compiler/rustc_ty/src/ty.rs

   1 use rustc_data_structures::fx::FxIndexSet;
   2 use rustc_data_structures::svh::Svh;
   3 use rustc_hir as hir;
   4 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
   5 use rustc_middle::hir::map as hir_map;
   6 use rustc_middle::ty::subst::Subst;
   7 use rustc_middle::ty::{
   8     self, Binder, Predicate, PredicateAtom, PredicateKind, ToPredicate, Ty, TyCtxt, WithConstness,
   9 };
  10 use rustc_session::CrateDisambiguator;
  11 use rustc_span::symbol::Symbol;
  12 use rustc_span::Span;
  13 use rustc_trait_selection::traits;
  14
  15 fn sized_constraint_for_ty<'tcx>(
  16     tcx: TyCtxt<'tcx>,
  17     adtdef: &ty::AdtDef,
  18     ty: Ty<'tcx>,
  19 ) -> Vec<Ty<'tcx>> {
  20     use ty::TyKind::*;
  21
  22     let result = match ty.kind() {
  23         Bool | Char | Int(..) | Uint(..) | Float(..) | RawPtr(..) | Ref(..) | FnDef(..)
  24         | FnPtr(_) | Array(..) | Closure(..) | Generator(..) | Never => vec![],
  25
  26         Str | Dynamic(..) | Slice(_) | Foreign(..) | Error(_) | GeneratorWitness(..) => {
  27             // these are never sized - return the target type
  28             vec![ty]
  29         }
  30
  31         Tuple(ref tys) => match tys.last() {
  32             None => vec![],
  33             Some(ty) => sized_constraint_for_ty(tcx, adtdef, ty.expect_ty()),
  34         },
  35
  36         Adt(adt, substs) => {
  37             // recursive case
  38             let adt_tys = adt.sized_constraint(tcx);
  39             debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
  40             adt_tys
  41                 .iter()
  42                 .map(|ty| ty.subst(tcx, substs))
  43                 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
  44                 .collect()
  45         }
  46
  47         Projection(..) | Opaque(..) => {
  48             // must calculate explicitly.
  49             // FIXME: consider special-casing always-Sized projections
  50             vec![ty]
  51         }
  52
  53         Param(..) => {
  54             // perf hack: if there is a `T: Sized` bound, then
  55             // we know that `T` is Sized and do not need to check
  56             // it on the impl.
  57
  58             let sized_trait = match tcx.lang_items().sized_trait() {
  59                 Some(x) => x,
  60                 _ => return vec![ty],
  61             };
  62             let sized_predicate = ty::Binder::dummy(ty::TraitRef {
  63                 def_id: sized_trait,
  64                 substs: tcx.mk_substs_trait(ty, &[]),
  65             })
  66             .without_const()
  67             .to_predicate(tcx);
  68             let predicates = tcx.predicates_of(adtdef.did).predicates;
  69             if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
  70         }
  71
  72         Placeholder(..) | Bound(..) | Infer(..) => {
  73             bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
  74         }
  75     };
  76     debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
  77     result
  78 }
  79
  80 fn associated_item_from_trait_item_ref(
  81     tcx: TyCtxt<'_>,
  82     parent_def_id: LocalDefId,
  83     trait_item_ref: &hir::TraitItemRef,
  84 ) -> ty::AssocItem {
  85     let def_id = tcx.hir().local_def_id(trait_item_ref.id.hir_id);
  86     let (kind, has_self) = match trait_item_ref.kind {
  87         hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
  88         hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
  89         hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
  90     };
  91
  92     ty::AssocItem {
  93         ident: trait_item_ref.ident,
  94         kind,
  95         vis: tcx.visibility(def_id),
  96         defaultness: trait_item_ref.defaultness,
  97         def_id: def_id.to_def_id(),
  98         container: ty::TraitContainer(parent_def_id.to_def_id()),
  99         fn_has_self_parameter: has_self,
 100     }
 101 }
 102
 103 fn associated_item_from_impl_item_ref(
 104     tcx: TyCtxt<'_>,
 105     parent_def_id: LocalDefId,
 106     impl_item_ref: &hir::ImplItemRef<'_>,
 107 ) -> ty::AssocItem {
 108     let def_id = tcx.hir().local_def_id(impl_item_ref.id.hir_id);
 109     let (kind, has_self) = match impl_item_ref.kind {
 110         hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
 111         hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
 112         hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
 113     };
 114
 115     ty::AssocItem {
 116         ident: impl_item_ref.ident,
 117         kind,
 118         vis: tcx.visibility(def_id),
 119         defaultness: impl_item_ref.defaultness,
 120         def_id: def_id.to_def_id(),
 121         container: ty::ImplContainer(parent_def_id.to_def_id()),
 122         fn_has_self_parameter: has_self,
 123     }
 124 }
 125
