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 *interprocedural* 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};
  18 use crate::constrained_generic_params as cgp;
  19 use crate::check::intrinsic::intrisic_operation_unsafety;
  20 use crate::lint;
  21 use crate::middle::lang_items::SizedTraitLangItem;
  22 use crate::middle::resolve_lifetime as rl;
  23 use crate::middle::weak_lang_items;
  24 use rustc::mir::mono::Linkage;
  25 use rustc::ty::query::Providers;
  26 use rustc::ty::subst::{Subst, InternalSubsts};
  27 use rustc::ty::util::Discr;
  28 use rustc::ty::util::IntTypeExt;
  29 use rustc::ty::subst::UnpackedKind;
  30 use rustc::ty::{self, AdtKind, ToPolyTraitRef, Ty, TyCtxt};
  31 use rustc::ty::{ReprOptions, ToPredicate};
  32 use rustc::util::captures::Captures;
  33 use rustc::util::nodemap::FxHashMap;
  34 use rustc_target::spec::abi;
  35
  36 use syntax::ast;
  37 use syntax::ast::{Ident, MetaItemKind};
  38 use syntax::attr::{InlineAttr, OptimizeAttr, list_contains_name, mark_used};
  39 use syntax::source_map::Spanned;
  40 use syntax::feature_gate;
  41 use syntax::symbol::{InternedString, kw, Symbol, sym};
  42 use syntax_pos::{Span, DUMMY_SP};
  43
  44 use rustc::hir::def::{CtorKind, Res, DefKind};
  45 use rustc::hir::Node;
  46 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  47 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  48 use rustc::hir::GenericParamKind;
  49 use rustc::hir::{self, CodegenFnAttrFlags, CodegenFnAttrs, Unsafety};
  50
  51 use errors::Applicability;
  52
  53 use std::iter;
  54
  55 struct OnlySelfBounds(bool);
  56
  57 ///////////////////////////////////////////////////////////////////////////
  58 // Main entry point
  59
  60 fn collect_mod_item_types<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>, module_def_id: DefId) {
  61     tcx.hir().visit_item_likes_in_module(
  62         module_def_id,
  63         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor()
  64     );
  65 }
  66
  67 pub fn provide(providers: &mut Providers<'_>) {
  68     *providers = Providers {
  69         type_of,
  70         generics_of,
  71         predicates_of,
  72         predicates_defined_on,
  73         explicit_predicates_of,
  74         super_predicates_of,
  75         type_param_predicates,
  76         trait_def,
  77         adt_def,
  78         fn_sig,
  79         impl_trait_ref,
  80         impl_polarity,
  81         is_foreign_item,
  82         static_mutability,
  83         codegen_fn_attrs,
  84         collect_mod_item_types,
  85         ..*providers
  86     };
  87 }
  88
  89 ///////////////////////////////////////////////////////////////////////////
  90
  91 /// Context specific to some particular item. This is what implements
  92 /// `AstConv`. It has information about the predicates that are defined
  93 /// on the trait. Unfortunately, this predicate information is
  94 /// available in various different forms at various points in the
  95 /// process. So we can't just store a pointer to e.g., the AST or the
  96 /// parsed ty form, we have to be more flexible. To this end, the
  97 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  98 /// `get_type_parameter_bounds` requests, drawing the information from
  99 /// the AST (`hir::Generics`), recursively.
 100 pub struct ItemCtxt<'a, 'tcx: 'a> {
 101     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 102     item_def_id: DefId,
 103 }
 104
 105 ///////////////////////////////////////////////////////////////////////////
 106
 107 struct CollectItemTypesVisitor<'a, 'tcx: 'a> {
 108     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 109 }
 110
 111 impl<'a, 'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'a, 'tcx> {
 112     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 113         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 114     }
 115
 116     fn visit_item(&mut self, item: &'tcx hir::Item) {
 117         convert_item(self.tcx, item.hir_id);
 118         intravisit::walk_item(self, item);
 119     }
 120
 121     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
 122         for param in &generics.params {
 123             match param.kind {
 124                 hir::GenericParamKind::Lifetime { .. } => {}
 125                 hir::GenericParamKind::Type {
 126                     default: Some(_), ..
 127                 } => {
 128                     let def_id = self.tcx.hir().local_def_id_from_hir_id(param.hir_id);
 129                     self.tcx.type_of(def_id);
 130                 }
 131                 hir::GenericParamKind::Type { .. } => {}
 132                 hir::GenericParamKind::Const { .. } => {
 133                     let def_id = self.tcx.hir().local_def_id_from_hir_id(param.hir_id);
 134                     self.tcx.type_of(def_id);
 135                 }
 136             }
 137         }
 138         intravisit::walk_generics(self, generics);
 139     }
 140
 141     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 142         if let hir::ExprKind::Closure(..) = expr.node {
 143             let def_id = self.tcx.hir().local_def_id_from_hir_id(expr.hir_id);
 144             self.tcx.generics_of(def_id);
 145             self.tcx.type_of(def_id);
 146         }
 147         intravisit::walk_expr(self, expr);
 148     }
 149
 150     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
 151         convert_trait_item(self.tcx, trait_item.hir_id);
 152         intravisit::walk_trait_item(self, trait_item);
 153     }
 154
 155     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
 156         convert_impl_item(self.tcx, impl_item.hir_id);
 157         intravisit::walk_impl_item(self, impl_item);
 158     }
 159 }
 160
 161 ///////////////////////////////////////////////////////////////////////////
 162 // Utility types and common code for the above passes.
 163
 164 impl<'a, 'tcx> ItemCtxt<'a, 'tcx> {
 165     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, item_def_id: DefId) -> ItemCtxt<'a, 'tcx> {
 166         ItemCtxt { tcx, item_def_id }
 167     }
 168 }
 169
 170 impl<'a, 'tcx> ItemCtxt<'a, 'tcx> {
 171     pub fn to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
 172         AstConv::ast_ty_to_ty(self, ast_ty)
 173     }
 174 }
 175
 176 impl<'a, 'tcx> AstConv<'tcx, 'tcx> for ItemCtxt<'a, 'tcx> {
 177     fn tcx<'b>(&'b self) -> TyCtxt<'b, 'tcx, 'tcx> {
 178         self.tcx
 179     }
 180
 181     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
 182                                  -> &'tcx ty::GenericPredicates<'tcx> {
 183         self.tcx
 184             .at(span)
 185             .type_param_predicates((self.item_def_id, def_id))
 186     }
 187
 188     fn re_infer(
 189         &self,
 190         _span: Span,
 191         _def: Option<&ty::GenericParamDef>,
 192     ) -> Option<ty::Region<'tcx>> {
 193         None
 194     }
 195
 196     fn ty_infer(&self, span: Span) -> Ty<'tcx> {
 197         struct_span_err!(
 198             self.tcx().sess,
 199             span,
 200             E0121,
 201             "the type placeholder `_` is not allowed within types on item signatures"
 202         ).span_label(span, "not allowed in type signatures")
 203          .emit();
 204
 205         self.tcx().types.err
 206     }
 207
 208     fn projected_ty_from_poly_trait_ref(
 209         &self,
 210         span: Span,
 211         item_def_id: DefId,
 212         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 213     ) -> Ty<'tcx> {
 214         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 215             self.tcx().mk_projection(item_def_id, trait_ref.substs)
 216         } else {
 217             // no late-bound regions, we can just ignore the binder
 218             span_err!(
 219                 self.tcx().sess,
 220                 span,
 221                 E0212,
 222                 "cannot extract an associated type from a higher-ranked trait bound \
 223                  in this context"
 224             );
 225             self.tcx().types.err
 226         }
 227     }
 228
 229     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 230         // types in item signatures are not normalized, to avoid undue
 231         // dependencies.
 232         ty
 233     }
 234
 235     fn set_tainted_by_errors(&self) {
 236         // no obvious place to track this, just let it go
 237     }
 238
 239     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 240         // no place to record types from signatures?
 241     }
 242 }
 243
 244 fn type_param_predicates<'a, 'tcx>(
 245     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 246     (item_def_id, def_id): (DefId, DefId),
 247 ) -> &'tcx ty::GenericPredicates<'tcx> {
 248     use rustc::hir::*;
 249
 250     // In the AST, bounds can derive from two places. Either
 251     // written inline like `<T : Foo>` or in a where clause like
 252     // `where T : Foo`.
 253
 254     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 255     let param_owner = tcx.hir().ty_param_owner(param_id);
 256     let param_owner_def_id = tcx.hir().local_def_id_from_hir_id(param_owner);
 257     let generics = tcx.generics_of(param_owner_def_id);
 258     let index = generics.param_def_id_to_index[&def_id];
 259     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id).as_interned_str());
 260
 261     // Don't look for bounds where the type parameter isn't in scope.
 262     let parent = if item_def_id == param_owner_def_id {
 263         None
 264     } else {
 265         tcx.generics_of(item_def_id).parent
 266     };
 267
 268     let result = parent.map_or(&tcx.common.empty_predicates, |parent| {
 269         let icx = ItemCtxt::new(tcx, parent);
 270         icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 271     });
 272     let mut extend = None;
 273
 274     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 275     let ast_generics = match tcx.hir().get_by_hir_id(item_hir_id) {
 276         Node::TraitItem(item) => &item.generics,
 277
 278         Node::ImplItem(item) => &item.generics,
 279
 280         Node::Item(item) => {
 281             match item.node {
 282                 ItemKind::Fn(.., ref generics, _)
 283                 | ItemKind::Impl(_, _, _, ref generics, ..)
 284                 | ItemKind::Ty(_, ref generics)
 285                 | ItemKind::Existential(ExistTy {
 286                     ref generics,
 287                     impl_trait_fn: None,
 288                     ..
 289                 })
 290                 | ItemKind::Enum(_, ref generics)
 291                 | ItemKind::Struct(_, ref generics)
 292                 | ItemKind::Union(_, ref generics) => generics,
 293                 ItemKind::Trait(_, _, ref generics, ..) => {
 294                     // Implied `Self: Trait` and supertrait bounds.
 295                     if param_id == item_hir_id {
 296                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 297                         extend = Some((identity_trait_ref.to_predicate(), item.span));
 298                     }
 299                     generics
 300                 }
 301                 _ => return result,
 302             }
 303         }
 304
 305         Node::ForeignItem(item) => match item.node {
 306             ForeignItemKind::Fn(_, _, ref generics) => generics,
 307             _ => return result,
 308         },
 309
 310         _ => return result,
 311     };
 312
 313     let icx = ItemCtxt::new(tcx, item_def_id);
 314     let mut result = (*result).clone();
 315     result.predicates.extend(extend.into_iter());
 316     result.predicates
 317           .extend(icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty,
 318                   OnlySelfBounds(true)));
 319     tcx.arena.alloc(result)
 320 }
 321
 322 impl<'a, 'tcx> ItemCtxt<'a, 'tcx> {
 323     /// Finds bounds from `hir::Generics`. This requires scanning through the
 324     /// AST. We do this to avoid having to convert *all* the bounds, which
 325     /// would create artificial cycles. Instead we can only convert the
 326     /// bounds for a type parameter `X` if `X::Foo` is used.
