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 visit_binder<T: TypeFoldable<'tcx>>(
60 ) -> ControlFlow<Self::BreakTy> {
61 self.binder_index.shift_in(1);
62 let result = t.super_visit_with(self);
63 self.binder_index.shift_out(1);
67 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
68 if t.outer_exclusive_binder() < self.binder_index
69 || !self.visited.insert((self.binder_index, t))
71 return ControlFlow::CONTINUE;
74 ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
75 match self.vars.entry(bound_ty.var.as_u32()) {
76 Entry::Vacant(entry) => {
77 entry.insert(ty::BoundVariableKind::Ty(bound_ty.kind));
79 Entry::Occupied(entry) => match entry.get() {
80 ty::BoundVariableKind::Ty(_) => {}
81 _ => bug!("Conflicting bound vars"),
89 t.super_visit_with(self)
92 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
94 ty::ReLateBound(index, br) if *index == self.binder_index => {
95 match self.vars.entry(br.var.as_u32()) {
96 Entry::Vacant(entry) => {
97 entry.insert(ty::BoundVariableKind::Region(br.kind));
99 Entry::Occupied(entry) => match entry.get() {
100 ty::BoundVariableKind::Region(_) => {}
101 _ => bug!("Conflicting bound vars"),
109 r.super_visit_with(self)
113 #[instrument(level = "debug", skip(tcx))]
114 fn resolve_instance<'tcx>(
116 key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
117 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
118 let (param_env, (did, substs)) = key.into_parts();
119 if let Some(did) = did.as_local() {
120 if let Some(param_did) = tcx.opt_const_param_of(did) {
121 return tcx.resolve_instance_of_const_arg(param_env.and((did, param_did, substs)));
125 inner_resolve_instance(tcx, param_env.and((ty::WithOptConstParam::unknown(did), substs)))
128 fn resolve_instance_of_const_arg<'tcx>(
130 key: ty::ParamEnvAnd<'tcx, (LocalDefId, DefId, SubstsRef<'tcx>)>,
131 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
132 let (param_env, (did, const_param_did, substs)) = key.into_parts();
133 inner_resolve_instance(
136 ty::WithOptConstParam { did: did.to_def_id(), const_param_did: Some(const_param_did) },
142 #[instrument(level = "debug", skip(tcx))]
143 fn inner_resolve_instance<'tcx>(
145 key: ty::ParamEnvAnd<'tcx, (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)>,
146 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
147 let (param_env, (def, substs)) = key.into_parts();
149 let result = if let Some(trait_def_id) = tcx.trait_of_item(def.did) {
150 debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
151 resolve_associated_item(tcx, def.did, param_env, trait_def_id, substs)
153 let ty = tcx.type_of(def.def_id_for_type_of());
154 let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);
156 let def = match *item_type.kind() {
159 let f = item_type.fn_sig(tcx);
160 f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic
163 debug!(" => intrinsic");
164 ty::InstanceDef::Intrinsic(def.did)
166 ty::FnDef(def_id, substs) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => {
167 let ty = substs.type_at(0);
169 if ty.needs_drop(tcx, param_env) {
170 debug!(" => nontrivial drop glue");
178 | ty::Slice(..) => {}
179 // Drop shims can only be built from ADTs.
180 _ => return Ok(None),
183 ty::InstanceDef::DropGlue(def_id, Some(ty))
185 debug!(" => trivial drop glue");
186 ty::InstanceDef::DropGlue(def_id, None)
190 debug!(" => free item");
191 ty::InstanceDef::Item(def)
194 Ok(Some(Instance { def, substs }))
196 debug!("inner_resolve_instance: result={:?}", result);
200 fn resolve_associated_item<'tcx>(
202 trait_item_id: DefId,
203 param_env: ty::ParamEnv<'tcx>,
205 rcvr_substs: SubstsRef<'tcx>,
206 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
207 debug!(?trait_item_id, ?param_env, ?trait_id, ?rcvr_substs, "resolve_associated_item");
209 let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
211 // See FIXME on `BoundVarsCollector`.
212 let mut bound_vars_collector = BoundVarsCollector::new();
213 trait_ref.visit_with(&mut bound_vars_collector);
214 let trait_binder = ty::Binder::bind_with_vars(trait_ref, bound_vars_collector.into_vars(tcx));
215 let vtbl = tcx.codegen_fulfill_obligation((param_env, trait_binder))?;
217 // Now that we know which impl is being used, we can dispatch to
218 // the actual function:
220 traits::ImplSource::UserDefined(impl_data) => {
222 "resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}",
223 param_env, trait_item_id, rcvr_substs, impl_data
225 assert!(!rcvr_substs.needs_infer());
226 assert!(!trait_ref.needs_infer());
228 let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
229 let trait_def = tcx.trait_def(trait_def_id);
230 let leaf_def = trait_def
231 .ancestors(tcx, impl_data.impl_def_id)?
