates_of,
  78         predicates_defined_on,
  79         explicit_predicates_of,
  80         super_predicates_of,
  81         super_predicates_that_define_assoc_type,
  82         trait_explicit_predicates_and_bounds,
  83         type_param_predicates,
  84         trait_def,
  85         adt_def,
  86         fn_sig,
  87         impl_trait_ref,
  88         impl_polarity,
  89         is_foreign_item,
  90         static_mutability,
  91         generator_kind,
  92         codegen_fn_attrs,
  93         collect_mod_item_types,
  94         should_inherit_track_caller,
  95         ..*providers
  96     };
  97 }
  98
  99 ///////////////////////////////////////////////////////////////////////////
 100
 101 /// Context specific to some particular item. This is what implements
 102 /// `AstConv`. It has information about the predicates that are defined
 103 /// on the trait. Unfortunately, this predicate information is
 104 /// available in various different forms at various points in the
 105 /// process. So we can't just store a pointer to e.g., the AST or the
 106 /// parsed ty form, we have to be more flexible. To this end, the
 107 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 108 /// `get_type_parameter_bounds` requests, drawing the information from
 109 /// the AST (`hir::Generics`), recursively.
 110 pub struct ItemCtxt<'tcx> {
 111     tcx: TyCtxt<'tcx>,
 112     item_def_id: DefId,
 113 }
 114
 115 ///////////////////////////////////////////////////////////////////////////
 116
 117 #[derive(Default)]
 118 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 119
 120 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 121     type Map = intravisit::ErasedMap<'v>;
 122
 123     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 124         NestedVisitorMap::None
 125     }
 126     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 127         if let hir::TyKind::Infer = t.kind {
 128             self.0.push(t.span);
 129         }
 130         intravisit::walk_ty(self, t)
 131     }
 132     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 133         match generic_arg {
 134             hir::GenericArg::Infer(inf) => {
 135                 self.0.push(inf.span);
 136                 intravisit::walk_inf(self, inf);
 137             }
 138             hir::GenericArg::Type(t) => self.visit_ty(t),
 139             _ => {}
 140         }
 141     }
 142 }
 143
 144 struct CollectItemTypesVisitor<'tcx> {
 145     tcx: TyCtxt<'tcx>,
 146 }
 147
 148 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 149 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 150 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 151 crate fn placeholder_type_error(
 152     tcx: TyCtxt<'tcx>,
 153     span: Option<Span>,
 154     generics: &[hir::GenericParam<'_>],
 155     placeholder_types: Vec<Span>,
 156     suggest: bool,
 157     hir_ty: Option<&hir::Ty<'_>>,
 158     kind: &'static str,
 159 ) {
 160     if placeholder_types.is_empty() {
 161         return;
 162     }
 163
 164     let type_name = generics.next_type_param_name(None);
 165     let mut sugg: Vec<_> =
 166         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 167
 168     if generics.is_empty() {
 169         if let Some(span) = span {
 170             sugg.push((span, format!("<{}>", type_name)));
 171         }
 172     } else if let Some(arg) = generics
 173         .iter()
 174         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 175     {
 176         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 177         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 178         sugg.push((arg.span, (*type_name).to_string()));
 179     } else {
 180         let last = generics.iter().last().unwrap();
 181         sugg.push((
 182             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 183             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 184             format!(", {}", type_name),
 185         ));
 186     }
 187
 188     let mut err = bad_placeholder_type(tcx, placeholder_types, kind);
 189
 190     // Suggest, but only if it is not a function in const or static
 191     if suggest {
 192         let mut is_fn = false;
 193         let mut is_const_or_static = false;
 194
 195         if let Some(hir_ty) = hir_ty {
 196             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 197                 is_fn = true;
 198
 199                 // Check if parent is const or static
 200                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 201                 let parent_node = tcx.hir().get(parent_id);
 202
 203                 is_const_or_static = match parent_node {
 204                     Node::Item(&hir::Item {
 205                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 206                         ..
 207                     })
 208                     | Node::TraitItem(&hir::TraitItem {
 209                         kind: hir::TraitItemKind::Const(..),
 210                         ..
 211                     })
 212                     | Node::ImplItem(&hir::ImplItem {
 213                         kind: hir::ImplItemKind::Const(..), ..
 214                     }) => true,
 215                     _ => false,
 216                 };
 217             }
 218         }
 219
 220         // if function is wrapped around a const or static,
 221         // then don't show the suggestion
 222         if !(is_fn && is_const_or_static) {
 223             err.multipart_suggestion(
 224                 "use type parameters instead",
 225                 sugg,
 226                 Applicability::HasPlaceholders,
 227             );
 228         }
 229     }
 230     err.emit();
 231 }
 232
 233 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 234     let (generics, suggest) = match &item.kind {
 235         hir::ItemKind::Union(_, generics)
 236         | hir::ItemKind::Enum(_, generics)
 237         | hir::ItemKind::TraitAlias(generics, _)
 238         | hir::ItemKind::Trait(_, _, generics, ..)
 239         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 240         | hir::ItemKind::Struct(_, generics) => (generics, true),
 241         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 242         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 243         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 244         _ => return,
 245     };
 246
 247     let mut visitor = PlaceholderHirTyCollector::default();
 248     visitor.visit_item(item);
 249
 250     placeholder_type_error(
 251         tcx,
 252         Some(generics.span),
 253         generics.params,
 254         visitor.0,
 255         suggest,
 256         None,
 257         item.kind.descr(),
 258     );
 259 }
 260
 261 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 262     type Map = Map<'tcx>;
 263
 264     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 265         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 266     }
 267
 268     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 269         convert_item(self.tcx, item.item_id());
 270         reject_placeholder_type_signatures_in_item(self.tcx, item);
 271         intravisit::walk_item(self, item);
 272     }
 273
 274     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 275         for param in generics.params {
 276             match param.kind {
 277                 hir::GenericParamKind::Lifetime { .. } => {}
 278                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 279                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 280                     self.tcx.ensure().type_of(def_id);
 281                 }
 282                 hir::GenericParamKind::Type { .. } => {}
 283                 hir::GenericParamKind::Const { default, .. } => {
 284                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 285                     self.tcx.ensure().type_of(def_id);
 286                     if let Some(default) = default {
 287                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 288                         // need to store default and type of default
 289                         self.tcx.ensure().type_of(default_def_id);
 290                         self.tcx.ensure().const_param_default(def_id);
 291                     }
 292                 }
 293             }
 294         }
 295         intravisit::walk_generics(self, generics);
 296     }
 297
 298     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 299         if let hir::ExprKind::Closure(..) = expr.kind {
 300             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 301             self.tcx.ensure().generics_of(def_id);
 302             self.tcx.ensure().type_of(def_id);
 303         }
 304         intravisit::walk_expr(self, expr);
 305     }
 306
 307     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 308         convert_trait_item(self.tcx, trait_item.trait_item_id());
 309         intravisit::walk_trait_item(self, trait_item);
 310     }
 311
 312     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 313         convert_impl_item(self.tcx, impl_item.impl_item_id());
 314         intravisit::walk_impl_item(self, impl_item);
 315     }
 316 }
 317
 318 ///////////////////////////////////////////////////////////////////////////
 319 // Utility types and common code for the above passes.
 320
 321 fn bad_placeholder_type(
 322     tcx: TyCtxt<'tcx>,
 323     mut spans: Vec<Span>,
 324     kind: &'static str,
 325 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 326     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 327
 328     spans.sort();
 329     let mut err = struct_span_err!(
 330         tcx.sess,
 331         spans.clone(),
 332         E0121,
 333         "the type placeholder `_` is not allowed within types on item signatures for {}",
 334         kind
 335     );
 336     for span in spans {
 337         err.span_label(span, "not allowed in type signatures");
 338     }
 339     err
 340 }
 341
 342 impl ItemCtxt<'tcx> {
 343     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 344         ItemCtxt { tcx, item_def_id }
 345     }
 346
 347     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 348         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 349     }
 350
 351     pub fn hir_id(&self) -> hir::HirId {
 352         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 353     }
 354
 355     pub fn node(&self) -> hir::Node<'tcx> {
 356         self.tcx.hir().get(self.hir_id())
 357     }
 358 }
 359
 360 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 361     fn tcx(&self) -> TyCtxt<'tcx> {
 362         self.tcx
 363     }
 364
 365     fn item_def_id(&self) -> Option<DefId> {
 366         Some(self.item_def_id)
 367     }
 368
 369     fn default_constness_for_trait_bounds(&self) -> hir::Constness {
 370         self.node().constness()
 371     }
 372
 373     fn get_type_parameter_bounds(
 374         &self,
 375         span: Span,
 376         def_id: DefId,
 377         assoc_name: Ident,
 378     ) -> ty::GenericPredicates<'tcx> {
 379         self.tcx.at(span).type_param_predicates((
 380             self.item_def_id,
 381             def_id.expect_local(),
 382             assoc_name,
 383         ))
 384     }
 385
 386     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 387         None
 388     }
 389
 390     fn allow_ty_infer(&self) -> bool {
 391         false
 392     }
 393
 394     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 395         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 396     }
 397
 398     fn ct_infer(
 399         &self,
 400         ty: Ty<'tcx>,
 401         _: Option<&ty::GenericParamDef>,
 402         span: Span,
 403     ) -> &'tcx Const<'tcx> {
 404         bad_placeholder_type(self.tcx(), vec![span], "generic").emit();
 405         // Typeck doesn't expect erased regions to be returned from `type_of`.
 406         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match r {
 407             ty::ReErased => self.tcx.lifetimes.re_static,
 408             _ => r,
 409         });
 410         self.tcx().const_error(ty)
 411     }
 412
 413     fn projected_ty_from_poly_trait_ref(
 414         &self,
 415         span: Span,
 416         item_def_id: DefId,
 417         item_segment: &hir::PathSegment<'_>,
 418         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 419     ) -> Ty<'tcx> {
 420         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 421             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 422                 self,
 423                 self.tcx,
 424                 span,
 425                 item_def_id,
 426                 item_segment,
 427                 trait_ref.substs,
 428             );
 429             self.tcx().mk_projection(item_def_id, item_substs)
 430         } else {
 431             // There are no late-bound regions; we can just ignore the binder.
 432             let mut err = struct_span_err!(
 433                 self.tcx().sess,
 434                 span,
 435                 E0212,
 436                 "cannot use the associated type of a trait \
 437                  with uninferred generic parameters"
 438             );
 439
 440             match self.node() {
 441                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 442                     let item =
 443                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 444                     match &item.kind {
 445                         hir::ItemKind::Enum(_, generics)
 446                         | hir::ItemKind::Struct(_, generics)
 447                         | hir::ItemKind::Union(_, generics) => {
 448                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 449                             let (lt_sp, sugg) = match generics.params {
 450                                 [] => (generics.span, format!("<{}>", lt_name)),
 451                                 [bound, ..] => {
 452                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 453                                 }
 454                             };
 455                             let suggestions = vec![
 456                                 (lt_sp, sugg),
 457                                 (
 458                                     span,
 459                                     format!(
 460                                         "{}::{}",
 461                                         // Replace the existing lifetimes with a new named lifetime.
 462                                         self.tcx
 463                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 464                                                 self.tcx.mk_region(ty::ReEarlyBound(
 465                                                     ty::EarlyBoundRegion {
 466                                                         def_id: item_def_id,
 467                                                         index: 0,
 468                                                         name: Symbol::intern(&lt_name),
 469                                                     },
 470                                                 ))
 471                                             })
 472                                             .0,
 473                                         item_segment.ident
 474                                     ),
 475                                 ),
 476                             ];
 477                             err.multipart_suggestion(
 478                                 "use a fully qualified path with explicit lifetimes",
 479                                 suggestions,
 480                                 Applicability::MaybeIncorrect,
 481                             );
 482                         }
 483                         _ => {}
 484                     }
 485                 }
 486                 hir::Node::Item(hir::Item {
 487                     kind:
 488                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 489                     ..