 327     fn type_parameter_bounds_in_generics(
 328         &self,
 329         ast_generics: &hir::Generics,
 330         param_id: hir::HirId,
 331         ty: Ty<'tcx>,
 332         only_self_bounds: OnlySelfBounds,
 333     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 334         let from_ty_params = ast_generics
 335             .params
 336             .iter()
 337             .filter_map(|param| match param.kind {
 338                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 339                 _ => None,
 340             })
 341             .flat_map(|bounds| bounds.iter())
 342             .flat_map(|b| predicates_from_bound(self, ty, b));
 343
 344         let from_where_clauses = ast_generics
 345             .where_clause
 346             .predicates
 347             .iter()
 348             .filter_map(|wp| match *wp {
 349                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 350                 _ => None,
 351             })
 352             .flat_map(|bp| {
 353                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 354                     Some(ty)
 355                 } else if !only_self_bounds.0 {
 356                     Some(self.to_ty(&bp.bounded_ty))
 357                 } else {
 358                     None
 359                 };
 360                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 361             })
 362             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
 363
 364         from_ty_params.chain(from_where_clauses).collect()
 365     }
 366 }
 367
 368 /// Tests whether this is the AST for a reference to the type
 369 /// parameter with ID `param_id`. We use this so as to avoid running
 370 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 371 /// conversion of the type to avoid inducing unnecessary cycles.
 372 fn is_param<'a, 'tcx>(
 373     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 374     ast_ty: &hir::Ty,
 375     param_id: hir::HirId,
 376 ) -> bool {
 377     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.node {
 378         match path.res {
 379             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 380                 def_id == tcx.hir().local_def_id_from_hir_id(param_id)
 381             }
 382             _ => false,
 383         }
 384     } else {
 385         false
 386     }
 387 }
 388
 389 fn convert_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item_id: hir::HirId) {
 390     let it = tcx.hir().expect_item_by_hir_id(item_id);
 391     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 392     let def_id = tcx.hir().local_def_id_from_hir_id(item_id);
 393     match it.node {
 394         // These don't define types.
 395         hir::ItemKind::ExternCrate(_)
 396         | hir::ItemKind::Use(..)
 397         | hir::ItemKind::Mod(_)
 398         | hir::ItemKind::GlobalAsm(_) => {}
 399         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 400             for item in &foreign_mod.items {
 401                 let def_id = tcx.hir().local_def_id_from_hir_id(item.hir_id);
 402                 tcx.generics_of(def_id);
 403                 tcx.type_of(def_id);
 404                 tcx.predicates_of(def_id);
 405                 if let hir::ForeignItemKind::Fn(..) = item.node {
 406                     tcx.fn_sig(def_id);
 407                 }
 408             }
 409         }
 410         hir::ItemKind::Enum(ref enum_definition, _) => {
 411             tcx.generics_of(def_id);
 412             tcx.type_of(def_id);
 413             tcx.predicates_of(def_id);
 414             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 415         }
 416         hir::ItemKind::Impl(..) => {
 417             tcx.generics_of(def_id);
 418             tcx.type_of(def_id);
 419             tcx.impl_trait_ref(def_id);
 420             tcx.predicates_of(def_id);
 421         }
 422         hir::ItemKind::Trait(..) => {
 423             tcx.generics_of(def_id);
 424             tcx.trait_def(def_id);
 425             tcx.at(it.span).super_predicates_of(def_id);
 426             tcx.predicates_of(def_id);
 427         }
 428         hir::ItemKind::TraitAlias(..) => {
 429             tcx.generics_of(def_id);
 430             tcx.at(it.span).super_predicates_of(def_id);
 431             tcx.predicates_of(def_id);
 432         }
 433         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 434             tcx.generics_of(def_id);
 435             tcx.type_of(def_id);
 436             tcx.predicates_of(def_id);
 437
 438             for f in struct_def.fields() {
 439                 let def_id = tcx.hir().local_def_id_from_hir_id(f.hir_id);
 440                 tcx.generics_of(def_id);
 441                 tcx.type_of(def_id);
 442                 tcx.predicates_of(def_id);
 443             }
 444
 445             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 446                 convert_variant_ctor(tcx, ctor_hir_id);
 447             }
 448         }
 449
 450         // Desugared from `impl Trait` -> visited by the function's return type
 451         hir::ItemKind::Existential(hir::ExistTy {
 452             impl_trait_fn: Some(_),
 453             ..
 454         }) => {}
 455
 456         hir::ItemKind::Existential(..)
 457         | hir::ItemKind::Ty(..)
 458         | hir::ItemKind::Static(..)
 459         | hir::ItemKind::Const(..)
 460         | hir::ItemKind::Fn(..) => {
 461             tcx.generics_of(def_id);
 462             tcx.type_of(def_id);
 463             tcx.predicates_of(def_id);
 464             if let hir::ItemKind::Fn(..) = it.node {
 465                 tcx.fn_sig(def_id);
 466             }
 467         }
 468     }
 469 }
 470
 471 fn convert_trait_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, trait_item_id: hir::HirId) {
 472     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 473     let def_id = tcx.hir().local_def_id_from_hir_id(trait_item.hir_id);
 474     tcx.generics_of(def_id);
 475
 476     match trait_item.node {
 477         hir::TraitItemKind::Const(..)
 478         | hir::TraitItemKind::Type(_, Some(_))
 479         | hir::TraitItemKind::Method(..) => {
 480             tcx.type_of(def_id);
 481             if let hir::TraitItemKind::Method(..) = trait_item.node {
 482                 tcx.fn_sig(def_id);
 483             }
 484         }
 485
 486         hir::TraitItemKind::Type(_, None) => {}
 487     };
 488
 489     tcx.predicates_of(def_id);
 490 }
 491
 492 fn convert_impl_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, impl_item_id: hir::HirId) {
 493     let def_id = tcx.hir().local_def_id_from_hir_id(impl_item_id);
 494     tcx.generics_of(def_id);
 495     tcx.type_of(def_id);
 496     tcx.predicates_of(def_id);
 497     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).node {
 498         tcx.fn_sig(def_id);
 499     }
 500 }
 501
 502 fn convert_variant_ctor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ctor_id: hir::HirId) {
 503     let def_id = tcx.hir().local_def_id_from_hir_id(ctor_id);
 504     tcx.generics_of(def_id);
 505     tcx.type_of(def_id);
 506     tcx.predicates_of(def_id);
 507 }
 508
 509 fn convert_enum_variant_types<'a, 'tcx>(
 510     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 511     def_id: DefId,
 512     variants: &[hir::Variant],
 513 ) {
 514     let def = tcx.adt_def(def_id);
 515     let repr_type = def.repr.discr_type();
 516     let initial = repr_type.initial_discriminant(tcx);
 517     let mut prev_discr = None::<Discr<'tcx>>;
 518
 519     // fill the discriminant values and field types
 520     for variant in variants {
 521         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 522         prev_discr = Some(
 523             if let Some(ref e) = variant.node.disr_expr {
 524                 let expr_did = tcx.hir().local_def_id_from_hir_id(e.hir_id);
 525                 def.eval_explicit_discr(tcx, expr_did)
 526             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 527                 Some(discr)
 528             } else {
 529                 struct_span_err!(
 530                     tcx.sess,
 531                     variant.span,
 532                     E0370,
 533                     "enum discriminant overflowed"
 534                 ).span_label(
 535                     variant.span,
 536                     format!("overflowed on value after {}", prev_discr.unwrap()),
 537                 ).note(&format!(
 538                     "explicitly set `{} = {}` if that is desired outcome",
 539                     variant.node.ident, wrapped_discr
 540                 ))
 541                 .emit();
 542                 None
 543             }.unwrap_or(wrapped_discr),
 544         );
 545
 546         for f in variant.node.data.fields() {
 547             let def_id = tcx.hir().local_def_id_from_hir_id(f.hir_id);
 548             tcx.generics_of(def_id);
 549             tcx.type_of(def_id);
 550             tcx.predicates_of(def_id);
 551         }
 552
 553         // Convert the ctor, if any. This also registers the variant as
 554         // an item.
 555         if let Some(ctor_hir_id) = variant.node.data.ctor_hir_id() {
 556             convert_variant_ctor(tcx, ctor_hir_id);
 557         }
 558     }
 559 }
 560
 561 fn convert_variant<'a, 'tcx>(
 562     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 563     variant_did: Option<DefId>,
 564     ctor_did: Option<DefId>,
 565     ident: Ident,
 566     discr: ty::VariantDiscr,
 567     def: &hir::VariantData,
 568     adt_kind: ty::AdtKind,
 569     parent_did: DefId
 570 ) -> ty::VariantDef {
 571     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 572     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 573     let fields = def
 574         .fields()
 575         .iter()
 576         .map(|f| {
 577             let fid = tcx.hir().local_def_id_from_hir_id(f.hir_id);
 578             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 579             if let Some(prev_span) = dup_span {
 580                 struct_span_err!(
 581                     tcx.sess,
 582                     f.span,
 583                     E0124,
 584                     "field `{}` is already declared",
 585                     f.ident
 586                 ).span_label(f.span, "field already declared")
 587                  .span_label(prev_span, format!("`{}` first declared here", f.ident))
 588                  .emit();
 589             } else {
 590                 seen_fields.insert(f.ident.modern(), f.span);
 591             }
 592
 593             ty::FieldDef {
 594                 did: fid,
 595                 ident: f.ident,
 596                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 597             }
 598         })
 599         .collect();
 600     let recovered = match def {
 601         hir::VariantData::Struct(_, r) => *r,
 602         _ => false,
 603     };
 604     ty::VariantDef::new(
 605         tcx,
 606         ident,
 607         variant_did,
 608         ctor_did,
 609         discr,
 610         fields,
 611         CtorKind::from_hir(def),
 612         adt_kind,
 613         parent_did,
 614         recovered,
 615     )
 616 }
 617
 618 fn adt_def<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx ty::AdtDef {
 619     use rustc::hir::*;
 620
 621     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 622     let item = match tcx.hir().get_by_hir_id(hir_id) {
 623         Node::Item(item) => item,
 624         _ => bug!(),
 625     };
 626
 627     let repr = ReprOptions::new(tcx, def_id);
 628     let (kind, variants) = match item.node {
 629         ItemKind::Enum(ref def, _) => {
 630             let mut distance_from_explicit = 0;
 631             let variants = def.variants
 632                 .iter()
 633                 .map(|v| {
 634                     let variant_did = Some(tcx.hir().local_def_id_from_hir_id(v.node.id));
 635                     let ctor_did = v.node.data.ctor_hir_id()
 636                         .map(|hir_id| tcx.hir().local_def_id_from_hir_id(hir_id));
 637
 638                     let discr = if let Some(ref e) = v.node.disr_expr {
 639                         distance_from_explicit = 0;
 640                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id_from_hir_id(e.hir_id))
 641                     } else {
 642                         ty::VariantDiscr::Relative(distance_from_explicit)
 643                     };
 644                     distance_from_explicit += 1;
 645
 646                     convert_variant(tcx, variant_did, ctor_did, v.node.ident, discr,
 647                                     &v.node.data, AdtKind::Enum, def_id)
 648                 })
 649                 .collect();
 650
 651             (AdtKind::Enum, variants)
 652         }
 653         ItemKind::Struct(ref def, _) => {
 654             let variant_did = None;
 655             let ctor_did = def.ctor_hir_id()
 656                 .map(|hir_id| tcx.hir().local_def_id_from_hir_id(hir_id));
 657
 658             let variants = std::iter::once(convert_variant(
 659                 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
 660                 AdtKind::Struct, def_id,
 661             )).collect();
 662
 663             (AdtKind::Struct, variants)
 664         }
 665         ItemKind::Union(ref def, _) => {
 666             let variant_did = None;
 667             let ctor_did = def.ctor_hir_id()
 668                 .map(|hir_id| tcx.hir().local_def_id_from_hir_id(hir_id));
 669
 670             let variants = std::iter::once(convert_variant(
 671                 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
 672                 AdtKind::Union, def_id,
 673             )).collect();
 674
 675             (AdtKind::Union, variants)
 676         },
 677         _ => bug!(),
 678     };
 679     tcx.alloc_adt_def(def_id, kind, variants, repr)
 680 }
 681
 682 /// Ensures that the super-predicates of the trait with a `DefId`
 683 /// of `trait_def_id` are converted and stored. This also ensures that
 684 /// the transitive super-predicates are converted.
