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