src/librustc_typeck/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  18 use crate::check::intrinsic::intrinsic_operation_unsafety;
  19 use crate::constrained_generic_params as cgp;
  20 use crate::middle::resolve_lifetime as rl;
  21 use rustc_ast::ast;
  22 use rustc_ast::ast::MetaItemKind;
  23 use rustc_attr::{list_contains_name, mark_used, InlineAttr, OptimizeAttr};
  24 use rustc_data_structures::captures::Captures;
  25 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
  26 use rustc_errors::{struct_span_err, Applicability};
  27 use rustc_hir as hir;
  28 use rustc_hir::def::{CtorKind, DefKind, Res};
  29 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
  30 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  31 use rustc_hir::weak_lang_items;
  32 use rustc_hir::{GenericParamKind, HirId, Node};
  33 use rustc_middle::hir::map::blocks::FnLikeNode;
  34 use rustc_middle::hir::map::Map;
  35 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  36 use rustc_middle::mir::mono::Linkage;
  37 use rustc_middle::ty::query::Providers;
  38 use rustc_middle::ty::subst::InternalSubsts;
  39 use rustc_middle::ty::util::Discr;
  40 use rustc_middle::ty::util::IntTypeExt;
  41 use rustc_middle::ty::{self, AdtKind, Const, ToPolyTraitRef, Ty, TyCtxt};
  42 use rustc_middle::ty::{ReprOptions, ToPredicate, WithConstness};
  43 use rustc_session::config::SanitizerSet;
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::abi;
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50
  51 mod type_of;
  52
  53 struct OnlySelfBounds(bool);
  54
  55 ///////////////////////////////////////////////////////////////////////////
  56 // Main entry point
  57
  58 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  59     tcx.hir().visit_item_likes_in_module(
  60         module_def_id,
  61         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  62     );
  63 }
  64
  65 pub fn provide(providers: &mut Providers) {
  66     *providers = Providers {
  67         opt_const_param_of: type_of::opt_const_param_of,
  68         type_of: type_of::type_of,
  69         generics_of,
  70         predicates_of,
  71         predicates_defined_on,
  72         explicit_predicates_of,
  73         super_predicates_of,
  74         type_param_predicates,
  75         trait_def,
  76         adt_def,
  77         fn_sig,
  78         impl_trait_ref,
  79         impl_polarity,
  80         is_foreign_item,
  81         static_mutability,
  82         generator_kind,
  83         codegen_fn_attrs,
  84         collect_mod_item_types,
  85         ..*providers
  86     };
  87 }
  88
  89 ///////////////////////////////////////////////////////////////////////////
  90
  91 /// Context specific to some particular item. This is what implements
  92 /// `AstConv`. It has information about the predicates that are defined
  93 /// on the trait. Unfortunately, this predicate information is
  94 /// available in various different forms at various points in the
  95 /// process. So we can't just store a pointer to e.g., the AST or the
  96 /// parsed ty form, we have to be more flexible. To this end, the
  97 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  98 /// `get_type_parameter_bounds` requests, drawing the information from
  99 /// the AST (`hir::Generics`), recursively.
 100 pub struct ItemCtxt<'tcx> {
 101     tcx: TyCtxt<'tcx>,
 102     item_def_id: DefId,
 103 }
 104
 105 ///////////////////////////////////////////////////////////////////////////
 106
 107 #[derive(Default)]
 108 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 109
 110 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 111     type Map = intravisit::ErasedMap<'v>;
 112
 113     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 114         NestedVisitorMap::None
 115     }
 116     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 117         if let hir::TyKind::Infer = t.kind {
 118             self.0.push(t.span);
 119         }
 120         intravisit::walk_ty(self, t)
 121     }
 122 }
 123
 124 struct CollectItemTypesVisitor<'tcx> {
 125     tcx: TyCtxt<'tcx>,
 126 }
 127
 128 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 129 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 130 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 131 crate fn placeholder_type_error(
 132     tcx: TyCtxt<'tcx>,
 133     span: Option<Span>,
 134     generics: &[hir::GenericParam<'_>],
 135     placeholder_types: Vec<Span>,
 136     suggest: bool,
 137 ) {
 138     if placeholder_types.is_empty() {
 139         return;
 140     }
 141
 142     let type_name = generics.next_type_param_name(None);
 143     let mut sugg: Vec<_> =
 144         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 145
 146     if generics.is_empty() {
 147         if let Some(span) = span {
 148             sugg.push((span, format!("<{}>", type_name)));
 149         }
 150     } else if let Some(arg) = generics.iter().find(|arg| match arg.name {
 151         hir::ParamName::Plain(Ident { name: kw::Underscore, .. }) => true,
 152         _ => false,
 153     }) {
 154         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 155         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 156         sugg.push((arg.span, (*type_name).to_string()));
 157     } else {
 158         let last = generics.iter().last().unwrap();
 159         sugg.push((
 160             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 161             last.bounds_span().unwrap_or(last.span).shrink_to_hi(),
 162             format!(", {}", type_name),
 163         ));
 164     }
 165
 166     let mut err = bad_placeholder_type(tcx, placeholder_types);
 167     if suggest {
 168         err.multipart_suggestion(
 169             "use type parameters instead",
 170             sugg,
 171             Applicability::HasPlaceholders,
 172         );
 173     }
 174     err.emit();
 175 }
 176
 177 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 178     let (generics, suggest) = match &item.kind {
 179         hir::ItemKind::Union(_, generics)
 180         | hir::ItemKind::Enum(_, generics)
 181         | hir::ItemKind::TraitAlias(generics, _)
 182         | hir::ItemKind::Trait(_, _, generics, ..)
 183         | hir::ItemKind::Impl { generics, .. }
 184         | hir::ItemKind::Struct(_, generics) => (generics, true),
 185         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 186         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 187         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 188         _ => return,
 189     };
 190
 191     let mut visitor = PlaceholderHirTyCollector::default();
 192     visitor.visit_item(item);
 193
 194     placeholder_type_error(tcx, Some(generics.span), &generics.params[..], visitor.0, suggest);
 195 }
 196
 197 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 198     type Map = Map<'tcx>;
 199
 200     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 201         NestedVisitorMap::OnlyBodies(self.tcx.hir())
 202     }
 203
 204     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 205         convert_item(self.tcx, item.hir_id);
 206         reject_placeholder_type_signatures_in_item(self.tcx, item);
 207         intravisit::walk_item(self, item);
 208     }
 209
 210     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 211         for param in generics.params {
 212             match param.kind {
 213                 hir::GenericParamKind::Lifetime { .. } => {}
 214                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 215                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 216                     self.tcx.ensure().type_of(def_id);
 217                 }
 218                 hir::GenericParamKind::Type { .. } => {}
 219                 hir::GenericParamKind::Const { .. } => {
 220                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 221                     self.tcx.ensure().type_of(def_id);
 222                 }
 223             }
 224         }
 225         intravisit::walk_generics(self, generics);
 226     }
 227
 228     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 229         if let hir::ExprKind::Closure(..) = expr.kind {
 230             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 231             self.tcx.ensure().generics_of(def_id);
 232             self.tcx.ensure().type_of(def_id);
 233         }
 234         intravisit::walk_expr(self, expr);
 235     }
 236
 237     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 238         convert_trait_item(self.tcx, trait_item.hir_id);
 239         intravisit::walk_trait_item(self, trait_item);
 240     }
 241
 242     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 243         convert_impl_item(self.tcx, impl_item.hir_id);
 244         intravisit::walk_impl_item(self, impl_item);
 245     }
 246 }
 247
 248 ///////////////////////////////////////////////////////////////////////////
 249 // Utility types and common code for the above passes.
 250
 251 fn bad_placeholder_type(
 252     tcx: TyCtxt<'tcx>,
 253     mut spans: Vec<Span>,
 254 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 255     spans.sort();
 256     let mut err = struct_span_err!(
 257         tcx.sess,
 258         spans.clone(),
 259         E0121,
 260         "the type placeholder `_` is not allowed within types on item signatures",
 261     );
 262     for span in spans {
 263         err.span_label(span, "not allowed in type signatures");
 264     }
 265     err
 266 }
 267
 268 impl ItemCtxt<'tcx> {
 269     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 270         ItemCtxt { tcx, item_def_id }
 271     }
 272
 273     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 274         AstConv::ast_ty_to_ty(self, ast_ty)
 275     }
 276
 277     pub fn hir_id(&self) -> hir::HirId {
 278         self.tcx.hir().as_local_hir_id(self.item_def_id.expect_local())
 279     }
 280
 281     pub fn node(&self) -> hir::Node<'tcx> {
 282         self.tcx.hir().get(self.hir_id())
 283     }
 284 }
 285
 286 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 287     fn tcx(&self) -> TyCtxt<'tcx> {
 288         self.tcx
 289     }
 290
 291     fn item_def_id(&self) -> Option<DefId> {
 292         Some(self.item_def_id)
 293     }
 294
 295     fn default_constness_for_trait_bounds(&self) -> hir::Constness {
 296         if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
 297             fn_like.constness()
 298         } else {
 299             hir::Constness::NotConst
 300         }
 301     }
 302
 303     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 304         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id.expect_local()))
 305     }
 306
 307     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 308         None
 309     }
 310
 311     fn allow_ty_infer(&self) -> bool {
 312         false
 313     }
 314
 315     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 316         self.tcx().ty_error_with_message(span, "bad_placeholder_type")
 317     }
 318
 319     fn ct_infer(
 320         &self,
 321         ty: Ty<'tcx>,
 322         _: Option<&ty::GenericParamDef>,
 323         span: Span,
 324     ) -> &'tcx Const<'tcx> {
 325         bad_placeholder_type(self.tcx(), vec![span]).emit();
 326         self.tcx().const_error(ty)
 327     }
 328
 329     fn projected_ty_from_poly_trait_ref(
 330         &self,
 331         span: Span,
 332         item_def_id: DefId,
 333         item_segment: &hir::PathSegment<'_>,
 334         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 335     ) -> Ty<'tcx> {
 336         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 337             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 338                 self,
 339                 self.tcx,
 340                 span,
 341                 item_def_id,
 342                 item_segment,
 343                 trait_ref.substs,
 344             );
 345             self.tcx().mk_projection(item_def_id, item_substs)
 346         } else {
 347             // There are no late-bound regions; we can just ignore the binder.
