src/librustc_typeck/collect.rs

   1 // ignore-tidy-filelength
   2
   3 //! "Collection" is the process of determining the type and other external
   4 //! details of each item in Rust. Collection is specifically concerned
   5 //! with *inter-procedural* things -- for example, for a function
   6 //! definition, collection will figure out the type and signature of the
   7 //! function, but it will not visit the *body* of the function in any way,
   8 //! nor examine type annotations on local variables (that's the job of
   9 //! type *checking*).
  10 //!
  11 //! Collecting is ultimately defined by a bundle of queries that
  12 //! inquire after various facts about the items in the crate (e.g.,
  13 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  14 //! for the full set.
  15 //!
  16 //! At present, however, we do run collection across all items in the
  17 //! crate as a kind of pass. This should eventually be factored away.
  18
  19 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::lint;
  23 use crate::middle::lang_items;
  24 use crate::middle::resolve_lifetime as rl;
  25 use rustc::hir::map::blocks::FnLikeNode;
  26 use rustc::hir::map::Map;
  27 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  28 use rustc::mir::mono::Linkage;
  29 use rustc::session::parse::feature_err;
  30 use rustc::traits;
  31 use rustc::ty::query::Providers;
  32 use rustc::ty::subst::GenericArgKind;
  33 use rustc::ty::subst::{InternalSubsts, Subst};
  34 use rustc::ty::util::Discr;
  35 use rustc::ty::util::IntTypeExt;
  36 use rustc::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt, WithConstness};
  37 use rustc::ty::{ReprOptions, ToPredicate};
  38 use rustc_attr::{list_contains_name, mark_used, InlineAttr, OptimizeAttr};
  39 use rustc_data_structures::captures::Captures;
  40 use rustc_data_structures::fx::FxHashMap;
  41 use rustc_errors::{struct_span_err, Applicability, StashKey};
  42 use rustc_hir as hir;
  43 use rustc_hir::def::{CtorKind, DefKind, Res};
  44 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
  45 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  46 use rustc_hir::{GenericParamKind, Node, Unsafety};
  47 use rustc_span::symbol::{kw, sym, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::abi;
  50 use syntax::ast;
  51 use syntax::ast::{Ident, MetaItemKind};
  52
  53 struct OnlySelfBounds(bool);
  54
  55 ///////////////////////////////////////////////////////////////////////////
  56 // Main entry point
  57
  58 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
  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         type_of,
  68         generics_of,
  69         predicates_of,
  70         predicates_defined_on,
  71         explicit_predicates_of,
  72         super_predicates_of,
  73         type_param_predicates,
  74         trait_def,
  75         adt_def,
  76         fn_sig,
  77         impl_trait_ref,
  78         impl_polarity,
  79         is_foreign_item,
  80         static_mutability,
  81         codegen_fn_attrs,
  82         collect_mod_item_types,
  83         ..*providers
  84     };
  85 }
  86
  87 ///////////////////////////////////////////////////////////////////////////
  88
  89 /// Context specific to some particular item. This is what implements
  90 /// `AstConv`. It has information about the predicates that are defined
  91 /// on the trait. Unfortunately, this predicate information is
  92 /// available in various different forms at various points in the
  93 /// process. So we can't just store a pointer to e.g., the AST or the
  94 /// parsed ty form, we have to be more flexible. To this end, the
  95 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  96 /// `get_type_parameter_bounds` requests, drawing the information from
  97 /// the AST (`hir::Generics`), recursively.
  98 pub struct ItemCtxt<'tcx> {
  99     tcx: TyCtxt<'tcx>,
 100     item_def_id: DefId,
 101 }
 102
 103 ///////////////////////////////////////////////////////////////////////////
 104
 105 #[derive(Default)]
 106 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 107
 108 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 109     type Map = Map<'v>;
 110
 111     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 112         NestedVisitorMap::None
 113     }
 114     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 115         if let hir::TyKind::Infer = t.kind {
 116             self.0.push(t.span);
 117         }
 118         intravisit::walk_ty(self, t)
 119     }
 120 }
 121
 122 struct CollectItemTypesVisitor<'tcx> {
 123     tcx: TyCtxt<'tcx>,
 124 }
 125
 126 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 127 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 128 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 129 crate fn placeholder_type_error(
 130     tcx: TyCtxt<'tcx>,
 131     span: Span,
 132     generics: &[hir::GenericParam<'_>],
 133     placeholder_types: Vec<Span>,
 134     suggest: bool,
 135 ) {
 136     if placeholder_types.is_empty() {
 137         return;
 138     }
 139     // This is the whitelist of possible parameter names that we might suggest.
 140     let possible_names = ["T", "K", "L", "A", "B", "C"];
 141     let used_names = generics
 142         .iter()
 143         .filter_map(|p| match p.name {
 144             hir::ParamName::Plain(ident) => Some(ident.name),
 145             _ => None,
 146         })
 147         .collect::<Vec<_>>();
 148
 149     let type_name = possible_names
 150         .iter()
 151         .find(|n| !used_names.contains(&Symbol::intern(n)))
 152         .unwrap_or(&"ParamName");
 153
 154     let mut sugg: Vec<_> =
 155         placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
 156     if generics.is_empty() {
 157         sugg.push((span, format!("<{}>", type_name)));
 158     } else if let Some(arg) = generics.iter().find(|arg| match arg.name {
 159         hir::ParamName::Plain(Ident { name: kw::Underscore, .. }) => true,
 160         _ => false,
 161     }) {
 162         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 163         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 164         sugg.push((arg.span, format!("{}", type_name)));
 165     } else {
 166         sugg.push((
 167             generics.iter().last().unwrap().span.shrink_to_hi(),
 168             format!(", {}", type_name),
 169         ));
 170     }
 171     let mut err = bad_placeholder_type(tcx, placeholder_types);
 172     if suggest {
 173         err.multipart_suggestion(
 174             "use type parameters instead",
 175             sugg,
 176             Applicability::HasPlaceholders,
 177         );
 178     }
 179     err.emit();
 180 }
 181
 182 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 183     let (generics, suggest) = match &item.kind {
 184         hir::ItemKind::Union(_, generics)
 185         | hir::ItemKind::Enum(_, generics)
 186         | hir::ItemKind::TraitAlias(generics, _)
 187         | hir::ItemKind::Trait(_, _, generics, ..)
 188         | hir::ItemKind::Impl { generics, .. }
 189         | hir::ItemKind::Struct(_, generics) => (generics, true),
 190         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 191         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 192         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 193         _ => return,
 194     };
 195
 196     let mut visitor = PlaceholderHirTyCollector::default();
 197     visitor.visit_item(item);
 198
 199     placeholder_type_error(tcx, generics.span, &generics.params[..], visitor.0, suggest);
 200 }
 201
 202 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 203     type Map = Map<'tcx>;
 204
 205     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 206         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 207     }
 208
 209     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 210         convert_item(self.tcx, item.hir_id);
 211         reject_placeholder_type_signatures_in_item(self.tcx, item);
 212         intravisit::walk_item(self, item);
 213     }
 214
 215     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 216         for param in generics.params {
 217             match param.kind {
 218                 hir::GenericParamKind::Lifetime { .. } => {}
 219                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 220                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 221                     self.tcx.type_of(def_id);
 222                 }
 223                 hir::GenericParamKind::Type { .. } => {}
 224                 hir::GenericParamKind::Const { .. } => {
 225                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 226                     self.tcx.type_of(def_id);
 227                 }
 228             }
 229         }
 230         intravisit::walk_generics(self, generics);
 231     }
 232
 233     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 234         if let hir::ExprKind::Closure(..) = expr.kind {
 235             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 236             self.tcx.generics_of(def_id);
 237             self.tcx.type_of(def_id);
 238         }
 239         intravisit::walk_expr(self, expr);
 240     }
 241
 242     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 243         convert_trait_item(self.tcx, trait_item.hir_id);
 244         intravisit::walk_trait_item(self, trait_item);
 245     }
 246
 247     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 248         convert_impl_item(self.tcx, impl_item.hir_id);
 249         intravisit::walk_impl_item(self, impl_item);
 250     }
 251 }
 252
 253 ///////////////////////////////////////////////////////////////////////////
 254 // Utility types and common code for the above passes.
 255
 256 fn bad_placeholder_type(
 257     tcx: TyCtxt<'tcx>,
 258     mut spans: Vec<Span>,
 259 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 260     spans.sort();
 261     let mut err = struct_span_err!(
 262         tcx.sess,
 263         spans.clone(),
 264         E0121,
 265         "the type placeholder `_` is not allowed within types on item signatures",
 266     );
 267     for span in spans {
 268         err.span_label(span, "not allowed in type signatures");
 269     }
 270     err
 271 }
 272
 273 impl ItemCtxt<'tcx> {
 274     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 275         ItemCtxt { tcx, item_def_id }
 276     }
 277
 278     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 279         AstConv::ast_ty_to_ty(self, ast_ty)
 280     }
 281 }
 282
 283 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 284     fn tcx(&self) -> TyCtxt<'tcx> {
 285         self.tcx
 286     }
 287
 288     fn item_def_id(&self) -> Option<DefId> {
 289         Some(self.item_def_id)
 290     }
 291
 292     fn default_constness_for_trait_bounds(&self) -> ast::Constness {
 293         // FIXME: refactor this into a method
 294         let hir_id = self
 295             .tcx
 296             .hir()
 297             .as_local_hir_id(self.item_def_id)
 298             .expect("Non-local call to local provider is_const_fn");
 299
 300         let node = self.tcx.hir().get(hir_id);
 301         if let Some(fn_like) = FnLikeNode::from_node(node) {
 302             fn_like.constness()
 303         } else {
 304             ast::Constness::NotConst
 305         }
 306     }
 307
 308     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 309         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id))
 310     }
 311
 312     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 313         None
 314     }
 315
 316     fn allow_ty_infer(&self) -> bool {
 317         false
 318     }
 319
 320     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 321         self.tcx().sess.delay_span_bug(span, "bad placeholder type");
 322         self.tcx().types.err
 323     }
 324
 325     fn ct_infer(
 326         &self,
 327         _: Ty<'tcx>,
 328         _: Option<&ty::GenericParamDef>,
 329         span: Span,
 330     ) -> &'tcx Const<'tcx> {
 331         bad_placeholder_type(self.tcx(), vec![span]).emit();
 332
 333         self.tcx().consts.err
 334     }
 335
 336     fn projected_ty_from_poly_trait_ref(
 337         &self,
 338         span: Span,
 339         item_def_id: DefId,
 340         item_segment: &hir::PathSegment<'_>,
 341         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 342     ) -> Ty<'tcx> {
 343         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 344             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 345                 self,
 346                 self.tcx,
 347                 span,
 348                 item_def_id,
 349                 item_segment,
 350                 trait_ref.substs,
 351             );
 352             self.tcx().mk_projection(item_def_id, item_substs)
 353         } else {
 354             // There are no late-bound regions; we can just ignore the binder.
 355             struct_span_err!(
 356                 self.tcx().sess,
 357                 span,
 358                 E0212,
 359                 "cannot extract an associated type from a higher-ranked trait bound \
 360                  in this context"
 361             )
 362             .emit();
 363             self.tcx().types.err
 364         }
 365     }
 366
 367     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 368         // Types in item signatures are not normalized to avoid undue dependencies.
 369         ty
 370     }
 371
 372     fn set_tainted_by_errors(&self) {
 373         // There's no obvious place to track this, so just let it go.
 374     }
 375
 376     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 377         // There's no place to record types from signatures?
 378     }
 379 }
 380
 381 /// Returns the predicates defined on `item_def_id` of the form
 382 /// `X: Foo` where `X` is the type parameter `def_id`.
