1 use rustc_data_structures::fx::FxIndexSet;
3 use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
4 use rustc_session::config::TraitSolver;
5 use rustc_span::def_id::{DefId, CRATE_DEF_ID};
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))
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(tcx.mk_trait_ref(sized_trait, [ty]))
56 let predicates = tcx.predicates_of(adtdef.did()).predicates;
57 if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
60 Placeholder(..) | Bound(..) | Infer(..) => {
61 bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
64 debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
68 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
69 match tcx.hir().get_by_def_id(def_id.expect_local()) {
70 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
71 hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
72 | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
74 bug!("`impl_defaultness` called on {:?}", node);
79 /// Calculates the `Sized` constraint.
81 /// In fact, there are only a few options for the types in the constraint:
82 /// - an obviously-unsized type
83 /// - a type parameter or projection whose Sizedness can't be known
84 /// - a tuple of type parameters or projections, if there are multiple
86 /// - an Error, if a type is infinitely sized
87 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
88 if let Some(def_id) = def_id.as_local() {
89 if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
90 return tcx.intern_type_list(&[tcx.ty_error()]);
93 let def = tcx.adt_def(def_id);
95 let result = tcx.mk_type_list(
98 .flat_map(|v| v.fields.last())
99 .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did))),
102 debug!("adt_sized_constraint: {:?} => {:?}", def, result);
107 /// See `ParamEnv` struct definition for details.
108 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
109 // Compute the bounds on Self and the type parameters.
110 let ty::InstantiatedPredicates { mut predicates, .. } =
111 tcx.predicates_of(def_id).instantiate_identity(tcx);
113 // Finally, we have to normalize the bounds in the environment, in
114 // case they contain any associated type projections. This process
115 // can yield errors if the put in illegal associated types, like
116 // `<i32 as Foo>::Bar` where `i32` does not implement `Foo`. We
117 // report these errors right here; this doesn't actually feel
118 // right to me, because constructing the environment feels like a
119 // kind of an "idempotent" action, but I'm not sure where would be
120 // a better place. In practice, we construct environments for
121 // every fn once during type checking, and we'll abort if there
122 // are any errors at that point, so outside of type inference you can be
123 // sure that this will succeed without errors anyway.
125 if tcx.sess.opts.unstable_opts.trait_solver == TraitSolver::Chalk {
126 let environment = well_formed_types_in_env(tcx, def_id);
127 predicates.extend(environment);
130 let local_did = def_id.as_local();
131 let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
133 // FIXME(consts): This is not exactly in line with the constness query.
134 let constness = match hir_id {
135 Some(hir_id) => match tcx.hir().get(hir_id) {
136 hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
137 if tcx.is_const_default_method(def_id) =>
139 hir::Constness::Const
142 hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
143 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
144 | hir::Node::TraitItem(hir::TraitItem {
145 kind: hir::TraitItemKind::Const(..), ..
147 | hir::Node::AnonConst(_)
148 | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
149 | hir::Node::ImplItem(hir::ImplItem {
151 hir::ImplItemKind::Fn(
153 header: hir::FnHeader { constness: hir::Constness::Const, .. },
159 }) => hir::Constness::Const,
161 hir::Node::ImplItem(hir::ImplItem {
162 kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
165 let parent_hir_id = tcx.hir().parent_id(hir_id);
166 match tcx.hir().get(parent_hir_id) {
167 hir::Node::Item(hir::Item {
168 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
172 tcx.def_span(parent_hir_id.owner),
173 "impl item's parent node is not an impl",
178 hir::Node::Item(hir::Item {
180 hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
183 | hir::Node::TraitItem(hir::TraitItem {
185 hir::TraitItemKind::Fn(
186 hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
191 | hir::Node::Item(hir::Item {
192 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
196 _ => hir::Constness::NotConst,
198 // FIXME(consts): It's suspicious that a param-env for a foreign item
199 // will always have NotConst param-env, though we don't typically use
200 // that param-env for anything meaningful right now, so it's likely
202 None => hir::Constness::NotConst,
205 let unnormalized_env = ty::ParamEnv::new(
206 tcx.intern_predicates(&predicates),
207 traits::Reveal::UserFacing,
211 let body_id = local_did.unwrap_or(CRATE_DEF_ID);
212 let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
213 traits::normalize_param_env_or_error(tcx, unnormalized_env, cause)
216 /// Elaborate the environment.
218 /// Collect a list of `Predicate`'s used for building the `ParamEnv`. Adds `TypeWellFormedFromEnv`'s
219 /// that are assumed to be well-formed (because they come from the environment).