 685 fn super_predicates_of<'a, 'tcx>(
 686     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 687     trait_def_id: DefId,
 688 ) -> &'tcx ty::GenericPredicates<'tcx> {
 689     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 690     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 691
 692     let item = match tcx.hir().get_by_hir_id(trait_hir_id) {
 693         Node::Item(item) => item,
 694         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 695     };
 696
 697     let (generics, bounds) = match item.node {
 698         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 699         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 700         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 701     };
 702
 703     let icx = ItemCtxt::new(tcx, trait_def_id);
 704
 705     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 706     let self_param_ty = tcx.mk_self_type();
 707     let superbounds1 = compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No, item.span);
 708
 709     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 710
 711     // Convert any explicit superbounds in the where-clause,
 712     // e.g., `trait Foo where Self: Bar`.
 713     // In the case of trait aliases, however, we include all bounds in the where-clause,
 714     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 715     // as one of its "superpredicates".
 716     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 717     let superbounds2 = icx.type_parameter_bounds_in_generics(
 718         generics, item.hir_id, self_param_ty, OnlySelfBounds(!is_trait_alias));
 719
 720     // Combine the two lists to form the complete set of superbounds:
 721     let superbounds: Vec<_> = superbounds1.into_iter().chain(superbounds2).collect();
 722
 723     // Now require that immediate supertraits are converted,
 724     // which will, in turn, reach indirect supertraits.
 725     for &(pred, span) in &superbounds {
 726         debug!("superbound: {:?}", pred);
 727         if let ty::Predicate::Trait(bound) = pred {
 728             tcx.at(span).super_predicates_of(bound.def_id());
 729         }
 730     }
 731
 732     tcx.arena.alloc(ty::GenericPredicates {
 733         parent: None,
 734         predicates: superbounds,
 735     })
 736 }
 737
 738 fn trait_def<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx ty::TraitDef {
 739     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 740     let item = tcx.hir().expect_item_by_hir_id(hir_id);
 741
 742     let (is_auto, unsafety) = match item.node {
 743         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 744         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 745         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 746     };
 747
 748     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 749     if paren_sugar && !tcx.features().unboxed_closures {
 750         let mut err = tcx.sess.struct_span_err(
 751             item.span,
 752             "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 753              which traits can use parenthetical notation",
 754         );
 755         help!(
 756             &mut err,
 757             "add `#![feature(unboxed_closures)]` to \
 758              the crate attributes to use it"
 759         );
 760         err.emit();
 761     }
 762
 763     let is_marker = tcx.has_attr(def_id, sym::marker);
 764     let def_path_hash = tcx.def_path_hash(def_id);
 765     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 766     tcx.alloc_trait_def(def)
 767 }
 768
 769 fn has_late_bound_regions<'a, 'tcx>(
 770     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 771     node: Node<'tcx>,
 772 ) -> Option<Span> {
 773     struct LateBoundRegionsDetector<'a, 'tcx: 'a> {
 774         tcx: TyCtxt<'a, 'tcx, 'tcx>,
 775         outer_index: ty::DebruijnIndex,
 776         has_late_bound_regions: Option<Span>,
 777     }
 778
 779     impl<'a, 'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'a, 'tcx> {
 780         fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 781             NestedVisitorMap::None
 782         }
 783
 784         fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
 785             if self.has_late_bound_regions.is_some() {
 786                 return;
 787             }
 788             match ty.node {
 789                 hir::TyKind::BareFn(..) => {
 790                     self.outer_index.shift_in(1);
 791                     intravisit::walk_ty(self, ty);
 792                     self.outer_index.shift_out(1);
 793                 }
 794                 _ => intravisit::walk_ty(self, ty),
 795             }
 796         }
 797
 798         fn visit_poly_trait_ref(
 799             &mut self,
 800             tr: &'tcx hir::PolyTraitRef,
 801             m: hir::TraitBoundModifier,
 802         ) {
 803             if self.has_late_bound_regions.is_some() {
 804                 return;
 805             }
 806             self.outer_index.shift_in(1);
 807             intravisit::walk_poly_trait_ref(self, tr, m);
 808             self.outer_index.shift_out(1);
 809         }
 810
 811         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 812             if self.has_late_bound_regions.is_some() {
 813                 return;
 814             }
 815
 816             match self.tcx.named_region(lt.hir_id) {
 817                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 818                 Some(rl::Region::LateBound(debruijn, _, _))
 819                 | Some(rl::Region::LateBoundAnon(debruijn, _)) if debruijn < self.outer_index => {}
 820                 Some(rl::Region::LateBound(..))
 821                 | Some(rl::Region::LateBoundAnon(..))
 822                 | Some(rl::Region::Free(..))
 823                 | None => {
 824                     self.has_late_bound_regions = Some(lt.span);
 825                 }
 826             }
 827         }
 828     }
 829
 830     fn has_late_bound_regions<'a, 'tcx>(
 831         tcx: TyCtxt<'a, 'tcx, 'tcx>,
 832         generics: &'tcx hir::Generics,
 833         decl: &'tcx hir::FnDecl,
 834     ) -> Option<Span> {
 835         let mut visitor = LateBoundRegionsDetector {
 836             tcx,
 837             outer_index: ty::INNERMOST,
 838             has_late_bound_regions: None,
 839         };
 840         for param in &generics.params {
 841             if let GenericParamKind::Lifetime { .. } = param.kind {
 842                 if tcx.is_late_bound(param.hir_id) {
 843                     return Some(param.span);
 844                 }
 845             }
 846         }
 847         visitor.visit_fn_decl(decl);
 848         visitor.has_late_bound_regions
 849     }
 850
 851     match node {
 852         Node::TraitItem(item) => match item.node {
 853             hir::TraitItemKind::Method(ref sig, _) => {
 854                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 855             }
 856             _ => None,
 857         },
 858         Node::ImplItem(item) => match item.node {
 859             hir::ImplItemKind::Method(ref sig, _) => {
 860                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 861             }
 862             _ => None,
 863         },
 864         Node::ForeignItem(item) => match item.node {
 865             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
 866                 has_late_bound_regions(tcx, generics, fn_decl)
 867             }
 868             _ => None,
 869         },
 870         Node::Item(item) => match item.node {
 871             hir::ItemKind::Fn(ref fn_decl, .., ref generics, _) => {
 872                 has_late_bound_regions(tcx, generics, fn_decl)
 873             }
 874             _ => None,
 875         },
 876         _ => None,
 877     }
 878 }
 879
 880 fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx ty::Generics {
 881     use rustc::hir::*;
 882
 883     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 884
 885     let node = tcx.hir().get_by_hir_id(hir_id);
 886     let parent_def_id = match node {
 887         Node::ImplItem(_) | Node::TraitItem(_) | Node::Variant(_) |
 888         Node::Ctor(..) | Node::Field(_) => {
 889             let parent_id = tcx.hir().get_parent_item(hir_id);
 890             Some(tcx.hir().local_def_id_from_hir_id(parent_id))
 891         }
 892         Node::Expr(&hir::Expr {
 893             node: hir::ExprKind::Closure(..),
 894             ..
 895         }) => Some(tcx.closure_base_def_id(def_id)),
 896         Node::Item(item) => match item.node {
 897             ItemKind::Existential(hir::ExistTy { impl_trait_fn, .. }) => impl_trait_fn,
 898             _ => None,
 899         },
 900         _ => None,
 901     };
 902
 903     let mut opt_self = None;
 904     let mut allow_defaults = false;
 905
 906     let no_generics = hir::Generics::empty();
 907     let ast_generics = match node {
 908         Node::TraitItem(item) => &item.generics,
 909
 910         Node::ImplItem(item) => &item.generics,
 911
 912         Node::Item(item) => {
 913             match item.node {
 914                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
 915                     generics
 916                 }
 917
 918                 ItemKind::Ty(_, ref generics)
 919                 | ItemKind::Enum(_, ref generics)
 920                 | ItemKind::Struct(_, ref generics)
 921                 | ItemKind::Existential(hir::ExistTy { ref generics, .. })
 922                 | ItemKind::Union(_, ref generics) => {
 923                     allow_defaults = true;
 924                     generics
 925                 }
 926
 927                 ItemKind::Trait(_, _, ref generics, ..)
 928                 | ItemKind::TraitAlias(ref generics, ..) => {
 929                     // Add in the self type parameter.
 930                     //
 931                     // Something of a hack: use the node id for the trait, also as
 932                     // the node id for the Self type parameter.
 933                     let param_id = item.hir_id;
 934
 935                     opt_self = Some(ty::GenericParamDef {
 936                         index: 0,
 937                         name: kw::SelfUpper.as_interned_str(),
 938                         def_id: tcx.hir().local_def_id_from_hir_id(param_id),
 939                         pure_wrt_drop: false,
 940                         kind: ty::GenericParamDefKind::Type {
 941                             has_default: false,
 942                             object_lifetime_default: rl::Set1::Empty,
 943                             synthetic: None,
 944                         },
 945                     });
 946
 947                     allow_defaults = true;
 948                     generics
 949                 }
 950
 951                 _ => &no_generics,
 952             }
 953         }
 954
 955         Node::ForeignItem(item) => match item.node {
 956             ForeignItemKind::Static(..) => &no_generics,
 957             ForeignItemKind::Fn(_, _, ref generics) => generics,
 958             ForeignItemKind::Type => &no_generics,
 959         },
 960
 961         _ => &no_generics,
 962     };
 963
 964     let has_self = opt_self.is_some();
 965     let mut parent_has_self = false;
 966     let mut own_start = has_self as u32;
 967     let parent_count = parent_def_id.map_or(0, |def_id| {
 968         let generics = tcx.generics_of(def_id);
 969         assert_eq!(has_self, false);
 970         parent_has_self = generics.has_self;
 971         own_start = generics.count() as u32;
 972         generics.parent_count + generics.params.len()
 973     });
 974
 975     let mut params: Vec<_> = opt_self.into_iter().collect();
 976
 977     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
 978     params.extend(
 979         early_lifetimes
 980             .enumerate()
 981             .map(|(i, param)| ty::GenericParamDef {
 982                 name: param.name.ident().as_interned_str(),
 983                 index: own_start + i as u32,
 984                 def_id: tcx.hir().local_def_id_from_hir_id(param.hir_id),
 985                 pure_wrt_drop: param.pure_wrt_drop,
 986                 kind: ty::GenericParamDefKind::Lifetime,
 987             }),
 988     );
 989
 990     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
 991
 992     // Now create the real type parameters.
 993     let type_start = own_start - has_self as u32 + params.len() as u32;
 994     let mut i = 0;
 995     params.extend(
 996         ast_generics
 997             .params
 998             .iter()
 999             .filter_map(|param| {
1000                 let kind = match param.kind {
1001                     GenericParamKind::Type {
1002                         ref default,
1003                         synthetic,
1004                         ..
