src/librustc_typeck/collect.rs

   1 // ignore-tidy-filelength
   2
   3 //! "Collection" is the process of determining the type and other external
   4 //! details of each item in Rust. Collection is specifically concerned
   5 //! with *inter-procedural* things -- for example, for a function
   6 //! definition, collection will figure out the type and signature of the
   7 //! function, but it will not visit the *body* of the function in any way,
   8 //! nor examine type annotations on local variables (that's the job of
   9 //! type *checking*).
  10 //!
  11 //! Collecting is ultimately defined by a bundle of queries that
  12 //! inquire after various facts about the items in the crate (e.g.,
  13 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  14 //! for the full set.
  15 //!
  16 //! At present, however, we do run collection across all items in the
  17 //! crate as a kind of pass. This should eventually be factored away.
  18
  19 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::lint;
  23 use crate::middle::lang_items;
  24 use crate::middle::resolve_lifetime as rl;
  25 use rustc::hir::map::blocks::FnLikeNode;
  26 use rustc::hir::map::Map;
  27 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  28 use rustc::mir::mono::Linkage;
  29 use rustc::session::parse::feature_err;
  30 use rustc::traits;
  31 use rustc::ty::query::Providers;
  32 use rustc::ty::subst::GenericArgKind;
  33 use rustc::ty::subst::{InternalSubsts, Subst};
  34 use rustc::ty::util::Discr;
  35 use rustc::ty::util::IntTypeExt;
  36 use rustc::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt, WithConstness};
  37 use rustc::ty::{ReprOptions, ToPredicate};
  38 use rustc_attr::{list_contains_name, mark_used, InlineAttr, OptimizeAttr};
  39 use rustc_data_structures::captures::Captures;
  40 use rustc_data_structures::fx::FxHashMap;
  41 use rustc_errors::{struct_span_err, Applicability, StashKey};
  42 use rustc_hir as hir;
  43 use rustc_hir::def::{CtorKind, DefKind, Res};
  44 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
  45 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
  46 use rustc_hir::{GenericParamKind, Node, Unsafety};
  47 use rustc_span::symbol::{kw, sym, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::abi;
  50 use syntax::ast;
  51 use syntax::ast::{Ident, MetaItemKind};
  52
  53 struct OnlySelfBounds(bool);
  54
  55 ///////////////////////////////////////////////////////////////////////////
  56 // Main entry point
  57
  58 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
  59     tcx.hir().visit_item_likes_in_module(
  60         module_def_id,
  61         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  62     );
  63 }
  64
  65 pub fn provide(providers: &mut Providers<'_>) {
  66     *providers = Providers {
  67         type_of,
  68         generics_of,
  69         predicates_of,
  70         predicates_defined_on,
  71         explicit_predicates_of,
  72         super_predicates_of,
  73         type_param_predicates,
  74         trait_def,
  75         adt_def,
  76         fn_sig,
  77         impl_trait_ref,
  78         impl_polarity,
  79         is_foreign_item,
  80         static_mutability,
  81         codegen_fn_attrs,
  82         collect_mod_item_types,
  83         ..*providers
  84     };
  85 }
  86
  87 ///////////////////////////////////////////////////////////////////////////
  88
  89 /// Context specific to some particular item. This is what implements
  90 /// `AstConv`. It has information about the predicates that are defined
  91 /// on the trait. Unfortunately, this predicate information is
  92 /// available in various different forms at various points in the
  93 /// process. So we can't just store a pointer to e.g., the AST or the
  94 /// parsed ty form, we have to be more flexible. To this end, the
  95 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  96 /// `get_type_parameter_bounds` requests, drawing the information from
  97 /// the AST (`hir::Generics`), recursively.
  98 pub struct ItemCtxt<'tcx> {
  99     tcx: TyCtxt<'tcx>,
 100     item_def_id: DefId,
 101 }
 102
 103 ///////////////////////////////////////////////////////////////////////////
 104
 105 #[derive(Default)]
 106 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 107
 108 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 109     type Map = Map<'v>;
 110
 111     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 112         NestedVisitorMap::None
 113     }
 114     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 115         if let hir::TyKind::Infer = t.kind {
 116             self.0.push(t.span);
 117         }
 118         intravisit::walk_ty(self, t)
 119     }
 120 }
 121
 122 struct CollectItemTypesVisitor<'tcx> {
 123     tcx: TyCtxt<'tcx>,
 124 }
 125
 126 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 127 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 128 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 129 crate fn placeholder_type_error(
 130     tcx: TyCtxt<'tcx>,
 131     span: Span,
 132     generics: &[hir::GenericParam<'_>],
 133     placeholder_types: Vec<Span>,
 134     suggest: bool,
 135 ) {
 136     if placeholder_types.is_empty() {
 137         return;
 138     }
 139     // This is the whitelist of possible parameter names that we might suggest.
 140     let possible_names = ["T", "K", "L", "A", "B", "C"];
 141     let used_names = generics
 142         .iter()
 143         .filter_map(|p| match p.name {
 144             hir::ParamName::Plain(ident) => Some(ident.name),
 145             _ => None,
 146         })
 147         .collect::<Vec<_>>();
 148
 149     let type_name = possible_names
 150         .iter()
 151         .find(|n| !used_names.contains(&Symbol::intern(n)))
 152         .unwrap_or(&"ParamName");
 153
 154     let mut sugg: Vec<_> =
 155         placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
 156     if generics.is_empty() {
 157         sugg.push((span, format!("<{}>", type_name)));
 158     } else if let Some(arg) = generics.iter().find(|arg| match arg.name {
 159         hir::ParamName::Plain(Ident { name: kw::Underscore, .. }) => true,
 160         _ => false,
 161     }) {
 162         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 163         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 164         sugg.push((arg.span, format!("{}", type_name)));
 165     } else {
 166         sugg.push((
 167             generics.iter().last().unwrap().span.shrink_to_hi(),
 168             format!(", {}", type_name),
 169         ));
 170     }
 171     let mut err = bad_placeholder_type(tcx, placeholder_types);
 172     if suggest {
 173         err.multipart_suggestion(
 174             "use type parameters instead",
 175             sugg,
 176             Applicability::HasPlaceholders,
 177         );
 178     }
 179     err.emit();
 180 }
 181
 182 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 183     let (generics, suggest) = match &item.kind {
 184         hir::ItemKind::Union(_, generics)
 185         | hir::ItemKind::Enum(_, generics)
 186         | hir::ItemKind::TraitAlias(generics, _)
 187         | hir::ItemKind::Trait(_, _, generics, ..)
 188         | hir::ItemKind::Impl { generics, .. }
 189         | hir::ItemKind::Struct(_, generics) => (generics, true),
 190         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 191         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 192         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 193         _ => return,
 194     };
 195
 196     let mut visitor = PlaceholderHirTyCollector::default();
 197     visitor.visit_item(item);
 198
 199     placeholder_type_error(tcx, generics.span, &generics.params[..], visitor.0, suggest);
 200 }
 201
 202 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 203     type Map = Map<'tcx>;
 204
 205     fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 206         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 207     }
 208
 209     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 210         convert_item(self.tcx, item.hir_id);
 211         reject_placeholder_type_signatures_in_item(self.tcx, item);
 212         intravisit::walk_item(self, item);
 213     }
 214
 215     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 216         for param in generics.params {
 217             match param.kind {
 218                 hir::GenericParamKind::Lifetime { .. } => {}
 219                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 220                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 221                     self.tcx.type_of(def_id);
 222                 }
 223                 hir::GenericParamKind::Type { .. } => {}
 224                 hir::GenericParamKind::Const { .. } => {
 225                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 226                     self.tcx.type_of(def_id);
 227                 }
 228             }
 229         }
 230         intravisit::walk_generics(self, generics);
 231     }
 232
 233     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 234         if let hir::ExprKind::Closure(..) = expr.kind {
 235             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 236             self.tcx.generics_of(def_id);
 237             self.tcx.type_of(def_id);
 238         }
 239         intravisit::walk_expr(self, expr);
 240     }
 241
 242     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 243         convert_trait_item(self.tcx, trait_item.hir_id);
 244         intravisit::walk_trait_item(self, trait_item);
 245     }
 246
 247     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 248         convert_impl_item(self.tcx, impl_item.hir_id);
 249         intravisit::walk_impl_item(self, impl_item);
 250     }
 251 }
 252
 253 ///////////////////////////////////////////////////////////////////////////
 254 // Utility types and common code for the above passes.
 255
 256 fn bad_placeholder_type(
 257     tcx: TyCtxt<'tcx>,
 258     mut spans: Vec<Span>,
 259 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 260     spans.sort();
 261     let mut err = struct_span_err!(
 262         tcx.sess,
 263         spans.clone(),
 264         E0121,
 265         "the type placeholder `_` is not allowed within types on item signatures",
 266     );
 267     for span in spans {
 268         err.span_label(span, "not allowed in type signatures");
 269     }
 270     err
 271 }
 272
 273 impl ItemCtxt<'tcx> {
 274     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 275         ItemCtxt { tcx, item_def_id }
 276     }
 277
 278     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 279         AstConv::ast_ty_to_ty(self, ast_ty)
 280     }
 281
 282     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(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 368                     let item =
 369                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 370                     match &item.kind {
 371                         hir::ItemKind::Enum(_, generics)
 372                         | hir::ItemKind::Struct(_, generics)
 373                         | hir::ItemKind::Union(_, generics) => {
 374                             // FIXME: look for an appropriate lt name if `'a` is already used
 375                             let (lt_sp, sugg) = match &generics.params[..] {
 376                                 [] => (generics.span, "<'a>".to_string()),
 377                                 [bound, ..] => (bound.span.shrink_to_lo(), "'a, ".to_string()),
 378                             };
 379                             let suggestions = vec![
 380                                 (lt_sp, sugg),
 381                                 (
 382                                     span,
 383                                     format!(
 384                                         "{}::{}",
 385                                         // Replace the existing lifetimes with a new named lifetime.
 386                                         self.tcx
 387                                             .replace_late_bound_regions(&poly_trait_ref, |_| {
 388                                                 self.tcx.mk_region(ty::ReEarlyBound(
 389                                                     ty::EarlyBoundRegion {
 390                                                         def_id: item_def_id,
 391                                                         index: 0,
 392                                                         name: Symbol::intern("'a"),
 393                                                     },
 394                                                 ))
 395                                             })
 396                                             .0,
 397                                         item_segment.ident
 398                                     ),
 399                                 ),
 400                             ];
 401                             err.multipart_suggestion(
 402                                 "use a fully qualified path with explicit lifetimes",
 403                                 suggestions,
 404                                 Applicability::MaybeIncorrect,
 405                             );
 406                         }
 407                         _ => {}
 408                     }
 409                 }
 410                 hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..), .. })
 411                 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(..), .. })
 412                 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(..), .. }) => {}
 413                 hir::Node::Item(_)
 414                 | hir::Node::ForeignItem(_)
 415                 | hir::Node::TraitItem(_)
 416                 | hir::Node::ImplItem(_) => {
 417                     err.span_suggestion(
 418                         span,
 419                         "use a fully qualified path with inferred lifetimes",
 420                         format!(
 421                             "{}::{}",
 422                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 423                             self.tcx.anonymize_late_bound_regions(&poly_trait_ref).skip_binder(),
 424                             item_segment.ident
 425                         ),
 426                         Applicability::MaybeIncorrect,
 427                     );
 428                 }
 429                 _ => {}
 430             }
 431             err.emit();
 432             self.tcx().types.err
 433         }
 434     }
 435
 436     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 437         // Types in item signatures are not normalized to avoid undue dependencies.
 438         ty
 439     }
 440
 441     fn set_tainted_by_errors(&self) {
 442         // There's no obvious place to track this, so just let it go.
 443     }
 444
 445     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 446         // There's no place to record types from signatures?
 447     }
 448 }
 449
 450 /// Returns the predicates defined on `item_def_id` of the form
 451 /// `X: Foo` where `X` is the type parameter `def_id`.