 126 fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
 127     let id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 128     let parent_id = tcx.hir().get_parent_item(id);
 129     let parent_def_id = tcx.hir().local_def_id(parent_id);
 130     let parent_item = tcx.hir().expect_item(parent_id);
 131     match parent_item.kind {
 132         hir::ItemKind::Impl { ref items, .. } => {
 133             if let Some(impl_item_ref) = items.iter().find(|i| i.id.hir_id == id) {
 134                 let assoc_item =
 135                     associated_item_from_impl_item_ref(tcx, parent_def_id, impl_item_ref);
 136                 debug_assert_eq!(assoc_item.def_id, def_id);
 137                 return assoc_item;
 138             }
 139         }
 140
 141         hir::ItemKind::Trait(.., ref trait_item_refs) => {
 142             if let Some(trait_item_ref) = trait_item_refs.iter().find(|i| i.id.hir_id == id) {
 143                 let assoc_item =
 144                     associated_item_from_trait_item_ref(tcx, parent_def_id, trait_item_ref);
 145                 debug_assert_eq!(assoc_item.def_id, def_id);
 146                 return assoc_item;
 147             }
 148         }
 149
 150         _ => {}
 151     }
 152
 153     span_bug!(
 154         parent_item.span,
 155         "unexpected parent of trait or impl item or item not found: {:?}",
 156         parent_item.kind
 157     )
 158 }
 159
 160 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
 161     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 162     let item = tcx.hir().expect_item(hir_id);
 163     if let hir::ItemKind::Impl { defaultness, .. } = item.kind {
 164         defaultness
 165     } else {
 166         bug!("`impl_defaultness` called on {:?}", item);
 167     }
 168 }
 169
 170 /// Calculates the `Sized` constraint.
 171 ///
 172 /// In fact, there are only a few options for the types in the constraint:
 173 ///     - an obviously-unsized type
 174 ///     - a type parameter or projection whose Sizedness can't be known
 175 ///     - a tuple of type parameters or projections, if there are multiple
 176 ///       such.
 177 ///     - a Error, if a type contained itself. The representability
 178 ///       check should catch this case.
 179 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AdtSizedConstraint<'_> {
 180     let def = tcx.adt_def(def_id);
 181
 182     let result = tcx.mk_type_list(
 183         def.variants
 184             .iter()
 185             .flat_map(|v| v.fields.last())
 186             .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did))),
 187     );
 188
 189     debug!("adt_sized_constraint: {:?} => {:?}", def, result);
 190
 191     ty::AdtSizedConstraint(result)
 192 }
 193
 194 fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
 195     let id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 196     let item = tcx.hir().expect_item(id);
 197     match item.kind {
 198         hir::ItemKind::Trait(.., ref trait_item_refs) => tcx.arena.alloc_from_iter(
 199             trait_item_refs
 200                 .iter()
 201                 .map(|trait_item_ref| trait_item_ref.id)
 202                 .map(|id| tcx.hir().local_def_id(id.hir_id).to_def_id()),
 203         ),
 204         hir::ItemKind::Impl { ref items, .. } => tcx.arena.alloc_from_iter(
 205             items
 206                 .iter()
 207                 .map(|impl_item_ref| impl_item_ref.id)
 208                 .map(|id| tcx.hir().local_def_id(id.hir_id).to_def_id()),
 209         ),
 210         hir::ItemKind::TraitAlias(..) => &[],
 211         _ => span_bug!(item.span, "associated_item_def_ids: not impl or trait"),
 212     }
 213 }
 214
 215 fn associated_items(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssociatedItems<'_> {
 216     let items = tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did));
 217     ty::AssociatedItems::new(items)
 218 }
 219
 220 fn def_span(tcx: TyCtxt<'_>, def_id: DefId) -> Span {
 221     tcx.hir().span_if_local(def_id).unwrap()
 222 }
 223
 224 /// If the given `DefId` describes an item belonging to a trait,
 225 /// returns the `DefId` of the trait that the trait item belongs to;
 226 /// otherwise, returns `None`.
 227 fn trait_of_item(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
 228     tcx.opt_associated_item(def_id).and_then(|associated_item| match associated_item.container {
 229         ty::TraitContainer(def_id) => Some(def_id),
 230         ty::ImplContainer(_) => None,
 231     })
 232 }
 233
 234 /// See `ParamEnv` struct definition for details.
 235 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
 236     // The param_env of an impl Trait type is its defining function's param_env
 237     if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
 238         return param_env(tcx, parent);
 239     }
 240     // Compute the bounds on Self and the type parameters.