1005                     } => {
1006                         if param.name.ident().name == kw::SelfUpper {
1007                             span_bug!(
1008                                 param.span,
1009                                 "`Self` should not be the name of a regular parameter"
1010                             );
1011                         }
1012
1013                         if !allow_defaults && default.is_some() {
1014                             if !tcx.features().default_type_parameter_fallback {
1015                                 tcx.lint_hir(
1016                                     lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1017                                     param.hir_id,
1018                                     param.span,
1019                                     &format!(
1020                                         "defaults for type parameters are only allowed in \
1021                                         `struct`, `enum`, `type`, or `trait` definitions."
1022                                     ),
1023                                 );
1024                             }
1025                         }
1026
1027                         ty::GenericParamDefKind::Type {
1028                             has_default: default.is_some(),
1029                             object_lifetime_default: object_lifetime_defaults
1030                                 .as_ref()
1031                                 .map_or(rl::Set1::Empty, |o| o[i]),
1032                             synthetic,
1033                         }
1034                     }
1035                     GenericParamKind::Const { .. } => {
1036                         if param.name.ident().name == kw::SelfUpper {
1037                             span_bug!(
1038                                 param.span,
1039                                 "`Self` should not be the name of a regular parameter",
1040                             );
1041                         }
1042
1043                         ty::GenericParamDefKind::Const
1044                     }
1045                     _ => return None,
1046                 };
1047
1048                 let param_def = ty::GenericParamDef {
1049                     index: type_start + i as u32,
1050                     name: param.name.ident().as_interned_str(),
1051                     def_id: tcx.hir().local_def_id_from_hir_id(param.hir_id),
1052                     pure_wrt_drop: param.pure_wrt_drop,
1053                     kind,
1054                 };
1055                 i += 1;
1056                 Some(param_def)
1057             })
1058     );
1059
1060     // provide junk type parameter defs - the only place that
1061     // cares about anything but the length is instantiation,
1062     // and we don't do that for closures.
1063     if let Node::Expr(&hir::Expr {
1064         node: hir::ExprKind::Closure(.., gen),
1065         ..
1066     }) = node
1067     {
1068         let dummy_args = if gen.is_some() {
1069             &["<yield_ty>", "<return_ty>", "<witness>"][..]
1070         } else {
1071             &["<closure_kind>", "<closure_signature>"][..]
1072         };
1073
1074         params.extend(
1075             dummy_args
1076                 .iter()
1077                 .enumerate()
1078                 .map(|(i, &arg)| ty::GenericParamDef {
1079                     index: type_start + i as u32,
1080                     name: InternedString::intern(arg),
1081                     def_id,
1082                     pure_wrt_drop: false,
1083                     kind: ty::GenericParamDefKind::Type {
1084                         has_default: false,
1085                         object_lifetime_default: rl::Set1::Empty,
1086                         synthetic: None,
1087                     },
1088                 }),
1089         );
1090
1091         if let Some(upvars) = tcx.upvars(def_id) {
1092             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1093                 ty::GenericParamDef {
1094                     index: type_start + i,
1095                     name: InternedString::intern("<upvar>"),
1096                     def_id,
1097                     pure_wrt_drop: false,
1098                     kind: ty::GenericParamDefKind::Type {
1099                         has_default: false,
1100                         object_lifetime_default: rl::Set1::Empty,
1101                         synthetic: None,
1102                     },
1103                 }
1104             }));
1105         }
1106     }
1107
1108     let param_def_id_to_index = params
1109         .iter()
1110         .map(|param| (param.def_id, param.index))
1111         .collect();
1112
1113     tcx.alloc_generics(ty::Generics {
1114         parent: parent_def_id,
1115         parent_count,
1116         params,
1117         param_def_id_to_index,
1118         has_self: has_self || parent_has_self,
1119         has_late_bound_regions: has_late_bound_regions(tcx, node),
1120     })
1121 }
1122
1123 fn report_assoc_ty_on_inherent_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span) {
1124     span_err!(
1125         tcx.sess,
1126         span,
1127         E0202,
1128         "associated types are not yet supported in inherent impls (see #8995)"
1129     );
1130 }
1131
1132 fn type_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Ty<'tcx> {
1133     checked_type_of(tcx, def_id, true).unwrap()
1134 }
1135
1136 /// Same as [`type_of`] but returns [`Option`] instead of failing.
1137 ///
1138 /// If you want to fail anyway, you can set the `fail` parameter to true, but in this case,
1139 /// you'd better just call [`type_of`] directly.
1140 pub fn checked_type_of<'a, 'tcx>(
1141     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1142     def_id: DefId,
1143     fail: bool,
1144 ) -> Option<Ty<'tcx>> {
1145     use rustc::hir::*;
1146
1147     let hir_id = match tcx.hir().as_local_hir_id(def_id) {
1148         Some(hir_id) => hir_id,
1149         None => {
1150             if !fail {
1151                 return None;
1152             }
1153             bug!("invalid node");
1154         }
1155     };
1156
1157     let icx = ItemCtxt::new(tcx, def_id);
1158
1159     Some(match tcx.hir().get_by_hir_id(hir_id) {
1160         Node::TraitItem(item) => match item.node {
1161             TraitItemKind::Method(..) => {
1162                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1163                 tcx.mk_fn_def(def_id, substs)
1164             }
1165             TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1166             TraitItemKind::Type(_, None) => {
1167                 if !fail {
1168                     return None;
1169                 }
1170                 span_bug!(item.span, "associated type missing default");
1171             }
1172         },
1173
1174         Node::ImplItem(item) => match item.node {
1175             ImplItemKind::Method(..) => {
1176                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1177                 tcx.mk_fn_def(def_id, substs)
1178             }
1179             ImplItemKind::Const(ref ty, _) => icx.to_ty(ty),
1180             ImplItemKind::Existential(_) => {
1181                 if tcx
1182                     .impl_trait_ref(tcx.hir().get_parent_did_by_hir_id(hir_id))
1183                     .is_none()
1184                 {
1185                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1186                 }
1187
1188                 find_existential_constraints(tcx, def_id)
1189             }
1190             ImplItemKind::Type(ref ty) => {
1191                 if tcx
1192                     .impl_trait_ref(tcx.hir().get_parent_did_by_hir_id(hir_id))
1193                     .is_none()
1194                 {
1195                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1196                 }
1197
1198                 icx.to_ty(ty)
1199             }
1200         },
1201
1202         Node::Item(item) => {
1203             match item.node {
1204                 ItemKind::Static(ref t, ..)
1205                 | ItemKind::Const(ref t, _)
1206                 | ItemKind::Ty(ref t, _)
1207                 | ItemKind::Impl(.., ref t, _) => icx.to_ty(t),
1208                 ItemKind::Fn(..) => {
1209                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1210                     tcx.mk_fn_def(def_id, substs)
1211                 }
1212                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1213                     let def = tcx.adt_def(def_id);
1214                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1215                     tcx.mk_adt(def, substs)
1216                 }
1217                 ItemKind::Existential(hir::ExistTy {
1218                     impl_trait_fn: None,
1219                     ..
1220                 }) => find_existential_constraints(tcx, def_id),
1221                 // existential types desugared from impl Trait
1222                 ItemKind::Existential(hir::ExistTy {
1223                     impl_trait_fn: Some(owner),
1224                     ..
1225                 }) => {
1226                     tcx.typeck_tables_of(owner)
1227                         .concrete_existential_types
1228                         .get(&def_id)
1229                         .map(|opaque| opaque.concrete_type)
1230                         .unwrap_or_else(|| {
1231                             // This can occur if some error in the
1232                             // owner fn prevented us from populating
1233                             // the `concrete_existential_types` table.
1234                             tcx.sess.delay_span_bug(
1235                                 DUMMY_SP,
1236                                 &format!(
1237                                     "owner {:?} has no existential type for {:?} in its tables",
1238                                     owner, def_id,
1239                                 ),
1240                             );
1241                             tcx.types.err
1242                         })
1243                 }
1244                 ItemKind::Trait(..)
1245                 | ItemKind::TraitAlias(..)
1246                 | ItemKind::Mod(..)
1247                 | ItemKind::ForeignMod(..)
1248                 | ItemKind::GlobalAsm(..)
1249                 | ItemKind::ExternCrate(..)
1250                 | ItemKind::Use(..) => {
1251                     if !fail {
1252                         return None;
1253                     }
1254                     span_bug!(
1255                         item.span,
1256                         "compute_type_of_item: unexpected item type: {:?}",
1257                         item.node
1258                     );
1259                 }
1260             }
1261         }
1262
1263         Node::ForeignItem(foreign_item) => match foreign_item.node {
1264             ForeignItemKind::Fn(..) => {
1265                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1266                 tcx.mk_fn_def(def_id, substs)
1267             }
1268             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1269             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1270         },
1271
1272         Node::Ctor(&ref def) | Node::Variant(&Spanned {
1273             node: hir::VariantKind { data: ref def, .. },
1274             ..
1275         }) => match *def {
1276             VariantData::Unit(..) | VariantData::Struct(..) => {
1277                 tcx.type_of(tcx.hir().get_parent_did_by_hir_id(hir_id))
1278             }
1279             VariantData::Tuple(..) => {
1280                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1281                 tcx.mk_fn_def(def_id, substs)
1282             }
1283         },
1284
1285         Node::Field(field) => icx.to_ty(&field.ty),
1286
1287         Node::Expr(&hir::Expr {
1288             node: hir::ExprKind::Closure(.., gen),
1289             ..
1290         }) => {
1291             if gen.is_some() {
1292                 return Some(tcx.typeck_tables_of(def_id).node_type(hir_id));
1293             }
1294
1295             let substs = ty::ClosureSubsts {
1296                 substs: InternalSubsts::identity_for_item(tcx, def_id),
1297             };
1298
1299             tcx.mk_closure(def_id, substs)
1300         }
1301
1302         Node::AnonConst(_) => {
1303             let parent_node = tcx.hir().get_by_hir_id(tcx.hir().get_parent_node_by_hir_id(hir_id));
1304             match parent_node {
1305                 Node::Ty(&hir::Ty {
1306                     node: hir::TyKind::Array(_, ref constant),
1307                     ..
1308                 })
1309                 | Node::Ty(&hir::Ty {
1310                     node: hir::TyKind::Typeof(ref constant),
1311                     ..
1312                 })
1313                 | Node::Expr(&hir::Expr {
1314                     node: ExprKind::Repeat(_, ref constant),
1315                     ..
1316                 }) if constant.hir_id == hir_id =>
1317                 {
1318                     tcx.types.usize
1319                 }
1320
1321                 Node::Variant(&Spanned {
1322                     node:
1323                         VariantKind {
1324                             disr_expr: Some(ref e),
1325                             ..
1326                         },
1327                     ..
1328                 }) if e.hir_id == hir_id =>
1329                 {
1330                     tcx.adt_def(tcx.hir().get_parent_did_by_hir_id(hir_id))
1331                         .repr
1332                         .discr_type()
1333                         .to_ty(tcx)
1334                 }
1335
1336                 Node::Ty(&hir::Ty { node: hir::TyKind::Path(_), .. }) |
1337                 Node::Expr(&hir::Expr { node: ExprKind::Struct(..), .. }) |
1338                 Node::Expr(&hir::Expr { node: ExprKind::Path(_), .. }) => {
1339                     let path = match parent_node {
1340                         Node::Ty(&hir::Ty { node: hir::TyKind::Path(ref path), .. }) |
1341                         Node::Expr(&hir::Expr { node: ExprKind::Path(ref path), .. }) => {
1342                             path
1343                         }
1344                         Node::Expr(&hir::Expr { node: ExprKind::Struct(ref path, ..), .. }) => {
1345                             &*path
1346                         }
1347                         _ => unreachable!(),
1348                     };
1349
1350                     match path {
1351                         QPath::Resolved(_, ref path) => {
1352                             let mut arg_index = 0;
1353                             let mut found_const = false;
1354                             for seg in &path.segments {
1355                                 if let Some(generic_args) = &seg.args {
1356                                     let args = &generic_args.args;
1357                                     for arg in args {
1358                                         if let GenericArg::Const(ct) = arg {
1359                                             if ct.value.hir_id == hir_id {
1360                                                 found_const = true;
1361                                                 break;
1362                                             }
1363                                             arg_index += 1;
1364                                         }
1365                                     }
1366                                 }
1367                             }
1368                             // Sanity check to make sure everything is as expected.