 452 fn type_param_predicates(
 453     tcx: TyCtxt<'_>,
 454     (item_def_id, def_id): (DefId, DefId),
 455 ) -> ty::GenericPredicates<'_> {
 456     use rustc_hir::*;
 457
 458     // In the AST, bounds can derive from two places. Either
 459     // written inline like `<T: Foo>` or in a where-clause like
 460     // `where T: Foo`.
 461
 462     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 463     let param_owner = tcx.hir().ty_param_owner(param_id);
 464     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 465     let generics = tcx.generics_of(param_owner_def_id);
 466     let index = generics.param_def_id_to_index[&def_id];
 467     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 468
 469     // Don't look for bounds where the type parameter isn't in scope.
 470     let parent =
 471         if item_def_id == param_owner_def_id { None } else { tcx.generics_of(item_def_id).parent };
 472
 473     let mut result = parent
 474         .map(|parent| {
 475             let icx = ItemCtxt::new(tcx, parent);
 476             icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 477         })
 478         .unwrap_or_default();
 479     let mut extend = None;
 480
 481     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 482     let ast_generics = match tcx.hir().get(item_hir_id) {
 483         Node::TraitItem(item) => &item.generics,
 484
 485         Node::ImplItem(item) => &item.generics,
 486
 487         Node::Item(item) => {
 488             match item.kind {
 489                 ItemKind::Fn(.., ref generics, _)
 490                 | ItemKind::Impl { ref generics, .. }
 491                 | ItemKind::TyAlias(_, ref generics)
 492                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 493                 | ItemKind::Enum(_, ref generics)
 494                 | ItemKind::Struct(_, ref generics)
 495                 | ItemKind::Union(_, ref generics) => generics,
 496                 ItemKind::Trait(_, _, ref generics, ..) => {
 497                     // Implied `Self: Trait` and supertrait bounds.
 498                     if param_id == item_hir_id {
 499                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 500                         extend =
 501                             Some((identity_trait_ref.without_const().to_predicate(), item.span));
 502                     }
 503                     generics
 504                 }
 505                 _ => return result,
 506             }
 507         }
 508
 509         Node::ForeignItem(item) => match item.kind {
 510             ForeignItemKind::Fn(_, _, ref generics) => generics,
 511             _ => return result,
 512         },
 513
 514         _ => return result,
 515     };
 516
 517     let icx = ItemCtxt::new(tcx, item_def_id);
 518     let extra_predicates = extend.into_iter().chain(
 519         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 520             .into_iter()
 521             .filter(|(predicate, _)| match predicate {
 522                 ty::Predicate::Trait(ref data, _) => data.skip_binder().self_ty().is_param(index),
 523                 _ => false,
 524             }),
 525     );
 526     result.predicates =
 527         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 528     result
 529 }
 530
 531 impl ItemCtxt<'tcx> {
 532     /// Finds bounds from `hir::Generics`. This requires scanning through the
 533     /// AST. We do this to avoid having to convert *all* the bounds, which
 534     /// would create artificial cycles. Instead, we can only convert the
 535     /// bounds for a type parameter `X` if `X::Foo` is used.
 536     fn type_parameter_bounds_in_generics(
 537         &self,
 538         ast_generics: &'tcx hir::Generics<'tcx>,
 539         param_id: hir::HirId,
 540         ty: Ty<'tcx>,
 541         only_self_bounds: OnlySelfBounds,
 542     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 543         let constness = self.default_constness_for_trait_bounds();
 544         let from_ty_params = ast_generics
 545             .params
 546             .iter()
 547             .filter_map(|param| match param.kind {
 548                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 549                 _ => None,
 550             })
 551             .flat_map(|bounds| bounds.iter())
 552             .flat_map(|b| predicates_from_bound(self, ty, b, constness));
 553
 554         let from_where_clauses = ast_generics
 555             .where_clause
 556             .predicates
 557             .iter()
 558             .filter_map(|wp| match *wp {
 559                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 560                 _ => None,
 561             })
 562             .flat_map(|bp| {
 563                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 564                     Some(ty)
 565                 } else if !only_self_bounds.0 {
 566                     Some(self.to_ty(&bp.bounded_ty))
 567                 } else {
 568                     None
 569                 };
 570                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 571             })
 572             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b, constness));
 573
 574         from_ty_params.chain(from_where_clauses).collect()
 575     }
 576 }
 577
 578 /// Tests whether this is the AST for a reference to the type
 579 /// parameter with ID `param_id`. We use this so as to avoid running
 580 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 581 /// conversion of the type to avoid inducing unnecessary cycles.
 582 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 583     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 584         match path.res {
 585             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 586                 def_id == tcx.hir().local_def_id(param_id)
 587             }
 588             _ => false,
 589         }
 590     } else {
 591         false
 592     }
 593 }
 594
 595 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 596     let it = tcx.hir().expect_item(item_id);
 597     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 598     let def_id = tcx.hir().local_def_id(item_id);
 599     match it.kind {
 600         // These don't define types.
 601         hir::ItemKind::ExternCrate(_)
 602         | hir::ItemKind::Use(..)
 603         | hir::ItemKind::Mod(_)
 604         | hir::ItemKind::GlobalAsm(_) => {}
 605         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 606             for item in foreign_mod.items {
 607                 let def_id = tcx.hir().local_def_id(item.hir_id);
 608                 tcx.generics_of(def_id);
 609                 tcx.type_of(def_id);
 610                 tcx.predicates_of(def_id);
 611                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 612                     tcx.fn_sig(def_id);
 613                 }
 614             }
 615         }
 616         hir::ItemKind::Enum(ref enum_definition, _) => {
 617             tcx.generics_of(def_id);
 618             tcx.type_of(def_id);
 619             tcx.predicates_of(def_id);
 620             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 621         }
 622         hir::ItemKind::Impl { .. } => {
 623             tcx.generics_of(def_id);
 624             tcx.type_of(def_id);
 625             tcx.impl_trait_ref(def_id);
 626             tcx.predicates_of(def_id);
 627         }
 628         hir::ItemKind::Trait(..) => {
 629             tcx.generics_of(def_id);
 630             tcx.trait_def(def_id);
 631             tcx.at(it.span).super_predicates_of(def_id);
 632             tcx.predicates_of(def_id);
 633         }
 634         hir::ItemKind::TraitAlias(..) => {
 635             tcx.generics_of(def_id);
 636             tcx.at(it.span).super_predicates_of(def_id);
 637             tcx.predicates_of(def_id);
 638         }
 639         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 640             tcx.generics_of(def_id);
 641             tcx.type_of(def_id);
 642             tcx.predicates_of(def_id);
 643
 644             for f in struct_def.fields() {
 645                 let def_id = tcx.hir().local_def_id(f.hir_id);
 646                 tcx.generics_of(def_id);
 647                 tcx.type_of(def_id);
 648                 tcx.predicates_of(def_id);
 649             }
 650
 651             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 652                 convert_variant_ctor(tcx, ctor_hir_id);
 653             }
 654         }
 655
 656         // Desugared from `impl Trait`, so visited by the function's return type.
 657         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 658
 659         hir::ItemKind::OpaqueTy(..)
 660         | hir::ItemKind::TyAlias(..)
 661         | hir::ItemKind::Static(..)
 662         | hir::ItemKind::Const(..)
 663         | hir::ItemKind::Fn(..) => {
 664             tcx.generics_of(def_id);
 665             tcx.type_of(def_id);
 666             tcx.predicates_of(def_id);
 667             if let hir::ItemKind::Fn(..) = it.kind {
 668                 tcx.fn_sig(def_id);
 669             }
 670         }
 671     }
 672 }
 673
 674 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 675     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 676     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 677     tcx.generics_of(def_id);
 678
 679     match trait_item.kind {
 680         hir::TraitItemKind::Const(..)
 681         | hir::TraitItemKind::Type(_, Some(_))
 682         | hir::TraitItemKind::Method(..) => {
 683             tcx.type_of(def_id);
 684             if let hir::TraitItemKind::Method(..) = trait_item.kind {
 685                 tcx.fn_sig(def_id);
 686             }
 687         }
 688
 689         hir::TraitItemKind::Type(_, None) => {}
 690     };
 691
 692     tcx.predicates_of(def_id);
 693 }
 694
 695 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 696     let def_id = tcx.hir().local_def_id(impl_item_id);
 697     tcx.generics_of(def_id);
 698     tcx.type_of(def_id);
 699     tcx.predicates_of(def_id);
 700     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
 701         tcx.fn_sig(def_id);
 702     }
 703 }
 704
 705 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 706     let def_id = tcx.hir().local_def_id(ctor_id);
 707     tcx.generics_of(def_id);
 708     tcx.type_of(def_id);
 709     tcx.predicates_of(def_id);
 710 }
 711
 712 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 713     let def = tcx.adt_def(def_id);
 714     let repr_type = def.repr.discr_type();
 715     let initial = repr_type.initial_discriminant(tcx);
 716     let mut prev_discr = None::<Discr<'_>>;
 717
 718     // fill the discriminant values and field types
 719     for variant in variants {
 720         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 721         prev_discr = Some(
 722             if let Some(ref e) = variant.disr_expr {
 723                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 724                 def.eval_explicit_discr(tcx, expr_did)
 725             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 726                 Some(discr)
 727             } else {
 728                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 729                     .span_label(
 730                         variant.span,
 731                         format!("overflowed on value after {}", prev_discr.unwrap()),
 732                     )
 733                     .note(&format!(
 734                         "explicitly set `{} = {}` if that is desired outcome",
 735                         variant.ident, wrapped_discr
 736                     ))
 737                     .emit();
 738                 None
 739             }
 740             .unwrap_or(wrapped_discr),
 741         );
 742
 743         for f in variant.data.fields() {
 744             let def_id = tcx.hir().local_def_id(f.hir_id);
 745             tcx.generics_of(def_id);
 746             tcx.type_of(def_id);
 747             tcx.predicates_of(def_id);
 748         }
 749
 750         // Convert the ctor, if any. This also registers the variant as
 751         // an item.