 348             let mut err = struct_span_err!(
 349                 self.tcx().sess,
 350                 span,
 351                 E0212,
 352                 "cannot extract an associated type from a higher-ranked trait bound \
 353                  in this context"
 354             );
 355
 356             match self.node() {
 357                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 358                     let item =
 359                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 360                     match &item.kind {
 361                         hir::ItemKind::Enum(_, generics)
 362                         | hir::ItemKind::Struct(_, generics)
 363                         | hir::ItemKind::Union(_, generics) => {
 364                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 365                             let (lt_sp, sugg) = match &generics.params[..] {
 366                                 [] => (generics.span, format!("<{}>", lt_name)),
 367                                 [bound, ..] => {
 368                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 369                                 }
 370                             };
 371                             let suggestions = vec![
 372                                 (lt_sp, sugg),
 373                                 (
 374                                     span,
 375                                     format!(
 376                                         "{}::{}",
 377                                         // Replace the existing lifetimes with a new named lifetime.
 378                                         self.tcx
 379                                             .replace_late_bound_regions(&poly_trait_ref, |_| {
 380                                                 self.tcx.mk_region(ty::ReEarlyBound(
 381                                                     ty::EarlyBoundRegion {
 382                                                         def_id: item_def_id,
 383                                                         index: 0,
 384                                                         name: Symbol::intern(&lt_name),
 385                                                     },
 386                                                 ))
 387                                             })
 388                                             .0,
 389                                         item_segment.ident
 390                                     ),
 391                                 ),
 392                             ];
 393                             err.multipart_suggestion(
 394                                 "use a fully qualified path with explicit lifetimes",
 395                                 suggestions,
 396                                 Applicability::MaybeIncorrect,
 397                             );
 398                         }
 399                         _ => {}
 400                     }
 401                 }
 402                 hir::Node::Item(hir::Item {
 403                     kind:
 404                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 405                     ..
 406                 }) => {}
 407                 hir::Node::Item(_)
 408                 | hir::Node::ForeignItem(_)
 409                 | hir::Node::TraitItem(_)
 410                 | hir::Node::ImplItem(_) => {
 411                     err.span_suggestion(
 412                         span,
 413                         "use a fully qualified path with inferred lifetimes",
 414                         format!(
 415                             "{}::{}",
 416                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 417                             self.tcx.anonymize_late_bound_regions(&poly_trait_ref).skip_binder(),
 418                             item_segment.ident
 419                         ),
 420                         Applicability::MaybeIncorrect,
 421                     );
 422                 }
 423                 _ => {}
 424             }
 425             err.emit();
 426             self.tcx().ty_error()
 427         }
 428     }
 429
 430     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 431         // Types in item signatures are not normalized to avoid undue dependencies.
 432         ty
 433     }
 434
 435     fn set_tainted_by_errors(&self) {
 436         // There's no obvious place to track this, so just let it go.
 437     }
 438
 439     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 440         // There's no place to record types from signatures?
 441     }
 442 }
 443
 444 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 445 fn get_new_lifetime_name<'tcx>(
 446     tcx: TyCtxt<'tcx>,
 447     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 448     generics: &hir::Generics<'tcx>,
 449 ) -> String {
 450     let existing_lifetimes = tcx
 451         .collect_referenced_late_bound_regions(&poly_trait_ref)
 452         .into_iter()
 453         .filter_map(|lt| {
 454             if let ty::BoundRegion::BrNamed(_, name) = lt {
 455                 Some(name.as_str().to_string())
 456             } else {
 457                 None
 458             }
 459         })
 460         .chain(generics.params.iter().filter_map(|param| {
 461             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 462                 Some(param.name.ident().as_str().to_string())
 463             } else {
 464                 None
 465             }
 466         }))
 467         .collect::<FxHashSet<String>>();
 468
 469     let a_to_z_repeat_n = |n| {
 470         (b'a'..=b'z').map(move |c| {
 471             let mut s = '\''.to_string();
 472             s.extend(std::iter::repeat(char::from(c)).take(n));
 473             s
 474         })
 475     };
 476
 477     // If all single char lifetime names are present, we wrap around and double the chars.
 478     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 479 }
 480
 481 /// Returns the predicates defined on `item_def_id` of the form
 482 /// `X: Foo` where `X` is the type parameter `def_id`.
 483 fn type_param_predicates(
 484     tcx: TyCtxt<'_>,
 485     (item_def_id, def_id): (DefId, LocalDefId),
 486 ) -> ty::GenericPredicates<'_> {
 487     use rustc_hir::*;
 488
 489     // In the AST, bounds can derive from two places. Either
 490     // written inline like `<T: Foo>` or in a where-clause like
 491     // `where T: Foo`.
 492
 493     let param_id = tcx.hir().as_local_hir_id(def_id);
 494     let param_owner = tcx.hir().ty_param_owner(param_id);
 495     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 496     let generics = tcx.generics_of(param_owner_def_id);
 497     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 498     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 499
 500     // Don't look for bounds where the type parameter isn't in scope.
 501     let parent = if item_def_id == param_owner_def_id.to_def_id() {
 502         None
 503     } else {
 504         tcx.generics_of(item_def_id).parent
 505     };
 506
 507     let mut result = parent
 508         .map(|parent| {
 509             let icx = ItemCtxt::new(tcx, parent);
 510             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id())
 511         })
 512         .unwrap_or_default();
 513     let mut extend = None;
 514
 515     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id.expect_local());
 516     let ast_generics = match tcx.hir().get(item_hir_id) {
 517         Node::TraitItem(item) => &item.generics,
 518
 519         Node::ImplItem(item) => &item.generics,
 520
 521         Node::Item(item) => {
 522             match item.kind {
 523                 ItemKind::Fn(.., ref generics, _)
 524                 | ItemKind::Impl { ref generics, .. }
 525                 | ItemKind::TyAlias(_, ref generics)
 526                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 527                 | ItemKind::Enum(_, ref generics)
 528                 | ItemKind::Struct(_, ref generics)
 529                 | ItemKind::Union(_, ref generics) => generics,
 530                 ItemKind::Trait(_, _, ref generics, ..) => {
 531                     // Implied `Self: Trait` and supertrait bounds.
 532                     if param_id == item_hir_id {
 533                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 534                         extend =
 535                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 536                     }
 537                     generics
 538                 }
 539                 _ => return result,
 540             }
 541         }
 542
 543         Node::ForeignItem(item) => match item.kind {
 544             ForeignItemKind::Fn(_, _, ref generics) => generics,
 545             _ => return result,
 546         },
 547
 548         _ => return result,
 549     };
 550
 551     let icx = ItemCtxt::new(tcx, item_def_id);
 552     let extra_predicates = extend.into_iter().chain(
 553         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 554             .into_iter()
 555             .filter(|(predicate, _)| match predicate.ignore_qualifiers(tcx).skip_binder().kind() {
 556                 ty::PredicateKind::Trait(data, _) => data.self_ty().is_param(index),
 557                 _ => false,
 558             }),
 559     );
 560     result.predicates =
 561         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 562     result
 563 }
 564
 565 impl ItemCtxt<'tcx> {
 566     /// Finds bounds from `hir::Generics`. This requires scanning through the
 567     /// AST. We do this to avoid having to convert *all* the bounds, which
 568     /// would create artificial cycles. Instead, we can only convert the
 569     /// bounds for a type parameter `X` if `X::Foo` is used.
 570     fn type_parameter_bounds_in_generics(
 571         &self,
 572         ast_generics: &'tcx hir::Generics<'tcx>,
 573         param_id: hir::HirId,
 574         ty: Ty<'tcx>,
 575         only_self_bounds: OnlySelfBounds,
 576     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 577         let constness = self.default_constness_for_trait_bounds();
 578         let from_ty_params = ast_generics
 579             .params
 580             .iter()
 581             .filter_map(|param| match param.kind {
 582                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 583                 _ => None,
 584             })
 585             .flat_map(|bounds| bounds.iter())
 586             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 587
 588         let from_where_clauses = ast_generics
 589             .where_clause
 590             .predicates
 591             .iter()
 592             .filter_map(|wp| match *wp {
 593                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 594                 _ => None,
 595             })
 596             .flat_map(|bp| {
 597                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 598                     Some(ty)
 599                 } else if !only_self_bounds.0 {
 600                     Some(self.to_ty(&bp.bounded_ty))
 601                 } else {
 602                     None
 603                 };
 604                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 605             })
 606             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 607
 608         from_ty_params.chain(from_where_clauses).collect()
 609     }
 610 }
 611
 612 /// Tests whether this is the AST for a reference to the type
 613 /// parameter with ID `param_id`. We use this so as to avoid running
 614 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 615 /// conversion of the type to avoid inducing unnecessary cycles.
 616 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 617     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 618         match path.res {
 619             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 620                 def_id == tcx.hir().local_def_id(param_id).to_def_id()
 621             }
 622             _ => false,
 623         }
 624     } else {
 625         false
 626     }
 627 }
 628
 629 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 630     let it = tcx.hir().expect_item(item_id);
 631     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 632     let def_id = tcx.hir().local_def_id(item_id);
 633     match it.kind {
 634         // These don't define types.
 635         hir::ItemKind::ExternCrate(_)
 636         | hir::ItemKind::Use(..)
 637         | hir::ItemKind::Mod(_)
 638         | hir::ItemKind::GlobalAsm(_) => {}
 639         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 640             for item in foreign_mod.items {
 641                 let def_id = tcx.hir().local_def_id(item.hir_id);
 642                 tcx.ensure().generics_of(def_id);
 643                 tcx.ensure().type_of(def_id);
 644                 tcx.ensure().predicates_of(def_id);
 645                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 646                     tcx.ensure().fn_sig(def_id);
 647                 }
 648             }
 649         }
 650         hir::ItemKind::Enum(ref enum_definition, _) => {
 651             tcx.ensure().generics_of(def_id);
 652             tcx.ensure().type_of(def_id);
 653             tcx.ensure().predicates_of(def_id);
 654             convert_enum_variant_types(tcx, def_id.to_def_id(), &enum_definition.variants);
 655         }
 656         hir::ItemKind::Impl { .. } => {
 657             tcx.ensure().generics_of(def_id);
 658             tcx.ensure().type_of(def_id);
 659             tcx.ensure().impl_trait_ref(def_id);
 660             tcx.ensure().predicates_of(def_id);
 661         }
 662         hir::ItemKind::Trait(..) => {
 663             tcx.ensure().generics_of(def_id);
 664             tcx.ensure().trait_def(def_id);
 665             tcx.at(it.span).super_predicates_of(def_id);
 666             tcx.ensure().predicates_of(def_id);
 667         }
 668         hir::ItemKind::TraitAlias(..) => {
 669             tcx.ensure().generics_of(def_id);
 670             tcx.at(it.span).super_predicates_of(def_id);
 671             tcx.ensure().predicates_of(def_id);
 672         }
 673         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 674             tcx.ensure().generics_of(def_id);
 675             tcx.ensure().type_of(def_id);
 676             tcx.ensure().predicates_of(def_id);
 677
 678             for f in struct_def.fields() {
 679                 let def_id = tcx.hir().local_def_id(f.hir_id);
 680                 tcx.ensure().generics_of(def_id);
 681                 tcx.ensure().type_of(def_id);
 682                 tcx.ensure().predicates_of(def_id);
 683             }
 684
 685             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 686                 convert_variant_ctor(tcx, ctor_hir_id);
 687             }
 688         }
 689
 690         // Desugared from `impl Trait`, so visited by the function's return type.
