1 use rustc_data_structures::fx::FxIndexSet;
3 use rustc_hir::def_id::DefId;
4 use rustc_middle::ty::subst::Subst;
5 use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
6 use rustc_trait_selection::traits;
8 fn sized_constraint_for_ty<'tcx>(
10 adtdef: ty::AdtDef<'tcx>,
13 use rustc_type_ir::sty::TyKind::*;
15 let result = match ty.kind() {
16 Bool | Char | Int(..) | Uint(..) | Float(..) | RawPtr(..) | Ref(..) | FnDef(..)
17 | FnPtr(_) | Array(..) | Closure(..) | Generator(..) | Never => vec![],
19 Str | Dynamic(..) | Slice(_) | Foreign(..) | Error(_) | GeneratorWitness(..) => {
20 // these are never sized - return the target type
24 Tuple(ref tys) => match tys.last() {
26 Some(&ty) => sized_constraint_for_ty(tcx, adtdef, ty),
31 let adt_tys = adt.sized_constraint(tcx);
32 debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
36 .map(|ty| adt_tys.rebind(*ty).subst(tcx, substs))
37 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
41 Projection(..) | Opaque(..) => {
42 // must calculate explicitly.
43 // FIXME: consider special-casing always-Sized projections
48 // perf hack: if there is a `T: Sized` bound, then
49 // we know that `T` is Sized and do not need to check
52 let Some(sized_trait) = tcx.lang_items().sized_trait() else { return vec![ty] };
53 let sized_predicate = ty::Binder::dummy(ty::TraitRef {
55 substs: tcx.mk_substs_trait(ty, &[]),
59 let predicates = tcx.predicates_of(adtdef.did()).predicates;
60 if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
63 Placeholder(..) | Bound(..) | Infer(..) => {
64 bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
67 debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
71 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
72 match tcx.hir().get_by_def_id(def_id.expect_local()) {
73 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
74 hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
75 | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
77 bug!("`impl_defaultness` called on {:?}", node);
82 /// Calculates the `Sized` constraint.
84 /// In fact, there are only a few options for the types in the constraint:
85 /// - an obviously-unsized type
86 /// - a type parameter or projection whose Sizedness can't be known
87 /// - a tuple of type parameters or projections, if there are multiple
89 /// - an Error, if a type contained itself. The representability
90 /// check should catch this case.
91 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AdtSizedConstraint<'_> {
92 let def = tcx.adt_def(def_id);
94 let result = tcx.mk_type_list(
97 .flat_map(|v| v.fields.last())
98 .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did))),
101 debug!("adt_sized_constraint: {:?} => {:?}", def, result);
103 ty::AdtSizedConstraint(result)
106 /// See `ParamEnv` struct definition for details.
107 #[instrument(level = "debug", skip(tcx))]
108 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
109 // The param_env of an impl Trait type is its defining function's param_env
110 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
111 return param_env(tcx, parent.to_def_id());
113 // Compute the bounds on Self and the type parameters.
115 let ty::InstantiatedPredicates { mut predicates, .. } =
116 tcx.predicates_of(def_id).instantiate_identity(tcx);
118 // Finally, we have to normalize the bounds in the environment, in
119 // case they contain any associated type projections. This process
120 // can yield errors if the put in illegal associated types, like
121 // `<i32 as Foo>::Bar` where `i32` does not implement `Foo`. We
122 // report these errors right here; this doesn't actually feel
123 // right to me, because constructing the environment feels like a
124 // kind of an "idempotent" action, but I'm not sure where would be
125 // a better place. In practice, we construct environments for
126 // every fn once during type checking, and we'll abort if there
127 // are any errors at that point, so outside of type inference you can be
128 // sure that this will succeed without errors anyway.
130 if tcx.sess.opts.unstable_opts.chalk {
131 let environment = well_formed_types_in_env(tcx, def_id);
132 predicates.extend(environment);
135 let local_did = def_id.as_local();
136 let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
138 let constness = match hir_id {
139 Some(hir_id) => match tcx.hir().get(hir_id) {
140 hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
141 if tcx.is_const_default_method(def_id) =>
143 hir::Constness::Const
146 hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
147 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
148 | hir::Node::TraitItem(hir::TraitItem {
149 kind: hir::TraitItemKind::Const(..), ..
