| use rustc_data_structures::fx::FxHashMap; |
| use rustc_hir::{def_id::DefId, Movability, Mutability}; |
| use rustc_infer::traits::query::NoSolution; |
| use rustc_middle::ty::{ |
| self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt, |
| }; |
| |
| use crate::solve::EvalCtxt; |
| |
| // Calculates the constituent types of a type for `auto trait` purposes. |
| // |
| // For types with an "existential" binder, i.e. generator witnesses, we also |
| // instantiate the binder with placeholders eagerly. |
| pub(in crate::solve) fn instantiate_constituent_tys_for_auto_trait<'tcx>( |
| ecx: &EvalCtxt<'_, 'tcx>, |
| ty: Ty<'tcx>, |
| ) -> Result<Vec<Ty<'tcx>>, NoSolution> { |
| let tcx = ecx.tcx(); |
| match *ty.kind() { |
| ty::Uint(_) |
| | ty::Int(_) |
| | ty::Bool |
| | ty::Float(_) |
| | ty::FnDef(..) |
| | ty::FnPtr(_) |
| | ty::Error(_) |
| | ty::Never |
| | ty::Char => Ok(vec![]), |
| |
| // Treat `str` like it's defined as `struct str([u8]);` |
| ty::Str => Ok(vec![tcx.mk_slice(tcx.types.u8)]), |
| |
| ty::Dynamic(..) |
| | ty::Param(..) |
| | ty::Foreign(..) |
| | ty::Alias(ty::Projection | ty::Inherent, ..) |
| | ty::Placeholder(..) |
| | ty::Bound(..) |
| | ty::Infer(_) => { |
| bug!("unexpected type `{ty}`") |
| } |
| |
| ty::RawPtr(ty::TypeAndMut { ty: element_ty, .. }) | ty::Ref(_, element_ty, _) => { |
| Ok(vec![element_ty]) |
| } |
| |
| ty::Array(element_ty, _) | ty::Slice(element_ty) => Ok(vec![element_ty]), |
| |
| ty::Tuple(ref tys) => { |
| // (T1, ..., Tn) -- meets any bound that all of T1...Tn meet |
| Ok(tys.iter().collect()) |
| } |
| |
| ty::Closure(_, ref substs) => Ok(vec![substs.as_closure().tupled_upvars_ty()]), |
| |
| ty::Generator(_, ref substs, _) => { |
| let generator_substs = substs.as_generator(); |
| Ok(vec![generator_substs.tupled_upvars_ty(), generator_substs.witness()]) |
| } |
| |
| ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()), |
| |
| ty::GeneratorWitnessMIR(def_id, substs) => Ok(ecx |
| .tcx() |
| .generator_hidden_types(def_id) |
| .map(|bty| { |
| ecx.instantiate_binder_with_placeholders(replace_erased_lifetimes_with_bound_vars( |
| tcx, |
| bty.subst(tcx, substs), |
| )) |
| }) |
| .collect()), |
| |
| // For `PhantomData<T>`, we pass `T`. |
| ty::Adt(def, substs) if def.is_phantom_data() => Ok(vec![substs.type_at(0)]), |
| |
| ty::Adt(def, substs) => Ok(def.all_fields().map(|f| f.ty(tcx, substs)).collect()), |
| |
| ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => { |
| // We can resolve the `impl Trait` to its concrete type, |
| // which enforces a DAG between the functions requiring |
| // the auto trait bounds in question. |
| Ok(vec![tcx.type_of(def_id).subst(tcx, substs)]) |
| } |
| } |
| } |
| |
| pub(in crate::solve) fn replace_erased_lifetimes_with_bound_vars<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| ty: Ty<'tcx>, |
| ) -> ty::Binder<'tcx, Ty<'tcx>> { |
| debug_assert!(!ty.has_late_bound_regions()); |
| let mut counter = 0; |
| let ty = tcx.fold_regions(ty, |r, current_depth| match r.kind() { |
| ty::ReErased => { |
| let br = |
| ty::BoundRegion { var: ty::BoundVar::from_u32(counter), kind: ty::BrAnon(None) }; |
| counter += 1; |
| tcx.mk_re_late_bound(current_depth, br) |
| } |
