1 use rustc_data_structures::fx::FxIndexSet;
3 use rustc_index::bit_set::BitSet;
4 use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
5 use rustc_session::config::TraitSolver;
6 use rustc_span::def_id::{DefId, CRATE_DEF_ID};
7 use rustc_trait_selection::traits;
9 fn sized_constraint_for_ty<'tcx>(
11 adtdef: ty::AdtDef<'tcx>,
14 use rustc_type_ir::sty::TyKind::*;
16 let result = match ty.kind() {
17 Bool | Char | Int(..) | Uint(..) | Float(..) | RawPtr(..) | Ref(..) | FnDef(..)
18 | FnPtr(_) | Array(..) | Closure(..) | Generator(..) | Never => vec![],
25 | GeneratorWitness(..)
26 | GeneratorWitnessMIR(..) => {
27 // these are never sized - return the target type
31 Tuple(ref tys) => match tys.last() {
33 Some(&ty) => sized_constraint_for_ty(tcx, adtdef, ty),
38 let adt_tys = adt.sized_constraint(tcx);
39 debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
43 .map(|ty| adt_tys.rebind(*ty).subst(tcx, substs))
44 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
49 // must calculate explicitly.
50 // FIXME: consider special-casing always-Sized projections
55 // perf hack: if there is a `T: Sized` bound, then
56 // we know that `T` is Sized and do not need to check
59 let Some(sized_trait) = tcx.lang_items().sized_trait() else { return vec![ty] };
60 let sized_predicate = ty::Binder::dummy(tcx.mk_trait_ref(sized_trait, [ty]))
63 let predicates = tcx.predicates_of(adtdef.did()).predicates;
64 if predicates.iter().any(|(p, _)| *p == sized_predicate) { vec![] } else { vec![ty] }
67 Placeholder(..) | Bound(..) | Infer(..) => {
68 bug!("unexpected type `{:?}` in sized_constraint_for_ty", ty)
71 debug!("sized_constraint_for_ty({:?}) = {:?}", ty, result);
75 fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
76 match tcx.hir().get_by_def_id(def_id.expect_local()) {
77 hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
78 hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
79 | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
81 bug!("`impl_defaultness` called on {:?}", node);
86 /// Calculates the `Sized` constraint.
88 /// In fact, there are only a few options for the types in the constraint:
89 /// - an obviously-unsized type
90 /// - a type parameter or projection whose Sizedness can't be known
91 /// - a tuple of type parameters or projections, if there are multiple
93 /// - an Error, if a type is infinitely sized
94 fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
95 if let Some(def_id) = def_id.as_local() {
96 if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
97 return tcx.intern_type_list(&[tcx.ty_error()]);
100 let def = tcx.adt_def(def_id);
102 let result = tcx.mk_type_list(
105 .flat_map(|v| v.fields.last())
106 .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did))),
109 debug!("adt_sized_constraint: {:?} => {:?}", def, result);
114 /// See `ParamEnv` struct definition for details.
115 fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
116 // 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.trait_solver == TraitSolver::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 // FIXME(consts): This is not exactly in line with the constness query.
141 let constness = match hir_id {
142 Some(hir_id) => match tcx.hir().get(hir_id) {
143 hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
144 if tcx.is_const_default_method(def_id) =>
146 hir::Constness::Const
149 hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(..), .. })
150 | hir::Node::Item(hir::Item { kind: hir::ItemKind::Static(..), .. })
151 | hir::Node::TraitItem(hir::TraitItem {
152 kind: hir::TraitItemKind::Const(..), ..