 752         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 753             convert_variant_ctor(tcx, ctor_hir_id);
 754         }
 755     }
 756 }
 757
 758 fn convert_variant(
 759     tcx: TyCtxt<'_>,
 760     variant_did: Option<DefId>,
 761     ctor_did: Option<DefId>,
 762     ident: Ident,
 763     discr: ty::VariantDiscr,
 764     def: &hir::VariantData<'_>,
 765     adt_kind: ty::AdtKind,
 766     parent_did: DefId,
 767 ) -> ty::VariantDef {
 768     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 769     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 770     let fields = def
 771         .fields()
 772         .iter()
 773         .map(|f| {
 774             let fid = tcx.hir().local_def_id(f.hir_id);
 775             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 776             if let Some(prev_span) = dup_span {
 777                 struct_span_err!(
 778                     tcx.sess,
 779                     f.span,
 780                     E0124,
 781                     "field `{}` is already declared",
 782                     f.ident
 783                 )
 784                 .span_label(f.span, "field already declared")
 785                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 786                 .emit();
 787             } else {
 788                 seen_fields.insert(f.ident.modern(), f.span);
 789             }
 790
 791             ty::FieldDef {
 792                 did: fid,
 793                 ident: f.ident,
 794                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 795             }
 796         })
 797         .collect();
 798     let recovered = match def {
 799         hir::VariantData::Struct(_, r) => *r,
 800         _ => false,
 801     };
 802     ty::VariantDef::new(
 803         tcx,
 804         ident,
 805         variant_did,
 806         ctor_did,
 807         discr,
 808         fields,
 809         CtorKind::from_hir(def),
 810         adt_kind,
 811         parent_did,
 812         recovered,
 813     )
 814 }
 815
 816 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 817     use rustc_hir::*;
 818
 819     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 820     let item = match tcx.hir().get(hir_id) {
 821         Node::Item(item) => item,
 822         _ => bug!(),
 823     };
 824
 825     let repr = ReprOptions::new(tcx, def_id);
 826     let (kind, variants) = match item.kind {
 827         ItemKind::Enum(ref def, _) => {
 828             let mut distance_from_explicit = 0;
 829             let variants = def
 830                 .variants
 831                 .iter()
 832                 .map(|v| {
 833                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 834                     let ctor_did =
 835                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 836
 837                     let discr = if let Some(ref e) = v.disr_expr {
 838                         distance_from_explicit = 0;
 839                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 840                     } else {
 841                         ty::VariantDiscr::Relative(distance_from_explicit)
 842                     };
 843                     distance_from_explicit += 1;
 844
 845                     convert_variant(
 846                         tcx,
 847                         variant_did,
 848                         ctor_did,
 849                         v.ident,
 850                         discr,
 851                         &v.data,
 852                         AdtKind::Enum,
 853                         def_id,
 854                     )
 855                 })
 856                 .collect();
 857
 858             (AdtKind::Enum, variants)
 859         }
 860         ItemKind::Struct(ref def, _) => {
 861             let variant_did = None;
 862             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 863
 864             let variants = std::iter::once(convert_variant(
 865                 tcx,
 866                 variant_did,
 867                 ctor_did,
 868                 item.ident,
 869                 ty::VariantDiscr::Relative(0),
 870                 def,
 871                 AdtKind::Struct,
 872                 def_id,
 873             ))
 874             .collect();
 875
 876             (AdtKind::Struct, variants)
 877         }
 878         ItemKind::Union(ref def, _) => {
 879             let variant_did = None;
 880             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 881
 882             let variants = std::iter::once(convert_variant(
 883                 tcx,
 884                 variant_did,
 885                 ctor_did,
 886                 item.ident,
 887                 ty::VariantDiscr::Relative(0),
 888                 def,
 889                 AdtKind::Union,
 890                 def_id,
 891             ))
 892             .collect();
 893
 894             (AdtKind::Union, variants)
 895         }
 896         _ => bug!(),
 897     };
 898     tcx.alloc_adt_def(def_id, kind, variants, repr)
 899 }
 900
 901 /// Ensures that the super-predicates of the trait with a `DefId`
 902 /// of `trait_def_id` are converted and stored. This also ensures that
 903 /// the transitive super-predicates are converted.
 904 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 905     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 906     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 907
 908     let item = match tcx.hir().get(trait_hir_id) {
 909         Node::Item(item) => item,
 910         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 911     };
 912
 913     let (generics, bounds) = match item.kind {
 914         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 915         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 916         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 917     };
 918
 919     let icx = ItemCtxt::new(tcx, trait_def_id);
 920
 921     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 922     let self_param_ty = tcx.types.self_param;
 923     let superbounds1 =
 924         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 925
 926     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 927
 928     // Convert any explicit superbounds in the where-clause,
 929     // e.g., `trait Foo where Self: Bar`.
 930     // In the case of trait aliases, however, we include all bounds in the where-clause,
 931     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 932     // as one of its "superpredicates".
 933     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 934     let superbounds2 = icx.type_parameter_bounds_in_generics(
 935         generics,
 936         item.hir_id,
 937         self_param_ty,
 938         OnlySelfBounds(!is_trait_alias),
 939     );
 940
 941     // Combine the two lists to form the complete set of superbounds:
 942     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
 943
 944     // Now require that immediate supertraits are converted,
 945     // which will, in turn, reach indirect supertraits.
 946     for &(pred, span) in superbounds {
 947         debug!("superbound: {:?}", pred);
 948         if let ty::Predicate::Trait(bound, _) = pred {
 949             tcx.at(span).super_predicates_of(bound.def_id());
 950         }
 951     }
 952
 953     ty::GenericPredicates { parent: None, predicates: superbounds }
 954 }
 955
 956 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 957     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 958     let item = tcx.hir().expect_item(hir_id);
 959
 960     let (is_auto, unsafety) = match item.kind {
 961         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 962         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 963         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 964     };
 965
 966     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 967     if paren_sugar && !tcx.features().unboxed_closures {
 968         tcx.sess
 969             .struct_span_err(
 970                 item.span,
 971                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 972              which traits can use parenthetical notation",
 973             )
 974             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
 975             .emit();
 976     }
 977
 978     let is_marker = tcx.has_attr(def_id, sym::marker);
 979     let def_path_hash = tcx.def_path_hash(def_id);
 980     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 981     tcx.arena.alloc(def)
 982 }
 983
 984 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 985     struct LateBoundRegionsDetector<'tcx> {
 986         tcx: TyCtxt<'tcx>,
 987         outer_index: ty::DebruijnIndex,
 988         has_late_bound_regions: Option<Span>,
 989     }
 990
 991     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 992         type Map = Map<'tcx>;
 993
 994         fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
 995             NestedVisitorMap::None
 996         }
 997
 998         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
 999             if self.has_late_bound_regions.is_some() {
1000                 return;
1001             }
1002             match ty.kind {
1003                 hir::TyKind::BareFn(..) => {
1004                     self.outer_index.shift_in(1);
1005                     intravisit::walk_ty(self, ty);
1006                     self.outer_index.shift_out(1);
1007                 }
1008                 _ => intravisit::walk_ty(self, ty),
1009             }
1010         }
1011
1012         fn visit_poly_trait_ref(
1013             &mut self,
1014             tr: &'tcx hir::PolyTraitRef<'tcx>,
1015             m: hir::TraitBoundModifier,
1016         ) {
1017             if self.has_late_bound_regions.is_some() {
1018                 return;
1019             }
1020             self.outer_index.shift_in(1);
1021             intravisit::walk_poly_trait_ref(self, tr, m);
1022             self.outer_index.shift_out(1);
1023         }
1024
1025         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1026             if self.has_late_bound_regions.is_some() {
1027                 return;
1028             }
1029
1030             match self.tcx.named_region(lt.hir_id) {
1031                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
1032                 Some(rl::Region::LateBound(debruijn, _, _))
1033                 | Some(rl::Region::LateBoundAnon(debruijn, _))
1034                     if debruijn < self.outer_index => {}
1035                 Some(rl::Region::LateBound(..))
1036                 | Some(rl::Region::LateBoundAnon(..))
1037                 | Some(rl::Region::Free(..))
1038                 | None => {
1039                     self.has_late_bound_regions = Some(lt.span);
1040                 }
1041             }
1042         }
1043     }
1044
1045     fn has_late_bound_regions<'tcx>(
1046         tcx: TyCtxt<'tcx>,
1047         generics: &'tcx hir::Generics<'tcx>,
1048         decl: &'tcx hir::FnDecl<'tcx>,
1049     ) -> Option<Span> {
1050         let mut visitor = LateBoundRegionsDetector {
1051             tcx,
1052             outer_index: ty::INNERMOST,
1053             has_late_bound_regions: None,
1054         };
1055         for param in generics.params {
1056             if let GenericParamKind::Lifetime { .. } = param.kind {
1057                 if tcx.is_late_bound(param.hir_id) {
1058                     return Some(param.span);
1059                 }
1060             }
1061         }
1062         visitor.visit_fn_decl(decl);
1063         visitor.has_late_bound_regions
1064     }
1065
1066     match node {
1067         Node::TraitItem(item) => match item.kind {
1068             hir::TraitItemKind::Method(ref sig, _) => {
1069                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1070             }
1071             _ => None,
1072         },
1073         Node::ImplItem(item) => match item.kind {
1074             hir::ImplItemKind::Method(ref sig, _) => {
1075                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
1076             }
1077             _ => None,
1078         },
1079         Node::ForeignItem(item) => match item.kind {
1080             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
1081                 has_late_bound_regions(tcx, generics, fn_decl)
1082             }
1083             _ => None,
1084         },
1085         Node::Item(item) => match item.kind {
1086             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1087                 has_late_bound_regions(tcx, generics, &sig.decl)
1088             }
1089             _ => None,
1090         },
1091         _ => None,
1092     }
1093 }
1094
1095 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
1096     use rustc_hir::*;
1097
1098     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1099
1100     let node = tcx.hir().get(hir_id);
1101     let parent_def_id = match node {
1102         Node::ImplItem(_)
1103         | Node::TraitItem(_)
1104         | Node::Variant(_)
1105         | Node::Ctor(..)
1106         | Node::Field(_) => {
1107             let parent_id = tcx.hir().get_parent_item(hir_id);
1108             Some(tcx.hir().local_def_id(parent_id))
1109         }
1110         // FIXME(#43408) enable this always when we get lazy normalization.
1111         Node::AnonConst(_) => {
1112             // HACK(eddyb) this provides the correct generics when
1113             // `feature(const_generics)` is enabled, so that const expressions
1114             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1115             if tcx.features().const_generics {
1116                 let parent_id = tcx.hir().get_parent_item(hir_id);
1117                 Some(tcx.hir().local_def_id(parent_id))
1118             } else {
1119                 None
1120             }
1121         }
1122         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1123             Some(tcx.closure_base_def_id(def_id))
1124         }
1125         Node::Item(item) => match item.kind {
1126             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => {
1127                 impl_trait_fn.or_else(|| {
1128                     let parent_id = tcx.hir().get_parent_item(hir_id);
1129                     if parent_id != hir_id && parent_id != CRATE_HIR_ID {
1130                         debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1131                         // If this 'impl Trait' is nested inside another 'impl Trait'
1132                         // (e.g. `impl Foo<MyType = impl Bar<A>>`), we need to use the 'parent'
1133                         // 'impl Trait' for its generic parameters, since we can reference them
1134                         // from the 'child' 'impl Trait'
1135                         if let Node::Item(hir::Item { kind: ItemKind::OpaqueTy(..), .. }) =
1136                             tcx.hir().get(parent_id)
1137                         {
1138                             Some(tcx.hir().local_def_id(parent_id))
1139                         } else {
1140                             None
1141                         }
1142                     } else {
1143                         None
1144                     }
1145                 })
1146             }
1147             _ => None,
1148         },
1149         _ => None,
1150     };
1151
1152     let mut opt_self = None;
1153     let mut allow_defaults = false;
1154
1155     let no_generics = hir::Generics::empty();
1156     let ast_generics = match node {
1157         Node::TraitItem(item) => &item.generics,
1158
1159         Node::ImplItem(item) => &item.generics,
1160
1161         Node::Item(item) => {
1162             match item.kind {
1163                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl { ref generics, .. } => generics,
1164
1165                 ItemKind::TyAlias(_, ref generics)
1166                 | ItemKind::Enum(_, ref generics)
1167                 | ItemKind::Struct(_, ref generics)
1168                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1169                 | ItemKind::Union(_, ref generics) => {
1170                     allow_defaults = true;
1171                     generics
1172                 }
1173
1174                 ItemKind::Trait(_, _, ref generics, ..)
1175                 | ItemKind::TraitAlias(ref generics, ..) => {
1176                     // Add in the self type parameter.
1177                     //
1178                     // Something of a hack: use the node id for the trait, also as
1179                     // the node id for the Self type parameter.
1180                     let param_id = item.hir_id;
1181
1182                     opt_self = Some(ty::GenericParamDef {
1183                         index: 0,
1184                         name: kw::SelfUpper,
1185                         def_id: tcx.hir().local_def_id(param_id),
1186                         pure_wrt_drop: false,
1187                         kind: ty::GenericParamDefKind::Type {
1188                             has_default: false,
1189                             object_lifetime_default: rl::Set1::Empty,
1190                             synthetic: None,
1191                         },
1192                     });
1193
1194                     allow_defaults = true;
1195                     generics
1196                 }
1197
1198                 _ => &no_generics,
1199             }
1200         }
1201
1202         Node::ForeignItem(item) => match item.kind {
1203             ForeignItemKind::Static(..) => &no_generics,
1204             ForeignItemKind::Fn(_, _, ref generics) => generics,
1205             ForeignItemKind::Type => &no_generics,
1206         },
1207
1208         _ => &no_generics,
1209     };
1210
1211     let has_self = opt_self.is_some();
1212     let mut parent_has_self = false;
1213     let mut own_start = has_self as u32;
1214     let parent_count = parent_def_id.map_or(0, |def_id| {
1215         let generics = tcx.generics_of(def_id);
1216         assert_eq!(has_self, false);
1217         parent_has_self = generics.has_self;
1218         own_start = generics.count() as u32;
1219         generics.parent_count + generics.params.len()
1220     });
1221
1222     let mut params: Vec<_> = opt_self.into_iter().collect();
1223
1224     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1225     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1226         name: param.name.ident().name,
1227         index: own_start + i as u32,
1228         def_id: tcx.hir().local_def_id(param.hir_id),
1229         pure_wrt_drop: param.pure_wrt_drop,
1230         kind: ty::GenericParamDefKind::Lifetime,
1231     }));
1232
1233     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1234
1235     // Now create the real type parameters.
