| use rustc_errors::ErrorReported; |
| use rustc_hir::def_id::DefId; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_middle::ty::subst::SubstsRef; |
| use rustc_middle::ty::{self, Instance, TyCtxt, TypeFoldable}; |
| use rustc_span::sym; |
| use rustc_target::spec::abi::Abi; |
| use rustc_trait_selection::traits; |
| use traits::{translate_substs, Reveal}; |
| |
| use log::debug; |
| |
| fn resolve_instance<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>, |
| ) -> Result<Option<Instance<'tcx>>, ErrorReported> { |
| let (param_env, (def_id, substs)) = key.into_parts(); |
| |
| debug!("resolve(def_id={:?}, substs={:?})", def_id, substs); |
| let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) { |
| debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env); |
| let item = tcx.associated_item(def_id); |
| resolve_associated_item(tcx, &item, param_env, trait_def_id, substs) |
| } else { |
| let ty = tcx.type_of(def_id); |
| let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, &ty); |
| |
| let def = match item_type.kind { |
| ty::FnDef(..) |
| if { |
| let f = item_type.fn_sig(tcx); |
| f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic |
| } => |
| { |
| debug!(" => intrinsic"); |
| ty::InstanceDef::Intrinsic(def_id) |
| } |
| 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) { |
| // `DropGlue` requires a monomorphic aka concrete type. |
| if ty.needs_subst() { |
| return Ok(None); |
| } |
| |
| debug!(" => nontrivial drop glue"); |
| 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_id) |
| } |
| }; |
| Ok(Some(Instance { def, substs })) |
| }; |
| debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result); |
| result |
| } |
| |
| fn resolve_associated_item<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| trait_item: &ty::AssocItem, |
| param_env: ty::ParamEnv<'tcx>, |
| trait_id: DefId, |
| rcvr_substs: SubstsRef<'tcx>, |
| ) -> Result<Option<Instance<'tcx>>, ErrorReported> { |
| let def_id = trait_item.def_id; |
| debug!( |
| "resolve_associated_item(trait_item={:?}, \ |
| param_env={:?}, \ |
| trait_id={:?}, \ |
| rcvr_substs={:?})", |
| def_id, param_env, trait_id, rcvr_substs |
| ); |
| |
| let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs); |
| let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)))?; |
| |
| // Now that we know which impl is being used, we can dispatch to |
| // the actual function: |
| Ok(match vtbl { |
| traits::ImplSourceUserDefined(impl_data) => { |
| debug!( |
| "resolving ImplSourceUserDefined: {:?}, {:?}, {:?}, {:?}", |
| param_env, trait_item, 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.ident, trait_item.kind) |
| .unwrap_or_else(|| { |
| bug!("{:?} not found in {:?}", trait_item, impl_data.impl_def_id); |
| }); |
| |
| let substs = tcx.infer_ctxt().enter(|infcx| { |
| let param_env = param_env.with_reveal_all(); |
| 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); |
| } |
| |
| 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<(), ErrorReported>`) 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 trait_item.kind == ty::AssocKind::Const |
| && trait_item.def_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.def_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.def_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); |
| tcx.sess.delay_span_bug(span, &msg); |
| |
| return Err(ErrorReported); |
| } |
| } |
| |
| Some(ty::Instance::new(leaf_def.item.def_id, substs)) |
| } |
| traits::ImplSourceGenerator(generator_data) => Some(Instance { |
| def: ty::InstanceDef::Item(generator_data.generator_def_id), |
| substs: generator_data.substs, |
| }), |
| traits::ImplSourceClosure(closure_data) => { |
| let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap(); |
| Some(Instance::resolve_closure( |
| tcx, |
| closure_data.closure_def_id, |
| closure_data.substs, |
| trait_closure_kind, |
| )) |
| } |
| traits::ImplSourceFnPointer(ref data) => { |
| // `FnPtrShim` requires a monomorphic aka concrete type. |
| if data.fn_ty.needs_subst() { |
| return Ok(None); |
| } |
| |
| Some(Instance { |
| def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty), |
| substs: rcvr_substs, |
| }) |
| } |
| traits::ImplSourceObject(ref data) => { |
| let index = traits::get_vtable_index_of_object_method(tcx, data, def_id); |
| Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs }) |
| } |
| traits::ImplSourceBuiltin(..) => { |
| 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(def_id); |
| if name == sym::clone { |
| let self_ty = trait_ref.self_ty(); |
| |
| // `CloneShim` requires a monomorphic aka concrete type. |
| if self_ty.needs_subst() { |
| return Ok(None); |
| } |
| |
| Some(Instance { |
| def: ty::InstanceDef::CloneShim(def_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(def_id, substs)) |
| } |
| } else { |
| None |
| } |
| } |
| traits::ImplSourceAutoImpl(..) |
| | traits::ImplSourceParam(..) |
| | traits::ImplSourceTraitAlias(..) |
| | traits::ImplSourceDiscriminantKind(..) => None, |
| }) |
| } |
| |
| pub fn provide(providers: &mut ty::query::Providers) { |
| *providers = ty::query::Providers { resolve_instance, ..*providers }; |
| } |