151 | hir::Node::AnonConst(_)
152 | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
153 | hir::Node::ImplItem(hir::ImplItem {
155 hir::ImplItemKind::Fn(
157 header: hir::FnHeader { constness: hir::Constness::Const, .. },
163 }) => hir::Constness::Const,
165 hir::Node::ImplItem(hir::ImplItem {
166 kind: hir::ImplItemKind::TyAlias(..) | hir::ImplItemKind::Fn(..),
169 let parent_hir_id = tcx.hir().get_parent_node(hir_id);
170 match tcx.hir().get(parent_hir_id) {
171 hir::Node::Item(hir::Item {
172 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
176 tcx.def_span(parent_hir_id.owner),
177 "impl item's parent node is not an impl",
182 hir::Node::Item(hir::Item {
184 hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
187 | hir::Node::TraitItem(hir::TraitItem {
189 hir::TraitItemKind::Fn(
190 hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
195 | hir::Node::Item(hir::Item {
196 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
200 _ => hir::Constness::NotConst,
202 None => hir::Constness::NotConst,
205 let unnormalized_env = ty::ParamEnv::new(
206 tcx.intern_predicates(&predicates),
207 traits::Reveal::UserFacing,
212 local_did.and_then(|id| tcx.hir().maybe_body_owned_by(id).map(|body| body.hir_id));
213 let body_id = match body_id {
215 None if hir_id.is_some() => hir_id.unwrap(),
216 _ => hir::CRATE_HIR_ID,
219 let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
220 traits::normalize_param_env_or_error(tcx, unnormalized_env, cause)
223 /// Elaborate the environment.
225 /// Collect a list of `Predicate`'s used for building the `ParamEnv`. Adds `TypeWellFormedFromEnv`'s
226 /// that are assumed to be well-formed (because they come from the environment).
228 /// Used only in chalk mode.
229 fn well_formed_types_in_env<'tcx>(
232 ) -> &'tcx ty::List<Predicate<'tcx>> {
233 use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
234 use rustc_middle::ty::subst::GenericArgKind;
236 debug!("environment(def_id = {:?})", def_id);
238 // The environment of an impl Trait type is its defining function's environment.
239 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
240 return well_formed_types_in_env(tcx, parent.to_def_id());
243 // Compute the bounds on `Self` and the type parameters.
244 let ty::InstantiatedPredicates { predicates, .. } =
245 tcx.predicates_of(def_id).instantiate_identity(tcx);
247 let clauses = predicates.into_iter();
249 if !def_id.is_local() {
250 return ty::List::empty();
252 let node = tcx.hir().get_by_def_id(def_id.expect_local());
261 let node_kind = match node {
262 Node::TraitItem(item) => match item.kind {
263 TraitItemKind::Fn(..) => NodeKind::Fn,
264 _ => NodeKind::Other,
267 Node::ImplItem(item) => match item.kind {
268 ImplItemKind::Fn(..) => NodeKind::Fn,
269 _ => NodeKind::Other,
272 Node::Item(item) => match item.kind {
273 ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => NodeKind::TraitImpl,
274 ItemKind::Impl(hir::Impl { of_trait: None, .. }) => NodeKind::InherentImpl,
275 ItemKind::Fn(..) => NodeKind::Fn,
276 _ => NodeKind::Other,
279 Node::ForeignItem(item) => match item.kind {
280 ForeignItemKind::Fn(..) => NodeKind::Fn,
281 _ => NodeKind::Other,
285 _ => NodeKind::Other,
288 // FIXME(eddyb) isn't the unordered nature of this a hazard?
289 let mut inputs = FxIndexSet::default();
292 // In a trait impl, we assume that the header trait ref and all its
293 // constituents are well-formed.
294 NodeKind::TraitImpl => {
295 let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl");
297 // FIXME(chalk): this has problems because of late-bound regions
298 //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
299 inputs.extend(trait_ref.substs.iter());
302 // In an inherent impl, we assume that the receiver type and all its
303 // constituents are well-formed.