 490                 }) => {}
 491                 hir::Node::Item(_)
 492                 | hir::Node::ForeignItem(_)
 493                 | hir::Node::TraitItem(_)
 494                 | hir::Node::ImplItem(_) => {
 495                     err.span_suggestion(
 496                         span,
 497                         "use a fully qualified path with inferred lifetimes",
 498                         format!(
 499                             "{}::{}",
 500                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 501                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 502                             item_segment.ident
 503                         ),
 504                         Applicability::MaybeIncorrect,
 505                     );
 506                 }
 507                 _ => {}
 508             }
 509             err.emit();
 510             self.tcx().ty_error()
 511         }
 512     }
 513
 514     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 515         // Types in item signatures are not normalized to avoid undue dependencies.
 516         ty
 517     }
 518
 519     fn set_tainted_by_errors(&self) {
 520         // There's no obvious place to track this, so just let it go.
 521     }
 522
 523     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 524         // There's no place to record types from signatures?
 525     }
 526 }
 527
 528 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 529 fn get_new_lifetime_name<'tcx>(
 530     tcx: TyCtxt<'tcx>,
 531     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 532     generics: &hir::Generics<'tcx>,
 533 ) -> String {
 534     let existing_lifetimes = tcx
 535         .collect_referenced_late_bound_regions(&poly_trait_ref)
 536         .into_iter()
 537         .filter_map(|lt| {
 538             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 539                 Some(name.as_str().to_string())
 540             } else {
 541                 None
 542             }
 543         })
 544         .chain(generics.params.iter().filter_map(|param| {
 545             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 546                 Some(param.name.ident().as_str().to_string())
 547             } else {
 548                 None
 549             }
 550         }))
 551         .collect::<FxHashSet<String>>();
 552
 553     let a_to_z_repeat_n = |n| {
 554         (b'a'..=b'z').map(move |c| {
 555             let mut s = '\''.to_string();
 556             s.extend(std::iter::repeat(char::from(c)).take(n));
 557             s
 558         })
 559     };
 560
 561     // If all single char lifetime names are present, we wrap around and double the chars.
 562     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 563 }
 564
 565 /// Returns the predicates defined on `item_def_id` of the form
 566 /// `X: Foo` where `X` is the type parameter `def_id`.
 567 fn type_param_predicates(
 568     tcx: TyCtxt<'_>,
 569     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 570 ) -> ty::GenericPredicates<'_> {
 571     use rustc_hir::*;
 572
 573     // In the AST, bounds can derive from two places. Either
 574     // written inline like `<T: Foo>` or in a where-clause like
 575     // `where T: Foo`.
 576
 577     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 578     let param_owner = tcx.hir().ty_param_owner(param_id);
 579     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 580     let generics = tcx.generics_of(param_owner_def_id);
 581     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 582     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 583
 584     // Don't look for bounds where the type parameter isn't in scope.
 585     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 586         None
 587     } else {
 588         tcx.generics_of(item_def_id).parent
 589     };
 590
 591     let mut result = parent
 592         .map(|parent| {
 593             let icx = ItemCtxt::new(tcx, parent);
 594             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 595         })
 596         .unwrap_or_default();
 597     let mut extend = None;
 598
 599     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 600     let ast_generics = match tcx.hir().get(item_hir_id) {
 601         Node::TraitItem(item) => &item.generics,
 602
 603         Node::ImplItem(item) => &item.generics,
 604
 605         Node::Item(item) => {
 606             match item.kind {
 607                 ItemKind::Fn(.., ref generics, _)
 608                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 609                 | ItemKind::TyAlias(_, ref generics)
 610                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 611                 | ItemKind::Enum(_, ref generics)
 612                 | ItemKind::Struct(_, ref generics)
 613                 | ItemKind::Union(_, ref generics) => generics,
 614                 ItemKind::Trait(_, _, ref generics, ..) => {
 615                     // Implied `Self: Trait` and supertrait bounds.
 616                     if param_id == item_hir_id {
 617                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 618                         extend =
 619                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 620                     }
 621                     generics
 622                 }
 623                 _ => return result,
 624             }
 625         }
 626
 627         Node::ForeignItem(item) => match item.kind {
 628             ForeignItemKind::Fn(_, _, ref generics) => generics,
 629             _ => return result,
 630         },
 631
 632         _ => return result,
 633     };
 634
 635     let icx = ItemCtxt::new(tcx, item_def_id);
 636     let extra_predicates = extend.into_iter().chain(
 637         icx.type_parameter_bounds_in_generics(
 638             ast_generics,
 639             param_id,
 640             ty,
 641             OnlySelfBounds(true),
 642             Some(assoc_name),
 643         )
 644         .into_iter()
 645         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 646             ty::PredicateKind::Trait(data, _) => data.self_ty().is_param(index),
 647             _ => false,
 648         }),
 649     );
 650     result.predicates =
 651         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 652     result
 653 }
 654
 655 impl ItemCtxt<'tcx> {
 656     /// Finds bounds from `hir::Generics`. This requires scanning through the
 657     /// AST. We do this to avoid having to convert *all* the bounds, which
 658     /// would create artificial cycles. Instead, we can only convert the
 659     /// bounds for a type parameter `X` if `X::Foo` is used.
 660     fn type_parameter_bounds_in_generics(
 661         &self,
 662         ast_generics: &'tcx hir::Generics<'tcx>,
 663         param_id: hir::HirId,
 664         ty: Ty<'tcx>,
 665         only_self_bounds: OnlySelfBounds,
 666         assoc_name: Option<Ident>,
 667     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 668         let constness = self.default_constness_for_trait_bounds();
 669         let from_ty_params = ast_generics
 670             .params
 671             .iter()
 672             .filter_map(|param| match param.kind {
 673                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 674                 _ => None,
 675             })
 676             .flat_map(|bounds| bounds.iter())
 677             .filter(|b| match assoc_name {
 678                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 679                 None => true,
 680             })
 681             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 682
 683         let from_where_clauses = ast_generics
 684             .where_clause
 685             .predicates
 686             .iter()
 687             .filter_map(|wp| match *wp {
 688                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 689                 _ => None,
 690             })
 691             .flat_map(|bp| {
 692                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 693                     Some(ty)
 694                 } else if !only_self_bounds.0 {
 695                     Some(self.to_ty(&bp.bounded_ty))
 696                 } else {
 697                     None
 698                 };
 699                 bp.bounds
 700                     .iter()
 701                     .filter(|b| match assoc_name {
 702                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 703                         None => true,
 704                     })
 705                     .filter_map(move |b| bt.map(|bt| (bt, b)))
 706             })
 707             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 708
 709         from_ty_params.chain(from_where_clauses).collect()
 710     }
 711
 712     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 713         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 714
 715         match b {
 716             hir::GenericBound::Trait(poly_trait_ref, _) => {
 717                 let trait_ref = &poly_trait_ref.trait_ref;
 718                 if let Some(trait_did) = trait_ref.trait_def_id() {
 719                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 720                 } else {
 721                     false
 722                 }
 723             }
 724             _ => false,
 725         }
 726     }
 727 }
 728
 729 /// Tests whether this is the AST for a reference to the type
 730 /// parameter with ID `param_id`. We use this so as to avoid running
 731 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 732 /// conversion of the type to avoid inducing unnecessary cycles.
 733 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 734     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 735         match path.res {
 736             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 737                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 738             }
 739             _ => false,
 740         }
 741     } else {
 742         false
 743     }
 744 }
 745
 746 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 747     let it = tcx.hir().item(item_id);
 748     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 749     let def_id = item_id.def_id;
 750
 751     match it.kind {
 752         // These don't define types.
 753         hir::ItemKind::ExternCrate(_)
 754         | hir::ItemKind::Use(..)
 755         | hir::ItemKind::Mod(_)
 756         | hir::ItemKind::GlobalAsm(_) => {}
 757         hir::ItemKind::ForeignMod { items, .. } => {
 758             for item in items {
 759                 let item = tcx.hir().foreign_item(item.id);
 760                 tcx.ensure().generics_of(item.def_id);
 761                 tcx.ensure().type_of(item.def_id);
 762                 tcx.ensure().predicates_of(item.def_id);
 763                 match item.kind {
 764                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 765                     hir::ForeignItemKind::Static(..) => {
 766                         let mut visitor = PlaceholderHirTyCollector::default();
 767                         visitor.visit_foreign_item(item);
 768                         placeholder_type_error(
 769                             tcx,
 770                             None,
 771                             &[],
 772                             visitor.0,
 773                             false,
 774                             None,
 775                             "static variable",
 776                         );
 777                     }
 778                     _ => (),
 779                 }
 780             }
 781         }
 782         hir::ItemKind::Enum(ref enum_definition, _) => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.ensure().type_of(def_id);
 785             tcx.ensure().predicates_of(def_id);
 786             convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
 787         }
 788         hir::ItemKind::Impl { .. } => {
 789             tcx.ensure().generics_of(def_id);
 790             tcx.ensure().type_of(def_id);
 791             tcx.ensure().impl_trait_ref(def_id);
 792             tcx.ensure().predicates_of(def_id);
 793         }
 794         hir::ItemKind::Trait(..) => {
 795             tcx.ensure().generics_of(def_id);
 796             tcx.ensure().trait_def(def_id);
 797             tcx.at(it.span).super_predicates_of(def_id);
 798             tcx.ensure().predicates_of(def_id);
 799         }
 800         hir::ItemKind::TraitAlias(..) => {
 801             tcx.ensure().generics_of(def_id);
 802             tcx.at(it.span).super_predicates_of(def_id);
 803             tcx.ensure().predicates_of(def_id);
 804         }
 805         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 806             tcx.ensure().generics_of(def_id);
 807             tcx.ensure().type_of(def_id);
 808             tcx.ensure().predicates_of(def_id);
 809
 810             for f in struct_def.fields() {
 811                 let def_id = tcx.hir().local_def_id(f.hir_id);
 812                 tcx.ensure().generics_of(def_id);
 813                 tcx.ensure().type_of(def_id);
 814                 tcx.ensure().predicates_of(def_id);
 815             }
 816
 817             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 818                 convert_variant_ctor(tcx, ctor_hir_id);
 819             }
 820         }
 821
 822         // Desugared from `impl Trait`, so visited by the function's return type.
 823         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 824
 825         // Don't call `type_of` on opaque types, since that depends on type
 826         // checking function bodies. `check_item_type` ensures that it's called
 827         // instead.
 828         hir::ItemKind::OpaqueTy(..) => {
 829             tcx.ensure().generics_of(def_id);
 830             tcx.ensure().predicates_of(def_id);
 831             tcx.ensure().explicit_item_bounds(def_id);
 832         }
 833         hir::ItemKind::TyAlias(..)
 834         | hir::ItemKind::Static(..)
 835         | hir::ItemKind::Const(..)
 836         | hir::ItemKind::Fn(..) => {
 837             tcx.ensure().generics_of(def_id);
 838             tcx.ensure().type_of(def_id);
 839             tcx.ensure().predicates_of(def_id);
 840             match it.kind {
 841                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 842                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 843                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 844                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 845                     if let hir::TyKind::TraitObject(..) = ty.kind {
 846                         let mut visitor = PlaceholderHirTyCollector::default();
 847                         visitor.visit_item(it);
 848                         placeholder_type_error(
 849                             tcx,
 850                             None,
 851                             &[],
 852                             visitor.0,
 853                             false,
 854                             None,
 855                             it.kind.descr(),
 856                         );
 857                     }
 858                 }
 859                 _ => (),
 860             }
 861         }
 862     }
 863 }
 864
 865 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 866     let trait_item = tcx.hir().trait_item(trait_item_id);
 867     tcx.ensure().generics_of(trait_item_id.def_id);
 868
 869     match trait_item.kind {
 870         hir::TraitItemKind::Fn(..) => {
 871             tcx.ensure().type_of(trait_item_id.def_id);
 872             tcx.ensure().fn_sig(trait_item_id.def_id);
 873         }
 874
 875         hir::TraitItemKind::Const(.., Some(_)) => {
 876             tcx.ensure().type_of(trait_item_id.def_id);
 877         }
 878
 879         hir::TraitItemKind::Const(..) => {
 880             tcx.ensure().type_of(trait_item_id.def_id);
 881             // Account for `const C: _;`.