1236     let type_start = own_start - has_self as u32 + params.len() as u32;
1237     let mut i = 0;
1238     params.extend(ast_generics.params.iter().filter_map(|param| {
1239         let kind = match param.kind {
1240             GenericParamKind::Type { ref default, synthetic, .. } => {
1241                 if !allow_defaults && default.is_some() {
1242                     if !tcx.features().default_type_parameter_fallback {
1243                         tcx.struct_span_lint_hir(
1244                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1245                             param.hir_id,
1246                             param.span,
1247                             |lint| {
1248                                 lint.build(&format!(
1249                                     "defaults for type parameters are only allowed in \
1250                                         `struct`, `enum`, `type`, or `trait` definitions."
1251                                 ))
1252                                 .emit();
1253                             },
1254                         );
1255                     }
1256                 }
1257
1258                 ty::GenericParamDefKind::Type {
1259                     has_default: default.is_some(),
1260                     object_lifetime_default: object_lifetime_defaults
1261                         .as_ref()
1262                         .map_or(rl::Set1::Empty, |o| o[i]),
1263                     synthetic,
1264                 }
1265             }
1266             GenericParamKind::Const { .. } => ty::GenericParamDefKind::Const,
1267             _ => return None,
1268         };
1269
1270         let param_def = ty::GenericParamDef {
1271             index: type_start + i as u32,
1272             name: param.name.ident().name,
1273             def_id: tcx.hir().local_def_id(param.hir_id),
1274             pure_wrt_drop: param.pure_wrt_drop,
1275             kind,
1276         };
1277         i += 1;
1278         Some(param_def)
1279     }));
1280
1281     // provide junk type parameter defs - the only place that
1282     // cares about anything but the length is instantiation,
1283     // and we don't do that for closures.
1284     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1285         let dummy_args = if gen.is_some() {
1286             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>"][..]
1287         } else {
1288             &["<closure_kind>", "<closure_signature>"][..]
1289         };
1290
1291         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1292             index: type_start + i as u32,
1293             name: Symbol::intern(arg),
1294             def_id,
1295             pure_wrt_drop: false,
1296             kind: ty::GenericParamDefKind::Type {
1297                 has_default: false,
1298                 object_lifetime_default: rl::Set1::Empty,
1299                 synthetic: None,
1300             },
1301         }));
1302
1303         if let Some(upvars) = tcx.upvars(def_id) {
1304             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1305                 ty::GenericParamDef {
1306                     index: type_start + i,
1307                     name: Symbol::intern("<upvar>"),
1308                     def_id,
1309                     pure_wrt_drop: false,
1310                     kind: ty::GenericParamDefKind::Type {
1311                         has_default: false,
1312                         object_lifetime_default: rl::Set1::Empty,
1313                         synthetic: None,
1314                     },
1315                 }
1316             }));
1317         }
1318     }
1319
1320     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1321
1322     tcx.arena.alloc(ty::Generics {
1323         parent: parent_def_id,
1324         parent_count,
1325         params,
1326         param_def_id_to_index,
1327         has_self: has_self || parent_has_self,
1328         has_late_bound_regions: has_late_bound_regions(tcx, node),
1329     })
1330 }
1331
1332 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1333     struct_span_err!(
1334         tcx.sess,
1335         span,
1336         E0202,
1337         "associated types are not yet supported in inherent impls (see #8995)"
1338     )
1339     .emit();
1340 }
1341
1342 fn infer_placeholder_type(
1343     tcx: TyCtxt<'_>,
1344     def_id: DefId,
1345     body_id: hir::BodyId,
1346     span: Span,
1347     item_ident: Ident,
1348 ) -> Ty<'_> {
1349     let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
1350
1351     // If this came from a free `const` or `static mut?` item,
1352     // then the user may have written e.g. `const A = 42;`.
1353     // In this case, the parser has stashed a diagnostic for
1354     // us to improve in typeck so we do that now.
1355     match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1356         Some(mut err) => {
1357             // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1358             // We are typeck and have the real type, so remove that and suggest the actual type.
1359             err.suggestions.clear();
1360             err.span_suggestion(
1361                 span,
1362                 "provide a type for the item",
1363                 format!("{}: {}", item_ident, ty),
1364                 Applicability::MachineApplicable,
1365             )
1366             .emit();
1367         }
1368         None => {
1369             let mut diag = bad_placeholder_type(tcx, vec![span]);
1370             if ty != tcx.types.err {
1371                 diag.span_suggestion(
1372                     span,
1373                     "replace `_` with the correct type",
1374                     ty.to_string(),
1375                     Applicability::MaybeIncorrect,
1376                 );
1377             }
1378             diag.emit();
1379         }
1380     }
1381
1382     ty
1383 }
1384
1385 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1386     use rustc_hir::*;
1387
1388     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1389
1390     let icx = ItemCtxt::new(tcx, def_id);
1391
1392     match tcx.hir().get(hir_id) {
1393         Node::TraitItem(item) => match item.kind {
1394             TraitItemKind::Method(..) => {
1395                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1396                 tcx.mk_fn_def(def_id, substs)
1397             }
1398             TraitItemKind::Const(ref ty, body_id) => body_id
1399                 .and_then(|body_id| {
1400                     if is_suggestable_infer_ty(ty) {
1401                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1402                     } else {
1403                         None
1404                     }
1405                 })
1406                 .unwrap_or_else(|| icx.to_ty(ty)),
1407             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1408             TraitItemKind::Type(_, None) => {
1409                 span_bug!(item.span, "associated type missing default");
1410             }
1411         },
1412
1413         Node::ImplItem(item) => match item.kind {
1414             ImplItemKind::Method(..) => {
1415                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1416                 tcx.mk_fn_def(def_id, substs)
1417             }
1418             ImplItemKind::Const(ref ty, body_id) => {
1419                 if is_suggestable_infer_ty(ty) {
1420                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1421                 } else {
1422                     icx.to_ty(ty)
1423                 }
1424             }
1425             ImplItemKind::OpaqueTy(_) => {
1426                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1427                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1428                 }
1429
1430                 find_opaque_ty_constraints(tcx, def_id)
1431             }
1432             ImplItemKind::TyAlias(ref ty) => {
1433                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1434                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1435                 }
1436
1437                 icx.to_ty(ty)
1438             }
1439         },
1440
1441         Node::Item(item) => {
1442             match item.kind {
1443                 ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
1444                     if is_suggestable_infer_ty(ty) {
1445                         infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1446                     } else {
1447                         icx.to_ty(ty)
1448                     }
1449                 }
1450                 ItemKind::TyAlias(ref self_ty, _) | ItemKind::Impl { ref self_ty, .. } => {
1451                     icx.to_ty(self_ty)
1452                 }
1453                 ItemKind::Fn(..) => {
1454                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1455                     tcx.mk_fn_def(def_id, substs)
1456                 }
1457                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1458                     let def = tcx.adt_def(def_id);
1459                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1460                     tcx.mk_adt(def, substs)
1461                 }
1462                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
1463                     find_opaque_ty_constraints(tcx, def_id)
1464                 }
1465                 // Opaque types desugared from `impl Trait`.
1466                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
1467                     tcx.typeck_tables_of(owner)
1468                         .concrete_opaque_types
1469                         .get(&def_id)
1470                         .map(|opaque| opaque.concrete_type)
1471                         .unwrap_or_else(|| {
1472                             // This can occur if some error in the
1473                             // owner fn prevented us from populating
1474                             // the `concrete_opaque_types` table.
1475                             tcx.sess.delay_span_bug(
1476                                 DUMMY_SP,
1477                                 &format!(
1478                                     "owner {:?} has no opaque type for {:?} in its tables",
1479                                     owner, def_id,
1480                                 ),
1481                             );
1482                             tcx.types.err
1483                         })
1484                 }
1485                 ItemKind::Trait(..)
1486                 | ItemKind::TraitAlias(..)
1487                 | ItemKind::Mod(..)
1488                 | ItemKind::ForeignMod(..)
1489                 | ItemKind::GlobalAsm(..)
1490                 | ItemKind::ExternCrate(..)
1491                 | ItemKind::Use(..) => {
1492                     span_bug!(
1493                         item.span,
1494                         "compute_type_of_item: unexpected item type: {:?}",
1495                         item.kind
1496                     );
1497                 }
1498             }
1499         }
1500
1501         Node::ForeignItem(foreign_item) => match foreign_item.kind {
1502             ForeignItemKind::Fn(..) => {
1503                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1504                 tcx.mk_fn_def(def_id, substs)
1505             }
1506             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1507             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1508         },
1509
1510         Node::Ctor(&ref def) | Node::Variant(hir::Variant { data: ref def, .. }) => match *def {
1511             VariantData::Unit(..) | VariantData::Struct(..) => {
1512                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1513             }
1514             VariantData::Tuple(..) => {
1515                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1516                 tcx.mk_fn_def(def_id, substs)
1517             }
1518         },
1519
1520         Node::Field(field) => icx.to_ty(&field.ty),
1521
1522         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) => {
1523             if gen.is_some() {
1524                 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1525             }
1526
1527             let substs = InternalSubsts::identity_for_item(tcx, def_id);
1528             tcx.mk_closure(def_id, substs)
1529         }
1530
1531         Node::AnonConst(_) => {
1532             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1533             match parent_node {
1534                 Node::Ty(&hir::Ty { kind: hir::TyKind::Array(_, ref constant), .. })
1535                 | Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref constant), .. })
1536                 | Node::Expr(&hir::Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1537                     if constant.hir_id == hir_id =>
1538                 {
1539                     tcx.types.usize
1540                 }
1541
1542                 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
1543                     tcx.adt_def(tcx.hir().get_parent_did(hir_id)).repr.discr_type().to_ty(tcx)
1544                 }
1545
1546                 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. })
1547                 | Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. })
1548                 | Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. })
1549                 | Node::TraitRef(..) => {
1550                     let path = match parent_node {
1551                         Node::Ty(&hir::Ty {
1552                             kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1553                             ..
1554                         })
1555                         | Node::Expr(&hir::Expr {
1556                             kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1557                             ..
1558                         }) => Some(&**path),
1559                         Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1560                             if let QPath::Resolved(_, ref path) = **path {
1561                                 Some(&**path)
1562                             } else {
1563                                 None
1564                             }
1565                         }
1566                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1567                         _ => None,
1568                     };
1569
1570                     if let Some(path) = path {
1571                         let arg_index = path
1572                             .segments
1573                             .iter()
1574                             .filter_map(|seg| seg.args.as_ref())
1575                             .map(|generic_args| generic_args.args.as_ref())
1576                             .find_map(|args| {
1577                                 args.iter()
1578                                     .filter(|arg| arg.is_const())
1579                                     .enumerate()
1580                                     .filter(|(_, arg)| arg.id() == hir_id)
1581                                     .map(|(index, _)| index)
1582                                     .next()
1583                             })
1584                             .unwrap_or_else(|| {
1585                                 bug!("no arg matching AnonConst in path");
1586                             });
1587
1588                         // We've encountered an `AnonConst` in some path, so we need to
1589                         // figure out which generic parameter it corresponds to and return
1590                         // the relevant type.
