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::resolve_lifetime as rl;
  24 use crate::middle::weak_lang_items;
  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     pub fn hir_id(&self) -> hir::HirId {
 283         self.tcx
 284             .hir()
 285             .as_local_hir_id(self.item_def_id)
 286             .expect("Non-local call to local provider is_const_fn")
 287     }
 288
 289     pub fn node(&self) -> hir::Node<'tcx> {
 290         self.tcx.hir().get(self.hir_id())
 291     }
 292 }
 293
 294 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 295     fn tcx(&self) -> TyCtxt<'tcx> {
 296         self.tcx
 297     }
 298
 299     fn item_def_id(&self) -> Option<DefId> {
 300         Some(self.item_def_id)
 301     }
 302
 303     fn default_constness_for_trait_bounds(&self) -> ast::Constness {
 304         if let Some(fn_like) = FnLikeNode::from_node(self.node()) {
 305             fn_like.constness()
 306         } else {
 307             ast::Constness::NotConst
 308         }
 309     }
 310
 311     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 312         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id))
 313     }
 314
 315     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 316         None
 317     }
 318
 319     fn allow_ty_infer(&self) -> bool {
 320         false
 321     }
 322
 323     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 324         self.tcx().sess.delay_span_bug(span, "bad placeholder type");
 325         self.tcx().types.err
 326     }
 327
 328     fn ct_infer(
 329         &self,
 330         _: Ty<'tcx>,
 331         _: Option<&ty::GenericParamDef>,
 332         span: Span,
 333     ) -> &'tcx Const<'tcx> {
 334         bad_placeholder_type(self.tcx(), vec![span]).emit();
 335
 336         self.tcx().consts.err
 337     }
 338
 339     fn projected_ty_from_poly_trait_ref(
 340         &self,
 341         span: Span,
 342         item_def_id: DefId,
 343         item_segment: &hir::PathSegment<'_>,
 344         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 345     ) -> Ty<'tcx> {
 346         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 347             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 348                 self,
 349                 self.tcx,
 350                 span,
 351                 item_def_id,
 352                 item_segment,
 353                 trait_ref.substs,
 354             );
 355             self.tcx().mk_projection(item_def_id, item_substs)
 356         } else {
 357             // There are no late-bound regions; we can just ignore the binder.
 358             let mut err = struct_span_err!(
 359                 self.tcx().sess,
 360                 span,
 361                 E0212,
 362                 "cannot extract an associated type from a higher-ranked trait bound \
 363                  in this context"
 364             );
 365
 366             match self.node() {
 367                 hir::Node::Field(_)
 368                 | hir::Node::Variant(_)
 369                 | hir::Node::Ctor(_)
 370                 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..), .. })
 371                 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(..), .. })
 372                 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(..), .. }) => {
 373                     // The suggestion is only valid if this is not an ADT.
 374                 }
 375                 hir::Node::Item(_)
 376                 | hir::Node::ForeignItem(_)
 377                 | hir::Node::TraitItem(_)
 378                 | hir::Node::ImplItem(_) => {
 379                     err.span_suggestion(
 380                         span,
 381                         "use a fully qualified path with inferred lifetimes",
 382                         format!(
 383                             "{}::{}",
 384                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 385                             self.tcx.anonymize_late_bound_regions(&poly_trait_ref).skip_binder(),
 386                             item_segment.ident
 387                         ),
 388                         Applicability::MaybeIncorrect,
 389                     );
 390                 }
 391                 _ => {}
 392             }
 393             err.emit();
 394             self.tcx().types.err
 395         }
 396     }
 397
 398     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 399         // Types in item signatures are not normalized to avoid undue dependencies.
 400         ty
 401     }
 402
 403     fn set_tainted_by_errors(&self) {
 404         // There's no obvious place to track this, so just let it go.
 405     }
 406
 407     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 408         // There's no place to record types from signatures?
 409     }
 410 }
 411
 412 /// Returns the predicates defined on `item_def_id` of the form
 413 /// `X: Foo` where `X` is the type parameter `def_id`.
 414 fn type_param_predicates(
 415     tcx: TyCtxt<'_>,
 416     (item_def_id, def_id): (DefId, DefId),
 417 ) -> ty::GenericPredicates<'_> {
 418     use rustc_hir::*;
 419
 420     // In the AST, bounds can derive from two places. Either
 421     // written inline like `<T: Foo>` or in a where-clause like
 422     // `where T: Foo`.
 423
 424     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 425     let param_owner = tcx.hir().ty_param_owner(param_id);
 426     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 427     let generics = tcx.generics_of(param_owner_def_id);
 428     let index = generics.param_def_id_to_index[&def_id];
 429     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 430
 431     // Don't look for bounds where the type parameter isn't in scope.
 432     let parent =
 433         if item_def_id == param_owner_def_id { None } else { tcx.generics_of(item_def_id).parent };
 434
 435     let mut result = parent
 436         .map(|parent| {
 437             let icx = ItemCtxt::new(tcx, parent);
 438             icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 439         })
 440         .unwrap_or_default();
 441     let mut extend = None;
 442
 443     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 444     let ast_generics = match tcx.hir().get(item_hir_id) {
 445         Node::TraitItem(item) => &item.generics,
 446
 447         Node::ImplItem(item) => &item.generics,
 448
 449         Node::Item(item) => {
 450             match item.kind {
 451                 ItemKind::Fn(.., ref generics, _)
 452                 | ItemKind::Impl { ref generics, .. }
 453                 | ItemKind::TyAlias(_, ref generics)
 454                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 455                 | ItemKind::Enum(_, ref generics)
 456                 | ItemKind::Struct(_, ref generics)
 457                 | ItemKind::Union(_, ref generics) => generics,
 458                 ItemKind::Trait(_, _, ref generics, ..) => {
 459                     // Implied `Self: Trait` and supertrait bounds.
 460                     if param_id == item_hir_id {
 461                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 462                         extend =
 463                             Some((identity_trait_ref.without_const().to_predicate(), item.span));
 464                     }
 465                     generics
 466                 }
 467                 _ => return result,
 468             }
 469         }
 470
 471         Node::ForeignItem(item) => match item.kind {
 472             ForeignItemKind::Fn(_, _, ref generics) => generics,
 473             _ => return result,
 474         },
 475
 476         _ => return result,
 477     };
 478
 479     let icx = ItemCtxt::new(tcx, item_def_id);
 480     let extra_predicates = extend.into_iter().chain(
 481         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 482             .into_iter()
 483             .filter(|(predicate, _)| match predicate {
 484                 ty::Predicate::Trait(ref data, _) => data.skip_binder().self_ty().is_param(index),
 485                 _ => false,
 486             }),
 487     );
 488     result.predicates =
 489         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 490     result
 491 }
 492
 493 impl ItemCtxt<'tcx> {
 494     /// Finds bounds from `hir::Generics`. This requires scanning through the
 495     /// AST. We do this to avoid having to convert *all* the bounds, which
 496     /// would create artificial cycles. Instead, we can only convert the
 497     /// bounds for a type parameter `X` if `X::Foo` is used.
 498     fn type_parameter_bounds_in_generics(
 499         &self,
 500         ast_generics: &'tcx hir::Generics<'tcx>,
 501         param_id: hir::HirId,
 502         ty: Ty<'tcx>,
 503         only_self_bounds: OnlySelfBounds,
 504     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 505         let constness = self.default_constness_for_trait_bounds();
 506         let from_ty_params = ast_generics
 507             .params
 508             .iter()
 509             .filter_map(|param| match param.kind {
 510                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 511                 _ => None,
 512             })
 513             .flat_map(|bounds| bounds.iter())
 514             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 515
 516         let from_where_clauses = ast_generics
 517             .where_clause
 518             .predicates
 519             .iter()
 520             .filter_map(|wp| match *wp {
 521                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 522                 _ => None,
 523             })
 524             .flat_map(|bp| {
 525                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 526                     Some(ty)
 527                 } else if !only_self_bounds.0 {
 528                     Some(self.to_ty(&bp.bounded_ty))
 529                 } else {
 530                     None
 531                 };
 532                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 533             })
 534             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 535
 536         from_ty_params.chain(from_where_clauses).collect()
 537     }
 538 }
 539
 540 /// Tests whether this is the AST for a reference to the type
 541 /// parameter with ID `param_id`. We use this so as to avoid running
 542 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 543 /// conversion of the type to avoid inducing unnecessary cycles.
 544 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 545     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 546         match path.res {
 547             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 548                 def_id == tcx.hir().local_def_id(param_id)
 549             }
 550             _ => false,
 551         }
 552     } else {
 553         false
 554     }
 555 }
 556
 557 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 558     let it = tcx.hir().expect_item(item_id);
 559     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 560     let def_id = tcx.hir().local_def_id(item_id);
 561     match it.kind {
 562         // These don't define types.
 563         hir::ItemKind::ExternCrate(_)
 564         | hir::ItemKind::Use(..)
 565         | hir::ItemKind::Mod(_)
 566         | hir::ItemKind::GlobalAsm(_) => {}
 567         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 568             for item in foreign_mod.items {
 569                 let def_id = tcx.hir().local_def_id(item.hir_id);
 570                 tcx.generics_of(def_id);
 571                 tcx.type_of(def_id);
 572                 tcx.predicates_of(def_id);
 573                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 574                     tcx.fn_sig(def_id);
 575                 }
 576             }
 577         }
 578         hir::ItemKind::Enum(ref enum_definition, _) => {
 579             tcx.generics_of(def_id);
 580             tcx.type_of(def_id);
 581             tcx.predicates_of(def_id);
 582             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 583         }
 584         hir::ItemKind::Impl { .. } => {
 585             tcx.generics_of(def_id);
 586             tcx.type_of(def_id);
 587             tcx.impl_trait_ref(def_id);
 588             tcx.predicates_of(def_id);
 589         }
 590         hir::ItemKind::Trait(..) => {
 591             tcx.generics_of(def_id);
 592             tcx.trait_def(def_id);
 593             tcx.at(it.span).super_predicates_of(def_id);
 594             tcx.predicates_of(def_id);
 595         }
 596         hir::ItemKind::TraitAlias(..) => {
 597             tcx.generics_of(def_id);
 598             tcx.at(it.span).super_predicates_of(def_id);
 599             tcx.predicates_of(def_id);
 600         }
 601         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 602             tcx.generics_of(def_id);
 603             tcx.type_of(def_id);
 604             tcx.predicates_of(def_id);
 605
 606             for f in struct_def.fields() {
 607                 let def_id = tcx.hir().local_def_id(f.hir_id);
 608                 tcx.generics_of(def_id);
 609                 tcx.type_of(def_id);
 610                 tcx.predicates_of(def_id);
 611             }
 612
 613             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 614                 convert_variant_ctor(tcx, ctor_hir_id);
 615             }
 616         }
 617
 618         // Desugared from `impl Trait`, so visited by the function's return type.