 882             let mut visitor = PlaceholderHirTyCollector::default();
 883             visitor.visit_trait_item(trait_item);
 884             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 885         }
 886
 887         hir::TraitItemKind::Type(_, Some(_)) => {
 888             tcx.ensure().item_bounds(trait_item_id.def_id);
 889             tcx.ensure().type_of(trait_item_id.def_id);
 890             // Account for `type T = _;`.
 891             let mut visitor = PlaceholderHirTyCollector::default();
 892             visitor.visit_trait_item(trait_item);
 893             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 894         }
 895
 896         hir::TraitItemKind::Type(_, None) => {
 897             tcx.ensure().item_bounds(trait_item_id.def_id);
 898             // #74612: Visit and try to find bad placeholders
 899             // even if there is no concrete type.
 900             let mut visitor = PlaceholderHirTyCollector::default();
 901             visitor.visit_trait_item(trait_item);
 902
 903             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 904         }
 905     };
 906
 907     tcx.ensure().predicates_of(trait_item_id.def_id);
 908 }
 909
 910 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 911     let def_id = impl_item_id.def_id;
 912     tcx.ensure().generics_of(def_id);
 913     tcx.ensure().type_of(def_id);
 914     tcx.ensure().predicates_of(def_id);
 915     let impl_item = tcx.hir().impl_item(impl_item_id);
 916     match impl_item.kind {
 917         hir::ImplItemKind::Fn(..) => {
 918             tcx.ensure().fn_sig(def_id);
 919         }
 920         hir::ImplItemKind::TyAlias(_) => {
 921             // Account for `type T = _;`
 922             let mut visitor = PlaceholderHirTyCollector::default();
 923             visitor.visit_impl_item(impl_item);
 924
 925             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 926         }
 927         hir::ImplItemKind::Const(..) => {}
 928     }
 929 }
 930
 931 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 932     let def_id = tcx.hir().local_def_id(ctor_id);
 933     tcx.ensure().generics_of(def_id);
 934     tcx.ensure().type_of(def_id);
 935     tcx.ensure().predicates_of(def_id);
 936 }
 937
 938 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 939     let def = tcx.adt_def(def_id);
 940     let repr_type = def.repr.discr_type();
 941     let initial = repr_type.initial_discriminant(tcx);
 942     let mut prev_discr = None::<Discr<'_>>;
 943
 944     // fill the discriminant values and field types
 945     for variant in variants {
 946         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 947         prev_discr = Some(
 948             if let Some(ref e) = variant.disr_expr {
 949                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 950                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 951             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 952                 Some(discr)
 953             } else {
 954                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 955                     .span_label(
 956                         variant.span,
 957                         format!("overflowed on value after {}", prev_discr.unwrap()),
 958                     )
 959                     .note(&format!(
 960                         "explicitly set `{} = {}` if that is desired outcome",
 961                         variant.ident, wrapped_discr
 962                     ))
 963                     .emit();
 964                 None
 965             }
 966             .unwrap_or(wrapped_discr),
 967         );
 968
 969         for f in variant.data.fields() {
 970             let def_id = tcx.hir().local_def_id(f.hir_id);
 971             tcx.ensure().generics_of(def_id);
 972             tcx.ensure().type_of(def_id);
 973             tcx.ensure().predicates_of(def_id);
 974         }
 975
 976         // Convert the ctor, if any. This also registers the variant as
 977         // an item.
 978         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 979             convert_variant_ctor(tcx, ctor_hir_id);
 980         }
 981     }
 982 }
 983
 984 fn convert_variant(
 985     tcx: TyCtxt<'_>,
 986     variant_did: Option<LocalDefId>,
 987     ctor_did: Option<LocalDefId>,
 988     ident: Ident,
 989     discr: ty::VariantDiscr,
 990     def: &hir::VariantData<'_>,
 991     adt_kind: ty::AdtKind,
 992     parent_did: LocalDefId,
 993 ) -> ty::VariantDef {
 994     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 995     let fields = def
 996         .fields()
 997         .iter()
 998         .map(|f| {
 999             let fid = tcx.hir().local_def_id(f.hir_id);
1000             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
1001             if let Some(prev_span) = dup_span {
1002                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
1003                     field_name: f.ident,
1004                     span: f.span,
1005                     prev_span,
1006                 });
1007             } else {
1008                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
1009             }
1010
1011             ty::FieldDef { did: fid.to_def_id(), ident: f.ident, vis: tcx.visibility(fid) }
1012         })
1013         .collect();
1014     let recovered = match def {
1015         hir::VariantData::Struct(_, r) => *r,
1016         _ => false,
1017     };
1018     ty::VariantDef::new(
1019         ident,
1020         variant_did.map(LocalDefId::to_def_id),
1021         ctor_did.map(LocalDefId::to_def_id),
1022         discr,
1023         fields,
1024         CtorKind::from_hir(def),
1025         adt_kind,
1026         parent_did.to_def_id(),
1027         recovered,
1028         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1029             || variant_did.map_or(false, |variant_did| {
1030                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1031             }),
1032     )
1033 }
1034
1035 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1036     use rustc_hir::*;
1037
1038     let def_id = def_id.expect_local();
1039     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1040     let item = match tcx.hir().get(hir_id) {
1041         Node::Item(item) => item,
1042         _ => bug!(),
1043     };
1044
1045     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1046     let (kind, variants) = match item.kind {
1047         ItemKind::Enum(ref def, _) => {
1048             let mut distance_from_explicit = 0;
1049             let variants = def
1050                 .variants
1051                 .iter()
1052                 .map(|v| {
1053                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1054                     let ctor_did =
1055                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1056
1057                     let discr = if let Some(ref e) = v.disr_expr {
1058                         distance_from_explicit = 0;
1059                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1060                     } else {
1061                         ty::VariantDiscr::Relative(distance_from_explicit)
1062                     };
1063                     distance_from_explicit += 1;
1064
1065                     convert_variant(
1066                         tcx,
1067                         variant_did,
1068                         ctor_did,
1069                         v.ident,
1070                         discr,
1071                         &v.data,
1072                         AdtKind::Enum,
1073                         def_id,
1074                     )
1075                 })
1076                 .collect();
1077
1078             (AdtKind::Enum, variants)
1079         }
1080         ItemKind::Struct(ref def, _) => {
1081             let variant_did = None::<LocalDefId>;
1082             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1083
1084             let variants = std::iter::once(convert_variant(
1085                 tcx,
1086                 variant_did,
1087                 ctor_did,
1088                 item.ident,
1089                 ty::VariantDiscr::Relative(0),
1090                 def,
1091                 AdtKind::Struct,
1092                 def_id,
1093             ))
1094             .collect();
1095
1096             (AdtKind::Struct, variants)
1097         }
1098         ItemKind::Union(ref def, _) => {
1099             let variant_did = None;
1100             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1101
1102             let variants = std::iter::once(convert_variant(
1103                 tcx,
1104                 variant_did,
1105                 ctor_did,
1106                 item.ident,
1107                 ty::VariantDiscr::Relative(0),
1108                 def,
1109                 AdtKind::Union,
1110                 def_id,
1111             ))
1112             .collect();
1113
1114             (AdtKind::Union, variants)
1115         }
1116         _ => bug!(),
1117     };
1118     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1119 }
1120
1121 /// Ensures that the super-predicates of the trait with a `DefId`
1122 /// of `trait_def_id` are converted and stored. This also ensures that
1123 /// the transitive super-predicates are converted.
1124 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1125     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1126     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1127 }
1128
1129 /// Ensures that the super-predicates of the trait with a `DefId`
1130 /// of `trait_def_id` are converted and stored. This also ensures that
1131 /// the transitive super-predicates are converted.
1132 fn super_predicates_that_define_assoc_type(
1133     tcx: TyCtxt<'_>,
1134     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1135 ) -> ty::GenericPredicates<'_> {
1136     debug!(
1137         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1138         trait_def_id, assoc_name
1139     );
1140     if trait_def_id.is_local() {
1141         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1142         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1143
1144         let item = match tcx.hir().get(trait_hir_id) {
1145             Node::Item(item) => item,
1146             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1147         };
1148
1149         let (generics, bounds) = match item.kind {
1150             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1151             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1152             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1153         };
1154
1155         let icx = ItemCtxt::new(tcx, trait_def_id);
1156
1157         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1158         let self_param_ty = tcx.types.self_param;
1159         let superbounds1 = if let Some(assoc_name) = assoc_name {
1160             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1161                 &icx,
1162                 self_param_ty,
1163                 &bounds,
1164                 SizedByDefault::No,
1165                 item.span,
1166                 assoc_name,
1167             )
1168         } else {
1169             <dyn AstConv<'_>>::compute_bounds(
1170                 &icx,
1171                 self_param_ty,
1172                 &bounds,
1173                 SizedByDefault::No,
1174                 item.span,
1175             )
1176         };
1177
1178         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1179
1180         // Convert any explicit superbounds in the where-clause,
1181         // e.g., `trait Foo where Self: Bar`.
1182         // In the case of trait aliases, however, we include all bounds in the where-clause,
1183         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1184         // as one of its "superpredicates".
1185         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1186         let superbounds2 = icx.type_parameter_bounds_in_generics(
1187             generics,
1188             item.hir_id(),
1189             self_param_ty,
1190             OnlySelfBounds(!is_trait_alias),
1191             assoc_name,
1192         );
1193
1194         // Combine the two lists to form the complete set of superbounds:
1195         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1196
1197         // Now require that immediate supertraits are converted,
1198         // which will, in turn, reach indirect supertraits.
1199         if assoc_name.is_none() {
1200             // Now require that immediate supertraits are converted,
1201             // which will, in turn, reach indirect supertraits.
1202             for &(pred, span) in superbounds {
1203                 debug!("superbound: {:?}", pred);
1204                 if let ty::PredicateKind::Trait(bound, _) = pred.kind().skip_binder() {
1205                     tcx.at(span).super_predicates_of(bound.def_id());
1206                 }
1207             }
1208         }
1209
1210         ty::GenericPredicates { parent: None, predicates: superbounds }
1211     } else {
1212         // if `assoc_name` is None, then the query should've been redirected to an
1213         // external provider
1214         assert!(assoc_name.is_some());
1215         tcx.super_predicates_of(trait_def_id)
1216     }
1217 }
1218
1219 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1220     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1221     let item = tcx.hir().expect_item(hir_id);
1222
1223     let (is_auto, unsafety) = match item.kind {
1224         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1225         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1226         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1227     };
1228
1229     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1230     if paren_sugar && !tcx.features().unboxed_closures {
1231         tcx.sess
1232             .struct_span_err(
1233                 item.span,
1234                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1235                  which traits can use parenthetical notation",
1236             )
1237             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1238             .emit();
1239     }
1240
1241     let is_marker = tcx.has_attr(def_id, sym::marker);
1242     let skip_array_during_method_dispatch =
1243         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1244     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1245         ty::trait_def::TraitSpecializationKind::Marker
1246     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1247         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1248     } else {
1249         ty::trait_def::TraitSpecializationKind::None
1250     };
1251     let def_path_hash = tcx.def_path_hash(def_id);
1252     ty::TraitDef::new(
1253         def_id,
1254         unsafety,
1255         paren_sugar,
1256         is_auto,
1257         is_marker,
1258         skip_array_during_method_dispatch,
1259         spec_kind,
1260         def_path_hash,
1261     )
1262 }
1263
1264 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1265     struct LateBoundRegionsDetector<'tcx> {
1266         tcx: TyCtxt<'tcx>,
1267         outer_index: ty::DebruijnIndex,
1268         has_late_bound_regions: Option<Span>,
1269     }
1270
1271     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1272         type Map = intravisit::ErasedMap<'tcx>;
1273
1274         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1275             NestedVisitorMap::None
1276         }
1277
1278         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1279             if self.has_late_bound_regions.is_some() {
1280                 return;
1281             }
1282             match ty.kind {
1283                 hir::TyKind::BareFn(..) => {
1284                     self.outer_index.shift_in(1);
1285                     intravisit::walk_ty(self, ty);
1286                     self.outer_index.shift_out(1);
1287                 }
1288                 _ => intravisit::walk_ty(self, ty),
1289             }
1290         }
1291
1292         fn visit_poly_trait_ref(
1293             &mut self,
1294             tr: &'tcx hir::PolyTraitRef<'tcx>,
1295             m: hir::TraitBoundModifier,
1296         ) {
1297             if self.has_late_bound_regions.is_some() {
1298                 return;
1299             }
1300             self.outer_index.shift_in(1);
1301             intravisit::walk_poly_trait_ref(self, tr, m);
1302             self.outer_index.shift_out(1);
1303         }
1304
1305         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1306             if self.has_late_bound_regions.is_some() {
1307                 return;
1308             }
1309
1310             match self.tcx.named_region(lt.hir_id) {
1311                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1312                 Some(
1313                     rl::Region::LateBound(debruijn, _, _, _)
1314                     | rl::Region::LateBoundAnon(debruijn, _, _),
1315                 ) if debruijn < self.outer_index => {}
1316                 Some(
1317                     rl::Region::LateBound(..)