1591                         let generics = match path.res {
1592                             Res::Def(DefKind::Ctor(..), def_id) => {
1593                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1594                             }
1595                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1596                             Res::Err => return tcx.types.err,
1597                             res => {
1598                                 tcx.sess.delay_span_bug(
1599                                     DUMMY_SP,
1600                                     &format!("unexpected const parent path def {:?}", res,),
1601                                 );
1602                                 return tcx.types.err;
1603                             }
1604                         };
1605
1606                         generics
1607                             .params
1608                             .iter()
1609                             .filter(|param| {
1610                                 if let ty::GenericParamDefKind::Const = param.kind {
1611                                     true
1612                                 } else {
1613                                     false
1614                                 }
1615                             })
1616                             .nth(arg_index)
1617                             .map(|param| tcx.type_of(param.def_id))
1618                             // This is no generic parameter associated with the arg. This is
1619                             // probably from an extra arg where one is not needed.
1620                             .unwrap_or(tcx.types.err)
1621                     } else {
1622                         tcx.sess.delay_span_bug(
1623                             DUMMY_SP,
1624                             &format!("unexpected const parent path {:?}", parent_node,),
1625                         );
1626                         return tcx.types.err;
1627                     }
1628                 }
1629
1630                 x => {
1631                     tcx.sess.delay_span_bug(
1632                         DUMMY_SP,
1633                         &format!("unexpected const parent in type_of_def_id(): {:?}", x),
1634                     );
1635                     tcx.types.err
1636                 }
1637             }
1638         }
1639
1640         Node::GenericParam(param) => match &param.kind {
1641             hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1642             hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1643                 let ty = icx.to_ty(hir_ty);
1644                 if !tcx.features().const_compare_raw_pointers {
1645                     let err = match ty.peel_refs().kind {
1646                         ty::FnPtr(_) => Some("function pointers"),
1647                         ty::RawPtr(_) => Some("raw pointers"),
1648                         _ => None,
1649                     };
1650                     if let Some(unsupported_type) = err {
1651                         feature_err(
1652                             &tcx.sess.parse_sess,
1653                             sym::const_compare_raw_pointers,
1654                             hir_ty.span,
1655                             &format!(
1656                                 "using {} as const generic parameters is unstable",
1657                                 unsupported_type
1658                             ),
1659                         )
1660                         .emit();
1661                     };
1662                 }
1663                 if traits::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
1664                     .is_some()
1665                 {
1666                     struct_span_err!(
1667                         tcx.sess,
1668                         hir_ty.span,
1669                         E0741,
1670                         "the types of const generic parameters must derive `PartialEq` and `Eq`",
1671                     )
1672                     .span_label(
1673                         hir_ty.span,
1674                         format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1675                     )
1676                     .emit();
1677                 }
1678                 ty
1679             }
1680             x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1681         },
1682
1683         x => {
1684             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1685         }
1686     }
1687 }
1688
1689 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1690     use rustc_hir::{ImplItem, Item, TraitItem};
1691
1692     debug!("find_opaque_ty_constraints({:?})", def_id);
1693
1694     struct ConstraintLocator<'tcx> {
1695         tcx: TyCtxt<'tcx>,
1696         def_id: DefId,
1697         // (first found type span, actual type, mapping from the opaque type's generic
1698         // parameters to the concrete type's generic parameters)
1699         //
1700         // The mapping is an index for each use site of a generic parameter in the concrete type
1701         //
1702         // The indices index into the generic parameters on the opaque type.
1703         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1704     }
1705
1706     impl ConstraintLocator<'tcx> {
1707         fn check(&mut self, def_id: DefId) {
1708             // Don't try to check items that cannot possibly constrain the type.
1709             if !self.tcx.has_typeck_tables(def_id) {
1710                 debug!(
1711                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1712                     self.def_id, def_id,
1713                 );
1714                 return;
1715             }
1716             let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
1717             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1718                 debug!(
1719                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1720                     self.def_id, def_id, ty,
1721                 );
1722
1723                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1724                 let span = self.tcx.def_span(def_id);
1725                 // used to quickly look up the position of a generic parameter
1726                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1727                 // Skipping binder is ok, since we only use this to find generic parameters and
1728                 // their positions.
1729                 for (idx, subst) in substs.iter().enumerate() {
1730                     if let GenericArgKind::Type(ty) = subst.unpack() {
1731                         if let ty::Param(p) = ty.kind {
1732                             if index_map.insert(p, idx).is_some() {
1733                                 // There was already an entry for `p`, meaning a generic parameter
1734                                 // was used twice.
1735                                 self.tcx.sess.span_err(
1736                                     span,
1737                                     &format!(
1738                                         "defining opaque type use restricts opaque \
1739                                          type by using the generic parameter `{}` twice",
1740                                         p,
1741                                     ),
1742                                 );
1743                                 return;
1744                             }
1745                         } else {
1746                             self.tcx.sess.delay_span_bug(
1747                                 span,
1748                                 &format!(
1749                                     "non-defining opaque ty use in defining scope: {:?}, {:?}",
1750                                     concrete_type, substs,
1751                                 ),
1752                             );
1753                         }
1754                     }
1755                 }
1756                 // Compute the index within the opaque type for each generic parameter used in
1757                 // the concrete type.
1758                 let indices = concrete_type
1759                     .subst(self.tcx, substs)
1760                     .walk()
1761                     .filter_map(|t| match &t.kind {
1762                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1763                         _ => None,
1764                     })
1765                     .collect();
1766                 let is_param = |ty: Ty<'_>| match ty.kind {
1767                     ty::Param(_) => true,
1768                     _ => false,
1769                 };
1770                 let bad_substs: Vec<_> = substs
1771                     .iter()
1772                     .enumerate()
1773                     .filter_map(|(i, k)| {
1774                         if let GenericArgKind::Type(ty) = k.unpack() { Some((i, ty)) } else { None }
1775                     })
1776                     .filter(|(_, ty)| !is_param(ty))
1777                     .collect();
1778
1779                 if !bad_substs.is_empty() {
1780                     let identity_substs = InternalSubsts::identity_for_item(self.tcx, self.def_id);
1781                     for (i, bad_subst) in bad_substs {
1782                         self.tcx.sess.span_err(
1783                             span,
1784                             &format!(
1785                                 "defining opaque type use does not fully define opaque type: \
1786                             generic parameter `{}` is specified as concrete type `{}`",
1787                                 identity_substs.type_at(i),
1788                                 bad_subst
1789                             ),
1790                         );
1791                     }
1792                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1793                     let mut ty = concrete_type.walk().fuse();
1794                     let mut p_ty = prev_ty.walk().fuse();
1795                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1796                         // Type parameters are equal to any other type parameter for the purpose of
1797                         // concrete type equality, as it is possible to obtain the same type just
1798                         // by passing matching parameters to a function.
1799                         (ty::Param(_), ty::Param(_)) => true,
1800                         _ => t == p,
1801                     });
1802                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1803                         debug!("find_opaque_ty_constraints: span={:?}", span);
1804                         // Found different concrete types for the opaque type.
1805                         let mut err = self.tcx.sess.struct_span_err(
1806                             span,
1807                             "concrete type differs from previous defining opaque type use",
1808                         );
1809                         err.span_label(
1810                             span,
1811                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1812                         );
1813                         err.span_note(prev_span, "previous use here");
1814                         err.emit();
1815                     } else if indices != *prev_indices {
1816                         // Found "same" concrete types, but the generic parameter order differs.
1817                         let mut err = self.tcx.sess.struct_span_err(
1818                             span,
1819                             "concrete type's generic parameters differ from previous defining use",
1820                         );
1821                         use std::fmt::Write;
1822                         let mut s = String::new();
1823                         write!(s, "expected [").unwrap();
1824                         let list = |s: &mut String, indices: &Vec<usize>| {
1825                             let mut indices = indices.iter().cloned();
1826                             if let Some(first) = indices.next() {
1827                                 write!(s, "`{}`", substs[first]).unwrap();
1828                                 for i in indices {
1829                                     write!(s, ", `{}`", substs[i]).unwrap();
1830                                 }
1831                             }
1832                         };
1833                         list(&mut s, prev_indices);
1834                         write!(s, "], got [").unwrap();
1835                         list(&mut s, &indices);
1836                         write!(s, "]").unwrap();
1837                         err.span_label(span, s);
1838                         err.span_note(prev_span, "previous use here");
1839                         err.emit();
1840                     }
1841                 } else {
1842                     self.found = Some((span, concrete_type, indices));
1843                 }
1844             } else {
1845                 debug!(
1846                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1847                     self.def_id, def_id,
1848                 );
1849             }
1850         }
1851     }
1852
1853     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1854         type Map = Map<'tcx>;
1855
1856         fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
1857             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1858         }
1859         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
1860             debug!("find_existential_constraints: visiting {:?}", it);
1861             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1862             // The opaque type itself or its children are not within its reveal scope.
1863             if def_id != self.def_id {
1864                 self.check(def_id);
1865                 intravisit::walk_item(self, it);
1866             }
1867         }
1868         fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
1869             debug!("find_existential_constraints: visiting {:?}", it);
1870             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1871             // The opaque type itself or its children are not within its reveal scope.
1872             if def_id != self.def_id {
1873                 self.check(def_id);
1874                 intravisit::walk_impl_item(self, it);
1875             }
1876         }
1877         fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
1878             debug!("find_existential_constraints: visiting {:?}", it);
1879             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1880             self.check(def_id);
1881             intravisit::walk_trait_item(self, it);
1882         }
1883     }
1884
1885     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1886     let scope = tcx.hir().get_defining_scope(hir_id);
1887     let mut locator = ConstraintLocator { def_id, tcx, found: None };
1888
1889     debug!("find_opaque_ty_constraints: scope={:?}", scope);
1890
1891     if scope == hir::CRATE_HIR_ID {
1892         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1893     } else {
1894         debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1895         match tcx.hir().get(scope) {
1896             // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1897             // This allows our visitor to process the defining item itself, causing
1898             // it to pick up any 'sibling' defining uses.
1899             //
1900             // For example, this code:
1901             // ```
1902             // fn foo() {
1903             //     type Blah = impl Debug;
1904             //     let my_closure = || -> Blah { true };
1905             // }
1906             // ```
1907             //
1908             // requires us to explicitly process `foo()` in order
1909             // to notice the defining usage of `Blah`.
1910             Node::Item(ref it) => locator.visit_item(it),
1911             Node::ImplItem(ref it) => locator.visit_impl_item(it),
1912             Node::TraitItem(ref it) => locator.visit_trait_item(it),
1913             other => bug!("{:?} is not a valid scope for an opaque type item", other),
1914         }
1915     }
1916
1917     match locator.found {
1918         Some((_, ty, _)) => ty,
1919         None => {
1920             let span = tcx.def_span(def_id);
1921             tcx.sess.span_err(span, "could not find defining uses");
1922             tcx.types.err
1923         }
1924     }
1925 }
1926
1927 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1928     generic_args
1929         .iter()
1930         .filter_map(|arg| match arg {
1931             hir::GenericArg::Type(ty) => Some(ty),
1932             _ => None,
1933         })
1934         .any(is_suggestable_infer_ty)
1935 }
1936
1937 /// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
1938 /// use inference to provide suggestions for the appropriate type if possible.
1939 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1940     use hir::TyKind::*;
1941     match &ty.kind {
1942         Infer => true,
1943         Slice(ty) | Array(ty, _) => is_suggestable_infer_ty(ty),
1944         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1945         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1946         Def(_, generic_args) => are_suggestable_generic_args(generic_args),
1947         Path(hir::QPath::TypeRelative(ty, segment)) => {
1948             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.generic_args().args)
1949         }
1950         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1951             ty_opt.map_or(false, is_suggestable_infer_ty)
1952                 || segments
1953                     .iter()
1954                     .any(|segment| are_suggestable_generic_args(segment.generic_args().args))
1955         }
1956         _ => false,
1957     }
1958 }
1959
1960 pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1961     if let hir::FunctionRetTy::Return(ref ty) = output {
1962         if is_suggestable_infer_ty(ty) {
1963             return Some(&**ty);
1964         }
1965     }
1966     None
1967 }
1968
1969 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1970     use rustc_hir::Node::*;
1971     use rustc_hir::*;
1972
1973     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1974
1975     let icx = ItemCtxt::new(tcx, def_id);
1976
1977     match tcx.hir().get(hir_id) {
1978         TraitItem(hir::TraitItem {
1979             kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1980             ident,
1981             generics,
1982             ..
