| use rustc_errors::ErrorGuaranteed; |
| use rustc_hir::def::DefKind; |
| use rustc_hir::def_id::DefId; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_middle::query::Providers; |
| use rustc_middle::traits::{BuiltinImplSource, CodegenObligationError}; |
| use rustc_middle::ty::GenericArgsRef; |
| use rustc_middle::ty::{self, Instance, TyCtxt, TypeVisitableExt}; |
| use rustc_span::sym; |
| use rustc_trait_selection::traits; |
| use traits::{translate_args, Reveal}; |
| |
| use crate::errors::UnexpectedFnPtrAssociatedItem; |
| |
| fn resolve_instance<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>, |
| ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { |
| let (param_env, (def_id, args)) = key.into_parts(); |
| |
| 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); |
| resolve_associated_item( |
| tcx, |
| def_id, |
| param_env, |
| trait_def_id, |
| tcx.normalize_erasing_regions(param_env, args), |
| ) |
| } else { |
| let def = if matches!(tcx.def_kind(def_id), DefKind::Fn) && tcx.is_intrinsic(def_id) { |
| debug!(" => intrinsic"); |
| ty::InstanceDef::Intrinsic(def_id) |
| } else if Some(def_id) == tcx.lang_items().drop_in_place_fn() { |
| let ty = args.type_at(0); |
| |
| if ty.needs_drop(tcx, param_env) { |
| debug!(" => nontrivial drop glue"); |
| match *ty.kind() { |
| ty::Closure(..) |
| | ty::Coroutine(..) |
| | 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) |
| } |
| } else { |
| debug!(" => free item"); |
| // FIXME(effects): we may want to erase the effect param if that is present on this item. |
| ty::InstanceDef::Item(def_id) |
| }; |
| |
| Ok(Some(Instance { def, args })) |
| }; |
| 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_args: GenericArgsRef<'tcx>, |
| ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> { |
| debug!(?trait_item_id, ?param_env, ?trait_id, ?rcvr_args, "resolve_associated_item"); |
| |
| let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_args); |
| |
| let vtbl = match tcx.codegen_select_candidate((param_env, trait_ref)) { |
| Ok(vtbl) => vtbl, |
| Err(CodegenObligationError::Ambiguity) => { |
| let reported = tcx.sess.delay_span_bug( |
| tcx.def_span(trait_item_id), |
| format!( |
| "encountered ambiguity selecting `{trait_ref:?}` during codegen, presuming due to \ |
| overflow or prior type error", |
| ), |
| ); |
| 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_args, impl_data |
| ); |
| assert!(!rcvr_args.has_infer()); |
| assert!(!trait_ref.has_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 infcx = tcx.infer_ctxt().build(); |
| let param_env = param_env.with_reveal_all_normalized(tcx); |
| let args = rcvr_args.rebase_onto(tcx, trait_def_id, impl_data.args); |
| let args = translate_args( |
| &infcx, |
| param_env, |
| impl_data.impl_def_id, |
| args, |
| leaf_def.defining_node, |
| ); |
| let args = infcx.tcx.erase_regions(args); |
| |
| // 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); |
| } |
| |
| // HACK: We may have overlapping `dyn Trait` built-in impls and |
| // user-provided blanket impls. Detect that case here, and return |
| // ambiguity. |
| // |
| // This should not affect totally monomorphized contexts, only |
| // resolve calls that happen polymorphically, such as the mir-inliner |
| // and const-prop (and also some lints). |
| let self_ty = rcvr_args.type_at(0); |
| if !self_ty.is_known_rigid() { |
| let predicates = tcx |
| .predicates_of(impl_data.impl_def_id) |
| .instantiate(tcx, impl_data.args) |
| .predicates; |
| let sized_def_id = tcx.lang_items().sized_trait(); |
| // If we find a `Self: Sized` bound on the item, then we know |
| // that `dyn Trait` can certainly never apply here. |
| if !predicates.into_iter().filter_map(ty::Clause::as_trait_clause).any(|clause| { |
| Some(clause.def_id()) == sized_def_id |
| && clause.skip_binder().self_ty() == self_ty |
| }) { |
| return Ok(None); |
| } |
| } |
| |
| // Any final impl is required to define all associated items. |
| if !leaf_def.item.defaultness(tcx).has_value() { |
| let guard = tcx.sess.delay_span_bug( |
| tcx.def_span(leaf_def.item.def_id), |
| "missing value for assoc item in impl", |
| ); |
| return Err(guard); |
| } |
| |
| let args = tcx.erase_regions(args); |
| |
| // 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). |
| if leaf_def.item.kind == ty::AssocKind::Const |
| && trait_item_id != leaf_def.item.def_id |
| && let Some(leaf_def_item) = leaf_def.item.def_id.as_local() |
| { |
| tcx.compare_impl_const((leaf_def_item, trait_item_id))?; |
| } |
| |
| Some(ty::Instance::new(leaf_def.item.def_id, args)) |
| } |
| traits::ImplSource::Builtin(BuiltinImplSource::Object { vtable_base }, _) => { |
| traits::get_vtable_index_of_object_method(tcx, *vtable_base, trait_item_id).map( |
| |index| Instance { |
| def: ty::InstanceDef::Virtual(trait_item_id, index), |
| args: rcvr_args, |