 691         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 692
 693         hir::ItemKind::OpaqueTy(..)
 694         | hir::ItemKind::TyAlias(..)
 695         | hir::ItemKind::Static(..)
 696         | hir::ItemKind::Const(..)
 697         | hir::ItemKind::Fn(..) => {
 698             tcx.ensure().generics_of(def_id);
 699             tcx.ensure().type_of(def_id);
 700             tcx.ensure().predicates_of(def_id);
 701             if let hir::ItemKind::Fn(..) = it.kind {
 702                 tcx.ensure().fn_sig(def_id);
 703             }
 704         }
 705     }
 706 }
 707
 708 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 709     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 710     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 711     tcx.ensure().generics_of(def_id);
 712
 713     match trait_item.kind {
 714         hir::TraitItemKind::Fn(..) => {
 715             tcx.ensure().type_of(def_id);
 716             tcx.ensure().fn_sig(def_id);
 717         }
 718
 719         hir::TraitItemKind::Const(.., Some(_)) => {
 720             tcx.ensure().type_of(def_id);
 721         }
 722
 723         hir::TraitItemKind::Const(..) | hir::TraitItemKind::Type(_, Some(_)) => {
 724             tcx.ensure().type_of(def_id);
 725             // Account for `const C: _;` and `type T = _;`.
 726             let mut visitor = PlaceholderHirTyCollector::default();
 727             visitor.visit_trait_item(trait_item);
 728             placeholder_type_error(tcx, None, &[], visitor.0, false);
 729         }
 730
 731         hir::TraitItemKind::Type(_, None) => {
 732             // #74612: Visit and try to find bad placeholders
 733             // even if there is no concrete type.
 734             let mut visitor = PlaceholderHirTyCollector::default();
 735             visitor.visit_trait_item(trait_item);
 736             placeholder_type_error(tcx, None, &[], visitor.0, false);
 737         }
 738     };
 739
 740     tcx.ensure().predicates_of(def_id);
 741 }
 742
 743 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 744     let def_id = tcx.hir().local_def_id(impl_item_id);
 745     tcx.ensure().generics_of(def_id);
 746     tcx.ensure().type_of(def_id);
 747     tcx.ensure().predicates_of(def_id);
 748     let impl_item = tcx.hir().expect_impl_item(impl_item_id);
 749     match impl_item.kind {
 750         hir::ImplItemKind::Fn(..) => {
 751             tcx.ensure().fn_sig(def_id);
 752         }
 753         hir::ImplItemKind::TyAlias(_) => {
 754             // Account for `type T = _;`
 755             let mut visitor = PlaceholderHirTyCollector::default();
 756             visitor.visit_impl_item(impl_item);
 757             placeholder_type_error(tcx, None, &[], visitor.0, false);
 758         }
 759         hir::ImplItemKind::Const(..) => {}
 760     }
 761 }
 762
 763 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 764     let def_id = tcx.hir().local_def_id(ctor_id);
 765     tcx.ensure().generics_of(def_id);
 766     tcx.ensure().type_of(def_id);
 767     tcx.ensure().predicates_of(def_id);
 768 }
 769
 770 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 771     let def = tcx.adt_def(def_id);
 772     let repr_type = def.repr.discr_type();
 773     let initial = repr_type.initial_discriminant(tcx);
 774     let mut prev_discr = None::<Discr<'_>>;
 775
 776     // fill the discriminant values and field types
 777     for variant in variants {
 778         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 779         prev_discr = Some(
 780             if let Some(ref e) = variant.disr_expr {
 781                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 782                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 783             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 784                 Some(discr)
 785             } else {
 786                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 787                     .span_label(
 788                         variant.span,
 789                         format!("overflowed on value after {}", prev_discr.unwrap()),
 790                     )
 791                     .note(&format!(
 792                         "explicitly set `{} = {}` if that is desired outcome",
 793                         variant.ident, wrapped_discr
 794                     ))
 795                     .emit();
 796                 None
 797             }
 798             .unwrap_or(wrapped_discr),
 799         );
 800
 801         for f in variant.data.fields() {
 802             let def_id = tcx.hir().local_def_id(f.hir_id);
 803             tcx.ensure().generics_of(def_id);
 804             tcx.ensure().type_of(def_id);
 805             tcx.ensure().predicates_of(def_id);
 806         }
 807
 808         // Convert the ctor, if any. This also registers the variant as
 809         // an item.
 810         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 811             convert_variant_ctor(tcx, ctor_hir_id);
 812         }
 813     }
 814 }
 815
 816 fn convert_variant(
 817     tcx: TyCtxt<'_>,
 818     variant_did: Option<LocalDefId>,
 819     ctor_did: Option<LocalDefId>,
 820     ident: Ident,
 821     discr: ty::VariantDiscr,
 822     def: &hir::VariantData<'_>,
 823     adt_kind: ty::AdtKind,
 824     parent_did: LocalDefId,
 825 ) -> ty::VariantDef {
 826     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 827     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did));
 828     let fields = def
 829         .fields()
 830         .iter()
 831         .map(|f| {
 832             let fid = tcx.hir().local_def_id(f.hir_id);
 833             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 834             if let Some(prev_span) = dup_span {
 835                 struct_span_err!(
 836                     tcx.sess,
 837                     f.span,
 838                     E0124,
 839                     "field `{}` is already declared",
 840                     f.ident
 841                 )
 842                 .span_label(f.span, "field already declared")
 843                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 844                 .emit();
 845             } else {
 846                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 847             }
 848
 849             ty::FieldDef {
 850                 did: fid.to_def_id(),
 851                 ident: f.ident,
 852                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 853             }
 854         })
 855         .collect();
 856     let recovered = match def {
 857         hir::VariantData::Struct(_, r) => *r,
 858         _ => false,
 859     };
 860     ty::VariantDef::new(
 861         tcx,
 862         ident,
 863         variant_did.map(LocalDefId::to_def_id),
 864         ctor_did.map(LocalDefId::to_def_id),
 865         discr,
 866         fields,
 867         CtorKind::from_hir(def),
 868         adt_kind,
 869         parent_did.to_def_id(),
 870         recovered,
 871     )
 872 }
 873
 874 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 875     use rustc_hir::*;
 876
 877     let def_id = def_id.expect_local();
 878     let hir_id = tcx.hir().as_local_hir_id(def_id);
 879     let item = match tcx.hir().get(hir_id) {
 880         Node::Item(item) => item,
 881         _ => bug!(),
 882     };
 883
 884     let repr = ReprOptions::new(tcx, def_id.to_def_id());
 885     let (kind, variants) = match item.kind {
 886         ItemKind::Enum(ref def, _) => {
 887             let mut distance_from_explicit = 0;
 888             let variants = def
 889                 .variants
 890                 .iter()
 891                 .map(|v| {
 892                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 893                     let ctor_did =
 894                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 895
 896                     let discr = if let Some(ref e) = v.disr_expr {
 897                         distance_from_explicit = 0;
 898                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
 899                     } else {
 900                         ty::VariantDiscr::Relative(distance_from_explicit)
 901                     };
 902                     distance_from_explicit += 1;
 903
 904                     convert_variant(
 905                         tcx,
 906                         variant_did,
 907                         ctor_did,
 908                         v.ident,
 909                         discr,
 910                         &v.data,
 911                         AdtKind::Enum,
 912                         def_id,
 913                     )
 914                 })
 915                 .collect();
 916
 917             (AdtKind::Enum, variants)
 918         }
 919         ItemKind::Struct(ref def, _) => {
 920             let variant_did = None::<LocalDefId>;
 921             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 922
 923             let variants = std::iter::once(convert_variant(
 924                 tcx,
 925                 variant_did,
 926                 ctor_did,
 927                 item.ident,
 928                 ty::VariantDiscr::Relative(0),
 929                 def,
 930                 AdtKind::Struct,
 931                 def_id,
 932             ))
 933             .collect();
 934
 935             (AdtKind::Struct, variants)
 936         }
 937         ItemKind::Union(ref def, _) => {
 938             let variant_did = None;
 939             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 940
 941             let variants = std::iter::once(convert_variant(
 942                 tcx,
 943                 variant_did,
 944                 ctor_did,
 945                 item.ident,
 946                 ty::VariantDiscr::Relative(0),
 947                 def,
 948                 AdtKind::Union,
 949                 def_id,
 950             ))
 951             .collect();
 952
 953             (AdtKind::Union, variants)
 954         }
 955         _ => bug!(),
 956     };
 957     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
 958 }
 959
 960 /// Ensures that the super-predicates of the trait with a `DefId`
 961 /// of `trait_def_id` are converted and stored. This also ensures that
 962 /// the transitive super-predicates are converted.
 963 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 964     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 965     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id.expect_local());
 966
 967     let item = match tcx.hir().get(trait_hir_id) {
 968         Node::Item(item) => item,
 969         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 970     };
 971
 972     let (generics, bounds) = match item.kind {
 973         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 974         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 975         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 976     };
 977
 978     let icx = ItemCtxt::new(tcx, trait_def_id);
 979
 980     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 981     let self_param_ty = tcx.types.self_param;
 982     let superbounds1 =
 983         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 984
 985     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 986
 987     // Convert any explicit superbounds in the where-clause,
 988     // e.g., `trait Foo where Self: Bar`.
 989     // In the case of trait aliases, however, we include all bounds in the where-clause,
 990     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 991     // as one of its "superpredicates".
 992     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 993     let superbounds2 = icx.type_parameter_bounds_in_generics(
 994         generics,
 995         item.hir_id,
 996         self_param_ty,
 997         OnlySelfBounds(!is_trait_alias),
 998     );
 999
1000     // Combine the two lists to form the complete set of superbounds:
1001     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1002
1003     // Now require that immediate supertraits are converted,
1004     // which will, in turn, reach indirect supertraits.
