src/librustc_typeck/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::{AstConv, Bounds, SizedByDefault};
  18 use crate::constrained_generic_params as cgp;
  19 use crate::check::intrinsic::intrisic_operation_unsafety;
  20 use crate::lint;
  21 use crate::middle::resolve_lifetime as rl;
  22 use crate::middle::weak_lang_items;
  23 use rustc::mir::mono::Linkage;
  24 use rustc::ty::query::Providers;
  25 use rustc::ty::subst::{Subst, InternalSubsts};
  26 use rustc::ty::util::Discr;
  27 use rustc::ty::util::IntTypeExt;
  28 use rustc::ty::subst::UnpackedKind;
  29 use rustc::ty::{self, AdtKind, DefIdTree, ToPolyTraitRef, Ty, TyCtxt, Const};
  30 use rustc::ty::{ReprOptions, ToPredicate};
  31 use rustc::util::captures::Captures;
  32 use rustc::util::nodemap::FxHashMap;
  33 use rustc_target::spec::abi;
  34
  35 use syntax::ast;
  36 use syntax::ast::{Ident, MetaItemKind};
  37 use syntax::attr::{InlineAttr, OptimizeAttr, list_contains_name, mark_used};
  38 use syntax::source_map::Spanned;
  39 use syntax::feature_gate;
  40 use syntax::symbol::{InternedString, kw, Symbol, sym};
  41 use syntax_pos::{Span, DUMMY_SP};
  42
  43 use rustc::hir::def::{CtorKind, Res, DefKind};
  44 use rustc::hir::Node;
  45 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
  46 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  47 use rustc::hir::GenericParamKind;
  48 use rustc::hir::{self, CodegenFnAttrFlags, CodegenFnAttrs, Unsafety};
  49
  50 use errors::{Applicability, DiagnosticId};
  51
  52 use std::iter;
  53
  54 struct OnlySelfBounds(bool);
  55
  56 ///////////////////////////////////////////////////////////////////////////
  57 // Main entry point
  58
  59 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
  60     tcx.hir().visit_item_likes_in_module(
  61         module_def_id,
  62         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor()
  63     );
  64 }
  65
  66 pub fn provide(providers: &mut Providers<'_>) {
  67     *providers = Providers {
  68         type_of,
  69         generics_of,
  70         predicates_of,
  71         predicates_defined_on,
  72         explicit_predicates_of,
  73         super_predicates_of,
  74         type_param_predicates,
  75         trait_def,
  76         adt_def,
  77         fn_sig,
  78         impl_trait_ref,
  79         impl_polarity,
  80         is_foreign_item,
  81         static_mutability,
  82         codegen_fn_attrs,
  83         collect_mod_item_types,
  84         ..*providers
  85     };
  86 }
  87
  88 ///////////////////////////////////////////////////////////////////////////
  89
  90 /// Context specific to some particular item. This is what implements
  91 /// `AstConv`. It has information about the predicates that are defined
  92 /// on the trait. Unfortunately, this predicate information is
  93 /// available in various different forms at various points in the
  94 /// process. So we can't just store a pointer to e.g., the AST or the
  95 /// parsed ty form, we have to be more flexible. To this end, the
  96 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
  97 /// `get_type_parameter_bounds` requests, drawing the information from
  98 /// the AST (`hir::Generics`), recursively.
  99 pub struct ItemCtxt<'tcx> {
 100     tcx: TyCtxt<'tcx>,
 101     item_def_id: DefId,
 102 }
 103
 104 ///////////////////////////////////////////////////////////////////////////
 105
 106 struct CollectItemTypesVisitor<'tcx> {
 107     tcx: TyCtxt<'tcx>,
 108 }
 109
 110 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 111     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 112         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 113     }
 114
 115     fn visit_item(&mut self, item: &'tcx hir::Item) {
 116         convert_item(self.tcx, item.hir_id);
 117         intravisit::walk_item(self, item);
 118     }
 119
 120     fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
 121         for param in &generics.params {
 122             match param.kind {
 123                 hir::GenericParamKind::Lifetime { .. } => {}
 124                 hir::GenericParamKind::Type {
 125                     default: Some(_), ..
 126                 } => {
 127                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 128                     self.tcx.type_of(def_id);
 129                 }
 130                 hir::GenericParamKind::Type { .. } => {}
 131                 hir::GenericParamKind::Const { .. } => {
 132                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 133                     self.tcx.type_of(def_id);
 134                 }
 135             }
 136         }
 137         intravisit::walk_generics(self, generics);
 138     }
 139
 140     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 141         if let hir::ExprKind::Closure(..) = expr.node {
 142             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 143             self.tcx.generics_of(def_id);
 144             self.tcx.type_of(def_id);
 145         }
 146         intravisit::walk_expr(self, expr);
 147     }
 148
 149     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
 150         convert_trait_item(self.tcx, trait_item.hir_id);
 151         intravisit::walk_trait_item(self, trait_item);
 152     }
 153
 154     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
 155         convert_impl_item(self.tcx, impl_item.hir_id);
 156         intravisit::walk_impl_item(self, impl_item);
 157     }
 158 }
 159
 160 ///////////////////////////////////////////////////////////////////////////
 161 // Utility types and common code for the above passes.
 162
 163 fn bad_placeholder_type(tcx: TyCtxt<'tcx>, span: Span) -> errors::DiagnosticBuilder<'tcx> {
 164     let mut diag = tcx.sess.struct_span_err_with_code(
 165         span,
 166         "the type placeholder `_` is not allowed within types on item signatures",
 167         DiagnosticId::Error("E0121".into()),
 168     );
 169     diag.span_label(span, "not allowed in type signatures");
 170     diag
 171 }
 172
 173 impl ItemCtxt<'tcx> {
 174     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 175         ItemCtxt { tcx, item_def_id }
 176     }
 177
 178     pub fn to_ty(&self, ast_ty: &'tcx hir::Ty) -> Ty<'tcx> {
 179         AstConv::ast_ty_to_ty(self, ast_ty)
 180     }
 181 }
 182
 183 impl AstConv<'tcx> for ItemCtxt<'tcx> {
 184     fn tcx(&self) -> TyCtxt<'tcx> {
 185         self.tcx
 186     }
 187
 188     fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
 189                                  -> &'tcx ty::GenericPredicates<'tcx> {
 190         self.tcx
 191             .at(span)
 192             .type_param_predicates((self.item_def_id, def_id))
 193     }
 194
 195     fn re_infer(
 196         &self,
 197         _: Option<&ty::GenericParamDef>,
 198         _: Span,
 199     ) -> Option<ty::Region<'tcx>> {
 200         None
 201     }
 202
 203     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 204         bad_placeholder_type(self.tcx(), span).emit();
 205
 206         self.tcx().types.err
 207     }
 208
 209     fn ct_infer(
 210         &self,
 211         _: Ty<'tcx>,
 212         _: Option<&ty::GenericParamDef>,
 213         span: Span,
 214     ) -> &'tcx Const<'tcx> {
 215         bad_placeholder_type(self.tcx(), span).emit();
 216
 217         self.tcx().consts.err
 218     }
 219
 220     fn projected_ty_from_poly_trait_ref(
 221         &self,
 222         span: Span,
 223         item_def_id: DefId,
 224         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 225     ) -> Ty<'tcx> {
 226         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 227             self.tcx().mk_projection(item_def_id, trait_ref.substs)
 228         } else {
 229             // no late-bound regions, we can just ignore the binder
 230             span_err!(
 231                 self.tcx().sess,
 232                 span,
 233                 E0212,
 234                 "cannot extract an associated type from a higher-ranked trait bound \
 235                  in this context"
 236             );
 237             self.tcx().types.err
 238         }
 239     }
 240
 241     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 242         // types in item signatures are not normalized, to avoid undue
 243         // dependencies.
 244         ty
 245     }
 246
 247     fn set_tainted_by_errors(&self) {
 248         // no obvious place to track this, so just let it go
 249     }
 250
 251     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 252         // no place to record types from signatures?
 253     }
 254 }
 255
 256 fn type_param_predicates(
 257     tcx: TyCtxt<'_>,
 258     (item_def_id, def_id): (DefId, DefId),
 259 ) -> &ty::GenericPredicates<'_> {
 260     use rustc::hir::*;
 261
 262     // In the AST, bounds can derive from two places. Either
 263     // written inline like `<T : Foo>` or in a where clause like
 264     // `where T : Foo`.
 265
 266     let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 267     let param_owner = tcx.hir().ty_param_owner(param_id);
 268     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
 269     let generics = tcx.generics_of(param_owner_def_id);
 270     let index = generics.param_def_id_to_index[&def_id];
 271     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id).as_interned_str());
 272
 273     // Don't look for bounds where the type parameter isn't in scope.
 274     let parent = if item_def_id == param_owner_def_id {
 275         None
 276     } else {
 277         tcx.generics_of(item_def_id).parent
 278     };
 279
 280     let result = parent.map_or(&tcx.common.empty_predicates, |parent| {
 281         let icx = ItemCtxt::new(tcx, parent);
 282         icx.get_type_parameter_bounds(DUMMY_SP, def_id)
 283     });
 284     let mut extend = None;
 285
 286     let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
 287     let ast_generics = match tcx.hir().get(item_hir_id) {
 288         Node::TraitItem(item) => &item.generics,
 289
 290         Node::ImplItem(item) => &item.generics,
 291
 292         Node::Item(item) => {
 293             match item.node {
 294                 ItemKind::Fn(.., ref generics, _)
 295                 | ItemKind::Impl(_, _, _, ref generics, ..)
 296                 | ItemKind::Ty(_, ref generics)
 297                 | ItemKind::Existential(ExistTy {
 298                     ref generics,
 299                     impl_trait_fn: None,
 300                     ..
 301                 })
 302                 | ItemKind::Enum(_, ref generics)
 303                 | ItemKind::Struct(_, ref generics)
 304                 | ItemKind::Union(_, ref generics) => generics,
 305                 ItemKind::Trait(_, _, ref generics, ..) => {
 306                     // Implied `Self: Trait` and supertrait bounds.
 307                     if param_id == item_hir_id {
 308                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 309                         extend = Some((identity_trait_ref.to_predicate(), item.span));
 310                     }
 311                     generics
 312                 }
 313                 _ => return result,
 314             }
 315         }
 316
 317         Node::ForeignItem(item) => match item.node {
 318             ForeignItemKind::Fn(_, _, ref generics) => generics,
 319             _ => return result,
 320         },
 321
 322         _ => return result,
 323     };
 324
 325     let icx = ItemCtxt::new(tcx, item_def_id);
 326     let mut result = (*result).clone();
 327     result.predicates.extend(extend.into_iter());
 328     result.predicates
 329           .extend(icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty,
 330                   OnlySelfBounds(true)));
 331     tcx.arena.alloc(result)
 332 }
 333
 334 impl ItemCtxt<'tcx> {
 335     /// Finds bounds from `hir::Generics`. This requires scanning through the
 336     /// AST. We do this to avoid having to convert *all* the bounds, which
 337     /// would create artificial cycles. Instead we can only convert the
 338     /// bounds for a type parameter `X` if `X::Foo` is used.
