src/librustc_typeck/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  18 use crate::check::intrinsic::intrinsic_operation_unsafety;
  19 use crate::constrained_generic_params as cgp;
  20 use crate::lint;
  21 use crate::middle::resolve_lifetime as rl;
  22 use crate::middle::weak_lang_items;
  23 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  24 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  25 use rustc::mir::mono::Linkage;
  26 use rustc::ty::query::Providers;
  27 use rustc::ty::subst::GenericArgKind;
  28 use rustc::ty::subst::{InternalSubsts, Subst};
  29 use rustc::ty::util::Discr;
  30 use rustc::ty::util::IntTypeExt;
  31 use rustc::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  32 use rustc::ty::{ReprOptions, ToPredicate};
  33 use rustc::util::captures::Captures;
  34 use rustc_data_structures::fx::FxHashMap;
  35 use rustc_hir as hir;
  36 use rustc_hir::def::{CtorKind, DefKind, Res};
  37 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
  38 use rustc_hir::{GenericParamKind, Node, Unsafety};
  39 use rustc_span::symbol::{kw, sym, Symbol};
  40 use rustc_span::{Span, DUMMY_SP};
  41 use rustc_target::spec::abi;
  42 use syntax::ast;
  43 use syntax::ast::{Ident, MetaItemKind};
  44 use syntax::attr::{list_contains_name, mark_used, InlineAttr, OptimizeAttr};
  45 use syntax::feature_gate;
  46
  47 use errors::{Applicability, StashKey};
  48
  49 use rustc_error_codes::*;
  50
  51 struct OnlySelfBounds(bool);
  52
  53 ///////////////////////////////////////////////////////////////////////////
  54 // Main entry point
  55
  56 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
  57     tcx.hir().visit_item_likes_in_module(
  58         module_def_id,
  59         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  60     );
  61 }
  62
  63 pub fn provide(providers: &mut Providers<'_>) {
  64     *providers = Providers {
  65         type_of,
  66         generics_of,
  67         predicates_of,
  68         predicates_defined_on,
  69         explicit_predicates_of,
  70         super_predicates_of,
  71         type_param_predicates,
  72         trait_def,
  73         adt_def,
  74         fn_sig,
  75         impl_trait_ref,
  76         impl_polarity,
  77         is_foreign_item,
  78         static_mutability,
  79         codegen_fn_attrs,
  80         collect_mod_item_types,
  81         ..*providers
  82     };
  83 }
  84
  85 ///////////////////////////////////////////////////////////////////////////
  86
  87 /// Context specific to some particular item. This is what implements
  88 /// `AstConv`. It has information about the predicates that are defined
  89 /// on the trait. Unfortunately, this predicate information is
  90 /// available in various different forms at various points in the
  91 /// process. So we can't just store a pointer to e.g., the AST or the
  92 /// parsed ty form, we have to be more flexible. To this end, the
  93 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  94 /// `get_type_parameter_bounds` requests, drawing the information from
  95 /// the AST (`hir::Generics`), recursively.
  96 pub struct ItemCtxt<'tcx> {
  97     tcx: TyCtxt<'tcx>,
  98     item_def_id: DefId,
  99 }
 100
 101 ///////////////////////////////////////////////////////////////////////////
 102
 103 #[derive(Default)]
 104 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 105
 106 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 107     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
 108         NestedVisitorMap::None
 109     }
 110     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 111         if let hir::TyKind::Infer = t.kind {
 112             self.0.push(t.span);
 113         }
 114         intravisit::walk_ty(self, t)
 115     }
 116 }
 117
 118 struct CollectItemTypesVisitor<'tcx> {
 119     tcx: TyCtxt<'tcx>,
 120 }
 121
 122 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 123 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 124 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 125 crate fn placeholder_type_error(
 126     tcx: TyCtxt<'tcx>,
 127     ident_span: Span,
 128     generics: &[hir::GenericParam<'_>],
 129     placeholder_types: Vec<Span>,
 130     suggest: bool,
 131 ) {
 132     if placeholder_types.is_empty() {
 133         return;
 134     }
 135     // This is the whitelist of possible parameter names that we might suggest.
 136     let possible_names = ["T", "K", "L", "A", "B", "C"];
 137     let used_names = generics
 138         .iter()
 139         .filter_map(|p| match p.name {
 140             hir::ParamName::Plain(ident) => Some(ident.name),
 141             _ => None,
 142         })
 143         .collect::<Vec<_>>();
 144
 145     let type_name = possible_names
 146         .iter()
 147         .find(|n| !used_names.contains(&Symbol::intern(n)))
 148         .unwrap_or(&"ParamName");
 149
 150     let mut sugg: Vec<_> =
 151         placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
 152     if generics.is_empty() {
 153         sugg.push((ident_span.shrink_to_hi(), format!("<{}>", type_name)));
 154     } else {
 155         sugg.push((
 156             generics.iter().last().unwrap().span.shrink_to_hi(),
 157             format!(", {}", type_name),
 158         ));
 159     }
 160     let mut err = bad_placeholder_type(tcx, placeholder_types);
 161     if suggest {
 162         err.multipart_suggestion(
 163             "use type parameters instead",
 164             sugg,
 165             Applicability::HasPlaceholders,
 166         );
 167     }
 168     err.emit();
 169 }
 170
 171 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 172     let (generics, suggest) = match &item.kind {
 173         hir::ItemKind::Union(_, generics)
 174         | hir::ItemKind::Enum(_, generics)
 175         | hir::ItemKind::Struct(_, generics) => (&generics.params[..], true),
 176         hir::ItemKind::TyAlias(_, generics) => (&generics.params[..], false),
 177         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 178         _ => return,
 179     };
 180
 181     let mut visitor = PlaceholderHirTyCollector::default();
 182     visitor.visit_item(item);
 183
 184     placeholder_type_error(tcx, item.ident.span, generics, visitor.0, suggest);
 185 }
 186
 187 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 188     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 189         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 190     }
 191
 192     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 193         convert_item(self.tcx, item.hir_id);
 194         reject_placeholder_type_signatures_in_item(self.tcx, item);
 195         intravisit::walk_item(self, item);
 196     }
 197
 198     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 199         for param in generics.params {
 200             match param.kind {
 201                 hir::GenericParamKind::Lifetime { .. } => {}
 202                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 203                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 204                     self.tcx.type_of(def_id);
 205                 }
 206                 hir::GenericParamKind::Type { .. } => {}
 207                 hir::GenericParamKind::Const { .. } => {
 208                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 209                     self.tcx.type_of(def_id);
 210                 }
 211             }
 212         }
 213         intravisit::walk_generics(self, generics);
 214     }
 215
 216     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 217         if let hir::ExprKind::Closure(..) = expr.kind {
 218             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 219             self.tcx.generics_of(def_id);
 220             self.tcx.type_of(def_id);
 221         }
 222         intravisit::walk_expr(self, expr);
 223     }
 224
 225     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 226         convert_trait_item(self.tcx, trait_item.hir_id);
 227         intravisit::walk_trait_item(self, trait_item);
 228     }
 229
 230     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 231         convert_impl_item(self.tcx, impl_item.hir_id);
 232         intravisit::walk_impl_item(self, impl_item);
 233     }
 234 }
 235
 236 ///////////////////////////////////////////////////////////////////////////
 237 // Utility types and common code for the above passes.
 238
 239 fn bad_placeholder_type(
 240     tcx: TyCtxt<'tcx>,
 241     mut spans: Vec<Span>,
 242 ) -> errors::DiagnosticBuilder<'tcx> {
 243     spans.sort();
 244     let mut err = struct_span_err!(
 245         tcx.sess,
 246         spans.clone(),
 247         E0121,
 248         "the type placeholder `_` is not allowed within types on item signatures",
 249     );
 250     for span in spans {
 251         err.span_label(span, "not allowed in type signatures");
 252     }
 253     err
 254 }
 255
 256 impl ItemCtxt<'tcx> {
 257     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 258         ItemCtxt { tcx, item_def_id }
 259     }
 260
 261     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 262         AstConv::ast_ty_to_ty(self, ast_ty)
 263     }
 264 }
 265
 266 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 267     fn tcx(&self) -> TyCtxt<'tcx> {
 268         self.tcx
 269     }
 270
 271     fn item_def_id(&self) -> Option<DefId> {
 272         Some(self.item_def_id)
 273     }
 274
 275     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 276         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id))
 277     }
 278
 279     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 280         None
 281     }
 282
 283     fn allow_ty_infer(&self) -> bool {
 284         false
 285     }
 286
 287     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 288         self.tcx().sess.delay_span_bug(span, "bad placeholder type");
 289         self.tcx().types.err
 290     }
 291
 292     fn ct_infer(
 293         &self,
 294         _: Ty<'tcx>,
 295         _: Option<&ty::GenericParamDef>,
 296         span: Span,
 297     ) -> &'tcx Const<'tcx> {
 298         bad_placeholder_type(self.tcx(), vec![span]).emit();
 299
 300         self.tcx().consts.err
 301     }
 302
 303     fn projected_ty_from_poly_trait_ref(
 304         &self,
 305         span: Span,
 306         item_def_id: DefId,
 307         item_segment: &hir::PathSegment<'_>,
 308         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 309     ) -> Ty<'tcx> {
 310         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 311             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 312                 self,
 313                 self.tcx,
 314                 span,
 315                 item_def_id,
 316                 item_segment,
 317                 trait_ref.substs,
 318             );
 319             self.tcx().mk_projection(item_def_id, item_substs)
 320         } else {
 321             // There are no late-bound regions; we can just ignore the binder.
 322             span_err!(
 323                 self.tcx().sess,
 324                 span,
 325                 E0212,
 326                 "cannot extract an associated type from a higher-ranked trait bound \
 327                  in this context"
 328             );
 329             self.tcx().types.err
 330         }
 331     }
 332
 333     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 334         // Types in item signatures are not normalized to avoid undue dependencies.
 335         ty
 336     }
 337
 338     fn set_tainted_by_errors(&self) {
 339         // There's no obvious place to track this, so just let it go.
 340     }
 341
 342     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 343         // There's no place to record types from signatures?
 344     }
 345 }
 346
 347 /// Returns the predicates defined on `item_def_id` of the form
 348 /// `X: Foo` where `X` is the type parameter `def_id`.
 349 fn type_param_predicates(
 350     tcx: TyCtxt<'_>,
 351     (item_def_id, def_id): (DefId, DefId),
 352 ) -> ty::GenericPredicates<'_> {
 353     use rustc_hir::*;
 354
 355     // In the AST, bounds can derive from two places. Either
 356     // written inline like `<T: Foo>` or in a where-clause like
 357     // `where T: Foo`.
 358
 359     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 360     let param_owner = tcx.hir().ty_param_owner(param_id);
 361     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 362     let generics = tcx.generics_of(param_owner_def_id);
 363     let index = generics.param_def_id_to_index[&def_id];
 364     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 365
 366     // Don't look for bounds where the type parameter isn't in scope.