1983         })
1984         | ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
1985         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1986             match get_infer_ret_ty(&sig.decl.output) {
1987                 Some(ty) => {
1988                     let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1989                     let mut visitor = PlaceholderHirTyCollector::default();
1990                     visitor.visit_ty(ty);
1991                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1992                     let ret_ty = fn_sig.output();
1993                     if ret_ty != tcx.types.err {
1994                         diag.span_suggestion(
1995                             ty.span,
1996                             "replace with the correct return type",
1997                             ret_ty.to_string(),
1998                             Applicability::MaybeIncorrect,
1999                         );
2000                     }
2001                     diag.emit();
2002                     ty::Binder::bind(fn_sig)
2003                 }
2004                 None => AstConv::ty_of_fn(
2005                     &icx,
2006                     sig.header.unsafety,
2007                     sig.header.abi,
2008                     &sig.decl,
2009                     &generics.params[..],
2010                     Some(ident.span),
2011                 ),
2012             }
2013         }
2014
2015         TraitItem(hir::TraitItem {
2016             kind: TraitItemKind::Method(FnSig { header, decl }, _),
2017             ident,
2018             generics,
2019             ..
2020         }) => AstConv::ty_of_fn(
2021             &icx,
2022             header.unsafety,
2023             header.abi,
2024             decl,
2025             &generics.params[..],
2026             Some(ident.span),
2027         ),
2028
2029         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
2030             let abi = tcx.hir().get_foreign_abi(hir_id);
2031             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
2032         }
2033
2034         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
2035             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
2036             let inputs =
2037                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
2038             ty::Binder::bind(tcx.mk_fn_sig(
2039                 inputs,
2040                 ty,
2041                 false,
2042                 hir::Unsafety::Normal,
2043                 abi::Abi::Rust,
2044             ))
2045         }
2046
2047         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
2048             // Closure signatures are not like other function
2049             // signatures and cannot be accessed through `fn_sig`. For
2050             // example, a closure signature excludes the `self`
2051             // argument. In any case they are embedded within the
2052             // closure type as part of the `ClosureSubsts`.
2053             //
2054             // To get
2055             // the signature of a closure, you should use the
2056             // `closure_sig` method on the `ClosureSubsts`:
2057             //
2058             //    closure_substs.sig(def_id, tcx)
2059             //
2060             // or, inside of an inference context, you can use
2061             //
2062             //    infcx.closure_sig(def_id, closure_substs)
2063             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
2064         }
2065
2066         x => {
2067             bug!("unexpected sort of node in fn_sig(): {:?}", x);
2068         }
2069     }
2070 }
2071
2072 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
2073     let icx = ItemCtxt::new(tcx, def_id);
2074
2075     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2076     match tcx.hir().expect_item(hir_id).kind {
2077         hir::ItemKind::Impl { ref of_trait, .. } => of_trait.as_ref().map(|ast_trait_ref| {
2078             let selfty = tcx.type_of(def_id);
2079             AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
2080         }),
2081         _ => bug!(),
2082     }
2083 }
2084
2085 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2086     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2087     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2088     let item = tcx.hir().expect_item(hir_id);
2089     match &item.kind {
2090         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Negative, .. } => {
2091             if is_rustc_reservation {
2092                 tcx.sess.span_err(item.span, "reservation impls can't be negative");
2093             }
2094             ty::ImplPolarity::Negative
2095         }
2096         hir::ItemKind::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => {
2097             if is_rustc_reservation {
2098                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2099             }
2100             ty::ImplPolarity::Positive
2101         }
2102         hir::ItemKind::Impl {
2103             polarity: hir::ImplPolarity::Positive, of_trait: Some(_), ..
2104         } => {
2105             if is_rustc_reservation {
2106                 ty::ImplPolarity::Reservation
2107             } else {
2108                 ty::ImplPolarity::Positive
2109             }
2110         }
2111         ref item => bug!("impl_polarity: {:?} not an impl", item),
2112     }
2113 }
2114
2115 /// Returns the early-bound lifetimes declared in this generics
2116 /// listing. For anything other than fns/methods, this is just all
2117 /// the lifetimes that are declared. For fns or methods, we have to
2118 /// screen out those that do not appear in any where-clauses etc using
2119 /// `resolve_lifetime::early_bound_lifetimes`.
2120 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2121     tcx: TyCtxt<'tcx>,
2122     generics: &'a hir::Generics<'a>,
2123 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2124     generics.params.iter().filter(move |param| match param.kind {
2125         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2126         _ => false,
2127     })
2128 }
2129
2130 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2131 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2132 /// inferred constraints concerning which regions outlive other regions.
2133 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2134     debug!("predicates_defined_on({:?})", def_id);
2135     let mut result = tcx.explicit_predicates_of(def_id);
2136     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2137     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2138     if !inferred_outlives.is_empty() {
2139         debug!(
2140             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2141             def_id, inferred_outlives,
2142         );
2143         if result.predicates.is_empty() {
2144             result.predicates = inferred_outlives;
2145         } else {
2146             result.predicates = tcx
2147                 .arena
2148                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2149         }
2150     }
2151     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2152     result
2153 }
2154
2155 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2156 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2157 /// `Self: Trait` predicates for traits.
2158 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2159     let mut result = tcx.predicates_defined_on(def_id);
2160
2161     if tcx.is_trait(def_id) {
2162         // For traits, add `Self: Trait` predicate. This is
2163         // not part of the predicates that a user writes, but it
2164         // is something that one must prove in order to invoke a
2165         // method or project an associated type.
2166         //
2167         // In the chalk setup, this predicate is not part of the
2168         // "predicates" for a trait item. But it is useful in
2169         // rustc because if you directly (e.g.) invoke a trait
2170         // method like `Trait::method(...)`, you must naturally
2171         // prove that the trait applies to the types that were
2172         // used, and adding the predicate into this list ensures
2173         // that this is done.
2174         let span = tcx.def_span(def_id);
2175         result.predicates =
2176             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2177                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(),
2178                 span,
2179             ))));
2180     }
2181     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2182     result
2183 }
2184
2185 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2186 /// N.B., this does not include any implied/inferred constraints.
2187 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2188     use rustc_data_structures::fx::FxHashSet;
2189     use rustc_hir::*;
2190
2191     debug!("explicit_predicates_of(def_id={:?})", def_id);
2192
2193     /// A data structure with unique elements, which preserves order of insertion.
2194     /// Preserving the order of insertion is important here so as not to break
2195     /// compile-fail UI tests.
2196     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2197     struct UniquePredicates<'tcx> {
2198         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2199         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2200     }
2201
2202     impl<'tcx> UniquePredicates<'tcx> {
2203         fn new() -> Self {
2204             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
2205         }
2206
2207         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2208             if self.uniques.insert(value) {
2209                 self.predicates.push(value);
2210             }
2211         }
2212
2213         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2214             for value in iter {
2215                 self.push(value);
2216             }
2217         }
2218     }
2219
2220     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2221     let node = tcx.hir().get(hir_id);
2222
2223     let mut is_trait = None;
2224     let mut is_default_impl_trait = None;
2225
2226     let icx = ItemCtxt::new(tcx, def_id);
2227     let constness = icx.default_constness_for_trait_bounds();
2228
2229     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2230
2231     let mut predicates = UniquePredicates::new();
2232
2233     let ast_generics = match node {
2234         Node::TraitItem(item) => &item.generics,
2235
2236         Node::ImplItem(item) => match item.kind {
2237             ImplItemKind::OpaqueTy(ref bounds) => {
2238                 ty::print::with_no_queries(|| {
2239                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2240                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2241                     debug!(
2242                         "explicit_predicates_of({:?}): created opaque type {:?}",
2243                         def_id, opaque_ty
2244                     );
2245
2246                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2247                     let bounds = AstConv::compute_bounds(
2248                         &icx,
2249                         opaque_ty,
2250                         bounds,
2251                         SizedByDefault::Yes,
2252                         tcx.def_span(def_id),
2253                     );
2254
2255                     predicates.extend(bounds.predicates(tcx, opaque_ty));
2256                     &item.generics
2257                 })
2258             }
2259             _ => &item.generics,
2260         },
2261
2262         Node::Item(item) => {
2263             match item.kind {
2264                 ItemKind::Impl { defaultness, ref generics, .. } => {
2265                     if defaultness.is_default() {
2266                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2267                     }
2268                     generics
2269                 }
2270                 ItemKind::Fn(.., ref generics, _)
2271                 | ItemKind::TyAlias(_, ref generics)
2272                 | ItemKind::Enum(_, ref generics)
2273                 | ItemKind::Struct(_, ref generics)
2274                 | ItemKind::Union(_, ref generics) => generics,
2275
2276                 ItemKind::Trait(_, _, ref generics, .., items) => {
2277                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2278                     generics
2279                 }
2280                 ItemKind::TraitAlias(ref generics, _) => {
2281                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
2282                     generics
2283                 }
2284                 ItemKind::OpaqueTy(OpaqueTy {
2285                     ref bounds,
2286                     impl_trait_fn,
2287                     ref generics,
2288                     origin: _,
2289                 }) => {
2290                     let bounds_predicates = ty::print::with_no_queries(|| {
2291                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
2292                         let opaque_ty = tcx.mk_opaque(def_id, substs);
2293
2294                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2295                         let bounds = AstConv::compute_bounds(
2296                             &icx,
2297                             opaque_ty,
2298                             bounds,
2299                             SizedByDefault::Yes,
2300                             tcx.def_span(def_id),
2301                         );
2302
2303                         bounds.predicates(tcx, opaque_ty)
2304                     });
2305                     if impl_trait_fn.is_some() {
2306                         // opaque types
2307                         return ty::GenericPredicates {
2308                             parent: None,
2309                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2310                         };
2311                     } else {
2312                         // named opaque types
2313                         predicates.extend(bounds_predicates);
2314                         generics
2315                     }
2316                 }
2317
2318                 _ => NO_GENERICS,
2319             }
2320         }
2321
2322         Node::ForeignItem(item) => match item.kind {
2323             ForeignItemKind::Static(..) => NO_GENERICS,
2324             ForeignItemKind::Fn(_, _, ref generics) => generics,
2325             ForeignItemKind::Type => NO_GENERICS,
2326         },
2327
2328         _ => NO_GENERICS,
2329     };
2330
2331     let generics = tcx.generics_of(def_id);
2332     let parent_count = generics.parent_count as u32;
2333     let has_own_self = generics.has_self && parent_count == 0;
2334
2335     // Below we'll consider the bounds on the type parameters (including `Self`)
2336     // and the explicit where-clauses, but to get the full set of predicates
2337     // on a trait we need to add in the supertrait bounds and bounds found on
2338     // associated types.
2339     if let Some((_trait_ref, _)) = is_trait {
2340         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2341     }
2342
2343     // In default impls, we can assume that the self type implements
2344     // the trait. So in:
2345     //
2346     //     default impl Foo for Bar { .. }
2347     //
2348     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2349     // (see below). Recall that a default impl is not itself an impl, but rather a
2350     // set of defaults that can be incorporated into another impl.
2351     if let Some(trait_ref) = is_default_impl_trait {
2352         predicates.push((
2353             trait_ref.to_poly_trait_ref().without_const().to_predicate(),
2354             tcx.def_span(def_id),
2355         ));
2356     }
2357
2358     // Collect the region predicates that were declared inline as
2359     // well. In the case of parameters declared on a fn or method, we
2360     // have to be careful to only iterate over early-bound regions.