154 | hir::Node::AnonConst(_)
155 | hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
156 | hir::Node::ImplItem(hir::ImplItem {
158 hir::ImplItemKind::Fn(
160 header: hir::FnHeader { constness: hir::Constness::Const, .. },
166 }) => hir::Constness::Const,
168 hir::Node::ImplItem(hir::ImplItem {
169 kind: hir::ImplItemKind::Type(..) | hir::ImplItemKind::Fn(..),
172 let parent_hir_id = tcx.hir().parent_id(hir_id);
173 match tcx.hir().get(parent_hir_id) {
174 hir::Node::Item(hir::Item {
175 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
179 tcx.def_span(parent_hir_id.owner),
180 "impl item's parent node is not an impl",
185 hir::Node::Item(hir::Item {
187 hir::ItemKind::Fn(hir::FnSig { header: hir::FnHeader { constness, .. }, .. }, ..),
190 | hir::Node::TraitItem(hir::TraitItem {
192 hir::TraitItemKind::Fn(
193 hir::FnSig { header: hir::FnHeader { constness, .. }, .. },
198 | hir::Node::Item(hir::Item {
199 kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
203 _ => hir::Constness::NotConst,
205 // FIXME(consts): It's suspicious that a param-env for a foreign item
206 // will always have NotConst param-env, though we don't typically use
207 // that param-env for anything meaningful right now, so it's likely
209 None => hir::Constness::NotConst,
212 let unnormalized_env = ty::ParamEnv::new(
213 tcx.intern_predicates(&predicates),
214 traits::Reveal::UserFacing,
218 let body_id = local_did.unwrap_or(CRATE_DEF_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: TyCtxt<'_>, def_id: DefId) -> &ty::List<Predicate<'_>> {
230 use rustc_hir::{ForeignItemKind, ImplItemKind, ItemKind, Node, TraitItemKind};
231 use rustc_middle::ty::subst::GenericArgKind;
233 debug!("environment(def_id = {:?})", def_id);
235 // The environment of an impl Trait type is its defining function's environment.
236 if let Some(parent) = ty::is_impl_trait_defn(tcx, def_id) {
237 return well_formed_types_in_env(tcx, parent.to_def_id());
240 // Compute the bounds on `Self` and the type parameters.
241 let ty::InstantiatedPredicates { predicates, .. } =
242 tcx.predicates_of(def_id).instantiate_identity(tcx);
244 let clauses = predicates.into_iter();
246 if !def_id.is_local() {
247 return ty::List::empty();
249 let node = tcx.hir().get_by_def_id(def_id.expect_local());
258 let node_kind = match node {
259 Node::TraitItem(item) => match item.kind {
260 TraitItemKind::Fn(..) => NodeKind::Fn,
261 _ => NodeKind::Other,
264 Node::ImplItem(item) => match item.kind {
265 ImplItemKind::Fn(..) => NodeKind::Fn,
266 _ => NodeKind::Other,
269 Node::Item(item) => match item.kind {
270 ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => NodeKind::TraitImpl,
271 ItemKind::Impl(hir::Impl { of_trait: None, .. }) => NodeKind::InherentImpl,
272 ItemKind::Fn(..) => NodeKind::Fn,
273 _ => NodeKind::Other,
276 Node::ForeignItem(item) => match item.kind {
277 ForeignItemKind::Fn(..) => NodeKind::Fn,
278 _ => NodeKind::Other,
282 _ => NodeKind::Other,
285 // FIXME(eddyb) isn't the unordered nature of this a hazard?
286 let mut inputs = FxIndexSet::default();
289 // In a trait impl, we assume that the header trait ref and all its
290 // constituents are well-formed.
291 NodeKind::TraitImpl => {
292 let trait_ref = tcx.impl_trait_ref(def_id).expect("not an impl").subst_identity();
294 // FIXME(chalk): this has problems because of late-bound regions
295 //inputs.extend(trait_ref.substs.iter().flat_map(|arg| arg.walk()));
296 inputs.extend(trait_ref.substs.iter());
299 // In an inherent impl, we assume that the receiver type and all its
300 // constituents are well-formed.
301 NodeKind::InherentImpl => {
302 let self_ty = tcx.type_of(def_id);
303 inputs.extend(self_ty.walk());
306 // In an fn, we assume that the arguments and all their constituents are
309 let fn_sig = tcx.fn_sig(def_id).subst_identity();
310 let fn_sig = tcx.liberate_late_bound_regions(def_id, fn_sig);
312 inputs.extend(fn_sig.inputs().iter().flat_map(|ty| ty.walk()));
315 NodeKind::Other => (),
317 let input_clauses = inputs.into_iter().filter_map(|arg| {
319 GenericArgKind::Type(ty) => {
320 let binder = Binder::dummy(PredicateKind::TypeWellFormedFromEnv(ty));
321 Some(tcx.mk_predicate(binder))
324 // FIXME(eddyb) no WF conditions from lifetimes?