 339     fn type_parameter_bounds_in_generics(
 340         &self,
 341         ast_generics: &'tcx hir::Generics,
 342         param_id: hir::HirId,
 343         ty: Ty<'tcx>,
 344         only_self_bounds: OnlySelfBounds,
 345     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 346         let from_ty_params = ast_generics
 347             .params
 348             .iter()
 349             .filter_map(|param| match param.kind {
 350                 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(&param.bounds),
 351                 _ => None,
 352             })
 353             .flat_map(|bounds| bounds.iter())
 354             .flat_map(|b| predicates_from_bound(self, ty, b));
 355
 356         let from_where_clauses = ast_generics
 357             .where_clause
 358             .predicates
 359             .iter()
 360             .filter_map(|wp| match *wp {
 361                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 362                 _ => None,
 363             })
 364             .flat_map(|bp| {
 365                 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
 366                     Some(ty)
 367                 } else if !only_self_bounds.0 {
 368                     Some(self.to_ty(&bp.bounded_ty))
 369                 } else {
 370                     None
 371                 };
 372                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
 373             })
 374             .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
 375
 376         from_ty_params.chain(from_where_clauses).collect()
 377     }
 378 }
 379
 380 /// Tests whether this is the AST for a reference to the type
 381 /// parameter with ID `param_id`. We use this so as to avoid running
 382 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
 383 /// conversion of the type to avoid inducing unnecessary cycles.
 384 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty, param_id: hir::HirId) -> bool {
 385     if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.node {
 386         match path.res {
 387             Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
 388                 def_id == tcx.hir().local_def_id(param_id)
 389             }
 390             _ => false,
 391         }
 392     } else {
 393         false
 394     }
 395 }
 396
 397 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
 398     let it = tcx.hir().expect_item(item_id);
 399     debug!("convert: item {} with id {}", it.ident, it.hir_id);
 400     let def_id = tcx.hir().local_def_id(item_id);
 401     match it.node {
 402         // These don't define types.
 403         hir::ItemKind::ExternCrate(_)
 404         | hir::ItemKind::Use(..)
 405         | hir::ItemKind::Mod(_)
 406         | hir::ItemKind::GlobalAsm(_) => {}
 407         hir::ItemKind::ForeignMod(ref foreign_mod) => {
 408             for item in &foreign_mod.items {
 409                 let def_id = tcx.hir().local_def_id(item.hir_id);
 410                 tcx.generics_of(def_id);
 411                 tcx.type_of(def_id);
 412                 tcx.predicates_of(def_id);
 413                 if let hir::ForeignItemKind::Fn(..) = item.node {
 414                     tcx.fn_sig(def_id);
 415                 }
 416             }
 417         }
 418         hir::ItemKind::Enum(ref enum_definition, _) => {
 419             tcx.generics_of(def_id);
 420             tcx.type_of(def_id);
 421             tcx.predicates_of(def_id);
 422             convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
 423         }
 424         hir::ItemKind::Impl(..) => {
 425             tcx.generics_of(def_id);
 426             tcx.type_of(def_id);
 427             tcx.impl_trait_ref(def_id);
 428             tcx.predicates_of(def_id);
 429         }
 430         hir::ItemKind::Trait(..) => {
 431             tcx.generics_of(def_id);
 432             tcx.trait_def(def_id);
 433             tcx.at(it.span).super_predicates_of(def_id);
 434             tcx.predicates_of(def_id);
 435         }
 436         hir::ItemKind::TraitAlias(..) => {
 437             tcx.generics_of(def_id);
 438             tcx.at(it.span).super_predicates_of(def_id);
 439             tcx.predicates_of(def_id);
 440         }
 441         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 442             tcx.generics_of(def_id);
 443             tcx.type_of(def_id);
 444             tcx.predicates_of(def_id);
 445
 446             for f in struct_def.fields() {
 447                 let def_id = tcx.hir().local_def_id(f.hir_id);
 448                 tcx.generics_of(def_id);
 449                 tcx.type_of(def_id);
 450                 tcx.predicates_of(def_id);
 451             }
 452
 453             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 454                 convert_variant_ctor(tcx, ctor_hir_id);
 455             }
 456         }
 457
 458         // Desugared from `impl Trait`, so visited by the function's return type.
 459         hir::ItemKind::Existential(hir::ExistTy {
 460             impl_trait_fn: Some(_),
 461             ..
 462         }) => {}
 463
 464         hir::ItemKind::Existential(..)
 465         | hir::ItemKind::Ty(..)
 466         | hir::ItemKind::Static(..)
 467         | hir::ItemKind::Const(..)
 468         | hir::ItemKind::Fn(..) => {
 469             tcx.generics_of(def_id);
 470             tcx.type_of(def_id);
 471             tcx.predicates_of(def_id);
 472             if let hir::ItemKind::Fn(..) = it.node {
 473                 tcx.fn_sig(def_id);
 474             }
 475         }
 476     }
 477 }
 478
 479 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
 480     let trait_item = tcx.hir().expect_trait_item(trait_item_id);
 481     let def_id = tcx.hir().local_def_id(trait_item.hir_id);
 482     tcx.generics_of(def_id);
 483
 484     match trait_item.node {
 485         hir::TraitItemKind::Const(..)
 486         | hir::TraitItemKind::Type(_, Some(_))
 487         | hir::TraitItemKind::Method(..) => {
 488             tcx.type_of(def_id);
 489             if let hir::TraitItemKind::Method(..) = trait_item.node {
 490                 tcx.fn_sig(def_id);
 491             }
 492         }
 493
 494         hir::TraitItemKind::Type(_, None) => {}
 495     };
 496
 497     tcx.predicates_of(def_id);
 498 }
 499
 500 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
 501     let def_id = tcx.hir().local_def_id(impl_item_id);
 502     tcx.generics_of(def_id);
 503     tcx.type_of(def_id);
 504     tcx.predicates_of(def_id);
 505     if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).node {
 506         tcx.fn_sig(def_id);
 507     }
 508 }
 509
 510 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 511     let def_id = tcx.hir().local_def_id(ctor_id);
 512     tcx.generics_of(def_id);
 513     tcx.type_of(def_id);
 514     tcx.predicates_of(def_id);
 515 }
 516
 517 fn convert_enum_variant_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, variants: &[hir::Variant]) {
 518     let def = tcx.adt_def(def_id);
 519     let repr_type = def.repr.discr_type();
 520     let initial = repr_type.initial_discriminant(tcx);
 521     let mut prev_discr = None::<Discr<'tcx>>;
 522
 523     // fill the discriminant values and field types
 524     for variant in variants {
 525         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 526         prev_discr = Some(
 527             if let Some(ref e) = variant.node.disr_expr {
 528                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 529                 def.eval_explicit_discr(tcx, expr_did)
 530             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 531                 Some(discr)
 532             } else {
 533                 struct_span_err!(
 534                     tcx.sess,
 535                     variant.span,
 536                     E0370,
 537                     "enum discriminant overflowed"
 538                 ).span_label(
 539                     variant.span,
 540                     format!("overflowed on value after {}", prev_discr.unwrap()),
 541                 ).note(&format!(
 542                     "explicitly set `{} = {}` if that is desired outcome",
 543                     variant.node.ident, wrapped_discr
 544                 ))
 545                 .emit();
 546                 None
 547             }.unwrap_or(wrapped_discr),
 548         );
 549
 550         for f in variant.node.data.fields() {
 551             let def_id = tcx.hir().local_def_id(f.hir_id);
 552             tcx.generics_of(def_id);
 553             tcx.type_of(def_id);
 554             tcx.predicates_of(def_id);
 555         }
 556
 557         // Convert the ctor, if any. This also registers the variant as
 558         // an item.
 559         if let Some(ctor_hir_id) = variant.node.data.ctor_hir_id() {
 560             convert_variant_ctor(tcx, ctor_hir_id);
 561         }
 562     }
 563 }
 564
 565 fn convert_variant(
 566     tcx: TyCtxt<'_>,
 567     variant_did: Option<DefId>,
 568     ctor_did: Option<DefId>,
 569     ident: Ident,
 570     discr: ty::VariantDiscr,
 571     def: &hir::VariantData,
 572     adt_kind: ty::AdtKind,
 573     parent_did: DefId,
 574 ) -> ty::VariantDef {
 575     let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
 576     let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
 577     let fields = def
 578         .fields()
 579         .iter()
 580         .map(|f| {
 581             let fid = tcx.hir().local_def_id(f.hir_id);
 582             let dup_span = seen_fields.get(&f.ident.modern()).cloned();
 583             if let Some(prev_span) = dup_span {
 584                 struct_span_err!(
 585                     tcx.sess,
 586                     f.span,
 587                     E0124,
 588                     "field `{}` is already declared",
 589                     f.ident
 590                 ).span_label(f.span, "field already declared")
 591                  .span_label(prev_span, format!("`{}` first declared here", f.ident))
 592                  .emit();
 593             } else {
 594                 seen_fields.insert(f.ident.modern(), f.span);
 595             }
 596
 597             ty::FieldDef {
 598                 did: fid,
 599                 ident: f.ident,
 600                 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
 601             }
 602         })
 603         .collect();
 604     let recovered = match def {
 605         hir::VariantData::Struct(_, r) => *r,
 606         _ => false,
 607     };
 608     ty::VariantDef::new(
 609         tcx,
 610         ident,
 611         variant_did,
 612         ctor_did,
 613         discr,
 614         fields,
 615         CtorKind::from_hir(def),
 616         adt_kind,
 617         parent_did,
 618         recovered,
 619     )
 620 }
 621
 622 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
 623     use rustc::hir::*;
 624
 625     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 626     let item = match tcx.hir().get(hir_id) {
 627         Node::Item(item) => item,
 628         _ => bug!(),
 629     };
 630
 631     let repr = ReprOptions::new(tcx, def_id);
 632     let (kind, variants) = match item.node {
 633         ItemKind::Enum(ref def, _) => {
 634             let mut distance_from_explicit = 0;
 635             let variants = def.variants
 636                 .iter()
 637                 .map(|v| {
 638                     let variant_did = Some(tcx.hir().local_def_id(v.node.id));
 639                     let ctor_did = v.node.data.ctor_hir_id()
 640                         .map(|hir_id| tcx.hir().local_def_id(hir_id));
 641
 642                     let discr = if let Some(ref e) = v.node.disr_expr {
 643                         distance_from_explicit = 0;
 644                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
 645                     } else {
 646                         ty::VariantDiscr::Relative(distance_from_explicit)
 647                     };
 648                     distance_from_explicit += 1;
 649
 650                     convert_variant(tcx, variant_did, ctor_did, v.node.ident, discr,
 651                                     &v.node.data, AdtKind::Enum, def_id)
 652                 })
 653                 .collect();
 654
 655             (AdtKind::Enum, variants)
 656         }
 657         ItemKind::Struct(ref def, _) => {
 658             let variant_did = None;
 659             let ctor_did = def.ctor_hir_id()
 660                 .map(|hir_id| tcx.hir().local_def_id(hir_id));
 661
 662             let variants = std::iter::once(convert_variant(
 663                 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
 664                 AdtKind::Struct, def_id,
 665             )).collect();
 666
 667             (AdtKind::Struct, variants)
 668         }
 669         ItemKind::Union(ref def, _) => {
 670             let variant_did = None;
 671             let ctor_did = def.ctor_hir_id()
 672                 .map(|hir_id| tcx.hir().local_def_id(hir_id));
 673
 674             let variants = std::iter::once(convert_variant(
 675                 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
 676                 AdtKind::Union, def_id,
 677             )).collect();
 678
 679             (AdtKind::Union, variants)
 680         },
 681         _ => bug!(),
 682     };
 683     tcx.alloc_adt_def(def_id, kind, variants, repr)
 684 }
 685
 686 /// Ensures that the super-predicates of the trait with a `DefId`
 687 /// of `trait_def_id` are converted and stored. This also ensures that
 688 /// the transitive super-predicates are converted.