 367     let parent =
 368         if item_def_id == param_owner_def_id { None } else { tcx.generics_of(item_def_id).parent };
 369
 370     let mut result = parent
 371         .map(|parent| {
 372             let icx = ItemCtxt::new(tcx, parent);
 373             icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 374         })
 375         .unwrap_or_default();
 376     let mut extend = None;
 377
 378     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 379     let ast_generics = match tcx.hir().get(item_hir_id) {
 380         Node::TraitItem(item) => &item.generics,
 381
 382         Node::ImplItem(item) => &item.generics,
 383
 384         Node::Item(item) => {
 385             match item.kind {
 386                 ItemKind::Fn(.., ref generics, _)
 387                 | ItemKind::Impl(_, _, _, ref generics, ..)
 388                 | ItemKind::TyAlias(_, ref generics)
 389                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 390                 | ItemKind::Enum(_, ref generics)
 391                 | ItemKind::Struct(_, ref generics)
 392                 | ItemKind::Union(_, ref generics) => generics,
 393                 ItemKind::Trait(_, _, ref generics, ..) => {
 394                     // Implied `Self: Trait` and supertrait bounds.
 395                     if param_id == item_hir_id {
 396                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 397                         extend = Some((identity_trait_ref.to_predicate(), item.span));
 398                     }
 399                     generics
 400                 }
 401                 _ => return result,
 402             }
 403         }
 404
 405         Node::ForeignItem(item) => match item.kind {
 406             ForeignItemKind::Fn(_, _, ref generics) => generics,
 407             _ => return result,
 408         },
 409
 410         _ => return result,
 411     };
 412
 413     let icx = ItemCtxt::new(tcx, item_def_id);
 414     let extra_predicates = extend.into_iter().chain(
 415         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 416             .into_iter()
 417             .filter(|(predicate, _)| match predicate {
 418                 ty::Predicate::Trait(ref data) => data.skip_binder().self_ty().is_param(index),
 419                 _ => false,
 420             }),
 421     );
 422     result.predicates =
 423         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 424     result
 425 }
 426
 427 impl ItemCtxt<'tcx> {
 428     /// Finds bounds from `hir::Generics`. This requires scanning through the
 429     /// AST. We do this to avoid having to convert *all* the bounds, which
 430     /// would create artificial cycles. Instead, we can only convert the
 431     /// bounds for a type parameter `X` if `X::Foo` is used.
 432     fn type_parameter_bounds_in_generics(
 433         &self,
 434         ast_generics: &'tcx hir::Generics<'tcx>,
 435         param_id: hir::HirId,
 436         ty: Ty<'tcx>,
 437         only_self_bounds: OnlySelfBounds,
 438     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 439         let from_ty_params = ast_generics
 440             .params
 441             .iter()
 442             .filter_map(|param| match param.kind {
 443                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 444                 _ => None,
 445             })
 446             .flat_map(|bounds| bounds.iter())
 447             .flat_map(|b| predicates_from_bound(self, ty, b));
 448
 449         let from_where_clauses = ast_generics
 450             .where_clause
 451             .predicates
 452             .iter()
 453             .filter_map(|wp| match *wp {
 454                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 455                 _ => None,
 456             })
 457             .flat_map(|bp| {
 458                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 459                     Some(ty)
 460                 } else if !only_self_bounds.0 {
 461                     Some(self.to_ty(&bp.bounded_ty))
 462                 } else {
 463                     None
 464                 };
 465                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 466             })
 467             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
 468
 469         from_ty_params.chain(from_where_clauses).collect()
 470     }
 471 }
 472
 473 /// Tests whether this is the AST for a reference to the type
 474 /// parameter with ID `param_id`. We use this so as to avoid running
 475 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 476 /// conversion of the type to avoid inducing unnecessary cycles.
 477 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 478     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 479         match path.res {
 480             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 481                 def_id == tcx.hir().local_def_id(param_id)
 482             }
 483             _ => false,
 484         }
 485     } else {
 486         false
 487     }
 488 }
 489
 490 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 491     let it = tcx.hir().expect_item(item_id);
 492     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 493     let def_id = tcx.hir().local_def_id(item_id);
 494     match it.kind {
 495         // These don't define types.
 496         hir::ItemKind::ExternCrate(_)
 497         | hir::ItemKind::Use(..)
 498         | hir::ItemKind::Mod(_)
 499         | hir::ItemKind::GlobalAsm(_) => {}
 500         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 501             for item in foreign_mod.items {
 502                 let def_id = tcx.hir().local_def_id(item.hir_id);
 503                 tcx.generics_of(def_id);
 504                 tcx.type_of(def_id);
 505                 tcx.predicates_of(def_id);
 506                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 507                     tcx.fn_sig(def_id);
 508                 }
 509             }
 510         }
 511         hir::ItemKind::Enum(ref enum_definition, _) => {
 512             tcx.generics_of(def_id);
 513             tcx.type_of(def_id);
 514             tcx.predicates_of(def_id);
 515             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 516         }
 517         hir::ItemKind::Impl(..) => {
 518             tcx.generics_of(def_id);
 519             tcx.type_of(def_id);
 520             tcx.impl_trait_ref(def_id);
 521             tcx.predicates_of(def_id);
 522         }
 523         hir::ItemKind::Trait(..) => {
 524             tcx.generics_of(def_id);
 525             tcx.trait_def(def_id);
 526             tcx.at(it.span).super_predicates_of(def_id);
 527             tcx.predicates_of(def_id);
 528         }
 529         hir::ItemKind::TraitAlias(..) => {
 530             tcx.generics_of(def_id);
 531             tcx.at(it.span).super_predicates_of(def_id);
 532             tcx.predicates_of(def_id);
 533         }
 534         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 535             tcx.generics_of(def_id);
 536             tcx.type_of(def_id);
 537             tcx.predicates_of(def_id);
 538
 539             for f in struct_def.fields() {
 540                 let def_id = tcx.hir().local_def_id(f.hir_id);
 541                 tcx.generics_of(def_id);
 542                 tcx.type_of(def_id);
 543                 tcx.predicates_of(def_id);
 544             }
 545
 546             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 547                 convert_variant_ctor(tcx, ctor_hir_id);
 548             }
 549         }
 550
 551         // Desugared from `impl Trait`, so visited by the function's return type.
 552         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 553
 554         hir::ItemKind::OpaqueTy(..)
 555         | hir::ItemKind::TyAlias(..)
 556         | hir::ItemKind::Static(..)
 557         | hir::ItemKind::Const(..)
 558         | hir::ItemKind::Fn(..) => {
 559             tcx.generics_of(def_id);
 560             tcx.type_of(def_id);
 561             tcx.predicates_of(def_id);
 562             if let hir::ItemKind::Fn(..) = it.kind {
 563                 tcx.fn_sig(def_id);
 564             }
 565         }
 566     }
 567 }
 568
 569 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 570     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 571     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 572     tcx.generics_of(def_id);
 573
 574     match trait_item.kind {
 575         hir::TraitItemKind::Const(..)
 576         | hir::TraitItemKind::Type(_, Some(_))
 577         | hir::TraitItemKind::Method(..) => {
 578             tcx.type_of(def_id);
 579             if let hir::TraitItemKind::Method(..) = trait_item.kind {
 580                 tcx.fn_sig(def_id);
 581             }
 582         }
 583
 584         hir::TraitItemKind::Type(_, None) => {}
 585     };
 586
 587     tcx.predicates_of(def_id);
 588 }
 589
 590 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 591     let def_id = tcx.hir().local_def_id(impl_item_id);
 592     tcx.generics_of(def_id);
 593     tcx.type_of(def_id);
 594     tcx.predicates_of(def_id);
 595     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
 596         tcx.fn_sig(def_id);
 597     }
 598 }
 599
 600 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 601     let def_id = tcx.hir().local_def_id(ctor_id);
 602     tcx.generics_of(def_id);
 603     tcx.type_of(def_id);
 604     tcx.predicates_of(def_id);
 605 }
 606
 607 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 608     let def = tcx.adt_def(def_id);
 609     let repr_type = def.repr.discr_type();
 610     let initial = repr_type.initial_discriminant(tcx);
 611     let mut prev_discr = None::<Discr<'_>>;
 612
 613     // fill the discriminant values and field types
 614     for variant in variants {
 615         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 616         prev_discr = Some(
 617             if let Some(ref e) = variant.disr_expr {
 618                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 619                 def.eval_explicit_discr(tcx, expr_did)
 620             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 621                 Some(discr)
 622             } else {
 623                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 624                     .span_label(
 625                         variant.span,
 626                         format!("overflowed on value after {}", prev_discr.unwrap()),
 627                     )
 628                     .note(&format!(
 629                         "explicitly set `{} = {}` if that is desired outcome",
 630                         variant.ident, wrapped_discr
 631                     ))
 632                     .emit();
 633                 None
 634             }
 635             .unwrap_or(wrapped_discr),
 636         );
 637
 638         for f in variant.data.fields() {
 639             let def_id = tcx.hir().local_def_id(f.hir_id);
 640             tcx.generics_of(def_id);
 641             tcx.type_of(def_id);
 642             tcx.predicates_of(def_id);
 643         }
 644
 645         // Convert the ctor, if any. This also registers the variant as
 646         // an item.
 647         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 648             convert_variant_ctor(tcx, ctor_hir_id);
 649         }
 650     }
 651 }
 652
 653 fn convert_variant(
 654     tcx: TyCtxt<'_>,
 655     variant_did: Option<DefId>,
 656     ctor_did: Option<DefId>,
 657     ident: Ident,
 658     discr: ty::VariantDiscr,
 659     def: &hir::VariantData<'_>,
 660     adt_kind: ty::AdtKind,
 661     parent_did: DefId,
 662 ) -> ty::VariantDef {
 663     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 664     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 665     let fields = def
 666         .fields()
 667         .iter()
 668         .map(|f| {
 669             let fid = tcx.hir().local_def_id(f.hir_id);
 670             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 671             if let Some(prev_span) = dup_span {
 672                 struct_span_err!(
 673                     tcx.sess,
 674                     f.span,
 675                     E0124,
 676                     "field `{}` is already declared",
 677                     f.ident
 678                 )
 679                 .span_label(f.span, "field already declared")
 680                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 681                 .emit();
 682             } else {
 683                 seen_fields.insert(f.ident.modern(), f.span);
 684             }
 685
 686             ty::FieldDef {
 687                 did: fid,
 688                 ident: f.ident,
 689                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 690             }
 691         })
 692         .collect();
 693     let recovered = match def {
 694         hir::VariantData::Struct(_, r) => *r,
 695         _ => false,
 696     };
 697     ty::VariantDef::new(
 698         tcx,
 699         ident,
 700         variant_did,
 701         ctor_did,
 702         discr,
 703         fields,
 704         CtorKind::from_hir(def),
 705         adt_kind,
 706         parent_did,
 707         recovered,
 708     )
 709 }
 710
 711 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 712     use rustc_hir::*;
 713
 714     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 715     let item = match tcx.hir().get(hir_id) {
 716         Node::Item(item) => item,
 717         _ => bug!(),
 718     };
 719
 720     let repr = ReprOptions::new(tcx, def_id);
 721     let (kind, variants) = match item.kind {
 722         ItemKind::Enum(ref def, _) => {
 723             let mut distance_from_explicit = 0;
 724             let variants = def
 725                 .variants
 726                 .iter()
 727                 .map(|v| {
 728                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 729                     let ctor_did =
 730                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 731
 732                     let discr = if let Some(ref e) = v.disr_expr {
 733                         distance_from_explicit = 0;
 734                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 735                     } else {
 736                         ty::VariantDiscr::Relative(distance_from_explicit)
 737                     };
 738                     distance_from_explicit += 1;
 739
 740                     convert_variant(
 741                         tcx,
 742                         variant_did,
 743                         ctor_did,
 744                         v.ident,
 745                         discr,
 746                         &v.data,
 747                         AdtKind::Enum,
 748                         def_id,
 749                     )
 750                 })
 751                 .collect();
 752
 753             (AdtKind::Enum, variants)
 754         }
 755         ItemKind::Struct(ref def, _) => {
 756             let variant_did = None;
 757             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 758
 759             let variants = std::iter::once(convert_variant(
 760                 tcx,
 761                 variant_did,
 762                 ctor_did,
 763                 item.ident,
 764                 ty::VariantDiscr::Relative(0),
 765                 def,
 766                 AdtKind::Struct,
 767                 def_id,
 768             ))
 769             .collect();
 770
 771             (AdtKind::Struct, variants)
 772         }
 773         ItemKind::Union(ref def, _) => {
 774             let variant_did = None;
 775             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 776
 777             let variants = std::iter::once(convert_variant(
 778                 tcx,
 779                 variant_did,
 780                 ctor_did,
 781                 item.ident,
 782                 ty::VariantDiscr::Relative(0),
 783                 def,
 784                 AdtKind::Union,
 785                 def_id,
 786             ))
 787             .collect();
 788
 789             (AdtKind::Union, variants)
 790         }
 791         _ => bug!(),
 792     };
 793     tcx.alloc_adt_def(def_id, kind, variants, repr)
 794 }
 795
 796 /// Ensures that the super-predicates of the trait with a `DefId`
 797 /// of `trait_def_id` are converted and stored. This also ensures that
 798 /// the transitive super-predicates are converted.