2361     let mut index = parent_count + has_own_self as u32;
2362     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2363         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2364             def_id: tcx.hir().local_def_id(param.hir_id),
2365             index,
2366             name: param.name.ident().name,
2367         }));
2368         index += 1;
2369
2370         match param.kind {
2371             GenericParamKind::Lifetime { .. } => {
2372                 param.bounds.iter().for_each(|bound| match bound {
2373                     hir::GenericBound::Outlives(lt) => {
2374                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2375                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2376                         predicates.push((outlives.to_predicate(), lt.span));
2377                     }
2378                     _ => bug!(),
2379                 });
2380             }
2381             _ => bug!(),
2382         }
2383     }
2384
2385     // Collect the predicates that were written inline by the user on each
2386     // type parameter (e.g., `<T: Foo>`).
2387     for param in ast_generics.params {
2388         if let GenericParamKind::Type { .. } = param.kind {
2389             let name = param.name.ident().name;
2390             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2391             index += 1;
2392
2393             let sized = SizedByDefault::Yes;
2394             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2395             predicates.extend(bounds.predicates(tcx, param_ty));
2396         }
2397     }
2398
2399     // Add in the bounds that appear in the where-clause.
2400     let where_clause = &ast_generics.where_clause;
2401     for predicate in where_clause.predicates {
2402         match predicate {
2403             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2404                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2405
2406                 // Keep the type around in a dummy predicate, in case of no bounds.
2407                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2408                 // is still checked for WF.
2409                 if bound_pred.bounds.is_empty() {
2410                     if let ty::Param(_) = ty.kind {
2411                         // This is a `where T:`, which can be in the HIR from the
2412                         // transformation that moves `?Sized` to `T`'s declaration.
2413                         // We can skip the predicate because type parameters are
2414                         // trivially WF, but also we *should*, to avoid exposing
2415                         // users who never wrote `where Type:,` themselves, to
2416                         // compiler/tooling bugs from not handling WF predicates.
2417                     } else {
2418                         let span = bound_pred.bounded_ty.span;
2419                         let re_root_empty = tcx.lifetimes.re_root_empty;
2420                         let predicate = ty::OutlivesPredicate(ty, re_root_empty);
2421                         predicates.push((
2422                             ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)),
2423                             span,
2424                         ));
2425                     }
2426                 }
2427
2428                 for bound in bound_pred.bounds.iter() {
2429                     match bound {
2430                         &hir::GenericBound::Trait(ref poly_trait_ref, modifier) => {
2431                             let constness = match modifier {
2432                                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2433                                 hir::TraitBoundModifier::None => constness,
2434                                 hir::TraitBoundModifier::Maybe => bug!("this wasn't handled"),
2435                             };
2436
2437                             let mut bounds = Bounds::default();
2438                             let _ = AstConv::instantiate_poly_trait_ref(
2439                                 &icx,
2440                                 poly_trait_ref,
2441                                 constness,
2442                                 ty,
2443                                 &mut bounds,
2444                             );
2445                             predicates.extend(bounds.predicates(tcx, ty));
2446                         }
2447
2448                         &hir::GenericBound::Outlives(ref lifetime) => {
2449                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2450                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2451                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2452                         }
2453                     }
2454                 }
2455             }
2456
2457             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2458                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2459                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2460                     let (r2, span) = match bound {
2461                         hir::GenericBound::Outlives(lt) => {
2462                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2463                         }
2464                         _ => bug!(),
2465                     };
2466                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2467
2468                     (ty::Predicate::RegionOutlives(pred), span)
2469                 }))
2470             }
2471
2472             &hir::WherePredicate::EqPredicate(..) => {
2473                 // FIXME(#20041)
2474             }
2475         }
2476     }
2477
2478     // Add predicates from associated type bounds.
2479     if let Some((self_trait_ref, trait_items)) = is_trait {
2480         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2481             associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2482         }))
2483     }
2484
2485     let mut predicates = predicates.predicates;
2486
2487     // Subtle: before we store the predicates into the tcx, we
2488     // sort them so that predicates like `T: Foo<Item=U>` come
2489     // before uses of `U`.  This avoids false ambiguity errors
2490     // in trait checking. See `setup_constraining_predicates`
2491     // for details.
2492     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2493         let self_ty = tcx.type_of(def_id);
2494         let trait_ref = tcx.impl_trait_ref(def_id);
2495         cgp::setup_constraining_predicates(
2496             tcx,
2497             &mut predicates,
2498             trait_ref,
2499             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2500         );
2501     }
2502
2503     let result = ty::GenericPredicates {
2504         parent: generics.parent,
2505         predicates: tcx.arena.alloc_from_iter(predicates),
2506     };
2507     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2508     result
2509 }
2510
2511 fn associated_item_predicates(
2512     tcx: TyCtxt<'tcx>,
2513     def_id: DefId,
2514     self_trait_ref: ty::TraitRef<'tcx>,
2515     trait_item_ref: &hir::TraitItemRef,
2516 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2517     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2518     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2519     let bounds = match trait_item.kind {
2520         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2521         _ => return Vec::new(),
2522     };
2523
2524     let is_gat = !tcx.generics_of(item_def_id).params.is_empty();
2525
2526     let mut had_error = false;
2527
2528     let mut unimplemented_error = |arg_kind: &str| {
2529         if !had_error {
2530             tcx.sess
2531                 .struct_span_err(
2532                     trait_item.span,
2533                     &format!("{}-generic associated types are not yet implemented", arg_kind),
2534                 )
2535                 .note(
2536                     "for more information, see issue #44265 \
2537                      <https://github.com/rust-lang/rust/issues/44265> for more information",
2538                 )
2539                 .emit();
2540             had_error = true;
2541         }
2542     };
2543
2544     let mk_bound_param = |param: &ty::GenericParamDef, _: &_| {
2545         match param.kind {
2546             ty::GenericParamDefKind::Lifetime => tcx
2547                 .mk_region(ty::RegionKind::ReLateBound(
2548                     ty::INNERMOST,
2549                     ty::BoundRegion::BrNamed(param.def_id, param.name),
2550                 ))
2551                 .into(),
2552             // FIXME(generic_associated_types): Use bound types and constants
2553             // once they are handled by the trait system.
2554             ty::GenericParamDefKind::Type { .. } => {
2555                 unimplemented_error("type");
2556                 tcx.types.err.into()
2557             }
2558             ty::GenericParamDefKind::Const => {
2559                 unimplemented_error("const");
2560                 tcx.consts.err.into()
2561             }
2562         }
2563     };
2564
2565     let bound_substs = if is_gat {
2566         // Given:
2567         //
2568         // trait X<'a, B, const C: usize> {
2569         //     type T<'d, E, const F: usize>: Default;
2570         // }
2571         //
2572         // We need to create predicates on the trait:
2573         //
2574         // for<'d, E, const F: usize>
2575         // <Self as X<'a, B, const C: usize>>::T<'d, E, const F: usize>: Sized + Default
2576         //
2577         // We substitute escaping bound parameters for the generic
2578         // arguments to the associated type which are then bound by
2579         // the `Binder` around the the predicate.
2580         //
2581         // FIXME(generic_associated_types): Currently only lifetimes are handled.
2582         self_trait_ref.substs.extend_to(tcx, item_def_id, mk_bound_param)
2583     } else {
2584         self_trait_ref.substs
2585     };
2586
2587     let assoc_ty = tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id), bound_substs);
2588
2589     let bounds = AstConv::compute_bounds(
2590         &ItemCtxt::new(tcx, def_id),
2591         assoc_ty,
2592         bounds,
2593         SizedByDefault::Yes,
2594         trait_item.span,
2595     );
2596
2597     let predicates = bounds.predicates(tcx, assoc_ty);
2598
2599     if is_gat {
2600         // We use shifts to get the regions that we're substituting to
2601         // be bound by the binders in the `Predicate`s rather that
2602         // escaping.
2603         let shifted_in = ty::fold::shift_vars(tcx, &predicates, 1);
2604         let substituted = shifted_in.subst(tcx, bound_substs);
2605         ty::fold::shift_out_vars(tcx, &substituted, 1)
2606     } else {
2607         predicates
2608     }
2609 }
2610
2611 /// Converts a specific `GenericBound` from the AST into a set of
2612 /// predicates that apply to the self type. A vector is returned
2613 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2614 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2615 /// and `<T as Bar>::X == i32`).
2616 fn predicates_from_bound<'tcx>(
2617     astconv: &dyn AstConv<'tcx>,
2618     param_ty: Ty<'tcx>,
2619     bound: &'tcx hir::GenericBound<'tcx>,
2620     constness: ast::Constness,
2621 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2622     match *bound {
2623         hir::GenericBound::Trait(ref tr, modifier) => {
2624             let constness = match modifier {
2625                 hir::TraitBoundModifier::Maybe => return vec![],
2626                 hir::TraitBoundModifier::MaybeConst => ast::Constness::NotConst,
2627                 hir::TraitBoundModifier::None => constness,
2628             };
2629
2630             let mut bounds = Bounds::default();
2631             let _ = astconv.instantiate_poly_trait_ref(tr, constness, param_ty, &mut bounds);
2632             bounds.predicates(astconv.tcx(), param_ty)
2633         }
2634         hir::GenericBound::Outlives(ref lifetime) => {
2635             let region = astconv.ast_region_to_region(lifetime, None);
2636             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2637             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2638         }
2639     }
2640 }
2641
2642 fn compute_sig_of_foreign_fn_decl<'tcx>(
2643     tcx: TyCtxt<'tcx>,
2644     def_id: DefId,
2645     decl: &'tcx hir::FnDecl<'tcx>,
2646     abi: abi::Abi,
2647 ) -> ty::PolyFnSig<'tcx> {
2648     let unsafety = if abi == abi::Abi::RustIntrinsic {
2649         intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2650     } else {
2651         hir::Unsafety::Unsafe
2652     };
2653     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
2654
2655     // Feature gate SIMD types in FFI, since I am not sure that the
2656     // ABIs are handled at all correctly. -huonw
2657     if abi != abi::Abi::RustIntrinsic
2658         && abi != abi::Abi::PlatformIntrinsic
2659         && !tcx.features().simd_ffi
2660     {
2661         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2662             if ty.is_simd() {
2663                 tcx.sess
2664                     .struct_span_err(
2665                         ast_ty.span,
2666                         &format!(
2667                             "use of SIMD type `{}` in FFI is highly experimental and \
2668                             may result in invalid code",
2669                             tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2670                         ),
2671                     )
2672                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2673                     .emit();
2674             }
2675         };
2676         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2677             check(&input, ty)
2678         }
2679         if let hir::FunctionRetTy::Return(ref ty) = decl.output {
2680             check(&ty, *fty.output().skip_binder())
2681         }
2682     }
2683
2684     fty
2685 }
2686
2687 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2688     match tcx.hir().get_if_local(def_id) {
2689         Some(Node::ForeignItem(..)) => true,
2690         Some(_) => false,
2691         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2692     }
2693 }
2694
2695 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2696     match tcx.hir().get_if_local(def_id) {
2697         Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. }))
2698         | Some(Node::ForeignItem(&hir::ForeignItem {
2699             kind: hir::ForeignItemKind::Static(_, mutbl),
2700             ..
2701         })) => Some(mutbl),
2702         Some(_) => None,
2703         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2704     }
2705 }
2706
2707 fn from_target_feature(
2708     tcx: TyCtxt<'_>,
2709     id: DefId,
2710     attr: &ast::Attribute,
2711     whitelist: &FxHashMap<String, Option<Symbol>>,
2712     target_features: &mut Vec<Symbol>,
2713 ) {
2714     let list = match attr.meta_item_list() {
2715         Some(list) => list,
2716         None => return,
2717     };
2718     let bad_item = |span| {
2719         let msg = "malformed `target_feature` attribute input";
2720         let code = "enable = \"..\"".to_owned();
2721         tcx.sess
2722             .struct_span_err(span, &msg)
2723             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2724             .emit();
2725     };
2726     let rust_features = tcx.features();
2727     for item in list {
2728         // Only `enable = ...` is accepted in the meta-item list.
2729         if !item.check_name(sym::enable) {
2730             bad_item(item.span());
2731             continue;
2732         }
2733
2734         // Must be of the form `enable = "..."` (a string).