| }, |
| ) |
| } |
| traits::ImplSource::Builtin(BuiltinImplSource::Misc, _) => { |
| let lang_items = tcx.lang_items(); |
| if Some(trait_ref.def_id) == 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, param_env); |
| match self_ty.kind() { |
| _ if is_copy => (), |
| ty::Coroutine(..) |
| | ty::CoroutineWitness(..) |
| | ty::Closure(..) |
| | ty::Tuple(..) => {} |
| _ => return Ok(None), |
| }; |
| |
| Some(Instance { |
| def: ty::InstanceDef::CloneShim(trait_item_id, self_ty), |
| args: rcvr_args, |
| }) |
| } else { |
| assert_eq!(name, sym::clone_from); |
| |
| // Use the default `fn clone_from` from `trait Clone`. |
| let args = tcx.erase_regions(rcvr_args); |
| Some(ty::Instance::new(trait_item_id, args)) |
| } |
| } else if Some(trait_ref.def_id) == lang_items.fn_ptr_trait() { |
| if lang_items.fn_ptr_addr() == Some(trait_item_id) { |
| let self_ty = trait_ref.self_ty(); |
| if !matches!(self_ty.kind(), ty::FnPtr(..)) { |
| return Ok(None); |
| } |
| Some(Instance { |
| def: ty::InstanceDef::FnPtrAddrShim(trait_item_id, self_ty), |
| args: rcvr_args, |
| }) |
| } else { |
| tcx.sess.emit_fatal(UnexpectedFnPtrAssociatedItem { |
| span: tcx.def_span(trait_item_id), |
| }) |
| } |
| } else if Some(trait_ref.def_id) == lang_items.future_trait() { |
| let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else { |
| bug!() |
| }; |
| if Some(trait_item_id) == tcx.lang_items().future_poll_fn() { |
| // `Future::poll` is generated by the compiler. |
| Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args: args }) |
| } else { |
| // All other methods are default methods of the `Future` trait. |
| // (this assumes that `ImplSource::Builtin` is only used for methods on `Future`) |
| debug_assert!(tcx.defaultness(trait_item_id).has_value()); |
| Some(Instance::new(trait_item_id, rcvr_args)) |
| } |
| } else if Some(trait_ref.def_id) == lang_items.iterator_trait() { |
| let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else { |
| bug!() |
| }; |
| if Some(trait_item_id) == tcx.lang_items().next_fn() { |
| // `Iterator::next` is generated by the compiler. |
| Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args }) |
| } else { |
| // All other methods are default methods of the `Iterator` trait. |
| // (this assumes that `ImplSource::Builtin` is only used for methods on `Iterator`) |
| debug_assert!(tcx.defaultness(trait_item_id).has_value()); |
| Some(Instance::new(trait_item_id, rcvr_args)) |
| } |
| } else if Some(trait_ref.def_id) == lang_items.coroutine_trait() { |
| let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else { |
| bug!() |
| }; |
| if cfg!(debug_assertions) && tcx.item_name(trait_item_id) != sym::resume { |
| // For compiler developers who'd like to add new items to `Coroutine`, |
| // you either need to generate a shim body, or perhaps return |
| // `InstanceDef::Item` pointing to a trait default method body if |
| // it is given a default implementation by the trait. |
| span_bug!( |
| tcx.def_span(coroutine_def_id), |
| "no definition for `{trait_ref}::{}` for built-in coroutine type", |
| tcx.item_name(trait_item_id) |
| ) |
| } |
| Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args }) |
| } else if tcx.fn_trait_kind_from_def_id(trait_ref.def_id).is_some() { |
| // FIXME: This doesn't check for malformed libcore that defines, e.g., |
| // `trait Fn { fn call_once(&self) { .. } }`. This is mostly for extension |
| // methods. |
| if cfg!(debug_assertions) |
| && ![sym::call, sym::call_mut, sym::call_once] |
| .contains(&tcx.item_name(trait_item_id)) |
| { |
| // For compiler developers who'd like to add new items to `Fn`/`FnMut`/`FnOnce`, |
| // you either need to generate a shim body, or perhaps return |
| // `InstanceDef::Item` pointing to a trait default method body if |
| // it is given a default implementation by the trait. |
| bug!( |
| "no definition for `{trait_ref}::{}` for built-in callable type", |
| tcx.item_name(trait_item_id) |
| ) |
| } |
| match *rcvr_args.type_at(0).kind() { |
| ty::Closure(closure_def_id, args) => { |
| let trait_closure_kind = tcx.fn_trait_kind_from_def_id(trait_id).unwrap(); |
| Instance::resolve_closure(tcx, closure_def_id, args, trait_closure_kind) |
| } |
| ty::FnDef(..) | ty::FnPtr(..) => Some(Instance { |
| def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_args.type_at(0)), |
| args: rcvr_args, |
| }), |
| _ => bug!( |
| "no built-in definition for `{trait_ref}::{}` for non-fn type", |
| tcx.item_name(trait_item_id) |
| ), |
| } |
| } else { |
| None |
| } |
| } |
| traits::ImplSource::Param(..) |
| | traits::ImplSource::Builtin(BuiltinImplSource::TraitUpcasting { .. }, _) |
| | traits::ImplSource::Builtin(BuiltinImplSource::TupleUnsizing, _) => None, |
| }) |
| } |
| |
| pub fn provide(providers: &mut Providers) { |
| *providers = Providers { resolve_instance, ..*providers }; |
| } |