1005     for &(pred, span) in superbounds {
1006         debug!("superbound: {:?}", pred);
1007         if let ty::PredicateKind::Trait(bound, _) = pred.ignore_qualifiers(tcx).skip_binder().kind()
1008         {
1009             tcx.at(span).super_predicates_of(bound.def_id());
1010         }
1011     }
1012
1013     ty::GenericPredicates { parent: None, predicates: superbounds }
1014 }
1015
1016 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1017     let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
1018     let item = tcx.hir().expect_item(hir_id);
1019
1020     let (is_auto, unsafety) = match item.kind {
1021         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
1022         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
1023         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1024     };
1025
1026     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1027     if paren_sugar && !tcx.features().unboxed_closures {
1028         tcx.sess
1029             .struct_span_err(
1030                 item.span,
1031                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1032                  which traits can use parenthetical notation",
1033             )
1034             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1035             .emit();
1036     }
1037
1038     let is_marker = tcx.has_attr(def_id, sym::marker);
1039     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1040         ty::trait_def::TraitSpecializationKind::Marker
1041     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1042         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1043     } else {
1044         ty::trait_def::TraitSpecializationKind::None
1045     };
1046     let def_path_hash = tcx.def_path_hash(def_id);
1047     ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, spec_kind, def_path_hash)
1048 }
1049
1050 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1051     struct LateBoundRegionsDetector<'tcx> {
1052         tcx: TyCtxt<'tcx>,
1053         outer_index: ty::DebruijnIndex,
1054         has_late_bound_regions: Option<Span>,
1055     }
1056
1057     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1058         type Map = intravisit::ErasedMap<'tcx>;
1059
1060         fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1061             NestedVisitorMap::None
1062         }
1063
1064         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1065             if self.has_late_bound_regions.is_some() {
1066                 return;
1067             }
1068             match ty.kind {
1069                 hir::TyKind::BareFn(..) => {
1070                     self.outer_index.shift_in(1);
1071                     intravisit::walk_ty(self, ty);
1072                     self.outer_index.shift_out(1);
1073                 }
1074                 _ => intravisit::walk_ty(self, ty),
1075             }
1076         }
1077
1078         fn visit_poly_trait_ref(
1079             &mut self,
1080             tr: &'tcx hir::PolyTraitRef<'tcx>,
1081             m: hir::TraitBoundModifier,
1082         ) {
1083             if self.has_late_bound_regions.is_some() {
1084                 return;
1085             }
1086             self.outer_index.shift_in(1);
1087             intravisit::walk_poly_trait_ref(self, tr, m);
1088             self.outer_index.shift_out(1);
1089         }
1090
1091         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1092             if self.has_late_bound_regions.is_some() {
1093                 return;
1094             }
1095
1096             match self.tcx.named_region(lt.hir_id) {
1097                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1098                 Some(
1099                     rl::Region::LateBound(debruijn, _, _) | rl::Region::LateBoundAnon(debruijn, _),
1100                 ) if debruijn < self.outer_index => {}
1101                 Some(
1102                     rl::Region::LateBound(..)
1103                     | rl::Region::LateBoundAnon(..)
1104                     | rl::Region::Free(..),
1105                 )
1106                 | None => {
1107                     self.has_late_bound_regions = Some(lt.span);
1108                 }
1109             }
1110         }
1111     }
1112
1113     fn has_late_bound_regions<'tcx>(
1114         tcx: TyCtxt<'tcx>,
1115         generics: &'tcx hir::Generics<'tcx>,
1116         decl: &'tcx hir::FnDecl<'tcx>,
1117     ) -> Option<Span> {
1118         let mut visitor = LateBoundRegionsDetector {
1119             tcx,
1120             outer_index: ty::INNERMOST,
1121             has_late_bound_regions: None,
1122         };
1123         for param in generics.params {
1124             if let GenericParamKind::Lifetime { .. } = param.kind {
1125                 if tcx.is_late_bound(param.hir_id) {
1126                     return Some(param.span);
1127                 }
1128             }
1129         }
1130         visitor.visit_fn_decl(decl);
1131         visitor.has_late_bound_regions
1132     }
1133
1134     match node {
1135         Node::TraitItem(item) => match item.kind {
1136             hir::TraitItemKind::Fn(ref sig, _) => {
1137                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1138             }
1139             _ => None,
1140         },
1141         Node::ImplItem(item) => match item.kind {
1142             hir::ImplItemKind::Fn(ref sig, _) => {
1143                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1144             }
1145             _ => None,
1146         },
1147         Node::ForeignItem(item) => match item.kind {
1148             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1149                 has_late_bound_regions(tcx, generics, fn_decl)
1150             }
1151             _ => None,
1152         },
1153         Node::Item(item) => match item.kind {
1154             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1155                 has_late_bound_regions(tcx, generics, &sig.decl)
1156             }
1157             _ => None,
1158         },
1159         _ => None,
1160     }
1161 }
1162
1163 struct AnonConstInParamListDetector {
1164     in_param_list: bool,
1165     found_anon_const_in_list: bool,
1166     ct: HirId,
1167 }
1168
1169 impl<'v> Visitor<'v> for AnonConstInParamListDetector {
1170     type Map = intravisit::ErasedMap<'v>;
1171
1172     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1173         NestedVisitorMap::None
1174     }
1175
1176     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1177         let prev = self.in_param_list;
1178         self.in_param_list = true;
1179         intravisit::walk_generic_param(self, p);
1180         self.in_param_list = prev;
1181     }
1182
1183     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1184         if self.in_param_list && self.ct == c.hir_id {
1185             self.found_anon_const_in_list = true;
1186         } else {
1187             intravisit::walk_anon_const(self, c)
1188         }
1189     }
1190 }
1191
1192 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1193     use rustc_hir::*;
1194
1195     let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
1196
1197     let node = tcx.hir().get(hir_id);
1198     let parent_def_id = match node {
1199         Node::ImplItem(_)
1200         | Node::TraitItem(_)
1201         | Node::Variant(_)
1202         | Node::Ctor(..)
1203         | Node::Field(_) => {
1204             let parent_id = tcx.hir().get_parent_item(hir_id);
1205             Some(tcx.hir().local_def_id(parent_id).to_def_id())
1206         }
1207         // FIXME(#43408) always enable this once `lazy_normalization` is
1208         // stable enough and does not need a feature gate anymore.
1209         Node::AnonConst(_) => {
1210             let parent_id = tcx.hir().get_parent_item(hir_id);
1211             let parent_def_id = tcx.hir().local_def_id(parent_id);
1212
1213             let mut in_param_list = false;
1214             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1215                 if let Some(generics) = node.generics() {
1216                     let mut visitor = AnonConstInParamListDetector {
1217                         in_param_list: false,
1218                         found_anon_const_in_list: false,
1219                         ct: hir_id,
1220                     };
1221
1222                     visitor.visit_generics(generics);
1223                     in_param_list = visitor.found_anon_const_in_list;
1224                     break;
1225                 }
1226             }
1227
1228             if in_param_list {
1229                 // We do not allow generic parameters in anon consts if we are inside
1230                 // of a param list.
1231                 //
1232                 // This affects both default type bindings, e.g. `struct<T, U = [u8; std::mem::size_of::<T>()]>(T, U)`,
1233                 // and the types of const parameters, e.g. `struct V<const N: usize, const M: [u8; N]>();`.
1234                 None
1235             } else if tcx.lazy_normalization() {
1236                 // HACK(eddyb) this provides the correct generics when
1237                 // `feature(const_generics)` is enabled, so that const expressions
1238                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1239                 Some(parent_def_id.to_def_id())
1240             } else {
1241                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1242                 match parent_node {
1243                     // HACK(eddyb) this provides the correct generics for repeat
1244                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1245                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1246                     // as they shouldn't be able to cause query cycle errors.
1247                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1248                     | Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1249                         if constant.hir_id == hir_id =>
1250                     {
1251                         Some(parent_def_id.to_def_id())
1252                     }
1253
1254                     _ => None,
1255                 }
1256             }
1257         }
1258         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1259             Some(tcx.closure_base_def_id(def_id))
1260         }
1261         Node::Item(item) => match item.kind {
1262             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1263                 impl_trait_fn.or_else(|| {
1264                     let parent_id = tcx.hir().get_parent_item(hir_id);
1265                     assert!(parent_id != hir_id && parent_id != CRATE_HIR_ID);
1266                     debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1267                     // Opaque types are always nested within another item, and
1268                     // inherit the generics of the item.
1269                     Some(tcx.hir().local_def_id(parent_id).to_def_id())
1270                 })
1271             }
1272             _ => None,
1273         },
1274         _ => None,
1275     };
1276
1277     let mut opt_self = None;
1278     let mut allow_defaults = false;
1279
1280     let no_generics = hir::Generics::empty();
1281     let ast_generics = match node {
1282         Node::TraitItem(item) => &item.generics,
1283
1284         Node::ImplItem(item) => &item.generics,
1285
1286         Node::Item(item) => {
1287             match item.kind {
1288                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl { ref generics, .. } => generics,
1289
1290                 ItemKind::TyAlias(_, ref generics)
1291                 | ItemKind::Enum(_, ref generics)
1292                 | ItemKind::Struct(_, ref generics)
1293                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1294                 | ItemKind::Union(_, ref generics) => {
1295                     allow_defaults = true;
1296                     generics
1297                 }
1298
1299                 ItemKind::Trait(_, _, ref generics, ..)
1300                 | ItemKind::TraitAlias(ref generics, ..) => {
1301                     // Add in the self type parameter.
1302                     //
1303                     // Something of a hack: use the node id for the trait, also as
1304                     // the node id for the Self type parameter.
1305                     let param_id = item.hir_id;
1306
1307                     opt_self = Some(ty::GenericParamDef {
1308                         index: 0,
1309                         name: kw::SelfUpper,
1310                         def_id: tcx.hir().local_def_id(param_id).to_def_id(),
1311                         pure_wrt_drop: false,
1312                         kind: ty::GenericParamDefKind::Type {
1313                             has_default: false,
1314                             object_lifetime_default: rl::Set1::Empty,
1315                             synthetic: None,
1316                         },
1317                     });
1318
1319                     allow_defaults = true;
1320                     generics
1321                 }
1322
1323                 _ => &no_generics,
1324             }
1325         }
1326
1327         Node::ForeignItem(item) => match item.kind {
1328             ForeignItemKind::Static(..) => &no_generics,
1329             ForeignItemKind::Fn(_, _, ref generics) => generics,
1330             ForeignItemKind::Type => &no_generics,
1331         },
1332
1333         _ => &no_generics,
1334     };
1335
1336     let has_self = opt_self.is_some();
1337     let mut parent_has_self = false;
1338     let mut own_start = has_self as u32;
1339     let parent_count = parent_def_id.map_or(0, |def_id| {
1340         let generics = tcx.generics_of(def_id);
1341         assert_eq!(has_self, false);
1342         parent_has_self = generics.has_self;
1343         own_start = generics.count() as u32;
1344         generics.parent_count + generics.params.len()
1345     });
1346
1347     let mut params: Vec<_> = opt_self.into_iter().collect();
1348
1349     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1350     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1351         name: param.name.ident().name,
1352         index: own_start + i as u32,
1353         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1354         pure_wrt_drop: param.pure_wrt_drop,
1355         kind: ty::GenericParamDefKind::Lifetime,
1356     }));
1357
1358     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1359
1360     // Now create the real type and const parameters.