 689 fn super_predicates_of(
 690     tcx: TyCtxt<'_>,
 691     trait_def_id: DefId,
 692 ) -> &ty::GenericPredicates<'_> {
 693     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
 694     let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
 695
 696     let item = match tcx.hir().get(trait_hir_id) {
 697         Node::Item(item) => item,
 698         _ => bug!("trait_node_id {} is not an item", trait_hir_id),
 699     };
 700
 701     let (generics, bounds) = match item.node {
 702         hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
 703         hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
 704         _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
 705     };
 706
 707     let icx = ItemCtxt::new(tcx, trait_def_id);
 708
 709     // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
 710     let self_param_ty = tcx.mk_self_type();
 711     let superbounds1 = AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No,
 712         item.span);
 713
 714     let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 715
 716     // Convert any explicit superbounds in the where-clause,
 717     // e.g., `trait Foo where Self: Bar`.
 718     // In the case of trait aliases, however, we include all bounds in the where-clause,
 719     // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
 720     // as one of its "superpredicates".
 721     let is_trait_alias = tcx.is_trait_alias(trait_def_id);
 722     let superbounds2 = icx.type_parameter_bounds_in_generics(
 723         generics, item.hir_id, self_param_ty, OnlySelfBounds(!is_trait_alias));
 724
 725     // Combine the two lists to form the complete set of superbounds:
 726     let superbounds: Vec<_> = superbounds1.into_iter().chain(superbounds2).collect();
 727
 728     // Now require that immediate supertraits are converted,
 729     // which will, in turn, reach indirect supertraits.
 730     for &(pred, span) in &superbounds {
 731         debug!("superbound: {:?}", pred);
 732         if let ty::Predicate::Trait(bound) = pred {
 733             tcx.at(span).super_predicates_of(bound.def_id());
 734         }
 735     }
 736
 737     tcx.arena.alloc(ty::GenericPredicates {
 738         parent: None,
 739         predicates: superbounds,
 740     })
 741 }
 742
 743 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
 744     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 745     let item = tcx.hir().expect_item(hir_id);
 746
 747     let (is_auto, unsafety) = match item.node {
 748         hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
 749         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
 750         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
 751     };
 752
 753     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
 754     if paren_sugar && !tcx.features().unboxed_closures {
 755         let mut err = tcx.sess.struct_span_err(
 756             item.span,
 757             "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
 758              which traits can use parenthetical notation",
 759         );
 760         help!(
 761             &mut err,
 762             "add `#![feature(unboxed_closures)]` to \
 763              the crate attributes to use it"
 764         );
 765         err.emit();
 766     }
 767
 768     let is_marker = tcx.has_attr(def_id, sym::marker);
 769     let def_path_hash = tcx.def_path_hash(def_id);
 770     let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
 771     tcx.arena.alloc(def)
 772 }
 773
 774 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
 775     struct LateBoundRegionsDetector<'tcx> {
 776         tcx: TyCtxt<'tcx>,
 777         outer_index: ty::DebruijnIndex,
 778         has_late_bound_regions: Option<Span>,
 779     }
 780
 781     impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
 782         fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 783             NestedVisitorMap::None
 784         }
 785
 786         fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
 787             if self.has_late_bound_regions.is_some() {
 788                 return;
 789             }
 790             match ty.node {
 791                 hir::TyKind::BareFn(..) => {
 792                     self.outer_index.shift_in(1);
 793                     intravisit::walk_ty(self, ty);
 794                     self.outer_index.shift_out(1);
 795                 }
 796                 _ => intravisit::walk_ty(self, ty),
 797             }
 798         }
 799
 800         fn visit_poly_trait_ref(
 801             &mut self,
 802             tr: &'tcx hir::PolyTraitRef,
 803             m: hir::TraitBoundModifier,
 804         ) {
 805             if self.has_late_bound_regions.is_some() {
 806                 return;
 807             }
 808             self.outer_index.shift_in(1);
 809             intravisit::walk_poly_trait_ref(self, tr, m);
 810             self.outer_index.shift_out(1);
 811         }
 812
 813         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 814             if self.has_late_bound_regions.is_some() {
 815                 return;
 816             }
 817
 818             match self.tcx.named_region(lt.hir_id) {
 819                 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
 820                 Some(rl::Region::LateBound(debruijn, _, _))
 821                 | Some(rl::Region::LateBoundAnon(debruijn, _)) if debruijn < self.outer_index => {}
 822                 Some(rl::Region::LateBound(..))
 823                 | Some(rl::Region::LateBoundAnon(..))
 824                 | Some(rl::Region::Free(..))
 825                 | None => {
 826                     self.has_late_bound_regions = Some(lt.span);
 827                 }
 828             }
 829         }
 830     }
 831
 832     fn has_late_bound_regions<'tcx>(
 833         tcx: TyCtxt<'tcx>,
 834         generics: &'tcx hir::Generics,
 835         decl: &'tcx hir::FnDecl,
 836     ) -> Option<Span> {
 837         let mut visitor = LateBoundRegionsDetector {
 838             tcx,
 839             outer_index: ty::INNERMOST,
 840             has_late_bound_regions: None,
 841         };
 842         for param in &generics.params {
 843             if let GenericParamKind::Lifetime { .. } = param.kind {
 844                 if tcx.is_late_bound(param.hir_id) {
 845                     return Some(param.span);
 846                 }
 847             }
 848         }
 849         visitor.visit_fn_decl(decl);
 850         visitor.has_late_bound_regions
 851     }
 852
 853     match node {
 854         Node::TraitItem(item) => match item.node {
 855             hir::TraitItemKind::Method(ref sig, _) => {
 856                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 857             }
 858             _ => None,
 859         },
 860         Node::ImplItem(item) => match item.node {
 861             hir::ImplItemKind::Method(ref sig, _) => {
 862                 has_late_bound_regions(tcx, &item.generics, &sig.decl)
 863             }
 864             _ => None,
 865         },
 866         Node::ForeignItem(item) => match item.node {
 867             hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
 868                 has_late_bound_regions(tcx, generics, fn_decl)
 869             }
 870             _ => None,
 871         },
 872         Node::Item(item) => match item.node {
 873             hir::ItemKind::Fn(ref fn_decl, .., ref generics, _) => {
 874                 has_late_bound_regions(tcx, generics, fn_decl)
 875             }
 876             _ => None,
 877         },
 878         _ => None,
 879     }
 880 }
 881
 882 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
 883     use rustc::hir::*;
 884
 885     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 886
 887     let node = tcx.hir().get(hir_id);
 888     let parent_def_id = match node {
 889         Node::ImplItem(_) | Node::TraitItem(_) | Node::Variant(_) |
 890         Node::Ctor(..) | Node::Field(_) => {
 891             let parent_id = tcx.hir().get_parent_item(hir_id);
 892             Some(tcx.hir().local_def_id(parent_id))
 893         }
 894         Node::Expr(&hir::Expr {
 895             node: hir::ExprKind::Closure(..),
 896             ..
 897         }) => Some(tcx.closure_base_def_id(def_id)),
 898         Node::Item(item) => match item.node {
 899             ItemKind::Existential(hir::ExistTy { impl_trait_fn, .. }) => impl_trait_fn,
 900             _ => None,
 901         },
 902         _ => None,
 903     };
 904
 905     let mut opt_self = None;
 906     let mut allow_defaults = false;
 907
 908     let no_generics = hir::Generics::empty();
 909     let ast_generics = match node {
 910         Node::TraitItem(item) => &item.generics,
 911
 912         Node::ImplItem(item) => &item.generics,
 913
 914         Node::Item(item) => {
 915             match item.node {
 916                 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
 917                     generics
 918                 }
 919
 920                 ItemKind::Ty(_, ref generics)
 921                 | ItemKind::Enum(_, ref generics)
 922                 | ItemKind::Struct(_, ref generics)
 923                 | ItemKind::Existential(hir::ExistTy { ref generics, .. })
 924                 | ItemKind::Union(_, ref generics) => {
 925                     allow_defaults = true;
 926                     generics
 927                 }
 928
 929                 ItemKind::Trait(_, _, ref generics, ..)
 930                 | ItemKind::TraitAlias(ref generics, ..) => {
 931                     // Add in the self type parameter.
 932                     //
 933                     // Something of a hack: use the node id for the trait, also as
 934                     // the node id for the Self type parameter.
 935                     let param_id = item.hir_id;
 936
 937                     opt_self = Some(ty::GenericParamDef {
 938                         index: 0,
 939                         name: kw::SelfUpper.as_interned_str(),
 940                         def_id: tcx.hir().local_def_id(param_id),
 941                         pure_wrt_drop: false,
 942                         kind: ty::GenericParamDefKind::Type {
 943                             has_default: false,
 944                             object_lifetime_default: rl::Set1::Empty,
 945                             synthetic: None,
 946                         },
 947                     });
 948
 949                     allow_defaults = true;
 950                     generics
 951                 }
 952
 953                 _ => &no_generics,
 954             }
 955         }
 956
 957         Node::ForeignItem(item) => match item.node {
 958             ForeignItemKind::Static(..) => &no_generics,
 959             ForeignItemKind::Fn(_, _, ref generics) => generics,
 960             ForeignItemKind::Type => &no_generics,
 961         },
 962
 963         _ => &no_generics,
 964     };
 965
 966     let has_self = opt_self.is_some();
 967     let mut parent_has_self = false;
 968     let mut own_start = has_self as u32;
 969     let parent_count = parent_def_id.map_or(0, |def_id| {
 970         let generics = tcx.generics_of(def_id);
 971         assert_eq!(has_self, false);
 972         parent_has_self = generics.has_self;
 973         own_start = generics.count() as u32;
 974         generics.parent_count + generics.params.len()
 975     });
 976
 977     let mut params: Vec<_> = opt_self.into_iter().collect();
 978
 979     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
 980     params.extend(
 981         early_lifetimes
 982             .enumerate()
 983             .map(|(i, param)| ty::GenericParamDef {
 984                 name: param.name.ident().as_interned_str(),
 985                 index: own_start + i as u32,
 986                 def_id: tcx.hir().local_def_id(param.hir_id),
 987                 pure_wrt_drop: param.pure_wrt_drop,
 988                 kind: ty::GenericParamDefKind::Lifetime,
 989             }),
 990     );
 991
 992     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
 993
 994     // Now create the real type parameters.
 995     let type_start = own_start - has_self as u32 + params.len() as u32;
 996     let mut i = 0;
 997     params.extend(
 998         ast_generics
 999             .params
1000             .iter()
1001             .filter_map(|param| {
1002                 let kind = match param.kind {
1003                     GenericParamKind::Type {
1004                         ref default,
1005                         synthetic,
1006                         ..