1369                             if !found_const {
1370                                 if !fail {
1371                                     return None;
1372                                 }
1373                                 bug!("no arg matching AnonConst in path")
1374                             }
1375                             match path.res {
1376                                 // We've encountered an `AnonConst` in some path, so we need to
1377                                 // figure out which generic parameter it corresponds to and return
1378                                 // the relevant type.
1379                                 Res::Def(DefKind::Struct, def_id)
1380                                 | Res::Def(DefKind::Union, def_id)
1381                                 | Res::Def(DefKind::Enum, def_id)
1382                                 | Res::Def(DefKind::Fn, def_id) => {
1383                                     let generics = tcx.generics_of(def_id);
1384                                     let mut param_index = 0;
1385                                     for param in &generics.params {
1386                                         if let ty::GenericParamDefKind::Const = param.kind {
1387                                             if param_index == arg_index {
1388                                                 return Some(tcx.type_of(param.def_id));
1389                                             }
1390                                             param_index += 1;
1391                                         }
1392                                     }
1393                                     // This is no generic parameter associated with the arg. This is
1394                                     // probably from an extra arg where one is not needed.
1395                                     return Some(tcx.types.err);
1396                                 }
1397                                 Res::Err => tcx.types.err,
1398                                 x => {
1399                                     if !fail {
1400                                         return None;
1401                                     }
1402                                     tcx.sess.delay_span_bug(
1403                                         DUMMY_SP,
1404                                         &format!(
1405                                             "unexpected const parent path def {:?}", x
1406                                         ),
1407                                     );
1408                                     tcx.types.err
1409                                 }
1410                             }
1411                         }
1412                         x => {
1413                             if !fail {
1414                                 return None;
1415                             }
1416                             tcx.sess.delay_span_bug(
1417                                 DUMMY_SP,
1418                                 &format!(
1419                                     "unexpected const parent path {:?}", x
1420                                 ),
1421                             );
1422                             tcx.types.err
1423                         }
1424                     }
1425                 }
1426
1427                 x => {
1428                     if !fail {
1429                         return None;
1430                     }
1431                     tcx.sess.delay_span_bug(
1432                         DUMMY_SP,
1433                         &format!(
1434                             "unexpected const parent in type_of_def_id(): {:?}", x
1435                         ),
1436                     );
1437                     tcx.types.err
1438                 }
1439             }
1440         }
1441
1442         Node::GenericParam(param) => match &param.kind {
1443             hir::GenericParamKind::Type { default: Some(ref ty), .. } |
1444             hir::GenericParamKind::Const { ref ty, .. } => {
1445                 icx.to_ty(ty)
1446             }
1447             x => {
1448                 if !fail {
1449                     return None;
1450                 }
1451                 bug!("unexpected non-type Node::GenericParam: {:?}", x)
1452             },
1453         },
1454
1455         x => {
1456             if !fail {
1457                 return None;
1458             }
1459             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1460         }
1461     })
1462 }
1463
1464 fn find_existential_constraints<'a, 'tcx>(
1465     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1466     def_id: DefId,
1467 ) -> Ty<'tcx> {
1468     use rustc::hir::{ImplItem, Item, TraitItem};
1469
1470     struct ConstraintLocator<'a, 'tcx: 'a> {
1471         tcx: TyCtxt<'a, 'tcx, 'tcx>,
1472         def_id: DefId,
1473         // First found type span, actual type, mapping from the existential type's generic
1474         // parameters to the concrete type's generic parameters
1475         //
1476         // The mapping is an index for each use site of a generic parameter in the concrete type
1477         //
1478         // The indices index into the generic parameters on the existential type.
1479         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1480     }
1481
1482     impl<'a, 'tcx> ConstraintLocator<'a, 'tcx> {
1483         fn check(&mut self, def_id: DefId) {
1484             trace!("checking {:?}", def_id);
1485             // don't try to check items that cannot possibly constrain the type
1486             if !self.tcx.has_typeck_tables(def_id) {
1487                 trace!("no typeck tables for {:?}", def_id);
1488                 return;
1489             }
1490             let ty = self
1491                 .tcx
1492                 .typeck_tables_of(def_id)
1493                 .concrete_existential_types
1494                 .get(&self.def_id);
1495             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1496                 // FIXME(oli-obk): trace the actual span from inference to improve errors
1497                 let span = self.tcx.def_span(def_id);
1498                 // used to quickly look up the position of a generic parameter
1499                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1500                 // skip binder is ok, since we only use this to find generic parameters and their
1501                 // positions.
1502                 for (idx, subst) in substs.iter().enumerate() {
1503                     if let UnpackedKind::Type(ty) = subst.unpack() {
1504                         if let ty::Param(p) = ty.sty {
1505                             if index_map.insert(p, idx).is_some() {
1506                                 // there was already an entry for `p`, meaning a generic parameter
1507                                 // was used twice
1508                                 self.tcx.sess.span_err(
1509                                     span,
1510                                     &format!("defining existential type use restricts existential \
1511                                     type by using the generic parameter `{}` twice", p.name),
1512                                 );
1513                                 return;
1514                             }
1515                         } else {
1516                             self.tcx.sess.delay_span_bug(
1517                                 span,
1518                                 &format!(
1519                                     "non-defining exist ty use in defining scope: {:?}, {:?}",
1520                                     concrete_type, substs,
1521                                 ),
1522                             );
1523                         }
1524                     }
1525                 }
1526                 // compute the index within the existential type for each generic parameter used in
1527                 // the concrete type
1528                 let indices = concrete_type
1529                     .subst(self.tcx, substs)
1530                     .walk()
1531                     .filter_map(|t| match &t.sty {
1532                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1533                         _ => None,
1534                     }).collect();
1535                 let is_param = |ty: Ty<'_>| match ty.sty {
1536                     ty::Param(_) => true,
1537                     _ => false,
1538                 };
1539                 if !substs.types().all(is_param) {
1540                     self.tcx.sess.span_err(
1541                         span,
1542                         "defining existential type use does not fully define existential type",
1543                     );
1544                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1545                     let mut ty = concrete_type.walk().fuse();
1546                     let mut p_ty = prev_ty.walk().fuse();
1547                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.sty, &p.sty) {
1548                         // type parameters are equal to any other type parameter for the purpose of
1549                         // concrete type equality, as it is possible to obtain the same type just
1550                         // by passing matching parameters to a function.
1551                         (ty::Param(_), ty::Param(_)) => true,
1552                         _ => t == p,
1553                     });
1554                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1555                         // found different concrete types for the existential type
1556                         let mut err = self.tcx.sess.struct_span_err(
1557                             span,
1558                             "concrete type differs from previous defining existential type use",
1559                         );
1560                         err.span_label(
1561                             span,
1562                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1563                         );
1564                         err.span_note(prev_span, "previous use here");
1565                         err.emit();
1566                     } else if indices != *prev_indices {
1567                         // found "same" concrete types, but the generic parameter order differs
1568                         let mut err = self.tcx.sess.struct_span_err(
1569                             span,
1570                             "concrete type's generic parameters differ from previous defining use",
1571                         );
1572                         use std::fmt::Write;
1573                         let mut s = String::new();
1574                         write!(s, "expected [").unwrap();
1575                         let list = |s: &mut String, indices: &Vec<usize>| {
1576                             let mut indices = indices.iter().cloned();
1577                             if let Some(first) = indices.next() {
1578                                 write!(s, "`{}`", substs[first]).unwrap();
1579                                 for i in indices {
1580                                     write!(s, ", `{}`", substs[i]).unwrap();
1581                                 }
1582                             }
1583                         };
1584                         list(&mut s, prev_indices);
1585                         write!(s, "], got [").unwrap();
1586                         list(&mut s, &indices);
1587                         write!(s, "]").unwrap();
1588                         err.span_label(span, s);
1589                         err.span_note(prev_span, "previous use here");
1590                         err.emit();
1591                     }
1592                 } else {
1593                     self.found = Some((span, concrete_type, indices));
1594                 }
1595             }
1596         }
1597     }
1598
1599     impl<'a, 'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'a, 'tcx> {
1600         fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1601             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1602         }
1603         fn visit_item(&mut self, it: &'tcx Item) {
1604             let def_id = self.tcx.hir().local_def_id_from_hir_id(it.hir_id);
1605             // the existential type itself or its children are not within its reveal scope
1606             if def_id != self.def_id {
1607                 self.check(def_id);
1608                 intravisit::walk_item(self, it);
1609             }
1610         }
1611         fn visit_impl_item(&mut self, it: &'tcx ImplItem) {
1612             let def_id = self.tcx.hir().local_def_id_from_hir_id(it.hir_id);
1613             // the existential type itself or its children are not within its reveal scope
1614             if def_id != self.def_id {
1615                 self.check(def_id);
1616                 intravisit::walk_impl_item(self, it);
1617             }
1618         }
1619         fn visit_trait_item(&mut self, it: &'tcx TraitItem) {
1620             let def_id = self.tcx.hir().local_def_id_from_hir_id(it.hir_id);
1621             self.check(def_id);
1622             intravisit::walk_trait_item(self, it);
1623         }
1624     }
1625
1626     let mut locator = ConstraintLocator {
1627         def_id,
1628         tcx,
1629         found: None,
1630     };
1631     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1632     let parent = tcx.hir().get_parent_item(hir_id);
1633
1634     trace!("parent_id: {:?}", parent);
1635
1636     if parent == hir::CRATE_HIR_ID {
1637         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1638     } else {
1639         trace!("parent: {:?}", tcx.hir().get_by_hir_id(parent));
1640         match tcx.hir().get_by_hir_id(parent) {
1641             Node::Item(ref it) => intravisit::walk_item(&mut locator, it),
1642             Node::ImplItem(ref it) => intravisit::walk_impl_item(&mut locator, it),
1643             Node::TraitItem(ref it) => intravisit::walk_trait_item(&mut locator, it),
1644             other => bug!(
1645                 "{:?} is not a valid parent of an existential type item",
1646                 other
1647             ),
1648         }
1649     }
1650
1651     match locator.found {
1652         Some((_, ty, _)) => ty,
1653         None => {
1654             let span = tcx.def_span(def_id);
1655             tcx.sess.span_err(span, "could not find defining uses");
1656             tcx.types.err
1657         }
1658     }
1659 }
1660
1661 fn fn_sig<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> ty::PolyFnSig<'tcx> {
1662     use rustc::hir::*;
1663     use rustc::hir::Node::*;
1664
1665     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1666
1667     let icx = ItemCtxt::new(tcx, def_id);
1668
1669     match tcx.hir().get_by_hir_id(hir_id) {
1670         TraitItem(hir::TraitItem {
1671             node: TraitItemKind::Method(sig, _),
1672             ..
1673         })
1674         | ImplItem(hir::ImplItem {
1675             node: ImplItemKind::Method(sig, _),
1676             ..
