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