 619         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 620
 621         hir::ItemKind::OpaqueTy(..)
 622         | hir::ItemKind::TyAlias(..)
 623         | hir::ItemKind::Static(..)
 624         | hir::ItemKind::Const(..)
 625         | hir::ItemKind::Fn(..) => {
 626             tcx.generics_of(def_id);
 627             tcx.type_of(def_id);
 628             tcx.predicates_of(def_id);
 629             if let hir::ItemKind::Fn(..) = it.kind {
 630                 tcx.fn_sig(def_id);
 631             }
 632         }
 633     }
 634 }
 635
 636 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 637     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 638     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 639     tcx.generics_of(def_id);
 640
 641     match trait_item.kind {
 642         hir::TraitItemKind::Const(..)
 643         | hir::TraitItemKind::Type(_, Some(_))
 644         | hir::TraitItemKind::Method(..) => {
 645             tcx.type_of(def_id);
 646             if let hir::TraitItemKind::Method(..) = trait_item.kind {
 647                 tcx.fn_sig(def_id);
 648             }
 649         }
 650
 651         hir::TraitItemKind::Type(_, None) => {}
 652     };
 653
 654     tcx.predicates_of(def_id);
 655 }
 656
 657 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 658     let def_id = tcx.hir().local_def_id(impl_item_id);
 659     tcx.generics_of(def_id);
 660     tcx.type_of(def_id);
 661     tcx.predicates_of(def_id);
 662     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
 663         tcx.fn_sig(def_id);
 664     }
 665 }
 666
 667 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 668     let def_id = tcx.hir().local_def_id(ctor_id);
 669     tcx.generics_of(def_id);
 670     tcx.type_of(def_id);
 671     tcx.predicates_of(def_id);
 672 }
 673
 674 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 675     let def = tcx.adt_def(def_id);
 676     let repr_type = def.repr.discr_type();
 677     let initial = repr_type.initial_discriminant(tcx);
 678     let mut prev_discr = None::<Discr<'_>>;
 679
 680     // fill the discriminant values and field types
 681     for variant in variants {
 682         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 683         prev_discr = Some(
 684             if let Some(ref e) = variant.disr_expr {
 685                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 686                 def.eval_explicit_discr(tcx, expr_did)
 687             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 688                 Some(discr)
 689             } else {
 690                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 691                     .span_label(
 692                         variant.span,
 693                         format!("overflowed on value after {}", prev_discr.unwrap()),
 694                     )
 695                     .note(&format!(
 696                         "explicitly set `{} = {}` if that is desired outcome",
 697                         variant.ident, wrapped_discr
 698                     ))
 699                     .emit();
 700                 None
 701             }
 702             .unwrap_or(wrapped_discr),
 703         );
 704
 705         for f in variant.data.fields() {
 706             let def_id = tcx.hir().local_def_id(f.hir_id);
 707             tcx.generics_of(def_id);
 708             tcx.type_of(def_id);
 709             tcx.predicates_of(def_id);
 710         }
 711
 712         // Convert the ctor, if any. This also registers the variant as
 713         // an item.
 714         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 715             convert_variant_ctor(tcx, ctor_hir_id);
 716         }
 717     }
 718 }
 719
 720 fn convert_variant(
 721     tcx: TyCtxt<'_>,
 722     variant_did: Option<DefId>,
 723     ctor_did: Option<DefId>,
 724     ident: Ident,
 725     discr: ty::VariantDiscr,
 726     def: &hir::VariantData<'_>,
 727     adt_kind: ty::AdtKind,
 728     parent_did: DefId,
 729 ) -> ty::VariantDef {
 730     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 731     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 732     let fields = def
 733         .fields()
 734         .iter()
 735         .map(|f| {
 736             let fid = tcx.hir().local_def_id(f.hir_id);
 737             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 738             if let Some(prev_span) = dup_span {
 739                 struct_span_err!(
 740                     tcx.sess,
 741                     f.span,
 742                     E0124,
 743                     "field `{}` is already declared",
 744                     f.ident
 745                 )
 746                 .span_label(f.span, "field already declared")
 747                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 748                 .emit();
 749             } else {
 750                 seen_fields.insert(f.ident.modern(), f.span);
 751             }
 752
 753             ty::FieldDef {
 754                 did: fid,
 755                 ident: f.ident,
 756                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 757             }
 758         })
 759         .collect();
 760     let recovered = match def {
 761         hir::VariantData::Struct(_, r) => *r,
 762         _ => false,
 763     };
 764     ty::VariantDef::new(
 765         tcx,
 766         ident,
 767         variant_did,
 768         ctor_did,
 769         discr,
 770         fields,
 771         CtorKind::from_hir(def),
 772         adt_kind,
 773         parent_did,
 774         recovered,
 775     )
 776 }
 777
 778 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 779     use rustc_hir::*;
 780
 781     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 782     let item = match tcx.hir().get(hir_id) {
 783         Node::Item(item) => item,
 784         _ => bug!(),
 785     };
 786
 787     let repr = ReprOptions::new(tcx, def_id);
 788     let (kind, variants) = match item.kind {
 789         ItemKind::Enum(ref def, _) => {
 790             let mut distance_from_explicit = 0;
 791             let variants = def
 792                 .variants
 793                 .iter()
 794                 .map(|v| {
 795                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 796                     let ctor_did =
 797                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 798
 799                     let discr = if let Some(ref e) = v.disr_expr {
 800                         distance_from_explicit = 0;
 801                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 802                     } else {
 803                         ty::VariantDiscr::Relative(distance_from_explicit)
 804                     };
 805                     distance_from_explicit += 1;
 806
 807                     convert_variant(
 808                         tcx,
 809                         variant_did,
 810                         ctor_did,
 811                         v.ident,
 812                         discr,
 813                         &v.data,
 814                         AdtKind::Enum,
 815                         def_id,
 816                     )
 817                 })
 818                 .collect();
 819
 820             (AdtKind::Enum, variants)
 821         }
 822         ItemKind::Struct(ref def, _) => {
 823             let variant_did = None;
 824             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 825
 826             let variants = std::iter::once(convert_variant(
 827                 tcx,
 828                 variant_did,
 829                 ctor_did,
 830                 item.ident,
 831                 ty::VariantDiscr::Relative(0),
 832                 def,
 833                 AdtKind::Struct,
 834                 def_id,
 835             ))
 836             .collect();
 837
 838             (AdtKind::Struct, variants)
 839         }
 840         ItemKind::Union(ref def, _) => {
 841             let variant_did = None;
 842             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 843
 844             let variants = std::iter::once(convert_variant(
 845                 tcx,
 846                 variant_did,
 847                 ctor_did,
 848                 item.ident,
 849                 ty::VariantDiscr::Relative(0),
 850                 def,
 851                 AdtKind::Union,
 852                 def_id,
 853             ))
 854             .collect();
 855
 856             (AdtKind::Union, variants)
 857         }
 858         _ => bug!(),
 859     };
 860     tcx.alloc_adt_def(def_id, kind, variants, repr)
 861 }
 862
 863 /// Ensures that the super-predicates of the trait with a `DefId`
 864 /// of `trait_def_id` are converted and stored. This also ensures that
 865 /// the transitive super-predicates are converted.
 866 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 867     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 868     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 869
 870     let item = match tcx.hir().get(trait_hir_id) {
 871         Node::Item(item) => item,
 872         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 873     };
 874
 875     let (generics, bounds) = match item.kind {
 876         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 877         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 878         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 879     };
 880
 881     let icx = ItemCtxt::new(tcx, trait_def_id);
 882
 883     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 884     let self_param_ty = tcx.types.self_param;
 885     let superbounds1 =
 886         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 887
 888     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 889
 890     // Convert any explicit superbounds in the where-clause,
 891     // e.g., `trait Foo where Self: Bar`.
 892     // In the case of trait aliases, however, we include all bounds in the where-clause,
 893     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 894     // as one of its "superpredicates".
 895     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 896     let superbounds2 = icx.type_parameter_bounds_in_generics(
 897         generics,
 898         item.hir_id,
 899         self_param_ty,
 900         OnlySelfBounds(!is_trait_alias),
 901     );
 902
 903     // Combine the two lists to form the complete set of superbounds:
 904     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
 905
 906     // Now require that immediate supertraits are converted,
 907     // which will, in turn, reach indirect supertraits.
 908     for &(pred, span) in superbounds {
 909         debug!("superbound: {:?}", pred);
 910         if let ty::Predicate::Trait(bound, _) = pred {
 911             tcx.at(span).super_predicates_of(bound.def_id());
 912         }
 913     }
 914
 915     ty::GenericPredicates { parent: None, predicates: superbounds }
 916 }
 917
 918 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 919     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 920     let item = tcx.hir().expect_item(hir_id);
 921
 922     let (is_auto, unsafety) = match item.kind {
 923         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 924         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 925         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 926     };
 927
 928     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 929     if paren_sugar && !tcx.features().unboxed_closures {
 930         tcx.sess
 931             .struct_span_err(
 932                 item.span,
 933                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 934              which traits can use parenthetical notation",
 935             )
 936             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
 937             .emit();
 938     }
 939
 940     let is_marker = tcx.has_attr(def_id, sym::marker);
 941     let def_path_hash = tcx.def_path_hash(def_id);
 942     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 943     tcx.arena.alloc(def)
 944 }
 945
 946 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 947     struct LateBoundRegionsDetector<'tcx> {
 948         tcx: TyCtxt<'tcx>,
 949         outer_index: ty::DebruijnIndex,
 950         has_late_bound_regions: Option<Span>,
 951     }
 952
 953     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 954         type Map = Map<'tcx>;
 955
 956         fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 957             NestedVisitorMap::None
 958         }
 959
 960         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
 961             if self.has_late_bound_regions.is_some() {
 962                 return;
 963             }
 964             match ty.kind {
 965                 hir::TyKind::BareFn(..) => {
 966                     self.outer_index.shift_in(1);
 967                     intravisit::walk_ty(self, ty);
 968                     self.outer_index.shift_out(1);
 969                 }
 970                 _ => intravisit::walk_ty(self, ty),
 971             }
 972         }
 973
 974         fn visit_poly_trait_ref(
 975             &mut self,
 976             tr: &'tcx hir::PolyTraitRef<'tcx>,
 977             m: hir::TraitBoundModifier,
 978         ) {
 979             if self.has_late_bound_regions.is_some() {
 980                 return;
 981             }
 982             self.outer_index.shift_in(1);
 983             intravisit::walk_poly_trait_ref(self, tr, m);
 984             self.outer_index.shift_out(1);
 985         }
 986
 987         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 988             if self.has_late_bound_regions.is_some() {
 989                 return;
 990             }
 991
 992             match self.tcx.named_region(lt.hir_id) {
 993                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 994                 Some(rl::Region::LateBound(debruijn, _, _))
 995                 | Some(rl::Region::LateBoundAnon(debruijn, _))
 996                     if debruijn < self.outer_index => {}
 997                 Some(rl::Region::LateBound(..))
 998                 | Some(rl::Region::LateBoundAnon(..))