1361     let type_start = own_start - has_self as u32 + params.len() as u32;
1362     let mut i = 0;
1363
1364     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1365         GenericParamKind::Lifetime { .. } => None,
1366         GenericParamKind::Type { ref default, synthetic, .. } => {
1367             if !allow_defaults && default.is_some() {
1368                 if !tcx.features().default_type_parameter_fallback {
1369                     tcx.struct_span_lint_hir(
1370                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1371                         param.hir_id,
1372                         param.span,
1373                         |lint| {
1374                             lint.build(
1375                                 "defaults for type parameters are only allowed in \
1376                                  `struct`, `enum`, `type`, or `trait` definitions.",
1377                             )
1378                             .emit();
1379                         },
1380                     );
1381                 }
1382             }
1383
1384             let kind = ty::GenericParamDefKind::Type {
1385                 has_default: default.is_some(),
1386                 object_lifetime_default: object_lifetime_defaults
1387                     .as_ref()
1388                     .map_or(rl::Set1::Empty, |o| o[i]),
1389                 synthetic,
1390             };
1391
1392             let param_def = ty::GenericParamDef {
1393                 index: type_start + i as u32,
1394                 name: param.name.ident().name,
1395                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1396                 pure_wrt_drop: param.pure_wrt_drop,
1397                 kind,
1398             };
1399             i += 1;
1400             Some(param_def)
1401         }
1402         GenericParamKind::Const { .. } => {
1403             let param_def = ty::GenericParamDef {
1404                 index: type_start + i as u32,
1405                 name: param.name.ident().name,
1406                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1407                 pure_wrt_drop: param.pure_wrt_drop,
1408                 kind: ty::GenericParamDefKind::Const,
1409             };
1410             i += 1;
1411             Some(param_def)
1412         }
1413     }));
1414
1415     // provide junk type parameter defs - the only place that
1416     // cares about anything but the length is instantiation,
1417     // and we don't do that for closures.
1418     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1419         let dummy_args = if gen.is_some() {
1420             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1421         } else {
1422             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1423         };
1424
1425         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1426             index: type_start + i as u32,
1427             name: Symbol::intern(arg),
1428             def_id,
1429             pure_wrt_drop: false,
1430             kind: ty::GenericParamDefKind::Type {
1431                 has_default: false,
1432                 object_lifetime_default: rl::Set1::Empty,
1433                 synthetic: None,
1434             },
1435         }));
1436     }
1437
1438     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1439
1440     ty::Generics {
1441         parent: parent_def_id,
1442         parent_count,
1443         params,
1444         param_def_id_to_index,
1445         has_self: has_self || parent_has_self,
1446         has_late_bound_regions: has_late_bound_regions(tcx, node),
1447     }
1448 }
1449
1450 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1451     generic_args
1452         .iter()
1453         .filter_map(|arg| match arg {
1454             hir::GenericArg::Type(ty) => Some(ty),
1455             _ => None,
1456         })
1457         .any(is_suggestable_infer_ty)
1458 }
1459
1460 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1461 /// use inference to provide suggestions for the appropriate type if possible.
1462 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1463     use hir::TyKind::*;
1464     match &ty.kind {
1465         Infer => true,
1466         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1467         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1468         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1469         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1470         Path(hir::QPath::TypeRelative(ty, segment)) => {
1471             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1472         }
1473         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1474             ty_opt.map_or(false, is_suggestable_infer_ty)
1475                 || segments
1476                     .iter()
1477                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1478         }
1479         _ => false,
1480     }
1481 }
1482
1483 pub fn get_infer_ret_ty(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1484     if let hir::FnRetTy::Return(ref ty) = output {
1485         if is_suggestable_infer_ty(ty) {
1486             return Some(&**ty);
1487         }
1488     }
1489     None
1490 }
1491
1492 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1493     use rustc_hir::Node::*;
1494     use rustc_hir::*;
1495
1496     let def_id = def_id.expect_local();
1497     let hir_id = tcx.hir().as_local_hir_id(def_id);
1498
1499     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1500
1501     match tcx.hir().get(hir_id) {
1502         TraitItem(hir::TraitItem {
1503             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1504             ident,
1505             generics,
1506             ..
1507         })
1508         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1509         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1510             match get_infer_ret_ty(&sig.decl.output) {
1511                 Some(ty) => {
1512                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1513                     let mut visitor = PlaceholderHirTyCollector::default();
1514                     visitor.visit_ty(ty);
1515                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1516                     let ret_ty = fn_sig.output();
1517                     if ret_ty != tcx.ty_error() {
1518                         diag.span_suggestion(
1519                             ty.span,
1520                             "replace with the correct return type",
1521                             ret_ty.to_string(),
1522                             Applicability::MaybeIncorrect,
1523                         );
1524                     }
1525                     diag.emit();
1526                     ty::Binder::bind(fn_sig)
1527                 }
1528                 None => AstConv::ty_of_fn(
1529                     &icx,
1530                     sig.header.unsafety,
1531                     sig.header.abi,
1532                     &sig.decl,
1533                     &generics,
1534                     Some(ident.span),
1535                 ),
1536             }
1537         }
1538
1539         TraitItem(hir::TraitItem {
1540             kind: TraitItemKind::Fn(FnSig { header, decl }, _),
1541             ident,
1542             generics,
1543             ..
1544         }) => {
1545             AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl, &generics, Some(ident.span))
1546         }
1547
1548         ForeignItem(&hir::ForeignItem {
1549             kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1550             ident,
1551             ..
1552         }) => {
1553             let abi = tcx.hir().get_foreign_abi(hir_id);
1554             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1555         }
1556
1557         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1558             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id).to_def_id());
1559             let inputs =
1560                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1561             ty::Binder::bind(tcx.mk_fn_sig(
1562                 inputs,
1563                 ty,
1564                 false,
1565                 hir::Unsafety::Normal,
1566                 abi::Abi::Rust,
1567             ))
1568         }
1569
1570         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1571             // Closure signatures are not like other function
1572             // signatures and cannot be accessed through `fn_sig`. For
1573             // example, a closure signature excludes the `self`
1574             // argument. In any case they are embedded within the
1575             // closure type as part of the `ClosureSubsts`.
1576             //
1577             // To get the signature of a closure, you should use the
1578             // `sig` method on the `ClosureSubsts`:
1579             //
1580             //    substs.as_closure().sig(def_id, tcx)
1581             bug!(
1582                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1583             );
1584         }
1585
1586         x => {
1587             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1588         }
1589     }
1590 }
1591
1592 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1593     let icx = ItemCtxt::new(tcx, def_id);
1594
1595     let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
1596     match tcx.hir().expect_item(hir_id).kind {
1597         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
1598             let selfty = tcx.type_of(def_id);
1599             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1600         }),
1601         _ => bug!(),
1602     }
1603 }
1604
1605 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1606     let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
1607     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1608     let item = tcx.hir().expect_item(hir_id);
1609     match &item.kind {
1610         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative(span), of_trait, .. } => {
1611             if is_rustc_reservation {
1612                 let span = span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(*span));
1613                 tcx.sess.span_err(span, "reservation impls can't be negative");
1614             }
1615             ty::ImplPolarity::Negative
1616         }
1617         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
1618             if is_rustc_reservation {
1619                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1620             }
1621             ty::ImplPolarity::Positive
1622         }
1623         hir::ItemKind::Impl {
1624             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
1625         } => {
1626             if is_rustc_reservation {
1627                 ty::ImplPolarity::Reservation
1628             } else {
1629                 ty::ImplPolarity::Positive
1630             }
1631         }
1632         ref item => bug!("impl_polarity: {:?} not an impl", item),
1633     }
1634 }
1635
1636 /// Returns the early-bound lifetimes declared in this generics
1637 /// listing. For anything other than fns/methods, this is just all
1638 /// the lifetimes that are declared. For fns or methods, we have to
1639 /// screen out those that do not appear in any where-clauses etc using
1640 /// `resolve_lifetime::early_bound_lifetimes`.
1641 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1642     tcx: TyCtxt<'tcx>,
1643     generics: &'a hir::Generics<'a>,
1644 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1645     generics.params.iter().filter(move |param| match param.kind {
1646         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1647         _ => false,
1648     })
1649 }
1650
1651 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1652 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1653 /// inferred constraints concerning which regions outlive other regions.
1654 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1655     debug!("predicates_defined_on({:?})", def_id);
1656     let mut result = tcx.explicit_predicates_of(def_id);
1657     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1658     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1659     if !inferred_outlives.is_empty() {
1660         debug!(
1661             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1662             def_id, inferred_outlives,
1663         );
1664         if result.predicates.is_empty() {
1665             result.predicates = inferred_outlives;
1666         } else {
1667             result.predicates = tcx
1668                 .arena
1669                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1670         }
1671     }
1672     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1673     result
1674 }
1675
1676 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1677 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1678 /// `Self: Trait` predicates for traits.
1679 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1680     let mut result = tcx.predicates_defined_on(def_id);
1681
1682     if tcx.is_trait(def_id) {
1683         // For traits, add `Self: Trait` predicate. This is
1684         // not part of the predicates that a user writes, but it
1685         // is something that one must prove in order to invoke a
1686         // method or project an associated type.
1687         //
1688         // In the chalk setup, this predicate is not part of the
1689         // "predicates" for a trait item. But it is useful in
1690         // rustc because if you directly (e.g.) invoke a trait
1691         // method like `Trait::method(...)`, you must naturally
1692         // prove that the trait applies to the types that were
1693         // used, and adding the predicate into this list ensures
1694         // that this is done.
1695         let span = tcx.sess.source_map().guess_head_span(tcx.def_span(def_id));
1696         result.predicates =
1697             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
1698                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
1699                 span,
1700             ))));
1701     }
1702     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1703     result
1704 }
1705
1706 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1707 /// N.B., this does not include any implied/inferred constraints.
1708 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1709     use rustc_hir::*;
1710
1711     debug!("explicit_predicates_of(def_id={:?})", def_id);
1712
1713     /// A data structure with unique elements, which preserves order of insertion.
1714     /// Preserving the order of insertion is important here so as not to break
1715     /// compile-fail UI tests.
