src/librustc_typeck/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  18 use crate::check::intrinsic::intrinsic_operation_unsafety;
  19 use crate::constrained_generic_params as cgp;
  20 use crate::lint;
  21 use crate::middle::resolve_lifetime as rl;
  22 use crate::middle::weak_lang_items;
  23 use rustc::mir::mono::Linkage;
  24 use rustc::ty::query::Providers;
  25 use rustc::ty::subst::GenericArgKind;
  26 use rustc::ty::subst::{InternalSubsts, Subst};
  27 use rustc::ty::util::Discr;
  28 use rustc::ty::util::IntTypeExt;
  29 use rustc::ty::{self, AdtKind, Const, DefIdTree, ToPolyTraitRef, Ty, TyCtxt};
  30 use rustc::ty::{ReprOptions, ToPredicate};
  31 use rustc::util::captures::Captures;
  32 use rustc::util::nodemap::FxHashMap;
  33 use rustc_target::spec::abi;
  34
  35 use rustc_span::symbol::{kw, sym, Symbol};
  36 use rustc_span::{Span, DUMMY_SP};
  37 use syntax::ast;
  38 use syntax::ast::{Ident, MetaItemKind};
  39 use syntax::attr::{list_contains_name, mark_used, InlineAttr, OptimizeAttr};
  40 use syntax::feature_gate;
  41
  42 use rustc::hir::def::{CtorKind, DefKind, Res};
  43 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  44 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  45 use rustc::hir::GenericParamKind;
  46 use rustc::hir::Node;
  47 use rustc::hir::{self, CodegenFnAttrFlags, CodegenFnAttrs, Unsafety};
  48
  49 use errors::{Applicability, StashKey};
  50
  51 use rustc_error_codes::*;
  52
  53 struct OnlySelfBounds(bool);
  54
  55 ///////////////////////////////////////////////////////////////////////////
  56 // Main entry point
  57
  58 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
  59     tcx.hir().visit_item_likes_in_module(
  60         module_def_id,
  61         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  62     );
  63 }
  64
  65 pub fn provide(providers: &mut Providers<'_>) {
  66     *providers = Providers {
  67         type_of,
  68         generics_of,
  69         predicates_of,
  70         predicates_defined_on,
  71         explicit_predicates_of,
  72         super_predicates_of,
  73         type_param_predicates,
  74         trait_def,
  75         adt_def,
  76         fn_sig,
  77         impl_trait_ref,
  78         impl_polarity,
  79         is_foreign_item,
  80         static_mutability,
  81         codegen_fn_attrs,
  82         collect_mod_item_types,
  83         ..*providers
  84     };
  85 }
  86
  87 ///////////////////////////////////////////////////////////////////////////
  88
  89 /// Context specific to some particular item. This is what implements
  90 /// `AstConv`. It has information about the predicates that are defined
  91 /// on the trait. Unfortunately, this predicate information is
  92 /// available in various different forms at various points in the
  93 /// process. So we can't just store a pointer to e.g., the AST or the
  94 /// parsed ty form, we have to be more flexible. To this end, the
  95 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  96 /// `get_type_parameter_bounds` requests, drawing the information from
  97 /// the AST (`hir::Generics`), recursively.
  98 pub struct ItemCtxt<'tcx> {
  99     tcx: TyCtxt<'tcx>,
 100     item_def_id: DefId,
 101 }
 102
 103 ///////////////////////////////////////////////////////////////////////////
 104
 105 #[derive(Default)]
 106 crate struct PlaceholderHirTyCollector(crate Vec<Span>);
 107
 108 impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
 109     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
 110         NestedVisitorMap::None
 111     }
 112     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 113         if let hir::TyKind::Infer = t.kind {
 114             self.0.push(t.span);
 115         }
 116         hir::intravisit::walk_ty(self, t)
 117     }
 118 }
 119
 120 struct CollectItemTypesVisitor<'tcx> {
 121     tcx: TyCtxt<'tcx>,
 122 }
 123
 124 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 125 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 126 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 127 crate fn placeholder_type_error(
 128     tcx: TyCtxt<'tcx>,
 129     ident_span: Span,
 130     generics: &[hir::GenericParam<'_>],
 131     placeholder_types: Vec<Span>,
 132     suggest: bool,
 133 ) {
 134     if placeholder_types.is_empty() {
 135         return;
 136     }
 137     // This is the whitelist of possible parameter names that we might suggest.
 138     let possible_names = ["T", "K", "L", "A", "B", "C"];
 139     let used_names = generics
 140         .iter()
 141         .filter_map(|p| match p.name {
 142             hir::ParamName::Plain(ident) => Some(ident.name),
 143             _ => None,
 144         })
 145         .collect::<Vec<_>>();
 146
 147     let type_name = possible_names
 148         .iter()
 149         .find(|n| !used_names.contains(&Symbol::intern(n)))
 150         .unwrap_or(&"ParamName");
 151
 152     let mut sugg: Vec<_> =
 153         placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
 154     if generics.is_empty() {
 155         sugg.push((ident_span.shrink_to_hi(), format!("<{}>", type_name)));
 156     } else {
 157         sugg.push((
 158             generics.iter().last().unwrap().span.shrink_to_hi(),
 159             format!(", {}", type_name),
 160         ));
 161     }
 162     let mut err = bad_placeholder_type(tcx, placeholder_types);
 163     if suggest {
 164         err.multipart_suggestion(
 165             "use type parameters instead",
 166             sugg,
 167             Applicability::HasPlaceholders,
 168         );
 169     }
 170     err.emit();
 171 }
 172
 173 fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
 174     let (generics, suggest) = match &item.kind {
 175         hir::ItemKind::Union(_, generics)
 176         | hir::ItemKind::Enum(_, generics)
 177         | hir::ItemKind::Struct(_, generics) => (&generics.params[..], true),
 178         hir::ItemKind::TyAlias(_, generics) => (&generics.params[..], false),
 179         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 180         _ => return,
 181     };
 182
 183     let mut visitor = PlaceholderHirTyCollector::default();
 184     visitor.visit_item(item);
 185
 186     placeholder_type_error(tcx, item.ident.span, generics, visitor.0, suggest);
 187 }
 188
 189 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 190     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 191         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 192     }
 193
 194     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 195         convert_item(self.tcx, item.hir_id);
 196         reject_placeholder_type_signatures_in_item(self.tcx, item);
 197         intravisit::walk_item(self, item);
 198     }
 199
 200     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 201         for param in generics.params {
 202             match param.kind {
 203                 hir::GenericParamKind::Lifetime { .. } => {}
 204                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 205                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 206                     self.tcx.type_of(def_id);
 207                 }
 208                 hir::GenericParamKind::Type { .. } => {}
 209                 hir::GenericParamKind::Const { .. } => {
 210                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 211                     self.tcx.type_of(def_id);
 212                 }
 213             }
 214         }
 215         intravisit::walk_generics(self, generics);
 216     }
 217
 218     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 219         if let hir::ExprKind::Closure(..) = expr.kind {
 220             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 221             self.tcx.generics_of(def_id);
 222             self.tcx.type_of(def_id);
 223         }
 224         intravisit::walk_expr(self, expr);
 225     }
 226
 227     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 228         convert_trait_item(self.tcx, trait_item.hir_id);
 229         intravisit::walk_trait_item(self, trait_item);
 230     }
 231
 232     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 233         convert_impl_item(self.tcx, impl_item.hir_id);
 234         intravisit::walk_impl_item(self, impl_item);
 235     }
 236 }
 237
 238 ///////////////////////////////////////////////////////////////////////////
 239 // Utility types and common code for the above passes.
 240
 241 fn bad_placeholder_type(
 242     tcx: TyCtxt<'tcx>,
 243     mut spans: Vec<Span>,
 244 ) -> errors::DiagnosticBuilder<'tcx> {
 245     spans.sort();
 246     let mut err = struct_span_err!(
 247         tcx.sess,
 248         spans.clone(),
 249         E0121,
 250         "the type placeholder `_` is not allowed within types on item signatures",
 251     );
 252     for span in spans {
 253         err.span_label(span, "not allowed in type signatures");
 254     }
 255     err
 256 }
 257
 258 impl ItemCtxt<'tcx> {
 259     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 260         ItemCtxt { tcx, item_def_id }
 261     }
 262
 263     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty<'tcx>) -> Ty<'tcx> {
 264         AstConv::ast_ty_to_ty(self, ast_ty)
 265     }
 266 }
 267
 268 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 269     fn tcx(&self) -> TyCtxt<'tcx> {
 270         self.tcx
 271     }
 272
 273     fn item_def_id(&self) -> Option<DefId> {
 274         Some(self.item_def_id)
 275     }
 276
 277     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
 278         self.tcx.at(span).type_param_predicates((self.item_def_id, def_id))
 279     }
 280
 281     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 282         None
 283     }
 284
 285     fn allow_ty_infer(&self) -> bool {
 286         false
 287     }
 288
 289     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 290         self.tcx().sess.delay_span_bug(span, "bad placeholder type");
 291         self.tcx().types.err
 292     }
 293
 294     fn ct_infer(
 295         &self,
 296         _: Ty<'tcx>,
 297         _: Option<&ty::GenericParamDef>,
 298         span: Span,
 299     ) -> &'tcx Const<'tcx> {
 300         bad_placeholder_type(self.tcx(), vec![span]).emit();
 301
 302         self.tcx().consts.err
 303     }
 304
 305     fn projected_ty_from_poly_trait_ref(
 306         &self,
 307         span: Span,
 308         item_def_id: DefId,
 309         item_segment: &hir::PathSegment<'_>,
 310         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 311     ) -> Ty<'tcx> {
 312         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 313             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 314                 self,
 315                 self.tcx,
 316                 span,
 317                 item_def_id,
 318                 item_segment,
 319                 trait_ref.substs,
 320             );
 321             self.tcx().mk_projection(item_def_id, item_substs)
 322         } else {
 323             // There are no late-bound regions; we can just ignore the binder.
 324             span_err!(
 325                 self.tcx().sess,
 326                 span,
 327                 E0212,
 328                 "cannot extract an associated type from a higher-ranked trait bound \
 329                  in this context"
 330             );
 331             self.tcx().types.err
 332         }
 333     }
 334
 335     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 336         // Types in item signatures are not normalized to avoid undue dependencies.
 337         ty
 338     }
 339
 340     fn set_tainted_by_errors(&self) {
 341         // There's no obvious place to track this, so just let it go.
 342     }
 343
 344     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 345         // There's no place to record types from signatures?
 346     }
 347 }
 348
 349 /// Returns the predicates defined on `item_def_id` of the form
 350 /// `X: Foo` where `X` is the type parameter `def_id`.
 351 fn type_param_predicates(
 352     tcx: TyCtxt<'_>,
 353     (item_def_id, def_id): (DefId, DefId),
 354 ) -> ty::GenericPredicates<'_> {
 355     use rustc::hir::*;
 356
 357     // In the AST, bounds can derive from two places. Either
 358     // written inline like `<T: Foo>` or in a where-clause like
 359     // `where T: Foo`.
 360
 361     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 362     let param_owner = tcx.hir().ty_param_owner(param_id);
 363     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 364     let generics = tcx.generics_of(param_owner_def_id);
 365     let index = generics.param_def_id_to_index[&def_id];
 366     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 367
 368     // Don't look for bounds where the type parameter isn't in scope.