 241
 242     let ty::InstantiatedPredicates { mut predicates, .. } =
 243         tcx.predicates_of(def_id).instantiate_identity(tcx);
 244
 245     // Finally, we have to normalize the bounds in the environment, in
 246     // case they contain any associated type projections. This process
 247     // can yield errors if the put in illegal associated types, like
 248     // `<i32 as Foo>::Bar` where `i32` does not implement `Foo`. We
 249     // report these errors right here; this doesn't actually feel
 250     // right to me, because constructing the environment feels like a
 251     // kind of a "idempotent" action, but I'm not sure where would be
 252     // a better place. In practice, we construct environments for
 253     // every fn once during type checking, and we'll abort if there
 254     // are any errors at that point, so after type checking you can be
 255     // sure that this will succeed without errors anyway.
 256
 257     if tcx.sess.opts.debugging_opts.chalk {
 258         let environment = well_formed_types_in_env(tcx, def_id);
 259         predicates.extend(environment);
 260     }
 261
 262     let unnormalized_env =
 263         ty::ParamEnv::new(tcx.intern_predicates(&predicates), traits::Reveal::UserFacing);
 264
 265     let body_id = def_id
 266         .as_local()
 267         .map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
 268         .map_or(hir::CRATE_HIR_ID, |id| {
 269             tcx.hir().maybe_body_owned_by(id).map_or(id, |body| body.hir_id)
 270         });
 271     let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
 272     traits::normalize_param_env_or_error(tcx, def_id, unnormalized_env, cause)
 273 }
 274
 275 /// Elaborate the environment.
 276 ///
 277 /// Collect a list of `Predicate`'s used for building the `ParamEnv`. Adds `TypeWellFormedFromEnv`'s
 278 /// that are assumed to be well-formed (because they come from the environment).
 279 ///
 280 /// Used only in chalk mode.
 281 fn well_formed_types_in_env<'tcx>(
 282     tcx: TyCtxt<'tcx>,
 283     def_id: DefId,
 284 ) -> &'tcx ty::List<Predicate<'tcx>> {
 285     use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
 286     use rustc_middle::ty::subst::GenericArgKind;
 287
 288     debug!("environment(def_id = {:?})", def_id);
 289
 290     // The environment of an impl Trait type is its defining function's environment.
 291     if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
 292         return well_formed_types_in_env(tcx, parent);
 293     }
 294
 295     // Compute the bounds on `Self` and the type parameters.
 296     let ty::InstantiatedPredicates { predicates, .. } =
 297         tcx.predicates_of(def_id).instantiate_identity(tcx);
 298
 299     let clauses = predicates.into_iter();
 300
 301     if !def_id.is_local() {
 302         return ty::List::empty();
 303     }
 304     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 305     let node = tcx.hir().get(hir_id);
 306
 307     enum NodeKind {
 308         TraitImpl,
 309         InherentImpl,
 310         Fn,
 311         Other,
 312     };
 313
 314     let node_kind = match node {
 315         Node::TraitItem(item) => match item.kind {
 316             TraitItemKind::Fn(..) => NodeKind::Fn,
 317             _ => NodeKind::Other,
 318         },
 319
 320         Node::ImplItem(item) => match item.kind {
 321             ImplItemKind::Fn(..) => NodeKind::Fn,
 322             _ => NodeKind::Other,
 323         },
 324
 325         Node::Item(item) => match item.kind {
 326             ItemKind::Impl { of_trait: Some(_), .. } => NodeKind::TraitImpl,
 327             ItemKind::Impl { of_trait: None, .. } => NodeKind::InherentImpl,
 328             ItemKind::Fn(..) => NodeKind::Fn,
 329             _ => NodeKind::Other,
 330         },
 331
 332         Node::ForeignItem(item) => match item.kind {
 333             ForeignItemKind::Fn(..) => NodeKind::Fn,
 334             _ => NodeKind::Other,
 335         },
 336
 337         // FIXME: closures?
 338         _ => NodeKind::Other,
 339     };
 340
 341     // FIXME(eddyb) isn't the unordered nature of this a hazard?
 342     let mut inputs = FxIndexSet::default();
 343
 344     match node_kind {
 345         // In a trait impl, we assume that the header trait ref and all its
 346         // constituents are well-formed.
 347         NodeKind::TraitImpl => {
 348             let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl");
 349
 350             // FIXME(chalk): this has problems because of late-bound regions
 351             //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
 352             inputs.extend(trait_ref.substs.iter());
 353         }
 354
 355         // In an inherent impl, we assume that the receiver type and all its
 356         // constituents are well-formed.
 357         NodeKind::InherentImpl => {
 358             let self_ty = tcx.type_of(def_id);
 359             inputs.extend(self_ty.walk());
 360         }
 361
 362         // In an fn, we assume that the arguments and all their constituents are
 363         // well-formed.