1716     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
1717     struct UniquePredicates<'tcx> {
1718         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
1719         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
1720     }
1721
1722     impl<'tcx> UniquePredicates<'tcx> {
1723         fn new() -> Self {
1724             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
1725         }
1726
1727         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
1728             if self.uniques.insert(value) {
1729                 self.predicates.push(value);
1730             }
1731         }
1732
1733         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
1734             for value in iter {
1735                 self.push(value);
1736             }
1737         }
1738     }
1739
1740     let hir_id = tcx.hir().as_local_hir_id(def_id.expect_local());
1741     let node = tcx.hir().get(hir_id);
1742
1743     let mut is_trait = None;
1744     let mut is_default_impl_trait = None;
1745     let mut is_trait_associated_type = None;
1746
1747     let icx = ItemCtxt::new(tcx, def_id);
1748     let constness = icx.default_constness_for_trait_bounds();
1749
1750     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
1751
1752     let mut predicates = UniquePredicates::new();
1753
1754     let ast_generics = match node {
1755         Node::TraitItem(item) => {
1756             if let hir::TraitItemKind::Type(bounds, _) = item.kind {
1757                 is_trait_associated_type = Some((bounds, item.span));
1758             }
1759             &item.generics
1760         }
1761
1762         Node::ImplItem(item) => &item.generics,
1763
1764         Node::Item(item) => {
1765             match item.kind {
1766                 ItemKind::Impl { defaultness, ref generics, .. } => {
1767                     if defaultness.is_default() {
1768                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
1769                     }
1770                     generics
1771                 }
1772                 ItemKind::Fn(.., ref generics, _)
1773                 | ItemKind::TyAlias(_, ref generics)
1774                 | ItemKind::Enum(_, ref generics)
1775                 | ItemKind::Struct(_, ref generics)
1776                 | ItemKind::Union(_, ref generics) => generics,
1777
1778                 ItemKind::Trait(_, _, ref generics, .., items) => {
1779                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
1780                     generics
1781                 }
1782                 ItemKind::TraitAlias(ref generics, _) => {
1783                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
1784                     generics
1785                 }
1786                 ItemKind::OpaqueTy(OpaqueTy {
1787                     ref bounds,
1788                     impl_trait_fn,
1789                     ref generics,
1790                     origin: _,
1791                 }) => {
1792                     let bounds_predicates = ty::print::with_no_queries(|| {
1793                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
1794                         let opaque_ty = tcx.mk_opaque(def_id, substs);
1795
1796                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
1797                         let bounds = AstConv::compute_bounds(
1798                             &icx,
1799                             opaque_ty,
1800                             bounds,
1801                             SizedByDefault::Yes,
1802                             tcx.def_span(def_id),
1803                         );
1804
1805                         bounds.predicates(tcx, opaque_ty)
1806                     });
1807                     if impl_trait_fn.is_some() {
1808                         // opaque types
1809                         return ty::GenericPredicates {
1810                             parent: None,
1811                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
1812                         };
1813                     } else {
1814                         // named opaque types
1815                         predicates.extend(bounds_predicates);
1816                         generics
1817                     }
1818                 }
1819
1820                 _ => NO_GENERICS,
1821             }
1822         }
1823
1824         Node::ForeignItem(item) => match item.kind {
1825             ForeignItemKind::Static(..) => NO_GENERICS,
1826             ForeignItemKind::Fn(_, _, ref generics) => generics,
1827             ForeignItemKind::Type => NO_GENERICS,
1828         },
1829
1830         _ => NO_GENERICS,
1831     };
1832
1833     let generics = tcx.generics_of(def_id);
1834     let parent_count = generics.parent_count as u32;
1835     let has_own_self = generics.has_self && parent_count == 0;
1836
1837     // Below we'll consider the bounds on the type parameters (including `Self`)
1838     // and the explicit where-clauses, but to get the full set of predicates
1839     // on a trait we need to add in the supertrait bounds and bounds found on
1840     // associated types.
1841     if let Some((_trait_ref, _)) = is_trait {
1842         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
1843     }
1844
1845     // In default impls, we can assume that the self type implements
1846     // the trait. So in:
1847     //
1848     //     default impl Foo for Bar { .. }
1849     //
1850     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
1851     // (see below). Recall that a default impl is not itself an impl, but rather a
1852     // set of defaults that can be incorporated into another impl.
1853     if let Some(trait_ref) = is_default_impl_trait {
1854         predicates.push((
1855             trait_ref.to_poly_trait_ref().without_const().to_predicate(tcx),
1856             tcx.def_span(def_id),
1857         ));
1858     }
1859
1860     // Collect the region predicates that were declared inline as
1861     // well. In the case of parameters declared on a fn or method, we
1862     // have to be careful to only iterate over early-bound regions.
1863     let mut index = parent_count + has_own_self as u32;
1864     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
1865         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
1866             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1867             index,
1868             name: param.name.ident().name,
1869         }));
1870         index += 1;
1871
1872         match param.kind {
1873             GenericParamKind::Lifetime { .. } => {
1874                 param.bounds.iter().for_each(|bound| match bound {
1875                     hir::GenericBound::Outlives(lt) => {
1876                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
1877                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
1878                         predicates.push((outlives.to_predicate(tcx), lt.span));
1879                     }
1880                     _ => bug!(),
1881                 });
1882             }
1883             _ => bug!(),
1884         }
1885     }
1886
1887     // Collect the predicates that were written inline by the user on each
1888     // type parameter (e.g., `<T: Foo>`).
1889     for param in ast_generics.params {
1890         match param.kind {
1891             // We already dealt with early bound lifetimes above.
1892             GenericParamKind::Lifetime { .. } => (),
1893             GenericParamKind::Type { .. } => {
1894                 let name = param.name.ident().name;
1895                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
1896                 index += 1;
1897
1898                 let sized = SizedByDefault::Yes;
1899                 let bounds =
1900                     AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
1901                 predicates.extend(bounds.predicates(tcx, param_ty));
1902             }
1903             GenericParamKind::Const { .. } => {
1904                 // Bounds on const parameters are currently not possible.
1905                 debug_assert!(param.bounds.is_empty());
1906                 index += 1;
1907             }
1908         }
1909     }
1910
1911     // Add in the bounds that appear in the where-clause.
1912     let where_clause = &ast_generics.where_clause;
1913     for predicate in where_clause.predicates {
1914         match predicate {
1915             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
1916                 let ty = icx.to_ty(&bound_pred.bounded_ty);
1917
1918                 // Keep the type around in a dummy predicate, in case of no bounds.
1919                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
1920                 // is still checked for WF.
1921                 if bound_pred.bounds.is_empty() {
1922                     if let ty::Param(_) = ty.kind {
1923                         // This is a `where T:`, which can be in the HIR from the
1924                         // transformation that moves `?Sized` to `T`'s declaration.
1925                         // We can skip the predicate because type parameters are
1926                         // trivially WF, but also we *should*, to avoid exposing
1927                         // users who never wrote `where Type:,` themselves, to
1928                         // compiler/tooling bugs from not handling WF predicates.
1929                     } else {
1930                         let span = bound_pred.bounded_ty.span;
1931                         let re_root_empty = tcx.lifetimes.re_root_empty;
1932                         let predicate = ty::OutlivesPredicate(ty, re_root_empty);
1933                         predicates.push((
1934                             ty::PredicateKind::TypeOutlives(ty::Binder::bind(predicate))
1935                                 .to_predicate(tcx),
1936                             span,
1937                         ));
1938                     }
1939                 }
1940
1941                 for bound in bound_pred.bounds.iter() {
1942                     match bound {
1943                         &hir::GenericBound::Trait(ref poly_trait_ref, modifier) => {
1944                             let constness = match modifier {
1945                                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
1946                                 hir::TraitBoundModifier::None => constness,
1947                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
1948                             };
1949
1950                             let mut bounds = Bounds::default();
1951                             let _ = AstConv::instantiate_poly_trait_ref(
1952                                 &icx,
1953                                 poly_trait_ref,
1954                                 constness,
1955                                 ty,
1956                                 &mut bounds,
1957                             );
1958                             predicates.extend(bounds.predicates(tcx, ty));
1959                         }
1960
1961                         &hir::GenericBound::Outlives(ref lifetime) => {
1962                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
1963                             predicates.push((
1964                                 ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, region))
1965                                     .to_predicate(tcx)
1966                                     .potentially_qualified(tcx, ty::PredicateKind::ForAll),
1967                                 lifetime.span,
1968                             ))
1969                         }
1970                     }
1971                 }
1972             }
1973
1974             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
1975                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
1976                 predicates.extend(region_pred.bounds.iter().map(|bound| {
1977                     let (r2, span) = match bound {
1978                         hir::GenericBound::Outlives(lt) => {
1979                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
1980                         }
1981                         _ => bug!(),
1982                     };
1983                     let pred = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
1984                         .to_predicate(icx.tcx);
1985
1986                     (pred.potentially_qualified(icx.tcx, ty::PredicateKind::ForAll), span)
1987                 }))
1988             }
1989
1990             &hir::WherePredicate::EqPredicate(..) => {
1991                 // FIXME(#20041)
1992             }
1993         }
1994     }
1995
1996     // Add predicates from associated type bounds (`type X: Bound`)
1997     if tcx.features().generic_associated_types {
1998         // New behavior: bounds declared on associate type are predicates of that
1999         // associated type. Not the default because it needs more testing.
2000         if let Some((bounds, span)) = is_trait_associated_type {
2001             let projection_ty =
2002                 tcx.mk_projection(def_id, InternalSubsts::identity_for_item(tcx, def_id));
2003
2004             predicates.extend(associated_item_bounds(tcx, def_id, bounds, projection_ty, span))
2005         }
2006     } else if let Some((self_trait_ref, trait_items)) = is_trait {
2007         // Current behavior: bounds declared on associate type are predicates
2008         // of its parent trait.
2009         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2010             trait_associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2011         }))
2012     }
2013
2014     let mut predicates = predicates.predicates;
2015
2016     // Subtle: before we store the predicates into the tcx, we
2017     // sort them so that predicates like `T: Foo<Item=U>` come
2018     // before uses of `U`.  This avoids false ambiguity errors
2019     // in trait checking. See `setup_constraining_predicates`
2020     // for details.
2021     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2022         let self_ty = tcx.type_of(def_id);
2023         let trait_ref = tcx.impl_trait_ref(def_id);
2024         cgp::setup_constraining_predicates(
2025             tcx,
2026             &mut predicates,
2027             trait_ref,
2028             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2029         );
2030     }
2031
2032     let result = ty::GenericPredicates {
2033         parent: generics.parent,
2034         predicates: tcx.arena.alloc_from_iter(predicates),
2035     };
2036     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2037     result
2038 }
2039
2040 fn trait_associated_item_predicates(
2041     tcx: TyCtxt<'tcx>,
2042     def_id: DefId,
2043     self_trait_ref: ty::TraitRef<'tcx>,
2044     trait_item_ref: &hir::TraitItemRef,
2045 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2046     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2047     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2048     let bounds = match trait_item.kind {
2049         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2050         _ => return Vec::new(),
2051     };
2052
2053     if !tcx.generics_of(item_def_id).params.is_empty() {
2054         // For GATs the substs provided to the mk_projection call below are
2055         // wrong. We should emit a feature gate error if we get here so skip
2056         // this type.