304 NodeKind::InherentImpl => {
305 let self_ty = tcx.type_of(def_id);
306 inputs.extend(self_ty.walk());
309 // In an fn, we assume that the arguments and all their constituents are
312 let fn_sig = tcx.fn_sig(def_id);
313 let fn_sig = tcx.liberate_late_bound_regions(def_id, fn_sig);
315 inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
318 NodeKind::Other => (),
320 let input_clauses = inputs.into_iter().filter_map(|arg| {
322 GenericArgKind::Type(ty) => {
323 let binder = Binder::dummy(PredicateKind::TypeWellFormedFromEnv(ty));
324 Some(tcx.mk_predicate(binder))
327 // FIXME(eddyb) no WF conditions from lifetimes?
328 GenericArgKind::Lifetime(_) => None,
330 // FIXME(eddyb) support const generics in Chalk
331 GenericArgKind::Const(_) => None,
335 tcx.mk_predicates(clauses.chain(input_clauses))
338 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
339 tcx.param_env(def_id).with_reveal_all_normalized(tcx)
342 fn instance_def_size_estimate<'tcx>(
344 instance_def: ty::InstanceDef<'tcx>,
349 InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
350 let mir = tcx.instance_mir(instance_def);
351 mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
353 // Estimate the size of other compiler-generated shims to be 1.
358 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
360 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
361 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
362 debug!("issue33140_self_ty({:?})", def_id);
365 .impl_trait_ref(def_id)
366 .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id));
368 debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
370 let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
371 && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
373 // Check whether these impls would be ok for a marker trait.
375 debug!("issue33140_self_ty - not marker-like!");
379 // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
380 if trait_ref.substs.len() != 1 {
381 debug!("issue33140_self_ty - impl has substs!");
385 let predicates = tcx.predicates_of(def_id);
386 if predicates.parent.is_some() || !predicates.predicates.is_empty() {
387 debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
391 let self_ty = trait_ref.self_ty();
392 let self_ty_matches = match self_ty.kind() {
393 ty::Dynamic(ref data, re) if re.is_static() => data.principal().is_none(),
398 debug!("issue33140_self_ty - MATCHES!");
401 debug!("issue33140_self_ty - non-matching self type");
406 /// Check if a function is async.
407 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
408 let node = tcx.hir().get_by_def_id(def_id.expect_local());
409 if let Some(fn_kind) = node.fn_kind() { fn_kind.asyncness() } else { hir::IsAsync::NotAsync }
412 /// Don't call this directly: use ``tcx.conservative_is_privately_uninhabited`` instead.
413 #[instrument(level = "debug", skip(tcx))]
414 pub fn conservative_is_privately_uninhabited_raw<'tcx>(
416 param_env_and: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
418 let (param_env, ty) = param_env_and.into_parts();
421 debug!("ty::Never =>");
424 ty::Adt(def, _) if def.is_union() => {
425 debug!("ty::Adt(def, _) if def.is_union() =>");
426 // For now, `union`s are never considered uninhabited.
429 ty::Adt(def, substs) => {
430 debug!("ty::Adt(def, _) if def.is_not_union() =>");
431 // Any ADT is uninhabited if either:
432 // (a) It has no variants (i.e. an empty `enum`);
433 // (b) Each of its variants (a single one in the case of a `struct`) has at least
434 // one uninhabited field.
435 def.variants().iter().all(|var| {
436 var.fields.iter().any(|field| {
437 let ty = tcx.bound_type_of(field.did).subst(tcx, substs);
438 tcx.conservative_is_privately_uninhabited(param_env.and(ty))
442 ty::Tuple(fields) => {
443 debug!("ty::Tuple(..) =>");
444 fields.iter().any(|ty| tcx.conservative_is_privately_uninhabited(param_env.and(ty)))
446 ty::Array(ty, len) => {
447 debug!("ty::Array(ty, len) =>");
448 match len.try_eval_usize(tcx, param_env) {
449 Some(0) | None => false,
450 // If the array is definitely non-empty, it's uninhabited if
451 // the type of its elements is uninhabited.
452 Some(1..) => tcx.conservative_is_privately_uninhabited(param_env.and(*ty)),
456 debug!("ty::Ref(..) =>");
457 // References to uninitialised memory is valid for any type, including
458 // uninhabited types, in unsafe code, so we treat all references as
469 pub fn provide(providers: &mut ty::query::Providers) {
470 *providers = ty::query::Providers {
472 adt_sized_constraint,
474 param_env_reveal_all_normalized,
475 instance_def_size_estimate,
478 conservative_is_privately_uninhabited: conservative_is_privately_uninhabited_raw,