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