| // All free regions should be erased here. |
| r => bug!("unexpected region: {r:?}"), |
| }); |
| let bound_vars = tcx.mk_bound_variable_kinds_from_iter( |
| (0..counter).map(|_| ty::BoundVariableKind::Region(ty::BrAnon(None))), |
| ); |
| ty::Binder::bind_with_vars(ty, bound_vars) |
| } |
| |
| pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>( |
| ecx: &EvalCtxt<'_, 'tcx>, |
| ty: Ty<'tcx>, |
| ) -> Result<Vec<Ty<'tcx>>, NoSolution> { |
| match *ty.kind() { |
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) |
| | ty::Uint(_) |
| | ty::Int(_) |
| | ty::Bool |
| | ty::Float(_) |
| | ty::FnDef(..) |
| | ty::FnPtr(_) |
| | ty::RawPtr(..) |
| | ty::Char |
| | ty::Ref(..) |
| | ty::Generator(..) |
| | ty::GeneratorWitness(..) |
| | ty::GeneratorWitnessMIR(..) |
| | ty::Array(..) |
| | ty::Closure(..) |
| | ty::Never |
| | ty::Dynamic(_, _, ty::DynStar) |
| | ty::Error(_) => Ok(vec![]), |
| |
| ty::Str |
| | ty::Slice(_) |
| | ty::Dynamic(..) |
| | ty::Foreign(..) |
| | ty::Alias(..) |
| | ty::Param(_) |
| | ty::Placeholder(..) => Err(NoSolution), |
| |
| ty::Bound(..) |
| | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { |
| bug!("unexpected type `{ty}`") |
| } |
| |
| ty::Tuple(tys) => Ok(tys.to_vec()), |
| |
| ty::Adt(def, substs) => { |
| let sized_crit = def.sized_constraint(ecx.tcx()); |
| Ok(sized_crit.subst_iter_copied(ecx.tcx(), substs).collect()) |
| } |
| } |
| } |
| |
| pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>( |
| ecx: &EvalCtxt<'_, 'tcx>, |
| ty: Ty<'tcx>, |
| ) -> Result<Vec<Ty<'tcx>>, NoSolution> { |
| match *ty.kind() { |
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) |
| | ty::FnDef(..) |
| | ty::FnPtr(_) |
| | ty::Error(_) => Ok(vec![]), |
| |
| // Implementations are provided in core |
| ty::Uint(_) |
| | ty::Int(_) |
| | ty::Bool |
| | ty::Float(_) |
| | ty::Char |
| | ty::RawPtr(..) |
| | ty::Never |
| | ty::Ref(_, _, Mutability::Not) |
| | ty::Array(..) => Err(NoSolution), |
| |
| ty::Dynamic(..) |
| | ty::Str |
| | ty::Slice(_) |
| | ty::Generator(_, _, Movability::Static) |
| | ty::Foreign(..) |
| | ty::Ref(_, _, Mutability::Mut) |
| | ty::Adt(_, _) |
| | ty::Alias(_, _) |
| | ty::Param(_) |
| | ty::Placeholder(..) => Err(NoSolution), |
| |
| ty::Bound(..) |
| | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { |
| bug!("unexpected type `{ty}`") |
| } |
| |
| ty::Tuple(tys) => Ok(tys.to_vec()), |
| |
| ty::Closure(_, substs) => Ok(vec![substs.as_closure().tupled_upvars_ty()]), |
| |
| ty::Generator(_, substs, Movability::Movable) => { |
| if ecx.tcx().features().generator_clone { |
| let generator = substs.as_generator(); |
| Ok(vec![generator.tupled_upvars_ty(), generator.witness()]) |
| } else { |
| Err(NoSolution) |
| } |
| } |
| |
| ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()), |
| |
| ty::GeneratorWitnessMIR(def_id, substs) => Ok(ecx |
| .tcx() |
| .generator_hidden_types(def_id) |
| .map(|bty| { |
| ecx.instantiate_binder_with_placeholders(replace_erased_lifetimes_with_bound_vars( |
| ecx.tcx(), |
| bty.subst(ecx.tcx(), substs), |
| )) |
| }) |
| .collect()), |
| } |
| } |
| |
| // Returns a binder of the tupled inputs types and output type from a builtin callable type. |
| pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| self_ty: Ty<'tcx>, |
| goal_kind: ty::ClosureKind, |
| ) -> Result<Option<ty::Binder<'tcx, (Ty<'tcx>, Ty<'tcx>)>>, NoSolution> { |
| match *self_ty.kind() { |
| // keep this in sync with assemble_fn_pointer_candidates until the old solver is removed. |
| ty::FnDef(def_id, substs) => { |
| let sig = tcx.fn_sig(def_id); |
| if sig.skip_binder().is_fn_trait_compatible() |
| && tcx.codegen_fn_attrs(def_id).target_features.is_empty() |
| { |
| Ok(Some( |
| sig.subst(tcx, substs) |
| .map_bound(|sig| (tcx.mk_tup(sig.inputs()), sig.output())), |
| )) |
| } else { |
| Err(NoSolution) |
| } |
| } |
| // keep this in sync with assemble_fn_pointer_candidates until the old solver is removed. |
| ty::FnPtr(sig) => { |
| if sig.is_fn_trait_compatible() { |
| Ok(Some(sig.map_bound(|sig| (tcx.mk_tup(sig.inputs()), sig.output())))) |
| } else { |
| Err(NoSolution) |
| } |
| } |
| ty::Closure(_, substs) => { |
| let closure_substs = substs.as_closure(); |
| match closure_substs.kind_ty().to_opt_closure_kind() { |
| // If the closure's kind doesn't extend the goal kind, |
| // then the closure doesn't implement the trait. |
| Some(closure_kind) => { |
| if !closure_kind.extends(goal_kind) { |
| return Err(NoSolution); |
| } |
| } |
| // Closure kind is not yet determined, so we return ambiguity unless |
| // the expected kind is `FnOnce` as that is always implemented. |
| None => { |
| if goal_kind != ty::ClosureKind::FnOnce { |
| return Ok(None); |
| } |
| } |
| } |
| Ok(Some(closure_substs.sig().map_bound(|sig| (sig.inputs()[0], sig.output())))) |
| } |
| ty::Bool |
| | ty::Char |
| | ty::Int(_) |
| | ty::Uint(_) |
| | ty::Float(_) |
| | ty::Adt(_, _) |
| | ty::Foreign(_) |
| | ty::Str |
| | ty::Array(_, _) |
| | ty::Slice(_) |
| | ty::RawPtr(_) |
| | ty::Ref(_, _, _) |
| | ty::Dynamic(_, _, _) |
| | ty::Generator(_, _, _) |
| | ty::GeneratorWitness(_) |
| | ty::GeneratorWitnessMIR(..) |
| | ty::Never |
| | ty::Tuple(_) |
| | ty::Alias(_, _) |
| | ty::Param(_) |
| | ty::Placeholder(..) |
| | ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) |
| | ty::Error(_) => Err(NoSolution), |
| |
| ty::Bound(..) |
| | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { |
| bug!("unexpected type `{self_ty}`") |
| } |
| } |
| } |
| |
| /// Assemble a list of predicates that would be present on a theoretical |
| /// user impl for an object type. These predicates must be checked any time |
| /// we assemble a built-in object candidate for an object type, since they |
| /// are not implied by the well-formedness of the type. |
| /// |
| /// For example, given the following traits: |
| /// |
| /// ```rust,ignore (theoretical code) |
| /// trait Foo: Baz { |
| /// type Bar: Copy; |
| /// } |
| /// |
| /// trait Baz {} |
| /// ``` |
| /// |
| /// For the dyn type `dyn Foo<Item = Ty>`, we can imagine there being a |
| /// pair of theoretical impls: |
| /// |
| /// ```rust,ignore (theoretical code) |
| /// impl Foo for dyn Foo<Item = Ty> |
| /// where |
| /// Self: Baz, |
| /// <Self as Foo>::Bar: Copy, |
| /// { |
| /// type Bar = Ty; |
| /// } |
| /// |
| /// impl Baz for dyn Foo<Item = Ty> {} |
| /// ``` |
| /// |
| /// However, in order to make such impls well-formed, we need to do an |