 383 fn type_param_predicates(
 384     tcx: TyCtxt<'_>,
 385     (item_def_id, def_id): (DefId, DefId),
 386 ) -> ty::GenericPredicates<'_> {
 387     use rustc_hir::*;
 388
 389     // In the AST, bounds can derive from two places. Either
 390     // written inline like `<T: Foo>` or in a where-clause like
 391     // `where T: Foo`.
 392
 393     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 394     let param_owner = tcx.hir().ty_param_owner(param_id);
 395     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 396     let generics = tcx.generics_of(param_owner_def_id);
 397     let index = generics.param_def_id_to_index[&def_id];
 398     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 399
 400     // Don't look for bounds where the type parameter isn't in scope.
 401     let parent =
 402         if item_def_id == param_owner_def_id { None } else { tcx.generics_of(item_def_id).parent };
 403
 404     let mut result = parent
 405         .map(|parent| {
 406             let icx = ItemCtxt::new(tcx, parent);
 407             icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 408         })
 409         .unwrap_or_default();
 410     let mut extend = None;
 411
 412     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 413     let ast_generics = match tcx.hir().get(item_hir_id) {
 414         Node::TraitItem(item) => &item.generics,
 415
 416         Node::ImplItem(item) => &item.generics,
 417
 418         Node::Item(item) => {
 419             match item.kind {
 420                 ItemKind::Fn(.., ref generics, _)
 421                 | ItemKind::Impl { ref generics, .. }
 422                 | ItemKind::TyAlias(_, ref generics)
 423                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 424                 | ItemKind::Enum(_, ref generics)
 425                 | ItemKind::Struct(_, ref generics)
 426                 | ItemKind::Union(_, ref generics) => generics,
 427                 ItemKind::Trait(_, _, ref generics, ..) => {
 428                     // Implied `Self: Trait` and supertrait bounds.
 429                     if param_id == item_hir_id {
 430                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 431                         extend =
 432                             Some((identity_trait_ref.without_const().to_predicate(), item.span));
 433                     }
 434                     generics
 435                 }
 436                 _ => return result,
 437             }
 438         }
 439
 440         Node::ForeignItem(item) => match item.kind {
 441             ForeignItemKind::Fn(_, _, ref generics) => generics,
 442             _ => return result,
 443         },
 444
 445         _ => return result,
 446     };
 447
 448     let icx = ItemCtxt::new(tcx, item_def_id);
 449     let extra_predicates = extend.into_iter().chain(
 450         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 451             .into_iter()
 452             .filter(|(predicate, _)| match predicate {
 453                 ty::Predicate::Trait(ref data, _) => data.skip_binder().self_ty().is_param(index),
 454                 _ => false,
 455             }),
 456     );
 457     result.predicates =
 458         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 459     result
 460 }
 461
 462 impl ItemCtxt<'tcx> {
 463     /// Finds bounds from `hir::Generics`. This requires scanning through the
 464     /// AST. We do this to avoid having to convert *all* the bounds, which
 465     /// would create artificial cycles. Instead, we can only convert the
 466     /// bounds for a type parameter `X` if `X::Foo` is used.
 467     fn type_parameter_bounds_in_generics(
 468         &self,
 469         ast_generics: &'tcx hir::Generics<'tcx>,
 470         param_id: hir::HirId,
 471         ty: Ty<'tcx>,
 472         only_self_bounds: OnlySelfBounds,
 473     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 474         let constness = self.default_constness_for_trait_bounds();
 475         let from_ty_params = ast_generics
 476             .params
 477             .iter()
 478             .filter_map(|param| match param.kind {
 479                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 480                 _ => None,
 481             })
 482             .flat_map(|bounds| bounds.iter())
 483             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 484
 485         let from_where_clauses = ast_generics
 486             .where_clause
 487             .predicates
 488             .iter()
 489             .filter_map(|wp| match *wp {
 490                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 491                 _ => None,
 492             })
 493             .flat_map(|bp| {
 494                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 495                     Some(ty)
 496                 } else if !only_self_bounds.0 {
 497                     Some(self.to_ty(&bp.bounded_ty))
 498                 } else {
 499                     None
 500                 };
 501                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 502             })
 503             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 504
 505         from_ty_params.chain(from_where_clauses).collect()
 506     }
 507 }
 508
 509 /// Tests whether this is the AST for a reference to the type
 510 /// parameter with ID `param_id`. We use this so as to avoid running
 511 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 512 /// conversion of the type to avoid inducing unnecessary cycles.
 513 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 514     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 515         match path.res {
 516             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 517                 def_id == tcx.hir().local_def_id(param_id)
 518             }
 519             _ => false,
 520         }
 521     } else {
 522         false
 523     }
 524 }
 525
 526 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 527     let it = tcx.hir().expect_item(item_id);
 528     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 529     let def_id = tcx.hir().local_def_id(item_id);
 530     match it.kind {
 531         // These don't define types.
 532         hir::ItemKind::ExternCrate(_)
 533         | hir::ItemKind::Use(..)
 534         | hir::ItemKind::Mod(_)
 535         | hir::ItemKind::GlobalAsm(_) => {}
 536         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 537             for item in foreign_mod.items {
 538                 let def_id = tcx.hir().local_def_id(item.hir_id);
 539                 tcx.generics_of(def_id);
 540                 tcx.type_of(def_id);
 541                 tcx.predicates_of(def_id);
 542                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 543                     tcx.fn_sig(def_id);
 544                 }
 545             }
 546         }
 547         hir::ItemKind::Enum(ref enum_definition, _) => {
 548             tcx.generics_of(def_id);
 549             tcx.type_of(def_id);
 550             tcx.predicates_of(def_id);
 551             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 552         }
 553         hir::ItemKind::Impl { .. } => {
 554             tcx.generics_of(def_id);
 555             tcx.type_of(def_id);
 556             tcx.impl_trait_ref(def_id);
 557             tcx.predicates_of(def_id);
 558         }
 559         hir::ItemKind::Trait(..) => {
 560             tcx.generics_of(def_id);
 561             tcx.trait_def(def_id);
 562             tcx.at(it.span).super_predicates_of(def_id);
 563             tcx.predicates_of(def_id);
 564         }
 565         hir::ItemKind::TraitAlias(..) => {
 566             tcx.generics_of(def_id);
 567             tcx.at(it.span).super_predicates_of(def_id);
 568             tcx.predicates_of(def_id);
 569         }
 570         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 571             tcx.generics_of(def_id);
 572             tcx.type_of(def_id);
 573             tcx.predicates_of(def_id);
 574
 575             for f in struct_def.fields() {
 576                 let def_id = tcx.hir().local_def_id(f.hir_id);
 577                 tcx.generics_of(def_id);
 578                 tcx.type_of(def_id);
 579                 tcx.predicates_of(def_id);
 580             }
 581
 582             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 583                 convert_variant_ctor(tcx, ctor_hir_id);
 584             }
 585         }
 586
 587         // Desugared from `impl Trait`, so visited by the function's return type.
 588         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 589
 590         hir::ItemKind::OpaqueTy(..)
 591         | hir::ItemKind::TyAlias(..)
 592         | hir::ItemKind::Static(..)
 593         | hir::ItemKind::Const(..)
 594         | hir::ItemKind::Fn(..) => {
 595             tcx.generics_of(def_id);
 596             tcx.type_of(def_id);
 597             tcx.predicates_of(def_id);
 598             if let hir::ItemKind::Fn(..) = it.kind {
 599                 tcx.fn_sig(def_id);
 600             }
 601         }
 602     }
 603 }
 604
 605 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 606     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 607     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 608     tcx.generics_of(def_id);
 609
 610     match trait_item.kind {
 611         hir::TraitItemKind::Const(..)
 612         | hir::TraitItemKind::Type(_, Some(_))
 613         | hir::TraitItemKind::Method(..) => {
 614             tcx.type_of(def_id);
 615             if let hir::TraitItemKind::Method(..) = trait_item.kind {
 616                 tcx.fn_sig(def_id);
 617             }
 618         }
 619
 620         hir::TraitItemKind::Type(_, None) => {}
 621     };
 622
 623     tcx.predicates_of(def_id);
 624 }
 625
 626 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 627     let def_id = tcx.hir().local_def_id(impl_item_id);
 628     tcx.generics_of(def_id);
 629     tcx.type_of(def_id);
 630     tcx.predicates_of(def_id);
 631     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
 632         tcx.fn_sig(def_id);
 633     }
 634 }
 635
 636 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 637     let def_id = tcx.hir().local_def_id(ctor_id);
 638     tcx.generics_of(def_id);
 639     tcx.type_of(def_id);
 640     tcx.predicates_of(def_id);
 641 }
 642
 643 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 644     let def = tcx.adt_def(def_id);
 645     let repr_type = def.repr.discr_type();
 646     let initial = repr_type.initial_discriminant(tcx);
 647     let mut prev_discr = None::<Discr<'_>>;
 648
 649     // fill the discriminant values and field types
 650     for variant in variants {
 651         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 652         prev_discr = Some(
 653             if let Some(ref e) = variant.disr_expr {
 654                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 655                 def.eval_explicit_discr(tcx, expr_did)
 656             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 657                 Some(discr)
 658             } else {
 659                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 660                     .span_label(
 661                         variant.span,
 662                         format!("overflowed on value after {}", prev_discr.unwrap()),
 663                     )
 664                     .note(&format!(
 665                         "explicitly set `{} = {}` if that is desired outcome",
 666                         variant.ident, wrapped_discr
 667                     ))
 668                     .emit();
 669                 None
 670             }
 671             .unwrap_or(wrapped_discr),
 672         );
 673
 674         for f in variant.data.fields() {
 675             let def_id = tcx.hir().local_def_id(f.hir_id);
 676             tcx.generics_of(def_id);
 677             tcx.type_of(def_id);
 678             tcx.predicates_of(def_id);
 679         }
 680
 681         // Convert the ctor, if any. This also registers the variant as
 682         // an item.
