1 use rustc_data_structures::fx::FxIndexSet;
3 use rustc_hir::def_id::DefId;
4 use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
5 use rustc_trait_selection::traits;
7 fn sized_constraint_for_ty<'tcx>(
9 adtdef: ty::AdtDef<'tcx>,
12 use rustc_type_ir::sty::TyKind::*;
14 let result = match ty.kind() {
15 Bool | Char | Int(..) | Uint(..) | Float(..) | RawPtr(..) | Ref(..) | FnDef(..)
16 | FnPtr(_) | Array(..) | Closure(..) | Generator(..) | Never => vec![],
18 Str | Dynamic(..) | Slice(_) | Foreign(..) | Error(_) | GeneratorWitness(..) => {
19 // these are never sized - return the target type
23 Tuple(ref tys) => match tys.last() {
25 Some(&ty) => sized_constraint_for_ty(tcx, adtdef, ty),
30 let adt_tys = adt.sized_constraint(tcx);
31 debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
35 .map(|ty| adt_tys.rebind(*ty).subst(tcx, substs))
36 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
40 Projection(..) | Opaque(..) => {
41 // must calculate explicitly.
42 // FIXME: consider special-casing always-Sized projections
47 // perf hack: if there is a `T: Sized` bound, then
48 // we know that `T` is Sized and do not need to check
51 let Some(sized_trait) = tcx.lang_items().sized_trait() else { return vec![ty] };
52 let sized_predicate = ty::Binder::dummy(ty::TraitRef {
54 substs: tcx.mk_substs_trait(ty, &[]),
58 let predicates = tcx.predicates_of(adtdef.did()).predicates;
59 if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
62 Placeholder(..) | Bound(..) | Infer(..) => {
63 bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
66 debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
70 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
71 match tcx.hir().get_by_def_id(def_id.expect_local()) {
72 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
73 hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
74 | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
76 bug!("`impl_defaultness` called on {:?}", node);
81 /// Calculates the `Sized` constraint.
83 /// In fact, there are only a few options for the types in the constraint:
84 /// - an obviously-unsized type
85 /// - a type parameter or projection whose Sizedness can't be known
86 /// - a tuple of type parameters or projections, if there are multiple
88 /// - an Error, if a type is infinitely sized
89 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
90 if let Some(def_id) = def_id.as_local() {
91 if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
92 return tcx.intern_type_list(&[tcx.ty_error()]);
95 let def = tcx.adt_def(def_id);
97 let result = tcx.mk_type_list(
100 .flat_map(|v| v.fields.last())
101 .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did))),
104 debug!("adt_sized_constraint: {:?} => {:?}", def, result);
109 /// See `ParamEnv` struct definition for details.
110 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
111 // The param_env of an impl Trait type is its defining function's param_env
112 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
113 return param_env(tcx, parent.to_def_id());
115 // Compute the bounds on Self and the type parameters.
117 let ty::InstantiatedPredicates { mut predicates, .. } =
118 tcx.predicates_of(def_id).instantiate_identity(tcx);
120 // Finally, we have to normalize the bounds in the environment, in
121 // case they contain any associated type projections. This process
122 // can yield errors if the put in illegal associated types, like
123 // `<i32 as Foo>::Bar` where `i32` does not implement `Foo`. We
124 // report these errors right here; this doesn't actually feel
125 // right to me, because constructing the environment feels like a
126 // kind of an "idempotent" action, but I'm not sure where would be
127 // a better place. In practice, we construct environments for
128 // every fn once during type checking, and we'll abort if there
129 // are any errors at that point, so outside of type inference you can be
130 // sure that this will succeed without errors anyway.
132 if tcx.sess.opts.unstable_opts.chalk {
133 let environment = well_formed_types_in_env(tcx, def_id);
134 predicates.extend(environment);
137 let local_did = def_id.as_local();
138 let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
140 let unnormalized_env = ty::ParamEnv::new(
141 tcx.intern_predicates(&predicates),
142 traits::Reveal::UserFacing,
143 tcx.constness(def_id),
147 local_did.and_then(|id| tcx.hir().maybe_body_owned_by(id).map(|body| body.hir_id));
148 let body_id = match body_id {
150 None if hir_id.is_some() => hir_id.unwrap(),
151 _ => hir::CRATE_HIR_ID,
154 let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
155 traits::normalize_param_env_or_error(tcx, unnormalized_env, cause)
158 /// Elaborate the environment.
160 /// Collect a list of `Predicate`'s used for building the `ParamEnv`. Adds `TypeWellFormedFromEnv`'s
161 /// that are assumed to be well-formed (because they come from the environment).
163 /// Used only in chalk mode.
164 fn well_formed_types_in_env<'tcx>(
167 ) -> &'tcx ty::List<Predicate<'tcx>> {
168 use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
169 use rustc_middle::ty::subst::GenericArgKind;
171 debug!("environment(def_id = {:?})", def_id);
173 // The environment of an impl Trait type is its defining function's environment.
174 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
175 return well_formed_types_in_env(tcx, parent.to_def_id());
178 // Compute the bounds on `Self` and the type parameters.