1007                     } => {
1008                         if param.name.ident().name == kw::SelfUpper {
1009                             span_bug!(
1010                                 param.span,
1011                                 "`Self` should not be the name of a regular parameter"
1012                             );
1013                         }
1014
1015                         if !allow_defaults && default.is_some() {
1016                             if !tcx.features().default_type_parameter_fallback {
1017                                 tcx.lint_hir(
1018                                     lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1019                                     param.hir_id,
1020                                     param.span,
1021                                     &format!(
1022                                         "defaults for type parameters are only allowed in \
1023                                         `struct`, `enum`, `type`, or `trait` definitions."
1024                                     ),
1025                                 );
1026                             }
1027                         }
1028
1029                         ty::GenericParamDefKind::Type {
1030                             has_default: default.is_some(),
1031                             object_lifetime_default: object_lifetime_defaults
1032                                 .as_ref()
1033                                 .map_or(rl::Set1::Empty, |o| o[i]),
1034                             synthetic,
1035                         }
1036                     }
1037                     GenericParamKind::Const { .. } => {
1038                         if param.name.ident().name == kw::SelfUpper {
1039                             span_bug!(
1040                                 param.span,
1041                                 "`Self` should not be the name of a regular parameter",
1042                             );
1043                         }
1044
1045                         ty::GenericParamDefKind::Const
1046                     }
1047                     _ => return None,
1048                 };
1049
1050                 let param_def = ty::GenericParamDef {
1051                     index: type_start + i as u32,
1052                     name: param.name.ident().as_interned_str(),
1053                     def_id: tcx.hir().local_def_id(param.hir_id),
1054                     pure_wrt_drop: param.pure_wrt_drop,
1055                     kind,
1056                 };
1057                 i += 1;
1058                 Some(param_def)
1059             })
1060     );
1061
1062     // provide junk type parameter defs - the only place that
1063     // cares about anything but the length is instantiation,
1064     // and we don't do that for closures.
1065     if let Node::Expr(&hir::Expr {
1066         node: hir::ExprKind::Closure(.., gen),
1067         ..
1068     }) = node
1069     {
1070         let dummy_args = if gen.is_some() {
1071             &["<yield_ty>", "<return_ty>", "<witness>"][..]
1072         } else {
1073             &["<closure_kind>", "<closure_signature>"][..]
1074         };
1075
1076         params.extend(
1077             dummy_args
1078                 .iter()
1079                 .enumerate()
1080                 .map(|(i, &arg)| ty::GenericParamDef {
1081                     index: type_start + i as u32,
1082                     name: InternedString::intern(arg),
1083                     def_id,
1084                     pure_wrt_drop: false,
1085                     kind: ty::GenericParamDefKind::Type {
1086                         has_default: false,
1087                         object_lifetime_default: rl::Set1::Empty,
1088                         synthetic: None,
1089                     },
1090                 }),
1091         );
1092
1093         if let Some(upvars) = tcx.upvars(def_id) {
1094             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1095                 ty::GenericParamDef {
1096                     index: type_start + i,
1097                     name: InternedString::intern("<upvar>"),
1098                     def_id,
1099                     pure_wrt_drop: false,
1100                     kind: ty::GenericParamDefKind::Type {
1101                         has_default: false,
1102                         object_lifetime_default: rl::Set1::Empty,
1103                         synthetic: None,
1104                     },
1105                 }
1106             }));
1107         }
1108     }
1109
1110     let param_def_id_to_index = params
1111         .iter()
1112         .map(|param| (param.def_id, param.index))
1113         .collect();
1114
1115     tcx.arena.alloc(ty::Generics {
1116         parent: parent_def_id,
1117         parent_count,
1118         params,
1119         param_def_id_to_index,
1120         has_self: has_self || parent_has_self,
1121         has_late_bound_regions: has_late_bound_regions(tcx, node),
1122     })
1123 }
1124
1125 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1126     span_err!(
1127         tcx.sess,
1128         span,
1129         E0202,
1130         "associated types are not yet supported in inherent impls (see #8995)"
1131     );
1132 }
1133
1134 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1135     checked_type_of(tcx, def_id, true).unwrap()
1136 }
1137
1138 fn infer_placeholder_type(
1139     tcx: TyCtxt<'_>,
1140     def_id: DefId,
1141     body_id: hir::BodyId,
1142     span: Span,
1143 ) -> Ty<'_> {
1144     let ty = tcx.typeck_tables_of(def_id).node_type(body_id.hir_id);
1145     let mut diag = bad_placeholder_type(tcx, span);
1146     if ty != tcx.types.err {
1147         diag.span_suggestion(
1148             span,
1149             "replace `_` with the correct type",
1150             ty.to_string(),
1151             Applicability::MaybeIncorrect,
1152         );
1153     }
1154     diag.emit();
1155     ty
1156 }
1157
1158 /// Same as [`type_of`] but returns [`Option`] instead of failing.
1159 ///
1160 /// If you want to fail anyway, you can set the `fail` parameter to true, but in this case,
1161 /// you'd better just call [`type_of`] directly.
1162 pub fn checked_type_of(tcx: TyCtxt<'_>, def_id: DefId, fail: bool) -> Option<Ty<'_>> {
1163     use rustc::hir::*;
1164
1165     let hir_id = match tcx.hir().as_local_hir_id(def_id) {
1166         Some(hir_id) => hir_id,
1167         None => {
1168             if !fail {
1169                 return None;
1170             }
1171             bug!("invalid node");
1172         }
1173     };
1174
1175     let icx = ItemCtxt::new(tcx, def_id);
1176
1177     Some(match tcx.hir().get(hir_id) {
1178         Node::TraitItem(item) => match item.node {
1179             TraitItemKind::Method(..) => {
1180                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1181                 tcx.mk_fn_def(def_id, substs)
1182             }
1183             TraitItemKind::Const(ref ty, body_id)  => {
1184                 body_id.and_then(|body_id| {
1185                     if let hir::TyKind::Infer = ty.node {
1186                         Some(infer_placeholder_type(tcx, def_id, body_id, ty.span))
1187                     } else {
1188                         None
1189                     }
1190                 }).unwrap_or_else(|| icx.to_ty(ty))
1191             },
1192             TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1193             TraitItemKind::Type(_, None) => {
1194                 if !fail {
1195                     return None;
1196                 }
1197                 span_bug!(item.span, "associated type missing default");
1198             }
1199         },
1200
1201         Node::ImplItem(item) => match item.node {
1202             ImplItemKind::Method(..) => {
1203                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1204                 tcx.mk_fn_def(def_id, substs)
1205             }
1206             ImplItemKind::Const(ref ty, body_id) => {
1207                 if let hir::TyKind::Infer = ty.node {
1208                     infer_placeholder_type(tcx, def_id, body_id, ty.span)
1209                 } else {
1210                     icx.to_ty(ty)
1211                 }
1212             },
1213             ImplItemKind::Existential(_) => {
1214                 if tcx
1215                     .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1216                     .is_none()
1217                 {
1218                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1219                 }
1220
1221                 find_existential_constraints(tcx, def_id)
1222             }
1223             ImplItemKind::Type(ref ty) => {
1224                 if tcx
1225                     .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1226                     .is_none()
1227                 {
1228                     report_assoc_ty_on_inherent_impl(tcx, item.span);
1229                 }
1230
1231                 icx.to_ty(ty)
1232             }
1233         },
1234
1235         Node::Item(item) => {
1236             match item.node {
1237                 ItemKind::Static(ref ty, .., body_id)
1238                 | ItemKind::Const(ref ty, body_id) => {
1239                     if let hir::TyKind::Infer = ty.node {
1240                         infer_placeholder_type(tcx, def_id, body_id, ty.span)
1241                     } else {
1242                         icx.to_ty(ty)
1243                     }
1244                 },
1245                 ItemKind::Ty(ref ty, _)
1246                 | ItemKind::Impl(.., ref ty, _) => icx.to_ty(ty),
1247                 ItemKind::Fn(..) => {
1248                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1249                     tcx.mk_fn_def(def_id, substs)
1250                 }
1251                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1252                     let def = tcx.adt_def(def_id);
1253                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
1254                     tcx.mk_adt(def, substs)
1255                 }
1256                 ItemKind::Existential(hir::ExistTy {
1257                     impl_trait_fn: None,
1258                     ..
1259                 }) => find_existential_constraints(tcx, def_id),
1260                 // Existential types desugared from `impl Trait`.
1261                 ItemKind::Existential(hir::ExistTy {
1262                     impl_trait_fn: Some(owner),
1263                     ..
1264                 }) => {
1265                     tcx.typeck_tables_of(owner)
1266                         .concrete_existential_types
1267                         .get(&def_id)
1268                         .map(|opaque| opaque.concrete_type)
1269                         .unwrap_or_else(|| {
1270                             // This can occur if some error in the
1271                             // owner fn prevented us from populating
1272                             // the `concrete_existential_types` table.
1273                             tcx.sess.delay_span_bug(
1274                                 DUMMY_SP,
1275                                 &format!(
1276                                     "owner {:?} has no existential type for {:?} in its tables",
1277                                     owner, def_id,
1278                                 ),
1279                             );
1280                             tcx.types.err
1281                         })
1282                 }
1283                 ItemKind::Trait(..)
1284                 | ItemKind::TraitAlias(..)
1285                 | ItemKind::Mod(..)
1286                 | ItemKind::ForeignMod(..)
1287                 | ItemKind::GlobalAsm(..)
1288                 | ItemKind::ExternCrate(..)
1289                 | ItemKind::Use(..) => {
1290                     if !fail {
1291                         return None;
1292                     }
1293                     span_bug!(
1294                         item.span,
1295                         "compute_type_of_item: unexpected item type: {:?}",
1296                         item.node
1297                     );
1298                 }
1299             }
1300         }
1301
1302         Node::ForeignItem(foreign_item) => match foreign_item.node {
1303             ForeignItemKind::Fn(..) => {
1304                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1305                 tcx.mk_fn_def(def_id, substs)
1306             }
1307             ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1308             ForeignItemKind::Type => tcx.mk_foreign(def_id),
1309         },
1310
1311         Node::Ctor(&ref def) | Node::Variant(&Spanned {
1312             node: hir::VariantKind { data: ref def, .. },
1313             ..
1314         }) => match *def {
1315             VariantData::Unit(..) | VariantData::Struct(..) => {
1316                 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1317             }
1318             VariantData::Tuple(..) => {
1319                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1320                 tcx.mk_fn_def(def_id, substs)
1321             }
1322         },
1323
1324         Node::Field(field) => icx.to_ty(&field.ty),
1325
1326         Node::Expr(&hir::Expr {
1327             node: hir::ExprKind::Closure(.., gen),
1328             ..
1329         }) => {
1330             if gen.is_some() {
1331                 return Some(tcx.typeck_tables_of(def_id).node_type(hir_id));
1332             }
1333
1334             let substs = ty::ClosureSubsts {
1335                 substs: InternalSubsts::identity_for_item(tcx, def_id),
1336             };
1337
1338             tcx.mk_closure(def_id, substs)
1339         }
1340
1341         Node::AnonConst(_) => {
1342             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1343             match parent_node {
1344                 Node::Ty(&hir::Ty {
1345                     node: hir::TyKind::Array(_, ref constant),
1346                     ..