1318                     | rl::Region::LateBoundAnon(..)
1319                     | rl::Region::Free(..),
1320                 )
1321                 | None => {
1322                     self.has_late_bound_regions = Some(lt.span);
1323                 }
1324             }
1325         }
1326     }
1327
1328     fn has_late_bound_regions<'tcx>(
1329         tcx: TyCtxt<'tcx>,
1330         generics: &'tcx hir::Generics<'tcx>,
1331         decl: &'tcx hir::FnDecl<'tcx>,
1332     ) -> Option<Span> {
1333         let mut visitor = LateBoundRegionsDetector {
1334             tcx,
1335             outer_index: ty::INNERMOST,
1336             has_late_bound_regions: None,
1337         };
1338         for param in generics.params {
1339             if let GenericParamKind::Lifetime { .. } = param.kind {
1340                 if tcx.is_late_bound(param.hir_id) {
1341                     return Some(param.span);
1342                 }
1343             }
1344         }
1345         visitor.visit_fn_decl(decl);
1346         visitor.has_late_bound_regions
1347     }
1348
1349     match node {
1350         Node::TraitItem(item) => match item.kind {
1351             hir::TraitItemKind::Fn(ref sig, _) => {
1352                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1353             }
1354             _ => None,
1355         },
1356         Node::ImplItem(item) => match item.kind {
1357             hir::ImplItemKind::Fn(ref sig, _) => {
1358                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1359             }
1360             _ => None,
1361         },
1362         Node::ForeignItem(item) => match item.kind {
1363             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1364                 has_late_bound_regions(tcx, generics, fn_decl)
1365             }
1366             _ => None,
1367         },
1368         Node::Item(item) => match item.kind {
1369             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1370                 has_late_bound_regions(tcx, generics, &sig.decl)
1371             }
1372             _ => None,
1373         },
1374         _ => None,
1375     }
1376 }
1377
1378 struct AnonConstInParamTyDetector {
1379     in_param_ty: bool,
1380     found_anon_const_in_param_ty: bool,
1381     ct: HirId,
1382 }
1383
1384 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1385     type Map = intravisit::ErasedMap<'v>;
1386
1387     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1388         NestedVisitorMap::None
1389     }
1390
1391     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1392         if let GenericParamKind::Const { ref ty, default: _ } = p.kind {
1393             let prev = self.in_param_ty;
1394             self.in_param_ty = true;
1395             self.visit_ty(ty);
1396             self.in_param_ty = prev;
1397         }
1398     }
1399
1400     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1401         if self.in_param_ty && self.ct == c.hir_id {
1402             self.found_anon_const_in_param_ty = true;
1403         } else {
1404             intravisit::walk_anon_const(self, c)
1405         }
1406     }
1407 }
1408
1409 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1410     use rustc_hir::*;
1411
1412     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1413
1414     let node = tcx.hir().get(hir_id);
1415     let parent_def_id = match node {
1416         Node::ImplItem(_)
1417         | Node::TraitItem(_)
1418         | Node::Variant(_)
1419         | Node::Ctor(..)
1420         | Node::Field(_) => {
1421             let parent_id = tcx.hir().get_parent_item(hir_id);
1422             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1423         }
1424         // FIXME(#43408) always enable this once `lazy_normalization` is
1425         // stable enough and does not need a feature gate anymore.
1426         Node::AnonConst(_) => {
1427             let parent_id = tcx.hir().get_parent_item(hir_id);
1428             let parent_def_id = tcx.hir().local_def_id(parent_id);
1429
1430             let mut in_param_ty = false;
1431             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1432                 if let Some(generics) = node.generics() {
1433                     let mut visitor = AnonConstInParamTyDetector {
1434                         in_param_ty: false,
1435                         found_anon_const_in_param_ty: false,
1436                         ct: hir_id,
1437                     };
1438
1439                     visitor.visit_generics(generics);
1440                     in_param_ty = visitor.found_anon_const_in_param_ty;
1441                     break;
1442                 }
1443             }
1444
1445             if in_param_ty {
1446                 // We do not allow generic parameters in anon consts if we are inside
1447                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1448                 None
1449             } else if tcx.lazy_normalization() {
1450                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1451                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1452                     //
1453                     // struct Foo<const N: usize = { .. }>;
1454                     //        ^^^       ^          ^^^^^^ def id of this anon const
1455                     //        ^         ^ param_id
1456                     //        ^ parent_def_id
1457                     //
1458                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1459                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1460                     //
1461                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1462                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1463                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1464                     //
1465                     // We fix this by having this function return the parent's generics ourselves and truncating the
1466                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1467                     //
1468                     // For the above code example that means we want `substs: []`
1469                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1470                     // the def id of the `{ N + 1 }` anon const
1471                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1472                     //
1473                     // This has some implications for how we get the predicates available to the anon const
1474                     // see `explicit_predicates_of` for more information on this
1475                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1476                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1477                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1478                     // In the above example this would be .params[..N#0]
1479                     let params = generics.params[..param_def_idx as usize].to_owned();
1480                     let param_def_id_to_index =
1481                         params.iter().map(|param| (param.def_id, param.index)).collect();
1482
1483                     return ty::Generics {
1484                         // we set the parent of these generics to be our parent's parent so that we
1485                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1486                         // struct Foo<const N: usize, const M: usize = { ... }>;
1487                         parent: generics.parent,
1488                         parent_count: generics.parent_count,
1489                         params,
1490                         param_def_id_to_index,
1491                         has_self: generics.has_self,
1492                         has_late_bound_regions: generics.has_late_bound_regions,
1493                     };
1494                 }
1495
1496                 // HACK(eddyb) this provides the correct generics when
1497                 // `feature(const_generics)` is enabled, so that const expressions
1498                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1499                 //
1500                 // Note that we do not supply the parent generics when using
1501                 // `min_const_generics`.
1502                 Some(parent_def_id.to_def_id())
1503             } else {
1504                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1505                 match parent_node {
1506                     // HACK(eddyb) this provides the correct generics for repeat
1507                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1508                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1509                     // as they shouldn't be able to cause query cycle errors.
1510                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1511                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1512                         if constant.hir_id == hir_id =>
1513                     {
1514                         Some(parent_def_id.to_def_id())
1515                     }
1516
1517                     _ => None,
1518                 }
1519             }
1520         }
1521         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1522             Some(tcx.closure_base_def_id(def_id))
1523         }
1524         Node::Item(item) => match item.kind {
1525             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1526                 impl_trait_fn.or_else(|| {
1527                     let parent_id = tcx.hir().get_parent_item(hir_id);
1528                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1529                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1530                     // Opaque types are always nested within another item, and
1531                     // inherit the generics of the item.
1532                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1533                 })
1534             }
1535             _ => None,
1536         },
1537         _ => None,
1538     };
1539
1540     let mut opt_self = None;
1541     let mut allow_defaults = false;
1542
1543     let no_generics = hir::Generics::empty();
1544     let ast_generics = match node {
1545         Node::TraitItem(item) => &item.generics,
1546
1547         Node::ImplItem(item) => &item.generics,
1548
1549         Node::Item(item) => {
1550             match item.kind {
1551                 ItemKind::Fn(.., ref generics, _)
1552                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1553
1554                 ItemKind::TyAlias(_, ref generics)
1555                 | ItemKind::Enum(_, ref generics)
1556                 | ItemKind::Struct(_, ref generics)
1557                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1558                 | ItemKind::Union(_, ref generics) => {
1559                     allow_defaults = true;
1560                     generics
1561                 }
1562
1563                 ItemKind::Trait(_, _, ref generics, ..)
1564                 | ItemKind::TraitAlias(ref generics, ..) => {
1565                     // Add in the self type parameter.
1566                     //
1567                     // Something of a hack: use the node id for the trait, also as
1568                     // the node id for the Self type parameter.
1569                     let param_id = item.def_id;
1570
1571                     opt_self = Some(ty::GenericParamDef {
1572                         index: 0,
1573                         name: kw::SelfUpper,
1574                         def_id: param_id.to_def_id(),
1575                         pure_wrt_drop: false,
1576                         kind: ty::GenericParamDefKind::Type {
1577                             has_default: false,
1578                             object_lifetime_default: rl::Set1::Empty,
1579                             synthetic: None,
1580                         },
1581                     });
1582
1583                     allow_defaults = true;
1584                     generics
1585                 }
1586
1587                 _ => &no_generics,
1588             }
1589         }
1590
1591         Node::ForeignItem(item) => match item.kind {
1592             ForeignItemKind::Static(..) => &no_generics,
1593             ForeignItemKind::Fn(_, _, ref generics) => generics,
1594             ForeignItemKind::Type => &no_generics,
1595         },
1596
1597         _ => &no_generics,
1598     };
1599
1600     let has_self = opt_self.is_some();
1601     let mut parent_has_self = false;
1602     let mut own_start = has_self as u32;
1603     let parent_count = parent_def_id.map_or(0, |def_id| {
1604         let generics = tcx.generics_of(def_id);
1605         assert_eq!(has_self, false);
1606         parent_has_self = generics.has_self;
1607         own_start = generics.count() as u32;
1608         generics.parent_count + generics.params.len()
1609     });
1610
1611     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1612
1613     if let Some(opt_self) = opt_self {
1614         params.push(opt_self);
1615     }
1616
1617     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1618     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1619         name: param.name.ident().name,
1620         index: own_start + i as u32,
1621         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1622         pure_wrt_drop: param.pure_wrt_drop,
1623         kind: ty::GenericParamDefKind::Lifetime,
1624     }));
1625
1626     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1627
1628     // Now create the real type and const parameters.
1629     let type_start = own_start - has_self as u32 + params.len() as u32;
1630     let mut i = 0;
1631
1632     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1633         GenericParamKind::Lifetime { .. } => None,
1634         GenericParamKind::Type { ref default, synthetic, .. } => {
1635             if !allow_defaults && default.is_some() {
1636                 if !tcx.features().default_type_parameter_fallback {
1637                     tcx.struct_span_lint_hir(
1638                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1639                         param.hir_id,
1640                         param.span,
1641                         |lint| {
1642                             lint.build(
1643                                 "defaults for type parameters are only allowed in \
1644                                  `struct`, `enum`, `type`, or `trait` definitions",
1645                             )
1646                             .emit();
1647                         },
1648                     );
1649                 }
1650             }
1651
1652             let kind = ty::GenericParamDefKind::Type {
1653                 has_default: default.is_some(),
1654                 object_lifetime_default: object_lifetime_defaults
1655                     .as_ref()
1656                     .map_or(rl::Set1::Empty, |o| o[i]),
1657                 synthetic,
1658             };
1659
1660             let param_def = ty::GenericParamDef {
1661                 index: type_start + i as u32,
1662                 name: param.name.ident().name,
1663                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1664                 pure_wrt_drop: param.pure_wrt_drop,
1665                 kind,
1666             };
1667             i += 1;
1668             Some(param_def)
1669         }
1670         GenericParamKind::Const { default, .. } => {
1671             if !allow_defaults && default.is_some() {
1672                 tcx.sess.span_err(
1673                     param.span,
1674                     "defaults for const parameters are only allowed in \
1675                     `struct`, `enum`, `type`, or `trait` definitions",
1676                 );
1677             }
1678
1679             let param_def = ty::GenericParamDef {
1680                 index: type_start + i as u32,
1681                 name: param.name.ident().name,
1682                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1683                 pure_wrt_drop: param.pure_wrt_drop,
1684                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1685             };
1686             i += 1;
1687             Some(param_def)
1688         }
1689     }));
1690
1691     // provide junk type parameter defs - the only place that
1692     // cares about anything but the length is instantiation,
1693     // and we don't do that for closures.