 799 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 800     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 801     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 802
 803     let item = match tcx.hir().get(trait_hir_id) {
 804         Node::Item(item) => item,
 805         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 806     };
 807
 808     let (generics, bounds) = match item.kind {
 809         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 810         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 811         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 812     };
 813
 814     let icx = ItemCtxt::new(tcx, trait_def_id);
 815
 816     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 817     let self_param_ty = tcx.types.self_param;
 818     let superbounds1 =
 819         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 820
 821     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 822
 823     // Convert any explicit superbounds in the where-clause,
 824     // e.g., `trait Foo where Self: Bar`.
 825     // In the case of trait aliases, however, we include all bounds in the where-clause,
 826     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 827     // as one of its "superpredicates".
 828     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 829     let superbounds2 = icx.type_parameter_bounds_in_generics(
 830         generics,
 831         item.hir_id,
 832         self_param_ty,
 833         OnlySelfBounds(!is_trait_alias),
 834     );
 835
 836     // Combine the two lists to form the complete set of superbounds:
 837     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
 838
 839     // Now require that immediate supertraits are converted,
 840     // which will, in turn, reach indirect supertraits.
 841     for &(pred, span) in superbounds {
 842         debug!("superbound: {:?}", pred);
 843         if let ty::Predicate::Trait(bound) = pred {
 844             tcx.at(span).super_predicates_of(bound.def_id());
 845         }
 846     }
 847
 848     ty::GenericPredicates { parent: None, predicates: superbounds }
 849 }
 850
 851 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 852     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 853     let item = tcx.hir().expect_item(hir_id);
 854
 855     let (is_auto, unsafety) = match item.kind {
 856         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 857         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 858         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 859     };
 860
 861     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 862     if paren_sugar && !tcx.features().unboxed_closures {
 863         let mut err = tcx.sess.struct_span_err(
 864             item.span,
 865             "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 866              which traits can use parenthetical notation",
 867         );
 868         help!(
 869             &mut err,
 870             "add `#![feature(unboxed_closures)]` to \
 871              the crate attributes to use it"
 872         );
 873         err.emit();
 874     }
 875
 876     let is_marker = tcx.has_attr(def_id, sym::marker);
 877     let def_path_hash = tcx.def_path_hash(def_id);
 878     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 879     tcx.arena.alloc(def)
 880 }
 881
 882 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 883     struct LateBoundRegionsDetector<'tcx> {
 884         tcx: TyCtxt<'tcx>,
 885         outer_index: ty::DebruijnIndex,
 886         has_late_bound_regions: Option<Span>,
 887     }
 888
 889     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 890         fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 891             NestedVisitorMap::None
 892         }
 893
 894         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
 895             if self.has_late_bound_regions.is_some() {
 896                 return;
 897             }
 898             match ty.kind {
 899                 hir::TyKind::BareFn(..) => {
 900                     self.outer_index.shift_in(1);
 901                     intravisit::walk_ty(self, ty);
 902                     self.outer_index.shift_out(1);
 903                 }
 904                 _ => intravisit::walk_ty(self, ty),
 905             }
 906         }
 907
 908         fn visit_poly_trait_ref(
 909             &mut self,
 910             tr: &'tcx hir::PolyTraitRef<'tcx>,
 911             m: hir::TraitBoundModifier,
 912         ) {
 913             if self.has_late_bound_regions.is_some() {
 914                 return;
 915             }
 916             self.outer_index.shift_in(1);
 917             intravisit::walk_poly_trait_ref(self, tr, m);
 918             self.outer_index.shift_out(1);
 919         }
 920
 921         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 922             if self.has_late_bound_regions.is_some() {
 923                 return;
 924             }
 925
 926             match self.tcx.named_region(lt.hir_id) {
 927                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 928                 Some(rl::Region::LateBound(debruijn, _, _))
 929                 | Some(rl::Region::LateBoundAnon(debruijn, _))
 930                     if debruijn < self.outer_index => {}
 931                 Some(rl::Region::LateBound(..))
 932                 | Some(rl::Region::LateBoundAnon(..))
 933                 | Some(rl::Region::Free(..))
 934                 | None => {
 935                     self.has_late_bound_regions = Some(lt.span);
 936                 }
 937             }
 938         }
 939     }
 940
 941     fn has_late_bound_regions<'tcx>(
 942         tcx: TyCtxt<'tcx>,
 943         generics: &'tcx hir::Generics<'tcx>,
 944         decl: &'tcx hir::FnDecl<'tcx>,
 945     ) -> Option<Span> {
 946         let mut visitor = LateBoundRegionsDetector {
 947             tcx,
 948             outer_index: ty::INNERMOST,
 949             has_late_bound_regions: None,
 950         };
 951         for param in generics.params {
 952             if let GenericParamKind::Lifetime { .. } = param.kind {
 953                 if tcx.is_late_bound(param.hir_id) {
 954                     return Some(param.span);
 955                 }
 956             }
 957         }
 958         visitor.visit_fn_decl(decl);
 959         visitor.has_late_bound_regions
 960     }
 961
 962     match node {
 963         Node::TraitItem(item) => match item.kind {
 964             hir::TraitItemKind::Method(ref sig, _) => {
 965                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 966             }
 967             _ => None,
 968         },
 969         Node::ImplItem(item) => match item.kind {
 970             hir::ImplItemKind::Method(ref sig, _) => {
 971                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 972             }
 973             _ => None,
 974         },
 975         Node::ForeignItem(item) => match item.kind {
 976             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
 977                 has_late_bound_regions(tcx, generics, fn_decl)
 978             }
 979             _ => None,
 980         },
 981         Node::Item(item) => match item.kind {
 982             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
 983                 has_late_bound_regions(tcx, generics, &sig.decl)
 984             }
 985             _ => None,
 986         },
 987         _ => None,
 988     }
 989 }
 990
 991 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
 992     use rustc_hir::*;
 993
 994     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 995
 996     let node = tcx.hir().get(hir_id);
 997     let parent_def_id = match node {
 998         Node::ImplItem(_)
 999         | Node::TraitItem(_)
1000         | Node::Variant(_)
1001         | Node::Ctor(..)
1002         | Node::Field(_) => {
1003             let parent_id = tcx.hir().get_parent_item(hir_id);
1004             Some(tcx.hir().local_def_id(parent_id))
1005         }
1006         // FIXME(#43408) enable this always when we get lazy normalization.
1007         Node::AnonConst(_) => {
1008             // HACK(eddyb) this provides the correct generics when
1009             // `feature(const_generics)` is enabled, so that const expressions
1010             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1011             if tcx.features().const_generics {
1012                 let parent_id = tcx.hir().get_parent_item(hir_id);
1013                 Some(tcx.hir().local_def_id(parent_id))
1014             } else {
1015                 None
1016             }
1017         }
1018         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1019             Some(tcx.closure_base_def_id(def_id))
1020         }
1021         Node::Item(item) => match item.kind {
1022             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
1023             _ => None,
1024         },
1025         _ => None,
1026     };
1027
1028     let mut opt_self = None;
1029     let mut allow_defaults = false;
1030
1031     let no_generics = hir::Generics::empty();
1032     let ast_generics = match node {
1033         Node::TraitItem(item) => &item.generics,
1034
1035         Node::ImplItem(item) => &item.generics,
1036
1037         Node::Item(item) => {
1038             match item.kind {
1039                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
1040                     generics
1041                 }
1042
1043                 ItemKind::TyAlias(_, ref generics)
1044                 | ItemKind::Enum(_, ref generics)
1045                 | ItemKind::Struct(_, ref generics)
1046                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1047                 | ItemKind::Union(_, ref generics) => {
1048                     allow_defaults = true;
1049                     generics
1050                 }
1051
1052                 ItemKind::Trait(_, _, ref generics, ..)
1053                 | ItemKind::TraitAlias(ref generics, ..) => {
1054                     // Add in the self type parameter.
1055                     //
1056                     // Something of a hack: use the node id for the trait, also as
1057                     // the node id for the Self type parameter.
1058                     let param_id = item.hir_id;
1059
1060                     opt_self = Some(ty::GenericParamDef {
1061                         index: 0,
1062                         name: kw::SelfUpper,
1063                         def_id: tcx.hir().local_def_id(param_id),
1064                         pure_wrt_drop: false,
1065                         kind: ty::GenericParamDefKind::Type {
1066                             has_default: false,
1067                             object_lifetime_default: rl::Set1::Empty,
1068                             synthetic: None,
1069                         },
1070                     });
1071
1072                     allow_defaults = true;
1073                     generics
1074                 }
1075
1076                 _ => &no_generics,
1077             }
1078         }
1079
1080         Node::ForeignItem(item) => match item.kind {
1081             ForeignItemKind::Static(..) => &no_generics,
1082             ForeignItemKind::Fn(_, _, ref generics) => generics,
1083             ForeignItemKind::Type => &no_generics,
1084         },
1085
1086         _ => &no_generics,
1087     };
1088
1089     let has_self = opt_self.is_some();
1090     let mut parent_has_self = false;
1091     let mut own_start = has_self as u32;
1092     let parent_count = parent_def_id.map_or(0, |def_id| {
1093         let generics = tcx.generics_of(def_id);
1094         assert_eq!(has_self, false);
1095         parent_has_self = generics.has_self;
1096         own_start = generics.count() as u32;
1097         generics.parent_count + generics.params.len()
1098     });
1099
1100     let mut params: Vec<_> = opt_self.into_iter().collect();
1101
1102     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1103     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1104         name: param.name.ident().name,
1105         index: own_start + i as u32,
1106         def_id: tcx.hir().local_def_id(param.hir_id),
1107         pure_wrt_drop: param.pure_wrt_drop,
1108         kind: ty::GenericParamDefKind::Lifetime,
1109     }));
1110
1111     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1112
1113     // Now create the real type parameters.