 999                 | Some(rl::Region::Free(..))
1000                 | None => {
1001                     self.has_late_bound_regions = Some(lt.span);
1002                 }
1003             }
1004         }
1005     }
1006
1007     fn has_late_bound_regions<'tcx>(
1008         tcx: TyCtxt<'tcx>,
1009         generics: &'tcx hir::Generics<'tcx>,
1010         decl: &'tcx hir::FnDecl<'tcx>,
1011     ) -> Option<Span> {
1012         let mut visitor = LateBoundRegionsDetector {
1013             tcx,
1014             outer_index: ty::INNERMOST,
1015             has_late_bound_regions: None,
1016         };
1017         for param in generics.params {
1018             if let GenericParamKind::Lifetime { .. } = param.kind {
1019                 if tcx.is_late_bound(param.hir_id) {
1020                     return Some(param.span);
1021                 }
1022             }
1023         }
1024         visitor.visit_fn_decl(decl);
1025         visitor.has_late_bound_regions
1026     }
1027
1028     match node {
1029         Node::TraitItem(item) => match item.kind {
1030             hir::TraitItemKind::Method(ref sig, _) => {
1031                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1032             }
1033             _ => None,
1034         },
1035         Node::ImplItem(item) => match item.kind {
1036             hir::ImplItemKind::Method(ref sig, _) => {
1037                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1038             }
1039             _ => None,
1040         },
1041         Node::ForeignItem(item) => match item.kind {
1042             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1043                 has_late_bound_regions(tcx, generics, fn_decl)
1044             }
1045             _ => None,
1046         },
1047         Node::Item(item) => match item.kind {
1048             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1049                 has_late_bound_regions(tcx, generics, &sig.decl)
1050             }
1051             _ => None,
1052         },
1053         _ => None,
1054     }
1055 }
1056
1057 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
1058     use rustc_hir::*;
1059
1060     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1061
1062     let node = tcx.hir().get(hir_id);
1063     let parent_def_id = match node {
1064         Node::ImplItem(_)
1065         | Node::TraitItem(_)
1066         | Node::Variant(_)
1067         | Node::Ctor(..)
1068         | Node::Field(_) => {
1069             let parent_id = tcx.hir().get_parent_item(hir_id);
1070             Some(tcx.hir().local_def_id(parent_id))
1071         }
1072         // FIXME(#43408) enable this always when we get lazy normalization.
1073         Node::AnonConst(_) => {
1074             // HACK(eddyb) this provides the correct generics when
1075             // `feature(const_generics)` is enabled, so that const expressions
1076             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1077             if tcx.features().const_generics {
1078                 let parent_id = tcx.hir().get_parent_item(hir_id);
1079                 Some(tcx.hir().local_def_id(parent_id))
1080             } else {
1081                 None
1082             }
1083         }
1084         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1085             Some(tcx.closure_base_def_id(def_id))
1086         }
1087         Node::Item(item) => match item.kind {
1088             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
1089             _ => None,
1090         },
1091         _ => None,
1092     };
1093
1094     let mut opt_self = None;
1095     let mut allow_defaults = false;
1096
1097     let no_generics = hir::Generics::empty();
1098     let ast_generics = match node {
1099         Node::TraitItem(item) => &item.generics,
1100
1101         Node::ImplItem(item) => &item.generics,
1102
1103         Node::Item(item) => {
1104             match item.kind {
1105                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl { ref generics, .. } => generics,
1106
1107                 ItemKind::TyAlias(_, ref generics)
1108                 | ItemKind::Enum(_, ref generics)
1109                 | ItemKind::Struct(_, ref generics)
1110                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1111                 | ItemKind::Union(_, ref generics) => {
1112                     allow_defaults = true;
1113                     generics
1114                 }
1115
1116                 ItemKind::Trait(_, _, ref generics, ..)
1117                 | ItemKind::TraitAlias(ref generics, ..) => {
1118                     // Add in the self type parameter.
1119                     //
1120                     // Something of a hack: use the node id for the trait, also as
1121                     // the node id for the Self type parameter.
1122                     let param_id = item.hir_id;
1123
1124                     opt_self = Some(ty::GenericParamDef {
1125                         index: 0,
1126                         name: kw::SelfUpper,
1127                         def_id: tcx.hir().local_def_id(param_id),
1128                         pure_wrt_drop: false,
1129                         kind: ty::GenericParamDefKind::Type {
1130                             has_default: false,
1131                             object_lifetime_default: rl::Set1::Empty,
1132                             synthetic: None,
1133                         },
1134                     });
1135
1136                     allow_defaults = true;
1137                     generics
1138                 }
1139
1140                 _ => &no_generics,
1141             }
1142         }
1143
1144         Node::ForeignItem(item) => match item.kind {
1145             ForeignItemKind::Static(..) => &no_generics,
1146             ForeignItemKind::Fn(_, _, ref generics) => generics,
1147             ForeignItemKind::Type => &no_generics,
1148         },
1149
1150         _ => &no_generics,
1151     };
1152
1153     let has_self = opt_self.is_some();
1154     let mut parent_has_self = false;
1155     let mut own_start = has_self as u32;
1156     let parent_count = parent_def_id.map_or(0, |def_id| {
1157         let generics = tcx.generics_of(def_id);
1158         assert_eq!(has_self, false);
1159         parent_has_self = generics.has_self;
1160         own_start = generics.count() as u32;
1161         generics.parent_count + generics.params.len()
1162     });
1163
1164     let mut params: Vec<_> = opt_self.into_iter().collect();
1165
1166     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1167     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1168         name: param.name.ident().name,
1169         index: own_start + i as u32,
1170         def_id: tcx.hir().local_def_id(param.hir_id),
1171         pure_wrt_drop: param.pure_wrt_drop,
1172         kind: ty::GenericParamDefKind::Lifetime,
1173     }));
1174
1175     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1176
1177     // Now create the real type parameters.
1178     let type_start = own_start - has_self as u32 + params.len() as u32;
1179     let mut i = 0;
1180     params.extend(ast_generics.params.iter().filter_map(|param| {
1181         let kind = match param.kind {
1182             GenericParamKind::Type { ref default, synthetic, .. } => {
1183                 if !allow_defaults && default.is_some() {
1184                     if !tcx.features().default_type_parameter_fallback {
1185                         tcx.lint_hir(
1186                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1187                             param.hir_id,
1188                             param.span,
1189                             &format!(
1190                                 "defaults for type parameters are only allowed in \
1191                                         `struct`, `enum`, `type`, or `trait` definitions."
1192                             ),
1193                         );
1194                     }
1195                 }
1196
1197                 ty::GenericParamDefKind::Type {
1198                     has_default: default.is_some(),
1199                     object_lifetime_default: object_lifetime_defaults
1200                         .as_ref()
1201                         .map_or(rl::Set1::Empty, |o| o[i]),
1202                     synthetic,
1203                 }
1204             }
1205             GenericParamKind::Const { .. } => ty::GenericParamDefKind::Const,
1206             _ => return None,
1207         };
1208
1209         let param_def = ty::GenericParamDef {
1210             index: type_start + i as u32,
1211             name: param.name.ident().name,
1212             def_id: tcx.hir().local_def_id(param.hir_id),
1213             pure_wrt_drop: param.pure_wrt_drop,
1214             kind,
1215         };
1216         i += 1;
1217         Some(param_def)
1218     }));
1219
1220     // provide junk type parameter defs - the only place that
1221     // cares about anything but the length is instantiation,
1222     // and we don't do that for closures.
1223     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1224         let dummy_args = if gen.is_some() {
1225             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>"][..]
1226         } else {
1227             &["<closure_kind>", "<closure_signature>"][..]
1228         };
1229
1230         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1231             index: type_start + i as u32,
1232             name: Symbol::intern(arg),
1233             def_id,
1234             pure_wrt_drop: false,
1235             kind: ty::GenericParamDefKind::Type {
1236                 has_default: false,
1237                 object_lifetime_default: rl::Set1::Empty,
1238                 synthetic: None,
1239             },
1240         }));
1241
1242         if let Some(upvars) = tcx.upvars(def_id) {
1243             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1244                 ty::GenericParamDef {
1245                     index: type_start + i,
1246                     name: Symbol::intern("<upvar>"),
1247                     def_id,
1248                     pure_wrt_drop: false,
1249                     kind: ty::GenericParamDefKind::Type {
1250                         has_default: false,
1251                         object_lifetime_default: rl::Set1::Empty,
1252                         synthetic: None,
1253                     },
1254                 }
1255             }));
1256         }
1257     }
1258
1259     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1260
1261     tcx.arena.alloc(ty::Generics {
1262         parent: parent_def_id,
1263         parent_count,
1264         params,
1265         param_def_id_to_index,
1266         has_self: has_self || parent_has_self,
1267         has_late_bound_regions: has_late_bound_regions(tcx, node),
1268     })
1269 }
1270
1271 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1272     struct_span_err!(
1273         tcx.sess,
1274         span,
1275         E0202,
1276         "associated types are not yet supported in inherent impls (see #8995)"
1277     )
1278     .emit();
1279 }
1280
1281 fn infer_placeholder_type(
1282     tcx: TyCtxt<'_>,
1283     def_id: DefId,
1284     body_id: hir::BodyId,
1285     span: Span,
1286     item_ident: Ident,
1287 ) -> Ty<'_> {
1288     let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
1289
1290     // If this came from a free `const` or `static mut?` item,
1291     // then the user may have written e.g. `const A = 42;`.
1292     // In this case, the parser has stashed a diagnostic for
1293     // us to improve in typeck so we do that now.
1294     match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1295         Some(mut err) => {
1296             // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1297             // We are typeck and have the real type, so remove that and suggest the actual type.