1694     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1695         let dummy_args = if gen.is_some() {
1696             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1697         } else {
1698             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1699         };
1700
1701         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1702             index: type_start + i as u32,
1703             name: Symbol::intern(arg),
1704             def_id,
1705             pure_wrt_drop: false,
1706             kind: ty::GenericParamDefKind::Type {
1707                 has_default: false,
1708                 object_lifetime_default: rl::Set1::Empty,
1709                 synthetic: None,
1710             },
1711         }));
1712     }
1713
1714     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1715
1716     ty::Generics {
1717         parent: parent_def_id,
1718         parent_count,
1719         params,
1720         param_def_id_to_index,
1721         has_self: has_self || parent_has_self,
1722         has_late_bound_regions: has_late_bound_regions(tcx, node),
1723     }
1724 }
1725
1726 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1727     generic_args.iter().any(|arg| match arg {
1728         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1729         hir::GenericArg::Infer(_) => true,
1730         _ => false,
1731     })
1732 }
1733
1734 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1735 /// use inference to provide suggestions for the appropriate type if possible.
1736 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1737     use hir::TyKind::*;
1738     match &ty.kind {
1739         Infer => true,
1740         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1741         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1742         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1743         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1744         Path(hir::QPath::TypeRelative(ty, segment)) => {
1745             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1746         }
1747         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1748             ty_opt.map_or(false, is_suggestable_infer_ty)
1749                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1750         }
1751         _ => false,
1752     }
1753 }
1754
1755 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1756     if let hir::FnRetTy::Return(ref ty) = output {
1757         if is_suggestable_infer_ty(ty) {
1758             return Some(&**ty);
1759         }
1760     }
1761     None
1762 }
1763
1764 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1765     use rustc_hir::Node::*;
1766     use rustc_hir::*;
1767
1768     let def_id = def_id.expect_local();
1769     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1770
1771     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1772
1773     match tcx.hir().get(hir_id) {
1774         TraitItem(hir::TraitItem {
1775             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1776             ident,
1777             generics,
1778             ..
1779         })
1780         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1781         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1782             match get_infer_ret_ty(&sig.decl.output) {
1783                 Some(ty) => {
1784                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1785                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1786                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match r {
1787                         ty::ReErased => tcx.lifetimes.re_static,
1788                         _ => r,
1789                     });
1790                     let fn_sig = ty::Binder::dummy(fn_sig);
1791
1792                     let mut visitor = PlaceholderHirTyCollector::default();
1793                     visitor.visit_ty(ty);
1794                     let mut diag = bad_placeholder_type(tcx, visitor.0, "return type");
1795                     let ret_ty = fn_sig.skip_binder().output();
1796                     if ret_ty != tcx.ty_error() {
1797                         if !ret_ty.is_closure() {
1798                             let ret_ty_str = match ret_ty.kind() {
1799                                 // Suggest a function pointer return type instead of a unique function definition
1800                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1801                                 // syntax)
1802                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1803                                 _ => ret_ty.to_string(),
1804                             };
1805                             diag.span_suggestion(
1806                                 ty.span,
1807                                 "replace with the correct return type",
1808                                 ret_ty_str,
1809                                 Applicability::MaybeIncorrect,
1810                             );
1811                         } else {
1812                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1813                             // to prevent the user from getting a papercut while trying to use the unique closure
1814                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1815                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1816                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1817                         }
1818                     }
1819                     diag.emit();
1820
1821                     fn_sig
1822                 }
1823                 None => <dyn AstConv<'_>>::ty_of_fn(
1824                     &icx,
1825                     hir_id,
1826                     sig.header.unsafety,
1827                     sig.header.abi,
1828                     &sig.decl,
1829                     &generics,
1830                     Some(ident.span),
1831                     None,
1832                 ),
1833             }
1834         }
1835
1836         TraitItem(hir::TraitItem {
1837             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1838             ident,
1839             generics,
1840             ..
1841         }) => <dyn AstConv<'_>>::ty_of_fn(
1842             &icx,
1843             hir_id,
1844             header.unsafety,
1845             header.abi,
1846             decl,
1847             &generics,
1848             Some(ident.span),
1849             None,
1850         ),
1851
1852         ForeignItem(&hir::ForeignItem {
1853             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1854             ident,
1855             ..
1856         }) => {
1857             let abi = tcx.hir().get_foreign_abi(hir_id);
1858             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1859         }
1860
1861         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1862             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1863             let inputs =
1864                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1865             ty::Binder::dummy(tcx.mk_fn_sig(
1866                 inputs,
1867                 ty,
1868                 false,
1869                 hir::Unsafety::Normal,
1870                 abi::Abi::Rust,
1871             ))
1872         }
1873
1874         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1875             // Closure signatures are not like other function
1876             // signatures and cannot be accessed through `fn_sig`. For
1877             // example, a closure signature excludes the `self`
1878             // argument. In any case they are embedded within the
1879             // closure type as part of the `ClosureSubsts`.
1880             //
1881             // To get the signature of a closure, you should use the
1882             // `sig` method on the `ClosureSubsts`:
1883             //
1884             //    substs.as_closure().sig(def_id, tcx)
1885             bug!(
1886                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1887             );
1888         }
1889
1890         x => {
1891             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1892         }
1893     }
1894 }
1895
1896 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1897     let icx = ItemCtxt::new(tcx, def_id);
1898
1899     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1900     match tcx.hir().expect_item(hir_id).kind {
1901         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1902             let selfty = tcx.type_of(def_id);
1903             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1904         }),
1905         _ => bug!(),
1906     }
1907 }
1908
1909 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1910     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1911     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1912     let item = tcx.hir().expect_item(hir_id);
1913     match &item.kind {
1914         hir::ItemKind::Impl(hir::Impl {
1915             polarity: hir::ImplPolarity::Negative(span),
1916             of_trait,
1917             ..
1918         }) => {
1919             if is_rustc_reservation {
1920                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1921                 tcx.sess.span_err(span, "reservation impls can't be negative");
1922             }
1923             ty::ImplPolarity::Negative
1924         }
1925         hir::ItemKind::Impl(hir::Impl {
1926             polarity: hir::ImplPolarity::Positive,
1927             of_trait: None,
1928             ..
1929         }) => {
1930             if is_rustc_reservation {
1931                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1932             }
1933             ty::ImplPolarity::Positive
1934         }
1935         hir::ItemKind::Impl(hir::Impl {
1936             polarity: hir::ImplPolarity::Positive,
1937             of_trait: Some(_),
1938             ..
1939         }) => {
1940             if is_rustc_reservation {
1941                 ty::ImplPolarity::Reservation
1942             } else {
1943                 ty::ImplPolarity::Positive
1944             }
1945         }
1946         item => bug!("impl_polarity: {:?} not an impl", item),
1947     }
1948 }
1949
1950 /// Returns the early-bound lifetimes declared in this generics
1951 /// listing. For anything other than fns/methods, this is just all
1952 /// the lifetimes that are declared. For fns or methods, we have to
1953 /// screen out those that do not appear in any where-clauses etc using
1954 /// `resolve_lifetime::early_bound_lifetimes`.
1955 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1956     tcx: TyCtxt<'tcx>,
1957     generics: &'a hir::Generics<'a>,
1958 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1959     generics.params.iter().filter(move |param| match param.kind {
1960         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1961         _ => false,
1962     })
1963 }
1964
1965 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1966 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1967 /// inferred constraints concerning which regions outlive other regions.
1968 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1969     debug!("predicates_defined_on({:?})", def_id);
1970     let mut result = tcx.explicit_predicates_of(def_id);
1971     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1972     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1973     if !inferred_outlives.is_empty() {
1974         debug!(
1975             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1976             def_id, inferred_outlives,
1977         );
1978         if result.predicates.is_empty() {
1979             result.predicates = inferred_outlives;
1980         } else {
1981             result.predicates = tcx
1982                 .arena
1983                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1984         }
1985     }
1986
1987     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1988     result
1989 }
1990
1991 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1992 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1993 /// `Self: Trait` predicates for traits.
1994 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1995     let mut result = tcx.predicates_defined_on(def_id);
1996
1997     if tcx.is_trait(def_id) {
1998         // For traits, add `Self: Trait` predicate. This is
1999         // not part of the predicates that a user writes, but it
2000         // is something that one must prove in order to invoke a
2001         // method or project an associated type.
2002         //
2003         // In the chalk setup, this predicate is not part of the
2004         // "predicates" for a trait item. But it is useful in
2005         // rustc because if you directly (e.g.) invoke a trait
2006         // method like `Trait::method(...)`, you must naturally
2007         // prove that the trait applies to the types that were
2008         // used, and adding the predicate into this list ensures
2009         // that this is done.
2010         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
2011         result.predicates =
2012             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2013                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2014                 span,
2015             ))));
2016     }
2017     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2018     result
2019 }
2020
2021 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2022 /// N.B., this does not include any implied/inferred constraints.
2023 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2024     use rustc_hir::*;
2025
2026     debug!("explicit_predicates_of(def_id={:?})", def_id);
2027
2028     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2029     let node = tcx.hir().get(hir_id);
2030
2031     let mut is_trait = None;
2032     let mut is_default_impl_trait = None;
2033
2034     let icx = ItemCtxt::new(tcx, def_id);
2035     let constness = icx.default_constness_for_trait_bounds();
2036
2037     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2038
2039     // We use an `IndexSet` to preserves order of insertion.
2040     // Preserving the order of insertion is important here so as not to break UI tests.
2041     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2042
2043     let ast_generics = match node {
2044         Node::TraitItem(item) => &item.generics,
2045
2046         Node::ImplItem(item) => &item.generics,
2047
2048         Node::Item(item) => {
2049             match item.kind {
2050                 ItemKind::Impl(ref impl_) => {
2051                     if impl_.defaultness.is_default() {
2052                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2053                     }
2054                     &impl_.generics
2055                 }
2056                 ItemKind::Fn(.., ref generics, _)
2057                 | ItemKind::TyAlias(_, ref generics)
2058                 | ItemKind::Enum(_, ref generics)
2059                 | ItemKind::Struct(_, ref generics)
2060                 | ItemKind::Union(_, ref generics) => generics,
2061
2062                 ItemKind::Trait(_, _, ref generics, ..) => {
2063                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2064                     generics
2065                 }
2066                 ItemKind::TraitAlias(ref generics, _) => {
2067                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2068                     generics
2069                 }
2070                 ItemKind::OpaqueTy(OpaqueTy {
2071                     bounds: _,
2072                     impl_trait_fn,
2073                     ref generics,
2074                     origin: _,
2075                 }) => {
2076                     if impl_trait_fn.is_some() {
2077                         // return-position impl trait
2078                         //
2079                         // We don't inherit predicates from the parent here:
2080                         // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2081                         // then the return type is `f::<'static, T>::{{opaque}}`.
2082                         //
2083                         // If we inherited the predicates of `f` then we would
2084                         // require that `T: 'static` to show that the return
2085                         // type is well-formed.
2086                         //
2087                         // The only way to have something with this opaque type
2088                         // is from the return type of the containing function,
2089                         // which will ensure that the function's predicates
2090                         // hold.
2091                         return ty::GenericPredicates { parent: None, predicates: &[] };
2092                     } else {
2093                         // type-alias impl trait
2094                         generics
2095                     }
2096                 }
2097
2098                 _ => NO_GENERICS,
2099             }
2100         }
2101
2102         Node::ForeignItem(item) => match item.kind {
2103             ForeignItemKind::Static(..) => NO_GENERICS,
2104             ForeignItemKind::Fn(_, _, ref generics) => generics,
2105             ForeignItemKind::Type => NO_GENERICS,
2106         },
2107
2108         _ => NO_GENERICS,
2109     };
2110
2111     let generics = tcx.generics_of(def_id);
2112     let parent_count = generics.parent_count as u32;
2113     let has_own_self = generics.has_self && parent_count == 0;
2114
2115     // Below we'll consider the bounds on the type parameters (including `Self`)
2116     // and the explicit where-clauses, but to get the full set of predicates
2117     // on a trait we need to add in the supertrait bounds and bounds found on
2118     // associated types.