1114     let type_start = own_start - has_self as u32 + params.len() as u32;
1115     let mut i = 0;
1116     params.extend(ast_generics.params.iter().filter_map(|param| {
1117         let kind = match param.kind {
1118             GenericParamKind::Type { ref default, synthetic, .. } => {
1119                 if !allow_defaults && default.is_some() {
1120                     if !tcx.features().default_type_parameter_fallback {
1121                         tcx.lint_hir(
1122                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1123                             param.hir_id,
1124                             param.span,
1125                             &format!(
1126                                 "defaults for type parameters are only allowed in \
1127                                         `struct`, `enum`, `type`, or `trait` definitions."
1128                             ),
1129                         );
1130                     }
1131                 }
1132
1133                 ty::GenericParamDefKind::Type {
1134                     has_default: default.is_some(),
1135                     object_lifetime_default: object_lifetime_defaults
1136                         .as_ref()
1137                         .map_or(rl::Set1::Empty, |o| o[i]),
1138                     synthetic,
1139                 }
1140             }
1141             GenericParamKind::Const { .. } => ty::GenericParamDefKind::Const,
1142             _ => return None,
1143         };
1144
1145         let param_def = ty::GenericParamDef {
1146             index: type_start + i as u32,
1147             name: param.name.ident().name,
1148             def_id: tcx.hir().local_def_id(param.hir_id),
1149             pure_wrt_drop: param.pure_wrt_drop,
1150             kind,
1151         };
1152         i += 1;
1153         Some(param_def)
1154     }));
1155
1156     // provide junk type parameter defs - the only place that
1157     // cares about anything but the length is instantiation,
1158     // and we don't do that for closures.
1159     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1160         let dummy_args = if gen.is_some() {
1161             &["<yield_ty>", "<return_ty>", "<witness>"][..]
1162         } else {
1163             &["<closure_kind>", "<closure_signature>"][..]
1164         };
1165
1166         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1167             index: type_start + i as u32,
1168             name: Symbol::intern(arg),
1169             def_id,
1170             pure_wrt_drop: false,
1171             kind: ty::GenericParamDefKind::Type {
1172                 has_default: false,
1173                 object_lifetime_default: rl::Set1::Empty,
1174                 synthetic: None,
1175             },
1176         }));
1177
1178         if let Some(upvars) = tcx.upvars(def_id) {
1179             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1180                 ty::GenericParamDef {
1181                     index: type_start + i,
1182                     name: Symbol::intern("<upvar>"),
1183                     def_id,
1184                     pure_wrt_drop: false,
1185                     kind: ty::GenericParamDefKind::Type {
1186                         has_default: false,
1187                         object_lifetime_default: rl::Set1::Empty,
1188                         synthetic: None,
1189                     },
1190                 }
1191             }));
1192         }
1193     }
1194
1195     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1196
1197     tcx.arena.alloc(ty::Generics {
1198         parent: parent_def_id,
1199         parent_count,
1200         params,
1201         param_def_id_to_index,
1202         has_self: has_self || parent_has_self,
1203         has_late_bound_regions: has_late_bound_regions(tcx, node),
1204     })
1205 }
1206
1207 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1208     span_err!(
1209         tcx.sess,
1210         span,
1211         E0202,
1212         "associated types are not yet supported in inherent impls (see #8995)"
1213     );
1214 }
1215
1216 fn infer_placeholder_type(
1217     tcx: TyCtxt<'_>,
1218     def_id: DefId,
1219     body_id: hir::BodyId,
1220     span: Span,
1221     item_ident: Ident,
1222 ) -> Ty<'_> {
1223     let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
1224
1225     // If this came from a free `const` or `static mut?` item,
1226     // then the user may have written e.g. `const A = 42;`.
1227     // In this case, the parser has stashed a diagnostic for
1228     // us to improve in typeck so we do that now.
1229     match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1230         Some(mut err) => {
1231             // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1232             // We are typeck and have the real type, so remove that and suggest the actual type.
1233             err.suggestions.clear();
1234             err.span_suggestion(
1235                 span,
1236                 "provide a type for the item",
1237                 format!("{}: {}", item_ident, ty),
1238                 Applicability::MachineApplicable,
1239             )
1240             .emit();
1241         }
1242         None => {
1243             let mut diag = bad_placeholder_type(tcx, vec![span]);
1244             if ty != tcx.types.err {
1245                 diag.span_suggestion(
1246                     span,
1247                     "replace `_` with the correct type",
1248                     ty.to_string(),
1249                     Applicability::MaybeIncorrect,
1250                 );
1251             }
1252             diag.emit();
1253         }
1254     }
1255
1256     ty
1257 }
1258
1259 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1260     use rustc_hir::*;
1261
1262     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1263
1264     let icx = ItemCtxt::new(tcx, def_id);
1265
1266     match tcx.hir().get(hir_id) {
1267         Node::TraitItem(item) => match item.kind {
1268             TraitItemKind::Method(..) => {
1269                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1270                 tcx.mk_fn_def(def_id, substs)
1271             }
1272             TraitItemKind::Const(ref ty, body_id) => body_id
1273                 .and_then(|body_id| {
1274                     if is_suggestable_infer_ty(ty) {
1275                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1276                     } else {
1277                         None
1278                     }
1279                 })
1280                 .unwrap_or_else(|| icx.to_ty(ty)),
1281             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1282             TraitItemKind::Type(_, None) => {
1283                 span_bug!(item.span, "associated type missing default");
1284             }
1285         },
1286
1287         Node::ImplItem(item) => match item.kind {
1288             ImplItemKind::Method(..) => {
1289                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1290                 tcx.mk_fn_def(def_id, substs)
1291             }
1292             ImplItemKind::Const(ref ty, body_id) => {
1293                 if is_suggestable_infer_ty(ty) {
1294                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1295                 } else {
1296                     icx.to_ty(ty)
1297                 }
1298             }
1299             ImplItemKind::OpaqueTy(_) => {
1300                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1301                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1302                 }
1303
1304                 find_opaque_ty_constraints(tcx, def_id)
1305             }
1306             ImplItemKind::TyAlias(ref ty) => {
1307                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1308                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1309                 }
1310
1311                 icx.to_ty(ty)
1312             }
1313         },
1314
1315         Node::Item(item) => {
1316             match item.kind {
1317                 ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
1318                     if is_suggestable_infer_ty(ty) {
1319                         infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1320                     } else {
1321                         icx.to_ty(ty)
1322                     }
1323                 }
1324                 ItemKind::TyAlias(ref ty, _) | ItemKind::Impl(.., ref ty, _) => icx.to_ty(ty),
1325                 ItemKind::Fn(..) => {
1326                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1327                     tcx.mk_fn_def(def_id, substs)
1328                 }
1329                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1330                     let def = tcx.adt_def(def_id);
1331                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1332                     tcx.mk_adt(def, substs)
1333                 }
1334                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
1335                     find_opaque_ty_constraints(tcx, def_id)
1336                 }
1337                 // Opaque types desugared from `impl Trait`.
1338                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
1339                     tcx.typeck_tables_of(owner)
1340                         .concrete_opaque_types
1341                         .get(&def_id)
1342                         .map(|opaque| opaque.concrete_type)
1343                         .unwrap_or_else(|| {
1344                             // This can occur if some error in the
1345                             // owner fn prevented us from populating
1346                             // the `concrete_opaque_types` table.
1347                             tcx.sess.delay_span_bug(
1348                                 DUMMY_SP,
1349                                 &format!(
1350                                     "owner {:?} has no opaque type for {:?} in its tables",
1351                                     owner, def_id,
1352                                 ),
1353                             );
1354                             tcx.types.err
1355                         })
1356                 }
1357                 ItemKind::Trait(..)
1358                 | ItemKind::TraitAlias(..)
1359                 | ItemKind::Mod(..)
1360                 | ItemKind::ForeignMod(..)
1361                 | ItemKind::GlobalAsm(..)
1362                 | ItemKind::ExternCrate(..)
1363                 | ItemKind::Use(..) => {
1364                     span_bug!(
1365                         item.span,
1366                         "compute_type_of_item: unexpected item type: {:?}",
1367                         item.kind
1368                     );
1369                 }
1370             }
1371         }
1372
1373         Node::ForeignItem(foreign_item) => match foreign_item.kind {
1374             ForeignItemKind::Fn(..) => {
1375                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1376                 tcx.mk_fn_def(def_id, substs)
1377             }
1378             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1379             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1380         },
1381
1382         Node::Ctor(&ref def) | Node::Variant(hir::Variant { data: ref def, .. }) => match *def {
1383             VariantData::Unit(..) | VariantData::Struct(..) => {
1384                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1385             }
1386             VariantData::Tuple(..) => {
1387                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1388                 tcx.mk_fn_def(def_id, substs)
1389             }
1390         },
1391
1392         Node::Field(field) => icx.to_ty(&field.ty),
1393
1394         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) => {
1395             if gen.is_some() {
1396                 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1397             }
1398
1399             let substs = InternalSubsts::identity_for_item(tcx, def_id);
1400             tcx.mk_closure(def_id, substs)
1401         }
1402
1403         Node::AnonConst(_) => {
1404             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1405             match parent_node {
1406                 Node::Ty(&hir::Ty { kind: hir::TyKind::Array(_, ref constant), .. })
1407                 | Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref constant), .. })
1408                 | Node::Expr(&hir::Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1409                     if constant.hir_id == hir_id =>
1410                 {
1411                     tcx.types.usize
1412                 }
1413
1414                 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
1415                     tcx.adt_def(tcx.hir().get_parent_did(hir_id)).repr.discr_type().to_ty(tcx)
1416                 }
1417
1418                 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. })
1419                 | Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. })
1420                 | Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. })
1421                 | Node::TraitRef(..) => {
1422                     let path = match parent_node {
1423                         Node::Ty(&hir::Ty {
1424                             kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1425                             ..
1426                         })
1427                         | Node::Expr(&hir::Expr {
1428                             kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1429                             ..
1430                         }) => Some(&**path),
1431                         Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1432                             if let QPath::Resolved(_, ref path) = **path {
1433                                 Some(&**path)
1434                             } else {
1435                                 None
1436                             }
1437                         }
1438                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1439                         _ => None,
1440                     };
1441
1442                     if let Some(path) = path {
1443                         let arg_index = path
1444                             .segments
1445                             .iter()
1446                             .filter_map(|seg| seg.args.as_ref())
1447                             .map(|generic_args| generic_args.args.as_ref())
1448                             .find_map(|args| {
1449                                 args.iter()
1450                                     .filter(|arg| arg.is_const())
1451                                     .enumerate()
1452                                     .filter(|(_, arg)| arg.id() == hir_id)
1453                                     .map(|(index, _)| index)
1454                                     .next()
1455                             })
1456                             .unwrap_or_else(|| {
1457                                 bug!("no arg matching AnonConst in path");
1458                             });
1459
1460                         // We've encountered an `AnonConst` in some path, so we need to
1461                         // figure out which generic parameter it corresponds to and return
1462                         // the relevant type.