 369     let parent =
 370         if item_def_id == param_owner_def_id { None } else { tcx.generics_of(item_def_id).parent };
 371
 372     let mut result = parent
 373         .map(|parent| {
 374             let icx = ItemCtxt::new(tcx, parent);
 375             icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 376         })
 377         .unwrap_or_default();
 378     let mut extend = None;
 379
 380     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 381     let ast_generics = match tcx.hir().get(item_hir_id) {
 382         Node::TraitItem(item) => &item.generics,
 383
 384         Node::ImplItem(item) => &item.generics,
 385
 386         Node::Item(item) => {
 387             match item.kind {
 388                 ItemKind::Fn(.., ref generics, _)
 389                 | ItemKind::Impl(_, _, _, ref generics, ..)
 390                 | ItemKind::TyAlias(_, ref generics)
 391                 | ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. })
 392                 | ItemKind::Enum(_, ref generics)
 393                 | ItemKind::Struct(_, ref generics)
 394                 | ItemKind::Union(_, ref generics) => generics,
 395                 ItemKind::Trait(_, _, ref generics, ..) => {
 396                     // Implied `Self: Trait` and supertrait bounds.
 397                     if param_id == item_hir_id {
 398                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 399                         extend = Some((identity_trait_ref.to_predicate(), item.span));
 400                     }
 401                     generics
 402                 }
 403                 _ => return result,
 404             }
 405         }
 406
 407         Node::ForeignItem(item) => match item.kind {
 408             ForeignItemKind::Fn(_, _, ref generics) => generics,
 409             _ => return result,
 410         },
 411
 412         _ => return result,
 413     };
 414
 415     let icx = ItemCtxt::new(tcx, item_def_id);
 416     let extra_predicates = extend.into_iter().chain(
 417         icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
 418             .into_iter()
 419             .filter(|(predicate, _)| match predicate {
 420                 ty::Predicate::Trait(ref data) => data.skip_binder().self_ty().is_param(index),
 421                 _ => false,
 422             }),
 423     );
 424     result.predicates =
 425         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 426     result
 427 }
 428
 429 impl ItemCtxt<'tcx> {
 430     /// Finds bounds from `hir::Generics`. This requires scanning through the
 431     /// AST. We do this to avoid having to convert *all* the bounds, which
 432     /// would create artificial cycles. Instead, we can only convert the
 433     /// bounds for a type parameter `X` if `X::Foo` is used.
 434     fn type_parameter_bounds_in_generics(
 435         &self,
 436         ast_generics: &'tcx hir::Generics<'tcx>,
 437         param_id: hir::HirId,
 438         ty: Ty<'tcx>,
 439         only_self_bounds: OnlySelfBounds,
 440     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 441         let from_ty_params = ast_generics
 442             .params
 443             .iter()
 444             .filter_map(|param| match param.kind {
 445                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 446                 _ => None,
 447             })
 448             .flat_map(|bounds| bounds.iter())
 449             .flat_map(|b| predicates_from_bound(self, ty, b));
 450
 451         let from_where_clauses = ast_generics
 452             .where_clause
 453             .predicates
 454             .iter()
 455             .filter_map(|wp| match *wp {
 456                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 457                 _ => None,
 458             })
 459             .flat_map(|bp| {
 460                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 461                     Some(ty)
 462                 } else if !only_self_bounds.0 {
 463                     Some(self.to_ty(&bp.bounded_ty))
 464                 } else {
 465                     None
 466                 };
 467                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 468             })
 469             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
 470
 471         from_ty_params.chain(from_where_clauses).collect()
 472     }
 473 }
 474
 475 /// Tests whether this is the AST for a reference to the type
 476 /// parameter with ID `param_id`. We use this so as to avoid running
 477 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 478 /// conversion of the type to avoid inducing unnecessary cycles.
 479 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty<'_>, param_id: hir::HirId) -> bool {
 480     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
 481         match path.res {
 482             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 483                 def_id == tcx.hir().local_def_id(param_id)
 484             }
 485             _ => false,
 486         }
 487     } else {
 488         false
 489     }
 490 }
 491
 492 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 493     let it = tcx.hir().expect_item(item_id);
 494     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 495     let def_id = tcx.hir().local_def_id(item_id);
 496     match it.kind {
 497         // These don't define types.
 498         hir::ItemKind::ExternCrate(_)
 499         | hir::ItemKind::Use(..)
 500         | hir::ItemKind::Mod(_)
 501         | hir::ItemKind::GlobalAsm(_) => {}
 502         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 503             for item in foreign_mod.items {
 504                 let def_id = tcx.hir().local_def_id(item.hir_id);
 505                 tcx.generics_of(def_id);
 506                 tcx.type_of(def_id);
 507                 tcx.predicates_of(def_id);
 508                 if let hir::ForeignItemKind::Fn(..) = item.kind {
 509                     tcx.fn_sig(def_id);
 510                 }
 511             }
 512         }
 513         hir::ItemKind::Enum(ref enum_definition, _) => {
 514             tcx.generics_of(def_id);
 515             tcx.type_of(def_id);
 516             tcx.predicates_of(def_id);
 517             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 518         }
 519         hir::ItemKind::Impl(..) => {
 520             tcx.generics_of(def_id);
 521             tcx.type_of(def_id);
 522             tcx.impl_trait_ref(def_id);
 523             tcx.predicates_of(def_id);
 524         }
 525         hir::ItemKind::Trait(..) => {
 526             tcx.generics_of(def_id);
 527             tcx.trait_def(def_id);
 528             tcx.at(it.span).super_predicates_of(def_id);
 529             tcx.predicates_of(def_id);
 530         }
 531         hir::ItemKind::TraitAlias(..) => {
 532             tcx.generics_of(def_id);
 533             tcx.at(it.span).super_predicates_of(def_id);
 534             tcx.predicates_of(def_id);
 535         }
 536         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 537             tcx.generics_of(def_id);
 538             tcx.type_of(def_id);
 539             tcx.predicates_of(def_id);
 540
 541             for f in struct_def.fields() {
 542                 let def_id = tcx.hir().local_def_id(f.hir_id);
 543                 tcx.generics_of(def_id);
 544                 tcx.type_of(def_id);
 545                 tcx.predicates_of(def_id);
 546             }
 547
 548             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 549                 convert_variant_ctor(tcx, ctor_hir_id);
 550             }
 551         }
 552
 553         // Desugared from `impl Trait`, so visited by the function's return type.
 554         hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(_), .. }) => {}
 555
 556         hir::ItemKind::OpaqueTy(..)
 557         | hir::ItemKind::TyAlias(..)
 558         | hir::ItemKind::Static(..)
 559         | hir::ItemKind::Const(..)
 560         | hir::ItemKind::Fn(..) => {
 561             tcx.generics_of(def_id);
 562             tcx.type_of(def_id);
 563             tcx.predicates_of(def_id);
 564             if let hir::ItemKind::Fn(..) = it.kind {
 565                 tcx.fn_sig(def_id);
 566             }
 567         }
 568     }
 569 }
 570
 571 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 572     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 573     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 574     tcx.generics_of(def_id);
 575
 576     match trait_item.kind {
 577         hir::TraitItemKind::Const(..)
 578         | hir::TraitItemKind::Type(_, Some(_))
 579         | hir::TraitItemKind::Method(..) => {
 580             tcx.type_of(def_id);
 581             if let hir::TraitItemKind::Method(..) = trait_item.kind {
 582                 tcx.fn_sig(def_id);
 583             }
 584         }
 585
 586         hir::TraitItemKind::Type(_, None) => {}
 587     };
 588
 589     tcx.predicates_of(def_id);
 590 }
 591
 592 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 593     let def_id = tcx.hir().local_def_id(impl_item_id);
 594     tcx.generics_of(def_id);
 595     tcx.type_of(def_id);
 596     tcx.predicates_of(def_id);
 597     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
 598         tcx.fn_sig(def_id);
 599     }
 600 }
 601
 602 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 603     let def_id = tcx.hir().local_def_id(ctor_id);
 604     tcx.generics_of(def_id);
 605     tcx.type_of(def_id);
 606     tcx.predicates_of(def_id);
 607 }
 608
 609 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 610     let def = tcx.adt_def(def_id);
 611     let repr_type = def.repr.discr_type();
 612     let initial = repr_type.initial_discriminant(tcx);
 613     let mut prev_discr = None::<Discr<'_>>;
 614
 615     // fill the discriminant values and field types
 616     for variant in variants {
 617         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 618         prev_discr = Some(
 619             if let Some(ref e) = variant.disr_expr {
 620                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 621                 def.eval_explicit_discr(tcx, expr_did)
 622             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 623                 Some(discr)
 624             } else {
 625                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 626                     .span_label(
 627                         variant.span,
 628                         format!("overflowed on value after {}", prev_discr.unwrap()),
 629                     )
 630                     .note(&format!(
 631                         "explicitly set `{} = {}` if that is desired outcome",
 632                         variant.ident, wrapped_discr
 633                     ))
 634                     .emit();
 635                 None
 636             }
 637             .unwrap_or(wrapped_discr),
 638         );
 639
 640         for f in variant.data.fields() {
 641             let def_id = tcx.hir().local_def_id(f.hir_id);
 642             tcx.generics_of(def_id);
 643             tcx.type_of(def_id);
 644             tcx.predicates_of(def_id);
 645         }
 646
 647         // Convert the ctor, if any. This also registers the variant as
 648         // an item.