 364         NodeKind::Fn => {
 365             let fn_sig = tcx.fn_sig(def_id);
 366             let fn_sig = tcx.liberate_late_bound_regions(def_id, &fn_sig);
 367
 368             inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
 369         }
 370
 371         NodeKind::Other => (),
 372     }
 373     let input_clauses = inputs.into_iter().filter_map(|arg| {
 374         match arg.unpack() {
 375             GenericArgKind::Type(ty) => {
 376                 let binder = Binder::dummy(PredicateAtom::TypeWellFormedFromEnv(ty));
 377                 Some(tcx.mk_predicate(PredicateKind::ForAll(binder)))
 378             }
 379
 380             // FIXME(eddyb) no WF conditions from lifetimes?
 381             GenericArgKind::Lifetime(_) => None,
 382
 383             // FIXME(eddyb) support const generics in Chalk
 384             GenericArgKind::Const(_) => None,
 385         }
 386     });
 387
 388     tcx.mk_predicates(clauses.chain(input_clauses))
 389 }
 390
 391 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
 392     tcx.param_env(def_id).with_reveal_all_normalized(tcx)
 393 }
 394
 395 fn crate_disambiguator(tcx: TyCtxt<'_>, crate_num: CrateNum) -> CrateDisambiguator {
 396     assert_eq!(crate_num, LOCAL_CRATE);
 397     tcx.sess.local_crate_disambiguator()
 398 }
 399
 400 fn original_crate_name(tcx: TyCtxt<'_>, crate_num: CrateNum) -> Symbol {
 401     assert_eq!(crate_num, LOCAL_CRATE);
 402     tcx.crate_name
 403 }
 404
 405 fn crate_hash(tcx: TyCtxt<'_>, crate_num: CrateNum) -> Svh {
 406     tcx.index_hir(crate_num).crate_hash
 407 }
 408
 409 fn instance_def_size_estimate<'tcx>(
 410     tcx: TyCtxt<'tcx>,
 411     instance_def: ty::InstanceDef<'tcx>,
 412 ) -> usize {
 413     use ty::InstanceDef;
 414
 415     match instance_def {
 416         InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
 417             let mir = tcx.instance_mir(instance_def);
 418             mir.basic_blocks().iter().map(|bb| bb.statements.len()).sum()
 419         }
 420         // Estimate the size of other compiler-generated shims to be 1.
 421         _ => 1,
 422     }
 423 }
 424
 425 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
 426 ///
 427 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
 428 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
 429     debug!("issue33140_self_ty({:?})", def_id);
 430
 431     let trait_ref = tcx
 432         .impl_trait_ref(def_id)
 433         .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id));
 434
 435     debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
 436
 437     let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
 438         && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
 439
 440     // Check whether these impls would be ok for a marker trait.
 441     if !is_marker_like {
 442         debug!("issue33140_self_ty - not marker-like!");
 443         return None;
 444     }
 445
 446     // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
 447     if trait_ref.substs.len() != 1 {
 448         debug!("issue33140_self_ty - impl has substs!");
 449         return None;
 450     }
 451
 452     let predicates = tcx.predicates_of(def_id);
 453     if predicates.parent.is_some() || !predicates.predicates.is_empty() {
 454         debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
 455         return None;
 456     }
 457
 458     let self_ty = trait_ref.self_ty();
 459     let self_ty_matches = match self_ty.kind() {
 460         ty::Dynamic(ref data, ty::ReStatic) => data.principal().is_none(),
 461         _ => false,
 462     };
 463
 464     if self_ty_matches {
 465         debug!("issue33140_self_ty - MATCHES!");
 466         Some(self_ty)
 467     } else {
 468         debug!("issue33140_self_ty - non-matching self type");
 469         None
 470     }
 471 }
 472
 473 /// Check if a function is async.
 474 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
 475     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
 476
 477     let node = tcx.hir().get(hir_id);
 478
 479     let fn_like = hir_map::blocks::FnLikeNode::from_node(node).unwrap_or_else(|| {
 480         bug!("asyncness: expected fn-like node but got `{:?}`", def_id);
 481     });
 482
 483     fn_like.asyncness()
 484 }
 485
 486 pub fn provide(providers: &mut ty::query::Providers) {
 487     *providers = ty::query::Providers {
 488         asyncness,
 489         associated_item,
 490         associated_item_def_ids,
 491         associated_items,
 492         adt_sized_constraint,
 493         def_span,
 494         param_env,
 495         param_env_reveal_all_normalized,
 496         trait_of_item,
 497         crate_disambiguator,
 498         original_crate_name,
 499         crate_hash,
 500         instance_def_size_estimate,
 501         issue33140_self_ty,
 502         impl_defaultness,
 503         ..*providers
 504     };
 505 }