1463                         let generics = match path.res {
1464                             Res::Def(DefKind::Ctor(..), def_id) => {
1465                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1466                             }
1467                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1468                             Res::Err => return tcx.types.err,
1469                             res => {
1470                                 tcx.sess.delay_span_bug(
1471                                     DUMMY_SP,
1472                                     &format!("unexpected const parent path def {:?}", res,),
1473                                 );
1474                                 return tcx.types.err;
1475                             }
1476                         };
1477
1478                         generics
1479                             .params
1480                             .iter()
1481                             .filter(|param| {
1482                                 if let ty::GenericParamDefKind::Const = param.kind {
1483                                     true
1484                                 } else {
1485                                     false
1486                                 }
1487                             })
1488                             .nth(arg_index)
1489                             .map(|param| tcx.type_of(param.def_id))
1490                             // This is no generic parameter associated with the arg. This is
1491                             // probably from an extra arg where one is not needed.
1492                             .unwrap_or(tcx.types.err)
1493                     } else {
1494                         tcx.sess.delay_span_bug(
1495                             DUMMY_SP,
1496                             &format!("unexpected const parent path {:?}", parent_node,),
1497                         );
1498                         return tcx.types.err;
1499                     }
1500                 }
1501
1502                 x => {
1503                     tcx.sess.delay_span_bug(
1504                         DUMMY_SP,
1505                         &format!("unexpected const parent in type_of_def_id(): {:?}", x),
1506                     );
1507                     tcx.types.err
1508                 }
1509             }
1510         }
1511
1512         Node::GenericParam(param) => {
1513             match &param.kind {
1514                 hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1515                 hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1516                     let ty = icx.to_ty(hir_ty);
1517                     if !tcx.features().const_compare_raw_pointers {
1518                         let err = match ty.peel_refs().kind {
1519                             ty::FnPtr(_) => Some("function pointers"),
1520                             ty::RawPtr(_) => Some("raw pointers"),
1521                             _ => None,
1522                         };
1523                         if let Some(unsupported_type) = err {
1524                             feature_gate::feature_err(
1525                                 &tcx.sess.parse_sess,
1526                                 sym::const_compare_raw_pointers,
1527                                 hir_ty.span,
1528                                 &format!(
1529                                     "using {} as const generic parameters is unstable",
1530                                     unsupported_type
1531                                 ),
1532                             )
1533                             .emit();
1534                         };
1535                     }
1536                     if ty::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
1537                         .is_some()
1538                     {
1539                         struct_span_err!(
1540                         tcx.sess,
1541                         hir_ty.span,
1542                         E0741,
1543                         "the types of const generic parameters must derive `PartialEq` and `Eq`",
1544                     ).span_label(
1545                         hir_ty.span,
1546                         format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1547                     ).emit();
1548                     }
1549                     ty
1550                 }
1551                 x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1552             }
1553         }
1554
1555         x => {
1556             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1557         }
1558     }
1559 }
1560
1561 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1562     use rustc_hir::{ImplItem, Item, TraitItem};
1563
1564     debug!("find_opaque_ty_constraints({:?})", def_id);
1565
1566     struct ConstraintLocator<'tcx> {
1567         tcx: TyCtxt<'tcx>,
1568         def_id: DefId,
1569         // (first found type span, actual type, mapping from the opaque type's generic
1570         // parameters to the concrete type's generic parameters)
1571         //
1572         // The mapping is an index for each use site of a generic parameter in the concrete type
1573         //
1574         // The indices index into the generic parameters on the opaque type.
1575         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1576     }
1577
1578     impl ConstraintLocator<'tcx> {
1579         fn check(&mut self, def_id: DefId) {
1580             // Don't try to check items that cannot possibly constrain the type.
1581             if !self.tcx.has_typeck_tables(def_id) {
1582                 debug!(
1583                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1584                     self.def_id, def_id,
1585                 );
1586                 return;
1587             }
1588             let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
1589             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1590                 debug!(
1591                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1592                     self.def_id, def_id, ty,
1593                 );
1594
1595                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1596                 let span = self.tcx.def_span(def_id);
1597                 // used to quickly look up the position of a generic parameter
1598                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1599                 // Skipping binder is ok, since we only use this to find generic parameters and
1600                 // their positions.
1601                 for (idx, subst) in substs.iter().enumerate() {
1602                     if let GenericArgKind::Type(ty) = subst.unpack() {
1603                         if let ty::Param(p) = ty.kind {
1604                             if index_map.insert(p, idx).is_some() {
1605                                 // There was already an entry for `p`, meaning a generic parameter
1606                                 // was used twice.
1607                                 self.tcx.sess.span_err(
1608                                     span,
1609                                     &format!(
1610                                         "defining opaque type use restricts opaque \
1611                                          type by using the generic parameter `{}` twice",
1612                                         p,
1613                                     ),
1614                                 );
1615                                 return;
1616                             }
1617                         } else {
1618                             self.tcx.sess.delay_span_bug(
1619                                 span,
1620                                 &format!(
1621                                     "non-defining opaque ty use in defining scope: {:?}, {:?}",
1622                                     concrete_type, substs,
1623                                 ),
1624                             );
1625                         }
1626                     }
1627                 }
1628                 // Compute the index within the opaque type for each generic parameter used in
1629                 // the concrete type.
1630                 let indices = concrete_type
1631                     .subst(self.tcx, substs)
1632                     .walk()
1633                     .filter_map(|t| match &t.kind {
1634                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1635                         _ => None,
1636                     })
1637                     .collect();
1638                 let is_param = |ty: Ty<'_>| match ty.kind {
1639                     ty::Param(_) => true,
1640                     _ => false,
1641                 };
1642                 let bad_substs: Vec<_> =
1643                     substs.types().enumerate().filter(|(_, ty)| !is_param(ty)).collect();
1644                 if !bad_substs.is_empty() {
1645                     let identity_substs = InternalSubsts::identity_for_item(self.tcx, self.def_id);
1646                     for (i, bad_subst) in bad_substs {
1647                         self.tcx.sess.span_err(
1648                             span,
1649                             &format!(
1650                                 "defining opaque type use does not fully define opaque type: \
1651                             generic parameter `{}` is specified as concrete type `{}`",
1652                                 identity_substs.type_at(i),
1653                                 bad_subst
1654                             ),
1655                         );
1656                     }
1657                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1658                     let mut ty = concrete_type.walk().fuse();
1659                     let mut p_ty = prev_ty.walk().fuse();
1660                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1661                         // Type parameters are equal to any other type parameter for the purpose of
1662                         // concrete type equality, as it is possible to obtain the same type just
1663                         // by passing matching parameters to a function.
1664                         (ty::Param(_), ty::Param(_)) => true,
1665                         _ => t == p,
1666                     });
1667                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1668                         debug!("find_opaque_ty_constraints: span={:?}", span);
1669                         // Found different concrete types for the opaque type.
1670                         let mut err = self.tcx.sess.struct_span_err(
1671                             span,
1672                             "concrete type differs from previous defining opaque type use",
1673                         );
1674                         err.span_label(
1675                             span,
1676                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1677                         );
1678                         err.span_note(prev_span, "previous use here");
1679                         err.emit();
1680                     } else if indices != *prev_indices {
1681                         // Found "same" concrete types, but the generic parameter order differs.
1682                         let mut err = self.tcx.sess.struct_span_err(
1683                             span,
1684                             "concrete type's generic parameters differ from previous defining use",
1685                         );
1686                         use std::fmt::Write;
1687                         let mut s = String::new();
1688                         write!(s, "expected [").unwrap();
1689                         let list = |s: &mut String, indices: &Vec<usize>| {
1690                             let mut indices = indices.iter().cloned();
1691                             if let Some(first) = indices.next() {
1692                                 write!(s, "`{}`", substs[first]).unwrap();
1693                                 for i in indices {
1694                                     write!(s, ", `{}`", substs[i]).unwrap();
1695                                 }
1696                             }
1697                         };
1698                         list(&mut s, prev_indices);
1699                         write!(s, "], got [").unwrap();
1700                         list(&mut s, &indices);
1701                         write!(s, "]").unwrap();
1702                         err.span_label(span, s);
1703                         err.span_note(prev_span, "previous use here");
1704                         err.emit();
1705                     }
1706                 } else {
1707                     self.found = Some((span, concrete_type, indices));
1708                 }
1709             } else {
1710                 debug!(
1711                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1712                     self.def_id, def_id,
1713                 );
1714             }
1715         }
1716     }
1717
1718     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1719         fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1720             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1721         }
1722         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
1723             debug!("find_existential_constraints: visiting {:?}", it);
1724             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1725             // The opaque type itself or its children are not within its reveal scope.
1726             if def_id != self.def_id {
1727                 self.check(def_id);
1728                 intravisit::walk_item(self, it);
1729             }
1730         }
1731         fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
1732             debug!("find_existential_constraints: visiting {:?}", it);
1733             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1734             // The opaque type itself or its children are not within its reveal scope.
1735             if def_id != self.def_id {
1736                 self.check(def_id);
1737                 intravisit::walk_impl_item(self, it);
1738             }
1739         }
1740         fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
1741             debug!("find_existential_constraints: visiting {:?}", it);
1742             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1743             self.check(def_id);
1744             intravisit::walk_trait_item(self, it);
1745         }
1746     }
1747
1748     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1749     let scope = tcx.hir().get_defining_scope(hir_id);
1750     let mut locator = ConstraintLocator { def_id, tcx, found: None };
1751
1752     debug!("find_opaque_ty_constraints: scope={:?}", scope);
1753
1754     if scope == hir::CRATE_HIR_ID {
1755         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1756     } else {
1757         debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1758         match tcx.hir().get(scope) {
1759             // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1760             // This allows our visitor to process the defining item itself, causing
1761             // it to pick up any 'sibling' defining uses.
1762             //
1763             // For example, this code:
1764             // ```
1765             // fn foo() {
1766             //     type Blah = impl Debug;
1767             //     let my_closure = || -> Blah { true };
1768             // }
1769             // ```
1770             //
1771             // requires us to explicitly process `foo()` in order
1772             // to notice the defining usage of `Blah`.
1773             Node::Item(ref it) => locator.visit_item(it),
1774             Node::ImplItem(ref it) => locator.visit_impl_item(it),
1775             Node::TraitItem(ref it) => locator.visit_trait_item(it),
1776             other => bug!("{:?} is not a valid scope for an opaque type item", other),
1777         }
1778     }
1779
1780     match locator.found {
1781         Some((_, ty, _)) => ty,
1782         None => {
1783             let span = tcx.def_span(def_id);
1784             tcx.sess.span_err(span, "could not find defining uses");
1785             tcx.types.err
1786         }
1787     }
1788 }
1789
1790 /// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
1791 /// use inference to provide suggestions for the appropriate type if possible.