1347                 })
1348                 | Node::Ty(&hir::Ty {
1349                     node: hir::TyKind::Typeof(ref constant),
1350                     ..
1351                 })
1352                 | Node::Expr(&hir::Expr {
1353                     node: ExprKind::Repeat(_, ref constant),
1354                     ..
1355                 }) if constant.hir_id == hir_id =>
1356                 {
1357                     tcx.types.usize
1358                 }
1359
1360                 Node::Variant(&Spanned {
1361                     node:
1362                         VariantKind {
1363                             disr_expr: Some(ref e),
1364                             ..
1365                         },
1366                     ..
1367                 }) if e.hir_id == hir_id =>
1368                 {
1369                     tcx.adt_def(tcx.hir().get_parent_did(hir_id))
1370                         .repr
1371                         .discr_type()
1372                         .to_ty(tcx)
1373                 }
1374
1375                 Node::Ty(&hir::Ty { node: hir::TyKind::Path(_), .. }) |
1376                 Node::Expr(&hir::Expr { node: ExprKind::Struct(..), .. }) |
1377                 Node::Expr(&hir::Expr { node: ExprKind::Path(_), .. }) |
1378                 Node::TraitRef(..) => {
1379                     let path = match parent_node {
1380                         Node::Ty(&hir::Ty {
1381                             node: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1382                             ..
1383                         })
1384                         | Node::Expr(&hir::Expr {
1385                             node: ExprKind::Path(QPath::Resolved(_, ref path)),
1386                             ..
1387                         }) => {
1388                             Some(&**path)
1389                         }
1390                         Node::Expr(&hir::Expr { node: ExprKind::Struct(ref path, ..), .. }) => {
1391                             if let QPath::Resolved(_, ref path) = **path {
1392                                 Some(&**path)
1393                             } else {
1394                                 None
1395                             }
1396                         }
1397                         Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1398                         _ => None,
1399                     };
1400
1401                     if let Some(path) = path {
1402                         let arg_index = path.segments.iter()
1403                             .filter_map(|seg| seg.args.as_ref())
1404                             .map(|generic_args| generic_args.args.as_ref())
1405                             .find_map(|args| {
1406                                 args.iter()
1407                                     .filter(|arg| arg.is_const())
1408                                     .enumerate()
1409                                     .filter(|(_, arg)| arg.id() == hir_id)
1410                                     .map(|(index, _)| index)
1411                                     .next()
1412                             })
1413                             .or_else(|| {
1414                                 if !fail {
1415                                     None
1416                                 } else {
1417                                     bug!("no arg matching AnonConst in path")
1418                                 }
1419                             })?;
1420
1421                         // We've encountered an `AnonConst` in some path, so we need to
1422                         // figure out which generic parameter it corresponds to and return
1423                         // the relevant type.
1424                         let generics = match path.res {
1425                             Res::Def(DefKind::Ctor(..), def_id) => {
1426                                 tcx.generics_of(tcx.parent(def_id).unwrap())
1427                             }
1428                             Res::Def(_, def_id) => tcx.generics_of(def_id),
1429                             Res::Err => return Some(tcx.types.err),
1430                             _ if !fail => return None,
1431                             res => {
1432                                 tcx.sess.delay_span_bug(
1433                                     DUMMY_SP,
1434                                     &format!(
1435                                         "unexpected const parent path def {:?}",
1436                                         res,
1437                                     ),
1438                                 );
1439                                 return Some(tcx.types.err);
1440                             }
1441                         };
1442
1443                         generics.params.iter()
1444                             .filter(|param| {
1445                                 if let ty::GenericParamDefKind::Const = param.kind {
1446                                     true
1447                                 } else {
1448                                     false
1449                                 }
1450                             })
1451                             .nth(arg_index)
1452                             .map(|param| tcx.type_of(param.def_id))
1453                             // This is no generic parameter associated with the arg. This is
1454                             // probably from an extra arg where one is not needed.
1455                             .unwrap_or(tcx.types.err)
1456                     } else {
1457                         if !fail {
1458                             return None;
1459                         }
1460                         tcx.sess.delay_span_bug(
1461                             DUMMY_SP,
1462                             &format!(
1463                                 "unexpected const parent path {:?}",
1464                                 parent_node,
1465                             ),
1466                         );
1467                         return Some(tcx.types.err);
1468                     }
1469                 }
1470
1471                 x => {
1472                     if !fail {
1473                         return None;
1474                     }
1475                     tcx.sess.delay_span_bug(
1476                         DUMMY_SP,
1477                         &format!(
1478                             "unexpected const parent in type_of_def_id(): {:?}", x
1479                         ),
1480                     );
1481                     tcx.types.err
1482                 }
1483             }
1484         }
1485
1486         Node::GenericParam(param) => match &param.kind {
1487             hir::GenericParamKind::Type { default: Some(ref ty), .. } |
1488             hir::GenericParamKind::Const { ref ty, .. } => {
1489                 icx.to_ty(ty)
1490             }
1491             x => {
1492                 if !fail {
1493                     return None;
1494                 }
1495                 bug!("unexpected non-type Node::GenericParam: {:?}", x)
1496             },
1497         },
1498
1499         x => {
1500             if !fail {
1501                 return None;
1502             }
1503             bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1504         }
1505     })
1506 }
1507
1508 fn find_existential_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1509     use rustc::hir::{ImplItem, Item, TraitItem};
1510
1511     debug!("find_existential_constraints({:?})", def_id);
1512
1513     struct ConstraintLocator<'tcx> {
1514         tcx: TyCtxt<'tcx>,
1515         def_id: DefId,
1516         // (first found type span, actual type, mapping from the existential type's generic
1517         // parameters to the concrete type's generic parameters)
1518         //
1519         // The mapping is an index for each use site of a generic parameter in the concrete type
1520         //
1521         // The indices index into the generic parameters on the existential type.
1522         found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1523     }
1524
1525     impl ConstraintLocator<'tcx> {
1526         fn check(&mut self, def_id: DefId) {
1527             // Don't try to check items that cannot possibly constrain the type.
1528             if !self.tcx.has_typeck_tables(def_id) {
1529                 debug!(
1530                     "find_existential_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1531                     self.def_id,
1532                     def_id,
1533                 );
1534                 return;
1535             }
1536             let ty = self
1537                 .tcx
1538                 .typeck_tables_of(def_id)
1539                 .concrete_existential_types
1540                 .get(&self.def_id);
1541             if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1542                 debug!(
1543                     "find_existential_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1544                     self.def_id,
1545                     def_id,
1546                     ty,
1547                 );
1548
1549                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1550                 let span = self.tcx.def_span(def_id);
1551                 // used to quickly look up the position of a generic parameter
1552                 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1553                 // Skipping binder is ok, since we only use this to find generic parameters and
1554                 // their positions.
1555                 for (idx, subst) in substs.iter().enumerate() {
1556                     if let UnpackedKind::Type(ty) = subst.unpack() {
1557                         if let ty::Param(p) = ty.sty {
1558                             if index_map.insert(p, idx).is_some() {
1559                                 // There was already an entry for `p`, meaning a generic parameter
1560                                 // was used twice.
1561                                 self.tcx.sess.span_err(
1562                                     span,
1563                                     &format!(
1564                                         "defining existential type use restricts existential \
1565                                          type by using the generic parameter `{}` twice",
1566                                         p.name
1567                                     ),
1568                                 );
1569                                 return;
1570                             }
1571                         } else {
1572                             self.tcx.sess.delay_span_bug(
1573                                 span,
1574                                 &format!(
1575                                     "non-defining exist ty use in defining scope: {:?}, {:?}",
1576                                     concrete_type, substs,
1577                                 ),
1578                             );
1579                         }
1580                     }
1581                 }
1582                 // Compute the index within the existential type for each generic parameter used in
1583                 // the concrete type.
1584                 let indices = concrete_type
1585                     .subst(self.tcx, substs)
1586                     .walk()
1587                     .filter_map(|t| match &t.sty {
1588                         ty::Param(p) => Some(*index_map.get(p).unwrap()),
1589                         _ => None,
1590                     }).collect();
1591                 let is_param = |ty: Ty<'_>| match ty.sty {
1592                     ty::Param(_) => true,
1593                     _ => false,
1594                 };
1595                 if !substs.types().all(is_param) {
1596                     self.tcx.sess.span_err(
1597                         span,
1598                         "defining existential type use does not fully define existential type",
1599                     );
1600                 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1601                     let mut ty = concrete_type.walk().fuse();
1602                     let mut p_ty = prev_ty.walk().fuse();
1603                     let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.sty, &p.sty) {
1604                         // Type parameters are equal to any other type parameter for the purpose of
1605                         // concrete type equality, as it is possible to obtain the same type just
1606                         // by passing matching parameters to a function.
1607                         (ty::Param(_), ty::Param(_)) => true,
1608                         _ => t == p,
1609                     });
1610                     if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1611                         debug!("find_existential_constraints: span={:?}", span);
1612                         // Found different concrete types for the existential type.
1613                         let mut err = self.tcx.sess.struct_span_err(
1614                             span,
1615                             "concrete type differs from previous defining existential type use",
1616                         );
1617                         err.span_label(
1618                             span,
1619                             format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1620                         );
1621                         err.span_note(prev_span, "previous use here");
1622                         err.emit();
1623                     } else if indices != *prev_indices {
1624                         // Found "same" concrete types, but the generic parameter order differs.
1625                         let mut err = self.tcx.sess.struct_span_err(
1626                             span,
1627                             "concrete type's generic parameters differ from previous defining use",
1628                         );
1629                         use std::fmt::Write;
1630                         let mut s = String::new();
1631                         write!(s, "expected [").unwrap();
1632                         let list = |s: &mut String, indices: &Vec<usize>| {
1633                             let mut indices = indices.iter().cloned();
1634                             if let Some(first) = indices.next() {
1635                                 write!(s, "`{}`", substs[first]).unwrap();
1636                                 for i in indices {
1637                                     write!(s, ", `{}`", substs[i]).unwrap();
1638                                 }
1639                             }
1640                         };
1641                         list(&mut s, prev_indices);
1642                         write!(s, "], got [").unwrap();
1643                         list(&mut s, &indices);
1644                         write!(s, "]").unwrap();
1645                         err.span_label(span, s);
1646                         err.span_note(prev_span, "previous use here");
1647                         err.emit();
1648                     }
1649                 } else {
1650                     self.found = Some((span, concrete_type, indices));
1651                 }
1652             } else {
1653                 debug!(
1654                     "find_existential_constraints: no constraint for `{:?}` at `{:?}`",
1655                     self.def_id,
1656                     def_id,
1657                 );
1658             }
1659         }
1660     }
1661
1662     impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1663         fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1664             intravisit::NestedVisitorMap::All(&self.tcx.hir())
1665         }
1666         fn visit_item(&mut self, it: &'tcx Item) {
1667             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1668             // The existential type itself or its children are not within its reveal scope.
1669             if def_id != self.def_id {
1670                 self.check(def_id);
1671                 intravisit::walk_item(self, it);
1672             }
1673         }
1674         fn visit_impl_item(&mut self, it: &'tcx ImplItem) {
1675             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1676             // The existential type itself or its children are not within its reveal scope.