232 .leaf_def(tcx, trait_item_id)
234 bug!("{:?} not found in {:?}", trait_item_id, impl_data.impl_def_id);
237 let substs = tcx.infer_ctxt().enter(|infcx| {
238 let param_env = param_env.with_reveal_all_normalized(tcx);
239 let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
240 let substs = translate_substs(
243 impl_data.impl_def_id,
245 leaf_def.defining_node,
247 infcx.tcx.erase_regions(substs)
250 // Since this is a trait item, we need to see if the item is either a trait default item
251 // or a specialization because we can't resolve those unless we can `Reveal::All`.
252 // NOTE: This should be kept in sync with the similar code in
253 // `rustc_trait_selection::traits::project::assemble_candidates_from_impls()`.
254 let eligible = if leaf_def.is_final() {
255 // Non-specializable items are always projectable.
258 // Only reveal a specializable default if we're past type-checking
259 // and the obligation is monomorphic, otherwise passes such as
260 // transmute checking and polymorphic MIR optimizations could
261 // get a result which isn't correct for all monomorphizations.
262 if param_env.reveal() == Reveal::All {
263 !trait_ref.still_further_specializable()
273 let substs = tcx.erase_regions(substs);
275 // Check if we just resolved an associated `const` declaration from
276 // a `trait` to an associated `const` definition in an `impl`, where
277 // the definition in the `impl` has the wrong type (for which an
278 // error has already been/will be emitted elsewhere).
280 // NB: this may be expensive, we try to skip it in all the cases where
281 // we know the error would've been caught (e.g. in an upstream crate).
283 // A better approach might be to just introduce a query (returning
284 // `Result<(), ErrorReported>`) for the check that `rustc_typeck`
285 // performs (i.e. that the definition's type in the `impl` matches
286 // the declaration in the `trait`), so that we can cheaply check
287 // here if it failed, instead of approximating it.
288 if leaf_def.item.kind == ty::AssocKind::Const
289 && trait_item_id != leaf_def.item.def_id
290 && leaf_def.item.def_id.is_local()
292 let normalized_type_of = |def_id, substs| {
293 tcx.subst_and_normalize_erasing_regions(substs, param_env, tcx.type_of(def_id))
296 let original_ty = normalized_type_of(trait_item_id, rcvr_substs);
297 let resolved_ty = normalized_type_of(leaf_def.item.def_id, substs);
299 if original_ty != resolved_ty {
301 "Instance::resolve: inconsistent associated `const` type: \
302 was `{}: {}` but resolved to `{}: {}`",
303 tcx.def_path_str_with_substs(trait_item_id, rcvr_substs),
305 tcx.def_path_str_with_substs(leaf_def.item.def_id, substs),
308 let span = tcx.def_span(leaf_def.item.def_id);
309 tcx.sess.delay_span_bug(span, &msg);
311 return Err(ErrorReported);
315 Some(ty::Instance::new(leaf_def.item.def_id, substs))
317 traits::ImplSource::Generator(generator_data) => Some(Instance {
318 def: ty::InstanceDef::Item(ty::WithOptConstParam::unknown(
319 generator_data.generator_def_id,
321 substs: generator_data.substs,
323 traits::ImplSource::Closure(closure_data) => {
324 let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap();
325 Some(Instance::resolve_closure(
327 closure_data.closure_def_id,
332 traits::ImplSource::FnPointer(ref data) => match data.fn_ty.kind() {
333 ty::FnDef(..) | ty::FnPtr(..) => Some(Instance {
334 def: ty::InstanceDef::FnPtrShim(trait_item_id, data.fn_ty),
339 traits::ImplSource::Object(ref data) => {
340 let index = traits::get_vtable_index_of_object_method(tcx, data, trait_item_id);
342 def: ty::InstanceDef::Virtual(trait_item_id, index),
346 traits::ImplSource::Builtin(..) => {
347 if Some(trait_ref.def_id) == tcx.lang_items().clone_trait() {
348 // FIXME(eddyb) use lang items for methods instead of names.
349 let name = tcx.item_name(trait_item_id);
350 if name == sym::clone {
351 let self_ty = trait_ref.self_ty();
353 let is_copy = self_ty.is_copy_modulo_regions(tcx.at(DUMMY_SP), param_env);
354 match self_ty.kind() {
356 ty::Closure(..) | ty::Tuple(..) => {}
357 _ => return Ok(None),
361 def: ty::InstanceDef::CloneShim(trait_item_id, self_ty),
365 assert_eq!(name, sym::clone_from);
367 // Use the default `fn clone_from` from `trait Clone`.
368 let substs = tcx.erase_regions(rcvr_substs);
369 Some(ty::Instance::new(trait_item_id, substs))
375 traits::ImplSource::AutoImpl(..)
376 | traits::ImplSource::Param(..)
377 | traits::ImplSource::TraitAlias(..)
378 | traits::ImplSource::DiscriminantKind(..)
379 | traits::ImplSource::Pointee(..)
380 | traits::ImplSource::TraitUpcasting(_)
381 | traits::ImplSource::ConstDrop(_) => None,
385 pub fn provide(providers: &mut ty::query::Providers) {
387 ty::query::Providers { resolve_instance, resolve_instance_of_const_arg, ..*providers };