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