 683         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 684             convert_variant_ctor(tcx, ctor_hir_id);
 685         }
 686     }
 687 }
 688
 689 fn convert_variant(
 690     tcx: TyCtxt<'_>,
 691     variant_did: Option<DefId>,
 692     ctor_did: Option<DefId>,
 693     ident: Ident,
 694     discr: ty::VariantDiscr,
 695     def: &hir::VariantData<'_>,
 696     adt_kind: ty::AdtKind,
 697     parent_did: DefId,
 698 ) -> ty::VariantDef {
 699     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 700     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 701     let fields = def
 702         .fields()
 703         .iter()
 704         .map(|f| {
 705             let fid = tcx.hir().local_def_id(f.hir_id);
 706             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 707             if let Some(prev_span) = dup_span {
 708                 struct_span_err!(
 709                     tcx.sess,
 710                     f.span,
 711                     E0124,
 712                     "field `{}` is already declared",
 713                     f.ident
 714                 )
 715                 .span_label(f.span, "field already declared")
 716                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 717                 .emit();
 718             } else {
 719                 seen_fields.insert(f.ident.modern(), f.span);
 720             }
 721
 722             ty::FieldDef {
 723                 did: fid,
 724                 ident: f.ident,
 725                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 726             }
 727         })
 728         .collect();
 729     let recovered = match def {
 730         hir::VariantData::Struct(_, r) => *r,
 731         _ => false,
 732     };
 733     ty::VariantDef::new(
 734         tcx,
 735         ident,
 736         variant_did,
 737         ctor_did,
 738         discr,
 739         fields,
 740         CtorKind::from_hir(def),
 741         adt_kind,
 742         parent_did,
 743         recovered,
 744     )
 745 }
 746
 747 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 748     use rustc_hir::*;
 749
 750     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 751     let item = match tcx.hir().get(hir_id) {
 752         Node::Item(item) => item,
 753         _ => bug!(),
 754     };
 755
 756     let repr = ReprOptions::new(tcx, def_id);
 757     let (kind, variants) = match item.kind {
 758         ItemKind::Enum(ref def, _) => {
 759             let mut distance_from_explicit = 0;
 760             let variants = def
 761                 .variants
 762                 .iter()
 763                 .map(|v| {
 764                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 765                     let ctor_did =
 766                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 767
 768                     let discr = if let Some(ref e) = v.disr_expr {
 769                         distance_from_explicit = 0;
 770                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 771                     } else {
 772                         ty::VariantDiscr::Relative(distance_from_explicit)
 773                     };
 774                     distance_from_explicit += 1;
 775
 776                     convert_variant(
 777                         tcx,
 778                         variant_did,
 779                         ctor_did,
 780                         v.ident,
 781                         discr,
 782                         &v.data,
 783                         AdtKind::Enum,
 784                         def_id,
 785                     )
 786                 })
 787                 .collect();
 788
 789             (AdtKind::Enum, variants)
 790         }
 791         ItemKind::Struct(ref def, _) => {
 792             let variant_did = None;
 793             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 794
 795             let variants = std::iter::once(convert_variant(
 796                 tcx,
 797                 variant_did,
 798                 ctor_did,
 799                 item.ident,
 800                 ty::VariantDiscr::Relative(0),
 801                 def,
 802                 AdtKind::Struct,
 803                 def_id,
 804             ))
 805             .collect();
 806
 807             (AdtKind::Struct, variants)
 808         }
 809         ItemKind::Union(ref def, _) => {
 810             let variant_did = None;
 811             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 812
 813             let variants = std::iter::once(convert_variant(
 814                 tcx,
 815                 variant_did,
 816                 ctor_did,
 817                 item.ident,
 818                 ty::VariantDiscr::Relative(0),
 819                 def,
 820                 AdtKind::Union,
 821                 def_id,
 822             ))
 823             .collect();
 824
 825             (AdtKind::Union, variants)
 826         }
 827         _ => bug!(),
 828     };
 829     tcx.alloc_adt_def(def_id, kind, variants, repr)
 830 }
 831
 832 /// Ensures that the super-predicates of the trait with a `DefId`
 833 /// of `trait_def_id` are converted and stored. This also ensures that
 834 /// the transitive super-predicates are converted.
 835 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 836     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 837     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 838
 839     let item = match tcx.hir().get(trait_hir_id) {
 840         Node::Item(item) => item,
 841         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 842     };
 843
 844     let (generics, bounds) = match item.kind {
 845         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 846         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 847         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 848     };
 849
 850     let icx = ItemCtxt::new(tcx, trait_def_id);
 851
 852     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 853     let self_param_ty = tcx.types.self_param;
 854     let superbounds1 =
 855         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 856
 857     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 858
 859     // Convert any explicit superbounds in the where-clause,
 860     // e.g., `trait Foo where Self: Bar`.
 861     // In the case of trait aliases, however, we include all bounds in the where-clause,
 862     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 863     // as one of its "superpredicates".
 864     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 865     let superbounds2 = icx.type_parameter_bounds_in_generics(
 866         generics,
 867         item.hir_id,
 868         self_param_ty,
 869         OnlySelfBounds(!is_trait_alias),
 870     );
 871
 872     // Combine the two lists to form the complete set of superbounds:
 873     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
 874
 875     // Now require that immediate supertraits are converted,
 876     // which will, in turn, reach indirect supertraits.
 877     for &(pred, span) in superbounds {
 878         debug!("superbound: {:?}", pred);
 879         if let ty::Predicate::Trait(bound, _) = pred {
 880             tcx.at(span).super_predicates_of(bound.def_id());
 881         }
 882     }
 883
 884     ty::GenericPredicates { parent: None, predicates: superbounds }
 885 }
 886
 887 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 888     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 889     let item = tcx.hir().expect_item(hir_id);
 890
 891     let (is_auto, unsafety) = match item.kind {
 892         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 893         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 894         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 895     };
 896
 897     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 898     if paren_sugar && !tcx.features().unboxed_closures {
 899         tcx.sess
 900             .struct_span_err(
 901                 item.span,
 902                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 903              which traits can use parenthetical notation",
 904             )
 905             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
 906             .emit();
 907     }
 908
 909     let is_marker = tcx.has_attr(def_id, sym::marker);
 910     let def_path_hash = tcx.def_path_hash(def_id);
 911     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 912     tcx.arena.alloc(def)
 913 }
 914
 915 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 916     struct LateBoundRegionsDetector<'tcx> {
 917         tcx: TyCtxt<'tcx>,
 918         outer_index: ty::DebruijnIndex,
 919         has_late_bound_regions: Option<Span>,
 920     }
 921
 922     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 923         type Map = Map<'tcx>;
 924
 925         fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 926             NestedVisitorMap::None
 927         }
 928
 929         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
 930             if self.has_late_bound_regions.is_some() {
 931                 return;
 932             }
 933             match ty.kind {
 934                 hir::TyKind::BareFn(..) => {
 935                     self.outer_index.shift_in(1);
 936                     intravisit::walk_ty(self, ty);
 937                     self.outer_index.shift_out(1);
 938                 }
 939                 _ => intravisit::walk_ty(self, ty),
 940             }
 941         }
 942
 943         fn visit_poly_trait_ref(
 944             &mut self,
 945             tr: &'tcx hir::PolyTraitRef<'tcx>,
 946             m: hir::TraitBoundModifier,
 947         ) {
 948             if self.has_late_bound_regions.is_some() {
 949                 return;
 950             }
 951             self.outer_index.shift_in(1);
 952             intravisit::walk_poly_trait_ref(self, tr, m);
 953             self.outer_index.shift_out(1);
 954         }
 955
 956         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 957             if self.has_late_bound_regions.is_some() {
 958                 return;
 959             }
 960
 961             match self.tcx.named_region(lt.hir_id) {
 962                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 963                 Some(rl::Region::LateBound(debruijn, _, _))
 964                 | Some(rl::Region::LateBoundAnon(debruijn, _))
 965                     if debruijn < self.outer_index => {}
 966                 Some(rl::Region::LateBound(..))
 967                 | Some(rl::Region::LateBoundAnon(..))
 968                 | Some(rl::Region::Free(..))
 969                 | None => {
 970                     self.has_late_bound_regions = Some(lt.span);
 971                 }
 972             }
 973         }
 974     }
 975
 976     fn has_late_bound_regions<'tcx>(
 977         tcx: TyCtxt<'tcx>,
 978         generics: &'tcx hir::Generics<'tcx>,
 979         decl: &'tcx hir::FnDecl<'tcx>,
 980     ) -> Option<Span> {
 981         let mut visitor = LateBoundRegionsDetector {
 982             tcx,
 983             outer_index: ty::INNERMOST,
 984             has_late_bound_regions: None,
 985         };
 986         for param in generics.params {
 987             if let GenericParamKind::Lifetime { .. } = param.kind {
 988                 if tcx.is_late_bound(param.hir_id) {
 989                     return Some(param.span);
 990                 }
 991             }
 992         }
 993         visitor.visit_fn_decl(decl);
 994         visitor.has_late_bound_regions
 995     }
 996
 997     match node {
 998         Node::TraitItem(item) => match item.kind {
 999             hir::TraitItemKind::Method(ref sig, _) => {
1000                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1001             }
1002             _ => None,
1003         },
1004         Node::ImplItem(item) => match item.kind {
1005             hir::ImplItemKind::Method(ref sig, _) => {
1006                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1007             }
1008             _ => None,
1009         },
1010         Node::ForeignItem(item) => match item.kind {
1011             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1012                 has_late_bound_regions(tcx, generics, fn_decl)
1013             }
1014             _ => None,
1015         },
1016         Node::Item(item) => match item.kind {
1017             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1018                 has_late_bound_regions(tcx, generics, &sig.decl)
1019             }
1020             _ => None,
1021         },
1022         _ => None,
1023     }
1024 }
1025
1026 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
1027     use rustc_hir::*;
1028
1029     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1030
1031     let node = tcx.hir().get(hir_id);
1032     let parent_def_id = match node {
1033         Node::ImplItem(_)
1034         | Node::TraitItem(_)
1035         | Node::Variant(_)
1036         | Node::Ctor(..)
1037         | Node::Field(_) => {
1038             let parent_id = tcx.hir().get_parent_item(hir_id);
1039             Some(tcx.hir().local_def_id(parent_id))
1040         }
1041         // FIXME(#43408) enable this always when we get lazy normalization.
1042         Node::AnonConst(_) => {
1043             // HACK(eddyb) this provides the correct generics when
1044             // `feature(const_generics)` is enabled, so that const expressions
1045             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1046             if tcx.features().const_generics {
1047                 let parent_id = tcx.hir().get_parent_item(hir_id);
1048                 Some(tcx.hir().local_def_id(parent_id))
1049             } else {
1050                 None
1051             }
1052         }
1053         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1054             Some(tcx.closure_base_def_id(def_id))
1055         }
1056         Node::Item(item) => match item.kind {
1057             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
1058             _ => None,
1059         },
1060         _ => None,
1061     };
1062
1063     let mut opt_self = None;
1064     let mut allow_defaults = false;
1065
1066     let no_generics = hir::Generics::empty();
1067     let ast_generics = match node {
1068         Node::TraitItem(item) => &item.generics,
1069
1070         Node::ImplItem(item) => &item.generics,
1071
1072         Node::Item(item) => {
1073             match item.kind {
1074                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl { ref generics, .. } => generics,
1075
1076                 ItemKind::TyAlias(_, ref generics)
1077                 | ItemKind::Enum(_, ref generics)
1078                 | ItemKind::Struct(_, ref generics)
1079                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1080                 | ItemKind::Union(_, ref generics) => {
1081                     allow_defaults = true;
1082                     generics
1083                 }
1084
1085                 ItemKind::Trait(_, _, ref generics, ..)
1086                 | ItemKind::TraitAlias(ref generics, ..) => {
1087                     // Add in the self type parameter.
1088                     //
1089                     // Something of a hack: use the node id for the trait, also as
1090                     // the node id for the Self type parameter.
1091                     let param_id = item.hir_id;
1092
1093                     opt_self = Some(ty::GenericParamDef {
1094                         index: 0,
1095                         name: kw::SelfUpper,
1096                         def_id: tcx.hir().local_def_id(param_id),
1097                         pure_wrt_drop: false,
1098                         kind: ty::GenericParamDefKind::Type {
1099                             has_default: false,
1100                             object_lifetime_default: rl::Set1::Empty,
1101                             synthetic: None,
1102                         },
1103                     });
1104
1105                     allow_defaults = true;
1106                     generics
1107                 }
1108
1109                 _ => &no_generics,
1110             }
1111         }
1112
1113         Node::ForeignItem(item) => match item.kind {
1114             ForeignItemKind::Static(..) => &no_generics,
1115             ForeignItemKind::Fn(_, _, ref generics) => generics,
1116             ForeignItemKind::Type => &no_generics,
1117         },
1118
1119         _ => &no_generics,
1120     };
1121
1122     let has_self = opt_self.is_some();
1123     let mut parent_has_self = false;
1124     let mut own_start = has_self as u32;
1125     let parent_count = parent_def_id.map_or(0, |def_id| {
1126         let generics = tcx.generics_of(def_id);
1127         assert_eq!(has_self, false);
1128         parent_has_self = generics.has_self;
1129         own_start = generics.count() as u32;
1130         generics.parent_count + generics.params.len()
1131     });
1132
1133     let mut params: Vec<_> = opt_self.into_iter().collect();
1134
1135     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1136     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1137         name: param.name.ident().name,
1138         index: own_start + i as u32,
1139         def_id: tcx.hir().local_def_id(param.hir_id),
1140         pure_wrt_drop: param.pure_wrt_drop,
1141         kind: ty::GenericParamDefKind::Lifetime,
1142     }));
1143
1144     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1145
1146     // Now create the real type parameters.
