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))
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(tcx.mk_trait_ref(sized_trait, [ty]))
55 let predicates = tcx.predicates_of(adtdef.did()).predicates;
56 if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
59 Placeholder(..) | Bound(..) | Infer(..) => {
60 bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
63 debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
67 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
68 match tcx.hir().get_by_def_id(def_id.expect_local()) {
69 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
70 hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
71 | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
73 bug!("`impl_defaultness` called on {:?}", node);
78 /// Calculates the `Sized` constraint.
80 /// In fact, there are only a few options for the types in the constraint:
81 /// - an obviously-unsized type
82 /// - a type parameter or projection whose Sizedness can't be known
83 /// - a tuple of type parameters or projections, if there are multiple
85 /// - an Error, if a type is infinitely sized
86 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
87 if let Some(def_id) = def_id.as_local() {
88 if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
89 return tcx.intern_type_list(&[tcx.ty_error()]);
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);
106 /// See `ParamEnv` struct definition for details.
107 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
108 // Compute the bounds on Self and the type parameters.
109 let ty::InstantiatedPredicates { mut predicates, .. } =
110 tcx.predicates_of(def_id).instantiate_identity(tcx);
112 // Finally, we have to normalize the bounds in the environment, in
113 // case they contain any associated type projections. This process
114 // can yield errors if the put in illegal associated types, like
115 // `<i32 as Foo>::Bar` where `i32` does not implement `Foo`. We
116 // report these errors right here; this doesn't actually feel
117 // right to me, because constructing the environment feels like a
118 // kind of an "idempotent" action, but I'm not sure where would be
119 // a better place. In practice, we construct environments for
120 // every fn once during type checking, and we'll abort if there
121 // are any errors at that point, so outside of type inference you can be
122 // sure that this will succeed without errors anyway.
124 if tcx.sess.opts.unstable_opts.chalk {
125 let environment = well_formed_types_in_env(tcx, def_id);
126 predicates.extend(environment);
129 let local_did = def_id.as_local();
130 let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
132 // FIXME(consts): This is not exactly in line with the constness query.
133 let constness = match hir_id {
134 Some(hir_id) => match tcx.hir().get(hir_id) {
135 hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
136 if tcx.is_const_default_method(def_id) =>
138 hir::Constness::Const
141 hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
142 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
143 | hir::Node::TraitItem(hir::TraitItem {
144 kind: hir::TraitItemKind::Const(..), ..
146 | hir::Node::AnonConst(_)
147 | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
148 | hir::Node::ImplItem(hir::ImplItem {
150 hir::ImplItemKind::Fn(
152 header: hir::FnHeader { constness: hir::Constness::Const, .. },
158 }) => hir::Constness::Const,
160 hir::Node::ImplItem(hir::ImplItem {
161 kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
164 let parent_hir_id = tcx.hir().get_parent_node(hir_id);
165 match tcx.hir().get(parent_hir_id) {
166 hir::Node::Item(hir::Item {
167 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
171 tcx.def_span(parent_hir_id.owner),
172 "impl item's parent node is not an impl",
177 hir::Node::Item(hir::Item {
179 hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
182 | hir::Node::TraitItem(hir::TraitItem {
184 hir::TraitItemKind::Fn(
185 hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
190 | hir::Node::Item(hir::Item {
191 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
195 _ => hir::Constness::NotConst,
197 // FIXME(consts): It's suspicious that a param-env for a foreign item
198 // will always have NotConst param-env, though we don't typically use
199 // that param-env for anything meaningful right now, so it's likely
201 None => hir::Constness::NotConst,
204 let unnormalized_env = ty::ParamEnv::new(
205 tcx.intern_predicates(&predicates),
206 traits::Reveal::UserFacing,
211 local_did.and_then(|id| tcx.hir().maybe_body_owned_by(id).map(|body| body.hir_id));
212 let body_id = match body_id {
214 None if hir_id.is_some() => hir_id.unwrap(),
215 _ => hir::CRATE_HIR_ID,
218 let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
219 traits::normalize_param_env_or_error(tcx, unnormalized_env, cause)
222 /// Elaborate the environment.
224 /// Collect a list of `Predicate`'s used for building the `ParamEnv`. Adds `TypeWellFormedFromEnv`'s
225 /// that are assumed to be well-formed (because they come from the environment).
227 /// Used only in chalk mode.
228 fn well_formed_types_in_env<'tcx>(
231 ) -> &'tcx ty::List<Predicate<'tcx>> {
232 use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
233 use rustc_middle::ty::subst::GenericArgKind;
235 debug!("environment(def_id = {:?})", def_id);
237 // The environment of an impl Trait type is its defining function's environment.