1298             err.suggestions.clear();
1299             err.span_suggestion(
1300                 span,
1301                 "provide a type for the item",
1302                 format!("{}: {}", item_ident, ty),
1303                 Applicability::MachineApplicable,
1304             )
1305             .emit();
1306         }
1307         None => {
1308             let mut diag = bad_placeholder_type(tcx, vec![span]);
1309             if ty != tcx.types.err {
1310                 diag.span_suggestion(
1311                     span,
1312                     "replace `_` with the correct type",
1313                     ty.to_string(),
1314                     Applicability::MaybeIncorrect,
1315                 );
1316             }
1317             diag.emit();
1318         }
1319     }
1320
1321     ty
1322 }
1323
1324 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1325     use rustc_hir::*;
1326
1327     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1328
1329     let icx = ItemCtxt::new(tcx, def_id);
1330
1331     match tcx.hir().get(hir_id) {
1332         Node::TraitItem(item) => match item.kind {
1333             TraitItemKind::Method(..) => {
1334                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1335                 tcx.mk_fn_def(def_id, substs)
1336             }
1337             TraitItemKind::Const(ref ty, body_id) => body_id
1338                 .and_then(|body_id| {
1339                     if is_suggestable_infer_ty(ty) {
1340                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1341                     } else {
1342                         None
1343                     }
1344                 })
1345                 .unwrap_or_else(|| icx.to_ty(ty)),
1346             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1347             TraitItemKind::Type(_, None) => {
1348                 span_bug!(item.span, "associated type missing default");
1349             }
1350         },
1351
1352         Node::ImplItem(item) => match item.kind {
1353             ImplItemKind::Method(..) => {
1354                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1355                 tcx.mk_fn_def(def_id, substs)
1356             }
1357             ImplItemKind::Const(ref ty, body_id) => {
1358                 if is_suggestable_infer_ty(ty) {
1359                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1360                 } else {
1361                     icx.to_ty(ty)
1362                 }
1363             }
1364             ImplItemKind::OpaqueTy(_) => {
1365                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1366                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1367                 }
1368
1369                 find_opaque_ty_constraints(tcx, def_id)
1370             }
1371             ImplItemKind::TyAlias(ref ty) => {
1372                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1373                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1374                 }
1375
1376                 icx.to_ty(ty)
1377             }
1378         },
1379
1380         Node::Item(item) => {
1381             match item.kind {
1382                 ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
1383                     if is_suggestable_infer_ty(ty) {
1384                         infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1385                     } else {
1386                         icx.to_ty(ty)
1387                     }
1388                 }
1389                 ItemKind::TyAlias(ref self_ty, _) | ItemKind::Impl { ref self_ty, .. } => {
1390                     icx.to_ty(self_ty)
1391                 }
1392                 ItemKind::Fn(..) => {
1393                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1394                     tcx.mk_fn_def(def_id, substs)
1395                 }
1396                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1397                     let def = tcx.adt_def(def_id);
1398                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1399                     tcx.mk_adt(def, substs)
1400                 }
1401                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
1402                     find_opaque_ty_constraints(tcx, def_id)
1403                 }
1404                 // Opaque types desugared from `impl Trait`.
1405                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
1406                     tcx.typeck_tables_of(owner)
1407                         .concrete_opaque_types
1408                         .get(&def_id)
1409                         .map(|opaque| opaque.concrete_type)
1410                         .unwrap_or_else(|| {
1411                             // This can occur if some error in the
1412                             // owner fn prevented us from populating
1413                             // the `concrete_opaque_types` table.
1414                             tcx.sess.delay_span_bug(
1415                                 DUMMY_SP,
1416                                 &format!(
1417                                     "owner {:?} has no opaque type for {:?} in its tables",
1418                                     owner, def_id,
1419                                 ),
1420                             );
1421                             tcx.types.err
1422                         })
1423                 }
1424                 ItemKind::Trait(..)
1425                 | ItemKind::TraitAlias(..)
1426                 | ItemKind::Mod(..)
1427                 | ItemKind::ForeignMod(..)
1428                 | ItemKind::GlobalAsm(..)
1429                 | ItemKind::ExternCrate(..)
1430                 | ItemKind::Use(..) => {
1431                     span_bug!(
1432                         item.span,
1433                         "compute_type_of_item: unexpected item type: {:?}",
1434                         item.kind
1435                     );
1436                 }
1437             }
1438         }
1439
1440         Node::ForeignItem(foreign_item) => match foreign_item.kind {
1441             ForeignItemKind::Fn(..) => {
1442                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1443                 tcx.mk_fn_def(def_id, substs)
1444             }
1445             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1446             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1447         },
1448
1449         Node::Ctor(&ref def) | Node::Variant(hir::Variant { data: ref def, .. }) => match *def {
1450             VariantData::Unit(..) | VariantData::Struct(..) => {
1451                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1452             }
1453             VariantData::Tuple(..) => {
1454                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1455                 tcx.mk_fn_def(def_id, substs)
1456             }
1457         },
1458
1459         Node::Field(field) => icx.to_ty(&field.ty),
1460
1461         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) => {
1462             if gen.is_some() {
1463                 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1464             }
1465
1466             let substs = InternalSubsts::identity_for_item(tcx, def_id);
1467             tcx.mk_closure(def_id, substs)
1468         }
1469
1470         Node::AnonConst(_) => {
1471             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1472             match parent_node {
1473                 Node::Ty(&hir::Ty { kind: hir::TyKind::Array(_, ref constant), .. })
1474                 | Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref constant), .. })
1475                 | Node::Expr(&hir::Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1476                     if constant.hir_id == hir_id =>
1477                 {
1478                     tcx.types.usize
1479                 }
1480
1481                 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
1482                     tcx.adt_def(tcx.hir().get_parent_did(hir_id)).repr.discr_type().to_ty(tcx)
1483                 }
1484
1485                 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. })
1486                 | Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. })
1487                 | Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. })
1488                 | Node::TraitRef(..) => {
1489                     let path = match parent_node {
1490                         Node::Ty(&hir::Ty {
1491                             kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1492                             ..
1493                         })
1494                         | Node::Expr(&hir::Expr {
1495                             kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1496                             ..
1497                         }) => Some(&**path),
1498                         Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1499                             if let QPath::Resolved(_, ref path) = **path {
1500                                 Some(&**path)
1501                             } else {
1502                                 None
1503                             }
1504                         }
1505                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1506                         _ => None,
1507                     };
1508
1509                     if let Some(path) = path {
1510                         let arg_index = path
1511                             .segments
1512                             .iter()
1513                             .filter_map(|seg| seg.args.as_ref())
1514                             .map(|generic_args| generic_args.args.as_ref())
1515                             .find_map(|args| {
1516                                 args.iter()
1517                                     .filter(|arg| arg.is_const())
1518                                     .enumerate()
1519                                     .filter(|(_, arg)| arg.id() == hir_id)
1520                                     .map(|(index, _)| index)
1521                                     .next()
1522                             })
1523                             .unwrap_or_else(|| {
1524                                 bug!("no arg matching AnonConst in path");
1525                             });
1526
1527                         // We've encountered an `AnonConst` in some path, so we need to
1528                         // figure out which generic parameter it corresponds to and return
1529                         // the relevant type.
1530                         let generics = match path.res {
1531                             Res::Def(DefKind::Ctor(..), def_id) => {
1532                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1533                             }
1534                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1535                             Res::Err => return tcx.types.err,
1536                             res => {
1537                                 tcx.sess.delay_span_bug(
1538                                     DUMMY_SP,
1539                                     &format!("unexpected const parent path def {:?}", res,),
1540                                 );
1541                                 return tcx.types.err;
1542                             }
1543                         };
1544
1545                         generics
1546                             .params
1547                             .iter()
1548                             .filter(|param| {
1549                                 if let ty::GenericParamDefKind::Const = param.kind {
1550                                     true
1551                                 } else {
1552                                     false
1553                                 }
1554                             })
1555                             .nth(arg_index)
1556                             .map(|param| tcx.type_of(param.def_id))
1557                             // This is no generic parameter associated with the arg. This is
1558                             // probably from an extra arg where one is not needed.
1559                             .unwrap_or(tcx.types.err)
1560                     } else {
1561                         tcx.sess.delay_span_bug(
1562                             DUMMY_SP,
1563                             &format!("unexpected const parent path {:?}", parent_node,),
1564                         );
1565                         return tcx.types.err;
1566                     }
1567                 }
1568
1569                 x => {
1570                     tcx.sess.delay_span_bug(
1571                         DUMMY_SP,
1572                         &format!("unexpected const parent in type_of_def_id(): {:?}", x),
1573                     );
1574                     tcx.types.err
1575                 }
1576             }
1577         }
1578
1579         Node::GenericParam(param) => match &param.kind {
1580             hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1581             hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1582                 let ty = icx.to_ty(hir_ty);
1583                 if !tcx.features().const_compare_raw_pointers {
1584                     let err = match ty.peel_refs().kind {
1585                         ty::FnPtr(_) => Some("function pointers"),
1586                         ty::RawPtr(_) => Some("raw pointers"),
1587                         _ => None,
1588                     };
1589                     if let Some(unsupported_type) = err {
1590                         feature_err(
1591                             &tcx.sess.parse_sess,
1592                             sym::const_compare_raw_pointers,
1593                             hir_ty.span,
1594                             &format!(
1595                                 "using {} as const generic parameters is unstable",
1596                                 unsupported_type
1597                             ),
1598                         )
1599                         .emit();
1600                     };
1601                 }
1602                 if traits::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
1603                     .is_some()
1604                 {
1605                     struct_span_err!(
1606                         tcx.sess,
1607                         hir_ty.span,
1608                         E0741,
1609                         "the types of const generic parameters must derive `PartialEq` and `Eq`",
1610                     )
1611                     .span_label(
1612                         hir_ty.span,
1613                         format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1614                     )
1615                     .emit();
1616                 }
1617                 ty
1618             }
1619             x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1620         },
1621
1622         x => {
1623             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1624         }
1625     }
1626 }
1627
1628 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1629     use rustc_hir::{ImplItem, Item, TraitItem};
1630
1631     debug!("find_opaque_ty_constraints({:?})", def_id);
1632
1633     struct ConstraintLocator<'tcx> {
1634         tcx: TyCtxt<'tcx>,
1635         def_id: DefId,
1636         // (first found type span, actual type, mapping from the opaque type's generic
1637         // parameters to the concrete type's generic parameters)
1638         //
1639         // The mapping is an index for each use site of a generic parameter in the concrete type
1640         //
1641         // The indices index into the generic parameters on the opaque type.
1642         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1643     }
1644
1645     impl ConstraintLocator<'tcx> {
1646         fn check(&mut self, def_id: DefId) {
1647             // Don't try to check items that cannot possibly constrain the type.
1648             if !self.tcx.has_typeck_tables(def_id) {
1649                 debug!(
1650                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1651                     self.def_id, def_id,
1652                 );
1653                 return;
1654             }
1655             let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
1656             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1657                 debug!(
1658                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1659                     self.def_id, def_id, ty,
1660                 );
1661
1662                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1663                 let span = self.tcx.def_span(def_id);
1664                 // used to quickly look up the position of a generic parameter
1665                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1666                 // Skipping binder is ok, since we only use this to find generic parameters and
1667                 // their positions.
1668                 for (idx, subst) in substs.iter().enumerate() {
1669                     if let GenericArgKind::Type(ty) = subst.unpack() {
1670                         if let ty::Param(p) = ty.kind {
1671                             if index_map.insert(p, idx).is_some() {
1672                                 // There was already an entry for `p`, meaning a generic parameter
1673                                 // was used twice.