2735         let value = match item.value_str() {
2736             Some(value) => value,
2737             None => {
2738                 bad_item(item.span());
2739                 continue;
2740             }
2741         };
2742
2743         // We allow comma separation to enable multiple features.
2744         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2745             // Only allow whitelisted features per platform.
2746             let feature_gate = match whitelist.get(feature) {
2747                 Some(g) => g,
2748                 None => {
2749                     let msg =
2750                         format!("the feature named `{}` is not valid for this target", feature);
2751                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2752                     err.span_label(
2753                         item.span(),
2754                         format!("`{}` is not valid for this target", feature),
2755                     );
2756                     if feature.starts_with("+") {
2757                         let valid = whitelist.contains_key(&feature[1..]);
2758                         if valid {
2759                             err.help("consider removing the leading `+` in the feature name");
2760                         }
2761                     }
2762                     err.emit();
2763                     return None;
2764                 }
2765             };
2766
2767             // Only allow features whose feature gates have been enabled.
2768             let allowed = match feature_gate.as_ref().map(|s| *s) {
2769                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2770                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2771                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2772                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2773                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2774                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2775                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2776                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2777                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2778                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2779                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2780                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2781                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2782                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2783                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2784                 Some(name) => bug!("unknown target feature gate {}", name),
2785                 None => true,
2786             };
2787             if !allowed && id.is_local() {
2788                 feature_err(
2789                     &tcx.sess.parse_sess,
2790                     feature_gate.unwrap(),
2791                     item.span(),
2792                     &format!("the target feature `{}` is currently unstable", feature),
2793                 )
2794                 .emit();
2795             }
2796             Some(Symbol::intern(feature))
2797         }));
2798     }
2799 }
2800
2801 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2802     use rustc::mir::mono::Linkage::*;
2803
2804     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2805     // applicable to variable declarations and may not really make sense for
2806     // Rust code in the first place but whitelist them anyway and trust that
2807     // the user knows what s/he's doing. Who knows, unanticipated use cases
2808     // may pop up in the future.
2809     //
2810     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2811     // and don't have to be, LLVM treats them as no-ops.
2812     match name {
2813         "appending" => Appending,
2814         "available_externally" => AvailableExternally,
2815         "common" => Common,
2816         "extern_weak" => ExternalWeak,
2817         "external" => External,
2818         "internal" => Internal,
2819         "linkonce" => LinkOnceAny,
2820         "linkonce_odr" => LinkOnceODR,
2821         "private" => Private,
2822         "weak" => WeakAny,
2823         "weak_odr" => WeakODR,
2824         _ => {
2825             let span = tcx.hir().span_if_local(def_id);
2826             if let Some(span) = span {
2827                 tcx.sess.span_fatal(span, "invalid linkage specified")
2828             } else {
2829                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2830             }
2831         }
2832     }
2833 }
2834
2835 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2836     let attrs = tcx.get_attrs(id);
2837
2838     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2839
2840     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2841
2842     let mut inline_span = None;
2843     let mut link_ordinal_span = None;
2844     let mut no_sanitize_span = None;
2845     for attr in attrs.iter() {
2846         if attr.check_name(sym::cold) {
2847             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2848         } else if attr.check_name(sym::rustc_allocator) {
2849             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2850         } else if attr.check_name(sym::unwind) {
2851             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2852         } else if attr.check_name(sym::ffi_returns_twice) {
2853             if tcx.is_foreign_item(id) {
2854                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2855             } else {
2856                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2857                 struct_span_err!(
2858                     tcx.sess,
2859                     attr.span,
2860                     E0724,
2861                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2862                 )
2863                 .emit();
2864             }
2865         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2866             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2867         } else if attr.check_name(sym::naked) {
2868             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2869         } else if attr.check_name(sym::no_mangle) {
2870             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2871         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2872             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2873         } else if attr.check_name(sym::no_debug) {
2874             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2875         } else if attr.check_name(sym::used) {
2876             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2877         } else if attr.check_name(sym::thread_local) {
2878             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2879         } else if attr.check_name(sym::track_caller) {
2880             if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2881                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2882                     .emit();
2883             }
2884             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2885         } else if attr.check_name(sym::export_name) {
2886             if let Some(s) = attr.value_str() {
2887                 if s.as_str().contains("\0") {
2888                     // `#[export_name = ...]` will be converted to a null-terminated string,
2889                     // so it may not contain any null characters.
2890                     struct_span_err!(
2891                         tcx.sess,
2892                         attr.span,
2893                         E0648,
2894                         "`export_name` may not contain null characters"
2895                     )
2896                     .emit();
2897                 }
2898                 codegen_fn_attrs.export_name = Some(s);
2899             }
2900         } else if attr.check_name(sym::target_feature) {
2901             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2902                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2903                 tcx.sess
2904                     .struct_span_err(attr.span, msg)
2905                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2906                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2907                     .emit();
2908             }
2909             from_target_feature(tcx, id, attr, &whitelist, &mut codegen_fn_attrs.target_features);
2910         } else if attr.check_name(sym::linkage) {
2911             if let Some(val) = attr.value_str() {
2912                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2913             }
2914         } else if attr.check_name(sym::link_section) {
2915             if let Some(val) = attr.value_str() {
2916                 if val.as_str().bytes().any(|b| b == 0) {
2917                     let msg = format!(
2918                         "illegal null byte in link_section \
2919                          value: `{}`",
2920                         &val
2921                     );
2922                     tcx.sess.span_err(attr.span, &msg);
2923                 } else {
2924                     codegen_fn_attrs.link_section = Some(val);
2925                 }
2926             }
2927         } else if attr.check_name(sym::link_name) {
2928             codegen_fn_attrs.link_name = attr.value_str();
2929         } else if attr.check_name(sym::link_ordinal) {
2930             link_ordinal_span = Some(attr.span);
2931             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2932                 codegen_fn_attrs.link_ordinal = ordinal;
2933             }
2934         } else if attr.check_name(sym::no_sanitize) {
2935             no_sanitize_span = Some(attr.span);
2936             if let Some(list) = attr.meta_item_list() {
2937                 for item in list.iter() {
2938                     if item.check_name(sym::address) {
2939                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_ADDRESS;
2940                     } else if item.check_name(sym::memory) {
2941                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_MEMORY;
2942                     } else if item.check_name(sym::thread) {
2943                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_SANITIZE_THREAD;
2944                     } else {
2945                         tcx.sess
2946                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2947                             .note("expected one of: `address`, `memory` or `thread`")
2948                             .emit();
2949                     }
2950                 }
2951             }
2952         }
2953     }
2954
2955     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2956         if !attr.has_name(sym::inline) {
2957             return ia;
2958         }
2959         match attr.meta().map(|i| i.kind) {
2960             Some(MetaItemKind::Word) => {
2961                 mark_used(attr);
2962                 InlineAttr::Hint
2963             }
2964             Some(MetaItemKind::List(ref items)) => {
2965                 mark_used(attr);
2966                 inline_span = Some(attr.span);
2967                 if items.len() != 1 {
2968                     struct_span_err!(
2969                         tcx.sess.diagnostic(),
2970                         attr.span,
2971                         E0534,
2972                         "expected one argument"
2973                     )
2974                     .emit();
2975                     InlineAttr::None
2976                 } else if list_contains_name(&items[..], sym::always) {
2977                     InlineAttr::Always
2978                 } else if list_contains_name(&items[..], sym::never) {
2979                     InlineAttr::Never
2980                 } else {
2981                     struct_span_err!(
2982                         tcx.sess.diagnostic(),
2983                         items[0].span(),
2984                         E0535,
2985                         "invalid argument"
2986                     )
2987                     .emit();
2988
2989                     InlineAttr::None
2990                 }
2991             }
2992             Some(MetaItemKind::NameValue(_)) => ia,
2993             None => ia,
2994         }
2995     });
2996
2997     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2998         if !attr.has_name(sym::optimize) {
2999             return ia;
3000         }
3001         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3002         match attr.meta().map(|i| i.kind) {
3003             Some(MetaItemKind::Word) => {
3004                 err(attr.span, "expected one argument");
3005                 ia
3006             }
3007             Some(MetaItemKind::List(ref items)) => {
3008                 mark_used(attr);
3009                 inline_span = Some(attr.span);
3010                 if items.len() != 1 {
3011                     err(attr.span, "expected one argument");
3012                     OptimizeAttr::None
3013                 } else if list_contains_name(&items[..], sym::size) {
3014                     OptimizeAttr::Size
3015                 } else if list_contains_name(&items[..], sym::speed) {
3016                     OptimizeAttr::Speed
3017                 } else {
3018                     err(items[0].span(), "invalid argument");
3019                     OptimizeAttr::None
3020                 }
3021             }
3022             Some(MetaItemKind::NameValue(_)) => ia,
3023             None => ia,
3024         }
3025     });
3026
3027     // If a function uses #[target_feature] it can't be inlined into general
3028     // purpose functions as they wouldn't have the right target features
3029     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3030     // respected.
3031     if codegen_fn_attrs.target_features.len() > 0 {
3032         if codegen_fn_attrs.inline == InlineAttr::Always {
3033             if let Some(span) = inline_span {
3034                 tcx.sess.span_err(
3035                     span,
3036                     "cannot use `#[inline(always)]` with \
3037                      `#[target_feature]`",
3038                 );
3039             }
3040         }
3041     }
3042
3043     if codegen_fn_attrs.flags.intersects(CodegenFnAttrFlags::NO_SANITIZE_ANY) {
3044         if codegen_fn_attrs.inline == InlineAttr::Always {
3045             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3046                 let hir_id = tcx.hir().as_local_hir_id(id).unwrap();
3047                 tcx.struct_span_lint_hir(
3048                     lint::builtin::INLINE_NO_SANITIZE,
3049                     hir_id,
3050                     no_sanitize_span,
3051                     |lint| {
3052                         lint.build("`no_sanitize` will have no effect after inlining")
3053                             .span_note(inline_span, "inlining requested here")
3054                             .emit();
3055                     },
3056                 )
3057             }
3058         }
3059     }
3060
3061     // Weak lang items have the same semantics as "std internal" symbols in the
3062     // sense that they're preserved through all our LTO passes and only
3063     // strippable by the linker.
3064     //
3065     // Additionally weak lang items have predetermined symbol names.
3066     if tcx.is_weak_lang_item(id) {
3067         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3068     }
3069     if let Some(name) = lang_items::link_name(&attrs) {
3070         codegen_fn_attrs.export_name = Some(name);
3071         codegen_fn_attrs.link_name = Some(name);
3072     }
3073     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3074
3075     // Internal symbols to the standard library all have no_mangle semantics in
3076     // that they have defined symbol names present in the function name. This
3077     // also applies to weak symbols where they all have known symbol names.
3078     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3079         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3080     }
3081
3082     codegen_fn_attrs
3083 }
3084
3085 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
3086     use syntax::ast::{Lit, LitIntType, LitKind};
3087     let meta_item_list = attr.meta_item_list();
3088     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3089     let sole_meta_list = match meta_item_list {
3090         Some([item]) => item.literal(),
3091         _ => None,
3092     };
3093     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3094         if *ordinal <= std::usize::MAX as u128 {
3095             Some(*ordinal as usize)
3096         } else {
3097             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3098             tcx.sess
3099                 .struct_span_err(attr.span, &msg)
3100                 .note("the value may not exceed `std::usize::MAX`")
3101                 .emit();
3102             None
3103         }
3104     } else {
3105         tcx.sess
3106             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3107             .note("an unsuffixed integer value, e.g., `1`, is expected")
3108             .emit();
3109         None
3110     }
3111 }
3112
3113 fn check_link_name_xor_ordinal(
3114     tcx: TyCtxt<'_>,
3115     codegen_fn_attrs: &CodegenFnAttrs,
3116     inline_span: Option<Span>,
3117 ) {
3118     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3119         return;
3120     }
3121     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3122     if let Some(span) = inline_span {
3123         tcx.sess.span_err(span, msg);
3124     } else {
3125         tcx.sess.err(msg);
3126     }
3127 }