1792 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1793     match &ty.kind {
1794         hir::TyKind::Infer => true,
1795         hir::TyKind::Slice(ty) | hir::TyKind::Array(ty, _) => is_suggestable_infer_ty(ty),
1796         hir::TyKind::Tup(tys) => tys.iter().any(|ty| is_suggestable_infer_ty(ty)),
1797         _ => false,
1798     }
1799 }
1800
1801 pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1802     if let hir::FunctionRetTy::Return(ref ty) = output {
1803         if is_suggestable_infer_ty(ty) {
1804             return Some(&**ty);
1805         }
1806     }
1807     None
1808 }
1809
1810 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1811     use rustc_hir::Node::*;
1812     use rustc_hir::*;
1813
1814     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1815
1816     let icx = ItemCtxt::new(tcx, def_id);
1817
1818     match tcx.hir().get(hir_id) {
1819         TraitItem(hir::TraitItem {
1820             kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1821             ident,
1822             generics,
1823             ..
1824         })
1825         | ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
1826         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1827             match get_infer_ret_ty(&sig.decl.output) {
1828                 Some(ty) => {
1829                     let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1830                     let mut visitor = PlaceholderHirTyCollector::default();
1831                     visitor.visit_ty(ty);
1832                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1833                     let ret_ty = fn_sig.output();
1834                     if ret_ty != tcx.types.err {
1835                         diag.span_suggestion(
1836                             ty.span,
1837                             "replace with the correct return type",
1838                             ret_ty.to_string(),
1839                             Applicability::MaybeIncorrect,
1840                         );
1841                     }
1842                     diag.emit();
1843                     ty::Binder::bind(fn_sig)
1844                 }
1845                 None => AstConv::ty_of_fn(
1846                     &icx,
1847                     sig.header.unsafety,
1848                     sig.header.abi,
1849                     &sig.decl,
1850                     &generics.params[..],
1851                     Some(ident.span),
1852                 ),
1853             }
1854         }
1855
1856         TraitItem(hir::TraitItem {
1857             kind: TraitItemKind::Method(FnSig { header, decl }, _),
1858             ident,
1859             generics,
1860             ..
1861         }) => AstConv::ty_of_fn(
1862             &icx,
1863             header.unsafety,
1864             header.abi,
1865             decl,
1866             &generics.params[..],
1867             Some(ident.span),
1868         ),
1869
1870         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
1871             let abi = tcx.hir().get_foreign_abi(hir_id);
1872             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1873         }
1874
1875         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1876             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1877             let inputs =
1878                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1879             ty::Binder::bind(tcx.mk_fn_sig(
1880                 inputs,
1881                 ty,
1882                 false,
1883                 hir::Unsafety::Normal,
1884                 abi::Abi::Rust,
1885             ))
1886         }
1887
1888         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1889             // Closure signatures are not like other function
1890             // signatures and cannot be accessed through `fn_sig`. For
1891             // example, a closure signature excludes the `self`
1892             // argument. In any case they are embedded within the
1893             // closure type as part of the `ClosureSubsts`.
1894             //
1895             // To get
1896             // the signature of a closure, you should use the
1897             // `closure_sig` method on the `ClosureSubsts`:
1898             //
1899             //    closure_substs.sig(def_id, tcx)
1900             //
1901             // or, inside of an inference context, you can use
1902             //
1903             //    infcx.closure_sig(def_id, closure_substs)
1904             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1905         }
1906
1907         x => {
1908             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1909         }
1910     }
1911 }
1912
1913 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1914     let icx = ItemCtxt::new(tcx, def_id);
1915
1916     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1917     match tcx.hir().expect_item(hir_id).kind {
1918         hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1919             opt_trait_ref.as_ref().map(|ast_trait_ref| {
1920                 let selfty = tcx.type_of(def_id);
1921                 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1922             })
1923         }
1924         _ => bug!(),
1925     }
1926 }
1927
1928 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1929     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1930     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1931     let item = tcx.hir().expect_item(hir_id);
1932     match &item.kind {
1933         hir::ItemKind::Impl(_, hir::ImplPolarity::Negative, ..) => {
1934             if is_rustc_reservation {
1935                 tcx.sess.span_err(item.span, "reservation impls can't be negative");
1936             }
1937             ty::ImplPolarity::Negative
1938         }
1939         hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, None, _, _) => {
1940             if is_rustc_reservation {
1941                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1942             }
1943             ty::ImplPolarity::Positive
1944         }
1945         hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, Some(_tr), _, _) => {
1946             if is_rustc_reservation {
1947                 ty::ImplPolarity::Reservation
1948             } else {
1949                 ty::ImplPolarity::Positive
1950             }
1951         }
1952         ref item => bug!("impl_polarity: {:?} not an impl", item),
1953     }
1954 }
1955
1956 /// Returns the early-bound lifetimes declared in this generics
1957 /// listing. For anything other than fns/methods, this is just all
1958 /// the lifetimes that are declared. For fns or methods, we have to
1959 /// screen out those that do not appear in any where-clauses etc using
1960 /// `resolve_lifetime::early_bound_lifetimes`.
1961 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1962     tcx: TyCtxt<'tcx>,
1963     generics: &'a hir::Generics<'a>,
1964 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1965     generics.params.iter().filter(move |param| match param.kind {
1966         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1967         _ => false,
1968     })
1969 }
1970
1971 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1972 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1973 /// inferred constraints concerning which regions outlive other regions.
1974 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1975     debug!("predicates_defined_on({:?})", def_id);
1976     let mut result = tcx.explicit_predicates_of(def_id);
1977     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1978     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1979     if !inferred_outlives.is_empty() {
1980         debug!(
1981             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1982             def_id, inferred_outlives,
1983         );
1984         if result.predicates.is_empty() {
1985             result.predicates = inferred_outlives;
1986         } else {
1987             result.predicates = tcx
1988                 .arena
1989                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1990         }
1991     }
1992     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1993     result
1994 }
1995
1996 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1997 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1998 /// `Self: Trait` predicates for traits.
1999 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2000     let mut result = tcx.predicates_defined_on(def_id);
2001
2002     if tcx.is_trait(def_id) {
2003         // For traits, add `Self: Trait` predicate. This is
2004         // not part of the predicates that a user writes, but it
2005         // is something that one must prove in order to invoke a
2006         // method or project an associated type.
2007         //
2008         // In the chalk setup, this predicate is not part of the
2009         // "predicates" for a trait item. But it is useful in
2010         // rustc because if you directly (e.g.) invoke a trait
2011         // method like `Trait::method(...)`, you must naturally
2012         // prove that the trait applies to the types that were
2013         // used, and adding the predicate into this list ensures
2014         // that this is done.
2015         let span = tcx.def_span(def_id);
2016         result.predicates =
2017             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2018                 ty::TraitRef::identity(tcx, def_id).to_predicate(),
2019                 span,
2020             ))));
2021     }
2022     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2023     result
2024 }
2025
2026 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2027 /// N.B., this does not include any implied/inferred constraints.
2028 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2029     use rustc_data_structures::fx::FxHashSet;
2030     use rustc_hir::*;
2031
2032     debug!("explicit_predicates_of(def_id={:?})", def_id);
2033
2034     /// A data structure with unique elements, which preserves order of insertion.
2035     /// Preserving the order of insertion is important here so as not to break
2036     /// compile-fail UI tests.
2037     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2038     struct UniquePredicates<'tcx> {
2039         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2040         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2041     }
2042
2043     impl<'tcx> UniquePredicates<'tcx> {
2044         fn new() -> Self {
2045             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
2046         }
2047
2048         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2049             if self.uniques.insert(value) {
2050                 self.predicates.push(value);
2051             }
2052         }
2053
2054         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2055             for value in iter {
2056                 self.push(value);
2057             }
2058         }
2059     }
2060
2061     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2062     let node = tcx.hir().get(hir_id);
2063
2064     let mut is_trait = None;
2065     let mut is_default_impl_trait = None;
2066
2067     let icx = ItemCtxt::new(tcx, def_id);
2068
2069     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2070
2071     let mut predicates = UniquePredicates::new();
2072
2073     let ast_generics = match node {
2074         Node::TraitItem(item) => &item.generics,
2075
2076         Node::ImplItem(item) => match item.kind {
2077             ImplItemKind::OpaqueTy(ref bounds) => {
2078                 ty::print::with_no_queries(|| {
2079                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2080                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2081                     debug!(
2082                         "explicit_predicates_of({:?}): created opaque type {:?}",
2083                         def_id, opaque_ty
2084                     );
2085
2086                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2087                     let bounds = AstConv::compute_bounds(
2088                         &icx,
2089                         opaque_ty,
2090                         bounds,
2091                         SizedByDefault::Yes,
2092                         tcx.def_span(def_id),
2093                     );
2094
2095                     predicates.extend(bounds.predicates(tcx, opaque_ty));
2096                     &item.generics
2097                 })
2098             }
2099             _ => &item.generics,
2100         },
2101
2102         Node::Item(item) => {
2103             match item.kind {
2104                 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
2105                     if defaultness.is_default() {
2106                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2107                     }
2108                     generics
2109                 }
2110                 ItemKind::Fn(.., ref generics, _)
2111                 | ItemKind::TyAlias(_, ref generics)
2112                 | ItemKind::Enum(_, ref generics)
2113                 | ItemKind::Struct(_, ref generics)
2114                 | ItemKind::Union(_, ref generics) => generics,
2115
2116                 ItemKind::Trait(_, _, ref generics, .., items) => {
2117                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2118                     generics
2119                 }
2120                 ItemKind::TraitAlias(ref generics, _) => {
2121                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
2122                     generics
2123                 }
2124                 ItemKind::OpaqueTy(OpaqueTy {
2125                     ref bounds,
2126                     impl_trait_fn,
2127                     ref generics,
2128                     origin: _,
2129                 }) => {
2130                     let bounds_predicates = ty::print::with_no_queries(|| {
2131                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
2132                         let opaque_ty = tcx.mk_opaque(def_id, substs);
2133
2134                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2135                         let bounds = AstConv::compute_bounds(
2136                             &icx,
2137                             opaque_ty,
2138                             bounds,
2139                             SizedByDefault::Yes,
2140                             tcx.def_span(def_id),
2141                         );
2142
2143                         bounds.predicates(tcx, opaque_ty)
2144                     });
2145                     if impl_trait_fn.is_some() {
2146                         // opaque types
2147                         return ty::GenericPredicates {
2148                             parent: None,
2149                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2150                         };
2151                     } else {
2152                         // named opaque types
2153                         predicates.extend(bounds_predicates);
2154                         generics
2155                     }
2156                 }
2157
2158                 _ => NO_GENERICS,
2159             }
2160         }
2161
2162         Node::ForeignItem(item) => match item.kind {
2163             ForeignItemKind::Static(..) => NO_GENERICS,
2164             ForeignItemKind::Fn(_, _, ref generics) => generics,
2165             ForeignItemKind::Type => NO_GENERICS,
2166         },
2167
2168         _ => NO_GENERICS,
2169     };
2170
2171     let generics = tcx.generics_of(def_id);
2172     let parent_count = generics.parent_count as u32;
2173     let has_own_self = generics.has_self && parent_count == 0;
2174
2175     // Below we'll consider the bounds on the type parameters (including `Self`)
2176     // and the explicit where-clauses, but to get the full set of predicates
2177     // on a trait we need to add in the supertrait bounds and bounds found on
2178     // associated types.