1147     let type_start = own_start - has_self as u32 + params.len() as u32;
1148     let mut i = 0;
1149     params.extend(ast_generics.params.iter().filter_map(|param| {
1150         let kind = match param.kind {
1151             GenericParamKind::Type { ref default, synthetic, .. } => {
1152                 if !allow_defaults && default.is_some() {
1153                     if !tcx.features().default_type_parameter_fallback {
1154                         tcx.struct_span_lint_hir(
1155                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1156                             param.hir_id,
1157                             param.span,
1158                             |lint| {
1159                                 lint.build(&format!(
1160                                     "defaults for type parameters are only allowed in \
1161                                         `struct`, `enum`, `type`, or `trait` definitions."
1162                                 ))
1163                                 .emit();
1164                             },
1165                         );
1166                     }
1167                 }
1168
1169                 ty::GenericParamDefKind::Type {
1170                     has_default: default.is_some(),
1171                     object_lifetime_default: object_lifetime_defaults
1172                         .as_ref()
1173                         .map_or(rl::Set1::Empty, |o| o[i]),
1174                     synthetic,
1175                 }
1176             }
1177             GenericParamKind::Const { .. } => ty::GenericParamDefKind::Const,
1178             _ => return None,
1179         };
1180
1181         let param_def = ty::GenericParamDef {
1182             index: type_start + i as u32,
1183             name: param.name.ident().name,
1184             def_id: tcx.hir().local_def_id(param.hir_id),
1185             pure_wrt_drop: param.pure_wrt_drop,
1186             kind,
1187         };
1188         i += 1;
1189         Some(param_def)
1190     }));
1191
1192     // provide junk type parameter defs - the only place that
1193     // cares about anything but the length is instantiation,
1194     // and we don't do that for closures.
1195     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1196         let dummy_args = if gen.is_some() {
1197             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>"][..]
1198         } else {
1199             &["<closure_kind>", "<closure_signature>"][..]
1200         };
1201
1202         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1203             index: type_start + i as u32,
1204             name: Symbol::intern(arg),
1205             def_id,
1206             pure_wrt_drop: false,
1207             kind: ty::GenericParamDefKind::Type {
1208                 has_default: false,
1209                 object_lifetime_default: rl::Set1::Empty,
1210                 synthetic: None,
1211             },
1212         }));
1213
1214         if let Some(upvars) = tcx.upvars(def_id) {
1215             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1216                 ty::GenericParamDef {
1217                     index: type_start + i,
1218                     name: Symbol::intern("<upvar>"),
1219                     def_id,
1220                     pure_wrt_drop: false,
1221                     kind: ty::GenericParamDefKind::Type {
1222                         has_default: false,
1223                         object_lifetime_default: rl::Set1::Empty,
1224                         synthetic: None,
1225                     },
1226                 }
1227             }));
1228         }
1229     }
1230
1231     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1232
1233     tcx.arena.alloc(ty::Generics {
1234         parent: parent_def_id,
1235         parent_count,
1236         params,
1237         param_def_id_to_index,
1238         has_self: has_self || parent_has_self,
1239         has_late_bound_regions: has_late_bound_regions(tcx, node),
1240     })
1241 }
1242
1243 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1244     struct_span_err!(
1245         tcx.sess,
1246         span,
1247         E0202,
1248         "associated types are not yet supported in inherent impls (see #8995)"
1249     )
1250     .emit();
1251 }
1252
1253 fn infer_placeholder_type(
1254     tcx: TyCtxt<'_>,
1255     def_id: DefId,
1256     body_id: hir::BodyId,
1257     span: Span,
1258     item_ident: Ident,
1259 ) -> Ty<'_> {
1260     let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
1261
1262     // If this came from a free `const` or `static mut?` item,
1263     // then the user may have written e.g. `const A = 42;`.
1264     // In this case, the parser has stashed a diagnostic for
1265     // us to improve in typeck so we do that now.
1266     match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1267         Some(mut err) => {
1268             // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1269             // We are typeck and have the real type, so remove that and suggest the actual type.
1270             err.suggestions.clear();
1271             err.span_suggestion(
1272                 span,
1273                 "provide a type for the item",
1274                 format!("{}: {}", item_ident, ty),
1275                 Applicability::MachineApplicable,
1276             )
1277             .emit();
1278         }
1279         None => {
1280             let mut diag = bad_placeholder_type(tcx, vec![span]);
1281             if ty != tcx.types.err {
1282                 diag.span_suggestion(
1283                     span,
1284                     "replace `_` with the correct type",
1285                     ty.to_string(),
1286                     Applicability::MaybeIncorrect,
1287                 );
1288             }
1289             diag.emit();
1290         }
1291     }
1292
1293     ty
1294 }
1295
1296 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1297     use rustc_hir::*;
1298
1299     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1300
1301     let icx = ItemCtxt::new(tcx, def_id);
1302
1303     match tcx.hir().get(hir_id) {
1304         Node::TraitItem(item) => match item.kind {
1305             TraitItemKind::Method(..) => {
1306                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1307                 tcx.mk_fn_def(def_id, substs)
1308             }
1309             TraitItemKind::Const(ref ty, body_id) => body_id
1310                 .and_then(|body_id| {
1311                     if is_suggestable_infer_ty(ty) {
1312                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1313                     } else {
1314                         None
1315                     }
1316                 })
1317                 .unwrap_or_else(|| icx.to_ty(ty)),
1318             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1319             TraitItemKind::Type(_, None) => {
1320                 span_bug!(item.span, "associated type missing default");
1321             }
1322         },
1323
1324         Node::ImplItem(item) => match item.kind {
1325             ImplItemKind::Method(..) => {
1326                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1327                 tcx.mk_fn_def(def_id, substs)
1328             }
1329             ImplItemKind::Const(ref ty, body_id) => {
1330                 if is_suggestable_infer_ty(ty) {
1331                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1332                 } else {
1333                     icx.to_ty(ty)
1334                 }
1335             }
1336             ImplItemKind::OpaqueTy(_) => {
1337                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1338                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1339                 }
1340
1341                 find_opaque_ty_constraints(tcx, def_id)
1342             }
1343             ImplItemKind::TyAlias(ref ty) => {
1344                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1345                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1346                 }
1347
1348                 icx.to_ty(ty)
1349             }
1350         },
1351
1352         Node::Item(item) => {
1353             match item.kind {
1354                 ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
1355                     if is_suggestable_infer_ty(ty) {
1356                         infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1357                     } else {
1358                         icx.to_ty(ty)
1359                     }
1360                 }
1361                 ItemKind::TyAlias(ref self_ty, _) | ItemKind::Impl { ref self_ty, .. } => {
1362                     icx.to_ty(self_ty)
1363                 }
1364                 ItemKind::Fn(..) => {
1365                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1366                     tcx.mk_fn_def(def_id, substs)
1367                 }
1368                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1369                     let def = tcx.adt_def(def_id);
1370                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1371                     tcx.mk_adt(def, substs)
1372                 }
1373                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
1374                     find_opaque_ty_constraints(tcx, def_id)
1375                 }
1376                 // Opaque types desugared from `impl Trait`.
1377                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
1378                     tcx.typeck_tables_of(owner)
1379                         .concrete_opaque_types
1380                         .get(&def_id)
1381                         .map(|opaque| opaque.concrete_type)
1382                         .unwrap_or_else(|| {
1383                             // This can occur if some error in the
1384                             // owner fn prevented us from populating
1385                             // the `concrete_opaque_types` table.
1386                             tcx.sess.delay_span_bug(
1387                                 DUMMY_SP,
1388                                 &format!(
1389                                     "owner {:?} has no opaque type for {:?} in its tables",
1390                                     owner, def_id,
1391                                 ),
1392                             );
1393                             tcx.types.err
1394                         })
1395                 }
1396                 ItemKind::Trait(..)
1397                 | ItemKind::TraitAlias(..)
1398                 | ItemKind::Mod(..)
1399                 | ItemKind::ForeignMod(..)
1400                 | ItemKind::GlobalAsm(..)
1401                 | ItemKind::ExternCrate(..)
1402                 | ItemKind::Use(..) => {
1403                     span_bug!(
1404                         item.span,
1405                         "compute_type_of_item: unexpected item type: {:?}",
1406                         item.kind
1407                     );
1408                 }
1409             }
1410         }
1411
1412         Node::ForeignItem(foreign_item) => match foreign_item.kind {
1413             ForeignItemKind::Fn(..) => {
1414                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1415                 tcx.mk_fn_def(def_id, substs)
1416             }
1417             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1418             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1419         },
1420
1421         Node::Ctor(&ref def) | Node::Variant(hir::Variant { data: ref def, .. }) => match *def {
1422             VariantData::Unit(..) | VariantData::Struct(..) => {
1423                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1424             }
1425             VariantData::Tuple(..) => {
1426                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1427                 tcx.mk_fn_def(def_id, substs)
1428             }
1429         },
1430
1431         Node::Field(field) => icx.to_ty(&field.ty),
1432
1433         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) => {
1434             if gen.is_some() {
1435                 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1436             }
1437
1438             let substs = InternalSubsts::identity_for_item(tcx, def_id);
1439             tcx.mk_closure(def_id, substs)
1440         }
1441
1442         Node::AnonConst(_) => {
1443             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1444             match parent_node {
1445                 Node::Ty(&hir::Ty { kind: hir::TyKind::Array(_, ref constant), .. })
1446                 | Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref constant), .. })
1447                 | Node::Expr(&hir::Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1448                     if constant.hir_id == hir_id =>
1449                 {
1450                     tcx.types.usize
1451                 }
1452
1453                 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
1454                     tcx.adt_def(tcx.hir().get_parent_did(hir_id)).repr.discr_type().to_ty(tcx)
1455                 }
1456
1457                 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. })
1458                 | Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. })
1459                 | Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. })
1460                 | Node::TraitRef(..) => {
1461                     let path = match parent_node {
1462                         Node::Ty(&hir::Ty {
1463                             kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1464                             ..
1465                         })
1466                         | Node::Expr(&hir::Expr {
1467                             kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1468                             ..
1469                         }) => Some(&**path),
1470                         Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1471                             if let QPath::Resolved(_, ref path) = **path {
1472                                 Some(&**path)
1473                             } else {
1474                                 None
1475                             }
1476                         }
1477                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1478                         _ => None,
1479                     };
1480
1481                     if let Some(path) = path {
1482                         let arg_index = path
1483                             .segments
1484                             .iter()
1485                             .filter_map(|seg| seg.args.as_ref())
1486                             .map(|generic_args| generic_args.args.as_ref())
1487                             .find_map(|args| {
1488                                 args.iter()
1489                                     .filter(|arg| arg.is_const())
1490                                     .enumerate()
1491                                     .filter(|(_, arg)| arg.id() == hir_id)
1492                                     .map(|(index, _)| index)
1493                                     .next()
1494                             })
1495                             .unwrap_or_else(|| {
1496                                 bug!("no arg matching AnonConst in path");
1497                             });
1498
1499                         // We've encountered an `AnonConst` in some path, so we need to
1500                         // figure out which generic parameter it corresponds to and return
1501                         // the relevant type.
1502                         let generics = match path.res {
1503                             Res::Def(DefKind::Ctor(..), def_id) => {
1504                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1505                             }
1506                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1507                             Res::Err => return tcx.types.err,
1508                             res => {
1509                                 tcx.sess.delay_span_bug(
1510                                     DUMMY_SP,
1511                                     &format!("unexpected const parent path def {:?}", res,),
1512                                 );
1513                                 return tcx.types.err;
1514                             }
1515                         };
1516
1517                         generics
1518                             .params
1519                             .iter()
1520                             .filter(|param| {
1521                                 if let ty::GenericParamDefKind::Const = param.kind {
1522                                     true
1523                                 } else {
1524                                     false
1525                                 }
1526                             })
1527                             .nth(arg_index)
1528                             .map(|param| tcx.type_of(param.def_id))
1529                             // This is no generic parameter associated with the arg. This is
1530                             // probably from an extra arg where one is not needed.