 649         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 650             convert_variant_ctor(tcx, ctor_hir_id);
 651         }
 652     }
 653 }
 654
 655 fn convert_variant(
 656     tcx: TyCtxt<'_>,
 657     variant_did: Option<DefId>,
 658     ctor_did: Option<DefId>,
 659     ident: Ident,
 660     discr: ty::VariantDiscr,
 661     def: &hir::VariantData<'_>,
 662     adt_kind: ty::AdtKind,
 663     parent_did: DefId,
 664 ) -> ty::VariantDef {
 665     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 666     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 667     let fields = def
 668         .fields()
 669         .iter()
 670         .map(|f| {
 671             let fid = tcx.hir().local_def_id(f.hir_id);
 672             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 673             if let Some(prev_span) = dup_span {
 674                 struct_span_err!(
 675                     tcx.sess,
 676                     f.span,
 677                     E0124,
 678                     "field `{}` is already declared",
 679                     f.ident
 680                 )
 681                 .span_label(f.span, "field already declared")
 682                 .span_label(prev_span, format!("`{}` first declared here", f.ident))
 683                 .emit();
 684             } else {
 685                 seen_fields.insert(f.ident.modern(), f.span);
 686             }
 687
 688             ty::FieldDef {
 689                 did: fid,
 690                 ident: f.ident,
 691                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 692             }
 693         })
 694         .collect();
 695     let recovered = match def {
 696         hir::VariantData::Struct(_, r) => *r,
 697         _ => false,
 698     };
 699     ty::VariantDef::new(
 700         tcx,
 701         ident,
 702         variant_did,
 703         ctor_did,
 704         discr,
 705         fields,
 706         CtorKind::from_hir(def),
 707         adt_kind,
 708         parent_did,
 709         recovered,
 710     )
 711 }
 712
 713 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 714     use rustc::hir::*;
 715
 716     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 717     let item = match tcx.hir().get(hir_id) {
 718         Node::Item(item) => item,
 719         _ => bug!(),
 720     };
 721
 722     let repr = ReprOptions::new(tcx, def_id);
 723     let (kind, variants) = match item.kind {
 724         ItemKind::Enum(ref def, _) => {
 725             let mut distance_from_explicit = 0;
 726             let variants = def
 727                 .variants
 728                 .iter()
 729                 .map(|v| {
 730                     let variant_did = Some(tcx.hir().local_def_id(v.id));
 731                     let ctor_did =
 732                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 733
 734                     let discr = if let Some(ref e) = v.disr_expr {
 735                         distance_from_explicit = 0;
 736                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 737                     } else {
 738                         ty::VariantDiscr::Relative(distance_from_explicit)
 739                     };
 740                     distance_from_explicit += 1;
 741
 742                     convert_variant(
 743                         tcx,
 744                         variant_did,
 745                         ctor_did,
 746                         v.ident,
 747                         discr,
 748                         &v.data,
 749                         AdtKind::Enum,
 750                         def_id,
 751                     )
 752                 })
 753                 .collect();
 754
 755             (AdtKind::Enum, variants)
 756         }
 757         ItemKind::Struct(ref def, _) => {
 758             let variant_did = None;
 759             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 760
 761             let variants = std::iter::once(convert_variant(
 762                 tcx,
 763                 variant_did,
 764                 ctor_did,
 765                 item.ident,
 766                 ty::VariantDiscr::Relative(0),
 767                 def,
 768                 AdtKind::Struct,
 769                 def_id,
 770             ))
 771             .collect();
 772
 773             (AdtKind::Struct, variants)
 774         }
 775         ItemKind::Union(ref def, _) => {
 776             let variant_did = None;
 777             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
 778
 779             let variants = std::iter::once(convert_variant(
 780                 tcx,
 781                 variant_did,
 782                 ctor_did,
 783                 item.ident,
 784                 ty::VariantDiscr::Relative(0),
 785                 def,
 786                 AdtKind::Union,
 787                 def_id,
 788             ))
 789             .collect();
 790
 791             (AdtKind::Union, variants)
 792         }
 793         _ => bug!(),
 794     };
 795     tcx.alloc_adt_def(def_id, kind, variants, repr)
 796 }
 797
 798 /// Ensures that the super-predicates of the trait with a `DefId`
 799 /// of `trait_def_id` are converted and stored. This also ensures that
 800 /// the transitive super-predicates are converted.
 801 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
 802     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 803     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 804
 805     let item = match tcx.hir().get(trait_hir_id) {
 806         Node::Item(item) => item,
 807         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 808     };
 809
 810     let (generics, bounds) = match item.kind {
 811         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 812         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 813         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 814     };
 815
 816     let icx = ItemCtxt::new(tcx, trait_def_id);
 817
 818     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 819     let self_param_ty = tcx.types.self_param;
 820     let superbounds1 =
 821         AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 822
 823     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 824
 825     // Convert any explicit superbounds in the where-clause,
 826     // e.g., `trait Foo where Self: Bar`.
 827     // In the case of trait aliases, however, we include all bounds in the where-clause,
 828     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 829     // as one of its "superpredicates".
 830     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 831     let superbounds2 = icx.type_parameter_bounds_in_generics(
 832         generics,
 833         item.hir_id,
 834         self_param_ty,
 835         OnlySelfBounds(!is_trait_alias),
 836     );
 837
 838     // Combine the two lists to form the complete set of superbounds:
 839     let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
 840
 841     // Now require that immediate supertraits are converted,
 842     // which will, in turn, reach indirect supertraits.
 843     for &(pred, span) in superbounds {
 844         debug!("superbound: {:?}", pred);
 845         if let ty::Predicate::Trait(bound) = pred {
 846             tcx.at(span).super_predicates_of(bound.def_id());
 847         }
 848     }
 849
 850     ty::GenericPredicates { parent: None, predicates: superbounds }
 851 }
 852
 853 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 854     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 855     let item = tcx.hir().expect_item(hir_id);
 856
 857     let (is_auto, unsafety) = match item.kind {
 858         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 859         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 860         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 861     };
 862
 863     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 864     if paren_sugar && !tcx.features().unboxed_closures {
 865         let mut err = tcx.sess.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!(
 871             &mut err,
 872             "add `#![feature(unboxed_closures)]` to \
 873              the crate attributes to use it"
 874         );
 875         err.emit();
 876     }
 877
 878     let is_marker = tcx.has_attr(def_id, sym::marker);
 879     let def_path_hash = tcx.def_path_hash(def_id);
 880     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 881     tcx.arena.alloc(def)
 882 }
 883
 884 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 885     struct LateBoundRegionsDetector<'tcx> {
 886         tcx: TyCtxt<'tcx>,
 887         outer_index: ty::DebruijnIndex,
 888         has_late_bound_regions: Option<Span>,
 889     }
 890
 891     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 892         fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 893             NestedVisitorMap::None
 894         }
 895
 896         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
 897             if self.has_late_bound_regions.is_some() {
 898                 return;
 899             }
 900             match ty.kind {
 901                 hir::TyKind::BareFn(..) => {
 902                     self.outer_index.shift_in(1);
 903                     intravisit::walk_ty(self, ty);
 904                     self.outer_index.shift_out(1);
 905                 }
 906                 _ => intravisit::walk_ty(self, ty),
 907             }
 908         }
 909
 910         fn visit_poly_trait_ref(
 911             &mut self,
 912             tr: &'tcx hir::PolyTraitRef<'tcx>,
 913             m: hir::TraitBoundModifier,
 914         ) {
 915             if self.has_late_bound_regions.is_some() {
 916                 return;
 917             }
 918             self.outer_index.shift_in(1);
 919             intravisit::walk_poly_trait_ref(self, tr, m);
 920             self.outer_index.shift_out(1);
 921         }
 922
 923         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 924             if self.has_late_bound_regions.is_some() {
 925                 return;
 926             }
 927
 928             match self.tcx.named_region(lt.hir_id) {
 929                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 930                 Some(rl::Region::LateBound(debruijn, _, _))
 931                 | Some(rl::Region::LateBoundAnon(debruijn, _))
 932                     if debruijn < self.outer_index => {}
 933                 Some(rl::Region::LateBound(..))
 934                 | Some(rl::Region::LateBoundAnon(..))
 935                 | Some(rl::Region::Free(..))
 936                 | None => {
 937                     self.has_late_bound_regions = Some(lt.span);
 938                 }
 939             }
 940         }
 941     }
 942
 943     fn has_late_bound_regions<'tcx>(
 944         tcx: TyCtxt<'tcx>,
 945         generics: &'tcx hir::Generics<'tcx>,
 946         decl: &'tcx hir::FnDecl<'tcx>,
 947     ) -> Option<Span> {
 948         let mut visitor = LateBoundRegionsDetector {
 949             tcx,
 950             outer_index: ty::INNERMOST,
 951             has_late_bound_regions: None,
 952         };
 953         for param in generics.params {
 954             if let GenericParamKind::Lifetime { .. } = param.kind {
 955                 if tcx.is_late_bound(param.hir_id) {
 956                     return Some(param.span);
 957                 }
 958             }
 959         }
 960         visitor.visit_fn_decl(decl);
 961         visitor.has_late_bound_regions
 962     }
 963
 964     match node {
 965         Node::TraitItem(item) => match item.kind {
 966             hir::TraitItemKind::Method(ref sig, _) => {
 967                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 968             }
 969             _ => None,
 970         },
 971         Node::ImplItem(item) => match item.kind {
 972             hir::ImplItemKind::Method(ref sig, _) => {
 973                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 974             }
 975             _ => None,
 976         },
 977         Node::ForeignItem(item) => match item.kind {
 978             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
 979                 has_late_bound_regions(tcx, generics, fn_decl)
 980             }
 981             _ => None,
 982         },
 983         Node::Item(item) => match item.kind {
 984             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
 985                 has_late_bound_regions(tcx, generics, &sig.decl)
 986             }
 987             _ => None,
 988         },
 989         _ => None,
 990     }
 991 }
 992
 993 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
 994     use rustc::hir::*;
 995
 996     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 997
 998     let node = tcx.hir().get(hir_id);
 999     let parent_def_id = match node {
1000         Node::ImplItem(_)
1001         | Node::TraitItem(_)
1002         | Node::Variant(_)
1003         | Node::Ctor(..)
1004         | Node::Field(_) => {
1005             let parent_id = tcx.hir().get_parent_item(hir_id);
1006             Some(tcx.hir().local_def_id(parent_id))
1007         }
1008         // FIXME(#43408) enable this always when we get lazy normalization.
1009         Node::AnonConst(_) => {
1010             // HACK(eddyb) this provides the correct generics when
1011             // `feature(const_generics)` is enabled, so that const expressions
1012             // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1013             if tcx.features().const_generics {
1014                 let parent_id = tcx.hir().get_parent_item(hir_id);
1015                 Some(tcx.hir().local_def_id(parent_id))
1016             } else {
1017                 None
1018             }
1019         }
1020         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1021             Some(tcx.closure_base_def_id(def_id))
1022         }
1023         Node::Item(item) => match item.kind {
1024             ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
1025             _ => None,
1026         },
1027         _ => None,
1028     };
1029
1030     let mut opt_self = None;
1031     let mut allow_defaults = false;
1032
1033     let no_generics = hir::Generics::empty();
1034     let ast_generics = match node {
1035         Node::TraitItem(item) => &item.generics,
1036
1037         Node::ImplItem(item) => &item.generics,
1038
1039         Node::Item(item) => {
1040             match item.kind {
1041                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
1042                     generics
1043                 }
1044
1045                 ItemKind::TyAlias(_, ref generics)
1046                 | ItemKind::Enum(_, ref generics)
1047                 | ItemKind::Struct(_, ref generics)
1048                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1049                 | ItemKind::Union(_, ref generics) => {
1050                     allow_defaults = true;
1051                     generics
1052                 }
1053
1054                 ItemKind::Trait(_, _, ref generics, ..)
1055                 | ItemKind::TraitAlias(ref generics, ..) => {
1056                     // Add in the self type parameter.
1057                     //
1058                     // Something of a hack: use the node id for the trait, also as
1059                     // the node id for the Self type parameter.
1060                     let param_id = item.hir_id;
1061
1062                     opt_self = Some(ty::GenericParamDef {
1063                         index: 0,
1064                         name: kw::SelfUpper,
1065                         def_id: tcx.hir().local_def_id(param_id),
1066                         pure_wrt_drop: false,
1067                         kind: ty::GenericParamDefKind::Type {
1068                             has_default: false,
1069                             object_lifetime_default: rl::Set1::Empty,
1070                             synthetic: None,
1071                         },
1072                     });
1073
1074                     allow_defaults = true;
1075                     generics
1076                 }
1077
1078                 _ => &no_generics,
1079             }
1080         }
1081
1082         Node::ForeignItem(item) => match item.kind {
1083             ForeignItemKind::Static(..) => &no_generics,
1084             ForeignItemKind::Fn(_, _, ref generics) => generics,
1085             ForeignItemKind::Type => &no_generics,
1086         },
1087
1088         _ => &no_generics,
1089     };
1090
1091     let has_self = opt_self.is_some();
1092     let mut parent_has_self = false;
1093     let mut own_start = has_self as u32;
1094     let parent_count = parent_def_id.map_or(0, |def_id| {
1095         let generics = tcx.generics_of(def_id);
1096         assert_eq!(has_self, false);
1097         parent_has_self = generics.has_self;
1098         own_start = generics.count() as u32;
1099         generics.parent_count + generics.params.len()
1100     });
1101
1102     let mut params: Vec<_> = opt_self.into_iter().collect();
1103
1104     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1105     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1106         name: param.name.ident().name,
1107         index: own_start + i as u32,
1108         def_id: tcx.hir().local_def_id(param.hir_id),
1109         pure_wrt_drop: param.pure_wrt_drop,
1110         kind: ty::GenericParamDefKind::Lifetime,
1111     }));
1112
1113     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1114
1115     // Now create the real type parameters.
