1 use rustc_errors::ErrorReported;
2 use rustc_hir::def_id::{DefId, LocalDefId};
3 use rustc_infer::infer::TyCtxtInferExt;
4 use rustc_middle::ty::subst::SubstsRef;
5 use rustc_middle::ty::{self, Binder, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitor};
6 use rustc_span::{sym, DUMMY_SP};
7 use rustc_target::spec::abi::Abi;
8 use rustc_trait_selection::traits;
9 use traits::{translate_substs, Reveal};
11 use rustc_data_structures::sso::SsoHashSet;
12 use std::collections::btree_map::Entry;
13 use std::collections::BTreeMap;
14 use std::ops::ControlFlow;
18 // FIXME(#86795): `BoundVarsCollector` here should **NOT** be used
19 // outside of `resolve_associated_item`. It's just to address #64494,
20 // #83765, and #85848 which are creating bound types/regions that lose
21 // their `Binder` *unintentionally*.
22 // It's ideal to remove `BoundVarsCollector` and just use
23 // `ty::Binder::*` methods but we use this stopgap until we figure out
25 struct BoundVarsCollector<'tcx> {
26 binder_index: ty::DebruijnIndex,
27 vars: BTreeMap<u32, ty::BoundVariableKind>,
28 // We may encounter the same variable at different levels of binding, so
29 // this can't just be `Ty`
30 visited: SsoHashSet<(ty::DebruijnIndex, Ty<'tcx>)>,
33 impl<'tcx> BoundVarsCollector<'tcx> {
36 binder_index: ty::INNERMOST,
37 vars: BTreeMap::new(),
38 visited: SsoHashSet::default(),
42 fn into_vars(self, tcx: TyCtxt<'tcx>) -> &'tcx ty::List<ty::BoundVariableKind> {
43 let max = self.vars.iter().map(|(k, _)| *k).max().unwrap_or(0);
45 if let None = self.vars.get(&i) {
46 panic!("Unknown variable: {:?}", i);
50 tcx.mk_bound_variable_kinds(self.vars.into_iter().map(|(_, v)| v))
54 impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> {
57 fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
58 // Anon const substs do not contain bound vars by default.
61 fn visit_binder<T: TypeFoldable<'tcx>>(
64 ) -> ControlFlow<Self::BreakTy> {
65 self.binder_index.shift_in(1);
66 let result = t.super_visit_with(self);
67 self.binder_index.shift_out(1);
71 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
72 if t.outer_exclusive_binder() < self.binder_index
73 || !self.visited.insert((self.binder_index, t))
75 return ControlFlow::CONTINUE;
78 ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
79 match self.vars.entry(bound_ty.var.as_u32()) {
80 Entry::Vacant(entry) => {
81 entry.insert(ty::BoundVariableKind::Ty(bound_ty.kind));
83 Entry::Occupied(entry) => match entry.get() {
84 ty::BoundVariableKind::Ty(_) => {}
85 _ => bug!("Conflicting bound vars"),
93 t.super_visit_with(self)
96 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
98 ty::ReLateBound(index, br) if *index == self.binder_index => {
99 match self.vars.entry(br.var.as_u32()) {
100 Entry::Vacant(entry) => {
101 entry.insert(ty::BoundVariableKind::Region(br.kind));
103 Entry::Occupied(entry) => match entry.get() {
104 ty::BoundVariableKind::Region(_) => {}
105 _ => bug!("Conflicting bound vars"),
113 r.super_visit_with(self)
117 #[instrument(level = "debug", skip(tcx))]
118 fn resolve_instance<'tcx>(
120 key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
121 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
122 let (param_env, (did, substs)) = key.into_parts();
123 if let Some(did) = did.as_local() {
124 if let Some(param_did) = tcx.opt_const_param_of(did) {
125 return tcx.resolve_instance_of_const_arg(param_env.and((did, param_did, substs)));
129 inner_resolve_instance(tcx, param_env.and((ty::WithOptConstParam::unknown(did), substs)))
132 fn resolve_instance_of_const_arg<'tcx>(
134 key: ty::ParamEnvAnd<'tcx, (LocalDefId, DefId, SubstsRef<'tcx>)>,
135 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
136 let (param_env, (did, const_param_did, substs)) = key.into_parts();
137 inner_resolve_instance(