1677             if def_id != self.def_id {
1678                 self.check(def_id);
1679                 intravisit::walk_impl_item(self, it);
1680             }
1681         }
1682         fn visit_trait_item(&mut self, it: &'tcx TraitItem) {
1683             let def_id = self.tcx.hir().local_def_id(it.hir_id);
1684             self.check(def_id);
1685             intravisit::walk_trait_item(self, it);
1686         }
1687     }
1688
1689     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1690     let scope = tcx.hir()
1691         .get_defining_scope(hir_id)
1692         .expect("could not get defining scope");
1693     let mut locator = ConstraintLocator {
1694         def_id,
1695         tcx,
1696         found: None,
1697     };
1698
1699     debug!("find_existential_constraints: scope={:?}", scope);
1700
1701     if scope == hir::CRATE_HIR_ID {
1702         intravisit::walk_crate(&mut locator, tcx.hir().krate());
1703     } else {
1704         debug!("find_existential_constraints: scope={:?}", tcx.hir().get(scope));
1705         match tcx.hir().get(scope) {
1706             Node::Item(ref it) => intravisit::walk_item(&mut locator, it),
1707             Node::ImplItem(ref it) => intravisit::walk_impl_item(&mut locator, it),
1708             Node::TraitItem(ref it) => intravisit::walk_trait_item(&mut locator, it),
1709             other => bug!(
1710                 "{:?} is not a valid scope for an existential type item",
1711                 other
1712             ),
1713         }
1714     }
1715
1716     match locator.found {
1717         Some((_, ty, _)) => ty,
1718         None => {
1719             let span = tcx.def_span(def_id);
1720             tcx.sess.span_err(span, "could not find defining uses");
1721             tcx.types.err
1722         }
1723     }
1724 }
1725
1726 pub fn get_infer_ret_ty(output: &'_ hir::FunctionRetTy) -> Option<&hir::Ty> {
1727     if let hir::FunctionRetTy::Return(ref ty) = output {
1728         if let hir::TyKind::Infer = ty.node {
1729             return Some(&**ty)
1730         }
1731     }
1732     None
1733 }
1734
1735 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1736     use rustc::hir::*;
1737     use rustc::hir::Node::*;
1738
1739     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1740
1741     let icx = ItemCtxt::new(tcx, def_id);
1742
1743     match tcx.hir().get(hir_id) {
1744         TraitItem(hir::TraitItem {
1745             node: TraitItemKind::Method(MethodSig { header, decl }, TraitMethod::Provided(_)),
1746             ..
1747         })
1748         | ImplItem(hir::ImplItem {
1749             node: ImplItemKind::Method(MethodSig { header, decl }, _),
1750             ..
1751         })
1752         | Item(hir::Item {
1753             node: ItemKind::Fn(decl, header, _, _),
1754             ..
1755         }) => match get_infer_ret_ty(&decl.output) {
1756             Some(ty) => {
1757                 let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1758                 let mut diag = bad_placeholder_type(tcx, ty.span);
1759                 let ret_ty = fn_sig.output();
1760                 if ret_ty != tcx.types.err  {
1761                     diag.span_suggestion(
1762                         ty.span,
1763                         "replace `_` with the correct return type",
1764                         ret_ty.to_string(),
1765                         Applicability::MaybeIncorrect,
1766                     );
1767                 }
1768                 diag.emit();
1769                 ty::Binder::bind(fn_sig)
1770             },
1771             None => AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl)
1772         },
1773
1774         TraitItem(hir::TraitItem {
1775             node: TraitItemKind::Method(MethodSig { header, decl }, _),
1776             ..
1777         }) => {
1778             AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl)
1779         },
1780
1781         ForeignItem(&hir::ForeignItem {
1782             node: ForeignItemKind::Fn(ref fn_decl, _, _),
1783             ..
1784         }) => {
1785             let abi = tcx.hir().get_foreign_abi(hir_id);
1786             compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1787         }
1788
1789         Ctor(data) | Variant(Spanned {
1790             node: hir::VariantKind { data, ..  },
1791             ..
1792         }) if data.ctor_hir_id().is_some() => {
1793             let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1794             let inputs = data.fields()
1795                 .iter()
1796                 .map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1797             ty::Binder::bind(tcx.mk_fn_sig(
1798                 inputs,
1799                 ty,
1800                 false,
1801                 hir::Unsafety::Normal,
1802                 abi::Abi::Rust,
1803             ))
1804         }
1805
1806         Expr(&hir::Expr {
1807             node: hir::ExprKind::Closure(..),
1808             ..
1809         }) => {
1810             // Closure signatures are not like other function
1811             // signatures and cannot be accessed through `fn_sig`. For
1812             // example, a closure signature excludes the `self`
1813             // argument. In any case they are embedded within the
1814             // closure type as part of the `ClosureSubsts`.
1815             //
1816             // To get
1817             // the signature of a closure, you should use the
1818             // `closure_sig` method on the `ClosureSubsts`:
1819             //
1820             //    closure_substs.closure_sig(def_id, tcx)
1821             //
1822             // or, inside of an inference context, you can use
1823             //
1824             //    infcx.closure_sig(def_id, closure_substs)
1825             bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1826         }
1827
1828         x => {
1829             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1830         }
1831     }
1832 }
1833
1834 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1835     let icx = ItemCtxt::new(tcx, def_id);
1836
1837     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1838     match tcx.hir().expect_item(hir_id).node {
1839         hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1840             opt_trait_ref.as_ref().map(|ast_trait_ref| {
1841                 let selfty = tcx.type_of(def_id);
1842                 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1843             })
1844         }
1845         _ => bug!(),
1846     }
1847 }
1848
1849 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> hir::ImplPolarity {
1850     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1851     match tcx.hir().expect_item(hir_id).node {
1852         hir::ItemKind::Impl(_, polarity, ..) => polarity,
1853         ref item => bug!("impl_polarity: {:?} not an impl", item),
1854     }
1855 }
1856
1857 /// Returns the early-bound lifetimes declared in this generics
1858 /// listing. For anything other than fns/methods, this is just all
1859 /// the lifetimes that are declared. For fns or methods, we have to
1860 /// screen out those that do not appear in any where-clauses etc using
1861 /// `resolve_lifetime::early_bound_lifetimes`.
1862 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1863     tcx: TyCtxt<'tcx>,
1864     generics: &'a hir::Generics,
1865 ) -> impl Iterator<Item = &'a hir::GenericParam> + Captures<'tcx> {
1866     generics
1867         .params
1868         .iter()
1869         .filter(move |param| match param.kind {
1870             GenericParamKind::Lifetime { .. } => {
1871                 !tcx.is_late_bound(param.hir_id)
1872             }
1873             _ => false,
1874         })
1875 }
1876
1877 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1878 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1879 /// inferred constraints concerning which regions outlive other regions.
1880 fn predicates_defined_on(
1881     tcx: TyCtxt<'_>,
1882     def_id: DefId,
1883 ) -> &ty::GenericPredicates<'_> {
1884     debug!("predicates_defined_on({:?})", def_id);
1885     let mut result = tcx.explicit_predicates_of(def_id);
1886     debug!(
1887         "predicates_defined_on: explicit_predicates_of({:?}) = {:?}",
1888         def_id,
1889         result,
1890     );
1891     let inferred_outlives = tcx.inferred_outlives_of(def_id);
1892     if !inferred_outlives.is_empty() {
1893         let span = tcx.def_span(def_id);
1894         debug!(
1895             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1896             def_id,
1897             inferred_outlives,
1898         );
1899         let mut predicates = (*result).clone();
1900         predicates.predicates.extend(inferred_outlives.iter().map(|&p| (p, span)));
1901         result = tcx.arena.alloc(predicates);
1902     }
1903     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1904     result
1905 }
1906
1907 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1908 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1909 /// `Self: Trait` predicates for traits.
1910 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::GenericPredicates<'_> {
1911     let mut result = tcx.predicates_defined_on(def_id);
1912
1913     if tcx.is_trait(def_id) {
1914         // For traits, add `Self: Trait` predicate. This is
1915         // not part of the predicates that a user writes, but it
1916         // is something that one must prove in order to invoke a
1917         // method or project an associated type.
1918         //
1919         // In the chalk setup, this predicate is not part of the
1920         // "predicates" for a trait item. But it is useful in
1921         // rustc because if you directly (e.g.) invoke a trait
1922         // method like `Trait::method(...)`, you must naturally
1923         // prove that the trait applies to the types that were
1924         // used, and adding the predicate into this list ensures
1925         // that this is done.
1926         let span = tcx.def_span(def_id);
1927         let mut predicates = (*result).clone();
1928         predicates.predicates.push((ty::TraitRef::identity(tcx, def_id).to_predicate(), span));
1929         result = tcx.arena.alloc(predicates);
1930     }
1931     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1932     result
1933 }
1934
1935 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1936 /// N.B., this does not include any implied/inferred constraints.
1937 fn explicit_predicates_of(
1938     tcx: TyCtxt<'_>,
1939     def_id: DefId,
1940 ) -> &ty::GenericPredicates<'_> {
1941     use rustc::hir::*;
1942     use rustc_data_structures::fx::FxHashSet;
1943
1944     debug!("explicit_predicates_of(def_id={:?})", def_id);
1945
1946     /// A data structure with unique elements, which preserves order of insertion.
1947     /// Preserving the order of insertion is important here so as not to break
1948     /// compile-fail UI tests.