2179     if let Some((_trait_ref, _)) = is_trait {
2180         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2181     }
2182
2183     // In default impls, we can assume that the self type implements
2184     // the trait. So in:
2185     //
2186     //     default impl Foo for Bar { .. }
2187     //
2188     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2189     // (see below). Recall that a default impl is not itself an impl, but rather a
2190     // set of defaults that can be incorporated into another impl.
2191     if let Some(trait_ref) = is_default_impl_trait {
2192         predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2193     }
2194
2195     // Collect the region predicates that were declared inline as
2196     // well. In the case of parameters declared on a fn or method, we
2197     // have to be careful to only iterate over early-bound regions.
2198     let mut index = parent_count + has_own_self as u32;
2199     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2200         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2201             def_id: tcx.hir().local_def_id(param.hir_id),
2202             index,
2203             name: param.name.ident().name,
2204         }));
2205         index += 1;
2206
2207         match param.kind {
2208             GenericParamKind::Lifetime { .. } => {
2209                 param.bounds.iter().for_each(|bound| match bound {
2210                     hir::GenericBound::Outlives(lt) => {
2211                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2212                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2213                         predicates.push((outlives.to_predicate(), lt.span));
2214                     }
2215                     _ => bug!(),
2216                 });
2217             }
2218             _ => bug!(),
2219         }
2220     }
2221
2222     // Collect the predicates that were written inline by the user on each
2223     // type parameter (e.g., `<T: Foo>`).
2224     for param in ast_generics.params {
2225         if let GenericParamKind::Type { .. } = param.kind {
2226             let name = param.name.ident().name;
2227             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2228             index += 1;
2229
2230             let sized = SizedByDefault::Yes;
2231             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2232             predicates.extend(bounds.predicates(tcx, param_ty));
2233         }
2234     }
2235
2236     // Add in the bounds that appear in the where-clause.
2237     let where_clause = &ast_generics.where_clause;
2238     for predicate in where_clause.predicates {
2239         match predicate {
2240             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2241                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2242
2243                 // Keep the type around in a dummy predicate, in case of no bounds.
2244                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2245                 // is still checked for WF.
2246                 if bound_pred.bounds.is_empty() {
2247                     if let ty::Param(_) = ty.kind {
2248                         // This is a `where T:`, which can be in the HIR from the
2249                         // transformation that moves `?Sized` to `T`'s declaration.
2250                         // We can skip the predicate because type parameters are
2251                         // trivially WF, but also we *should*, to avoid exposing
2252                         // users who never wrote `where Type:,` themselves, to
2253                         // compiler/tooling bugs from not handling WF predicates.
2254                     } else {
2255                         let span = bound_pred.bounded_ty.span;
2256                         let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2257                         predicates.push((
2258                             ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)),
2259                             span,
2260                         ));
2261                     }
2262                 }
2263
2264                 for bound in bound_pred.bounds.iter() {
2265                     match bound {
2266                         &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2267                             let mut bounds = Bounds::default();
2268                             let _ = AstConv::instantiate_poly_trait_ref(
2269                                 &icx,
2270                                 poly_trait_ref,
2271                                 ty,
2272                                 &mut bounds,
2273                             );
2274                             predicates.extend(bounds.predicates(tcx, ty));
2275                         }
2276
2277                         &hir::GenericBound::Outlives(ref lifetime) => {
2278                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2279                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2280                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2281                         }
2282                     }
2283                 }
2284             }
2285
2286             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2287                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2288                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2289                     let (r2, span) = match bound {
2290                         hir::GenericBound::Outlives(lt) => {
2291                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2292                         }
2293                         _ => bug!(),
2294                     };
2295                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2296
2297                     (ty::Predicate::RegionOutlives(pred), span)
2298                 }))
2299             }
2300
2301             &hir::WherePredicate::EqPredicate(..) => {
2302                 // FIXME(#20041)
2303             }
2304         }
2305     }
2306
2307     // Add predicates from associated type bounds.
2308     if let Some((self_trait_ref, trait_items)) = is_trait {
2309         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2310             associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2311         }))
2312     }
2313
2314     let mut predicates = predicates.predicates;
2315
2316     // Subtle: before we store the predicates into the tcx, we
2317     // sort them so that predicates like `T: Foo<Item=U>` come
2318     // before uses of `U`.  This avoids false ambiguity errors
2319     // in trait checking. See `setup_constraining_predicates`
2320     // for details.
2321     if let Node::Item(&Item { kind: ItemKind::Impl(..), .. }) = node {
2322         let self_ty = tcx.type_of(def_id);
2323         let trait_ref = tcx.impl_trait_ref(def_id);
2324         cgp::setup_constraining_predicates(
2325             tcx,
2326             &mut predicates,
2327             trait_ref,
2328             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2329         );
2330     }
2331
2332     let result = ty::GenericPredicates {
2333         parent: generics.parent,
2334         predicates: tcx.arena.alloc_from_iter(predicates),
2335     };
2336     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2337     result
2338 }
2339
2340 fn associated_item_predicates(
2341     tcx: TyCtxt<'tcx>,
2342     def_id: DefId,
2343     self_trait_ref: ty::TraitRef<'tcx>,
2344     trait_item_ref: &hir::TraitItemRef,
2345 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2346     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2347     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2348     let bounds = match trait_item.kind {
2349         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2350         _ => return Vec::new(),
2351     };
2352
2353     let is_gat = !tcx.generics_of(item_def_id).params.is_empty();
2354
2355     let mut had_error = false;
2356
2357     let mut unimplemented_error = |arg_kind: &str| {
2358         if !had_error {
2359             tcx.sess
2360                 .struct_span_err(
2361                     trait_item.span,
2362                     &format!("{}-generic associated types are not yet implemented", arg_kind),
2363                 )
2364                 .note("for more information, see https://github.com/rust-lang/rust/issues/44265")
2365                 .emit();
2366             had_error = true;
2367         }
2368     };
2369
2370     let mk_bound_param = |param: &ty::GenericParamDef, _: &_| {
2371         match param.kind {
2372             ty::GenericParamDefKind::Lifetime => tcx
2373                 .mk_region(ty::RegionKind::ReLateBound(
2374                     ty::INNERMOST,
2375                     ty::BoundRegion::BrNamed(param.def_id, param.name),
2376                 ))
2377                 .into(),
2378             // FIXME(generic_associated_types): Use bound types and constants
2379             // once they are handled by the trait system.
2380             ty::GenericParamDefKind::Type { .. } => {
2381                 unimplemented_error("type");
2382                 tcx.types.err.into()
2383             }
2384             ty::GenericParamDefKind::Const => {
2385                 unimplemented_error("const");
2386                 tcx.consts.err.into()
2387             }
2388         }
2389     };
2390
2391     let bound_substs = if is_gat {
2392         // Given:
2393         //
2394         // trait X<'a, B, const C: usize> {
2395         //     type T<'d, E, const F: usize>: Default;
2396         // }
2397         //
2398         // We need to create predicates on the trait:
2399         //
2400         // for<'d, E, const F: usize>
2401         // <Self as X<'a, B, const C: usize>>::T<'d, E, const F: usize>: Sized + Default
2402         //
2403         // We substitute escaping bound parameters for the generic
2404         // arguments to the associated type which are then bound by
2405         // the `Binder` around the the predicate.
2406         //
2407         // FIXME(generic_associated_types): Currently only lifetimes are handled.
2408         self_trait_ref.substs.extend_to(tcx, item_def_id, mk_bound_param)
2409     } else {
2410         self_trait_ref.substs
2411     };
2412
2413     let assoc_ty = tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id), bound_substs);
2414
2415     let bounds = AstConv::compute_bounds(
2416         &ItemCtxt::new(tcx, def_id),
2417         assoc_ty,
2418         bounds,
2419         SizedByDefault::Yes,
2420         trait_item.span,
2421     );
2422
2423     let predicates = bounds.predicates(tcx, assoc_ty);
2424
2425     if is_gat {
2426         // We use shifts to get the regions that we're substituting to
2427         // be bound by the binders in the `Predicate`s rather that
2428         // escaping.
2429         let shifted_in = ty::fold::shift_vars(tcx, &predicates, 1);
2430         let substituted = shifted_in.subst(tcx, bound_substs);
2431         ty::fold::shift_out_vars(tcx, &substituted, 1)
2432     } else {
2433         predicates
2434     }
2435 }
2436
2437 /// Converts a specific `GenericBound` from the AST into a set of
2438 /// predicates that apply to the self type. A vector is returned
2439 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2440 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2441 /// and `<T as Bar>::X == i32`).
2442 fn predicates_from_bound<'tcx>(
2443     astconv: &dyn AstConv<'tcx>,
2444     param_ty: Ty<'tcx>,
2445     bound: &'tcx hir::GenericBound<'tcx>,
2446 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2447     match *bound {
2448         hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2449             let mut bounds = Bounds::default();
2450             let _ = astconv.instantiate_poly_trait_ref(tr, param_ty, &mut bounds);
2451             bounds.predicates(astconv.tcx(), param_ty)
2452         }
2453         hir::GenericBound::Outlives(ref lifetime) => {
2454             let region = astconv.ast_region_to_region(lifetime, None);
2455             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2456             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2457         }
2458         hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2459     }
2460 }
2461
2462 fn compute_sig_of_foreign_fn_decl<'tcx>(
2463     tcx: TyCtxt<'tcx>,
2464     def_id: DefId,
2465     decl: &'tcx hir::FnDecl<'tcx>,
2466     abi: abi::Abi,
2467 ) -> ty::PolyFnSig<'tcx> {
2468     let unsafety = if abi == abi::Abi::RustIntrinsic {
2469         intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2470     } else {
2471         hir::Unsafety::Unsafe
2472     };
2473     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
2474
2475     // Feature gate SIMD types in FFI, since I am not sure that the
2476     // ABIs are handled at all correctly. -huonw
2477     if abi != abi::Abi::RustIntrinsic
2478         && abi != abi::Abi::PlatformIntrinsic
2479         && !tcx.features().simd_ffi
2480     {
2481         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2482             if ty.is_simd() {
2483                 tcx.sess
2484                     .struct_span_err(
2485                         ast_ty.span,
2486                         &format!(
2487                             "use of SIMD type `{}` in FFI is highly experimental and \
2488                             may result in invalid code",
2489                             tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2490                         ),
2491                     )
2492                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2493                     .emit();
2494             }
2495         };
2496         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2497             check(&input, ty)
2498         }
2499         if let hir::FunctionRetTy::Return(ref ty) = decl.output {
2500             check(&ty, *fty.output().skip_binder())
2501         }
2502     }
2503
2504     fty
2505 }
2506
2507 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2508     match tcx.hir().get_if_local(def_id) {
2509         Some(Node::ForeignItem(..)) => true,
2510         Some(_) => false,
2511         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2512     }
2513 }
2514
2515 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2516     match tcx.hir().get_if_local(def_id) {
2517         Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. }))
2518         | Some(Node::ForeignItem(&hir::ForeignItem {
2519             kind: hir::ForeignItemKind::Static(_, mutbl),
2520             ..