2119     if let Some(_trait_ref) = is_trait {
2120         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2121     }
2122
2123     // In default impls, we can assume that the self type implements
2124     // the trait. So in:
2125     //
2126     //     default impl Foo for Bar { .. }
2127     //
2128     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2129     // (see below). Recall that a default impl is not itself an impl, but rather a
2130     // set of defaults that can be incorporated into another impl.
2131     if let Some(trait_ref) = is_default_impl_trait {
2132         predicates.insert((
2133             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
2134             tcx.def_span(def_id),
2135         ));
2136     }
2137
2138     // Collect the region predicates that were declared inline as
2139     // well. In the case of parameters declared on a fn or method, we
2140     // have to be careful to only iterate over early-bound regions.
2141     let mut index = parent_count + has_own_self as u32;
2142     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2143         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2144             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2145             index,
2146             name: param.name.ident().name,
2147         }));
2148         index += 1;
2149
2150         match param.kind {
2151             GenericParamKind::Lifetime { .. } => {
2152                 param.bounds.iter().for_each(|bound| match bound {
2153                     hir::GenericBound::Outlives(lt) => {
2154                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, &lt, None);
2155                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2156                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2157                     }
2158                     _ => bug!(),
2159                 });
2160             }
2161             _ => bug!(),
2162         }
2163     }
2164
2165     // Collect the predicates that were written inline by the user on each
2166     // type parameter (e.g., `<T: Foo>`).
2167     for param in ast_generics.params {
2168         match param.kind {
2169             // We already dealt with early bound lifetimes above.
2170             GenericParamKind::Lifetime { .. } => (),
2171             GenericParamKind::Type { .. } => {
2172                 let name = param.name.ident().name;
2173                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2174                 index += 1;
2175
2176                 let sized = SizedByDefault::Yes;
2177                 let bounds = <dyn AstConv<'_>>::compute_bounds(
2178                     &icx,
2179                     param_ty,
2180                     &param.bounds,
2181                     sized,
2182                     param.span,
2183                 );
2184                 predicates.extend(bounds.predicates(tcx, param_ty));
2185             }
2186             GenericParamKind::Const { .. } => {
2187                 // Bounds on const parameters are currently not possible.
2188                 debug_assert!(param.bounds.is_empty());
2189                 index += 1;
2190             }
2191         }
2192     }
2193
2194     // Add in the bounds that appear in the where-clause.
2195     let where_clause = &ast_generics.where_clause;
2196     for predicate in where_clause.predicates {
2197         match predicate {
2198             hir::WherePredicate::BoundPredicate(bound_pred) => {
2199                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2200                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2201
2202                 // Keep the type around in a dummy predicate, in case of no bounds.
2203                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2204                 // is still checked for WF.
2205                 if bound_pred.bounds.is_empty() {
2206                     if let ty::Param(_) = ty.kind() {
2207                         // This is a `where T:`, which can be in the HIR from the
2208                         // transformation that moves `?Sized` to `T`'s declaration.
2209                         // We can skip the predicate because type parameters are
2210                         // trivially WF, but also we *should*, to avoid exposing
2211                         // users who never wrote `where Type:,` themselves, to
2212                         // compiler/tooling bugs from not handling WF predicates.
2213                     } else {
2214                         let span = bound_pred.bounded_ty.span;
2215                         let re_root_empty = tcx.lifetimes.re_root_empty;
2216                         let predicate = ty::Binder::bind_with_vars(
2217                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2218                                 ty,
2219                                 re_root_empty,
2220                             )),
2221                             bound_vars,
2222                         );
2223                         predicates.insert((predicate.to_predicate(tcx), span));
2224                     }
2225                 }
2226
2227                 for bound in bound_pred.bounds.iter() {
2228                     match bound {
2229                         hir::GenericBound::Trait(poly_trait_ref, modifier) => {
2230                             let constness = match modifier {
2231                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2232                                 hir::TraitBoundModifier::None => constness,
2233                                 // We ignore `where T: ?Sized`, it is already part of
2234                                 // type parameter `T`.
2235                                 hir::TraitBoundModifier::Maybe => continue,
2236                             };
2237
2238                             let mut bounds = Bounds::default();
2239                             let _ = <dyn AstConv<'_>>::instantiate_poly_trait_ref(
2240                                 &icx,
2241                                 &poly_trait_ref.trait_ref,
2242                                 poly_trait_ref.span,
2243                                 constness,
2244                                 ty,
2245                                 &mut bounds,
2246                                 false,
2247                             );
2248                             predicates.extend(bounds.predicates(tcx, ty));
2249                         }
2250
2251                         &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2252                             let mut bounds = Bounds::default();
2253                             <dyn AstConv<'_>>::instantiate_lang_item_trait_ref(
2254                                 &icx,
2255                                 lang_item,
2256                                 span,
2257                                 hir_id,
2258                                 args,
2259                                 ty,
2260                                 &mut bounds,
2261                             );
2262                             predicates.extend(bounds.predicates(tcx, ty));
2263                         }
2264
2265                         hir::GenericBound::Unsized(_) => {}
2266
2267                         hir::GenericBound::Outlives(lifetime) => {
2268                             let region =
2269                                 <dyn AstConv<'_>>::ast_region_to_region(&icx, lifetime, None);
2270                             predicates.insert((
2271                                 ty::Binder::bind_with_vars(
2272                                     ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2273                                         ty, region,
2274                                     )),
2275                                     bound_vars,
2276                                 )
2277                                 .to_predicate(tcx),
2278                                 lifetime.span,
2279                             ));
2280                         }
2281                     }
2282                 }
2283             }
2284
2285             hir::WherePredicate::RegionPredicate(region_pred) => {
2286                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2287                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2288                     let (r2, span) = match bound {
2289                         hir::GenericBound::Outlives(lt) => {
2290                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2291                         }
2292                         _ => bug!(),
2293                     };
2294                     let pred = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
2295                         .to_predicate(icx.tcx);
2296
2297                     (pred, span)
2298                 }))
2299             }
2300
2301             hir::WherePredicate::EqPredicate(..) => {
2302                 // FIXME(#20041)
2303             }
2304         }
2305     }
2306
2307     if tcx.features().const_evaluatable_checked {
2308         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2309     }
2310
2311     let mut predicates: Vec<_> = predicates.into_iter().collect();
2312
2313     // Subtle: before we store the predicates into the tcx, we
2314     // sort them so that predicates like `T: Foo<Item=U>` come
2315     // before uses of `U`.  This avoids false ambiguity errors
2316     // in trait checking. See `setup_constraining_predicates`
2317     // for details.
2318     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2319         let self_ty = tcx.type_of(def_id);
2320         let trait_ref = tcx.impl_trait_ref(def_id);
2321         cgp::setup_constraining_predicates(
2322             tcx,
2323             &mut predicates,
2324             trait_ref,
2325             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2326         );
2327     }
2328
2329     let result = ty::GenericPredicates {
2330         parent: generics.parent,
2331         predicates: tcx.arena.alloc_from_iter(predicates),
2332     };
2333     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2334     result
2335 }
2336
2337 fn const_evaluatable_predicates_of<'tcx>(
2338     tcx: TyCtxt<'tcx>,
2339     def_id: LocalDefId,
2340 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2341     struct ConstCollector<'tcx> {
2342         tcx: TyCtxt<'tcx>,
2343         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2344     }
2345
2346     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2347         type Map = Map<'tcx>;
2348
2349         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
2350             intravisit::NestedVisitorMap::None
2351         }
2352
2353         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2354             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2355             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2356             if let ty::ConstKind::Unevaluated(uv) = ct.val {
2357                 assert_eq!(uv.promoted, None);
2358                 let span = self.tcx.hir().span(c.hir_id);
2359                 self.preds.insert((
2360                     ty::PredicateKind::ConstEvaluatable(uv.def, uv.substs).to_predicate(self.tcx),
2361                     span,
2362                 ));
2363             }
2364         }
2365
2366         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2367             // Do not look into const param defaults,
2368             // these get checked when they are actually instantiated.
2369             //
2370             // We do not want the following to error:
2371             //
2372             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2373             //     struct Bar<const N: usize>(Foo<N, 3>);
2374         }
2375     }
2376
2377     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2378     let node = tcx.hir().get(hir_id);
2379
2380     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2381     if let hir::Node::Item(item) = node {
2382         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2383             if let Some(of_trait) = &impl_.of_trait {
2384                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2385                 collector.visit_trait_ref(of_trait);
2386             }
2387
2388             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2389             collector.visit_ty(impl_.self_ty);
2390         }
2391     }
2392
2393     if let Some(generics) = node.generics() {
2394         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2395         collector.visit_generics(generics);
2396     }
2397
2398     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2399         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2400         collector.visit_fn_decl(fn_sig.decl);
2401     }
2402     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2403
2404     collector.preds
2405 }
2406
2407 fn trait_explicit_predicates_and_bounds(
2408     tcx: TyCtxt<'_>,
2409     def_id: LocalDefId,
2410 ) -> ty::GenericPredicates<'_> {
2411     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2412     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2413 }
2414
2415 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2416     let def_kind = tcx.def_kind(def_id);
2417     if let DefKind::Trait = def_kind {
2418         // Remove bounds on associated types from the predicates, they will be
2419         // returned by `explicit_item_bounds`.
2420         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2421         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2422
2423         let is_assoc_item_ty = |ty: Ty<'_>| {
2424             // For a predicate from a where clause to become a bound on an
2425             // associated type:
2426             // * It must use the identity substs of the item.
2427             //     * Since any generic parameters on the item are not in scope,
2428             //       this means that the item is not a GAT, and its identity
2429             //       substs are the same as the trait's.
2430             // * It must be an associated type for this trait (*not* a
2431             //   supertrait).
2432             if let ty::Projection(projection) = ty.kind() {
2433                 projection.substs == trait_identity_substs
2434                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2435             } else {
2436                 false
2437             }
2438         };
2439
2440         let predicates: Vec<_> = predicates_and_bounds
2441             .predicates
2442             .iter()
2443             .copied()
2444             .filter(|(pred, _)| match pred.kind().skip_binder() {
2445                 ty::PredicateKind::Trait(tr, _) => !is_assoc_item_ty(tr.self_ty()),
2446                 ty::PredicateKind::Projection(proj) => {
2447                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2448                 }
2449                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2450                 _ => true,
2451             })
2452             .collect();
2453         if predicates.len() == predicates_and_bounds.predicates.len() {
2454             predicates_and_bounds
2455         } else {
2456             ty::GenericPredicates {
2457                 parent: predicates_and_bounds.parent,
2458                 predicates: tcx.arena.alloc_slice(&predicates),
2459             }
2460         }
2461     } else {
2462         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2463             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2464             if let Some(_) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
2465                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2466                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2467                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2468                 //
2469                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2470                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2471                 //        ^^^                                             explicit_predicates_of on
2472                 //        parent item we dont have set as the
2473                 //        parent of generics returned by `generics_of`
2474                 //
2475                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2476                 let item_id = tcx.hir().get_parent_item(hir_id);
2477                 let item_def_id = tcx.hir().local_def_id(item_id).to_def_id();
2478                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2479                 return tcx.explicit_predicates_of(item_def_id);
2480             }
2481         }
2482         gather_explicit_predicates_of(tcx, def_id)
2483     }
2484 }
2485
2486 /// Converts a specific `GenericBound` from the AST into a set of
2487 /// predicates that apply to the self type. A vector is returned
2488 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2489 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2490 /// and `<T as Bar>::X == i32`).