1949     struct UniquePredicates<'tcx> {
1950         predicates: Vec<(ty::Predicate<'tcx>, Span)>,
1951         uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
1952     }
1953
1954     impl<'tcx> UniquePredicates<'tcx> {
1955         fn new() -> Self {
1956             UniquePredicates {
1957                 predicates: vec![],
1958                 uniques: FxHashSet::default(),
1959             }
1960         }
1961
1962         fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
1963             if self.uniques.insert(value) {
1964                 self.predicates.push(value);
1965             }
1966         }
1967
1968         fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
1969             for value in iter {
1970                 self.push(value);
1971             }
1972         }
1973     }
1974
1975     let hir_id = match tcx.hir().as_local_hir_id(def_id) {
1976         Some(hir_id) => hir_id,
1977         None => return tcx.predicates_of(def_id),
1978     };
1979     let node = tcx.hir().get(hir_id);
1980
1981     let mut is_trait = None;
1982     let mut is_default_impl_trait = None;
1983
1984     let icx = ItemCtxt::new(tcx, def_id);
1985
1986     const NO_GENERICS: &hir::Generics = &hir::Generics::empty();
1987
1988     let empty_trait_items = HirVec::new();
1989
1990     let mut predicates = UniquePredicates::new();
1991
1992     let ast_generics = match node {
1993         Node::TraitItem(item) => &item.generics,
1994
1995         Node::ImplItem(item) => match item.node {
1996             ImplItemKind::Existential(ref bounds) => {
1997                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1998                 let opaque_ty = tcx.mk_opaque(def_id, substs);
1999
2000                 // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2001                 let bounds = AstConv::compute_bounds(
2002                     &icx,
2003                     opaque_ty,
2004                     bounds,
2005                     SizedByDefault::Yes,
2006                     tcx.def_span(def_id),
2007                 );
2008
2009                 predicates.extend(bounds.predicates(tcx, opaque_ty));
2010                 &item.generics
2011             }
2012             _ => &item.generics,
2013         },
2014
2015         Node::Item(item) => {
2016             match item.node {
2017                 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
2018                     if defaultness.is_default() {
2019                         is_default_impl_trait = tcx.impl_trait_ref(def_id);
2020                     }
2021                     generics
2022                 }
2023                 ItemKind::Fn(.., ref generics, _)
2024                 | ItemKind::Ty(_, ref generics)
2025                 | ItemKind::Enum(_, ref generics)
2026                 | ItemKind::Struct(_, ref generics)
2027                 | ItemKind::Union(_, ref generics) => generics,
2028
2029                 ItemKind::Trait(_, _, ref generics, .., ref items) => {
2030                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2031                     generics
2032                 }
2033                 ItemKind::TraitAlias(ref generics, _) => {
2034                     is_trait = Some((ty::TraitRef::identity(tcx, def_id), &empty_trait_items));
2035                     generics
2036                 }
2037                 ItemKind::Existential(ExistTy {
2038                     ref bounds,
2039                     impl_trait_fn,
2040                     ref generics,
2041                     origin: _,
2042                 }) => {
2043                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
2044                     let opaque_ty = tcx.mk_opaque(def_id, substs);
2045
2046                     // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2047                     let bounds = AstConv::compute_bounds(
2048                         &icx,
2049                         opaque_ty,
2050                         bounds,
2051                         SizedByDefault::Yes,
2052                         tcx.def_span(def_id),
2053                     );
2054
2055                     let bounds_predicates = bounds.predicates(tcx, opaque_ty);
2056                     if impl_trait_fn.is_some() {
2057                         // opaque types
2058                         return tcx.arena.alloc(ty::GenericPredicates {
2059                             parent: None,
2060                             predicates: bounds_predicates,
2061                         });
2062                     } else {
2063                         // named existential types
2064                         predicates.extend(bounds_predicates);
2065                         generics
2066                     }
2067                 }
2068
2069                 _ => NO_GENERICS,
2070             }
2071         }
2072
2073         Node::ForeignItem(item) => match item.node {
2074             ForeignItemKind::Static(..) => NO_GENERICS,
2075             ForeignItemKind::Fn(_, _, ref generics) => generics,
2076             ForeignItemKind::Type => NO_GENERICS,
2077         },
2078
2079         _ => NO_GENERICS,
2080     };
2081
2082     let generics = tcx.generics_of(def_id);
2083     let parent_count = generics.parent_count as u32;
2084     let has_own_self = generics.has_self && parent_count == 0;
2085
2086     // Below we'll consider the bounds on the type parameters (including `Self`)
2087     // and the explicit where-clauses, but to get the full set of predicates
2088     // on a trait we need to add in the supertrait bounds and bounds found on
2089     // associated types.
2090     if let Some((_trait_ref, _)) = is_trait {
2091         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2092     }
2093
2094     // In default impls, we can assume that the self type implements
2095     // the trait. So in:
2096     //
2097     //     default impl Foo for Bar { .. }
2098     //
2099     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2100     // (see below). Recall that a default impl is not itself an impl, but rather a
2101     // set of defaults that can be incorporated into another impl.
2102     if let Some(trait_ref) = is_default_impl_trait {
2103         predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2104     }
2105
2106     // Collect the region predicates that were declared inline as
2107     // well. In the case of parameters declared on a fn or method, we
2108     // have to be careful to only iterate over early-bound regions.
2109     let mut index = parent_count + has_own_self as u32;
2110     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2111         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2112             def_id: tcx.hir().local_def_id(param.hir_id),
2113             index,
2114             name: param.name.ident().as_interned_str(),
2115         }));
2116         index += 1;
2117
2118         match param.kind {
2119             GenericParamKind::Lifetime { .. } => {
2120                 param.bounds.iter().for_each(|bound| match bound {
2121                     hir::GenericBound::Outlives(lt) => {
2122                         let bound = AstConv::ast_region_to_region(&icx, &lt, None);
2123                         let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2124                         predicates.push((outlives.to_predicate(), lt.span));
2125                     }
2126                     _ => bug!(),
2127                 });
2128             }
2129             _ => bug!(),
2130         }
2131     }
2132
2133     // Collect the predicates that were written inline by the user on each
2134     // type parameter (e.g., `<T: Foo>`).
2135     for param in &ast_generics.params {
2136         if let GenericParamKind::Type { .. } = param.kind {
2137             let name = param.name.ident().as_interned_str();
2138             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2139             index += 1;
2140
2141             let sized = SizedByDefault::Yes;
2142             let bounds = AstConv::compute_bounds(&icx, param_ty, &param.bounds, sized, param.span);
2143             predicates.extend(bounds.predicates(tcx, param_ty));
2144         }
2145     }
2146
2147     // Add in the bounds that appear in the where-clause.
2148     let where_clause = &ast_generics.where_clause;
2149     for predicate in &where_clause.predicates {
2150         match predicate {
2151             &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2152                 let ty = icx.to_ty(&bound_pred.bounded_ty);
2153
2154                 // Keep the type around in a dummy predicate, in case of no bounds.
2155                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2156                 // is still checked for WF.
2157                 if bound_pred.bounds.is_empty() {
2158                     if let ty::Param(_) = ty.sty {
2159                         // This is a `where T:`, which can be in the HIR from the
2160                         // transformation that moves `?Sized` to `T`'s declaration.
2161                         // We can skip the predicate because type parameters are
2162                         // trivially WF, but also we *should*, to avoid exposing
2163                         // users who never wrote `where Type:,` themselves, to
2164                         // compiler/tooling bugs from not handling WF predicates.
2165                     } else {
2166                         let span = bound_pred.bounded_ty.span;
2167                         let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2168                         predicates.push(
2169                             (ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)), span)
2170                         );
2171                     }
2172                 }
2173
2174                 for bound in bound_pred.bounds.iter() {
2175                     match bound {
2176                         &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2177                             let mut bounds = Bounds::default();
2178
2179                             let (trait_ref, _) = AstConv::instantiate_poly_trait_ref(
2180                                 &icx,
2181                                 poly_trait_ref,
2182                                 ty,
2183                                 &mut bounds,
2184                             );
2185
2186                             predicates.push((trait_ref.to_predicate(), poly_trait_ref.span));
2187                             predicates.extend(bounds.predicates(tcx, ty));
2188                         }
2189
2190                         &hir::GenericBound::Outlives(ref lifetime) => {
2191                             let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2192                             let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2193                             predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2194                         }
2195                     }
2196                 }
2197             }
2198
2199             &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2200                 let r1 = AstConv::ast_region_to_region(&icx, &region_pred.lifetime, None);
2201                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2202                     let (r2, span) = match bound {
2203                         hir::GenericBound::Outlives(lt) => {
2204                             (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2205                         }
2206                         _ => bug!(),
2207                     };
2208                     let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2209
2210                     (ty::Predicate::RegionOutlives(pred), span)
2211                 }))
2212             }
2213
2214             &hir::WherePredicate::EqPredicate(..) => {
2215                 // FIXME(#20041)
2216             }
2217         }
2218     }
2219
2220     // Add predicates from associated type bounds.
2221     if let Some((self_trait_ref, trait_items)) = is_trait {
2222         predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2223             let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2224             let bounds = match trait_item.node {
2225                 hir::TraitItemKind::Type(ref bounds, _) => bounds,
2226                 _ => return Vec::new().into_iter()
2227             };
2228
2229             let assoc_ty =
2230                 tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id),
2231                     self_trait_ref.substs);
2232
2233             let bounds = AstConv::compute_bounds(
2234                 &ItemCtxt::new(tcx, def_id),
2235                 assoc_ty,
2236                 bounds,
2237                 SizedByDefault::Yes,
2238                 trait_item.span,
2239             );
2240
2241             bounds.predicates(tcx, assoc_ty).into_iter()
2242         }))
2243     }
2244
2245     let mut predicates = predicates.predicates;
2246
2247     // Subtle: before we store the predicates into the tcx, we
2248     // sort them so that predicates like `T: Foo<Item=U>` come
2249     // before uses of `U`.  This avoids false ambiguity errors
2250     // in trait checking. See `setup_constraining_predicates`
2251     // for details.
2252     if let Node::Item(&Item {
2253         node: ItemKind::Impl(..),
2254         ..
2255     }) = node
2256     {
2257         let self_ty = tcx.type_of(def_id);
2258         let trait_ref = tcx.impl_trait_ref(def_id);
2259         cgp::setup_constraining_predicates(
2260             tcx,
2261             &mut predicates,
2262             trait_ref,
2263             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2264         );
2265     }
2266
2267     let result = tcx.arena.alloc(ty::GenericPredicates {
2268         parent: generics.parent,
2269         predicates,
2270     });
2271     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2272     result
2273 }
2274
2275 /// Converts a specific `GenericBound` from the AST into a set of
2276 /// predicates that apply to the self type. A vector is returned
2277 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2278 /// predicates) to one (`T: Foo`) to many (`T: Bar<X=i32>` adds `T: Bar`
2279 /// and `<T as Bar>::X == i32`).
2280 fn predicates_from_bound<'tcx>(
2281     astconv: &dyn AstConv<'tcx>,
2282     param_ty: Ty<'tcx>,
2283     bound: &'tcx hir::GenericBound,
2284 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2285     match *bound {
2286         hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2287             let mut bounds = Bounds::default();
2288             let (pred, _) = astconv.instantiate_poly_trait_ref(tr, param_ty, &mut bounds);
2289             iter::once((pred.to_predicate(), tr.span))
2290                 .chain(bounds.predicates(astconv.tcx(), param_ty))
2291                 .collect()
2292         }
2293         hir::GenericBound::Outlives(ref lifetime) => {
2294             let region = astconv.ast_region_to_region(lifetime, None);
2295             let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2296             vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2297         }
2298         hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2299     }
2300 }
2301
2302 fn compute_sig_of_foreign_fn_decl<'tcx>(
2303     tcx: TyCtxt<'tcx>,
2304     def_id: DefId,
2305     decl: &'tcx hir::FnDecl,
2306     abi: abi::Abi,
2307 ) -> ty::PolyFnSig<'tcx> {
2308     let unsafety = if abi == abi::Abi::RustIntrinsic {
2309         intrisic_operation_unsafety(&*tcx.item_name(def_id).as_str())
2310     } else {
2311         hir::Unsafety::Unsafe
2312     };
2313     let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl);
2314
2315     // Feature gate SIMD types in FFI, since I am not sure that the
2316     // ABIs are handled at all correctly. -huonw
2317     if abi != abi::Abi::RustIntrinsic
2318         && abi != abi::Abi::PlatformIntrinsic
2319         && !tcx.features().simd_ffi
2320     {
2321         let check = |ast_ty: &hir::Ty, ty: Ty<'_>| {
2322             if ty.is_simd() {
2323                 tcx.sess
2324                    .struct_span_err(
2325                        ast_ty.span,
2326                        &format!(
2327                            "use of SIMD type `{}` in FFI is highly experimental and \
2328                             may result in invalid code",
2329                            tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2330                        ),
2331                    )
2332                    .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2333                    .emit();
2334             }
2335         };
2336         for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2337             check(&input, ty)
2338         }
2339         if let hir::Return(ref ty) = decl.output {
2340             check(&ty, *fty.output().skip_binder())
2341         }
2342     }
2343
2344     fty
2345 }
2346
2347 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2348     match tcx.hir().get_if_local(def_id) {
2349         Some(Node::ForeignItem(..)) => true,
2350         Some(_) => false,
2351         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2352     }
2353 }
2354
2355 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2356     match tcx.hir().get_if_local(def_id) {
2357         Some(Node::Item(&hir::Item {
2358             node: hir::ItemKind::Static(_, mutbl, _), ..