2057         tcx.sess.delay_span_bug(trait_item.span, "gats used without feature gate");
2058         return Vec::new();
2059     }
2060
2061     let assoc_ty = tcx.mk_projection(
2062         tcx.hir().local_def_id(trait_item.hir_id).to_def_id(),
2063         self_trait_ref.substs,
2064     );
2065
2066     associated_item_bounds(tcx, def_id, bounds, assoc_ty, trait_item.span)
2067 }
2068
2069 fn associated_item_bounds(
2070     tcx: TyCtxt<'tcx>,
2071     def_id: DefId,
2072     bounds: &'tcx [hir::GenericBound<'tcx>],
2073     projection_ty: Ty<'tcx>,
2074     span: Span,
2075 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2076     let bounds = AstConv::compute_bounds(
2077         &ItemCtxt::new(tcx, def_id),
2078         projection_ty,
2079         bounds,
2080         SizedByDefault::Yes,
2081         span,
2082     );
2083
2084     let predicates = bounds.predicates(tcx, projection_ty);
2085
2086     predicates
2087 }
2088
2089 /// Converts a specific `GenericBound` from the AST into a set of
2090 /// predicates that apply to the self type. A vector is returned
2091 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2092 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2093 /// and `<T as Bar>::X == i32`).
2094 fn predicates_from_bound<'tcx>(
2095     astconv: &dyn AstConv<'tcx>,
2096     param_ty: Ty<'tcx>,
2097     bound: &'tcx hir::GenericBound<'tcx>,
2098     constness: hir::Constness,
2099 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2100     match *bound {
2101         hir::GenericBound::Trait(ref tr, modifier) => {
2102             let constness = match modifier {
2103                 hir::TraitBoundModifier::Maybe => return vec![],
2104                 hir::TraitBoundModifier::MaybeConst => hir::Constness::NotConst,
2105                 hir::TraitBoundModifier::None => constness,
2106             };
2107
2108             let mut bounds = Bounds::default();
2109             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2110             bounds.predicates(astconv.tcx(), param_ty)
2111         }
2112         hir::GenericBound::Outlives(ref lifetime) => {
2113             let region = astconv.ast_region_to_region(lifetime, None);
2114             let pred = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region))
2115                 .to_predicate(astconv.tcx())
2116                 .potentially_qualified(astconv.tcx(), ty::PredicateKind::ForAll);
2117             vec![(pred, lifetime.span)]
2118         }
2119     }
2120 }
2121
2122 fn compute_sig_of_foreign_fn_decl<'tcx>(
2123     tcx: TyCtxt<'tcx>,
2124     def_id: DefId,
2125     decl: &'tcx hir::FnDecl<'tcx>,
2126     abi: abi::Abi,
2127     ident: Ident,
2128 ) -> ty::PolyFnSig<'tcx> {
2129     let unsafety = if abi == abi::Abi::RustIntrinsic {
2130         intrinsic_operation_unsafety(tcx.item_name(def_id))
2131     } else {
2132         hir::Unsafety::Unsafe
2133     };
2134     let fty = AstConv::ty_of_fn(
2135         &ItemCtxt::new(tcx, def_id),
2136         unsafety,
2137         abi,
2138         decl,
2139         &hir::Generics::empty(),
2140         Some(ident.span),
2141     );
2142
2143     // Feature gate SIMD types in FFI, since I am not sure that the
2144     // ABIs are handled at all correctly. -huonw
2145     if abi != abi::Abi::RustIntrinsic
2146         && abi != abi::Abi::PlatformIntrinsic
2147         && !tcx.features().simd_ffi
2148     {
2149         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2150             if ty.is_simd() {
2151                 let snip = tcx
2152                     .sess
2153                     .source_map()
2154                     .span_to_snippet(ast_ty.span)
2155                     .map_or(String::new(), |s| format!(" `{}`", s));
2156                 tcx.sess
2157                     .struct_span_err(
2158                         ast_ty.span,
2159                         &format!(
2160                             "use of SIMD type{} in FFI is highly experimental and \
2161                              may result in invalid code",
2162                             snip
2163                         ),
2164                     )
2165                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2166                     .emit();
2167             }
2168         };
2169         for (input, ty) in decl.inputs.iter().zip(fty.inputs().skip_binder()) {
2170             check(&input, ty)
2171         }
2172         if let hir::FnRetTy::Return(ref ty) = decl.output {
2173             check(&ty, fty.output().skip_binder())
2174         }
2175     }
2176
2177     fty
2178 }
2179
2180 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2181     match tcx.hir().get_if_local(def_id) {
2182         Some(Node::ForeignItem(..)) => true,
2183         Some(_) => false,
2184         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2185     }
2186 }
2187
2188 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2189     match tcx.hir().get_if_local(def_id) {
2190         Some(
2191             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2192             | Node::ForeignItem(&hir::ForeignItem {
2193                 kind: hir::ForeignItemKind::Static(_, mutbl),
2194                 ..
2195             }),
2196         ) => Some(mutbl),
2197         Some(_) => None,
2198         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2199     }
2200 }
2201
2202 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2203     match tcx.hir().get_if_local(def_id) {
2204         Some(Node::Expr(&rustc_hir::Expr {
2205             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2206             ..
2207         })) => tcx.hir().body(body_id).generator_kind(),
2208         Some(_) => None,
2209         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2210     }
2211 }
2212
2213 fn from_target_feature(
2214     tcx: TyCtxt<'_>,
2215     id: DefId,
2216     attr: &ast::Attribute,
2217     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2218     target_features: &mut Vec<Symbol>,
2219 ) {
2220     let list = match attr.meta_item_list() {
2221         Some(list) => list,
2222         None => return,
2223     };
2224     let bad_item = |span| {
2225         let msg = "malformed `target_feature` attribute input";
2226         let code = "enable = \"..\"".to_owned();
2227         tcx.sess
2228             .struct_span_err(span, &msg)
2229             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2230             .emit();
2231     };
2232     let rust_features = tcx.features();
2233     for item in list {
2234         // Only `enable = ...` is accepted in the meta-item list.
2235         if !item.check_name(sym::enable) {
2236             bad_item(item.span());
2237             continue;
2238         }
2239
2240         // Must be of the form `enable = "..."` (a string).
2241         let value = match item.value_str() {
2242             Some(value) => value,
2243             None => {
2244                 bad_item(item.span());
2245                 continue;
2246             }
2247         };
2248
2249         // We allow comma separation to enable multiple features.
2250         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2251             let feature_gate = match supported_target_features.get(feature) {
2252                 Some(g) => g,
2253                 None => {
2254                     let msg =
2255                         format!("the feature named `{}` is not valid for this target", feature);
2256                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2257                     err.span_label(
2258                         item.span(),
2259                         format!("`{}` is not valid for this target", feature),
2260                     );
2261                     if feature.starts_with('+') {
2262                         let valid = supported_target_features.contains_key(&feature[1..]);
2263                         if valid {
2264                             err.help("consider removing the leading `+` in the feature name");
2265                         }
2266                     }
2267                     err.emit();
2268                     return None;
2269                 }
2270             };
2271
2272             // Only allow features whose feature gates have been enabled.
2273             let allowed = match feature_gate.as_ref().copied() {
2274                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2275                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2276                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2277                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2278                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2279                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2280                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2281                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2282                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2283                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2284                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2285                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2286                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2287                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2288                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2289                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2290                 Some(name) => bug!("unknown target feature gate {}", name),
2291                 None => true,
2292             };
2293             if !allowed && id.is_local() {
2294                 feature_err(
2295                     &tcx.sess.parse_sess,
2296                     feature_gate.unwrap(),
2297                     item.span(),
2298                     &format!("the target feature `{}` is currently unstable", feature),
2299                 )
2300                 .emit();
2301             }
2302             Some(Symbol::intern(feature))
2303         }));
2304     }
2305 }
2306
2307 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2308     use rustc_middle::mir::mono::Linkage::*;
2309
2310     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2311     // applicable to variable declarations and may not really make sense for
2312     // Rust code in the first place but allow them anyway and trust that the
2313     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2314     // up in the future.
2315     //
2316     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2317     // and don't have to be, LLVM treats them as no-ops.
2318     match name {
2319         "appending" => Appending,
2320         "available_externally" => AvailableExternally,
2321         "common" => Common,
2322         "extern_weak" => ExternalWeak,
2323         "external" => External,
2324         "internal" => Internal,
2325         "linkonce" => LinkOnceAny,
2326         "linkonce_odr" => LinkOnceODR,
2327         "private" => Private,
2328         "weak" => WeakAny,
2329         "weak_odr" => WeakODR,
2330         _ => {
2331             let span = tcx.hir().span_if_local(def_id);
2332             if let Some(span) = span {
2333                 tcx.sess.span_fatal(span, "invalid linkage specified")
2334             } else {
2335                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2336             }
2337         }
2338     }
2339 }
2340
2341 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2342     let attrs = tcx.get_attrs(id);
2343
2344     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2345     if should_inherit_track_caller(tcx, id) {
2346         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2347     }
2348
2349     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2350
2351     let mut inline_span = None;
2352     let mut link_ordinal_span = None;
2353     let mut no_sanitize_span = None;
2354     for attr in attrs.iter() {
2355         if attr.check_name(sym::cold) {
2356             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2357         } else if attr.check_name(sym::rustc_allocator) {
2358             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2359         } else if attr.check_name(sym::unwind) {
2360             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2361         } else if attr.check_name(sym::ffi_returns_twice) {
2362             if tcx.is_foreign_item(id) {
2363                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2364             } else {
2365                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2366                 struct_span_err!(
2367                     tcx.sess,
2368                     attr.span,
2369                     E0724,
2370                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2371                 )
2372                 .emit();
2373             }
2374         } else if attr.check_name(sym::ffi_pure) {
2375             if tcx.is_foreign_item(id) {
2376                 if attrs.iter().any(|a| a.check_name(sym::ffi_const)) {
2377                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2378                     struct_span_err!(
2379                         tcx.sess,
2380                         attr.span,
2381                         E0757,
2382                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2383                     )
2384                     .emit();
2385                 } else {
2386                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2387                 }
2388             } else {
2389                 // `#[ffi_pure]` is only allowed on foreign functions
2390                 struct_span_err!(
2391                     tcx.sess,
2392                     attr.span,
2393                     E0755,
2394                     "`#[ffi_pure]` may only be used on foreign functions"
2395                 )
2396                 .emit();
2397             }
2398         } else if attr.check_name(sym::ffi_const) {
2399             if tcx.is_foreign_item(id) {
2400                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2401             } else {
2402                 // `#[ffi_const]` is only allowed on foreign functions
2403                 struct_span_err!(
2404                     tcx.sess,
2405                     attr.span,
2406                     E0756,
2407                     "`#[ffi_const]` may only be used on foreign functions"
2408                 )
2409                 .emit();
2410             }
2411         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2412             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2413         } else if attr.check_name(sym::naked) {
2414             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2415         } else if attr.check_name(sym::no_mangle) {
2416             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2417         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2418             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2419         } else if attr.check_name(sym::used) {
2420             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2421         } else if attr.check_name(sym::thread_local) {
2422             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2423         } else if attr.check_name(sym::track_caller) {
2424             if tcx.is_closure(id) || tcx.fn_sig(id).abi() != abi::Abi::Rust {
2425                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2426                     .emit();
2427             }
2428             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2429         } else if attr.check_name(sym::export_name) {
2430             if let Some(s) = attr.value_str() {
2431                 if s.as_str().contains('\0') {
2432                     // `#[export_name = ...]` will be converted to a null-terminated string,
2433                     // so it may not contain any null characters.