1116     let type_start = own_start - has_self as u32 + params.len() as u32;
1117     let mut i = 0;
1118     params.extend(ast_generics.params.iter().filter_map(|param| {
1119         let kind = match param.kind {
1120             GenericParamKind::Type { ref default, synthetic, .. } => {
1121                 if !allow_defaults && default.is_some() {
1122                     if !tcx.features().default_type_parameter_fallback {
1123                         tcx.lint_hir(
1124                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1125                             param.hir_id,
1126                             param.span,
1127                             &format!(
1128                                 "defaults for type parameters are only allowed in \
1129                                         `struct`, `enum`, `type`, or `trait` definitions."
1130                             ),
1131                         );
1132                     }
1133                 }
1134
1135                 ty::GenericParamDefKind::Type {
1136                     has_default: default.is_some(),
1137                     object_lifetime_default: object_lifetime_defaults
1138                         .as_ref()
1139                         .map_or(rl::Set1::Empty, |o| o[i]),
1140                     synthetic,
1141                 }
1142             }
1143             GenericParamKind::Const { .. } => ty::GenericParamDefKind::Const,
1144             _ => return None,
1145         };
1146
1147         let param_def = ty::GenericParamDef {
1148             index: type_start + i as u32,
1149             name: param.name.ident().name,
1150             def_id: tcx.hir().local_def_id(param.hir_id),
1151             pure_wrt_drop: param.pure_wrt_drop,
1152             kind,
1153         };
1154         i += 1;
1155         Some(param_def)
1156     }));
1157
1158     // provide junk type parameter defs - the only place that
1159     // cares about anything but the length is instantiation,
1160     // and we don't do that for closures.
1161     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1162         let dummy_args = if gen.is_some() {
1163             &["<yield_ty>", "<return_ty>", "<witness>"][..]
1164         } else {
1165             &["<closure_kind>", "<closure_signature>"][..]
1166         };
1167
1168         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1169             index: type_start + i as u32,
1170             name: Symbol::intern(arg),
1171             def_id,
1172             pure_wrt_drop: false,
1173             kind: ty::GenericParamDefKind::Type {
1174                 has_default: false,
1175                 object_lifetime_default: rl::Set1::Empty,
1176                 synthetic: None,
1177             },
1178         }));
1179
1180         if let Some(upvars) = tcx.upvars(def_id) {
1181             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1182                 ty::GenericParamDef {
1183                     index: type_start + i,
1184                     name: Symbol::intern("<upvar>"),
1185                     def_id,
1186                     pure_wrt_drop: false,
1187                     kind: ty::GenericParamDefKind::Type {
1188                         has_default: false,
1189                         object_lifetime_default: rl::Set1::Empty,
1190                         synthetic: None,
1191                     },
1192                 }
1193             }));
1194         }
1195     }
1196
1197     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1198
1199     tcx.arena.alloc(ty::Generics {
1200         parent: parent_def_id,
1201         parent_count,
1202         params,
1203         param_def_id_to_index,
1204         has_self: has_self || parent_has_self,
1205         has_late_bound_regions: has_late_bound_regions(tcx, node),
1206     })
1207 }
1208
1209 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1210     span_err!(
1211         tcx.sess,
1212         span,
1213         E0202,
1214         "associated types are not yet supported in inherent impls (see #8995)"
1215     );
1216 }
1217
1218 fn infer_placeholder_type(
1219     tcx: TyCtxt<'_>,
1220     def_id: DefId,
1221     body_id: hir::BodyId,
1222     span: Span,
1223     item_ident: Ident,
1224 ) -> Ty<'_> {
1225     let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
1226
1227     // If this came from a free `const` or `static mut?` item,
1228     // then the user may have written e.g. `const A = 42;`.
1229     // In this case, the parser has stashed a diagnostic for
1230     // us to improve in typeck so we do that now.
1231     match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1232         Some(mut err) => {
1233             // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1234             // We are typeck and have the real type, so remove that and suggest the actual type.
1235             err.suggestions.clear();
1236             err.span_suggestion(
1237                 span,
1238                 "provide a type for the item",
1239                 format!("{}: {}", item_ident, ty),
1240                 Applicability::MachineApplicable,
1241             )
1242             .emit();
1243         }
1244         None => {
1245             let mut diag = bad_placeholder_type(tcx, vec![span]);
1246             if ty != tcx.types.err {
1247                 diag.span_suggestion(
1248                     span,
1249                     "replace `_` with the correct type",
1250                     ty.to_string(),
1251                     Applicability::MaybeIncorrect,
1252                 );
1253             }
1254             diag.emit();
1255         }
1256     }
1257
1258     ty
1259 }
1260
1261 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1262     use rustc::hir::*;
1263
1264     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1265
1266     let icx = ItemCtxt::new(tcx, def_id);
1267
1268     match tcx.hir().get(hir_id) {
1269         Node::TraitItem(item) => match item.kind {
1270             TraitItemKind::Method(..) => {
1271                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1272                 tcx.mk_fn_def(def_id, substs)
1273             }
1274             TraitItemKind::Const(ref ty, body_id) => body_id
1275                 .and_then(|body_id| {
1276                     if is_suggestable_infer_ty(ty) {
1277                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1278                     } else {
1279                         None
1280                     }
1281                 })
1282                 .unwrap_or_else(|| icx.to_ty(ty)),
1283             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1284             TraitItemKind::Type(_, None) => {
1285                 span_bug!(item.span, "associated type missing default");
1286             }
1287         },
1288
1289         Node::ImplItem(item) => match item.kind {
1290             ImplItemKind::Method(..) => {
1291                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1292                 tcx.mk_fn_def(def_id, substs)
1293             }
1294             ImplItemKind::Const(ref ty, body_id) => {
1295                 if is_suggestable_infer_ty(ty) {
1296                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1297                 } else {
1298                     icx.to_ty(ty)
1299                 }
1300             }
1301             ImplItemKind::OpaqueTy(_) => {
1302                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1303                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1304                 }
1305
1306                 find_opaque_ty_constraints(tcx, def_id)
1307             }
1308             ImplItemKind::TyAlias(ref ty) => {
1309                 if tcx.impl_trait_ref(tcx.hir().get_parent_did(hir_id)).is_none() {
1310                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1311                 }
1312
1313                 icx.to_ty(ty)
1314             }
1315         },
1316
1317         Node::Item(item) => {
1318             match item.kind {
1319                 ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
1320                     if is_suggestable_infer_ty(ty) {
1321                         infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1322                     } else {
1323                         icx.to_ty(ty)
1324                     }
1325                 }
1326                 ItemKind::TyAlias(ref ty, _) | ItemKind::Impl(.., ref ty, _) => icx.to_ty(ty),
1327                 ItemKind::Fn(..) => {
1328                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1329                     tcx.mk_fn_def(def_id, substs)
1330                 }
1331                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1332                     let def = tcx.adt_def(def_id);
1333                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1334                     tcx.mk_adt(def, substs)
1335                 }
1336                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
1337                     find_opaque_ty_constraints(tcx, def_id)
1338                 }
1339                 // Opaque types desugared from `impl Trait`.
1340                 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: Some(owner), .. }) => {
1341                     tcx.typeck_tables_of(owner)
1342                         .concrete_opaque_types
1343                         .get(&def_id)
1344                         .map(|opaque| opaque.concrete_type)
1345                         .unwrap_or_else(|| {
1346                             // This can occur if some error in the
1347                             // owner fn prevented us from populating
1348                             // the `concrete_opaque_types` table.
1349                             tcx.sess.delay_span_bug(
1350                                 DUMMY_SP,
1351                                 &format!(
1352                                     "owner {:?} has no opaque type for {:?} in its tables",
1353                                     owner, def_id,
1354                                 ),
1355                             );
1356                             tcx.types.err
1357                         })
1358                 }
1359                 ItemKind::Trait(..)
1360                 | ItemKind::TraitAlias(..)
1361                 | ItemKind::Mod(..)
1362                 | ItemKind::ForeignMod(..)
1363                 | ItemKind::GlobalAsm(..)
1364                 | ItemKind::ExternCrate(..)
1365                 | ItemKind::Use(..) => {
1366                     span_bug!(
1367                         item.span,
1368                         "compute_type_of_item: unexpected item type: {:?}",
1369                         item.kind
1370                     );
1371                 }
1372             }
1373         }
1374
1375         Node::ForeignItem(foreign_item) => match foreign_item.kind {
1376             ForeignItemKind::Fn(..) => {
1377                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1378                 tcx.mk_fn_def(def_id, substs)
1379             }
1380             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1381             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1382         },
1383
1384         Node::Ctor(&ref def) | Node::Variant(hir::Variant { data: ref def, .. }) => match *def {
1385             VariantData::Unit(..) | VariantData::Struct(..) => {
1386                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1387             }
1388             VariantData::Tuple(..) => {
1389                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1390                 tcx.mk_fn_def(def_id, substs)
1391             }
1392         },
1393
1394         Node::Field(field) => icx.to_ty(&field.ty),
1395
1396         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) => {
1397             if gen.is_some() {
1398                 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1399             }
1400
1401             let substs = InternalSubsts::identity_for_item(tcx, def_id);
1402             tcx.mk_closure(def_id, substs)
1403         }
1404
1405         Node::AnonConst(_) => {
1406             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1407             match parent_node {
1408                 Node::Ty(&hir::Ty { kind: hir::TyKind::Array(_, ref constant), .. })
1409                 | Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref constant), .. })
1410                 | Node::Expr(&hir::Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1411                     if constant.hir_id == hir_id =>
1412                 {
1413                     tcx.types.usize
1414                 }
1415
1416                 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
1417                     tcx.adt_def(tcx.hir().get_parent_did(hir_id)).repr.discr_type().to_ty(tcx)
1418                 }
1419
1420                 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. })
1421                 | Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. })
1422                 | Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. })
1423                 | Node::TraitRef(..) => {
1424                     let path = match parent_node {
1425                         Node::Ty(&hir::Ty {
1426                             kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1427                             ..
1428                         })
1429                         | Node::Expr(&hir::Expr {
1430                             kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1431                             ..
1432                         }) => Some(&**path),
1433                         Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1434                             if let QPath::Resolved(_, ref path) = **path {
1435                                 Some(&**path)
1436                             } else {
1437                                 None
1438                             }
1439                         }
1440                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1441                         _ => None,
1442                     };
1443
1444                     if let Some(path) = path {
1445                         let arg_index = path
1446                             .segments
1447                             .iter()
1448                             .filter_map(|seg| seg.args.as_ref())
1449                             .map(|generic_args| generic_args.args.as_ref())
1450                             .find_map(|args| {
1451                                 args.iter()
1452                                     .filter(|arg| arg.is_const())
1453                                     .enumerate()
1454                                     .filter(|(_, arg)| arg.id() == hir_id)
1455                                     .map(|(index, _)| index)
1456                                     .next()
1457                             })
1458                             .unwrap_or_else(|| {
1459                                 bug!("no arg matching AnonConst in path");
1460                             });
1461
1462                         // We've encountered an `AnonConst` in some path, so we need to
1463                         // figure out which generic parameter it corresponds to and return
1464                         // the relevant type.