2491 fn predicates_from_bound<'tcx>(
2492     astconv: &dyn AstConv<'tcx>,
2493     param_ty: Ty<'tcx>,
2494     bound: &'tcx hir::GenericBound<'tcx>,
2495     constness: hir::Constness,
2496 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2497     match *bound {
2498         hir::GenericBound::Trait(ref tr, modifier) => {
2499             let constness = match modifier {
2500                 hir::TraitBoundModifier::Maybe => return vec![],
2501                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2502                 hir::TraitBoundModifier::None => constness,
2503             };
2504
2505             let mut bounds = Bounds::default();
2506             let _ = astconv.instantiate_poly_trait_ref(
2507                 &tr.trait_ref,
2508                 tr.span,
2509                 constness,
2510                 param_ty,
2511                 &mut bounds,
2512                 false,
2513             );
2514             bounds.predicates(astconv.tcx(), param_ty)
2515         }
2516         hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
2517             let mut bounds = Bounds::default();
2518             astconv.instantiate_lang_item_trait_ref(
2519                 lang_item,
2520                 span,
2521                 hir_id,
2522                 args,
2523                 param_ty,
2524                 &mut bounds,
2525             );
2526             bounds.predicates(astconv.tcx(), param_ty)
2527         }
2528         hir::GenericBound::Unsized(_) => vec![],
2529         hir::GenericBound::Outlives(ref lifetime) => {
2530             let region = astconv.ast_region_to_region(lifetime, None);
2531             let pred = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2532                 .to_predicate(astconv.tcx());
2533             vec![(pred, lifetime.span)]
2534         }
2535     }
2536 }
2537
2538 fn compute_sig_of_foreign_fn_decl<'tcx>(
2539     tcx: TyCtxt<'tcx>,
2540     def_id: DefId,
2541     decl: &'tcx hir::FnDecl<'tcx>,
2542     abi: abi::Abi,
2543     ident: Ident,
2544 ) -> ty::PolyFnSig<'tcx> {
2545     let unsafety = if abi == abi::Abi::RustIntrinsic {
2546         intrinsic_operation_unsafety(tcx.item_name(def_id))
2547     } else {
2548         hir::Unsafety::Unsafe
2549     };
2550     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2551     let fty = <dyn AstConv<'_>>::ty_of_fn(
2552         &ItemCtxt::new(tcx, def_id),
2553         hir_id,
2554         unsafety,
2555         abi,
2556         decl,
2557         &hir::Generics::empty(),
2558         Some(ident.span),
2559         None,
2560     );
2561
2562     // Feature gate SIMD types in FFI, since I am not sure that the
2563     // ABIs are handled at all correctly. -huonw
2564     if abi != abi::Abi::RustIntrinsic
2565         && abi != abi::Abi::PlatformIntrinsic
2566         && !tcx.features().simd_ffi
2567     {
2568         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2569             if ty.is_simd() {
2570                 let snip = tcx
2571                     .sess
2572                     .source_map()
2573                     .span_to_snippet(ast_ty.span)
2574                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2575                 tcx.sess
2576                     .struct_span_err(
2577                         ast_ty.span,
2578                         &format!(
2579                             "use of SIMD type{} in FFI is highly experimental and \
2580                              may result in invalid code",
2581                             snip
2582                         ),
2583                     )
2584                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2585                     .emit();
2586             }
2587         };
2588         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2589             check(&input, ty)
2590         }
2591         if let hir::FnRetTy::Return(ref ty) = decl.output {
2592             check(&ty, fty.output().skip_binder())
2593         }
2594     }
2595
2596     fty
2597 }
2598
2599 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2600     match tcx.hir().get_if_local(def_id) {
2601         Some(Node::ForeignItem(..)) => true,
2602         Some(_) => false,
2603         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2604     }
2605 }
2606
2607 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2608     match tcx.hir().get_if_local(def_id) {
2609         Some(
2610             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2611             | Node::ForeignItem(&hir::ForeignItem {
2612                 kind: hir::ForeignItemKind::Static(_, mutbl),
2613                 ..
2614             }),
2615         ) => Some(mutbl),
2616         Some(_) => None,
2617         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2618     }
2619 }
2620
2621 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2622     match tcx.hir().get_if_local(def_id) {
2623         Some(Node::Expr(&rustc_hir::Expr {
2624             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2625             ..
2626         })) => tcx.hir().body(body_id).generator_kind(),
2627         Some(_) => None,
2628         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2629     }
2630 }
2631
2632 fn from_target_feature(
2633     tcx: TyCtxt<'_>,
2634     id: DefId,
2635     attr: &ast::Attribute,
2636     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2637     target_features: &mut Vec<Symbol>,
2638 ) {
2639     let list = match attr.meta_item_list() {
2640         Some(list) => list,
2641         None => return,
2642     };
2643     let bad_item = |span| {
2644         let msg = "malformed `target_feature` attribute input";
2645         let code = "enable = \"..\"".to_owned();
2646         tcx.sess
2647             .struct_span_err(span, &msg)
2648             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2649             .emit();
2650     };
2651     let rust_features = tcx.features();
2652     for item in list {
2653         // Only `enable = ...` is accepted in the meta-item list.
2654         if !item.has_name(sym::enable) {
2655             bad_item(item.span());
2656             continue;
2657         }
2658
2659         // Must be of the form `enable = "..."` (a string).
2660         let value = match item.value_str() {
2661             Some(value) => value,
2662             None => {
2663                 bad_item(item.span());
2664                 continue;
2665             }
2666         };
2667
2668         // We allow comma separation to enable multiple features.
2669         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2670             let feature_gate = match supported_target_features.get(feature) {
2671                 Some(g) => g,
2672                 None => {
2673                     let msg =
2674                         format!("the feature named `{}` is not valid for this target", feature);
2675                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2676                     err.span_label(
2677                         item.span(),
2678                         format!("`{}` is not valid for this target", feature),
2679                     );
2680                     if let Some(stripped) = feature.strip_prefix('+') {
2681                         let valid = supported_target_features.contains_key(stripped);
2682                         if valid {
2683                             err.help("consider removing the leading `+` in the feature name");
2684                         }
2685                     }
2686                     err.emit();
2687                     return None;
2688                 }
2689             };
2690
2691             // Only allow features whose feature gates have been enabled.
2692             let allowed = match feature_gate.as_ref().copied() {
2693                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2694                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2695                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2696                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2697                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2698                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2699                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2700                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2701                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2702                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2703                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2704                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2705                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2706                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2707                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2708                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2709                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2710                 Some(name) => bug!("unknown target feature gate {}", name),
2711                 None => true,
2712             };
2713             if !allowed && id.is_local() {
2714                 feature_err(
2715                     &tcx.sess.parse_sess,
2716                     feature_gate.unwrap(),
2717                     item.span(),
2718                     &format!("the target feature `{}` is currently unstable", feature),
2719                 )
2720                 .emit();
2721             }
2722             Some(Symbol::intern(feature))
2723         }));
2724     }
2725 }
2726
2727 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2728     use rustc_middle::mir::mono::Linkage::*;
2729
2730     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2731     // applicable to variable declarations and may not really make sense for
2732     // Rust code in the first place but allow them anyway and trust that the
2733     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2734     // up in the future.
2735     //
2736     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2737     // and don't have to be, LLVM treats them as no-ops.
2738     match name {
2739         "appending" => Appending,
2740         "available_externally" => AvailableExternally,
2741         "common" => Common,
2742         "extern_weak" => ExternalWeak,
2743         "external" => External,
2744         "internal" => Internal,
2745         "linkonce" => LinkOnceAny,
2746         "linkonce_odr" => LinkOnceODR,
2747         "private" => Private,
2748         "weak" => WeakAny,
2749         "weak_odr" => WeakODR,
2750         _ => {
2751             let span = tcx.hir().span_if_local(def_id);
2752             if let Some(span) = span {
2753                 tcx.sess.span_fatal(span, "invalid linkage specified")
2754             } else {
2755                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2756             }
2757         }
2758     }
2759 }
2760
2761 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2762     let attrs = tcx.get_attrs(id);
2763
2764     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2765     if tcx.should_inherit_track_caller(id) {
2766         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2767     }
2768
2769     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2770
2771     let mut inline_span = None;
2772     let mut link_ordinal_span = None;
2773     let mut no_sanitize_span = None;
2774     for attr in attrs.iter() {
2775         if tcx.sess.check_name(attr, sym::cold) {
2776             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2777         } else if tcx.sess.check_name(attr, sym::rustc_allocator) {
2778             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2779         } else if tcx.sess.check_name(attr, sym::unwind) {
2780             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2781         } else if tcx.sess.check_name(attr, sym::ffi_returns_twice) {
2782             if tcx.is_foreign_item(id) {
2783                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2784             } else {
2785                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2786                 struct_span_err!(
2787                     tcx.sess,
2788                     attr.span,
2789                     E0724,
2790                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2791                 )
2792                 .emit();
2793             }
2794         } else if tcx.sess.check_name(attr, sym::ffi_pure) {
2795             if tcx.is_foreign_item(id) {
2796                 if attrs.iter().any(|a| tcx.sess.check_name(a, sym::ffi_const)) {
2797                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2798                     struct_span_err!(
2799                         tcx.sess,
2800                         attr.span,
2801                         E0757,
2802                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2803                     )
2804                     .emit();
2805                 } else {
2806                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2807                 }
2808             } else {
2809                 // `#[ffi_pure]` is only allowed on foreign functions
2810                 struct_span_err!(
2811                     tcx.sess,
2812                     attr.span,
2813                     E0755,
2814                     "`#[ffi_pure]` may only be used on foreign functions"
2815                 )
2816                 .emit();
2817             }
2818         } else if tcx.sess.check_name(attr, sym::ffi_const) {
2819             if tcx.is_foreign_item(id) {
2820                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2821             } else {
2822                 // `#[ffi_const]` is only allowed on foreign functions
2823                 struct_span_err!(
2824                     tcx.sess,
2825                     attr.span,
2826                     E0756,
2827                     "`#[ffi_const]` may only be used on foreign functions"
2828                 )
2829                 .emit();
2830             }
2831         } else if tcx.sess.check_name(attr, sym::rustc_allocator_nounwind) {
2832             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2833         } else if tcx.sess.check_name(attr, sym::naked) {
2834             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2835         } else if tcx.sess.check_name(attr, sym::no_mangle) {
2836             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2837         } else if tcx.sess.check_name(attr, sym::no_coverage) {
2838             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2839         } else if tcx.sess.check_name(attr, sym::rustc_std_internal_symbol) {
2840             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2841         } else if tcx.sess.check_name(attr, sym::used) {
2842             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2843         } else if tcx.sess.check_name(attr, sym::cmse_nonsecure_entry) {
2844             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2845                 struct_span_err!(
2846                     tcx.sess,
2847                     attr.span,
2848                     E0776,
2849                     "`#[cmse_nonsecure_entry]` requires C ABI"
2850                 )
2851                 .emit();
2852             }
2853             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2854                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2855                     .emit();
2856             }
2857             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2858         } else if tcx.sess.check_name(attr, sym::thread_local) {
2859             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2860         } else if tcx.sess.check_name(attr, sym::track_caller) {
2861             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2862                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2863                     .emit();
2864             }
2865             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2866         } else if tcx.sess.check_name(attr, sym::export_name) {
2867             if let Some(s) = attr.value_str() {
2868                 if s.as_str().contains('\0') {
2869                     // `#[export_name = ...]` will be converted to a null-terminated string,
2870                     // so it may not contain any null characters.
2871                     struct_span_err!(
2872                         tcx.sess,
2873                         attr.span,
2874                         E0648,
2875                         "`export_name` may not contain null characters"
2876                     )
2877                     .emit();
2878                 }
2879                 codegen_fn_attrs.export_name = Some(s);
2880             }
2881         } else if tcx.sess.check_name(attr, sym::target_feature) {
2882             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2883                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2884                     // The `#[target_feature]` attribute is allowed on
2885                     // WebAssembly targets on all functions, including safe
2886                     // ones. Other targets require that `#[target_feature]` is
2887                     // only applied to unsafe funtions (pending the
2888                     // `target_feature_11` feature) because on most targets
2889                     // execution of instructions that are not supported is
2890                     // considered undefined behavior. For WebAssembly which is a
2891                     // 100% safe target at execution time it's not possible to
2892                     // execute undefined instructions, and even if a future
2893                     // feature was added in some form for this it would be a
2894                     // deterministic trap. There is no undefined behavior when
2895                     // executing WebAssembly so `#[target_feature]` is allowed
2896                     // on safe functions (but again, only for WebAssembly)
2897                     //
2898                     // Note that this is also allowed if `actually_rustdoc` so
2899                     // if a target is documenting some wasm-specific code then
2900                     // it's not spuriously denied.