2434                     struct_span_err!(
2435                         tcx.sess,
2436                         attr.span,
2437                         E0648,
2438                         "`export_name` may not contain null characters"
2439                     )
2440                     .emit();
2441                 }
2442                 codegen_fn_attrs.export_name = Some(s);
2443             }
2444         } else if attr.check_name(sym::target_feature) {
2445             if !tcx.features().target_feature_11 {
2446                 check_target_feature_safe_fn(tcx, id, attr.span);
2447             } else if let Some(local_id) = id.as_local() {
2448                 if tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2449                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2450                 }
2451             }
2452             from_target_feature(
2453                 tcx,
2454                 id,
2455                 attr,
2456                 &supported_target_features,
2457                 &mut codegen_fn_attrs.target_features,
2458             );
2459         } else if attr.check_name(sym::linkage) {
2460             if let Some(val) = attr.value_str() {
2461                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2462             }
2463         } else if attr.check_name(sym::link_section) {
2464             if let Some(val) = attr.value_str() {
2465                 if val.as_str().bytes().any(|b| b == 0) {
2466                     let msg = format!(
2467                         "illegal null byte in link_section \
2468                          value: `{}`",
2469                         &val
2470                     );
2471                     tcx.sess.span_err(attr.span, &msg);
2472                 } else {
2473                     codegen_fn_attrs.link_section = Some(val);
2474                 }
2475             }
2476         } else if attr.check_name(sym::link_name) {
2477             codegen_fn_attrs.link_name = attr.value_str();
2478         } else if attr.check_name(sym::link_ordinal) {
2479             link_ordinal_span = Some(attr.span);
2480             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2481                 codegen_fn_attrs.link_ordinal = ordinal;
2482             }
2483         } else if attr.check_name(sym::no_sanitize) {
2484             no_sanitize_span = Some(attr.span);
2485             if let Some(list) = attr.meta_item_list() {
2486                 for item in list.iter() {
2487                     if item.check_name(sym::address) {
2488                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2489                     } else if item.check_name(sym::memory) {
2490                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2491                     } else if item.check_name(sym::thread) {
2492                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2493                     } else {
2494                         tcx.sess
2495                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2496                             .note("expected one of: `address`, `memory` or `thread`")
2497                             .emit();
2498                     }
2499                 }
2500             }
2501         }
2502     }
2503
2504     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2505         if !attr.has_name(sym::inline) {
2506             return ia;
2507         }
2508         match attr.meta().map(|i| i.kind) {
2509             Some(MetaItemKind::Word) => {
2510                 mark_used(attr);
2511                 InlineAttr::Hint
2512             }
2513             Some(MetaItemKind::List(ref items)) => {
2514                 mark_used(attr);
2515                 inline_span = Some(attr.span);
2516                 if items.len() != 1 {
2517                     struct_span_err!(
2518                         tcx.sess.diagnostic(),
2519                         attr.span,
2520                         E0534,
2521                         "expected one argument"
2522                     )
2523                     .emit();
2524                     InlineAttr::None
2525                 } else if list_contains_name(&items[..], sym::always) {
2526                     InlineAttr::Always
2527                 } else if list_contains_name(&items[..], sym::never) {
2528                     InlineAttr::Never
2529                 } else {
2530                     struct_span_err!(
2531                         tcx.sess.diagnostic(),
2532                         items[0].span(),
2533                         E0535,
2534                         "invalid argument"
2535                     )
2536                     .emit();
2537
2538                     InlineAttr::None
2539                 }
2540             }
2541             Some(MetaItemKind::NameValue(_)) => ia,
2542             None => ia,
2543         }
2544     });
2545
2546     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2547         if !attr.has_name(sym::optimize) {
2548             return ia;
2549         }
2550         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2551         match attr.meta().map(|i| i.kind) {
2552             Some(MetaItemKind::Word) => {
2553                 err(attr.span, "expected one argument");
2554                 ia
2555             }
2556             Some(MetaItemKind::List(ref items)) => {
2557                 mark_used(attr);
2558                 inline_span = Some(attr.span);
2559                 if items.len() != 1 {
2560                     err(attr.span, "expected one argument");
2561                     OptimizeAttr::None
2562                 } else if list_contains_name(&items[..], sym::size) {
2563                     OptimizeAttr::Size
2564                 } else if list_contains_name(&items[..], sym::speed) {
2565                     OptimizeAttr::Speed
2566                 } else {
2567                     err(items[0].span(), "invalid argument");
2568                     OptimizeAttr::None
2569                 }
2570             }
2571             Some(MetaItemKind::NameValue(_)) => ia,
2572             None => ia,
2573         }
2574     });
2575
2576     // If a function uses #[target_feature] it can't be inlined into general
2577     // purpose functions as they wouldn't have the right target features
2578     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2579     // respected.
2580     if !codegen_fn_attrs.target_features.is_empty() {
2581         if codegen_fn_attrs.inline == InlineAttr::Always {
2582             if let Some(span) = inline_span {
2583                 tcx.sess.span_err(
2584                     span,
2585                     "cannot use `#[inline(always)]` with \
2586                      `#[target_feature]`",
2587                 );
2588             }
2589         }
2590     }
2591
2592     if !codegen_fn_attrs.no_sanitize.is_empty() {
2593         if codegen_fn_attrs.inline == InlineAttr::Always {
2594             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2595                 let hir_id = tcx.hir().as_local_hir_id(id.expect_local());
2596                 tcx.struct_span_lint_hir(
2597                     lint::builtin::INLINE_NO_SANITIZE,
2598                     hir_id,
2599                     no_sanitize_span,
2600                     |lint| {
2601                         lint.build("`no_sanitize` will have no effect after inlining")
2602                             .span_note(inline_span, "inlining requested here")
2603                             .emit();
2604                     },
2605                 )
2606             }
2607         }
2608     }
2609
2610     // Weak lang items have the same semantics as "std internal" symbols in the
2611     // sense that they're preserved through all our LTO passes and only
2612     // strippable by the linker.
2613     //
2614     // Additionally weak lang items have predetermined symbol names.
2615     if tcx.is_weak_lang_item(id) {
2616         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2617     }
2618     if let Some(name) = weak_lang_items::link_name(&attrs) {
2619         codegen_fn_attrs.export_name = Some(name);
2620         codegen_fn_attrs.link_name = Some(name);
2621     }
2622     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2623
2624     // Internal symbols to the standard library all have no_mangle semantics in
2625     // that they have defined symbol names present in the function name. This
2626     // also applies to weak symbols where they all have known symbol names.
2627     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2628         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2629     }
2630
2631     codegen_fn_attrs
2632 }
2633
2634 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
2635 /// applied to the method prototype.
2636 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2637     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
2638         if let ty::AssocItemContainer::ImplContainer(impl_def_id) = impl_item.container {
2639             if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id) {
2640                 if let Some(trait_item) = tcx
2641                     .associated_items(trait_def_id)
2642                     .filter_by_name_unhygienic(impl_item.ident.name)
2643                     .find(move |trait_item| {
2644                         trait_item.kind == ty::AssocKind::Fn
2645                             && tcx.hygienic_eq(impl_item.ident, trait_item.ident, trait_def_id)
2646                     })
2647                 {
2648                     return tcx
2649                         .codegen_fn_attrs(trait_item.def_id)
2650                         .flags
2651                         .intersects(CodegenFnAttrFlags::TRACK_CALLER);
2652                 }
2653             }
2654         }
2655     }
2656
2657     false
2658 }
2659
2660 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2661     use rustc_ast::ast::{Lit, LitIntType, LitKind};
2662     let meta_item_list = attr.meta_item_list();
2663     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2664     let sole_meta_list = match meta_item_list {
2665         Some([item]) => item.literal(),
2666         _ => None,
2667     };
2668     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2669         if *ordinal <= usize::MAX as u128 {
2670             Some(*ordinal as usize)
2671         } else {
2672             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2673             tcx.sess
2674                 .struct_span_err(attr.span, &msg)
2675                 .note("the value may not exceed `usize::MAX`")
2676                 .emit();
2677             None
2678         }
2679     } else {
2680         tcx.sess
2681             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2682             .note("an unsuffixed integer value, e.g., `1`, is expected")
2683             .emit();
2684         None
2685     }
2686 }
2687
2688 fn check_link_name_xor_ordinal(
2689     tcx: TyCtxt<'_>,
2690     codegen_fn_attrs: &CodegenFnAttrs,
2691     inline_span: Option<Span>,
2692 ) {
2693     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2694         return;
2695     }
2696     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2697     if let Some(span) = inline_span {
2698         tcx.sess.span_err(span, msg);
2699     } else {
2700         tcx.sess.err(msg);
2701     }
2702 }
2703
2704 /// Checks the function annotated with `#[target_feature]` is unsafe,
2705 /// reporting an error if it isn't.
2706 fn check_target_feature_safe_fn(tcx: TyCtxt<'_>, id: DefId, attr_span: Span) {
2707     if tcx.is_closure(id) || tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2708         let mut err = feature_err(
2709             &tcx.sess.parse_sess,
2710             sym::target_feature_11,
2711             attr_span,
2712             "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2713         );
2714         err.span_label(tcx.def_span(id), "not an `unsafe` function");
2715         err.emit();
2716     }
2717 }
2718
2719 /// Checks the function annotated with `#[target_feature]` is not a safe
2720 /// trait method implementation, reporting an error if it is.
2721 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
2722     let hir_id = tcx.hir().as_local_hir_id(id);
2723     let node = tcx.hir().get(hir_id);
2724     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
2725         let parent_id = tcx.hir().get_parent_item(hir_id);
2726         let parent_item = tcx.hir().expect_item(parent_id);
2727         if let hir::ItemKind::Impl { of_trait: Some(_), .. } = parent_item.kind {
2728             tcx.sess
2729                 .struct_span_err(
2730                     attr_span,
2731                     "`#[target_feature(..)]` cannot be applied to safe trait method",
2732                 )
2733                 .span_label(attr_span, "cannot be applied to safe trait method")
2734                 .span_label(tcx.def_span(id), "not an `unsafe` function")
2735                 .emit();
2736         }
2737     }
2738 }