1677         }) => AstConv::ty_of_fn(&icx, sig.header.unsafety, sig.header.abi, &sig.decl),
1678
1679         Item(hir::Item {
1680             node: ItemKind::Fn(decl, header, _, _),
1681             ..
1682         }) => AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl),
1683
1684         ForeignItem(&hir::ForeignItem {
1685             node: ForeignItemKind::Fn(ref fn_decl, _, _),
1686             ..
1687         }) => {
1688             let abi = tcx.hir().get_foreign_abi_by_hir_id(hir_id);
1689             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1690         }
1691
1692         Ctor(data) | Variant(Spanned {
1693             node: hir::VariantKind { data, ..  },
1694             ..
1695         }) if data.ctor_hir_id().is_some() => {
1696             let ty = tcx.type_of(tcx.hir().get_parent_did_by_hir_id(hir_id));
1697             let inputs = data.fields()
1698                 .iter()
1699                 .map(|f| tcx.type_of(tcx.hir().local_def_id_from_hir_id(f.hir_id)));
1700             ty::Binder::bind(tcx.mk_fn_sig(
1701                 inputs,
1702                 ty,
1703                 false,
1704                 hir::Unsafety::Normal,
1705                 abi::Abi::Rust,
1706             ))
1707         }
1708
1709         Expr(&hir::Expr {
1710             node: hir::ExprKind::Closure(..),
1711             ..
1712         }) => {
1713             // Closure signatures are not like other function
1714             // signatures and cannot be accessed through `fn_sig`. For
1715             // example, a closure signature excludes the `self`
1716             // argument. In any case they are embedded within the
1717             // closure type as part of the `ClosureSubsts`.
1718             //
1719             // To get
1720             // the signature of a closure, you should use the
1721             // `closure_sig` method on the `ClosureSubsts`:
1722             //
1723             //    closure_substs.closure_sig(def_id, tcx)
1724             //
1725             // or, inside of an inference context, you can use
1726             //
1727             //    infcx.closure_sig(def_id, closure_substs)
1728             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1729         }
1730
1731         x => {
1732             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1733         }
1734     }
1735 }
1736
1737 fn impl_trait_ref<'a, 'tcx>(
1738     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1739     def_id: DefId,
1740 ) -> Option<ty::TraitRef<'tcx>> {
1741     let icx = ItemCtxt::new(tcx, def_id);
1742
1743     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1744     match tcx.hir().expect_item_by_hir_id(hir_id).node {
1745         hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1746             opt_trait_ref.as_ref().map(|ast_trait_ref| {
1747                 let selfty = tcx.type_of(def_id);
1748                 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1749             })
1750         }
1751         _ => bug!(),
1752     }
1753 }
1754
1755 fn impl_polarity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> hir::ImplPolarity {
1756     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1757     match tcx.hir().expect_item_by_hir_id(hir_id).node {
1758         hir::ItemKind::Impl(_, polarity, ..) => polarity,
1759         ref item => bug!("impl_polarity: {:?} not an impl", item),
1760     }
1761 }
1762
1763 // Is it marked with ?Sized
1764 fn is_unsized<'gcx: 'tcx, 'tcx>(
1765     astconv: &dyn AstConv<'gcx, 'tcx>,
1766     ast_bounds: &[hir::GenericBound],
1767     span: Span,
1768 ) -> bool {
1769     let tcx = astconv.tcx();
1770
1771     // Try to find an unbound in bounds.
1772     let mut unbound = None;
1773     for ab in ast_bounds {
1774         if let &hir::GenericBound::Trait(ref ptr, hir::TraitBoundModifier::Maybe) = ab {
1775             if unbound.is_none() {
1776                 unbound = Some(ptr.trait_ref.clone());
1777             } else {
1778                 span_err!(
1779                     tcx.sess,
1780                     span,
1781                     E0203,
1782                     "type parameter has more than one relaxed default \
1783                      bound, only one is supported"
1784                 );
1785             }
1786         }
1787     }
1788
1789     let kind_id = tcx.lang_items().require(SizedTraitLangItem);
1790     match unbound {
1791         Some(ref tpb) => {
1792             // FIXME(#8559) currently requires the unbound to be built-in.
1793             if let Ok(kind_id) = kind_id {
1794                 if tpb.path.res != Res::Def(DefKind::Trait, kind_id) {
1795                     tcx.sess.span_warn(
1796                         span,
1797                         "default bound relaxed for a type parameter, but \
1798                          this does nothing because the given bound is not \
1799                          a default. Only `?Sized` is supported",
1800                     );
1801                 }
1802             }
1803         }
1804         _ if kind_id.is_ok() => {
1805             return false;
1806         }
1807         // No lang item for Sized, so we can't add it as a bound.
1808         None => {}
1809     }
1810
1811     true
1812 }
1813
1814 /// Returns the early-bound lifetimes declared in this generics
1815 /// listing. For anything other than fns/methods, this is just all
1816 /// the lifetimes that are declared. For fns or methods, we have to
1817 /// screen out those that do not appear in any where-clauses etc using
1818 /// `resolve_lifetime::early_bound_lifetimes`.
1819 fn early_bound_lifetimes_from_generics<'a, 'tcx>(
1820     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1821     generics: &'a hir::Generics,
1822 ) -> impl Iterator<Item = &'a hir::GenericParam> + Captures<'tcx> {
1823     generics
1824         .params
1825         .iter()
1826         .filter(move |param| match param.kind {
1827             GenericParamKind::Lifetime { .. } => {
1828                 !tcx.is_late_bound(param.hir_id)
1829             }
1830             _ => false,
1831         })
1832 }
1833
1834 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1835 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1836 /// inferred constraints concerning which regions outlive other regions.
1837 fn predicates_defined_on<'a, 'tcx>(
1838     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1839     def_id: DefId,
1840 ) -> &'tcx ty::GenericPredicates<'tcx> {
1841     debug!("predicates_defined_on({:?})", def_id);
1842     let mut result = tcx.explicit_predicates_of(def_id);
1843     debug!(
1844         "predicates_defined_on: explicit_predicates_of({:?}) = {:?}",
1845         def_id,
1846         result,
1847     );
1848     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1849     if !inferred_outlives.is_empty() {
1850         let span = tcx.def_span(def_id);
1851         debug!(
1852             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1853             def_id,
1854             inferred_outlives,
1855         );
1856         let mut predicates = (*result).clone();
1857         predicates.predicates.extend(inferred_outlives.iter().map(|&p| (p, span)));
1858         result = tcx.arena.alloc(predicates);
1859     }
1860     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1861     result
1862 }
1863
1864 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1865 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1866 /// `Self: Trait` predicates for traits.
1867 fn predicates_of<'a, 'tcx>(
1868     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1869     def_id: DefId,
1870 ) -> &'tcx ty::GenericPredicates<'tcx> {
1871     let mut result = tcx.predicates_defined_on(def_id);
1872
1873     if tcx.is_trait(def_id) {
1874         // For traits, add `Self: Trait` predicate. This is
1875         // not part of the predicates that a user writes, but it
1876         // is something that one must prove in order to invoke a
1877         // method or project an associated type.
1878         //
1879         // In the chalk setup, this predicate is not part of the
1880         // "predicates" for a trait item. But it is useful in
1881         // rustc because if you directly (e.g.) invoke a trait
1882         // method like `Trait::method(...)`, you must naturally
1883         // prove that the trait applies to the types that were
1884         // used, and adding the predicate into this list ensures
1885         // that this is done.
1886         let span = tcx.def_span(def_id);
1887         let mut predicates = (*result).clone();
1888         predicates.predicates.push((ty::TraitRef::identity(tcx, def_id).to_predicate(), span));
1889         result = tcx.arena.alloc(predicates);
1890     }
1891     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1892     result
1893 }
1894
1895 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1896 /// N.B., this does not include any implied/inferred constraints.
1897 fn explicit_predicates_of<'a, 'tcx>(
1898     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1899     def_id: DefId,
1900 ) -> &'tcx ty::GenericPredicates<'tcx> {
1901     use rustc::hir::*;
1902     use rustc_data_structures::fx::FxHashSet;
1903
1904     debug!("explicit_predicates_of(def_id={:?})", def_id);
1905
1906     /// A data structure with unique elements, which preserves order of insertion.
1907     /// Preserving the order of insertion is important here so as not to break
1908     /// compile-fail UI tests.
1909     struct UniquePredicates<'tcx> {
1910         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
1911         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
1912     }
1913
1914     impl<'tcx> UniquePredicates<'tcx> {
1915         fn new() -> Self {
1916             UniquePredicates {
1917                 predicates: vec![],
1918                 uniques: FxHashSet::default(),
1919             }
1920         }
1921
1922         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
1923             if self.uniques.insert(value) {
1924                 self.predicates.push(value);
1925             }
1926         }
1927
1928         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
1929             for value in iter {
1930                 self.push(value);
1931             }
1932         }
1933     }
1934
1935     let hir_id = match tcx.hir().as_local_hir_id(def_id) {
1936         Some(hir_id) => hir_id,
1937         None => return tcx.predicates_of(def_id),
1938     };
1939     let node = tcx.hir().get_by_hir_id(hir_id);
1940
1941     let mut is_trait = None;
1942     let mut is_default_impl_trait = None;
1943
1944     let icx = ItemCtxt::new(tcx, def_id);
1945     let no_generics = hir::Generics::empty();
1946     let empty_trait_items = HirVec::new();
1947
1948     let mut predicates = UniquePredicates::new();
1949
1950     let ast_generics = match node {
1951         Node::TraitItem(item) => &item.generics,
1952
1953         Node::ImplItem(item) => match item.node {
1954             ImplItemKind::Existential(ref bounds) => {
1955                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1956                 let opaque_ty = tcx.mk_opaque(def_id, substs);
1957
1958                 // Collect the bounds, i.e., the `A+B+'c` in `impl A+B+'c`.
1959                 let bounds = compute_bounds(
1960                     &icx,
1961                     opaque_ty,
1962                     bounds,
1963                     SizedByDefault::Yes,
1964                     tcx.def_span(def_id),
1965                 );
1966
1967                 predicates.extend(bounds.predicates(tcx, opaque_ty));
1968                 &item.generics
1969             }
1970             _ => &item.generics,
1971         },
1972
1973         Node::Item(item) => {
1974             match item.node {
1975                 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
1976                     if defaultness.is_default() {
1977                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
1978                     }
1979                     generics
1980                 }
1981                 ItemKind::Fn(.., ref generics, _)
1982                 | ItemKind::Ty(_, ref generics)
1983                 | ItemKind::Enum(_, ref generics)
1984                 | ItemKind::Struct(_, ref generics)
1985                 | ItemKind::Union(_, ref generics) => generics,
1986
1987                 ItemKind::Trait(_, _, ref generics, .., ref items) => {
1988                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
1989                     generics
1990                 }
1991                 ItemKind::TraitAlias(ref generics, _) => {
1992                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &empty_trait_items));
1993                     generics
1994                 }
1995                 ItemKind::Existential(ExistTy {
1996                     ref bounds,
1997                     impl_trait_fn,
1998                     ref generics,
1999                     origin: _,
2000                 }) => {
2001                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2002                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2003
2004                     // Collect the bounds, i.e., the `A+B+'c` in `impl A+B+'c`.