140 ty::WithOptConstParam { did: did.to_def_id(), const_param_did: Some(const_param_did) },
146 #[instrument(level = "debug", skip(tcx))]
147 fn inner_resolve_instance<'tcx>(
149 key: ty::ParamEnvAnd<'tcx, (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)>,
150 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
151 let (param_env, (def, substs)) = key.into_parts();
153 let result = if let Some(trait_def_id) = tcx.trait_of_item(def.did) {
154 debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
155 let item = tcx.associated_item(def.did);
156 resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
158 let ty = tcx.type_of(def.def_id_for_type_of());
159 let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);
161 let def = match *item_type.kind() {
164 let f = item_type.fn_sig(tcx);
165 f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic
168 debug!(" => intrinsic");
169 ty::InstanceDef::Intrinsic(def.did)
171 ty::FnDef(def_id, substs) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => {
172 let ty = substs.type_at(0);
174 if ty.needs_drop(tcx, param_env) {
175 debug!(" => nontrivial drop glue");
183 | ty::Slice(..) => {}
184 // Drop shims can only be built from ADTs.
185 _ => return Ok(None),
188 ty::InstanceDef::DropGlue(def_id, Some(ty))
190 debug!(" => trivial drop glue");
191 ty::InstanceDef::DropGlue(def_id, None)
195 debug!(" => free item");
196 ty::InstanceDef::Item(def)
199 Ok(Some(Instance { def, substs }))
201 debug!("inner_resolve_instance: result={:?}", result);
205 fn resolve_associated_item<'tcx>(
207 trait_item: &ty::AssocItem,
208 param_env: ty::ParamEnv<'tcx>,
210 rcvr_substs: SubstsRef<'tcx>,
211 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
212 let def_id = trait_item.def_id;
214 "resolve_associated_item(trait_item={:?}, \
218 def_id, param_env, trait_id, rcvr_substs
221 let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
223 // See FIXME on `BoundVarsCollector`.
224 let mut bound_vars_collector = BoundVarsCollector::new();
225 trait_ref.visit_with(&mut bound_vars_collector);
226 let trait_binder = ty::Binder::bind_with_vars(trait_ref, bound_vars_collector.into_vars(tcx));
227 let vtbl = tcx.codegen_fulfill_obligation((param_env, trait_binder))?;
229 // Now that we know which impl is being used, we can dispatch to
230 // the actual function:
232 traits::ImplSource::UserDefined(impl_data) => {
234 "resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}",
235 param_env, trait_item, rcvr_substs, impl_data
237 assert!(!rcvr_substs.needs_infer());
238 assert!(!trait_ref.needs_infer());
240 let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
241 let trait_def = tcx.trait_def(trait_def_id);
242 let leaf_def = trait_def
243 .ancestors(tcx, impl_data.impl_def_id)?
244 .leaf_def(tcx, trait_item.ident, trait_item.kind)
246 bug!("{:?} not found in {:?}", trait_item, impl_data.impl_def_id);
249 let substs = tcx.infer_ctxt().enter(|infcx| {
250 let param_env = param_env.with_reveal_all_normalized(tcx);
251 let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
252 let substs = translate_substs(
255 impl_data.impl_def_id,
257 leaf_def.defining_node,
259 infcx.tcx.erase_regions(substs)
262 // Since this is a trait item, we need to see if the item is either a trait default item
263 // or a specialization because we can't resolve those unless we can `Reveal::All`.
264 // NOTE: This should be kept in sync with the similar code in
265 // `rustc_trait_selection::traits::project::assemble_candidates_from_impls()`.
266 let eligible = if leaf_def.is_final() {
267 // Non-specializable items are always projectable.
270 // Only reveal a specializable default if we're past type-checking
271 // and the obligation is monomorphic, otherwise passes such as
272 // transmute checking and polymorphic MIR optimizations could
273 // get a result which isn't correct for all monomorphizations.