1531                             .unwrap_or(tcx.types.err)
1532                     } else {
1533                         tcx.sess.delay_span_bug(
1534                             DUMMY_SP,
1535                             &format!("unexpected const parent path {:?}", parent_node,),
1536                         );
1537                         return tcx.types.err;
1538                     }
1539                 }
1540
1541                 x => {
1542                     tcx.sess.delay_span_bug(
1543                         DUMMY_SP,
1544                         &format!("unexpected const parent in type_of_def_id(): {:?}", x),
1545                     );
1546                     tcx.types.err
1547                 }
1548             }
1549         }
1550
1551         Node::GenericParam(param) => match &param.kind {
1552             hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1553             hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1554                 let ty = icx.to_ty(hir_ty);
1555                 if !tcx.features().const_compare_raw_pointers {
1556                     let err = match ty.peel_refs().kind {
1557                         ty::FnPtr(_) => Some("function pointers"),
1558                         ty::RawPtr(_) => Some("raw pointers"),
1559                         _ => None,
1560                     };
1561                     if let Some(unsupported_type) = err {
1562                         feature_err(
1563                             &tcx.sess.parse_sess,
1564                             sym::const_compare_raw_pointers,
1565                             hir_ty.span,
1566                             &format!(
1567                                 "using {} as const generic parameters is unstable",
1568                                 unsupported_type
1569                             ),
1570                         )
1571                         .emit();
1572                     };
1573                 }
1574                 if traits::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
1575                     .is_some()
1576                 {
1577                     struct_span_err!(
1578                         tcx.sess,
1579                         hir_ty.span,
1580                         E0741,
1581                         "the types of const generic parameters must derive `PartialEq` and `Eq`",
1582                     )
1583                     .span_label(
1584                         hir_ty.span,
1585                         format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1586                     )
1587                     .emit();
1588                 }
1589                 ty
1590             }
1591             x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1592         },
1593
1594         x => {
1595             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1596         }
1597     }
1598 }
1599
1600 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1601     use rustc_hir::{ImplItem, Item, TraitItem};
1602
1603     debug!("find_opaque_ty_constraints({:?})", def_id);
1604
1605     struct ConstraintLocator<'tcx> {
1606         tcx: TyCtxt<'tcx>,
1607         def_id: DefId,
1608         // (first found type span, actual type, mapping from the opaque type's generic
1609         // parameters to the concrete type's generic parameters)
1610         //
1611         // The mapping is an index for each use site of a generic parameter in the concrete type
1612         //
1613         // The indices index into the generic parameters on the opaque type.
1614         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1615     }
1616
1617     impl ConstraintLocator<'tcx> {
1618         fn check(&mut self, def_id: DefId) {
1619             // Don't try to check items that cannot possibly constrain the type.
1620             if !self.tcx.has_typeck_tables(def_id) {
1621                 debug!(
1622                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1623                     self.def_id, def_id,
1624                 );
1625                 return;
1626             }
1627             let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
1628             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1629                 debug!(
1630                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1631                     self.def_id, def_id, ty,
1632                 );
1633
1634                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1635                 let span = self.tcx.def_span(def_id);
1636                 // used to quickly look up the position of a generic parameter
1637                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1638                 // Skipping binder is ok, since we only use this to find generic parameters and
1639                 // their positions.
1640                 for (idx, subst) in substs.iter().enumerate() {
1641                     if let GenericArgKind::Type(ty) = subst.unpack() {
1642                         if let ty::Param(p) = ty.kind {
1643                             if index_map.insert(p, idx).is_some() {
1644                                 // There was already an entry for `p`, meaning a generic parameter
1645                                 // was used twice.
1646                                 self.tcx.sess.span_err(
1647                                     span,
1648                                     &format!(
1649                                         "defining opaque type use restricts opaque \
1650                                          type by using the generic parameter `{}` twice",
1651                                         p,
1652                                     ),
1653                                 );
1654                                 return;
1655                             }
1656                         } else {
1657                             self.tcx.sess.delay_span_bug(
1658                                 span,
1659                                 &format!(
1660                                     "non-defining opaque ty use in defining scope: {:?}, {:?}",
1661                                     concrete_type, substs,
1662                                 ),
1663                             );
1664                         }
1665                     }
1666                 }
1667                 // Compute the index within the opaque type for each generic parameter used in
1668                 // the concrete type.
1669                 let indices = concrete_type
1670                     .subst(self.tcx, substs)
1671                     .walk()
1672                     .filter_map(|t| match &t.kind {
1673                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1674                         _ => None,
1675                     })
1676                     .collect();
1677                 let is_param = |ty: Ty<'_>| match ty.kind {
1678                     ty::Param(_) => true,
1679                     _ => false,
1680                 };
1681                 let bad_substs: Vec<_> = substs
1682                     .iter()
1683                     .enumerate()
1684                     .filter_map(|(i, k)| {
1685                         if let GenericArgKind::Type(ty) = k.unpack() { Some((i, ty)) } else { None }
1686                     })
1687                     .filter(|(_, ty)| !is_param(ty))
1688                     .collect();
1689
1690                 if !bad_substs.is_empty() {
1691                     let identity_substs = InternalSubsts::identity_for_item(self.tcx, self.def_id);
1692                     for (i, bad_subst) in bad_substs {
1693                         self.tcx.sess.span_err(
1694                             span,
1695                             &format!(
1696                                 "defining opaque type use does not fully define opaque type: \
1697                             generic parameter `{}` is specified as concrete type `{}`",
1698                                 identity_substs.type_at(i),
1699                                 bad_subst
1700                             ),
1701                         );
1702                     }
1703                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1704                     let mut ty = concrete_type.walk().fuse();
1705                     let mut p_ty = prev_ty.walk().fuse();
1706                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1707                         // Type parameters are equal to any other type parameter for the purpose of
1708                         // concrete type equality, as it is possible to obtain the same type just
1709                         // by passing matching parameters to a function.
1710                         (ty::Param(_), ty::Param(_)) => true,
1711                         _ => t == p,
1712                     });
1713                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1714                         debug!("find_opaque_ty_constraints: span={:?}", span);
1715                         // Found different concrete types for the opaque type.
1716                         let mut err = self.tcx.sess.struct_span_err(
1717                             span,
1718                             "concrete type differs from previous defining opaque type use",
1719                         );
1720                         err.span_label(
1721                             span,
1722                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1723                         );
1724                         err.span_note(prev_span, "previous use here");
1725                         err.emit();
1726                     } else if indices != *prev_indices {
1727                         // Found "same" concrete types, but the generic parameter order differs.
1728                         let mut err = self.tcx.sess.struct_span_err(
1729                             span,
1730                             "concrete type's generic parameters differ from previous defining use",
1731                         );
1732                         use std::fmt::Write;
1733                         let mut s = String::new();
1734                         write!(s, "expected [").unwrap();
1735                         let list = |s: &mut String, indices: &Vec<usize>| {
1736                             let mut indices = indices.iter().cloned();
1737                             if let Some(first) = indices.next() {
1738                                 write!(s, "`{}`", substs[first]).unwrap();
1739                                 for i in indices {
1740                                     write!(s, ", `{}`", substs[i]).unwrap();
1741                                 }
1742                             }
1743                         };
1744                         list(&mut s, prev_indices);
1745                         write!(s, "], got [").unwrap();
1746                         list(&mut s, &indices);
1747                         write!(s, "]").unwrap();
1748                         err.span_label(span, s);
1749                         err.span_note(prev_span, "previous use here");
1750                         err.emit();
1751                     }
1752                 } else {
1753                     self.found = Some((span, concrete_type, indices));
1754                 }
1755             } else {
1756                 debug!(
1757                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1758                     self.def_id, def_id,
1759                 );
1760             }
1761         }
1762     }
1763
1764     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1765         type Map = Map<'tcx>;
1766
1767         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1768             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1769         }
1770         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
1771             debug!("find_existential_constraints: visiting {:?}", it);
1772             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1773             // The opaque type itself or its children are not within its reveal scope.
1774             if def_id != self.def_id {
1775                 self.check(def_id);
1776                 intravisit::walk_item(self, it);
1777             }
1778         }
1779         fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
1780             debug!("find_existential_constraints: visiting {:?}", it);
1781             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1782             // The opaque type itself or its children are not within its reveal scope.
1783             if def_id != self.def_id {
1784                 self.check(def_id);
1785                 intravisit::walk_impl_item(self, it);
1786             }
1787         }
1788         fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
1789             debug!("find_existential_constraints: visiting {:?}", it);
1790             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1791             self.check(def_id);
1792             intravisit::walk_trait_item(self, it);
1793         }
1794     }
1795
1796     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1797     let scope = tcx.hir().get_defining_scope(hir_id);
1798     let mut locator = ConstraintLocator { def_id, tcx, found: None };
1799
1800     debug!("find_opaque_ty_constraints: scope={:?}", scope);
1801
1802     if scope == hir::CRATE_HIR_ID {
1803         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1804     } else {
1805         debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1806         match tcx.hir().get(scope) {
1807             // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1808             // This allows our visitor to process the defining item itself, causing
1809             // it to pick up any 'sibling' defining uses.
1810             //
1811             // For example, this code:
1812             // ```
1813             // fn foo() {
1814             //     type Blah = impl Debug;
1815             //     let my_closure = || -> Blah { true };
1816             // }
1817             // ```
1818             //
1819             // requires us to explicitly process `foo()` in order
1820             // to notice the defining usage of `Blah`.
1821             Node::Item(ref it) => locator.visit_item(it),
1822             Node::ImplItem(ref it) => locator.visit_impl_item(it),
1823             Node::TraitItem(ref it) => locator.visit_trait_item(it),
1824             other => bug!("{:?} is not a valid scope for an opaque type item", other),
1825         }
1826     }
1827
1828     match locator.found {
1829         Some((_, ty, _)) => ty,
1830         None => {
1831             let span = tcx.def_span(def_id);
1832             tcx.sess.span_err(span, "could not find defining uses");
1833             tcx.types.err
1834         }
1835     }
1836 }
1837
1838 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1839     generic_args
1840         .iter()
1841         .filter_map(|arg| match arg {
1842             hir::GenericArg::Type(ty) => Some(ty),
1843             _ => None,
1844         })
1845         .any(is_suggestable_infer_ty)
1846 }
1847
1848 /// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
1849 /// use inference to provide suggestions for the appropriate type if possible.
1850 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1851     use hir::TyKind::*;
1852     match &ty.kind {
1853         Infer => true,
1854         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1855         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1856         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1857         Def(_, generic_args) => are_suggestable_generic_args(generic_args),
1858         Path(hir::QPath::TypeRelative(ty, segment)) => {
1859             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1860         }
1861         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1862             ty_opt.map_or(false, is_suggestable_infer_ty)
1863                 || segments
1864                     .iter()
1865                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1866         }
1867         _ => false,
1868     }
1869 }
1870
1871 pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1872     if let hir::FunctionRetTy::Return(ref ty) = output {
1873         if is_suggestable_infer_ty(ty) {
1874             return Some(&**ty);
1875         }
1876     }
1877     None
1878 }
1879
1880 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1881     use rustc_hir::Node::*;
1882     use rustc_hir::*;
1883
1884     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1885
1886     let icx = ItemCtxt::new(tcx, def_id);
1887
1888     match tcx.hir().get(hir_id) {
1889         TraitItem(hir::TraitItem {
1890             kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1891             ident,
1892             generics,
1893             ..