2521         })) => Some(mutbl),
2522         Some(_) => None,
2523         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2524     }
2525 }
2526
2527 fn from_target_feature(
2528     tcx: TyCtxt<'_>,
2529     id: DefId,
2530     attr: &ast::Attribute,
2531     whitelist: &FxHashMap<String, Option<Symbol>>,
2532     target_features: &mut Vec<Symbol>,
2533 ) {
2534     let list = match attr.meta_item_list() {
2535         Some(list) => list,
2536         None => return,
2537     };
2538     let bad_item = |span| {
2539         let msg = "malformed `target_feature` attribute input";
2540         let code = "enable = \"..\"".to_owned();
2541         tcx.sess
2542             .struct_span_err(span, &msg)
2543             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2544             .emit();
2545     };
2546     let rust_features = tcx.features();
2547     for item in list {
2548         // Only `enable = ...` is accepted in the meta-item list.
2549         if !item.check_name(sym::enable) {
2550             bad_item(item.span());
2551             continue;
2552         }
2553
2554         // Must be of the form `enable = "..."` (a string).
2555         let value = match item.value_str() {
2556             Some(value) => value,
2557             None => {
2558                 bad_item(item.span());
2559                 continue;
2560             }
2561         };
2562
2563         // We allow comma separation to enable multiple features.
2564         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2565             // Only allow whitelisted features per platform.
2566             let feature_gate = match whitelist.get(feature) {
2567                 Some(g) => g,
2568                 None => {
2569                     let msg =
2570                         format!("the feature named `{}` is not valid for this target", feature);
2571                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2572                     err.span_label(
2573                         item.span(),
2574                         format!("`{}` is not valid for this target", feature),
2575                     );
2576                     if feature.starts_with("+") {
2577                         let valid = whitelist.contains_key(&feature[1..]);
2578                         if valid {
2579                             err.help("consider removing the leading `+` in the feature name");
2580                         }
2581                     }
2582                     err.emit();
2583                     return None;
2584                 }
2585             };
2586
2587             // Only allow features whose feature gates have been enabled.
2588             let allowed = match feature_gate.as_ref().map(|s| *s) {
2589                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2590                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2591                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2592                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2593                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2594                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2595                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2596                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2597                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2598                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2599                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2600                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2601                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2602                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2603                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2604                 Some(name) => bug!("unknown target feature gate {}", name),
2605                 None => true,
2606             };
2607             if !allowed && id.is_local() {
2608                 feature_gate::feature_err(
2609                     &tcx.sess.parse_sess,
2610                     feature_gate.unwrap(),
2611                     item.span(),
2612                     &format!("the target feature `{}` is currently unstable", feature),
2613                 )
2614                 .emit();
2615             }
2616             Some(Symbol::intern(feature))
2617         }));
2618     }
2619 }
2620
2621 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2622     use rustc::mir::mono::Linkage::*;
2623
2624     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2625     // applicable to variable declarations and may not really make sense for
2626     // Rust code in the first place but whitelist them anyway and trust that
2627     // the user knows what s/he's doing. Who knows, unanticipated use cases
2628     // may pop up in the future.
2629     //
2630     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2631     // and don't have to be, LLVM treats them as no-ops.
2632     match name {
2633         "appending" => Appending,
2634         "available_externally" => AvailableExternally,
2635         "common" => Common,
2636         "extern_weak" => ExternalWeak,
2637         "external" => External,
2638         "internal" => Internal,
2639         "linkonce" => LinkOnceAny,
2640         "linkonce_odr" => LinkOnceODR,
2641         "private" => Private,
2642         "weak" => WeakAny,
2643         "weak_odr" => WeakODR,
2644         _ => {
2645             let span = tcx.hir().span_if_local(def_id);
2646             if let Some(span) = span {
2647                 tcx.sess.span_fatal(span, "invalid linkage specified")
2648             } else {
2649                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2650             }
2651         }
2652     }
2653 }
2654
2655 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2656     let attrs = tcx.get_attrs(id);
2657
2658     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2659
2660     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2661
2662     let mut inline_span = None;
2663     let mut link_ordinal_span = None;
2664     for attr in attrs.iter() {
2665         if attr.check_name(sym::cold) {
2666             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2667         } else if attr.check_name(sym::rustc_allocator) {
2668             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2669         } else if attr.check_name(sym::unwind) {
2670             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2671         } else if attr.check_name(sym::ffi_returns_twice) {
2672             if tcx.is_foreign_item(id) {
2673                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2674             } else {
2675                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2676                 struct_span_err!(
2677                     tcx.sess,
2678                     attr.span,
2679                     E0724,
2680                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2681                 )
2682                 .emit();
2683             }
2684         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2685             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2686         } else if attr.check_name(sym::naked) {
2687             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2688         } else if attr.check_name(sym::no_mangle) {
2689             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2690         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2691             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2692         } else if attr.check_name(sym::no_debug) {
2693             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2694         } else if attr.check_name(sym::used) {
2695             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2696         } else if attr.check_name(sym::thread_local) {
2697             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2698         } else if attr.check_name(sym::track_caller) {
2699             if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2700                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2701                     .emit();
2702             }
2703             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2704         } else if attr.check_name(sym::export_name) {
2705             if let Some(s) = attr.value_str() {
2706                 if s.as_str().contains("\0") {
2707                     // `#[export_name = ...]` will be converted to a null-terminated string,
2708                     // so it may not contain any null characters.
2709                     struct_span_err!(
2710                         tcx.sess,
2711                         attr.span,
2712                         E0648,
2713                         "`export_name` may not contain null characters"
2714                     )
2715                     .emit();
2716                 }
2717                 codegen_fn_attrs.export_name = Some(s);
2718             }
2719         } else if attr.check_name(sym::target_feature) {
2720             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2721                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2722                 tcx.sess
2723                     .struct_span_err(attr.span, msg)
2724                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2725                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2726                     .emit();
2727             }
2728             from_target_feature(tcx, id, attr, &whitelist, &mut codegen_fn_attrs.target_features);
2729         } else if attr.check_name(sym::linkage) {
2730             if let Some(val) = attr.value_str() {
2731                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2732             }
2733         } else if attr.check_name(sym::link_section) {
2734             if let Some(val) = attr.value_str() {
2735                 if val.as_str().bytes().any(|b| b == 0) {
2736                     let msg = format!(
2737                         "illegal null byte in link_section \
2738                          value: `{}`",
2739                         &val
2740                     );
2741                     tcx.sess.span_err(attr.span, &msg);
2742                 } else {
2743                     codegen_fn_attrs.link_section = Some(val);
2744                 }
2745             }
2746         } else if attr.check_name(sym::link_name) {
2747             codegen_fn_attrs.link_name = attr.value_str();
2748         } else if attr.check_name(sym::link_ordinal) {
2749             link_ordinal_span = Some(attr.span);
2750             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2751                 codegen_fn_attrs.link_ordinal = ordinal;
2752             }
2753         }
2754     }
2755
2756     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2757         if !attr.has_name(sym::inline) {
2758             return ia;
2759         }
2760         match attr.meta().map(|i| i.kind) {
2761             Some(MetaItemKind::Word) => {
2762                 mark_used(attr);
2763                 InlineAttr::Hint
2764             }
2765             Some(MetaItemKind::List(ref items)) => {
2766                 mark_used(attr);
2767                 inline_span = Some(attr.span);
2768                 if items.len() != 1 {
2769                     span_err!(tcx.sess.diagnostic(), attr.span, E0534, "expected one argument");
2770                     InlineAttr::None
2771                 } else if list_contains_name(&items[..], sym::always) {
2772                     InlineAttr::Always
2773                 } else if list_contains_name(&items[..], sym::never) {
2774                     InlineAttr::Never
2775                 } else {
2776                     span_err!(tcx.sess.diagnostic(), items[0].span(), E0535, "invalid argument");
2777
2778                     InlineAttr::None
2779                 }
2780             }
2781             Some(MetaItemKind::NameValue(_)) => ia,
2782             None => ia,
2783         }
2784     });
2785
2786     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2787         if !attr.has_name(sym::optimize) {
2788             return ia;
2789         }
2790         let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2791         match attr.meta().map(|i| i.kind) {
2792             Some(MetaItemKind::Word) => {
2793                 err(attr.span, "expected one argument");
2794                 ia
2795             }
2796             Some(MetaItemKind::List(ref items)) => {
2797                 mark_used(attr);
2798                 inline_span = Some(attr.span);
2799                 if items.len() != 1 {
2800                     err(attr.span, "expected one argument");
2801                     OptimizeAttr::None
2802                 } else if list_contains_name(&items[..], sym::size) {
2803                     OptimizeAttr::Size
2804                 } else if list_contains_name(&items[..], sym::speed) {
2805                     OptimizeAttr::Speed
2806                 } else {
2807                     err(items[0].span(), "invalid argument");
2808                     OptimizeAttr::None
2809                 }
2810             }
2811             Some(MetaItemKind::NameValue(_)) => ia,
2812             None => ia,
2813         }
2814     });
2815
2816     // If a function uses #[target_feature] it can't be inlined into general
2817     // purpose functions as they wouldn't have the right target features
2818     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2819     // respected.
2820
2821     if codegen_fn_attrs.target_features.len() > 0 {
2822         if codegen_fn_attrs.inline == InlineAttr::Always {
2823             if let Some(span) = inline_span {
2824                 tcx.sess.span_err(
2825                     span,
2826                     "cannot use `#[inline(always)]` with \
2827                      `#[target_feature]`",
2828                 );
2829             }
2830         }
2831     }
2832
2833     // Weak lang items have the same semantics as "std internal" symbols in the
2834     // sense that they're preserved through all our LTO passes and only
2835     // strippable by the linker.
2836     //
2837     // Additionally weak lang items have predetermined symbol names.
2838     if tcx.is_weak_lang_item(id) {
2839         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2840     }
2841     if let Some(name) = weak_lang_items::link_name(&attrs) {
2842         codegen_fn_attrs.export_name = Some(name);
2843         codegen_fn_attrs.link_name = Some(name);
2844     }
2845     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2846
2847     // Internal symbols to the standard library all have no_mangle semantics in
2848     // that they have defined symbol names present in the function name. This
2849     // also applies to weak symbols where they all have known symbol names.
2850     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2851         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2852     }
2853
2854     codegen_fn_attrs
2855 }
2856
2857 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2858     use syntax::ast::{Lit, LitIntType, LitKind};
2859     let meta_item_list = attr.meta_item_list();
2860     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2861     let sole_meta_list = match meta_item_list {
2862         Some([item]) => item.literal(),
2863         _ => None,
2864     };
2865     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2866         if *ordinal <= std::usize::MAX as u128 {
2867             Some(*ordinal as usize)
2868         } else {
2869             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2870             tcx.sess
2871                 .struct_span_err(attr.span, &msg)
2872                 .note("the value may not exceed `std::usize::MAX`")
2873                 .emit();
2874             None
2875         }
2876     } else {
2877         tcx.sess
2878             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2879             .note("an unsuffixed integer value, e.g., `1`, is expected")
2880             .emit();
2881         None
2882     }
2883 }
2884
2885 fn check_link_name_xor_ordinal(
2886     tcx: TyCtxt<'_>,
2887     codegen_fn_attrs: &CodegenFnAttrs,
2888     inline_span: Option<Span>,
2889 ) {
2890     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2891         return;
2892     }
2893     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2894     if let Some(span) = inline_span {
2895         tcx.sess.span_err(span, msg);
2896     } else {
2897         tcx.sess.err(msg);
2898     }
2899 }