2005                     let bounds = compute_bounds(
2006                         &icx,
2007                         opaque_ty,
2008                         bounds,
2009                         SizedByDefault::Yes,
2010                         tcx.def_span(def_id),
2011                     );
2012
2013                     if impl_trait_fn.is_some() {
2014                         // impl Trait
2015                         return tcx.arena.alloc(ty::GenericPredicates {
2016                             parent: None,
2017                             predicates: bounds.predicates(tcx, opaque_ty),
2018                         });
2019                     } else {
2020                         // named existential types
2021                         predicates.extend(bounds.predicates(tcx, opaque_ty));
2022                         generics
2023                     }
2024                 }
2025
2026                 _ => &no_generics,
2027             }
2028         }
2029
2030         Node::ForeignItem(item) => match item.node {
2031             ForeignItemKind::Static(..) => &no_generics,
2032             ForeignItemKind::Fn(_, _, ref generics) => generics,
2033             ForeignItemKind::Type => &no_generics,
2034         },
2035
2036         _ => &no_generics,
2037     };
2038
2039     let generics = tcx.generics_of(def_id);
2040     let parent_count = generics.parent_count as u32;
2041     let has_own_self = generics.has_self && parent_count == 0;
2042
2043     // Below we'll consider the bounds on the type parameters (including `Self`)
2044     // and the explicit where-clauses, but to get the full set of predicates
2045     // on a trait we need to add in the supertrait bounds and bounds found on
2046     // associated types.
2047     if let Some((_trait_ref, _)) = is_trait {
2048         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2049     }
2050
2051     // In default impls, we can assume that the self type implements
2052     // the trait. So in:
2053     //
2054     //     default impl Foo for Bar { .. }
2055     //
2056     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2057     // (see below). Recall that a default impl is not itself an impl, but rather a
2058     // set of defaults that can be incorporated into another impl.
2059     if let Some(trait_ref) = is_default_impl_trait {
2060         predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2061     }
2062
2063     // Collect the region predicates that were declared inline as
2064     // well. In the case of parameters declared on a fn or method, we
2065     // have to be careful to only iterate over early-bound regions.
2066     let mut index = parent_count + has_own_self as u32;
2067     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2068         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2069             def_id: tcx.hir().local_def_id_from_hir_id(param.hir_id),
2070             index,
2071             name: param.name.ident().as_interned_str(),
2072         }));
2073         index += 1;
2074
2075         match param.kind {
2076             GenericParamKind::Lifetime { .. } => {
2077                 param.bounds.iter().for_each(|bound| match bound {
2078                     hir::GenericBound::Outlives(lt) => {
2079                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2080                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2081                         predicates.push((outlives.to_predicate(), lt.span));
2082                     }
2083                     _ => bug!(),
2084                 });
2085             }
2086             _ => bug!(),
2087         }
2088     }
2089
2090     // Collect the predicates that were written inline by the user on each
2091     // type parameter (e.g., `<T:Foo>`).
2092     for param in &ast_generics.params {
2093         if let GenericParamKind::Type { .. } = param.kind {
2094             let name = param.name.ident().as_interned_str();
2095             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2096             index += 1;
2097
2098             let sized = SizedByDefault::Yes;
2099             let bounds = compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2100             predicates.extend(bounds.predicates(tcx, param_ty));
2101         }
2102     }
2103
2104     // Add in the bounds that appear in the where-clause
2105     let where_clause = &ast_generics.where_clause;
2106     for predicate in &where_clause.predicates {
2107         match predicate {
2108             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2109                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2110
2111                 // Keep the type around in a dummy predicate, in case of no bounds.
2112                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2113                 // is still checked for WF.
2114                 if bound_pred.bounds.is_empty() {
2115                     if let ty::Param(_) = ty.sty {
2116                         // This is a `where T:`, which can be in the HIR from the
2117                         // transformation that moves `?Sized` to `T`'s declaration.
2118                         // We can skip the predicate because type parameters are
2119                         // trivially WF, but also we *should*, to avoid exposing
2120                         // users who never wrote `where Type:,` themselves, to
2121                         // compiler/tooling bugs from not handling WF predicates.
2122                     } else {
2123                         let span = bound_pred.bounded_ty.span;
2124                         let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2125                         predicates.push(
2126                             (ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)), span)
2127                         );
2128                     }
2129                 }
2130
2131                 for bound in bound_pred.bounds.iter() {
2132                     match bound {
2133                         &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2134                             let mut projections = Vec::new();
2135
2136                             let (trait_ref, _) = AstConv::instantiate_poly_trait_ref(
2137                                 &icx,
2138                                 poly_trait_ref,
2139                                 ty,
2140                                 &mut projections,
2141                             );
2142
2143                             predicates.extend(
2144                                 iter::once((trait_ref.to_predicate(), poly_trait_ref.span)).chain(
2145                                     projections.iter().map(|&(p, span)| (p.to_predicate(), span)
2146                             )));
2147                         }
2148
2149                         &hir::GenericBound::Outlives(ref lifetime) => {
2150                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2151                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2152                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2153                         }
2154                     }
2155                 }
2156             }
2157
2158             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2159                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2160                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2161                     let (r2, span) = match bound {
2162                         hir::GenericBound::Outlives(lt) => {
2163                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2164                         }
2165                         _ => bug!(),
2166                     };
2167                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2168
2169                     (ty::Predicate::RegionOutlives(pred), span)
2170                 }))
2171             }
2172
2173             &hir::WherePredicate::EqPredicate(..) => {
2174                 // FIXME(#20041)
2175             }
2176         }
2177     }
2178
2179     // Add predicates from associated type bounds.
2180     if let Some((self_trait_ref, trait_items)) = is_trait {
2181         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2182             let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2183             let bounds = match trait_item.node {
2184                 hir::TraitItemKind::Type(ref bounds, _) => bounds,
2185                 _ => return vec![].into_iter()
2186             };
2187
2188             let assoc_ty =
2189                 tcx.mk_projection(tcx.hir().local_def_id_from_hir_id(trait_item.hir_id),
2190                     self_trait_ref.substs);
2191
2192             let bounds = compute_bounds(
2193                 &ItemCtxt::new(tcx, def_id),
2194                 assoc_ty,
2195                 bounds,
2196                 SizedByDefault::Yes,
2197                 trait_item.span,
2198             );
2199
2200             bounds.predicates(tcx, assoc_ty).into_iter()
2201         }))
2202     }
2203
2204     let mut predicates = predicates.predicates;
2205
2206     // Subtle: before we store the predicates into the tcx, we
2207     // sort them so that predicates like `T: Foo<Item=U>` come
2208     // before uses of `U`.  This avoids false ambiguity errors
2209     // in trait checking. See `setup_constraining_predicates`
2210     // for details.
2211     if let Node::Item(&Item {
2212         node: ItemKind::Impl(..),
2213         ..
2214     }) = node
2215     {
2216         let self_ty = tcx.type_of(def_id);
2217         let trait_ref = tcx.impl_trait_ref(def_id);
2218         cgp::setup_constraining_predicates(
2219             tcx,
2220             &mut predicates,
2221             trait_ref,
2222             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2223         );
2224     }
2225
2226     let result = tcx.arena.alloc(ty::GenericPredicates {
2227         parent: generics.parent,
2228         predicates,
2229     });
2230     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2231     result
2232 }
2233
2234 pub enum SizedByDefault {
2235     Yes,
2236     No,
2237 }
2238
2239 /// Translate the AST's notion of ty param bounds (which are an enum consisting of a newtyped `Ty`
2240 /// or a region) to ty's notion of ty param bounds, which can either be user-defined traits, or the
2241 /// built-in trait `Send`.
2242 pub fn compute_bounds<'gcx: 'tcx, 'tcx>(
2243     astconv: &dyn AstConv<'gcx, 'tcx>,
2244     param_ty: Ty<'tcx>,
2245     ast_bounds: &[hir::GenericBound],
2246     sized_by_default: SizedByDefault,
2247     span: Span,
2248 ) -> Bounds<'tcx> {
2249     let mut region_bounds = Vec::new();
2250     let mut trait_bounds = Vec::new();
2251
2252     for ast_bound in ast_bounds {
2253         match *ast_bound {
2254             hir::GenericBound::Trait(ref b, hir::TraitBoundModifier::None) => trait_bounds.push(b),
2255             hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {}
2256             hir::GenericBound::Outlives(ref l) => region_bounds.push(l),
2257         }
2258     }
2259
2260     let mut projection_bounds = Vec::new();
2261
2262     let mut trait_bounds: Vec<_> = trait_bounds.iter().map(|&bound| {
2263         let (poly_trait_ref, _) = astconv.instantiate_poly_trait_ref(
2264             bound,
2265             param_ty,
2266             &mut projection_bounds,
2267         );
2268         (poly_trait_ref, bound.span)
2269     }).collect();
2270
2271     let region_bounds = region_bounds
2272         .into_iter()
2273         .map(|r| (astconv.ast_region_to_region(r, None), r.span))
2274         .collect();
2275
2276     trait_bounds.sort_by_key(|(t, _)| t.def_id());
2277
2278     let implicitly_sized = if let SizedByDefault::Yes = sized_by_default {
2279         if !is_unsized(astconv, ast_bounds, span) {
2280             Some(span)
2281         } else {
2282             None
2283         }
2284     } else {
2285         None
2286     };
2287
2288     Bounds {
2289         region_bounds,
2290         implicitly_sized,
2291         trait_bounds,
2292         projection_bounds,
2293     }
2294 }
2295
2296 /// Converts a specific `GenericBound` from the AST into a set of
2297 /// predicates that apply to the self type. A vector is returned
2298 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2299 /// predicates) to one (`T: Foo`) to many (`T: Bar<X=i32>` adds `T: Bar`
2300 /// and `<T as Bar>::X == i32`).
2301 fn predicates_from_bound<'tcx>(
2302     astconv: &dyn AstConv<'tcx, 'tcx>,
2303     param_ty: Ty<'tcx>,
2304     bound: &hir::GenericBound,
2305 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2306     match *bound {
2307         hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2308             let mut projections = Vec::new();
2309             let (pred, _) = astconv.instantiate_poly_trait_ref(tr, param_ty, &mut projections);
2310             iter::once((pred.to_predicate(), tr.span)).chain(
2311                 projections
2312                     .into_iter()
2313                     .map(|(p, span)| (p.to_predicate(), span))
2314             ).collect()
2315         }
2316         hir::GenericBound::Outlives(ref lifetime) => {
2317             let region = astconv.ast_region_to_region(lifetime, None);
2318             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2319             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2320         }
2321         hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2322     }
2323 }
2324
2325 fn compute_sig_of_foreign_fn_decl<'a, 'tcx>(
2326     tcx: TyCtxt<'a, 'tcx, 'tcx>,
2327     def_id: DefId,
2328     decl: &hir::FnDecl,
2329     abi: abi::Abi,
2330 ) -> ty::PolyFnSig<'tcx> {
2331     let unsafety = if abi == abi::Abi::RustIntrinsic {
2332         intrisic_operation_unsafety(&*tcx.item_name(def_id).as_str())
2333     } else {
2334         hir::Unsafety::Unsafe
2335     };
2336     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl);
2337
2338     // feature gate SIMD types in FFI, since I (huonw) am not sure the
2339     // ABIs are handled at all correctly.