1465                         let generics = match path.res {
1466                             Res::Def(DefKind::Ctor(..), def_id) => {
1467                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1468                             }
1469                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1470                             Res::Err => return tcx.types.err,
1471                             res => {
1472                                 tcx.sess.delay_span_bug(
1473                                     DUMMY_SP,
1474                                     &format!("unexpected const parent path def {:?}", res,),
1475                                 );
1476                                 return tcx.types.err;
1477                             }
1478                         };
1479
1480                         generics
1481                             .params
1482                             .iter()
1483                             .filter(|param| {
1484                                 if let ty::GenericParamDefKind::Const = param.kind {
1485                                     true
1486                                 } else {
1487                                     false
1488                                 }
1489                             })
1490                             .nth(arg_index)
1491                             .map(|param| tcx.type_of(param.def_id))
1492                             // This is no generic parameter associated with the arg. This is
1493                             // probably from an extra arg where one is not needed.
1494                             .unwrap_or(tcx.types.err)
1495                     } else {
1496                         tcx.sess.delay_span_bug(
1497                             DUMMY_SP,
1498                             &format!("unexpected const parent path {:?}", parent_node,),
1499                         );
1500                         return tcx.types.err;
1501                     }
1502                 }
1503
1504                 x => {
1505                     tcx.sess.delay_span_bug(
1506                         DUMMY_SP,
1507                         &format!("unexpected const parent in type_of_def_id(): {:?}", x),
1508                     );
1509                     tcx.types.err
1510                 }
1511             }
1512         }
1513
1514         Node::GenericParam(param) => {
1515             match &param.kind {
1516                 hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1517                 hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1518                     let ty = icx.to_ty(hir_ty);
1519                     if !tcx.features().const_compare_raw_pointers {
1520                         let err = match ty.peel_refs().kind {
1521                             ty::FnPtr(_) => Some("function pointers"),
1522                             ty::RawPtr(_) => Some("raw pointers"),
1523                             _ => None,
1524                         };
1525                         if let Some(unsupported_type) = err {
1526                             feature_gate::feature_err(
1527                                 &tcx.sess.parse_sess,
1528                                 sym::const_compare_raw_pointers,
1529                                 hir_ty.span,
1530                                 &format!(
1531                                     "using {} as const generic parameters is unstable",
1532                                     unsupported_type
1533                                 ),
1534                             )
1535                             .emit();
1536                         };
1537                     }
1538                     if ty::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
1539                         .is_some()
1540                     {
1541                         struct_span_err!(
1542                         tcx.sess,
1543                         hir_ty.span,
1544                         E0741,
1545                         "the types of const generic parameters must derive `PartialEq` and `Eq`",
1546                     ).span_label(
1547                         hir_ty.span,
1548                         format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1549                     ).emit();
1550                     }
1551                     ty
1552                 }
1553                 x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1554             }
1555         }
1556
1557         x => {
1558             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1559         }
1560     }
1561 }
1562
1563 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1564     use rustc::hir::{ImplItem, Item, TraitItem};
1565
1566     debug!("find_opaque_ty_constraints({:?})", def_id);
1567
1568     struct ConstraintLocator<'tcx> {
1569         tcx: TyCtxt<'tcx>,
1570         def_id: DefId,
1571         // (first found type span, actual type, mapping from the opaque type's generic
1572         // parameters to the concrete type's generic parameters)
1573         //
1574         // The mapping is an index for each use site of a generic parameter in the concrete type
1575         //
1576         // The indices index into the generic parameters on the opaque type.
1577         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1578     }
1579
1580     impl ConstraintLocator<'tcx> {
1581         fn check(&mut self, def_id: DefId) {
1582             // Don't try to check items that cannot possibly constrain the type.
1583             if !self.tcx.has_typeck_tables(def_id) {
1584                 debug!(
1585                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1586                     self.def_id, def_id,
1587                 );
1588                 return;
1589             }
1590             let ty = self.tcx.typeck_tables_of(def_id).concrete_opaque_types.get(&self.def_id);
1591             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1592                 debug!(
1593                     "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1594                     self.def_id, def_id, ty,
1595                 );
1596
1597                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1598                 let span = self.tcx.def_span(def_id);
1599                 // used to quickly look up the position of a generic parameter
1600                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1601                 // Skipping binder is ok, since we only use this to find generic parameters and
1602                 // their positions.
1603                 for (idx, subst) in substs.iter().enumerate() {
1604                     if let GenericArgKind::Type(ty) = subst.unpack() {
1605                         if let ty::Param(p) = ty.kind {
1606                             if index_map.insert(p, idx).is_some() {
1607                                 // There was already an entry for `p`, meaning a generic parameter
1608                                 // was used twice.
1609                                 self.tcx.sess.span_err(
1610                                     span,
1611                                     &format!(
1612                                         "defining opaque type use restricts opaque \
1613                                          type by using the generic parameter `{}` twice",
1614                                         p,
1615                                     ),
1616                                 );
1617                                 return;
1618                             }
1619                         } else {
1620                             self.tcx.sess.delay_span_bug(
1621                                 span,
1622                                 &format!(
1623                                     "non-defining opaque ty use in defining scope: {:?}, {:?}",
1624                                     concrete_type, substs,
1625                                 ),
1626                             );
1627                         }
1628                     }
1629                 }
1630                 // Compute the index within the opaque type for each generic parameter used in
1631                 // the concrete type.
1632                 let indices = concrete_type
1633                     .subst(self.tcx, substs)
1634                     .walk()
1635                     .filter_map(|t| match &t.kind {
1636                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1637                         _ => None,
1638                     })
1639                     .collect();
1640                 let is_param = |ty: Ty<'_>| match ty.kind {
1641                     ty::Param(_) => true,
1642                     _ => false,
1643                 };
1644                 let bad_substs: Vec<_> =
1645                     substs.types().enumerate().filter(|(_, ty)| !is_param(ty)).collect();
1646                 if !bad_substs.is_empty() {
1647                     let identity_substs = InternalSubsts::identity_for_item(self.tcx, self.def_id);
1648                     for (i, bad_subst) in bad_substs {
1649                         self.tcx.sess.span_err(
1650                             span,
1651                             &format!(
1652                                 "defining opaque type use does not fully define opaque type: \
1653                             generic parameter `{}` is specified as concrete type `{}`",
1654                                 identity_substs.type_at(i),
1655                                 bad_subst
1656                             ),
1657                         );
1658                     }
1659                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1660                     let mut ty = concrete_type.walk().fuse();
1661                     let mut p_ty = prev_ty.walk().fuse();
1662                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1663                         // Type parameters are equal to any other type parameter for the purpose of
1664                         // concrete type equality, as it is possible to obtain the same type just
1665                         // by passing matching parameters to a function.
1666                         (ty::Param(_), ty::Param(_)) => true,
1667                         _ => t == p,
1668                     });
1669                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1670                         debug!("find_opaque_ty_constraints: span={:?}", span);
1671                         // Found different concrete types for the opaque type.
1672                         let mut err = self.tcx.sess.struct_span_err(
1673                             span,
1674                             "concrete type differs from previous defining opaque type use",
1675                         );
1676                         err.span_label(
1677                             span,
1678                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1679                         );
1680                         err.span_note(prev_span, "previous use here");
1681                         err.emit();
1682                     } else if indices != *prev_indices {
1683                         // Found "same" concrete types, but the generic parameter order differs.
1684                         let mut err = self.tcx.sess.struct_span_err(
1685                             span,
1686                             "concrete type's generic parameters differ from previous defining use",
1687                         );
1688                         use std::fmt::Write;
1689                         let mut s = String::new();
1690                         write!(s, "expected [").unwrap();
1691                         let list = |s: &mut String, indices: &Vec<usize>| {
1692                             let mut indices = indices.iter().cloned();
1693                             if let Some(first) = indices.next() {
1694                                 write!(s, "`{}`", substs[first]).unwrap();
1695                                 for i in indices {
1696                                     write!(s, ", `{}`", substs[i]).unwrap();
1697                                 }
1698                             }
1699                         };
1700                         list(&mut s, prev_indices);
1701                         write!(s, "], got [").unwrap();
1702                         list(&mut s, &indices);
1703                         write!(s, "]").unwrap();
1704                         err.span_label(span, s);
1705                         err.span_note(prev_span, "previous use here");
1706                         err.emit();
1707                     }
1708                 } else {
1709                     self.found = Some((span, concrete_type, indices));
1710                 }
1711             } else {
1712                 debug!(
1713                     "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1714                     self.def_id, def_id,
1715                 );
1716             }
1717         }
1718     }
1719
1720     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1721         fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1722             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1723         }
1724         fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
1725             debug!("find_existential_constraints: visiting {:?}", it);
1726             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1727             // The opaque type itself or its children are not within its reveal scope.
1728             if def_id != self.def_id {
1729                 self.check(def_id);
1730                 intravisit::walk_item(self, it);
1731             }
1732         }
1733         fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
1734             debug!("find_existential_constraints: visiting {:?}", it);
1735             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1736             // The opaque type itself or its children are not within its reveal scope.
1737             if def_id != self.def_id {
1738                 self.check(def_id);
1739                 intravisit::walk_impl_item(self, it);
1740             }
1741         }
1742         fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
1743             debug!("find_existential_constraints: visiting {:?}", it);
1744             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1745             self.check(def_id);
1746             intravisit::walk_trait_item(self, it);
1747         }
1748     }
1749
1750     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1751     let scope = tcx.hir().get_defining_scope(hir_id);
1752     let mut locator = ConstraintLocator { def_id, tcx, found: None };
1753
1754     debug!("find_opaque_ty_constraints: scope={:?}", scope);
1755
1756     if scope == hir::CRATE_HIR_ID {
1757         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1758     } else {
1759         debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1760         match tcx.hir().get(scope) {
1761             // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1762             // This allows our visitor to process the defining item itself, causing
1763             // it to pick up any 'sibling' defining uses.
1764             //
1765             // For example, this code:
1766             // ```
1767             // fn foo() {
1768             //     type Blah = impl Debug;
1769             //     let my_closure = || -> Blah { true };
1770             // }
1771             // ```
1772             //
1773             // requires us to explicitly process `foo()` in order
1774             // to notice the defining usage of `Blah`.
1775             Node::Item(ref it) => locator.visit_item(it),
1776             Node::ImplItem(ref it) => locator.visit_impl_item(it),
1777             Node::TraitItem(ref it) => locator.visit_trait_item(it),
1778             other => bug!("{:?} is not a valid scope for an opaque type item", other),
1779         }
1780     }
1781
1782     match locator.found {
1783         Some((_, ty, _)) => ty,
1784         None => {
1785             let span = tcx.def_span(def_id);
1786             tcx.sess.span_err(span, "could not find defining uses");
1787             tcx.types.err
1788         }
1789     }
1790 }
1791
1792 /// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
1793 /// use inference to provide suggestions for the appropriate type if possible.