1894         })
1895         | ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
1896         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1897             match get_infer_ret_ty(&sig.decl.output) {
1898                 Some(ty) => {
1899                     let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1900                     let mut visitor = PlaceholderHirTyCollector::default();
1901                     visitor.visit_ty(ty);
1902                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1903                     let ret_ty = fn_sig.output();
1904                     if ret_ty != tcx.types.err {
1905                         diag.span_suggestion(
1906                             ty.span,
1907                             "replace with the correct return type",
1908                             ret_ty.to_string(),
1909                             Applicability::MaybeIncorrect,
1910                         );
1911                     }
1912                     diag.emit();
1913                     ty::Binder::bind(fn_sig)
1914                 }
1915                 None => AstConv::ty_of_fn(
1916                     &icx,
1917                     sig.header.unsafety,
1918                     sig.header.abi,
1919                     &sig.decl,
1920                     &generics.params[..],
1921                     Some(ident.span),
1922                 ),
1923             }
1924         }
1925
1926         TraitItem(hir::TraitItem {
1927             kind: TraitItemKind::Method(FnSig { header, decl }, _),
1928             ident,
1929             generics,
1930             ..
1931         }) => AstConv::ty_of_fn(
1932             &icx,
1933             header.unsafety,
1934             header.abi,
1935             decl,
1936             &generics.params[..],
1937             Some(ident.span),
1938         ),
1939
1940         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
1941             let abi = tcx.hir().get_foreign_abi(hir_id);
1942             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1943         }
1944
1945         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1946             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1947             let inputs =
1948                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1949             ty::Binder::bind(tcx.mk_fn_sig(
1950                 inputs,
1951                 ty,
1952                 false,
1953                 hir::Unsafety::Normal,
1954                 abi::Abi::Rust,
1955             ))
1956         }
1957
1958         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1959             // Closure signatures are not like other function
1960             // signatures and cannot be accessed through `fn_sig`. For
1961             // example, a closure signature excludes the `self`
1962             // argument. In any case they are embedded within the
1963             // closure type as part of the `ClosureSubsts`.
1964             //
1965             // To get
1966             // the signature of a closure, you should use the
1967             // `closure_sig` method on the `ClosureSubsts`:
1968             //
1969             //    closure_substs.sig(def_id, tcx)
1970             //
1971             // or, inside of an inference context, you can use
1972             //
1973             //    infcx.closure_sig(def_id, closure_substs)
1974             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1975         }
1976
1977         x => {
1978             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1979         }
1980     }
1981 }
1982
1983 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1984     let icx = ItemCtxt::new(tcx, def_id);
1985
1986     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1987     match tcx.hir().expect_item(hir_id).kind {
1988         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
1989             let selfty = tcx.type_of(def_id);
1990             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1991         }),
1992         _ => bug!(),
1993     }
1994 }
1995
1996 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1997     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1998     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1999     let item = tcx.hir().expect_item(hir_id);
2000     match &item.kind {
2001         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative, .. } => {
2002             if is_rustc_reservation {
2003                 tcx.sess.span_err(item.span, "reservation impls can't be negative");
2004             }
2005             ty::ImplPolarity::Negative
2006         }
2007         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
2008             if is_rustc_reservation {
2009                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2010             }
2011             ty::ImplPolarity::Positive
2012         }
2013         hir::ItemKind::Impl {
2014             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
2015         } => {
2016             if is_rustc_reservation {
2017                 ty::ImplPolarity::Reservation
2018             } else {
2019                 ty::ImplPolarity::Positive
2020             }
2021         }
2022         ref item => bug!("impl_polarity: {:?} not an impl", item),
2023     }
2024 }
2025
2026 /// Returns the early-bound lifetimes declared in this generics
2027 /// listing. For anything other than fns/methods, this is just all
2028 /// the lifetimes that are declared. For fns or methods, we have to
2029 /// screen out those that do not appear in any where-clauses etc using
2030 /// `resolve_lifetime::early_bound_lifetimes`.
2031 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2032     tcx: TyCtxt<'tcx>,
2033     generics: &'a hir::Generics<'a>,
2034 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2035     generics.params.iter().filter(move |param| match param.kind {
2036         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2037         _ => false,
2038     })
2039 }
2040
2041 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2042 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2043 /// inferred constraints concerning which regions outlive other regions.
2044 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2045     debug!("predicates_defined_on({:?})", def_id);
2046     let mut result = tcx.explicit_predicates_of(def_id);
2047     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2048     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2049     if !inferred_outlives.is_empty() {
2050         debug!(
2051             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2052             def_id, inferred_outlives,
2053         );
2054         if result.predicates.is_empty() {
2055             result.predicates = inferred_outlives;
2056         } else {
2057             result.predicates = tcx
2058                 .arena
2059                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2060         }
2061     }
2062     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2063     result
2064 }
2065
2066 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2067 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2068 /// `Self: Trait` predicates for traits.
2069 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2070     let mut result = tcx.predicates_defined_on(def_id);
2071
2072     if tcx.is_trait(def_id) {
2073         // For traits, add `Self: Trait` predicate. This is
2074         // not part of the predicates that a user writes, but it
2075         // is something that one must prove in order to invoke a
2076         // method or project an associated type.
2077         //
2078         // In the chalk setup, this predicate is not part of the
2079         // "predicates" for a trait item. But it is useful in
2080         // rustc because if you directly (e.g.) invoke a trait
2081         // method like `Trait::method(...)`, you must naturally
2082         // prove that the trait applies to the types that were
2083         // used, and adding the predicate into this list ensures
2084         // that this is done.
2085         let span = tcx.def_span(def_id);
2086         result.predicates =
2087             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2088                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(),
2089                 span,
2090             ))));
2091     }
2092     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2093     result
2094 }
2095
2096 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2097 /// N.B., this does not include any implied/inferred constraints.
2098 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2099     use rustc_data_structures::fx::FxHashSet;
2100     use rustc_hir::*;
2101
2102     debug!("explicit_predicates_of(def_id={:?})", def_id);
2103
2104     /// A data structure with unique elements, which preserves order of insertion.
2105     /// Preserving the order of insertion is important here so as not to break
2106     /// compile-fail UI tests.
2107     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2108     struct UniquePredicates<'tcx> {
2109         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2110         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2111     }
2112
2113     impl<'tcx> UniquePredicates<'tcx> {
2114         fn new() -> Self {
2115             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
2116         }
2117
2118         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2119             if self.uniques.insert(value) {
2120                 self.predicates.push(value);
2121             }
2122         }
2123
2124         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2125             for value in iter {
2126                 self.push(value);
2127             }
2128         }
2129     }
2130
2131     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2132     let node = tcx.hir().get(hir_id);
2133
2134     let mut is_trait = None;
2135     let mut is_default_impl_trait = None;
2136
2137     let icx = ItemCtxt::new(tcx, def_id);
2138     let constness = icx.default_constness_for_trait_bounds();
2139
2140     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2141
2142     let mut predicates = UniquePredicates::new();
2143
2144     let ast_generics = match node {
2145         Node::TraitItem(item) => &item.generics,
2146
2147         Node::ImplItem(item) => match item.kind {
2148             ImplItemKind::OpaqueTy(ref bounds) => {
2149                 ty::print::with_no_queries(|| {
2150                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2151                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2152                     debug!(
2153                         "explicit_predicates_of({:?}): created opaque type {:?}",
2154                         def_id, opaque_ty
2155                     );
2156
2157                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2158                     let bounds = AstConv::compute_bounds(
2159                         &icx,
2160                         opaque_ty,
2161                         bounds,
2162                         SizedByDefault::Yes,
2163                         tcx.def_span(def_id),
2164                     );
2165
2166                     predicates.extend(bounds.predicates(tcx, opaque_ty));
2167                     &item.generics
2168                 })
2169             }
2170             _ => &item.generics,
2171         },
2172
2173         Node::Item(item) => {
2174             match item.kind {
2175                 ItemKind::Impl { defaultness, ref generics, .. } => {
2176                     if defaultness.is_default() {
2177                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2178                     }
2179                     generics
2180                 }
2181                 ItemKind::Fn(.., ref generics, _)
2182                 | ItemKind::TyAlias(_, ref generics)
2183                 | ItemKind::Enum(_, ref generics)
2184                 | ItemKind::Struct(_, ref generics)
2185                 | ItemKind::Union(_, ref generics) => generics,
2186
2187                 ItemKind::Trait(_, _, ref generics, .., items) => {
2188                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2189                     generics
2190                 }
2191                 ItemKind::TraitAlias(ref generics, _) => {
2192                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
2193                     generics
2194                 }
2195                 ItemKind::OpaqueTy(OpaqueTy {
2196                     ref bounds,
2197                     impl_trait_fn,
2198                     ref generics,
2199                     origin: _,
2200                 }) => {
2201                     let bounds_predicates = ty::print::with_no_queries(|| {
2202                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
2203                         let opaque_ty = tcx.mk_opaque(def_id, substs);
2204
2205                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2206                         let bounds = AstConv::compute_bounds(
2207                             &icx,
2208                             opaque_ty,
2209                             bounds,
2210                             SizedByDefault::Yes,
2211                             tcx.def_span(def_id),
2212                         );
2213
2214                         bounds.predicates(tcx, opaque_ty)
2215                     });
2216                     if impl_trait_fn.is_some() {
2217                         // opaque types
2218                         return ty::GenericPredicates {
2219                             parent: None,
2220                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2221                         };
2222                     } else {
2223                         // named opaque types
2224                         predicates.extend(bounds_predicates);
2225                         generics
2226                     }
2227                 }
2228
2229                 _ => NO_GENERICS,
2230             }
2231         }
2232
2233         Node::ForeignItem(item) => match item.kind {
2234             ForeignItemKind::Static(..) => NO_GENERICS,
2235             ForeignItemKind::Fn(_, _, ref generics) => generics,
2236             ForeignItemKind::Type => NO_GENERICS,
2237         },
2238
2239         _ => NO_GENERICS,
2240     };
2241
2242     let generics = tcx.generics_of(def_id);
2243     let parent_count = generics.parent_count as u32;
2244     let has_own_self = generics.has_self && parent_count == 0;
2245
2246     // Below we'll consider the bounds on the type parameters (including `Self`)
2247     // and the explicit where-clauses, but to get the full set of predicates
2248     // on a trait we need to add in the supertrait bounds and bounds found on
2249     // associated types.
2250     if let Some((_trait_ref, _)) = is_trait {
2251         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2252     }
2253
2254     // In default impls, we can assume that the self type implements
2255     // the trait. So in:
2256     //
2257     //     default impl Foo for Bar { .. }
2258     //
2259     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2260     // (see below). Recall that a default impl is not itself an impl, but rather a
2261     // set of defaults that can be incorporated into another impl.
2262     if let Some(trait_ref) = is_default_impl_trait {
2263         predicates.push((
2264             trait_ref.to_poly_trait_ref().without_const().to_predicate(),
2265             tcx.def_span(def_id),
2266         ));
2267     }
2268
2269     // Collect the region predicates that were declared inline as
2270     // well. In the case of parameters declared on a fn or method, we
2271     // have to be careful to only iterate over early-bound regions.
2272     let mut index = parent_count + has_own_self as u32;
2273     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2274         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2275             def_id: tcx.hir().local_def_id(param.hir_id),
2276             index,
2277             name: param.name.ident().name,
2278         }));
2279         index += 1;
2280
2281         match param.kind {
2282             GenericParamKind::Lifetime { .. } => {
2283                 param.bounds.iter().for_each(|bound| match bound {
2284                     hir::GenericBound::Outlives(lt) => {
2285                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2286                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2287                         predicates.push((outlives.to_predicate(), lt.span));
2288                     }
2289                     _ => bug!(),
2290                 });
2291             }
2292             _ => bug!(),
2293         }
2294     }
2295
2296     // Collect the predicates that were written inline by the user on each
2297     // type parameter (e.g., `<T: Foo>`).