2340     if abi != abi::Abi::RustIntrinsic
2341         && abi != abi::Abi::PlatformIntrinsic
2342         && !tcx.features().simd_ffi
2343     {
2344         let check = |ast_ty: &hir::Ty, ty: Ty<'_>| {
2345             if ty.is_simd() {
2346                 tcx.sess
2347                    .struct_span_err(
2348                        ast_ty.span,
2349                        &format!(
2350                            "use of SIMD type `{}` in FFI is highly experimental and \
2351                             may result in invalid code",
2352                            tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2353                        ),
2354                    )
2355                    .help("add #![feature(simd_ffi)] to the crate attributes to enable")
2356                    .emit();
2357             }
2358         };
2359         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2360             check(&input, ty)
2361         }
2362         if let hir::Return(ref ty) = decl.output {
2363             check(&ty, *fty.output().skip_binder())
2364         }
2365     }
2366
2367     fty
2368 }
2369
2370 fn is_foreign_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> bool {
2371     match tcx.hir().get_if_local(def_id) {
2372         Some(Node::ForeignItem(..)) => true,
2373         Some(_) => false,
2374         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2375     }
2376 }
2377
2378 fn static_mutability<'a, 'tcx>(
2379     tcx: TyCtxt<'a, 'tcx, 'tcx>,
2380     def_id: DefId,
2381 ) -> Option<hir::Mutability> {
2382     match tcx.hir().get_if_local(def_id) {
2383         Some(Node::Item(&hir::Item {
2384             node: hir::ItemKind::Static(_, mutbl, _), ..
2385         })) |
2386         Some(Node::ForeignItem( &hir::ForeignItem {
2387             node: hir::ForeignItemKind::Static(_, mutbl), ..
2388         })) => Some(mutbl),
2389         Some(_) => None,
2390         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2391     }
2392 }
2393
2394 fn from_target_feature(
2395     tcx: TyCtxt<'_, '_, '_>,
2396     id: DefId,
2397     attr: &ast::Attribute,
2398     whitelist: &FxHashMap<String, Option<Symbol>>,
2399     target_features: &mut Vec<Symbol>,
2400 ) {
2401     let list = match attr.meta_item_list() {
2402         Some(list) => list,
2403         None => return,
2404     };
2405     let bad_item = |span| {
2406         let msg = "malformed `target_feature` attribute input";
2407         let code = "enable = \"..\"".to_owned();
2408         tcx.sess.struct_span_err(span, &msg)
2409             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2410             .emit();
2411     };
2412     let rust_features = tcx.features();
2413     for item in list {
2414         // Only `enable = ...` is accepted in the meta item list
2415         if !item.check_name(sym::enable) {
2416             bad_item(item.span());
2417             continue;
2418         }
2419
2420         // Must be of the form `enable = "..."` ( a string)
2421         let value = match item.value_str() {
2422             Some(value) => value,
2423             None => {
2424                 bad_item(item.span());
2425                 continue;
2426             }
2427         };
2428
2429         // We allow comma separation to enable multiple features
2430         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2431             // Only allow whitelisted features per platform
2432             let feature_gate = match whitelist.get(feature) {
2433                 Some(g) => g,
2434                 None => {
2435                     let msg = format!(
2436                         "the feature named `{}` is not valid for this target",
2437                         feature
2438                     );
2439                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2440                     err.span_label(
2441                         item.span(),
2442                         format!("`{}` is not valid for this target", feature),
2443                     );
2444                     if feature.starts_with("+") {
2445                         let valid = whitelist.contains_key(&feature[1..]);
2446                         if valid {
2447                             err.help("consider removing the leading `+` in the feature name");
2448                         }
2449                     }
2450                     err.emit();
2451                     return None;
2452                 }
2453             };
2454
2455             // Only allow features whose feature gates have been enabled
2456             let allowed = match feature_gate.as_ref().map(|s| *s) {
2457                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2458                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2459                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2460                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2461                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2462                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2463                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2464                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2465                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2466                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2467                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2468                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2469                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2470                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2471                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2472                 Some(name) => bug!("unknown target feature gate {}", name),
2473                 None => true,
2474             };
2475             if !allowed && id.is_local() {
2476                 feature_gate::emit_feature_err(
2477                     &tcx.sess.parse_sess,
2478                     feature_gate.unwrap(),
2479                     item.span(),
2480                     feature_gate::GateIssue::Language,
2481                     &format!("the target feature `{}` is currently unstable", feature),
2482                 );
2483             }
2484             Some(Symbol::intern(feature))
2485         }));
2486     }
2487 }
2488
2489 fn linkage_by_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId, name: &str) -> Linkage {
2490     use rustc::mir::mono::Linkage::*;
2491
2492     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2493     // applicable to variable declarations and may not really make sense for
2494     // Rust code in the first place but whitelist them anyway and trust that
2495     // the user knows what s/he's doing. Who knows, unanticipated use cases
2496     // may pop up in the future.
2497     //
2498     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2499     // and don't have to be, LLVM treats them as no-ops.
2500     match name {
2501         "appending" => Appending,
2502         "available_externally" => AvailableExternally,
2503         "common" => Common,
2504         "extern_weak" => ExternalWeak,
2505         "external" => External,
2506         "internal" => Internal,
2507         "linkonce" => LinkOnceAny,
2508         "linkonce_odr" => LinkOnceODR,
2509         "private" => Private,
2510         "weak" => WeakAny,
2511         "weak_odr" => WeakODR,
2512         _ => {
2513             let span = tcx.hir().span_if_local(def_id);
2514             if let Some(span) = span {
2515                 tcx.sess.span_fatal(span, "invalid linkage specified")
2516             } else {
2517                 tcx.sess
2518                    .fatal(&format!("invalid linkage specified: {}", name))
2519             }
2520         }
2521     }
2522 }
2523
2524 fn codegen_fn_attrs<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, id: DefId) -> CodegenFnAttrs {
2525     let attrs = tcx.get_attrs(id);
2526
2527     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2528
2529     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2530
2531     let mut inline_span = None;
2532     for attr in attrs.iter() {
2533         if attr.check_name(sym::cold) {
2534             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2535         } else if attr.check_name(sym::allocator) {
2536             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2537         } else if attr.check_name(sym::unwind) {
2538             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2539         } else if attr.check_name(sym::ffi_returns_twice) {
2540             if tcx.is_foreign_item(id) {
2541                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2542             } else {
2543                 // `#[ffi_returns_twice]` is only allowed `extern fn`s
2544                 struct_span_err!(
2545                     tcx.sess,
2546                     attr.span,
2547                     E0724,
2548                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2549                 ).emit();
2550             }
2551         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2552             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2553         } else if attr.check_name(sym::naked) {
2554             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2555         } else if attr.check_name(sym::no_mangle) {
2556             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2557         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2558             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2559         } else if attr.check_name(sym::no_debug) {
2560             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2561         } else if attr.check_name(sym::used) {
2562             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2563         } else if attr.check_name(sym::thread_local) {
2564             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2565         } else if attr.check_name(sym::export_name) {
2566             if let Some(s) = attr.value_str() {
2567                 if s.as_str().contains("\0") {
2568                     // `#[export_name = ...]` will be converted to a null-terminated string,
2569                     // so it may not contain any null characters.
2570                     struct_span_err!(
2571                         tcx.sess,
2572                         attr.span,
2573                         E0648,
2574                         "`export_name` may not contain null characters"
2575                     ).emit();
2576                 }
2577                 codegen_fn_attrs.export_name = Some(s);
2578             }
2579         } else if attr.check_name(sym::target_feature) {
2580             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2581                 let msg = "#[target_feature(..)] can only be applied to `unsafe` functions";
2582                 tcx.sess.struct_span_err(attr.span, msg)
2583                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2584                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2585                     .emit();
2586             }
2587             from_target_feature(
2588                 tcx,
2589                 id,
2590                 attr,
2591                 &whitelist,
2592                 &mut codegen_fn_attrs.target_features,
2593             );
2594         } else if attr.check_name(sym::linkage) {
2595             if let Some(val) = attr.value_str() {
2596                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2597             }
2598         } else if attr.check_name(sym::link_section) {
2599             if let Some(val) = attr.value_str() {
2600                 if val.as_str().bytes().any(|b| b == 0) {
2601                     let msg = format!(
2602                         "illegal null byte in link_section \
2603                          value: `{}`",
2604                         &val
2605                     );
2606                     tcx.sess.span_err(attr.span, &msg);
2607                 } else {
2608                     codegen_fn_attrs.link_section = Some(val);
2609                 }
2610             }
2611         } else if attr.check_name(sym::link_name) {
2612             codegen_fn_attrs.link_name = attr.value_str();
2613         }
2614     }
2615
2616     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2617         if attr.path != sym::inline {
2618             return ia;
2619         }
2620         match attr.meta().map(|i| i.node) {
2621             Some(MetaItemKind::Word) => {
2622                 mark_used(attr);
2623                 InlineAttr::Hint
2624             }
2625             Some(MetaItemKind::List(ref items)) => {
2626                 mark_used(attr);
2627                 inline_span = Some(attr.span);
2628                 if items.len() != 1 {
2629                     span_err!(
2630                         tcx.sess.diagnostic(),
2631                         attr.span,
2632                         E0534,
2633                         "expected one argument"
2634                     );
2635                     InlineAttr::None
2636                 } else if list_contains_name(&items[..], sym::always) {
2637                     InlineAttr::Always
2638                 } else if list_contains_name(&items[..], sym::never) {
2639                     InlineAttr::Never
2640                 } else {
2641                     span_err!(
2642                         tcx.sess.diagnostic(),
2643                         items[0].span(),
2644                         E0535,
2645                         "invalid argument"
2646                     );
2647
2648                     InlineAttr::None
2649                 }
2650             }
2651             Some(MetaItemKind::NameValue(_)) => ia,
2652             None => ia,
2653         }
2654     });
2655
2656     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2657         if attr.path != sym::optimize {
2658             return ia;
2659         }
2660         let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2661         match attr.meta().map(|i| i.node) {
2662             Some(MetaItemKind::Word) => {
2663                 err(attr.span, "expected one argument");
2664                 ia
2665             }
2666             Some(MetaItemKind::List(ref items)) => {
2667                 mark_used(attr);
2668                 inline_span = Some(attr.span);
2669                 if items.len() != 1 {
2670                     err(attr.span, "expected one argument");
2671                     OptimizeAttr::None
2672                 } else if list_contains_name(&items[..], sym::size) {
2673                     OptimizeAttr::Size
2674                 } else if list_contains_name(&items[..], sym::speed) {
2675                     OptimizeAttr::Speed
2676                 } else {
2677                     err(items[0].span(), "invalid argument");
2678                     OptimizeAttr::None
2679                 }
2680             }
2681             Some(MetaItemKind::NameValue(_)) => ia,
2682             None => ia,
2683         }
2684     });
2685
2686     // If a function uses #[target_feature] it can't be inlined into general
2687     // purpose functions as they wouldn't have the right target features
2688     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2689     // respected.
2690     if codegen_fn_attrs.target_features.len() > 0 {
2691         if codegen_fn_attrs.inline == InlineAttr::Always {
2692             if let Some(span) = inline_span {
2693                 tcx.sess.span_err(
2694                     span,
2695                     "cannot use #[inline(always)] with \
2696                      #[target_feature]",
2697                 );
2698             }
2699         }
2700     }
2701
2702     // Weak lang items have the same semantics as "std internal" symbols in the
2703     // sense that they're preserved through all our LTO passes and only
2704     // strippable by the linker.
2705     //
2706     // Additionally weak lang items have predetermined symbol names.
2707     if tcx.is_weak_lang_item(id) {
2708         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2709     }
2710     if let Some(name) = weak_lang_items::link_name(&attrs) {
2711         codegen_fn_attrs.export_name = Some(name);
2712         codegen_fn_attrs.link_name = Some(name);
2713     }
2714
2715     // Internal symbols to the standard library all have no_mangle semantics in
2716     // that they have defined symbol names present in the function name. This
2717     // also applies to weak symbols where they all have known symbol names.
2718     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2719         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2720     }
2721
2722     codegen_fn_attrs
2723 }