221 /// Used only in chalk mode.
222 fn well_formed_types_in_env(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::List<Predicate<'_>> {
223 use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
224 use rustc_middle::ty::subst::GenericArgKind;
226 debug!("environment(def_id = {:?})", def_id);
228 // The environment of an impl Trait type is its defining function's environment.
229 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
230 return well_formed_types_in_env(tcx, parent.to_def_id());
233 // Compute the bounds on `Self` and the type parameters.
234 let ty::InstantiatedPredicates { predicates, .. } =
235 tcx.predicates_of(def_id).instantiate_identity(tcx);
237 let clauses = predicates.into_iter();
239 if !def_id.is_local() {
240 return ty::List::empty();
242 let node = tcx.hir().get_by_def_id(def_id.expect_local());
251 let node_kind = match node {
252 Node::TraitItem(item) => match item.kind {
253 TraitItemKind::Fn(..) => NodeKind::Fn,
254 _ => NodeKind::Other,
257 Node::ImplItem(item) => match item.kind {
258 ImplItemKind::Fn(..) => NodeKind::Fn,
259 _ => NodeKind::Other,
262 Node::Item(item) => match item.kind {
263 ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => NodeKind::TraitImpl,
264 ItemKind::Impl(hir::Impl { of_trait: None, .. }) => NodeKind::InherentImpl,
265 ItemKind::Fn(..) => NodeKind::Fn,
266 _ => NodeKind::Other,
269 Node::ForeignItem(item) => match item.kind {
270 ForeignItemKind::Fn(..) => NodeKind::Fn,
271 _ => NodeKind::Other,
275 _ => NodeKind::Other,
278 // FIXME(eddyb) isn't the unordered nature of this a hazard?
279 let mut inputs = FxIndexSet::default();
282 // In a trait impl, we assume that the header trait ref and all its
283 // constituents are well-formed.
284 NodeKind::TraitImpl => {
285 let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl").subst_identity();
287 // FIXME(chalk): this has problems because of late-bound regions
288 //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
289 inputs.extend(trait_ref.substs.iter());
292 // In an inherent impl, we assume that the receiver type and all its
293 // constituents are well-formed.
294 NodeKind::InherentImpl => {
295 let self_ty = tcx.type_of(def_id);
296 inputs.extend(self_ty.walk());
299 // In an fn, we assume that the arguments and all their constituents are
302 let fn_sig = tcx.fn_sig(def_id);
303 let fn_sig = tcx.liberate_late_bound_regions(def_id, fn_sig);
305 inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
308 NodeKind::Other => (),
310 let input_clauses = inputs.into_iter().filter_map(|arg| {
312 GenericArgKind::Type(ty) => {
313 let binder = Binder::dummy(PredicateKind::TypeWellFormedFromEnv(ty));
314 Some(tcx.mk_predicate(binder))
317 // FIXME(eddyb) no WF conditions from lifetimes?
318 GenericArgKind::Lifetime(_) => None,
320 // FIXME(eddyb) support const generics in Chalk
321 GenericArgKind::Const(_) => None,
325 tcx.mk_predicates(clauses.chain(input_clauses))
328 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
329 tcx.param_env(def_id).with_reveal_all_normalized(tcx)
332 fn instance_def_size_estimate<'tcx>(
334 instance_def: ty::InstanceDef<'tcx>,
339 InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
340 let mir = tcx.instance_mir(instance_def);
341 mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
343 // Estimate the size of other compiler-generated shims to be 1.
348 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
350 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
351 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
352 debug!("issue33140_self_ty({:?})", def_id);
355 .impl_trait_ref(def_id)
356 .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id))
359 debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
361 let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
362 && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
364 // Check whether these impls would be ok for a marker trait.
366 debug!("issue33140_self_ty - not marker-like!");
370 // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
371 if trait_ref.substs.len() != 1 {
372 debug!("issue33140_self_ty - impl has substs!");
376 let predicates = tcx.predicates_of(def_id);
377 if predicates.parent.is_some() || !predicates.predicates.is_empty() {
378 debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
382 let self_ty = trait_ref.self_ty();
383 let self_ty_matches = match self_ty.kind() {
384 ty::Dynamic(ref data, re, _) if re.is_static() => data.principal().is_none(),
389 debug!("issue33140_self_ty - MATCHES!");
392 debug!("issue33140_self_ty - non-matching self type");
397 /// Check if a function is async.
398 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
399 let node = tcx.hir().get_by_def_id(def_id.expect_local());
400 node.fn_sig().map_or(hir::IsAsync::NotAsync, |sig| sig.header.asyncness)
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,