179 let ty::InstantiatedPredicates { predicates, .. } =
180 tcx.predicates_of(def_id).instantiate_identity(tcx);
182 let clauses = predicates.into_iter();
184 if !def_id.is_local() {
185 return ty::List::empty();
187 let node = tcx.hir().get_by_def_id(def_id.expect_local());
196 let node_kind = match node {
197 Node::TraitItem(item) => match item.kind {
198 TraitItemKind::Fn(..) => NodeKind::Fn,
199 _ => NodeKind::Other,
202 Node::ImplItem(item) => match item.kind {
203 ImplItemKind::Fn(..) => NodeKind::Fn,
204 _ => NodeKind::Other,
207 Node::Item(item) => match item.kind {
208 ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => NodeKind::TraitImpl,
209 ItemKind::Impl(hir::Impl { of_trait: None, .. }) => NodeKind::InherentImpl,
210 ItemKind::Fn(..) => NodeKind::Fn,
211 _ => NodeKind::Other,
214 Node::ForeignItem(item) => match item.kind {
215 ForeignItemKind::Fn(..) => NodeKind::Fn,
216 _ => NodeKind::Other,
220 _ => NodeKind::Other,
223 // FIXME(eddyb) isn't the unordered nature of this a hazard?
224 let mut inputs = FxIndexSet::default();
227 // In a trait impl, we assume that the header trait ref and all its
228 // constituents are well-formed.
229 NodeKind::TraitImpl => {
230 let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl");
232 // FIXME(chalk): this has problems because of late-bound regions
233 //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
234 inputs.extend(trait_ref.substs.iter());
237 // In an inherent impl, we assume that the receiver type and all its
238 // constituents are well-formed.
239 NodeKind::InherentImpl => {
240 let self_ty = tcx.type_of(def_id);
241 inputs.extend(self_ty.walk());
244 // In an fn, we assume that the arguments and all their constituents are
247 let fn_sig = tcx.fn_sig(def_id);
248 let fn_sig = tcx.liberate_late_bound_regions(def_id, fn_sig);
250 inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
253 NodeKind::Other => (),
255 let input_clauses = inputs.into_iter().filter_map(|arg| {
257 GenericArgKind::Type(ty) => {
258 let binder = Binder::dummy(PredicateKind::TypeWellFormedFromEnv(ty));
259 Some(tcx.mk_predicate(binder))
262 // FIXME(eddyb) no WF conditions from lifetimes?
263 GenericArgKind::Lifetime(_) => None,
265 // FIXME(eddyb) support const generics in Chalk
266 GenericArgKind::Const(_) => None,
270 tcx.mk_predicates(clauses.chain(input_clauses))
273 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
274 tcx.param_env(def_id).with_reveal_all_normalized(tcx)
277 fn instance_def_size_estimate<'tcx>(
279 instance_def: ty::InstanceDef<'tcx>,
284 InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
285 let mir = tcx.instance_mir(instance_def);
286 mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
288 // Estimate the size of other compiler-generated shims to be 1.
293 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
295 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
296 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
297 debug!("issue33140_self_ty({:?})", def_id);
300 .impl_trait_ref(def_id)
301 .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id));
303 debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
305 let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
306 && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
308 // Check whether these impls would be ok for a marker trait.
310 debug!("issue33140_self_ty - not marker-like!");
314 // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
315 if trait_ref.substs.len() != 1 {
316 debug!("issue33140_self_ty - impl has substs!");
320 let predicates = tcx.predicates_of(def_id);
321 if predicates.parent.is_some() || !predicates.predicates.is_empty() {
322 debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
326 let self_ty = trait_ref.self_ty();
327 let self_ty_matches = match self_ty.kind() {
328 ty::Dynamic(ref data, re, _) if re.is_static() => data.principal().is_none(),
333 debug!("issue33140_self_ty - MATCHES!");
336 debug!("issue33140_self_ty - non-matching self type");
341 /// Check if a function is async.
342 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
343 let node = tcx.hir().get_by_def_id(def_id.expect_local());
344 if let Some(fn_kind) = node.fn_kind() { fn_kind.asyncness() } else { hir::IsAsync::NotAsync }
347 /// Don't call this directly: use ``tcx.conservative_is_privately_uninhabited`` instead.
348 pub fn conservative_is_privately_uninhabited_raw<'tcx>(
350 param_env_and: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
352 let (param_env, ty) = param_env_and.into_parts();
355 debug!("ty::Never =>");
358 ty::Adt(def, _) if def.is_union() => {
359 debug!("ty::Adt(def, _) if def.is_union() =>");
360 // For now, `union`s are never considered uninhabited.
363 ty::Adt(def, substs) => {
364 debug!("ty::Adt(def, _) if def.is_not_union() =>");
365 // Any ADT is uninhabited if either:
366 // (a) It has no variants (i.e. an empty `enum`);
367 // (b) Each of its variants (a single one in the case of a `struct`) has at least
368 // one uninhabited field.
369 def.variants().iter().all(|var| {
370 var.fields.iter().any(|field| {
371 let ty = tcx.bound_type_of(field.did).subst(tcx, substs);
372 tcx.conservative_is_privately_uninhabited(param_env.and(ty))
376 ty::Tuple(fields) => {
377 debug!("ty::Tuple(..) =>");
378 fields.iter().any(|ty| tcx.conservative_is_privately_uninhabited(param_env.and(ty)))
380 ty::Array(ty, len) => {
381 debug!("ty::Array(ty, len) =>");
382 match len.try_eval_usize(tcx, param_env) {
383 Some(0) | None => false,
384 // If the array is definitely non-empty, it's uninhabited if
385 // the type of its elements is uninhabited.
386 Some(1..) => tcx.conservative_is_privately_uninhabited(param_env.and(*ty)),
390 debug!("ty::Ref(..) =>");
391 // References to uninitialised memory is valid for any type, including
392 // uninhabited types, in unsafe code, so we treat all references as
403 pub fn provide(providers: &mut ty::query::Providers) {
404 *providers = ty::query::Providers {
406 adt_sized_constraint,
408 param_env_reveal_all_normalized,
409 instance_def_size_estimate,
412 conservative_is_privately_uninhabited: conservative_is_privately_uninhabited_raw,