1674                                 self.tcx.sess.span_err(
1675                                     span,
1676                                     &format!(
1677                                         "defining opaque type use restricts opaque \
1678                                          type by using the generic parameter `{}` twice",
1679                                         p,
1680                                     ),
1681                                 );
1682                                 return;
1683                             }
1684                         } else {
1685                             self.tcx.sess.delay_span_bug(
1686                                 span,
1687                                 &format!(
1688                                     "non-defining opaque ty use in defining scope: {:?}, {:?}",
1689                                     concrete_type, substs,
1690                                 ),
1691                             );
1692                         }
1693                     }
1694                 }
1695                 // Compute the index within the opaque type for each generic parameter used in
1696                 // the concrete type.
1697                 let indices = concrete_type
1698                     .subst(self.tcx, substs)
1699                     .walk()
1700                     .filter_map(|t| match &t.kind {
1701                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1702                         _ => None,
1703                     })
1704                     .collect();
1705                 let is_param = |ty: Ty<'_>| match ty.kind {
1706                     ty::Param(_) => true,
1707                     _ => false,
1708                 };
1709                 let bad_substs: Vec<_> = substs
1710                     .iter()
1711                     .enumerate()
1712                     .filter_map(|(i, k)| {
1713                         if let GenericArgKind::Type(ty) = k.unpack() { Some((i, ty)) } else { None }
1714                     })
1715                     .filter(|(_, ty)| !is_param(ty))
1716                     .collect();
1717
1718                 if !bad_substs.is_empty() {
1719                     let identity_substs = InternalSubsts::identity_for_item(self.tcx, self.def_id);
1720                     for (i, bad_subst) in bad_substs {
1721                         self.tcx.sess.span_err(
1722                             span,
1723                             &format!(
1724                                 "defining opaque type use does not fully define opaque type: \
1725                             generic parameter `{}` is specified as concrete type `{}`",
1726                                 identity_substs.type_at(i),
1727                                 bad_subst
1728                             ),
1729                         );
1730                     }
1731                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1732                     let mut ty = concrete_type.walk().fuse();
1733                     let mut p_ty = prev_ty.walk().fuse();
1734                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1735                         // Type parameters are equal to any other type parameter for the purpose of
1736                         // concrete type equality, as it is possible to obtain the same type just
1737                         // by passing matching parameters to a function.
1738                         (ty::Param(_), ty::Param(_)) => true,
1739                         _ => t == p,
1740                     });
1741                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1742                         debug!("find_opaque_ty_constraints: span={:?}", span);
1743                         // Found different concrete types for the opaque type.
1744                         let mut err = self.tcx.sess.struct_span_err(
1745                             span,
1746                             "concrete type differs from previous defining opaque type use",
1747                         );
1748                         err.span_label(
1749                             span,
1750                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1751                         );
1752                         err.span_note(prev_span, "previous use here");
1753                         err.emit();
1754                     } else if indices != *prev_indices {
1755                         // Found "same" concrete types, but the generic parameter order differs.
1756                         let mut err = self.tcx.sess.struct_span_err(
1757                             span,
1758                             "concrete type's generic parameters differ from previous defining use",
1759                         );
1760                         use std::fmt::Write;
1761                         let mut s = String::new();
1762                         write!(s, "expected [").unwrap();
1763                         let list = |s: &mut String, indices: &Vec<usize>| {
1764                             let mut indices = indices.iter().cloned();
1765                             if let Some(first) = indices.next() {
1766                                 write!(s, "`{}`", substs[first]).unwrap();
1767                                 for i in indices {
1768                                     write!(s, ", `{}`", substs[i]).unwrap();
1769                                 }
1770                             }
1771                         };
1772                         list(&mut s, prev_indices);
1773                         write!(s, "], got [").unwrap();
1774                         list(&mut s, &indices);
1775                         write!(s, "]").unwrap();
1776                         err.span_label(span, s);
1777                         err.span_note(prev_span, "previous use here");
1778                         err.emit();
1779                     }
1780                 } else {
1781                     self.found = Some((span, concrete_type, indices));
1782                 }
1783             } else {
1784                 debug!(
1785                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1786                     self.def_id, def_id,
1787                 );
1788             }
1789         }
1790     }
1791
1792     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1793         type Map = Map<'tcx>;
1794
1795         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1796             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1797         }
1798         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
1799             debug!("find_existential_constraints: visiting {:?}", it);
1800             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1801             // The opaque type itself or its children are not within its reveal scope.
1802             if def_id != self.def_id {
1803                 self.check(def_id);
1804                 intravisit::walk_item(self, it);
1805             }
1806         }
1807         fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
1808             debug!("find_existential_constraints: visiting {:?}", it);
1809             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1810             // The opaque type itself or its children are not within its reveal scope.
1811             if def_id != self.def_id {
1812                 self.check(def_id);
1813                 intravisit::walk_impl_item(self, it);
1814             }
1815         }
1816         fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
1817             debug!("find_existential_constraints: visiting {:?}", it);
1818             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1819             self.check(def_id);
1820             intravisit::walk_trait_item(self, it);
1821         }
1822     }
1823
1824     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1825     let scope = tcx.hir().get_defining_scope(hir_id);
1826     let mut locator = ConstraintLocator { def_id, tcx, found: None };
1827
1828     debug!("find_opaque_ty_constraints: scope={:?}", scope);
1829
1830     if scope == hir::CRATE_HIR_ID {
1831         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1832     } else {
1833         debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1834         match tcx.hir().get(scope) {
1835             // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1836             // This allows our visitor to process the defining item itself, causing
1837             // it to pick up any 'sibling' defining uses.
1838             //
1839             // For example, this code:
1840             // ```
1841             // fn foo() {
1842             //     type Blah = impl Debug;
1843             //     let my_closure = || -> Blah { true };
1844             // }
1845             // ```
1846             //
1847             // requires us to explicitly process `foo()` in order
1848             // to notice the defining usage of `Blah`.
1849             Node::Item(ref it) => locator.visit_item(it),
1850             Node::ImplItem(ref it) => locator.visit_impl_item(it),
1851             Node::TraitItem(ref it) => locator.visit_trait_item(it),
1852             other => bug!("{:?} is not a valid scope for an opaque type item", other),
1853         }
1854     }
1855
1856     match locator.found {
1857         Some((_, ty, _)) => ty,
1858         None => {
1859             let span = tcx.def_span(def_id);
1860             tcx.sess.span_err(span, "could not find defining uses");
1861             tcx.types.err
1862         }
1863     }
1864 }
1865
1866 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1867     generic_args
1868         .iter()
1869         .filter_map(|arg| match arg {
1870             hir::GenericArg::Type(ty) => Some(ty),
1871             _ => None,
1872         })
1873         .any(is_suggestable_infer_ty)
1874 }
1875
1876 /// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
1877 /// use inference to provide suggestions for the appropriate type if possible.
1878 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1879     use hir::TyKind::*;
1880     match &ty.kind {
1881         Infer => true,
1882         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1883         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1884         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1885         Def(_, generic_args) => are_suggestable_generic_args(generic_args),
1886         Path(hir::QPath::TypeRelative(ty, segment)) => {
1887             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1888         }
1889         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1890             ty_opt.map_or(false, is_suggestable_infer_ty)
1891                 || segments
1892                     .iter()
1893                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1894         }
1895         _ => false,
1896     }
1897 }
1898
1899 pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1900     if let hir::FunctionRetTy::Return(ref ty) = output {
1901         if is_suggestable_infer_ty(ty) {
1902             return Some(&**ty);
1903         }
1904     }
1905     None
1906 }
1907
1908 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1909     use rustc_hir::Node::*;
1910     use rustc_hir::*;
1911
1912     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1913
1914     let icx = ItemCtxt::new(tcx, def_id);
1915
1916     match tcx.hir().get(hir_id) {
1917         TraitItem(hir::TraitItem {
1918             kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1919             ident,
1920             generics,
1921             ..
1922         })
1923         | ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
1924         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1925             match get_infer_ret_ty(&sig.decl.output) {
1926                 Some(ty) => {
1927                     let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1928                     let mut visitor = PlaceholderHirTyCollector::default();
1929                     visitor.visit_ty(ty);
1930                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1931                     let ret_ty = fn_sig.output();
1932                     if ret_ty != tcx.types.err {
1933                         diag.span_suggestion(
1934                             ty.span,
1935                             "replace with the correct return type",
1936                             ret_ty.to_string(),
1937                             Applicability::MaybeIncorrect,
1938                         );
1939                     }
1940                     diag.emit();
1941                     ty::Binder::bind(fn_sig)
1942                 }
1943                 None => AstConv::ty_of_fn(
1944                     &icx,
1945                     sig.header.unsafety,
1946                     sig.header.abi,
1947                     &sig.decl,
1948                     &generics.params[..],
1949                     Some(ident.span),
1950                 ),
1951             }
1952         }
1953
1954         TraitItem(hir::TraitItem {
1955             kind: TraitItemKind::Method(FnSig { header, decl }, _),
1956             ident,
1957             generics,
1958             ..
1959         }) => AstConv::ty_of_fn(
1960             &icx,
1961             header.unsafety,
1962             header.abi,
1963             decl,
1964             &generics.params[..],
1965             Some(ident.span),
1966         ),
1967
1968         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
1969             let abi = tcx.hir().get_foreign_abi(hir_id);
1970             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1971         }
1972
1973         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1974             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1975             let inputs =
1976                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1977             ty::Binder::bind(tcx.mk_fn_sig(
1978                 inputs,
1979                 ty,
1980                 false,
1981                 hir::Unsafety::Normal,
1982                 abi::Abi::Rust,
1983             ))
1984         }
1985
1986         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1987             // Closure signatures are not like other function
1988             // signatures and cannot be accessed through `fn_sig`. For
1989             // example, a closure signature excludes the `self`
1990             // argument. In any case they are embedded within the
1991             // closure type as part of the `ClosureSubsts`.