1794 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1795     match &ty.kind {
1796         hir::TyKind::Infer => true,
1797         hir::TyKind::Slice(ty) | hir::TyKind::Array(ty, _) => is_suggestable_infer_ty(ty),
1798         hir::TyKind::Tup(tys) => tys.iter().any(|ty| is_suggestable_infer_ty(ty)),
1799         _ => false,
1800     }
1801 }
1802
1803 pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1804     if let hir::FunctionRetTy::Return(ref ty) = output {
1805         if is_suggestable_infer_ty(ty) {
1806             return Some(&**ty);
1807         }
1808     }
1809     None
1810 }
1811
1812 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1813     use rustc::hir::Node::*;
1814     use rustc::hir::*;
1815
1816     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1817
1818     let icx = ItemCtxt::new(tcx, def_id);
1819
1820     match tcx.hir().get(hir_id) {
1821         TraitItem(hir::TraitItem {
1822             kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1823             ident,
1824             generics,
1825             ..
1826         })
1827         | ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
1828         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1829             match get_infer_ret_ty(&sig.decl.output) {
1830                 Some(ty) => {
1831                     let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1832                     let mut visitor = PlaceholderHirTyCollector::default();
1833                     visitor.visit_ty(ty);
1834                     let mut diag = bad_placeholder_type(tcx, visitor.0);
1835                     let ret_ty = fn_sig.output();
1836                     if ret_ty != tcx.types.err {
1837                         diag.span_suggestion(
1838                             ty.span,
1839                             "replace with the correct return type",
1840                             ret_ty.to_string(),
1841                             Applicability::MaybeIncorrect,
1842                         );
1843                     }
1844                     diag.emit();
1845                     ty::Binder::bind(fn_sig)
1846                 }
1847                 None => AstConv::ty_of_fn(
1848                     &icx,
1849                     sig.header.unsafety,
1850                     sig.header.abi,
1851                     &sig.decl,
1852                     &generics.params[..],
1853                     Some(ident.span),
1854                 ),
1855             }
1856         }
1857
1858         TraitItem(hir::TraitItem {
1859             kind: TraitItemKind::Method(FnSig { header, decl }, _),
1860             ident,
1861             generics,
1862             ..
1863         }) => AstConv::ty_of_fn(
1864             &icx,
1865             header.unsafety,
1866             header.abi,
1867             decl,
1868             &generics.params[..],
1869             Some(ident.span),
1870         ),
1871
1872         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
1873             let abi = tcx.hir().get_foreign_abi(hir_id);
1874             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1875         }
1876
1877         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1878             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1879             let inputs =
1880                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1881             ty::Binder::bind(tcx.mk_fn_sig(
1882                 inputs,
1883                 ty,
1884                 false,
1885                 hir::Unsafety::Normal,
1886                 abi::Abi::Rust,
1887             ))
1888         }
1889
1890         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1891             // Closure signatures are not like other function
1892             // signatures and cannot be accessed through `fn_sig`. For
1893             // example, a closure signature excludes the `self`
1894             // argument. In any case they are embedded within the
1895             // closure type as part of the `ClosureSubsts`.
1896             //
1897             // To get
1898             // the signature of a closure, you should use the
1899             // `closure_sig` method on the `ClosureSubsts`:
1900             //
1901             //    closure_substs.sig(def_id, tcx)
1902             //
1903             // or, inside of an inference context, you can use
1904             //
1905             //    infcx.closure_sig(def_id, closure_substs)
1906             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1907         }
1908
1909         x => {
1910             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1911         }
1912     }
1913 }
1914
1915 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1916     let icx = ItemCtxt::new(tcx, def_id);
1917
1918     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1919     match tcx.hir().expect_item(hir_id).kind {
1920         hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1921             opt_trait_ref.as_ref().map(|ast_trait_ref| {
1922                 let selfty = tcx.type_of(def_id);
1923                 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1924             })
1925         }
1926         _ => bug!(),
1927     }
1928 }
1929
1930 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1931     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1932     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1933     let item = tcx.hir().expect_item(hir_id);
1934     match &item.kind {
1935         hir::ItemKind::Impl(_, hir::ImplPolarity::Negative, ..) => {
1936             if is_rustc_reservation {
1937                 tcx.sess.span_err(item.span, "reservation impls can't be negative");
1938             }
1939             ty::ImplPolarity::Negative
1940         }
1941         hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, None, _, _) => {
1942             if is_rustc_reservation {
1943                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1944             }
1945             ty::ImplPolarity::Positive
1946         }
1947         hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, Some(_tr), _, _) => {
1948             if is_rustc_reservation {
1949                 ty::ImplPolarity::Reservation
1950             } else {
1951                 ty::ImplPolarity::Positive
1952             }
1953         }
1954         ref item => bug!("impl_polarity: {:?} not an impl", item),
1955     }
1956 }
1957
1958 /// Returns the early-bound lifetimes declared in this generics
1959 /// listing. For anything other than fns/methods, this is just all
1960 /// the lifetimes that are declared. For fns or methods, we have to
1961 /// screen out those that do not appear in any where-clauses etc using
1962 /// `resolve_lifetime::early_bound_lifetimes`.
1963 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1964     tcx: TyCtxt<'tcx>,
1965     generics: &'a hir::Generics<'a>,
1966 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1967     generics.params.iter().filter(move |param| match param.kind {
1968         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1969         _ => false,
1970     })
1971 }
1972
1973 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1974 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1975 /// inferred constraints concerning which regions outlive other regions.
1976 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1977     debug!("predicates_defined_on({:?})", def_id);
1978     let mut result = tcx.explicit_predicates_of(def_id);
1979     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1980     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1981     if !inferred_outlives.is_empty() {
1982         debug!(
1983             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1984             def_id, inferred_outlives,
1985         );
1986         if result.predicates.is_empty() {
1987             result.predicates = inferred_outlives;
1988         } else {
1989             result.predicates = tcx
1990                 .arena
1991                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1992         }
1993     }
1994     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1995     result
1996 }
1997
1998 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1999 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2000 /// `Self: Trait` predicates for traits.
2001 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2002     let mut result = tcx.predicates_defined_on(def_id);
2003
2004     if tcx.is_trait(def_id) {
2005         // For traits, add `Self: Trait` predicate. This is
2006         // not part of the predicates that a user writes, but it
2007         // is something that one must prove in order to invoke a
2008         // method or project an associated type.
2009         //
2010         // In the chalk setup, this predicate is not part of the
2011         // "predicates" for a trait item. But it is useful in
2012         // rustc because if you directly (e.g.) invoke a trait
2013         // method like `Trait::method(...)`, you must naturally
2014         // prove that the trait applies to the types that were
2015         // used, and adding the predicate into this list ensures
2016         // that this is done.
2017         let span = tcx.def_span(def_id);
2018         result.predicates =
2019             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2020                 ty::TraitRef::identity(tcx, def_id).to_predicate(),
2021                 span,
2022             ))));
2023     }
2024     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2025     result
2026 }
2027
2028 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2029 /// N.B., this does not include any implied/inferred constraints.
2030 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2031     use rustc::hir::*;
2032     use rustc_data_structures::fx::FxHashSet;
2033
2034     debug!("explicit_predicates_of(def_id={:?})", def_id);
2035
2036     /// A data structure with unique elements, which preserves order of insertion.
2037     /// Preserving the order of insertion is important here so as not to break
2038     /// compile-fail UI tests.
2039     // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2040     struct UniquePredicates<'tcx> {
2041         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2042         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2043     }
2044
2045     impl<'tcx> UniquePredicates<'tcx> {
2046         fn new() -> Self {
2047             UniquePredicates { predicates: vec![], uniques: FxHashSet::default() }
2048         }
2049
2050         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2051             if self.uniques.insert(value) {
2052                 self.predicates.push(value);
2053             }
2054         }
2055
2056         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2057             for value in iter {
2058                 self.push(value);
2059             }
2060         }
2061     }
2062
2063     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2064     let node = tcx.hir().get(hir_id);
2065
2066     let mut is_trait = None;
2067     let mut is_default_impl_trait = None;
2068
2069     let icx = ItemCtxt::new(tcx, def_id);
2070
2071     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2072
2073     let mut predicates = UniquePredicates::new();
2074
2075     let ast_generics = match node {
2076         Node::TraitItem(item) => &item.generics,
2077
2078         Node::ImplItem(item) => match item.kind {
2079             ImplItemKind::OpaqueTy(ref bounds) => {
2080                 ty::print::with_no_queries(|| {
2081                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2082                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2083                     debug!(
2084                         "explicit_predicates_of({:?}): created opaque type {:?}",
2085                         def_id, opaque_ty
2086                     );
2087
2088                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2089                     let bounds = AstConv::compute_bounds(
2090                         &icx,
2091                         opaque_ty,
2092                         bounds,
2093                         SizedByDefault::Yes,
2094                         tcx.def_span(def_id),
2095                     );
2096
2097                     predicates.extend(bounds.predicates(tcx, opaque_ty));
2098                     &item.generics
2099                 })
2100             }
2101             _ => &item.generics,
2102         },
2103
2104         Node::Item(item) => {
2105             match item.kind {
2106                 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
2107                     if defaultness.is_default() {
2108                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2109                     }
2110                     generics
2111                 }
2112                 ItemKind::Fn(.., ref generics, _)
2113                 | ItemKind::TyAlias(_, ref generics)
2114                 | ItemKind::Enum(_, ref generics)
2115                 | ItemKind::Struct(_, ref generics)
2116                 | ItemKind::Union(_, ref generics) => generics,
2117
2118                 ItemKind::Trait(_, _, ref generics, .., items) => {
2119                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2120                     generics
2121                 }
2122                 ItemKind::TraitAlias(ref generics, _) => {
2123                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &[]));
2124                     generics
2125                 }
2126                 ItemKind::OpaqueTy(OpaqueTy {
2127                     ref bounds,
2128                     impl_trait_fn,
2129                     ref generics,
2130                     origin: _,
2131                 }) => {
2132                     let bounds_predicates = ty::print::with_no_queries(|| {
2133                         let substs = InternalSubsts::identity_for_item(tcx, def_id);
2134                         let opaque_ty = tcx.mk_opaque(def_id, substs);
2135
2136                         // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2137                         let bounds = AstConv::compute_bounds(
2138                             &icx,
2139                             opaque_ty,
2140                             bounds,
2141                             SizedByDefault::Yes,
2142                             tcx.def_span(def_id),
2143                         );
2144
2145                         bounds.predicates(tcx, opaque_ty)
2146                     });
2147                     if impl_trait_fn.is_some() {
2148                         // opaque types
2149                         return ty::GenericPredicates {
2150                             parent: None,
2151                             predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2152                         };
2153                     } else {
2154                         // named opaque types
2155                         predicates.extend(bounds_predicates);
2156                         generics
2157                     }
2158                 }
2159
2160                 _ => NO_GENERICS,
2161             }
2162         }
2163
2164         Node::ForeignItem(item) => match item.kind {
2165             ForeignItemKind::Static(..) => NO_GENERICS,
2166             ForeignItemKind::Fn(_, _, ref generics) => generics,
2167             ForeignItemKind::Type => NO_GENERICS,
2168         },
2169
2170         _ => NO_GENERICS,
2171     };
2172
2173     let generics = tcx.generics_of(def_id);
2174     let parent_count = generics.parent_count as u32;
2175     let has_own_self = generics.has_self && parent_count == 0;
2176
2177     // Below we'll consider the bounds on the type parameters (including `Self`)
2178     // and the explicit where-clauses, but to get the full set of predicates
2179     // on a trait we need to add in the supertrait bounds and bounds found on
2180     // associated types.