274 if param_env.reveal() == Reveal::All {
275 !trait_ref.still_further_specializable()
285 let substs = tcx.erase_regions(substs);
287 // Check if we just resolved an associated `const` declaration from
288 // a `trait` to an associated `const` definition in an `impl`, where
289 // the definition in the `impl` has the wrong type (for which an
290 // error has already been/will be emitted elsewhere).
292 // NB: this may be expensive, we try to skip it in all the cases where
293 // we know the error would've been caught (e.g. in an upstream crate).
295 // A better approach might be to just introduce a query (returning
296 // `Result<(), ErrorReported>`) for the check that `rustc_typeck`
297 // performs (i.e. that the definition's type in the `impl` matches
298 // the declaration in the `trait`), so that we can cheaply check
299 // here if it failed, instead of approximating it.
300 if trait_item.kind == ty::AssocKind::Const
301 && trait_item.def_id != leaf_def.item.def_id
302 && leaf_def.item.def_id.is_local()
304 let normalized_type_of = |def_id, substs| {
305 tcx.subst_and_normalize_erasing_regions(substs, param_env, tcx.type_of(def_id))
308 let original_ty = normalized_type_of(trait_item.def_id, rcvr_substs);
309 let resolved_ty = normalized_type_of(leaf_def.item.def_id, substs);
311 if original_ty != resolved_ty {
313 "Instance::resolve: inconsistent associated `const` type: \
314 was `{}: {}` but resolved to `{}: {}`",
315 tcx.def_path_str_with_substs(trait_item.def_id, rcvr_substs),
317 tcx.def_path_str_with_substs(leaf_def.item.def_id, substs),
320 let span = tcx.def_span(leaf_def.item.def_id);
321 tcx.sess.delay_span_bug(span, &msg);
323 return Err(ErrorReported);
327 Some(ty::Instance::new(leaf_def.item.def_id, substs))
329 traits::ImplSource::Generator(generator_data) => Some(Instance {
330 def: ty::InstanceDef::Item(ty::WithOptConstParam::unknown(
331 generator_data.generator_def_id,
333 substs: generator_data.substs,
335 traits::ImplSource::Closure(closure_data) => {
336 let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap();
337 Some(Instance::resolve_closure(
339 closure_data.closure_def_id,
344 traits::ImplSource::FnPointer(ref data) => match data.fn_ty.kind() {
345 ty::FnDef(..) | ty::FnPtr(..) => Some(Instance {
346 def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
351 traits::ImplSource::Object(ref data) => {
352 let index = traits::get_vtable_index_of_object_method(tcx, data, def_id);
353 Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs })
355 traits::ImplSource::Builtin(..) => {
356 if Some(trait_ref.def_id) == tcx.lang_items().clone_trait() {
357 // FIXME(eddyb) use lang items for methods instead of names.
358 let name = tcx.item_name(def_id);
359 if name == sym::clone {
360 let self_ty = trait_ref.self_ty();
362 let is_copy = self_ty.is_copy_modulo_regions(tcx.at(DUMMY_SP), param_env);
363 match self_ty.kind() {
365 ty::Array(..) | ty::Closure(..) | ty::Tuple(..) => {}
366 _ => return Ok(None),
370 def: ty::InstanceDef::CloneShim(def_id, self_ty),
374 assert_eq!(name, sym::clone_from);
376 // Use the default `fn clone_from` from `trait Clone`.
377 let substs = tcx.erase_regions(rcvr_substs);
378 Some(ty::Instance::new(def_id, substs))
384 traits::ImplSource::AutoImpl(..)
385 | traits::ImplSource::Param(..)
386 | traits::ImplSource::TraitAlias(..)
387 | traits::ImplSource::DiscriminantKind(..)
388 | traits::ImplSource::Pointee(..)
389 | traits::ImplSource::TraitUpcasting(_)
390 | traits::ImplSource::ConstDrop(_) => None,
394 pub fn provide(providers: &mut ty::query::Providers) {
396 ty::query::Providers { resolve_instance, resolve_instance_of_const_arg, ..*providers };