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Diffstat (limited to 'compiler/rustc_ty_utils/src/instance.rs')
| -rw-r--r-- | compiler/rustc_ty_utils/src/instance.rs | 407 |
1 files changed, 407 insertions, 0 deletions
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs new file mode 100644 index 000000000..bd1d568cd --- /dev/null +++ b/compiler/rustc_ty_utils/src/instance.rs @@ -0,0 +1,407 @@ +use rustc_errors::ErrorGuaranteed; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_infer::infer::TyCtxtInferExt; +use rustc_middle::traits::CodegenObligationError; +use rustc_middle::ty::subst::SubstsRef; +use rustc_middle::ty::{ + self, Binder, Instance, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, +}; +use rustc_span::{sym, DUMMY_SP}; +use rustc_trait_selection::traits; +use traits::{translate_substs, Reveal}; + +use rustc_data_structures::sso::SsoHashSet; +use std::collections::btree_map::Entry; +use std::collections::BTreeMap; +use std::ops::ControlFlow; + +use tracing::debug; + +// FIXME(#86795): `BoundVarsCollector` here should **NOT** be used +// outside of `resolve_associated_item`. It's just to address #64494, +// #83765, and #85848 which are creating bound types/regions that lose +// their `Binder` *unintentionally*. +// It's ideal to remove `BoundVarsCollector` and just use +// `ty::Binder::*` methods but we use this stopgap until we figure out +// the "real" fix. +struct BoundVarsCollector<'tcx> { + binder_index: ty::DebruijnIndex, + vars: BTreeMap<u32, ty::BoundVariableKind>, + // We may encounter the same variable at different levels of binding, so + // this can't just be `Ty` + visited: SsoHashSet<(ty::DebruijnIndex, Ty<'tcx>)>, +} + +impl<'tcx> BoundVarsCollector<'tcx> { + fn new() -> Self { + BoundVarsCollector { + binder_index: ty::INNERMOST, + vars: BTreeMap::new(), + visited: SsoHashSet::default(), + } + } + + fn into_vars(self, tcx: TyCtxt<'tcx>) -> &'tcx ty::List<ty::BoundVariableKind> { + let max = self.vars.iter().map(|(k, _)| *k).max().unwrap_or(0); + for i in 0..max { + if let None = self.vars.get(&i) { + panic!("Unknown variable: {:?}", i); + } + } + + tcx.mk_bound_variable_kinds(self.vars.into_iter().map(|(_, v)| v)) + } +} + +impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> { + type BreakTy = (); + + fn visit_binder<T: TypeVisitable<'tcx>>( + &mut self, + t: &Binder<'tcx, T>, + ) -> ControlFlow<Self::BreakTy> { + self.binder_index.shift_in(1); + let result = t.super_visit_with(self); + self.binder_index.shift_out(1); + result + } + + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + if t.outer_exclusive_binder() < self.binder_index + || !self.visited.insert((self.binder_index, t)) + { + return ControlFlow::CONTINUE; + } + match *t.kind() { + ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => { + match self.vars.entry(bound_ty.var.as_u32()) { + Entry::Vacant(entry) => { + entry.insert(ty::BoundVariableKind::Ty(bound_ty.kind)); + } + Entry::Occupied(entry) => match entry.get() { + ty::BoundVariableKind::Ty(_) => {} + _ => bug!("Conflicting bound vars"), + }, + } + } + + _ => (), + }; + + t.super_visit_with(self) + } + + fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { + match *r { + ty::ReLateBound(index, br) if index == self.binder_index => { + match self.vars.entry(br.var.as_u32()) { + Entry::Vacant(entry) => { + entry.insert(ty::BoundVariableKind::Region(br.kind)); + } + Entry::Occupied(entry) => match entry.get() { + ty::BoundVariableKind::Region(_) => {} + _ => bug!("Conflicting bound vars"), + }, + } + } + + _ => (), + }; + + r.super_visit_with(self) + } +} + +fn resolve_instance<'tcx>( + tcx: TyCtxt<'tcx>, + key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>, +) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { + let (param_env, (did, substs)) = key.into_parts(); + if let Some(did) = did.as_local() { + if let Some(param_did) = tcx.opt_const_param_of(did) { + return tcx.resolve_instance_of_const_arg(param_env.and((did, param_did, substs))); + } + } + + inner_resolve_instance(tcx, param_env.and((ty::WithOptConstParam::unknown(did), substs))) +} + +fn resolve_instance_of_const_arg<'tcx>( + tcx: TyCtxt<'tcx>, + key: ty::ParamEnvAnd<'tcx, (LocalDefId, DefId, SubstsRef<'tcx>)>, +) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { + let (param_env, (did, const_param_did, substs)) = key.into_parts(); + inner_resolve_instance( + tcx, + param_env.and(( + ty::WithOptConstParam { did: did.to_def_id(), const_param_did: Some(const_param_did) }, + substs, + )), + ) +} + +fn inner_resolve_instance<'tcx>( + tcx: TyCtxt<'tcx>, + key: ty::ParamEnvAnd<'tcx, (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)>, +) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { + let (param_env, (def, substs)) = key.into_parts(); + + let result = if let Some(trait_def_id) = tcx.trait_of_item(def.did) { + debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env); + resolve_associated_item(tcx, def.did, param_env, trait_def_id, substs) + } else { + let ty = tcx.type_of(def.def_id_for_type_of()); + let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty); + + let def = match *item_type.kind() { + ty::FnDef(def_id, ..) if tcx.is_intrinsic(def_id) => { + debug!(" => intrinsic"); + ty::InstanceDef::Intrinsic(def.did) + } + ty::FnDef(def_id, substs) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => { + let ty = substs.type_at(0); + + if ty.needs_drop(tcx, param_env) { + debug!(" => nontrivial drop glue"); + match *ty.kind() { + ty::Closure(..) + | ty::Generator(..) + | ty::Tuple(..) + | ty::Adt(..) + | ty::Dynamic(..) + | ty::Array(..) + | ty::Slice(..) => {} + // Drop shims can only be built from ADTs. + _ => return Ok(None), + } + + ty::InstanceDef::DropGlue(def_id, Some(ty)) + } else { + debug!(" => trivial drop glue"); + ty::InstanceDef::DropGlue(def_id, None) + } + } + _ => { + debug!(" => free item"); + ty::InstanceDef::Item(def) + } + }; + Ok(Some(Instance { def, substs })) + }; + debug!("inner_resolve_instance: result={:?}", result); + result +} + +fn resolve_associated_item<'tcx>( + tcx: TyCtxt<'tcx>, + trait_item_id: DefId, + param_env: ty::ParamEnv<'tcx>, + trait_id: DefId, + rcvr_substs: SubstsRef<'tcx>, +) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { + debug!(?trait_item_id, ?param_env, ?trait_id, ?rcvr_substs, "resolve_associated_item"); + + let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs); + + // See FIXME on `BoundVarsCollector`. + let mut bound_vars_collector = BoundVarsCollector::new(); + trait_ref.visit_with(&mut bound_vars_collector); + let trait_binder = ty::Binder::bind_with_vars(trait_ref, bound_vars_collector.into_vars(tcx)); + let vtbl = match tcx.codegen_fulfill_obligation((param_env, trait_binder)) { + Ok(vtbl) => vtbl, + Err(CodegenObligationError::Ambiguity) => { + let reported = tcx.sess.delay_span_bug( + tcx.def_span(trait_item_id), + &format!( + "encountered ambiguity selecting `{:?}` during codegen, presuming due to \ + overflow or prior type error", + trait_binder + ), + ); + return Err(reported); + } + Err(CodegenObligationError::Unimplemented) => return Ok(None), + Err(CodegenObligationError::FulfillmentError) => return Ok(None), + }; + + // Now that we know which impl is being used, we can dispatch to + // the actual function: + Ok(match vtbl { + traits::ImplSource::UserDefined(impl_data) => { + debug!( + "resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}", + param_env, trait_item_id, rcvr_substs, impl_data + ); + assert!(!rcvr_substs.needs_infer()); + assert!(!trait_ref.needs_infer()); + + let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap(); + let trait_def = tcx.trait_def(trait_def_id); + let leaf_def = trait_def + .ancestors(tcx, impl_data.impl_def_id)? + .leaf_def(tcx, trait_item_id) + .unwrap_or_else(|| { + bug!("{:?} not found in {:?}", trait_item_id, impl_data.impl_def_id); + }); + + let substs = tcx.infer_ctxt().enter(|infcx| { + let param_env = param_env.with_reveal_all_normalized(tcx); + let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs); + let substs = translate_substs( + &infcx, + param_env, + impl_data.impl_def_id, + substs, + leaf_def.defining_node, + ); + infcx.tcx.erase_regions(substs) + }); + + // Since this is a trait item, we need to see if the item is either a trait default item + // or a specialization because we can't resolve those unless we can `Reveal::All`. + // NOTE: This should be kept in sync with the similar code in + // `rustc_trait_selection::traits::project::assemble_candidates_from_impls()`. + let eligible = if leaf_def.is_final() { + // Non-specializable items are always projectable. + true + } else { + // Only reveal a specializable default if we're past type-checking + // and the obligation is monomorphic, otherwise