2181     if let Some((_trait_ref, _)) = is_trait {
2182         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2183     }
2184
2185     // In default impls, we can assume that the self type implements
2186     // the trait. So in:
2187     //
2188     //     default impl Foo for Bar { .. }
2189     //
2190     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2191     // (see below). Recall that a default impl is not itself an impl, but rather a
2192     // set of defaults that can be incorporated into another impl.
2193     if let Some(trait_ref) = is_default_impl_trait {
2194         predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2195     }
2196
2197     // Collect the region predicates that were declared inline as
2198     // well. In the case of parameters declared on a fn or method, we
2199     // have to be careful to only iterate over early-bound regions.
2200     let mut index = parent_count + has_own_self as u32;
2201     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2202         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2203             def_id: tcx.hir().local_def_id(param.hir_id),
2204             index,
2205             name: param.name.ident().name,
2206         }));
2207         index += 1;
2208
2209         match param.kind {
2210             GenericParamKind::Lifetime { .. } => {
2211                 param.bounds.iter().for_each(|bound| match bound {
2212                     hir::GenericBound::Outlives(lt) => {
2213                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2214                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2215                         predicates.push((outlives.to_predicate(), lt.span));
2216                     }
2217                     _ => bug!(),
2218                 });
2219             }
2220             _ => bug!(),
2221         }
2222     }
2223
2224     // Collect the predicates that were written inline by the user on each
2225     // type parameter (e.g., `<T: Foo>`).
2226     for param in ast_generics.params {
2227         if let GenericParamKind::Type { .. } = param.kind {
2228             let name = param.name.ident().name;
2229             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2230             index += 1;
2231
2232             let sized = SizedByDefault::Yes;
2233             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2234             predicates.extend(bounds.predicates(tcx, param_ty));
2235         }
2236     }
2237
2238     // Add in the bounds that appear in the where-clause.
2239     let where_clause = &ast_generics.where_clause;
2240     for predicate in where_clause.predicates {
2241         match predicate {
2242             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2243                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2244
2245                 // Keep the type around in a dummy predicate, in case of no bounds.
2246                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2247                 // is still checked for WF.
2248                 if bound_pred.bounds.is_empty() {
2249                     if let ty::Param(_) = ty.kind {
2250                         // This is a `where T:`, which can be in the HIR from the
2251                         // transformation that moves `?Sized` to `T`'s declaration.
2252                         // We can skip the predicate because type parameters are
2253                         // trivially WF, but also we *should*, to avoid exposing
2254                         // users who never wrote `where Type:,` themselves, to
2255                         // compiler/tooling bugs from not handling WF predicates.
2256                     } else {
2257                         let span = bound_pred.bounded_ty.span;
2258                         let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2259                         predicates.push((
2260                             ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)),
2261                             span,
2262                         ));
2263                     }
2264                 }
2265
2266                 for bound in bound_pred.bounds.iter() {
2267                     match bound {
2268                         &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2269                             let mut bounds = Bounds::default();
2270                             let _ = AstConv::instantiate_poly_trait_ref(
2271                                 &icx,
2272                                 poly_trait_ref,
2273                                 ty,
2274                                 &mut bounds,
2275                             );
2276                             predicates.extend(bounds.predicates(tcx, ty));
2277                         }
2278
2279                         &hir::GenericBound::Outlives(ref lifetime) => {
2280                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2281                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2282                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2283                         }
2284                     }
2285                 }
2286             }
2287
2288             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2289                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2290                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2291                     let (r2, span) = match bound {
2292                         hir::GenericBound::Outlives(lt) => {
2293                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2294                         }
2295                         _ => bug!(),
2296                     };
2297                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2298
2299                     (ty::Predicate::RegionOutlives(pred), span)
2300                 }))
2301             }
2302
2303             &hir::WherePredicate::EqPredicate(..) => {
2304                 // FIXME(#20041)
2305             }
2306         }
2307     }
2308
2309     // Add predicates from associated type bounds.
2310     if let Some((self_trait_ref, trait_items)) = is_trait {
2311         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2312             associated_item_predicates(tcx, def_id, self_trait_ref, trait_item_ref)
2313         }))
2314     }
2315
2316     let mut predicates = predicates.predicates;
2317
2318     // Subtle: before we store the predicates into the tcx, we
2319     // sort them so that predicates like `T: Foo<Item=U>` come
2320     // before uses of `U`.  This avoids false ambiguity errors
2321     // in trait checking. See `setup_constraining_predicates`
2322     // for details.
2323     if let Node::Item(&Item { kind: ItemKind::Impl(..), .. }) = node {
2324         let self_ty = tcx.type_of(def_id);
2325         let trait_ref = tcx.impl_trait_ref(def_id);
2326         cgp::setup_constraining_predicates(
2327             tcx,
2328             &mut predicates,
2329             trait_ref,
2330             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2331         );
2332     }
2333
2334     let result = ty::GenericPredicates {
2335         parent: generics.parent,
2336         predicates: tcx.arena.alloc_from_iter(predicates),
2337     };
2338     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2339     result
2340 }
2341
2342 fn associated_item_predicates(
2343     tcx: TyCtxt<'tcx>,
2344     def_id: DefId,
2345     self_trait_ref: ty::TraitRef<'tcx>,
2346     trait_item_ref: &hir::TraitItemRef,
2347 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2348     let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2349     let item_def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
2350     let bounds = match trait_item.kind {
2351         hir::TraitItemKind::Type(ref bounds, _) => bounds,
2352         _ => return Vec::new(),
2353     };
2354
2355     let is_gat = !tcx.generics_of(item_def_id).params.is_empty();
2356
2357     let mut had_error = false;
2358
2359     let mut unimplemented_error = |arg_kind: &str| {
2360         if !had_error {
2361             tcx.sess
2362                 .struct_span_err(
2363                     trait_item.span,
2364                     &format!("{}-generic associated types are not yet implemented", arg_kind),
2365                 )
2366                 .note("for more information, see https://github.com/rust-lang/rust/issues/44265")
2367                 .emit();
2368             had_error = true;
2369         }
2370     };
2371
2372     let mk_bound_param = |param: &ty::GenericParamDef, _: &_| {
2373         match param.kind {
2374             ty::GenericParamDefKind::Lifetime => tcx
2375                 .mk_region(ty::RegionKind::ReLateBound(
2376                     ty::INNERMOST,
2377                     ty::BoundRegion::BrNamed(param.def_id, param.name),
2378                 ))
2379                 .into(),
2380             // FIXME(generic_associated_types): Use bound types and constants
2381             // once they are handled by the trait system.
2382             ty::GenericParamDefKind::Type { .. } => {
2383                 unimplemented_error("type");
2384                 tcx.types.err.into()
2385             }
2386             ty::GenericParamDefKind::Const => {
2387                 unimplemented_error("const");
2388                 tcx.consts.err.into()
2389             }
2390         }
2391     };
2392
2393     let bound_substs = if is_gat {
2394         // Given:
2395         //
2396         // trait X<'a, B, const C: usize> {
2397         //     type T<'d, E, const F: usize>: Default;
2398         // }
2399         //
2400         // We need to create predicates on the trait:
2401         //
2402         // for<'d, E, const F: usize>
2403         // <Self as X<'a, B, const C: usize>>::T<'d, E, const F: usize>: Sized + Default
2404         //
2405         // We substitute escaping bound parameters for the generic
2406         // arguments to the associated type which are then bound by
2407         // the `Binder` around the the predicate.
2408         //
2409         // FIXME(generic_associated_types): Currently only lifetimes are handled.
2410         self_trait_ref.substs.extend_to(tcx, item_def_id, mk_bound_param)
2411     } else {
2412         self_trait_ref.substs
2413     };
2414
2415     let assoc_ty = tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id), bound_substs);
2416
2417     let bounds = AstConv::compute_bounds(
2418         &ItemCtxt::new(tcx, def_id),
2419         assoc_ty,
2420         bounds,
2421         SizedByDefault::Yes,
2422         trait_item.span,
2423     );
2424
2425     let predicates = bounds.predicates(tcx, assoc_ty);
2426
2427     if is_gat {
2428         // We use shifts to get the regions that we're substituting to
2429         // be bound by the binders in the `Predicate`s rather that
2430         // escaping.
2431         let shifted_in = ty::fold::shift_vars(tcx, &predicates, 1);
2432         let substituted = shifted_in.subst(tcx, bound_substs);
2433         ty::fold::shift_out_vars(tcx, &substituted, 1)
2434     } else {
2435         predicates
2436     }
2437 }
2438
2439 /// Converts a specific `GenericBound` from the AST into a set of
2440 /// predicates that apply to the self type. A vector is returned
2441 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2442 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2443 /// and `<T as Bar>::X == i32`).
2444 fn predicates_from_bound<'tcx>(
2445     astconv: &dyn AstConv<'tcx>,
2446     param_ty: Ty<'tcx>,
2447     bound: &'tcx hir::GenericBound<'tcx>,
2448 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2449     match *bound {
2450         hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2451             let mut bounds = Bounds::default();
2452             let _ = astconv.instantiate_poly_trait_ref(tr, param_ty, &mut bounds);
2453             bounds.predicates(astconv.tcx(), param_ty)
2454         }
2455         hir::GenericBound::Outlives(ref lifetime) => {
2456             let region = astconv.ast_region_to_region(lifetime, None);
2457             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2458             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2459         }
2460         hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2461     }
2462 }
2463
2464 fn compute_sig_of_foreign_fn_decl<'tcx>(
2465     tcx: TyCtxt<'tcx>,
2466     def_id: DefId,
2467     decl: &'tcx hir::FnDecl<'tcx>,
2468     abi: abi::Abi,
2469 ) -> ty::PolyFnSig<'tcx> {
2470     let unsafety = if abi == abi::Abi::RustIntrinsic {
2471         intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2472     } else {
2473         hir::Unsafety::Unsafe
2474     };
2475     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
2476
2477     // Feature gate SIMD types in FFI, since I am not sure that the
2478     // ABIs are handled at all correctly. -huonw
2479     if abi != abi::Abi::RustIntrinsic
2480         && abi != abi::Abi::PlatformIntrinsic
2481         && !tcx.features().simd_ffi
2482     {
2483         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2484             if ty.is_simd() {
2485                 tcx.sess
2486                     .struct_span_err(
2487                         ast_ty.span,
2488                         &format!(
2489                             "use of SIMD type `{}` in FFI is highly experimental and \
2490                             may result in invalid code",
2491                             tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2492                         ),
2493                     )
2494                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2495                     .emit();
2496             }
2497         };
2498         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2499             check(&input, ty)
2500         }
2501         if let hir::Return(ref ty) = decl.output {
2502             check(&ty, *fty.output().skip_binder())
2503         }
2504     }
2505
2506     fty
2507 }
2508
2509 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2510     match tcx.hir().get_if_local(def_id) {
2511         Some(Node::ForeignItem(..)) => true,
2512         Some(_) => false,
2513         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2514     }
2515 }
2516
2517 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2518     match tcx.hir().get_if_local(def_id) {
2519         Some(Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. }))
2520         | Some(Node::ForeignItem(&hir::ForeignItem {
2521             kind: hir::ForeignItemKind::Static(_, mutbl),
2522             ..