2298     for param in ast_generics.params {
2299         if let GenericParamKind::Type { .. } = param.kind {
2300             let name = param.name.ident().name;
2301             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2302             index += 1;
2303
2304             let sized = SizedByDefault::Yes;
2305             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2306             predicates.extend(bounds.predicates(tcx, param_ty));
2307         }
2308     }
2309
2310     // Add in the bounds that appear in the where-clause.
2311     let where_clause = &ast_generics.where_clause;
2312     for predicate in where_clause.predicates {
2313         match predicate {
2314             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2315                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2316
2317                 // Keep the type around in a dummy predicate, in case of no bounds.
2318                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2319                 // is still checked for WF.
2320                 if bound_pred.bounds.is_empty() {
2321                     if let ty::Param(_) = ty.kind {
2322                         // This is a `where T:`, which can be in the HIR from the
2323                         // transformation that moves `?Sized` to `T`'s declaration.
2324                         // We can skip the predicate because type parameters are
2325                         // trivially WF, but also we *should*, to avoid exposing
2326                         // users who never wrote `where Type:,` themselves, to
2327                         // compiler/tooling bugs from not handling WF predicates.
2328                     } else {
2329                         let span = bound_pred.bounded_ty.span;
2330                         let re_root_empty = tcx.lifetimes.re_root_empty;
2331                         let predicate = ty::OutlivesPredicate(ty, re_root_empty);
2332                         predicates.push((
2333                             ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)),
2334                             span,
2335                         ));
2336                     }
2337                 }
2338
2339                 for bound in bound_pred.bounds.iter() {
2340                     match bound {
2341                         &hir::GenericBound::Trait(ref poly_trait_ref, modifier) => {
2342                             let constness = match modifier {
2343                                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2344                                 hir::TraitBoundModifier::None => constness,
2345                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
2346                             };
2347
2348                             let mut bounds = Bounds::default();
2349                             let _ = AstConv::instantiate_poly_trait_ref(
2350                                 &icx,
2351                                 poly_trait_ref,
2352                                 constness,
2353                                 ty,
2354                                 &mut bounds,
2355                             );
2356                             predicates.extend(bounds.predicates(tcx, ty));
2357                         }
2358
2359                         &hir::GenericBound::Outlives(ref lifetime) => {
2360                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2361                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2362                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2363                         }
2364                     }
2365                 }
2366             }
2367
2368             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2369                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2370                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2371                     let (r2, span) = match bound {
2372                         hir::GenericBound::Outlives(lt) => {
2373                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2374                         }
2375                         _ => bug!(),
2376                     };
2377                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2378
2379                     (ty::Predicate::RegionOutlives(pred), span)
2380                 }))
2381             }
2382
2383             &hir::WherePredicate::EqPredicate(..) => {
2384                 // FIXME(#20041)
2385             }
2386         }
2387     }
2388
2389     // Add predicates from associated type bounds.
2390     if let Some((self_trait_ref, trait_items)) = is_trait {
2391         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2392             associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2393         }))
2394     }
2395
2396     let mut predicates = predicates.predicates;
2397
2398     // Subtle: before we store the predicates into the tcx, we
2399     // sort them so that predicates like `T: Foo<Item=U>` come
2400     // before uses of `U`.  This avoids false ambiguity errors
2401     // in trait checking. See `setup_constraining_predicates`
2402     // for details.
2403     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2404         let self_ty = tcx.type_of(def_id);
2405         let trait_ref = tcx.impl_trait_ref(def_id);
2406         cgp::setup_constraining_predicates(
2407             tcx,
2408             &mut predicates,
2409             trait_ref,
2410             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2411         );
2412     }
2413
2414     let result = ty::GenericPredicates {
2415         parent: generics.parent,
2416         predicates: tcx.arena.alloc_from_iter(predicates),
2417     };
2418     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2419     result
2420 }
2421
2422 fn associated_item_predicates(
2423     tcx: TyCtxt<'tcx>,
2424     def_id: DefId,
2425     self_trait_ref: ty::TraitRef<'tcx>,
2426     trait_item_ref: &hir::TraitItemRef,
2427 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2428     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2429     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2430     let bounds = match trait_item.kind {
2431         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2432         _ => return Vec::new(),
2433     };
2434
2435     let is_gat = !tcx.generics_of(item_def_id).params.is_empty();
2436
2437     let mut had_error = false;
2438
2439     let mut unimplemented_error = |arg_kind: &str| {
2440         if !had_error {
2441             tcx.sess
2442                 .struct_span_err(
2443                     trait_item.span,
2444                     &format!("{}-generic associated types are not yet implemented", arg_kind),
2445                 )
2446                 .note(
2447                     "for more information, see issue #44265 \
2448                      <https://github.com/rust-lang/rust/issues/44265> for more information",
2449                 )
2450                 .emit();
2451             had_error = true;
2452         }
2453     };
2454
2455     let mk_bound_param = |param: &ty::GenericParamDef, _: &_| {
2456         match param.kind {
2457             ty::GenericParamDefKind::Lifetime => tcx
2458                 .mk_region(ty::RegionKind::ReLateBound(
2459                     ty::INNERMOST,
2460                     ty::BoundRegion::BrNamed(param.def_id, param.name),
2461                 ))
2462                 .into(),
2463             // FIXME(generic_associated_types): Use bound types and constants
2464             // once they are handled by the trait system.
2465             ty::GenericParamDefKind::Type { .. } => {
2466                 unimplemented_error("type");
2467                 tcx.types.err.into()
2468             }
2469             ty::GenericParamDefKind::Const => {
2470                 unimplemented_error("const");
2471                 tcx.consts.err.into()
2472             }
2473         }
2474     };
2475
2476     let bound_substs = if is_gat {
2477         // Given:
2478         //
2479         // trait X<'a, B, const C: usize> {
2480         //     type T<'d, E, const F: usize>: Default;
2481         // }
2482         //
2483         // We need to create predicates on the trait:
2484         //
2485         // for<'d, E, const F: usize>
2486         // <Self as X<'a, B, const C: usize>>::T<'d, E, const F: usize>: Sized + Default
2487         //
2488         // We substitute escaping bound parameters for the generic
2489         // arguments to the associated type which are then bound by
2490         // the `Binder` around the the predicate.
2491         //
2492         // FIXME(generic_associated_types): Currently only lifetimes are handled.
2493         self_trait_ref.substs.extend_to(tcx, item_def_id, mk_bound_param)
2494     } else {
2495         self_trait_ref.substs
2496     };
2497
2498     let assoc_ty = tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id), bound_substs);
2499
2500     let bounds = AstConv::compute_bounds(
2501         &ItemCtxt::new(tcx, def_id),
2502         assoc_ty,
2503         bounds,
2504         SizedByDefault::Yes,
2505         trait_item.span,
2506     );
2507
2508     let predicates = bounds.predicates(tcx, assoc_ty);
2509
2510     if is_gat {
2511         // We use shifts to get the regions that we're substituting to
2512         // be bound by the binders in the `Predicate`s rather that
2513         // escaping.
2514         let shifted_in = ty::fold::shift_vars(tcx, &predicates, 1);
2515         let substituted = shifted_in.subst(tcx, bound_substs);
2516         ty::fold::shift_out_vars(tcx, &substituted, 1)
2517     } else {
2518         predicates
2519     }
2520 }
2521
2522 /// Converts a specific `GenericBound` from the AST into a set of
2523 /// predicates that apply to the self type. A vector is returned
2524 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2525 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2526 /// and `<T as Bar>::X == i32`).
2527 fn predicates_from_bound<'tcx>(
2528     astconv: &dyn AstConv<'tcx>,
2529     param_ty: Ty<'tcx>,
2530     bound: &'tcx hir::GenericBound<'tcx>,
2531     constness: ast::Constness,
2532 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2533     match *bound {
2534         hir::GenericBound::Trait(ref tr, modifier) => {
2535             let constness = match modifier {
2536                 hir::TraitBoundModifier::Maybe => return vec![],
2537                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2538                 hir::TraitBoundModifier::None => constness,
2539             };
2540
2541             let mut bounds = Bounds::default();
2542             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2543             bounds.predicates(astconv.tcx(), param_ty)
2544         }
2545         hir::GenericBound::Outlives(ref lifetime) => {
2546             let region = astconv.ast_region_to_region(lifetime, None);
2547             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2548             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2549         }
2550     }
2551 }
2552
2553 fn compute_sig_of_foreign_fn_decl<'tcx>(
2554     tcx: TyCtxt<'tcx>,
2555     def_id: DefId,
2556     decl: &'tcx hir::FnDecl<'tcx>,
2557     abi: abi::Abi,
2558 ) -> ty::PolyFnSig<'tcx> {
2559     let unsafety = if abi == abi::Abi::RustIntrinsic {
2560         intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2561     } else {
2562         hir::Unsafety::Unsafe
2563     };
2564     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
2565
2566     // Feature gate SIMD types in FFI, since I am not sure that the
2567     // ABIs are handled at all correctly. -huonw
2568     if abi != abi::Abi::RustIntrinsic
2569         && abi != abi::Abi::PlatformIntrinsic
2570         && !tcx.features().simd_ffi
2571     {
2572         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2573             if ty.is_simd() {
2574                 tcx.sess
2575                     .struct_span_err(
2576                         ast_ty.span,
2577                         &format!(
2578                             "use of SIMD type `{}` in FFI is highly experimental and \
2579                             may result in invalid code",
2580                             tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2581                         ),
2582                     )
2583                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2584                     .emit();
2585             }
2586         };
2587         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2588             check(&input, ty)
2589         }
2590         if let hir::FunctionRetTy::Return(ref ty) = decl.output {
2591             check(&ty, *fty.output().skip_binder())
2592         }
2593     }
2594
2595     fty
2596 }
2597
2598 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2599     match tcx.hir().get_if_local(def_id) {
2600         Some(Node::ForeignItem(..)) => true,
2601         Some(_) => false,
2602         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2603     }
2604 }
2605
2606 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2607     match tcx.hir().get_if_local(def_id) {
2608         Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. }))
2609         | Some(Node::ForeignItem(&hir::ForeignItem {
2610             kind: hir::ForeignItemKind::Static(_, mutbl),
2611             ..
2612         })) => Some(mutbl),
2613         Some(_) => None,
2614         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2615     }
2616 }
2617
2618 fn from_target_feature(
2619     tcx: TyCtxt<'_>,
2620     id: DefId,
2621     attr: &ast::Attribute,
2622     whitelist: &FxHashMap<String, Option<Symbol>>,
2623     target_features: &mut Vec<Symbol>,
2624 ) {
2625     let list = match attr.meta_item_list() {
2626         Some(list) => list,
2627         None => return,
2628     };
2629     let bad_item = |span| {
2630         let msg = "malformed `target_feature` attribute input";
2631         let code = "enable = \"..\"".to_owned();
2632         tcx.sess
2633             .struct_span_err(span, &msg)
2634             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2635             .emit();
2636     };
2637     let rust_features = tcx.features();
2638     for item in list {
2639         // Only `enable = ...` is accepted in the meta-item list.
2640         if !item.check_name(sym::enable) {
2641             bad_item(item.span());
2642             continue;
2643         }
2644
2645         // Must be of the form `enable = "..."` (a string).
2646         let value = match item.value_str() {
2647             Some(value) => value,
2648             None => {
2649                 bad_item(item.span());
2650                 continue;
2651             }
2652         };
2653
2654         // We allow comma separation to enable multiple features.
2655         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2656             // Only allow whitelisted features per platform.
