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