1992             //
1993             // To get
1994             // the signature of a closure, you should use the
1995             // `closure_sig` method on the `ClosureSubsts`:
1996             //
1997             //    closure_substs.sig(def_id, tcx)
1998             //
1999             // or, inside of an inference context, you can use
2000             //
2001             //    infcx.closure_sig(def_id, closure_substs)
2002             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
2003         }
2004
2005         x => {
2006             bug!("unexpected sort of node in fn_sig(): {:?}", x);
2007         }
2008     }
2009 }
2010
2011 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
2012     let icx = ItemCtxt::new(tcx, def_id);
2013
2014     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2015     match tcx.hir().expect_item(hir_id).kind {
2016         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
2017             let selfty = tcx.type_of(def_id);
2018             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
2019         }),
2020         _ => bug!(),
2021     }
2022 }
2023
2024 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2025     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2026     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2027     let item = tcx.hir().expect_item(hir_id);
2028     match &item.kind {
2029         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative, .. } => {
2030             if is_rustc_reservation {
2031                 tcx.sess.span_err(item.span, "reservation impls can't be negative");
2032             }
2033             ty::ImplPolarity::Negative
2034         }
2035         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
2036             if is_rustc_reservation {
2037                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2038             }
2039             ty::ImplPolarity::Positive
2040         }
2041         hir::ItemKind::Impl {
2042             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
2043         } => {
2044             if is_rustc_reservation {
2045                 ty::ImplPolarity::Reservation
2046             } else {
2047                 ty::ImplPolarity::Positive
2048             }
2049         }
2050         ref item => bug!("impl_polarity: {:?} not an impl", item),
2051     }
2052 }
2053
2054 /// Returns the early-bound lifetimes declared in this generics
2055 /// listing. For anything other than fns/methods, this is just all
2056 /// the lifetimes that are declared. For fns or methods, we have to
2057 /// screen out those that do not appear in any where-clauses etc using
2058 /// `resolve_lifetime::early_bound_lifetimes`.
2059 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2060     tcx: TyCtxt<'tcx>,
2061     generics: &'a hir::Generics<'a>,
2062 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2063     generics.params.iter().filter(move |param| match param.kind {
2064         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2065         _ => false,
2066     })
2067 }
2068
2069 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2070 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2071 /// inferred constraints concerning which regions outlive other regions.
2072 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2073     debug!("predicates_defined_on({:?})", def_id);
2074     let mut result = tcx.explicit_predicates_of(def_id);
2075     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2076     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2077     if !inferred_outlives.is_empty() {
2078         debug!(
2079             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2080             def_id, inferred_outlives,
2081         );
2082         if result.predicates.is_empty() {
2083             result.predicates = inferred_outlives;
2084         } else {
2085             result.predicates = tcx
2086                 .arena
2087                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2088         }
2089     }
2090     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2091     result
2092 }
2093
2094 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2095 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2096 /// `Self: Trait` predicates for traits.
2097 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2098     let mut result = tcx.predicates_defined_on(def_id);
2099
2100     if tcx.is_trait(def_id) {
2101         // For traits, add `Self: Trait` predicate. This is
2102         // not part of the predicates that a user writes, but it
2103         // is something that one must prove in order to invoke a
2104         // method or project an associated type.
2105         //
2106         // In the chalk setup, this predicate is not part of the
2107         // "predicates" for a trait item. But it is useful in
2108         // rustc because if you directly (e.g.) invoke a trait
2109         // method like `Trait::method(...)`, you must naturally
2110         // prove that the trait applies to the types that were
2111         // used, and adding the predicate into this list ensures
2112         // that this is done.
2113         let span = tcx.def_span(def_id);
2114         result.predicates =
2115             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2116                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(),
2117                 span,
2118             ))));
2119     }
2120     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2121     result
2122 }
2123
2124 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2125 /// N.B., this does not include any implied/inferred constraints.
2126 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2127     use rustc_data_structures::fx::FxHashSet;
2128     use rustc_hir::*;
2129
2130     debug!("explicit_predicates_of(def_id={:?})", def_id);
2131
2132     /// A data structure with unique elements, which preserves order of insertion.
2133     /// Preserving the order of insertion is important here so as not to break
2134     /// compile-fail UI tests.
2135     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2136     struct UniquePredicates<'tcx> {
2137         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2138         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2139     }
2140
2141     impl<'tcx> UniquePredicates<'tcx> {
2142         fn new() -> Self {
2143             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
2144         }
2145
2146         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2147             if self.uniques.insert(value) {
2148                 self.predicates.push(value);
2149             }
2150         }
2151
2152         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2153             for value in iter {
2154                 self.push(value);
2155             }
2156         }
2157     }
2158
2159     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2160     let node = tcx.hir().get(hir_id);
2161
2162     let mut is_trait = None;
2163     let mut is_default_impl_trait = None;
2164
2165     let icx = ItemCtxt::new(tcx, def_id);
2166     let constness = icx.default_constness_for_trait_bounds();
2167
2168     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2169
2170     let mut predicates = UniquePredicates::new();
2171
2172     let ast_generics = match node {
2173         Node::TraitItem(item) => &item.generics,
2174
2175         Node::ImplItem(item) => match item.kind {
2176             ImplItemKind::OpaqueTy(ref bounds) => {
2177                 ty::print::with_no_queries(|| {
2178                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2179                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2180                     debug!(
2181                         "explicit_predicates_of({:?}): created opaque type {:?}",
2182                         def_id, opaque_ty
2183                     );
2184
2185                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2186                     let bounds = AstConv::compute_bounds(
2187                         &icx,
2188                         opaque_ty,
2189                         bounds,
2190                         SizedByDefault::Yes,
2191                         tcx.def_span(def_id),
2192                     );
2193
2194                     predicates.extend(bounds.predicates(tcx, opaque_ty));
2195                     &item.generics
2196                 })
2197             }
2198             _ => &item.generics,
2199         },
2200
2201         Node::Item(item) => {
2202             match item.kind {
2203                 ItemKind::Impl { defaultness, ref generics, .. } => {
2204                     if defaultness.is_default() {
2205                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2206                     }
2207                     generics
2208                 }
2209                 ItemKind::Fn(.., ref generics, _)
2210                 | ItemKind::TyAlias(_, ref generics)
2211                 | ItemKind::Enum(_, ref generics)
2212                 | ItemKind::Struct(_, ref generics)
2213                 | ItemKind::Union(_, ref generics) => generics,
2214
2215                 ItemKind::Trait(_, _, ref generics, .., items) => {
2216                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2217                     generics
2218                 }
2219                 ItemKind::TraitAlias(ref generics, _) => {
2220                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
2221                     generics
2222                 }
2223                 ItemKind::OpaqueTy(OpaqueTy {
2224                     ref bounds,
2225                     impl_trait_fn,
2226                     ref generics,
2227                     origin: _,
2228                 }) => {
2229                     let bounds_predicates = ty::print::with_no_queries(|| {
2230                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
2231                         let opaque_ty = tcx.mk_opaque(def_id, substs);
2232
2233                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2234                         let bounds = AstConv::compute_bounds(
2235                             &icx,
2236                             opaque_ty,
2237                             bounds,
2238                             SizedByDefault::Yes,
2239                             tcx.def_span(def_id),
2240                         );
2241
2242                         bounds.predicates(tcx, opaque_ty)
2243                     });
2244                     if impl_trait_fn.is_some() {
2245                         // opaque types
2246                         return ty::GenericPredicates {
2247                             parent: None,
2248                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2249                         };
2250                     } else {
2251                         // named opaque types
2252                         predicates.extend(bounds_predicates);
2253                         generics
2254                     }
2255                 }
2256
2257                 _ => NO_GENERICS,
2258             }
2259         }
2260
2261         Node::ForeignItem(item) => match item.kind {
2262             ForeignItemKind::Static(..) => NO_GENERICS,
2263             ForeignItemKind::Fn(_, _, ref generics) => generics,
2264             ForeignItemKind::Type => NO_GENERICS,
2265         },
2266
2267         _ => NO_GENERICS,
2268     };
2269
2270     let generics = tcx.generics_of(def_id);
2271     let parent_count = generics.parent_count as u32;
2272     let has_own_self = generics.has_self && parent_count == 0;
2273
2274     // Below we'll consider the bounds on the type parameters (including `Self`)
2275     // and the explicit where-clauses, but to get the full set of predicates
2276     // on a trait we need to add in the supertrait bounds and bounds found on
2277     // associated types.
2278     if let Some((_trait_ref, _)) = is_trait {
2279         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2280     }
2281
2282     // In default impls, we can assume that the self type implements
2283     // the trait. So in:
2284     //
2285     //     default impl Foo for Bar { .. }
2286     //
2287     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2288     // (see below). Recall that a default impl is not itself an impl, but rather a
2289     // set of defaults that can be incorporated into another impl.
2290     if let Some(trait_ref) = is_default_impl_trait {
2291         predicates.push((
2292             trait_ref.to_poly_trait_ref().without_const().to_predicate(),
2293             tcx.def_span(def_id),
2294         ));
2295     }
2296
2297     // Collect the region predicates that were declared inline as
2298     // well. In the case of parameters declared on a fn or method, we
2299     // have to be careful to only iterate over early-bound regions.
2300     let mut index = parent_count + has_own_self as u32;
2301     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2302         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2303             def_id: tcx.hir().local_def_id(param.hir_id),
2304             index,
2305             name: param.name.ident().name,
2306         }));
2307         index += 1;
2308
2309         match param.kind {
2310             GenericParamKind::Lifetime { .. } => {
2311                 param.bounds.iter().for_each(|bound| match bound {
2312                     hir::GenericBound::Outlives(lt) => {
2313                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2314                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2315                         predicates.push((outlives.to_predicate(), lt.span));
2316                     }
2317                     _ => bug!(),
2318                 });
2319             }
2320             _ => bug!(),
2321         }
2322     }
2323
2324     // Collect the predicates that were written inline by the user on each
2325     // type parameter (e.g., `<T: Foo>`).
2326     for param in ast_generics.params {
2327         if let GenericParamKind::Type { .. } = param.kind {
2328             let name = param.name.ident().name;
2329             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2330             index += 1;
2331
2332             let sized = SizedByDefault::Yes;
2333             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2334             predicates.extend(bounds.predicates(tcx, param_ty));
2335         }
2336     }
2337
2338     // Add in the bounds that appear in the where-clause.
2339     let where_clause = &ast_generics.where_clause;
2340     for predicate in where_clause.predicates {
2341         match predicate {
2342             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2343                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2344
2345                 // Keep the type around in a dummy predicate, in case of no bounds.
2346                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2347                 // is still checked for WF.
2348                 if bound_pred.bounds.is_empty() {
2349                     if let ty::Param(_) = ty.kind {
2350                         // This is a `where T:`, which can be in the HIR from the
2351                         // transformation that moves `?Sized` to `T`'s declaration.
2352                         // We can skip the predicate because type parameters are
2353                         // trivially WF, but also we *should*, to avoid exposing
2354                         // users who never wrote `where Type:,` themselves, to
2355                         // compiler/tooling bugs from not handling WF predicates.