2901                 } else if !tcx.features().target_feature_11 {
2902                     let mut err = feature_err(
2903                         &tcx.sess.parse_sess,
2904                         sym::target_feature_11,
2905                         attr.span,
2906                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2907                     );
2908                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2909                     err.emit();
2910                 } else if let Some(local_id) = id.as_local() {
2911                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2912                 }
2913             }
2914             from_target_feature(
2915                 tcx,
2916                 id,
2917                 attr,
2918                 &supported_target_features,
2919                 &mut codegen_fn_attrs.target_features,
2920             );
2921         } else if tcx.sess.check_name(attr, sym::linkage) {
2922             if let Some(val) = attr.value_str() {
2923                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2924             }
2925         } else if tcx.sess.check_name(attr, sym::link_section) {
2926             if let Some(val) = attr.value_str() {
2927                 if val.as_str().bytes().any(|b| b == 0) {
2928                     let msg = format!(
2929                         "illegal null byte in link_section \
2930                          value: `{}`",
2931                         &val
2932                     );
2933                     tcx.sess.span_err(attr.span, &msg);
2934                 } else {
2935                     codegen_fn_attrs.link_section = Some(val);
2936                 }
2937             }
2938         } else if tcx.sess.check_name(attr, sym::link_name) {
2939             codegen_fn_attrs.link_name = attr.value_str();
2940         } else if tcx.sess.check_name(attr, sym::link_ordinal) {
2941             link_ordinal_span = Some(attr.span);
2942             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2943                 codegen_fn_attrs.link_ordinal = ordinal;
2944             }
2945         } else if tcx.sess.check_name(attr, sym::no_sanitize) {
2946             no_sanitize_span = Some(attr.span);
2947             if let Some(list) = attr.meta_item_list() {
2948                 for item in list.iter() {
2949                     if item.has_name(sym::address) {
2950                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2951                     } else if item.has_name(sym::memory) {
2952                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2953                     } else if item.has_name(sym::thread) {
2954                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2955                     } else if item.has_name(sym::hwaddress) {
2956                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2957                     } else {
2958                         tcx.sess
2959                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2960                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
2961                             .emit();
2962                     }
2963                 }
2964             }
2965         } else if tcx.sess.check_name(attr, sym::instruction_set) {
2966             codegen_fn_attrs.instruction_set = match attr.meta().map(|i| i.kind) {
2967                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2968                     [NestedMetaItem::MetaItem(set)] => {
2969                         let segments =
2970                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2971                         match segments.as_slice() {
2972                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2973                                 if !tcx.sess.target.has_thumb_interworking {
2974                                     struct_span_err!(
2975                                         tcx.sess.diagnostic(),
2976                                         attr.span,
2977                                         E0779,
2978                                         "target does not support `#[instruction_set]`"
2979                                     )
2980                                     .emit();
2981                                     None
2982                                 } else if segments[1] == sym::a32 {
2983                                     Some(InstructionSetAttr::ArmA32)
2984                                 } else if segments[1] == sym::t32 {
2985                                     Some(InstructionSetAttr::ArmT32)
2986                                 } else {
2987                                     unreachable!()
2988                                 }
2989                             }
2990                             _ => {
2991                                 struct_span_err!(
2992                                     tcx.sess.diagnostic(),
2993                                     attr.span,
2994                                     E0779,
2995                                     "invalid instruction set specified",
2996                                 )
2997                                 .emit();
2998                                 None
2999                             }
3000                         }
3001                     }
3002                     [] => {
3003                         struct_span_err!(
3004                             tcx.sess.diagnostic(),
3005                             attr.span,
3006                             E0778,
3007                             "`#[instruction_set]` requires an argument"
3008                         )
3009                         .emit();
3010                         None
3011                     }
3012                     _ => {
3013                         struct_span_err!(
3014                             tcx.sess.diagnostic(),
3015                             attr.span,
3016                             E0779,
3017                             "cannot specify more than one instruction set"
3018                         )
3019                         .emit();
3020                         None
3021                     }
3022                 },
3023                 _ => {
3024                     struct_span_err!(
3025                         tcx.sess.diagnostic(),
3026                         attr.span,
3027                         E0778,
3028                         "must specify an instruction set"
3029                     )
3030                     .emit();
3031                     None
3032                 }
3033             };
3034         } else if tcx.sess.check_name(attr, sym::repr) {
3035             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3036                 Some(items) => match items.as_slice() {
3037                     [item] => match item.name_value_literal() {
3038                         Some((sym::align, literal)) => {
3039                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3040
3041                             match alignment {
3042                                 Ok(align) => Some(align),
3043                                 Err(msg) => {
3044                                     struct_span_err!(
3045                                         tcx.sess.diagnostic(),
3046                                         attr.span,
3047                                         E0589,
3048                                         "invalid `repr(align)` attribute: {}",
3049                                         msg
3050                                     )
3051                                     .emit();
3052
3053                                     None
3054                                 }
3055                             }
3056                         }
3057                         _ => None,
3058                     },
3059                     [] => None,
3060                     _ => None,
3061                 },
3062                 None => None,
3063             };
3064         }
3065     }
3066
3067     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3068         if !attr.has_name(sym::inline) {
3069             return ia;
3070         }
3071         match attr.meta().map(|i| i.kind) {
3072             Some(MetaItemKind::Word) => {
3073                 tcx.sess.mark_attr_used(attr);
3074                 InlineAttr::Hint
3075             }
3076             Some(MetaItemKind::List(ref items)) => {
3077                 tcx.sess.mark_attr_used(attr);
3078                 inline_span = Some(attr.span);
3079                 if items.len() != 1 {
3080                     struct_span_err!(
3081                         tcx.sess.diagnostic(),
3082                         attr.span,
3083                         E0534,
3084                         "expected one argument"
3085                     )
3086                     .emit();
3087                     InlineAttr::None
3088                 } else if list_contains_name(&items[..], sym::always) {
3089                     InlineAttr::Always
3090                 } else if list_contains_name(&items[..], sym::never) {
3091                     InlineAttr::Never
3092                 } else {
3093                     struct_span_err!(
3094                         tcx.sess.diagnostic(),
3095                         items[0].span(),
3096                         E0535,
3097                         "invalid argument"
3098                     )
3099                     .emit();
3100
3101                     InlineAttr::None
3102                 }
3103             }
3104             Some(MetaItemKind::NameValue(_)) => ia,
3105             None => ia,
3106         }
3107     });
3108
3109     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3110         if !attr.has_name(sym::optimize) {
3111             return ia;
3112         }
3113         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3114         match attr.meta().map(|i| i.kind) {
3115             Some(MetaItemKind::Word) => {
3116                 err(attr.span, "expected one argument");
3117                 ia
3118             }
3119             Some(MetaItemKind::List(ref items)) => {
3120                 tcx.sess.mark_attr_used(attr);
3121                 inline_span = Some(attr.span);
3122                 if items.len() != 1 {
3123                     err(attr.span, "expected one argument");
3124                     OptimizeAttr::None
3125                 } else if list_contains_name(&items[..], sym::size) {
3126                     OptimizeAttr::Size
3127                 } else if list_contains_name(&items[..], sym::speed) {
3128                     OptimizeAttr::Speed
3129                 } else {
3130                     err(items[0].span(), "invalid argument");
3131                     OptimizeAttr::None
3132                 }
3133             }
3134             Some(MetaItemKind::NameValue(_)) => ia,
3135             None => ia,
3136         }
3137     });
3138
3139     // #73631: closures inherit `#[target_feature]` annotations
3140     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3141         let owner_id = tcx.parent(id).expect("closure should have a parent");
3142         codegen_fn_attrs
3143             .target_features
3144             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3145     }
3146
3147     // If a function uses #[target_feature] it can't be inlined into general
3148     // purpose functions as they wouldn't have the right target features
3149     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3150     // respected.
3151     if !codegen_fn_attrs.target_features.is_empty() {
3152         if codegen_fn_attrs.inline == InlineAttr::Always {
3153             if let Some(span) = inline_span {
3154                 tcx.sess.span_err(
3155                     span,
3156                     "cannot use `#[inline(always)]` with \
3157                      `#[target_feature]`",
3158                 );
3159             }
3160         }
3161     }
3162
3163     if !codegen_fn_attrs.no_sanitize.is_empty() {
3164         if codegen_fn_attrs.inline == InlineAttr::Always {
3165             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3166                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3167                 tcx.struct_span_lint_hir(
3168                     lint::builtin::INLINE_NO_SANITIZE,
3169                     hir_id,
3170                     no_sanitize_span,
3171                     |lint| {
3172                         lint.build("`no_sanitize` will have no effect after inlining")
3173                             .span_note(inline_span, "inlining requested here")
3174                             .emit();
3175                     },
3176                 )
3177             }
3178         }
3179     }
3180
3181     // Weak lang items have the same semantics as "std internal" symbols in the
3182     // sense that they're preserved through all our LTO passes and only
3183     // strippable by the linker.
3184     //
3185     // Additionally weak lang items have predetermined symbol names.
3186     if tcx.is_weak_lang_item(id) {
3187         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3188     }
3189     let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
3190     if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {
3191         codegen_fn_attrs.export_name = Some(name);
3192         codegen_fn_attrs.link_name = Some(name);
3193     }
3194     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3195
3196     // Internal symbols to the standard library all have no_mangle semantics in
3197     // that they have defined symbol names present in the function name. This
3198     // also applies to weak symbols where they all have known symbol names.
3199     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3200         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3201     }
3202
3203     codegen_fn_attrs
3204 }
3205
3206 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3207 /// applied to the method prototype.
3208 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3209     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3210         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
3211             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
3212                 if let Some(trait_item) = tcx
3213                     .associated_items(trait_def_id)
3214                     .filter_by_name_unhygienic(impl_item.ident.name)
3215                     .find(move |trait_item| {
3216                         trait_item.kind == ty::AssocKind::Fn
3217                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
3218                     })
3219                 {
3220                     return tcx
3221                         .codegen_fn_attrs(trait_item.def_id)
3222                         .flags
3223                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3224                 }
3225             }
3226         }
3227     }
3228
3229     false
3230 }
3231
3232 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
3233     use rustc_ast::{Lit, LitIntType, LitKind};
3234     let meta_item_list = attr.meta_item_list();
3235     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3236     let sole_meta_list = match meta_item_list {
3237         Some([item]) => item.literal(),
3238         _ => None,
3239     };
3240     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3241         if *ordinal <= usize::MAX as u128 {
3242             Some(*ordinal as usize)
3243         } else {
3244             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3245             tcx.sess
3246                 .struct_span_err(attr.span, &msg)
3247                 .note("the value may not exceed `usize::MAX`")
3248                 .emit();
3249             None
3250         }
3251     } else {
3252         tcx.sess
3253             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3254             .note("an unsuffixed integer value, e.g., `1`, is expected")
3255             .emit();
3256         None
3257     }
3258 }
3259
3260 fn check_link_name_xor_ordinal(
3261     tcx: TyCtxt<'_>,
3262     codegen_fn_attrs: &CodegenFnAttrs,
3263     inline_span: Option<Span>,
3264 ) {
3265     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3266         return;
3267     }
3268     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3269     if let Some(span) = inline_span {
3270         tcx.sess.span_err(span, msg);
3271     } else {
3272         tcx.sess.err(msg);
3273     }
3274 }
3275
3276 /// Checks the function annotated with `#[target_feature]` is not a safe
3277 /// trait method implementation, reporting an error if it is.
3278 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3279     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3280     let node = tcx.hir().get(hir_id);
3281     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3282         let parent_id = tcx.hir().get_parent_item(hir_id);
3283         let parent_item = tcx.hir().expect_item(parent_id);
3284         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3285             tcx.sess
3286                 .struct_span_err(
3287                     attr_span,
3288                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3289                 )
3290                 .span_label(attr_span, "cannot be applied to safe trait method")
3291                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3292                 .emit();
3293         }
3294     }
3295 }