2523         })) => Some(mutbl),
2524         Some(_) => None,
2525         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2526     }
2527 }
2528
2529 fn from_target_feature(
2530     tcx: TyCtxt<'_>,
2531     id: DefId,
2532     attr: &ast::Attribute,
2533     whitelist: &FxHashMap<String, Option<Symbol>>,
2534     target_features: &mut Vec<Symbol>,
2535 ) {
2536     let list = match attr.meta_item_list() {
2537         Some(list) => list,
2538         None => return,
2539     };
2540     let bad_item = |span| {
2541         let msg = "malformed `target_feature` attribute input";
2542         let code = "enable = \"..\"".to_owned();
2543         tcx.sess
2544             .struct_span_err(span, &msg)
2545             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2546             .emit();
2547     };
2548     let rust_features = tcx.features();
2549     for item in list {
2550         // Only `enable = ...` is accepted in the meta-item list.
2551         if !item.check_name(sym::enable) {
2552             bad_item(item.span());
2553             continue;
2554         }
2555
2556         // Must be of the form `enable = "..."` (a string).
2557         let value = match item.value_str() {
2558             Some(value) => value,
2559             None => {
2560                 bad_item(item.span());
2561                 continue;
2562             }
2563         };
2564
2565         // We allow comma separation to enable multiple features.
2566         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2567             // Only allow whitelisted features per platform.
2568             let feature_gate = match whitelist.get(feature) {
2569                 Some(g) => g,
2570                 None => {
2571                     let msg =
2572                         format!("the feature named `{}` is not valid for this target", feature);
2573                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2574                     err.span_label(
2575                         item.span(),
2576                         format!("`{}` is not valid for this target", feature),
2577                     );
2578                     if feature.starts_with("+") {
2579                         let valid = whitelist.contains_key(&feature[1..]);
2580                         if valid {
2581                             err.help("consider removing the leading `+` in the feature name");
2582                         }
2583                     }
2584                     err.emit();
2585                     return None;
2586                 }
2587             };
2588
2589             // Only allow features whose feature gates have been enabled.
2590             let allowed = match feature_gate.as_ref().map(|s| *s) {
2591                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2592                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2593                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2594                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2595                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2596                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2597                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2598                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2599                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2600                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2601                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2602                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2603                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2604                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2605                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2606                 Some(name) => bug!("unknown target feature gate {}", name),
2607                 None => true,
2608             };
2609             if !allowed && id.is_local() {
2610                 feature_gate::feature_err(
2611                     &tcx.sess.parse_sess,
2612                     feature_gate.unwrap(),
2613                     item.span(),
2614                     &format!("the target feature `{}` is currently unstable", feature),
2615                 )
2616                 .emit();
2617             }
2618             Some(Symbol::intern(feature))
2619         }));
2620     }
2621 }
2622
2623 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2624     use rustc::mir::mono::Linkage::*;
2625
2626     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2627     // applicable to variable declarations and may not really make sense for
2628     // Rust code in the first place but whitelist them anyway and trust that
2629     // the user knows what s/he's doing. Who knows, unanticipated use cases
2630     // may pop up in the future.
2631     //
2632     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2633     // and don't have to be, LLVM treats them as no-ops.
2634     match name {
2635         "appending" => Appending,
2636         "available_externally" => AvailableExternally,
2637         "common" => Common,
2638         "extern_weak" => ExternalWeak,
2639         "external" => External,
2640         "internal" => Internal,
2641         "linkonce" => LinkOnceAny,
2642         "linkonce_odr" => LinkOnceODR,
2643         "private" => Private,
2644         "weak" => WeakAny,
2645         "weak_odr" => WeakODR,
2646         _ => {
2647             let span = tcx.hir().span_if_local(def_id);
2648             if let Some(span) = span {
2649                 tcx.sess.span_fatal(span, "invalid linkage specified")
2650             } else {
2651                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2652             }
2653         }
2654     }
2655 }
2656
2657 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2658     let attrs = tcx.get_attrs(id);
2659
2660     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2661
2662     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2663
2664     let mut inline_span = None;
2665     let mut link_ordinal_span = None;
2666     for attr in attrs.iter() {
2667         if attr.check_name(sym::cold) {
2668             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2669         } else if attr.check_name(sym::rustc_allocator) {
2670             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2671         } else if attr.check_name(sym::unwind) {
2672             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2673         } else if attr.check_name(sym::ffi_returns_twice) {
2674             if tcx.is_foreign_item(id) {
2675                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2676             } else {
2677                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2678                 struct_span_err!(
2679                     tcx.sess,
2680                     attr.span,
2681                     E0724,
2682                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2683                 )
2684                 .emit();
2685             }
2686         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2687             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2688         } else if attr.check_name(sym::naked) {
2689             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2690         } else if attr.check_name(sym::no_mangle) {
2691             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2692         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2693             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2694         } else if attr.check_name(sym::no_debug) {
2695             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2696         } else if attr.check_name(sym::used) {
2697             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2698         } else if attr.check_name(sym::thread_local) {
2699             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2700         } else if attr.check_name(sym::track_caller) {
2701             if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2702                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2703                     .emit();
2704             }
2705             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2706         } else if attr.check_name(sym::export_name) {
2707             if let Some(s) = attr.value_str() {
2708                 if s.as_str().contains("\0") {
2709                     // `#[export_name = ...]` will be converted to a null-terminated string,
2710                     // so it may not contain any null characters.
2711                     struct_span_err!(
2712                         tcx.sess,
2713                         attr.span,
2714                         E0648,
2715                         "`export_name` may not contain null characters"
2716                     )
2717                     .emit();
2718                 }
2719                 codegen_fn_attrs.export_name = Some(s);
2720             }
2721         } else if attr.check_name(sym::target_feature) {
2722             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2723                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2724                 tcx.sess
2725                     .struct_span_err(attr.span, msg)
2726                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2727                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2728                     .emit();
2729             }
2730             from_target_feature(tcx, id, attr, &whitelist, &mut codegen_fn_attrs.target_features);
2731         } else if attr.check_name(sym::linkage) {
2732             if let Some(val) = attr.value_str() {
2733                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2734             }
2735         } else if attr.check_name(sym::link_section) {
2736             if let Some(val) = attr.value_str() {
2737                 if val.as_str().bytes().any(|b| b == 0) {
2738                     let msg = format!(
2739                         "illegal null byte in link_section \
2740                          value: `{}`",
2741                         &val
2742                     );
2743                     tcx.sess.span_err(attr.span, &msg);
2744                 } else {
2745                     codegen_fn_attrs.link_section = Some(val);
2746                 }
2747             }
2748         } else if attr.check_name(sym::link_name) {
2749             codegen_fn_attrs.link_name = attr.value_str();
2750         } else if attr.check_name(sym::link_ordinal) {
2751             link_ordinal_span = Some(attr.span);
2752             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2753                 codegen_fn_attrs.link_ordinal = ordinal;
2754             }
2755         }
2756     }
2757
2758     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2759         if !attr.has_name(sym::inline) {
2760             return ia;
2761         }
2762         match attr.meta().map(|i| i.kind) {
2763             Some(MetaItemKind::Word) => {
2764                 mark_used(attr);
2765                 InlineAttr::Hint
2766             }
2767             Some(MetaItemKind::List(ref items)) => {
2768                 mark_used(attr);
2769                 inline_span = Some(attr.span);
2770                 if items.len() != 1 {
2771                     span_err!(tcx.sess.diagnostic(), attr.span, E0534, "expected one argument");
2772                     InlineAttr::None
2773                 } else if list_contains_name(&items[..], sym::always) {
2774                     InlineAttr::Always
2775                 } else if list_contains_name(&items[..], sym::never) {
2776                     InlineAttr::Never
2777                 } else {
2778                     span_err!(tcx.sess.diagnostic(), items[0].span(), E0535, "invalid argument");
2779
2780                     InlineAttr::None
2781                 }
2782             }
2783             Some(MetaItemKind::NameValue(_)) => ia,
2784             None => ia,
2785         }
2786     });
2787
2788     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2789         if !attr.has_name(sym::optimize) {
2790             return ia;
2791         }
2792         let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2793         match attr.meta().map(|i| i.kind) {
2794             Some(MetaItemKind::Word) => {
2795                 err(attr.span, "expected one argument");
2796                 ia
2797             }
2798             Some(MetaItemKind::List(ref items)) => {
2799                 mark_used(attr);
2800                 inline_span = Some(attr.span);
2801                 if items.len() != 1 {
2802                     err(attr.span, "expected one argument");
2803                     OptimizeAttr::None
2804                 } else if list_contains_name(&items[..], sym::size) {
2805                     OptimizeAttr::Size
2806                 } else if list_contains_name(&items[..], sym::speed) {
2807                     OptimizeAttr::Speed
2808                 } else {
2809                     err(items[0].span(), "invalid argument");
2810                     OptimizeAttr::None
2811                 }
2812             }
2813             Some(MetaItemKind::NameValue(_)) => ia,
2814             None => ia,
2815         }
2816     });
2817
2818     // If a function uses #[target_feature] it can't be inlined into general
2819     // purpose functions as they wouldn't have the right target features
2820     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2821     // respected.
2822
2823     if codegen_fn_attrs.target_features.len() > 0 {
2824         if codegen_fn_attrs.inline == InlineAttr::Always {
2825             if let Some(span) = inline_span {
2826                 tcx.sess.span_err(
2827                     span,
2828                     "cannot use `#[inline(always)]` with \
2829                      `#[target_feature]`",
2830                 );
2831             }
2832         }
2833     }
2834
2835     // Weak lang items have the same semantics as "std internal" symbols in the
2836     // sense that they're preserved through all our LTO passes and only
2837     // strippable by the linker.
2838     //
2839     // Additionally weak lang items have predetermined symbol names.
2840     if tcx.is_weak_lang_item(id) {
2841         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2842     }
2843     if let Some(name) = weak_lang_items::link_name(&attrs) {
2844         codegen_fn_attrs.export_name = Some(name);
2845         codegen_fn_attrs.link_name = Some(name);
2846     }
2847     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2848
2849     // Internal symbols to the standard library all have no_mangle semantics in
2850     // that they have defined symbol names present in the function name. This
2851     // also applies to weak symbols where they all have known symbol names.
2852     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2853         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2854     }
2855
2856     codegen_fn_attrs
2857 }
2858
2859 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2860     use syntax::ast::{Lit, LitIntType, LitKind};
2861     let meta_item_list = attr.meta_item_list();
2862     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2863     let sole_meta_list = match meta_item_list {
2864         Some([item]) => item.literal(),
2865         _ => None,
2866     };
2867     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2868         if *ordinal <= std::usize::MAX as u128 {
2869             Some(*ordinal as usize)
2870         } else {
2871             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2872             tcx.sess
2873                 .struct_span_err(attr.span, &msg)
2874                 .note("the value may not exceed `std::usize::MAX`")
2875                 .emit();
2876             None
2877         }
2878     } else {
2879         tcx.sess
2880             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2881             .note("an unsuffixed integer value, e.g., `1`, is expected")
2882             .emit();
2883         None
2884     }
2885 }
2886
2887 fn check_link_name_xor_ordinal(
2888     tcx: TyCtxt<'_>,
2889     codegen_fn_attrs: &CodegenFnAttrs,
2890     inline_span: Option<Span>,
2891 ) {
2892     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2893         return;
2894     }
2895     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2896     if let Some(span) = inline_span {
2897         tcx.sess.span_err(span, msg);
2898     } else {
2899         tcx.sess.err(msg);
2900     }
2901 }