2356                     } else {
2357                         let span = bound_pred.bounded_ty.span;
2358                         let re_root_empty = tcx.lifetimes.re_root_empty;
2359                         let predicate = ty::OutlivesPredicate(ty, re_root_empty);
2360                         predicates.push((
2361                             ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)),
2362                             span,
2363                         ));
2364                     }
2365                 }
2366
2367                 for bound in bound_pred.bounds.iter() {
2368                     match bound {
2369                         &hir::GenericBound::Trait(ref poly_trait_ref, modifier) => {
2370                             let constness = match modifier {
2371                                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2372                                 hir::TraitBoundModifier::None => constness,
2373                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
2374                             };
2375
2376                             let mut bounds = Bounds::default();
2377                             let _ = AstConv::instantiate_poly_trait_ref(
2378                                 &icx,
2379                                 poly_trait_ref,
2380                                 constness,
2381                                 ty,
2382                                 &mut bounds,
2383                             );
2384                             predicates.extend(bounds.predicates(tcx, ty));
2385                         }
2386
2387                         &hir::GenericBound::Outlives(ref lifetime) => {
2388                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2389                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2390                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2391                         }
2392                     }
2393                 }
2394             }
2395
2396             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2397                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2398                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2399                     let (r2, span) = match bound {
2400                         hir::GenericBound::Outlives(lt) => {
2401                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2402                         }
2403                         _ => bug!(),
2404                     };
2405                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2406
2407                     (ty::Predicate::RegionOutlives(pred), span)
2408                 }))
2409             }
2410
2411             &hir::WherePredicate::EqPredicate(..) => {
2412                 // FIXME(#20041)
2413             }
2414         }
2415     }
2416
2417     // Add predicates from associated type bounds.
2418     if let Some((self_trait_ref, trait_items)) = is_trait {
2419         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2420             associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2421         }))
2422     }
2423
2424     let mut predicates = predicates.predicates;
2425
2426     // Subtle: before we store the predicates into the tcx, we
2427     // sort them so that predicates like `T: Foo<Item=U>` come
2428     // before uses of `U`.  This avoids false ambiguity errors
2429     // in trait checking. See `setup_constraining_predicates`
2430     // for details.
2431     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2432         let self_ty = tcx.type_of(def_id);
2433         let trait_ref = tcx.impl_trait_ref(def_id);
2434         cgp::setup_constraining_predicates(
2435             tcx,
2436             &mut predicates,
2437             trait_ref,
2438             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2439         );
2440     }
2441
2442     let result = ty::GenericPredicates {
2443         parent: generics.parent,
2444         predicates: tcx.arena.alloc_from_iter(predicates),
2445     };
2446     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2447     result
2448 }
2449
2450 fn associated_item_predicates(
2451     tcx: TyCtxt<'tcx>,
2452     def_id: DefId,
2453     self_trait_ref: ty::TraitRef<'tcx>,
2454     trait_item_ref: &hir::TraitItemRef,
2455 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2456     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2457     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2458     let bounds = match trait_item.kind {
2459         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2460         _ => return Vec::new(),
2461     };
2462
2463     let is_gat = !tcx.generics_of(item_def_id).params.is_empty();
2464
2465     let mut had_error = false;
2466
2467     let mut unimplemented_error = |arg_kind: &str| {
2468         if !had_error {
2469             tcx.sess
2470                 .struct_span_err(
2471                     trait_item.span,
2472                     &format!("{}-generic associated types are not yet implemented", arg_kind),
2473                 )
2474                 .note("for more information, see https://github.com/rust-lang/rust/issues/44265")
2475                 .emit();
2476             had_error = true;
2477         }
2478     };
2479
2480     let mk_bound_param = |param: &ty::GenericParamDef, _: &_| {
2481         match param.kind {
2482             ty::GenericParamDefKind::Lifetime => tcx
2483                 .mk_region(ty::RegionKind::ReLateBound(
2484                     ty::INNERMOST,
2485                     ty::BoundRegion::BrNamed(param.def_id, param.name),
2486                 ))
2487                 .into(),
2488             // FIXME(generic_associated_types): Use bound types and constants
2489             // once they are handled by the trait system.
2490             ty::GenericParamDefKind::Type { .. } => {
2491                 unimplemented_error("type");
2492                 tcx.types.err.into()
2493             }
2494             ty::GenericParamDefKind::Const => {
2495                 unimplemented_error("const");
2496                 tcx.consts.err.into()
2497             }
2498         }
2499     };
2500
2501     let bound_substs = if is_gat {
2502         // Given:
2503         //
2504         // trait X<'a, B, const C: usize> {
2505         //     type T<'d, E, const F: usize>: Default;
2506         // }
2507         //
2508         // We need to create predicates on the trait:
2509         //
2510         // for<'d, E, const F: usize>
2511         // <Self as X<'a, B, const C: usize>>::T<'d, E, const F: usize>: Sized + Default
2512         //
2513         // We substitute escaping bound parameters for the generic
2514         // arguments to the associated type which are then bound by
2515         // the `Binder` around the the predicate.
2516         //
2517         // FIXME(generic_associated_types): Currently only lifetimes are handled.
2518         self_trait_ref.substs.extend_to(tcx, item_def_id, mk_bound_param)
2519     } else {
2520         self_trait_ref.substs
2521     };
2522
2523     let assoc_ty = tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id), bound_substs);
2524
2525     let bounds = AstConv::compute_bounds(
2526         &ItemCtxt::new(tcx, def_id),
2527         assoc_ty,
2528         bounds,
2529         SizedByDefault::Yes,
2530         trait_item.span,
2531     );
2532
2533     let predicates = bounds.predicates(tcx, assoc_ty);
2534
2535     if is_gat {
2536         // We use shifts to get the regions that we're substituting to
2537         // be bound by the binders in the `Predicate`s rather that
2538         // escaping.
2539         let shifted_in = ty::fold::shift_vars(tcx, &predicates, 1);
2540         let substituted = shifted_in.subst(tcx, bound_substs);
2541         ty::fold::shift_out_vars(tcx, &substituted, 1)
2542     } else {
2543         predicates
2544     }
2545 }
2546
2547 /// Converts a specific `GenericBound` from the AST into a set of
2548 /// predicates that apply to the self type. A vector is returned
2549 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2550 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2551 /// and `<T as Bar>::X == i32`).
2552 fn predicates_from_bound<'tcx>(
2553     astconv: &dyn AstConv<'tcx>,
2554     param_ty: Ty<'tcx>,
2555     bound: &'tcx hir::GenericBound<'tcx>,
2556     constness: ast::Constness,
2557 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2558     match *bound {
2559         hir::GenericBound::Trait(ref tr, modifier) => {
2560             let constness = match modifier {
2561                 hir::TraitBoundModifier::Maybe => return vec![],
2562                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2563                 hir::TraitBoundModifier::None => constness,
2564             };
2565
2566             let mut bounds = Bounds::default();
2567             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2568             bounds.predicates(astconv.tcx(), param_ty)
2569         }
2570         hir::GenericBound::Outlives(ref lifetime) => {
2571             let region = astconv.ast_region_to_region(lifetime, None);
2572             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2573             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2574         }
2575     }
2576 }
2577
2578 fn compute_sig_of_foreign_fn_decl<'tcx>(
2579     tcx: TyCtxt<'tcx>,
2580     def_id: DefId,
2581     decl: &'tcx hir::FnDecl<'tcx>,
2582     abi: abi::Abi,
2583 ) -> ty::PolyFnSig<'tcx> {
2584     let unsafety = if abi == abi::Abi::RustIntrinsic {
2585         intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2586     } else {
2587         hir::Unsafety::Unsafe
2588     };
2589     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
2590
2591     // Feature gate SIMD types in FFI, since I am not sure that the
2592     // ABIs are handled at all correctly. -huonw
2593     if abi != abi::Abi::RustIntrinsic
2594         && abi != abi::Abi::PlatformIntrinsic
2595         && !tcx.features().simd_ffi
2596     {
2597         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2598             if ty.is_simd() {
2599                 tcx.sess
2600                     .struct_span_err(
2601                         ast_ty.span,
2602                         &format!(
2603                             "use of SIMD type `{}` in FFI is highly experimental and \
2604                             may result in invalid code",
2605                             tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2606                         ),
2607                     )
2608                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2609                     .emit();
2610             }
2611         };
2612         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2613             check(&input, ty)
2614         }
2615         if let hir::FunctionRetTy::Return(ref ty) = decl.output {
2616             check(&ty, *fty.output().skip_binder())
2617         }
2618     }
2619
2620     fty
2621 }
2622
2623 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2624     match tcx.hir().get_if_local(def_id) {
2625         Some(Node::ForeignItem(..)) => true,
2626         Some(_) => false,
2627         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2628     }
2629 }
2630
2631 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2632     match tcx.hir().get_if_local(def_id) {
2633         Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. }))
2634         | Some(Node::ForeignItem(&hir::ForeignItem {
2635             kind: hir::ForeignItemKind::Static(_, mutbl),
2636             ..
2637         })) => Some(mutbl),
2638         Some(_) => None,
2639         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2640     }
2641 }
2642
2643 fn from_target_feature(
2644     tcx: TyCtxt<'_>,
2645     id: DefId,
2646     attr: &ast::Attribute,
2647     whitelist: &FxHashMap<String, Option<Symbol>>,
2648     target_features: &mut Vec<Symbol>,
2649 ) {
2650     let list = match attr.meta_item_list() {
2651         Some(list) => list,
2652         None => return,
2653     };
2654     let bad_item = |span| {
2655         let msg = "malformed `target_feature` attribute input";
2656         let code = "enable = \"..\"".to_owned();
2657         tcx.sess
2658             .struct_span_err(span, &msg)
2659             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2660             .emit();
2661     };
2662     let rust_features = tcx.features();
2663     for item in list {
2664         // Only `enable = ...` is accepted in the meta-item list.
2665         if !item.check_name(sym::enable) {
2666             bad_item(item.span());
2667             continue;
2668         }
2669
2670         // Must be of the form `enable = "..."` (a string).
2671         let value = match item.value_str() {
2672             Some(value) => value,
2673             None => {
2674                 bad_item(item.span());
2675                 continue;
2676             }
2677         };
2678
2679         // We allow comma separation to enable multiple features.
2680         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2681             // Only allow whitelisted features per platform.
2682             let feature_gate = match whitelist.get(feature) {
2683                 Some(g) => g,
2684                 None => {
2685                     let msg =
2686                         format!("the feature named `{}` is not valid for this target", feature);
2687                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2688                     err.span_label(
2689                         item.span(),
2690                         format!("`{}` is not valid for this target", feature),
2691                     );
2692                     if feature.starts_with("+") {
2693                         let valid = whitelist.contains_key(&feature[1..]);
2694                         if valid {
2695                             err.help("consider removing the leading `+` in the feature name");
2696                         }
2697                     }
2698                     err.emit();
2699                     return None;
2700                 }
2701             };
2702
2703             // Only allow features whose feature gates have been enabled.