2657             let feature_gate = match whitelist.get(feature) {
2658                 Some(g) => g,
2659                 None => {
2660                     let msg =
2661                         format!("the feature named `{}` is not valid for this target", feature);
2662                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2663                     err.span_label(
2664                         item.span(),
2665                         format!("`{}` is not valid for this target", feature),
2666                     );
2667                     if feature.starts_with("+") {
2668                         let valid = whitelist.contains_key(&feature[1..]);
2669                         if valid {
2670                             err.help("consider removing the leading `+` in the feature name");
2671                         }
2672                     }
2673                     err.emit();
2674                     return None;
2675                 }
2676             };
2677
2678             // Only allow features whose feature gates have been enabled.
2679             let allowed = match feature_gate.as_ref().map(|s| *s) {
2680                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2681                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2682                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2683                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2684                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2685                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2686                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2687                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2688                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2689                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2690                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2691                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2692                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2693                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2694                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2695                 Some(name) => bug!("unknown target feature gate {}", name),
2696                 None => true,
2697             };
2698             if !allowed && id.is_local() {
2699                 feature_err(
2700                     &tcx.sess.parse_sess,
2701                     feature_gate.unwrap(),
2702                     item.span(),
2703                     &format!("the target feature `{}` is currently unstable", feature),
2704                 )
2705                 .emit();
2706             }
2707             Some(Symbol::intern(feature))
2708         }));
2709     }
2710 }
2711
2712 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2713     use rustc::mir::mono::Linkage::*;
2714
2715     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2716     // applicable to variable declarations and may not really make sense for
2717     // Rust code in the first place but whitelist them anyway and trust that
2718     // the user knows what s/he's doing. Who knows, unanticipated use cases
2719     // may pop up in the future.
2720     //
2721     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2722     // and don't have to be, LLVM treats them as no-ops.
2723     match name {
2724         "appending" => Appending,
2725         "available_externally" => AvailableExternally,
2726         "common" => Common,
2727         "extern_weak" => ExternalWeak,
2728         "external" => External,
2729         "internal" => Internal,
2730         "linkonce" => LinkOnceAny,
2731         "linkonce_odr" => LinkOnceODR,
2732         "private" => Private,
2733         "weak" => WeakAny,
2734         "weak_odr" => WeakODR,
2735         _ => {
2736             let span = tcx.hir().span_if_local(def_id);
2737             if let Some(span) = span {
2738                 tcx.sess.span_fatal(span, "invalid linkage specified")
2739             } else {
2740                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2741             }
2742         }
2743     }
2744 }
2745
2746 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2747     let attrs = tcx.get_attrs(id);
2748
2749     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2750
2751     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2752
2753     let mut inline_span = None;
2754     let mut link_ordinal_span = None;
2755     let mut no_sanitize_span = None;
2756     for attr in attrs.iter() {
2757         if attr.check_name(sym::cold) {
2758             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2759         } else if attr.check_name(sym::rustc_allocator) {
2760             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2761         } else if attr.check_name(sym::unwind) {
2762             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2763         } else if attr.check_name(sym::ffi_returns_twice) {
2764             if tcx.is_foreign_item(id) {
2765                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2766             } else {
2767                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2768                 struct_span_err!(
2769                     tcx.sess,
2770                     attr.span,
2771                     E0724,
2772                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2773                 )
2774                 .emit();
2775             }
2776         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2777             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2778         } else if attr.check_name(sym::naked) {
2779             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2780         } else if attr.check_name(sym::no_mangle) {
2781             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2782         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2783             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2784         } else if attr.check_name(sym::no_debug) {
2785             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2786         } else if attr.check_name(sym::used) {
2787             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2788         } else if attr.check_name(sym::thread_local) {
2789             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2790         } else if attr.check_name(sym::track_caller) {
2791             if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2792                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2793                     .emit();
2794             }
2795             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2796         } else if attr.check_name(sym::export_name) {
2797             if let Some(s) = attr.value_str() {
2798                 if s.as_str().contains("\0") {
2799                     // `#[export_name = ...]` will be converted to a null-terminated string,
2800                     // so it may not contain any null characters.
2801                     struct_span_err!(
2802                         tcx.sess,
2803                         attr.span,
2804                         E0648,
2805                         "`export_name` may not contain null characters"
2806                     )
2807                     .emit();
2808                 }
2809                 codegen_fn_attrs.export_name = Some(s);
2810             }
2811         } else if attr.check_name(sym::target_feature) {
2812             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2813                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2814                 tcx.sess
2815                     .struct_span_err(attr.span, msg)
2816                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2817                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2818                     .emit();
2819             }
2820             from_target_feature(tcx, id, attr, &whitelist, &mut codegen_fn_attrs.target_features);
2821         } else if attr.check_name(sym::linkage) {
2822             if let Some(val) = attr.value_str() {
2823                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2824             }
2825         } else if attr.check_name(sym::link_section) {
2826             if let Some(val) = attr.value_str() {
2827                 if val.as_str().bytes().any(|b| b == 0) {
2828                     let msg = format!(
2829                         "illegal null byte in link_section \
2830                          value: `{}`",
2831                         &val
2832                     );
2833                     tcx.sess.span_err(attr.span, &msg);
2834                 } else {
2835                     codegen_fn_attrs.link_section = Some(val);
2836                 }
2837             }
2838         } else if attr.check_name(sym::link_name) {
2839             codegen_fn_attrs.link_name = attr.value_str();
2840         } else if attr.check_name(sym::link_ordinal) {
2841             link_ordinal_span = Some(attr.span);
2842             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2843                 codegen_fn_attrs.link_ordinal = ordinal;
2844             }
2845         } else if attr.check_name(sym::no_sanitize) {
2846             no_sanitize_span = Some(attr.span);
2847             if let Some(list) = attr.meta_item_list() {
2848                 for item in list.iter() {
2849                     if item.check_name(sym::address) {
2850                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_ADDRESS;
2851                     } else if item.check_name(sym::memory) {
2852                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_MEMORY;
2853                     } else if item.check_name(sym::thread) {
2854                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_THREAD;
2855                     } else {
2856                         tcx.sess
2857                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2858                             .note("expected one of: `address`, `memory` or `thread`")
2859                             .emit();
2860                     }
2861                 }
2862             }
2863         }
2864     }
2865
2866     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2867         if !attr.has_name(sym::inline) {
2868             return ia;
2869         }
2870         match attr.meta().map(|i| i.kind) {
2871             Some(MetaItemKind::Word) => {
2872                 mark_used(attr);
2873                 InlineAttr::Hint
2874             }
2875             Some(MetaItemKind::List(ref items)) => {
2876                 mark_used(attr);
2877                 inline_span = Some(attr.span);
2878                 if items.len() != 1 {
2879                     struct_span_err!(
2880                         tcx.sess.diagnostic(),
2881                         attr.span,
2882                         E0534,
2883                         "expected one argument"
2884                     )
2885                     .emit();
2886                     InlineAttr::None
2887                 } else if list_contains_name(&items[..], sym::always) {
2888                     InlineAttr::Always
2889                 } else if list_contains_name(&items[..], sym::never) {
2890                     InlineAttr::Never
2891                 } else {
2892                     struct_span_err!(
2893                         tcx.sess.diagnostic(),
2894                         items[0].span(),
2895                         E0535,
2896                         "invalid argument"
2897                     )
2898                     .emit();
2899
2900                     InlineAttr::None
2901                 }
2902             }
2903             Some(MetaItemKind::NameValue(_)) => ia,
2904             None => ia,
2905         }
2906     });
2907
2908     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2909         if !attr.has_name(sym::optimize) {
2910             return ia;
2911         }
2912         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2913         match attr.meta().map(|i| i.kind) {
2914             Some(MetaItemKind::Word) => {
2915                 err(attr.span, "expected one argument");
2916                 ia
2917             }
2918             Some(MetaItemKind::List(ref items)) => {
2919                 mark_used(attr);
2920                 inline_span = Some(attr.span);
2921                 if items.len() != 1 {
2922                     err(attr.span, "expected one argument");
2923                     OptimizeAttr::None
2924                 } else if list_contains_name(&items[..], sym::size) {
2925                     OptimizeAttr::Size
2926                 } else if list_contains_name(&items[..], sym::speed) {
2927                     OptimizeAttr::Speed
2928                 } else {
2929                     err(items[0].span(), "invalid argument");
2930                     OptimizeAttr::None
2931                 }
2932             }
2933             Some(MetaItemKind::NameValue(_)) => ia,
2934             None => ia,
2935         }
2936     });
2937
2938     // If a function uses #[target_feature] it can't be inlined into general
2939     // purpose functions as they wouldn't have the right target features
2940     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2941     // respected.
2942     if codegen_fn_attrs.target_features.len() > 0 {
2943         if codegen_fn_attrs.inline == InlineAttr::Always {
2944             if let Some(span) = inline_span {
2945                 tcx.sess.span_err(
2946                     span,
2947                     "cannot use `#[inline(always)]` with \
2948                      `#[target_feature]`",
2949                 );
2950             }
2951         }
2952     }
2953
2954     if codegen_fn_attrs.flags.intersects(CodegenFnAttrFlags::NO_SANITIZE_ANY) {
2955         if codegen_fn_attrs.inline == InlineAttr::Always {
2956             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2957                 let hir_id = tcx.hir().as_local_hir_id(id).unwrap();
2958                 tcx.struct_span_lint_hir(
2959                     lint::builtin::INLINE_NO_SANITIZE,
2960                     hir_id,
2961                     no_sanitize_span,
2962                     |lint| {
2963                         lint.build("`no_sanitize` will have no effect after inlining")
2964                             .span_note(inline_span, "inlining requested here")
2965                             .emit();
2966                     },
2967                 )
2968             }
2969         }
2970     }
2971
2972     // Weak lang items have the same semantics as "std internal" symbols in the
2973     // sense that they're preserved through all our LTO passes and only
2974     // strippable by the linker.
2975     //
2976     // Additionally weak lang items have predetermined symbol names.
2977     if tcx.is_weak_lang_item(id) {
2978         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2979     }
2980     if let Some(name) = lang_items::link_name(&attrs) {
2981         codegen_fn_attrs.export_name = Some(name);
2982         codegen_fn_attrs.link_name = Some(name);
2983     }
2984     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2985
2986     // Internal symbols to the standard library all have no_mangle semantics in
2987     // that they have defined symbol names present in the function name. This
2988     // also applies to weak symbols where they all have known symbol names.
2989     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2990         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2991     }
2992
2993     codegen_fn_attrs
2994 }
2995
2996 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2997     use syntax::ast::{Lit, LitIntType, LitKind};
2998     let meta_item_list = attr.meta_item_list();
2999     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3000     let sole_meta_list = match meta_item_list {
3001         Some([item]) => item.literal(),
3002         _ => None,
3003     };
3004     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3005         if *ordinal <= std::usize::MAX as u128 {
3006             Some(*ordinal as usize)
3007         } else {
3008             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3009             tcx.sess
3010                 .struct_span_err(attr.span, &msg)
3011                 .note("the value may not exceed `std::usize::MAX`")
3012                 .emit();
3013             None
3014         }
3015     } else {
3016         tcx.sess
3017             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3018             .note("an unsuffixed integer value, e.g., `1`, is expected")
3019             .emit();
3020         None
3021     }
3022 }
3023
3024 fn check_link_name_xor_ordinal(
3025     tcx: TyCtxt<'_>,
3026     codegen_fn_attrs: &CodegenFnAttrs,
3027     inline_span: Option<Span>,
3028 ) {
3029     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3030         return;
3031     }
3032     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3033     if let Some(span) = inline_span {
3034         tcx.sess.span_err(span, msg);
3035     } else {
3036         tcx.sess.err(msg);
3037     }
3038 }