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