2359         })) |
2360         Some(Node::ForeignItem( &hir::ForeignItem {
2361             node: hir::ForeignItemKind::Static(_, mutbl), ..
2362         })) => Some(mutbl),
2363         Some(_) => None,
2364         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2365     }
2366 }
2367
2368 fn from_target_feature(
2369     tcx: TyCtxt<'_>,
2370     id: DefId,
2371     attr: &ast::Attribute,
2372     whitelist: &FxHashMap<String, Option<Symbol>>,
2373     target_features: &mut Vec<Symbol>,
2374 ) {
2375     let list = match attr.meta_item_list() {
2376         Some(list) => list,
2377         None => return,
2378     };
2379     let bad_item = |span| {
2380         let msg = "malformed `target_feature` attribute input";
2381         let code = "enable = \"..\"".to_owned();
2382         tcx.sess.struct_span_err(span, &msg)
2383             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2384             .emit();
2385     };
2386     let rust_features = tcx.features();
2387     for item in list {
2388         // Only `enable = ...` is accepted in the meta-item list.
2389         if !item.check_name(sym::enable) {
2390             bad_item(item.span());
2391             continue;
2392         }
2393
2394         // Must be of the form `enable = "..."` (a string).
2395         let value = match item.value_str() {
2396             Some(value) => value,
2397             None => {
2398                 bad_item(item.span());
2399                 continue;
2400             }
2401         };
2402
2403         // We allow comma separation to enable multiple features.
2404         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2405             // Only allow whitelisted features per platform.
2406             let feature_gate = match whitelist.get(feature) {
2407                 Some(g) => g,
2408                 None => {
2409                     let msg = format!(
2410                         "the feature named `{}` is not valid for this target",
2411                         feature
2412                     );
2413                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2414                     err.span_label(
2415                         item.span(),
2416                         format!("`{}` is not valid for this target", feature),
2417                     );
2418                     if feature.starts_with("+") {
2419                         let valid = whitelist.contains_key(&feature[1..]);
2420                         if valid {
2421                             err.help("consider removing the leading `+` in the feature name");
2422                         }
2423                     }
2424                     err.emit();
2425                     return None;
2426                 }
2427             };
2428
2429             // Only allow features whose feature gates have been enabled.
2430             let allowed = match feature_gate.as_ref().map(|s| *s) {
2431                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2432                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2433                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2434                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2435                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2436                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2437                 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2438                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2439                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2440                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2441                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2442                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2443                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2444                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2445                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2446                 Some(name) => bug!("unknown target feature gate {}", name),
2447                 None => true,
2448             };
2449             if !allowed && id.is_local() {
2450                 feature_gate::emit_feature_err(
2451                     &tcx.sess.parse_sess,
2452                     feature_gate.unwrap(),
2453                     item.span(),
2454                     feature_gate::GateIssue::Language,
2455                     &format!("the target feature `{}` is currently unstable", feature),
2456                 );
2457             }
2458             Some(Symbol::intern(feature))
2459         }));
2460     }
2461 }
2462
2463 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2464     use rustc::mir::mono::Linkage::*;
2465
2466     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2467     // applicable to variable declarations and may not really make sense for
2468     // Rust code in the first place but whitelist them anyway and trust that
2469     // the user knows what s/he's doing. Who knows, unanticipated use cases
2470     // may pop up in the future.
2471     //
2472     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2473     // and don't have to be, LLVM treats them as no-ops.
2474     match name {
2475         "appending" => Appending,
2476         "available_externally" => AvailableExternally,
2477         "common" => Common,
2478         "extern_weak" => ExternalWeak,
2479         "external" => External,
2480         "internal" => Internal,
2481         "linkonce" => LinkOnceAny,
2482         "linkonce_odr" => LinkOnceODR,
2483         "private" => Private,
2484         "weak" => WeakAny,
2485         "weak_odr" => WeakODR,
2486         _ => {
2487             let span = tcx.hir().span_if_local(def_id);
2488             if let Some(span) = span {
2489                 tcx.sess.span_fatal(span, "invalid linkage specified")
2490             } else {
2491                 tcx.sess
2492                    .fatal(&format!("invalid linkage specified: {}", name))
2493             }
2494         }
2495     }
2496 }
2497
2498 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2499     let attrs = tcx.get_attrs(id);
2500
2501     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2502
2503     let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2504
2505     let mut inline_span = None;
2506     for attr in attrs.iter() {
2507         if attr.check_name(sym::cold) {
2508             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2509         } else if attr.check_name(sym::rustc_allocator) {
2510             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2511         } else if attr.check_name(sym::unwind) {
2512             codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2513         } else if attr.check_name(sym::ffi_returns_twice) {
2514             if tcx.is_foreign_item(id) {
2515                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2516             } else {
2517                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2518                 struct_span_err!(
2519                     tcx.sess,
2520                     attr.span,
2521                     E0724,
2522                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2523                 ).emit();
2524             }
2525         } else if attr.check_name(sym::rustc_allocator_nounwind) {
2526             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2527         } else if attr.check_name(sym::naked) {
2528             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2529         } else if attr.check_name(sym::no_mangle) {
2530             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2531         } else if attr.check_name(sym::rustc_std_internal_symbol) {
2532             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2533         } else if attr.check_name(sym::no_debug) {
2534             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2535         } else if attr.check_name(sym::used) {
2536             codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2537         } else if attr.check_name(sym::thread_local) {
2538             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2539         } else if attr.check_name(sym::export_name) {
2540             if let Some(s) = attr.value_str() {
2541                 if s.as_str().contains("\0") {
2542                     // `#[export_name = ...]` will be converted to a null-terminated string,
2543                     // so it may not contain any null characters.
2544                     struct_span_err!(
2545                         tcx.sess,
2546                         attr.span,
2547                         E0648,
2548                         "`export_name` may not contain null characters"
2549                     ).emit();
2550                 }
2551                 codegen_fn_attrs.export_name = Some(s);
2552             }
2553         } else if attr.check_name(sym::target_feature) {
2554             if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2555                 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2556                 tcx.sess.struct_span_err(attr.span, msg)
2557                     .span_label(attr.span, "can only be applied to `unsafe` functions")
2558                     .span_label(tcx.def_span(id), "not an `unsafe` function")
2559                     .emit();
2560             }
2561             from_target_feature(
2562                 tcx,
2563                 id,
2564                 attr,
2565                 &whitelist,
2566                 &mut codegen_fn_attrs.target_features,
2567             );
2568         } else if attr.check_name(sym::linkage) {
2569             if let Some(val) = attr.value_str() {
2570                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2571             }
2572         } else if attr.check_name(sym::link_section) {
2573             if let Some(val) = attr.value_str() {
2574                 if val.as_str().bytes().any(|b| b == 0) {
2575                     let msg = format!(
2576                         "illegal null byte in link_section \
2577                          value: `{}`",
2578                         &val
2579                     );
2580                     tcx.sess.span_err(attr.span, &msg);
2581                 } else {
2582                     codegen_fn_attrs.link_section = Some(val);
2583                 }
2584             }
2585         } else if attr.check_name(sym::link_name) {
2586             codegen_fn_attrs.link_name = attr.value_str();
2587         }
2588     }
2589
2590     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2591         if attr.path != sym::inline {
2592             return ia;
2593         }
2594         match attr.meta().map(|i| i.node) {
2595             Some(MetaItemKind::Word) => {
2596                 mark_used(attr);
2597                 InlineAttr::Hint
2598             }
2599             Some(MetaItemKind::List(ref items)) => {
2600                 mark_used(attr);
2601                 inline_span = Some(attr.span);
2602                 if items.len() != 1 {
2603                     span_err!(
2604                         tcx.sess.diagnostic(),
2605                         attr.span,
2606                         E0534,
2607                         "expected one argument"
2608                     );
2609                     InlineAttr::None
2610                 } else if list_contains_name(&items[..], sym::always) {
2611                     InlineAttr::Always
2612                 } else if list_contains_name(&items[..], sym::never) {
2613                     InlineAttr::Never
2614                 } else {
2615                     span_err!(
2616                         tcx.sess.diagnostic(),
2617                         items[0].span(),
2618                         E0535,
2619                         "invalid argument"
2620                     );
2621
2622                     InlineAttr::None
2623                 }
2624             }
2625             Some(MetaItemKind::NameValue(_)) => ia,
2626             None => ia,
2627         }
2628     });
2629
2630     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2631         if attr.path != sym::optimize {
2632             return ia;
2633         }
2634         let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2635         match attr.meta().map(|i| i.node) {
2636             Some(MetaItemKind::Word) => {
2637                 err(attr.span, "expected one argument");
2638                 ia
2639             }
2640             Some(MetaItemKind::List(ref items)) => {
2641                 mark_used(attr);
2642                 inline_span = Some(attr.span);
2643                 if items.len() != 1 {
2644                     err(attr.span, "expected one argument");
2645                     OptimizeAttr::None
2646                 } else if list_contains_name(&items[..], sym::size) {
2647                     OptimizeAttr::Size
2648                 } else if list_contains_name(&items[..], sym::speed) {
2649                     OptimizeAttr::Speed
2650                 } else {
2651                     err(items[0].span(), "invalid argument");
2652                     OptimizeAttr::None
2653                 }
2654             }
2655             Some(MetaItemKind::NameValue(_)) => ia,
2656             None => ia,
2657         }
2658     });
2659
2660     // If a function uses #[target_feature] it can't be inlined into general
2661     // purpose functions as they wouldn't have the right target features
2662     // enabled. For that reason we also forbid #[inline(always)] as it can't be
2663     // respected.
2664     if codegen_fn_attrs.target_features.len() > 0 {
2665         if codegen_fn_attrs.inline == InlineAttr::Always {
2666             if let Some(span) = inline_span {
2667                 tcx.sess.span_err(
2668                     span,
2669                     "cannot use `#[inline(always)]` with \
2670                      `#[target_feature]`",
2671                 );
2672             }
2673         }
2674     }
2675
2676     // Weak lang items have the same semantics as "std internal" symbols in the
2677     // sense that they're preserved through all our LTO passes and only
2678     // strippable by the linker.
2679     //
2680     // Additionally weak lang items have predetermined symbol names.
2681     if tcx.is_weak_lang_item(id) {
2682         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2683     }
2684     if let Some(name) = weak_lang_items::link_name(&attrs) {
2685         codegen_fn_attrs.export_name = Some(name);
2686         codegen_fn_attrs.link_name = Some(name);
2687     }
2688
2689     // Internal symbols to the standard library all have no_mangle semantics in
2690     // that they have defined symbol names present in the function name. This
2691     // also applies to weak symbols where they all have known symbol names.
2692     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2693         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2694     }
2695
2696     codegen_fn_attrs
2697 }