passes such as + // transmute checking and polymorphic MIR optimizations could + // get a result which isn't correct for all monomorphizations. + if param_env.reveal() == Reveal::All { + !trait_ref.still_further_specializable() + } else { + false + } + }; + + if !eligible { + return Ok(None); + } + + // If the item does not have a value, then we cannot return an instance. + if !leaf_def.item.defaultness(tcx).has_value() { + return Ok(None); + } + + let substs = tcx.erase_regions(substs); + + // Check if we just resolved an associated `const` declaration from + // a `trait` to an associated `const` definition in an `impl`, where + // the definition in the `impl` has the wrong type (for which an + // error has already been/will be emitted elsewhere). + // + // NB: this may be expensive, we try to skip it in all the cases where + // we know the error would've been caught (e.g. in an upstream crate). + // + // A better approach might be to just introduce a query (returning + // `Result<(), ErrorGuaranteed>`) for the check that `rustc_typeck` + // performs (i.e. that the definition's type in the `impl` matches + // the declaration in the `trait`), so that we can cheaply check + // here if it failed, instead of approximating it. + if leaf_def.item.kind == ty::AssocKind::Const + && trait_item_id != leaf_def.item.def_id + && leaf_def.item.def_id.is_local() + { + let normalized_type_of = |def_id, substs| { + tcx.subst_and_normalize_erasing_regions(substs, param_env, tcx.type_of(def_id)) + }; + + let original_ty = normalized_type_of(trait_item_id, rcvr_substs); + let resolved_ty = normalized_type_of(leaf_def.item.def_id, substs); + + if original_ty != resolved_ty { + let msg = format!( + "Instance::resolve: inconsistent associated `const` type: \ + was `{}: {}` but resolved to `{}: {}`", + tcx.def_path_str_with_substs(trait_item_id, rcvr_substs), + original_ty, + tcx.def_path_str_with_substs(leaf_def.item.def_id, substs), + resolved_ty, + ); + let span = tcx.def_span(leaf_def.item.def_id); + let reported = tcx.sess.delay_span_bug(span, &msg); + + return Err(reported); + } + } + + Some(ty::Instance::new(leaf_def.item.def_id, substs)) + } + traits::ImplSource::Generator(generator_data) => Some(Instance { + def: ty::InstanceDef::Item(ty::WithOptConstParam::unknown( + generator_data.generator_def_id, + )), + substs: generator_data.substs, + }), + traits::ImplSource::Closure(closure_data) => { + let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap(); + Instance::resolve_closure( + tcx, + closure_data.closure_def_id, + closure_data.substs, + trait_closure_kind, + ) + } + traits::ImplSource::FnPointer(ref data) => match data.fn_ty.kind() { + ty::FnDef(..) | ty::FnPtr(..) => Some(Instance { + def: ty::InstanceDef::FnPtrShim(trait_item_id, data.fn_ty), + substs: rcvr_substs, + }), + _ => None, + }, + traits::ImplSource::Object(ref data) => { + if let Some(index) = traits::get_vtable_index_of_object_method(tcx, data, trait_item_id) + { + Some(Instance { + def: ty::InstanceDef::Virtual(trait_item_id, index), + substs: rcvr_substs, + }) + } else { + None + } + } + traits::ImplSource::Builtin(..) => { + if Some(trait_ref.def_id) == tcx.lang_items().clone_trait() { + // FIXME(eddyb) use lang items for methods instead of names. + let name = tcx.item_name(trait_item_id); + if name == sym::clone { + let self_ty = trait_ref.self_ty(); + + let is_copy = self_ty.is_copy_modulo_regions(tcx.at(DUMMY_SP), param_env); + match self_ty.kind() { + _ if is_copy => (), + ty::Closure(..) | ty::Tuple(..) => {} + _ => return Ok(None), + }; + + Some(Instance { + def: ty::InstanceDef::CloneShim(trait_item_id, self_ty), + substs: rcvr_substs, + }) + } else { + assert_eq!(name, sym::clone_from); + + // Use the default `fn clone_from` from `trait Clone`. + let substs = tcx.erase_regions(rcvr_substs); + Some(ty::Instance::new(trait_item_id, substs)) + } + } else { + None + } + } + traits::ImplSource::AutoImpl(..) + | traits::ImplSource::Param(..) + | traits::ImplSource::TraitAlias(..) + | traits::ImplSource::DiscriminantKind(..) + | traits::ImplSource::Pointee(..) + | traits::ImplSource::TraitUpcasting(_) + | traits::ImplSource::ConstDestruct(_) => None, + }) +} + +pub fn provide(providers: &mut ty::query::Providers) { + *providers = + ty::query::Providers { resolve_instance, resolve_instance_of_const_arg, ..*providers }; +} |