2704             let allowed = match feature_gate.as_ref().map(|s| *s) {
2705                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2706                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2707                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2708                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2709                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2710                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2711                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2712                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2713                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2714                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2715                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2716                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2717                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2718                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2719                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2720                 Some(name) => bug!("unknown target feature gate {}", name),
2721                 None => true,
2722             };
2723             if !allowed && id.is_local() {
2724                 feature_err(
2725                     &tcx.sess.parse_sess,
2726                     feature_gate.unwrap(),
2727                     item.span(),
2728                     &format!("the target feature `{}` is currently unstable", feature),
2729                 )
2730                 .emit();
2731             }
2732             Some(Symbol::intern(feature))
2733         }));
2734     }
2735 }
2736
2737 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2738     use rustc::mir::mono::Linkage::*;
2739
2740     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2741     // applicable to variable declarations and may not really make sense for
2742     // Rust code in the first place but whitelist them anyway and trust that
2743     // the user knows what s/he's doing. Who knows, unanticipated use cases
2744     // may pop up in the future.
2745     //
2746     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2747     // and don't have to be, LLVM treats them as no-ops.
2748     match name {
2749         "appending" => Appending,
2750         "available_externally" => AvailableExternally,
2751         "common" => Common,
2752         "extern_weak" => ExternalWeak,
2753         "external" => External,
2754         "internal" => Internal,
2755         "linkonce" => LinkOnceAny,
2756         "linkonce_odr" => LinkOnceODR,
2757         "private" => Private,
2758         "weak" => WeakAny,
2759         "weak_odr" => WeakODR,
2760         _ => {
2761             let span = tcx.hir().span_if_local(def_id);
2762             if let Some(span) = span {
2763                 tcx.sess.span_fatal(span, "invalid linkage specified")
2764             } else {
2765                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2766             }
2767         }
2768     }
2769 }
2770
2771 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2772     let attrs = tcx.get_attrs(id);
2773
2774     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2775
2776     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2777
2778     let mut inline_span = None;
2779     let mut link_ordinal_span = None;
2780     let mut no_sanitize_span = None;
2781     for attr in attrs.iter() {
2782         if attr.check_name(sym::cold) {
2783             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2784         } else if attr.check_name(sym::rustc_allocator) {
2785             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2786         } else if attr.check_name(sym::unwind) {
2787             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2788         } else if attr.check_name(sym::ffi_returns_twice) {
2789             if tcx.is_foreign_item(id) {
2790                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2791             } else {
2792                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2793                 struct_span_err!(
2794                     tcx.sess,
2795                     attr.span,
2796                     E0724,
2797                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2798                 )
2799                 .emit();
2800             }
2801         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2802             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2803         } else if attr.check_name(sym::naked) {
2804             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2805         } else if attr.check_name(sym::no_mangle) {
2806             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2807         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2808             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2809         } else if attr.check_name(sym::no_debug) {
2810             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2811         } else if attr.check_name(sym::used) {
2812             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2813         } else if attr.check_name(sym::thread_local) {
2814             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2815         } else if attr.check_name(sym::track_caller) {
2816             if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2817                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2818                     .emit();
2819             }
2820             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2821         } else if attr.check_name(sym::export_name) {
2822             if let Some(s) = attr.value_str() {
2823                 if s.as_str().contains("\0") {
2824                     // `#[export_name = ...]` will be converted to a null-terminated string,
2825                     // so it may not contain any null characters.
2826                     struct_span_err!(
2827                         tcx.sess,
2828                         attr.span,
2829                         E0648,
2830                         "`export_name` may not contain null characters"
2831                     )
2832                     .emit();
2833                 }
2834                 codegen_fn_attrs.export_name = Some(s);
2835             }
2836         } else if attr.check_name(sym::target_feature) {
2837             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2838                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2839                 tcx.sess
2840                     .struct_span_err(attr.span, msg)
2841                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2842                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2843                     .emit();
2844             }
2845             from_target_feature(tcx, id, attr, &whitelist, &mut codegen_fn_attrs.target_features);
2846         } else if attr.check_name(sym::linkage) {
2847             if let Some(val) = attr.value_str() {
2848                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2849             }
2850         } else if attr.check_name(sym::link_section) {
2851             if let Some(val) = attr.value_str() {
2852                 if val.as_str().bytes().any(|b| b == 0) {
2853                     let msg = format!(
2854                         "illegal null byte in link_section \
2855                          value: `{}`",
2856                         &val
2857                     );
2858                     tcx.sess.span_err(attr.span, &msg);
2859                 } else {
2860                     codegen_fn_attrs.link_section = Some(val);
2861                 }
2862             }
2863         } else if attr.check_name(sym::link_name) {
2864             codegen_fn_attrs.link_name = attr.value_str();
2865         } else if attr.check_name(sym::link_ordinal) {
2866             link_ordinal_span = Some(attr.span);
2867             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2868                 codegen_fn_attrs.link_ordinal = ordinal;
2869             }
2870         } else if attr.check_name(sym::no_sanitize) {
2871             no_sanitize_span = Some(attr.span);
2872             if let Some(list) = attr.meta_item_list() {
2873                 for item in list.iter() {
2874                     if item.check_name(sym::address) {
2875                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_ADDRESS;
2876                     } else if item.check_name(sym::memory) {
2877                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_MEMORY;
2878                     } else if item.check_name(sym::thread) {
2879                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_THREAD;
2880                     } else {
2881                         tcx.sess
2882                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2883                             .note("expected one of: `address`, `memory` or `thread`")
2884                             .emit();
2885                     }
2886                 }
2887             }
2888         }
2889     }
2890
2891     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2892         if !attr.has_name(sym::inline) {
2893             return ia;
2894         }
2895         match attr.meta().map(|i| i.kind) {
2896             Some(MetaItemKind::Word) => {
2897                 mark_used(attr);
2898                 InlineAttr::Hint
2899             }
2900             Some(MetaItemKind::List(ref items)) => {
2901                 mark_used(attr);
2902                 inline_span = Some(attr.span);
2903                 if items.len() != 1 {
2904                     struct_span_err!(
2905                         tcx.sess.diagnostic(),
2906                         attr.span,
2907                         E0534,
2908                         "expected one argument"
2909                     )
2910                     .emit();
2911                     InlineAttr::None
2912                 } else if list_contains_name(&items[..], sym::always) {
2913                     InlineAttr::Always
2914                 } else if list_contains_name(&items[..], sym::never) {
2915                     InlineAttr::Never
2916                 } else {
2917                     struct_span_err!(
2918                         tcx.sess.diagnostic(),
2919                         items[0].span(),
2920                         E0535,
2921                         "invalid argument"
2922                     )
2923                     .emit();
2924
2925                     InlineAttr::None
2926                 }
2927             }
2928             Some(MetaItemKind::NameValue(_)) => ia,
2929             None => ia,
2930         }
2931     });
2932
2933     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2934         if !attr.has_name(sym::optimize) {
2935             return ia;
2936         }
2937         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2938         match attr.meta().map(|i| i.kind) {
2939             Some(MetaItemKind::Word) => {
2940                 err(attr.span, "expected one argument");
2941                 ia
2942             }
2943             Some(MetaItemKind::List(ref items)) => {
2944                 mark_used(attr);
2945                 inline_span = Some(attr.span);
2946                 if items.len() != 1 {
2947                     err(attr.span, "expected one argument");
2948                     OptimizeAttr::None
2949                 } else if list_contains_name(&items[..], sym::size) {
2950                     OptimizeAttr::Size
2951                 } else if list_contains_name(&items[..], sym::speed) {
2952                     OptimizeAttr::Speed
2953                 } else {
2954                     err(items[0].span(), "invalid argument");
2955                     OptimizeAttr::None
2956                 }
2957             }
2958             Some(MetaItemKind::NameValue(_)) => ia,
2959             None => ia,
2960         }
2961     });
2962
2963     // If a function uses #[target_feature] it can't be inlined into general
2964     // purpose functions as they wouldn't have the right target features
2965     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2966     // respected.
2967     if codegen_fn_attrs.target_features.len() > 0 {
2968         if codegen_fn_attrs.inline == InlineAttr::Always {
2969             if let Some(span) = inline_span {
2970                 tcx.sess.span_err(
2971                     span,
2972                     "cannot use `#[inline(always)]` with \
2973                      `#[target_feature]`",
2974                 );
2975             }
2976         }
2977     }
2978
2979     if codegen_fn_attrs.flags.intersects(CodegenFnAttrFlags::NO_SANITIZE_ANY) {
2980         if codegen_fn_attrs.inline == InlineAttr::Always {
2981             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2982                 let hir_id = tcx.hir().as_local_hir_id(id).unwrap();
2983                 tcx.struct_span_lint_hir(
2984                     lint::builtin::INLINE_NO_SANITIZE,
2985                     hir_id,
2986                     no_sanitize_span,
2987                     "`no_sanitize` will have no effect after inlining",
2988                 )
2989                 .span_note(inline_span, "inlining requested here")
2990                 .emit();
2991             }
2992         }
2993     }
2994
2995     // Weak lang items have the same semantics as "std internal" symbols in the
2996     // sense that they're preserved through all our LTO passes and only
2997     // strippable by the linker.
2998     //
2999     // Additionally weak lang items have predetermined symbol names.
3000     if tcx.is_weak_lang_item(id) {
3001         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3002     }
3003     if let Some(name) = weak_lang_items::link_name(&attrs) {
3004         codegen_fn_attrs.export_name = Some(name);
3005         codegen_fn_attrs.link_name = Some(name);
3006     }
3007     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3008
3009     // Internal symbols to the standard library all have no_mangle semantics in
3010     // that they have defined symbol names present in the function name. This
3011     // also applies to weak symbols where they all have known symbol names.
3012     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3013         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3014     }
3015
3016     codegen_fn_attrs
3017 }
3018
3019 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
3020     use syntax::ast::{Lit, LitIntType, LitKind};
3021     let meta_item_list = attr.meta_item_list();
3022     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3023     let sole_meta_list = match meta_item_list {
3024         Some([item]) => item.literal(),
3025         _ => None,
3026     };
3027     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3028         if *ordinal <= std::usize::MAX as u128 {
3029             Some(*ordinal as usize)
3030         } else {
3031             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3032             tcx.sess
3033                 .struct_span_err(attr.span, &msg)
3034                 .note("the value may not exceed `std::usize::MAX`")
3035                 .emit();
3036             None
3037         }
3038     } else {
3039         tcx.sess
3040             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3041             .note("an unsuffixed integer value, e.g., `1`, is expected")
3042             .emit();
3043         None
3044     }
3045 }
3046
3047 fn check_link_name_xor_ordinal(
3048     tcx: TyCtxt<'_>,
3049     codegen_fn_attrs: &CodegenFnAttrs,
3050     inline_span: Option<Span>,
3051 ) {
3052     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3053         return;
3054     }
3055     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3056     if let Some(span) = inline_span {
3057         tcx.sess.span_err(span, msg);
3058     } else {
3059         tcx.sess.err(msg);
3060     }
3061 }