238 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
239 return well_formed_types_in_env(tcx, parent.to_def_id());
242 // Compute the bounds on `Self` and the type parameters.
243 let ty::InstantiatedPredicates { predicates, .. } =
244 tcx.predicates_of(def_id).instantiate_identity(tcx);
246 let clauses = predicates.into_iter();
248 if !def_id.is_local() {
249 return ty::List::empty();
251 let node = tcx.hir().get_by_def_id(def_id.expect_local());
260 let node_kind = match node {
261 Node::TraitItem(item) => match item.kind {
262 TraitItemKind::Fn(..) => NodeKind::Fn,
263 _ => NodeKind::Other,
266 Node::ImplItem(item) => match item.kind {
267 ImplItemKind::Fn(..) => NodeKind::Fn,
268 _ => NodeKind::Other,
271 Node::Item(item) => match item.kind {
272 ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => NodeKind::TraitImpl,
273 ItemKind::Impl(hir::Impl { of_trait: None, .. }) => NodeKind::InherentImpl,
274 ItemKind::Fn(..) => NodeKind::Fn,
275 _ => NodeKind::Other,
278 Node::ForeignItem(item) => match item.kind {
279 ForeignItemKind::Fn(..) => NodeKind::Fn,
280 _ => NodeKind::Other,
284 _ => NodeKind::Other,
287 // FIXME(eddyb) isn't the unordered nature of this a hazard?
288 let mut inputs = FxIndexSet::default();
291 // In a trait impl, we assume that the header trait ref and all its
292 // constituents are well-formed.
293 NodeKind::TraitImpl => {
294 let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl");
296 // FIXME(chalk): this has problems because of late-bound regions
297 //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
298 inputs.extend(trait_ref.substs.iter());
301 // In an inherent impl, we assume that the receiver type and all its
302 // constituents are well-formed.
303 NodeKind::InherentImpl => {
304 let self_ty = tcx.type_of(def_id);
305 inputs.extend(self_ty.walk());
308 // In an fn, we assume that the arguments and all their constituents are
311 let fn_sig = tcx.fn_sig(def_id);
312 let fn_sig = tcx.liberate_late_bound_regions(def_id, fn_sig);
314 inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
317 NodeKind::Other => (),
319 let input_clauses = inputs.into_iter().filter_map(|arg| {
321 GenericArgKind::Type(ty) => {
322 let binder = Binder::dummy(PredicateKind::TypeWellFormedFromEnv(ty));
323 Some(tcx.mk_predicate(binder))
326 // FIXME(eddyb) no WF conditions from lifetimes?
327 GenericArgKind::Lifetime(_) => None,
329 // FIXME(eddyb) support const generics in Chalk
330 GenericArgKind::Const(_) => None,
334 tcx.mk_predicates(clauses.chain(input_clauses))
337 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
338 tcx.param_env(def_id).with_reveal_all_normalized(tcx)
341 fn instance_def_size_estimate<'tcx>(
343 instance_def: ty::InstanceDef<'tcx>,
348 InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
349 let mir = tcx.instance_mir(instance_def);
350 mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
352 // Estimate the size of other compiler-generated shims to be 1.
357 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
359 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
360 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
361 debug!("issue33140_self_ty({:?})", def_id);
364 .impl_trait_ref(def_id)
365 .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id));
367 debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
369 let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
370 && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
372 // Check whether these impls would be ok for a marker trait.
374 debug!("issue33140_self_ty - not marker-like!");
378 // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
379 if trait_ref.substs.len() != 1 {
380 debug!("issue33140_self_ty - impl has substs!");
384 let predicates = tcx.predicates_of(def_id);
385 if predicates.parent.is_some() || !predicates.predicates.is_empty() {
386 debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
390 let self_ty = trait_ref.self_ty();
391 let self_ty_matches = match self_ty.kind() {
392 ty::Dynamic(ref data, re, _) if re.is_static() => data.principal().is_none(),
397 debug!("issue33140_self_ty - MATCHES!");
400 debug!("issue33140_self_ty - non-matching self type");
405 /// Check if a function is async.
406 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
407 let node = tcx.hir().get_by_def_id(def_id.expect_local());
408 node.fn_sig().map_or(hir::IsAsync::NotAsync, |sig| sig.header.asyncness)
411 pub fn provide(providers: &mut ty::query::Providers) {
412 *providers = ty::query::Providers {
414 adt_sized_constraint,
416 param_env_reveal_all_normalized,
417 instance_def_size_estimate,