325 GenericArgKind::Lifetime(_) => None,
327 // FIXME(eddyb) support const generics in Chalk
328 GenericArgKind::Const(_) => None,
332 tcx.mk_predicates(clauses.chain(input_clauses))
335 fn param_env_reveal_all_normalized(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
336 tcx.param_env(def_id).with_reveal_all_normalized(tcx)
339 fn instance_def_size_estimate<'tcx>(
341 instance_def: ty::InstanceDef<'tcx>,
346 InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
347 let mir = tcx.instance_mir(instance_def);
348 mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
350 // Estimate the size of other compiler-generated shims to be 1.
355 /// If `def_id` is an issue 33140 hack impl, returns its self type; otherwise, returns `None`.
357 /// See [`ty::ImplOverlapKind::Issue33140`] for more details.
358 fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Ty<'_>> {
359 debug!("issue33140_self_ty({:?})", def_id);
362 .impl_trait_ref(def_id)
363 .unwrap_or_else(|| bug!("issue33140_self_ty called on inherent impl {:?}", def_id))
366 debug!("issue33140_self_ty({:?}), trait-ref={:?}", def_id, trait_ref);
368 let is_marker_like = tcx.impl_polarity(def_id) == ty::ImplPolarity::Positive
369 && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
371 // Check whether these impls would be ok for a marker trait.
373 debug!("issue33140_self_ty - not marker-like!");
377 // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
378 if trait_ref.substs.len() != 1 {
379 debug!("issue33140_self_ty - impl has substs!");
383 let predicates = tcx.predicates_of(def_id);
384 if predicates.parent.is_some() || !predicates.predicates.is_empty() {
385 debug!("issue33140_self_ty - impl has predicates {:?}!", predicates);
389 let self_ty = trait_ref.self_ty();
390 let self_ty_matches = match self_ty.kind() {
391 ty::Dynamic(ref data, re, _) if re.is_static() => data.principal().is_none(),
396 debug!("issue33140_self_ty - MATCHES!");
399 debug!("issue33140_self_ty - non-matching self type");
404 /// Check if a function is async.
405 fn asyncness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::IsAsync {
406 let node = tcx.hir().get_by_def_id(def_id.expect_local());
407 node.fn_sig().map_or(hir::IsAsync::NotAsync, |sig| sig.header.asyncness)
410 fn unsizing_params_for_adt<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> BitSet<u32> {
411 let def = tcx.adt_def(def_id);
412 let num_params = tcx.generics_of(def_id).count();
414 let maybe_unsizing_param_idx = |arg: ty::GenericArg<'tcx>| match arg.unpack() {
415 ty::GenericArgKind::Type(ty) => match ty.kind() {
416 ty::Param(p) => Some(p.index),
420 // We can't unsize a lifetime
421 ty::GenericArgKind::Lifetime(_) => None,
423 ty::GenericArgKind::Const(ct) => match ct.kind() {
424 ty::ConstKind::Param(p) => Some(p.index),
429 // FIXME(eddyb) cache this (including computing `unsizing_params`)
430 // by putting it in a query; it would only need the `DefId` as it
431 // looks at declared field types, not anything substituted.
433 // The last field of the structure has to exist and contain type/const parameters.
434 let Some((tail_field, prefix_fields)) =
435 def.non_enum_variant().fields.split_last() else
437 return BitSet::new_empty(num_params);
440 let mut unsizing_params = BitSet::new_empty(num_params);
441 for arg in tcx.bound_type_of(tail_field.did).subst_identity().walk() {
442 if let Some(i) = maybe_unsizing_param_idx(arg) {
443 unsizing_params.insert(i);
447 // Ensure none of the other fields mention the parameters used
449 for field in prefix_fields {
450 for arg in tcx.bound_type_of(field.did).subst_identity().walk() {
451 if let Some(i) = maybe_unsizing_param_idx(arg) {
452 unsizing_params.remove(i);
460 pub fn provide(providers: &mut ty::query::Providers) {
461 *providers = ty::query::Providers {
463 adt_sized_constraint,
465 param_env_reveal_all_normalized,
466 instance_def_size_estimate,
469 unsizing_params_for_adt,