| /// additional step of eagerly folding the associated types in the where |
| /// clauses of the impl. In this example, that means replacing |
| /// `<Self as Foo>::Bar` with `Ty` in the first impl. |
| /// |
| // FIXME: This is only necessary as `<Self as Trait>::Assoc: ItemBound` |
| // bounds in impls are trivially proven using the item bound candidates. |
| // This is unsound in general and once that is fixed, we don't need to |
| // normalize eagerly here. See https://github.com/lcnr/solver-woes/issues/9 |
| // for more details. |
| pub(in crate::solve) fn predicates_for_object_candidate<'tcx>( |
| ecx: &EvalCtxt<'_, 'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| trait_ref: ty::TraitRef<'tcx>, |
| object_bound: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>, |
| ) -> Vec<ty::Predicate<'tcx>> { |
| let tcx = ecx.tcx(); |
| let mut requirements = vec![]; |
| requirements.extend( |
| tcx.super_predicates_of(trait_ref.def_id).instantiate(tcx, trait_ref.substs).predicates, |
| ); |
| for item in tcx.associated_items(trait_ref.def_id).in_definition_order() { |
| // FIXME(associated_const_equality): Also add associated consts to |
| // the requirements here. |
| if item.kind == ty::AssocKind::Type { |
| requirements.extend(tcx.item_bounds(item.def_id).subst(tcx, trait_ref.substs)); |
| } |
| } |
| |
| let mut replace_projection_with = FxHashMap::default(); |
| for bound in object_bound { |
| if let ty::ExistentialPredicate::Projection(proj) = bound.skip_binder() { |
| let proj = proj.with_self_ty(tcx, trait_ref.self_ty()); |
| let old_ty = replace_projection_with.insert(proj.def_id(), bound.rebind(proj)); |
| assert_eq!( |
| old_ty, |
| None, |
| "{} has two substitutions: {} and {}", |
| proj.projection_ty, |
| proj.term, |
| old_ty.unwrap() |
| ); |
| } |
| } |
| |
| requirements.fold_with(&mut ReplaceProjectionWith { |
| ecx, |
| param_env, |
| mapping: replace_projection_with, |
| }) |
| } |
| |
| struct ReplaceProjectionWith<'a, 'tcx> { |
| ecx: &'a EvalCtxt<'a, 'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| mapping: FxHashMap<DefId, ty::PolyProjectionPredicate<'tcx>>, |
| } |
| |
| impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceProjectionWith<'_, 'tcx> { |
| fn interner(&self) -> TyCtxt<'tcx> { |
| self.ecx.tcx() |
| } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| if let ty::Alias(ty::Projection, alias_ty) = *ty.kind() |
| && let Some(replacement) = self.mapping.get(&alias_ty.def_id) |
| { |
| // We may have a case where our object type's projection bound is higher-ranked, |
| // but the where clauses we instantiated are not. We can solve this by instantiating |
| // the binder at the usage site. |
| let proj = self.ecx.instantiate_binder_with_infer(*replacement); |
| // FIXME: Technically this folder could be fallible? |
| let nested = self |
| .ecx |
| .eq_and_get_goals(self.param_env, alias_ty, proj.projection_ty) |
| .expect("expected to be able to unify goal projection with dyn's projection"); |
| // FIXME: Technically we could register these too.. |
| assert!(nested.is_empty(), "did not expect unification to have any nested goals"); |
| proj.term.ty().unwrap() |
| } else { |
| ty.super_fold_with(self) |
| } |
| } |
| } |
