diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs | 200 |
1 files changed, 161 insertions, 39 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs index a11cd13cb..d7d93377c 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs @@ -1,16 +1,19 @@ -use rustc_hir::{Movability, Mutability}; -use rustc_infer::{infer::InferCtxt, traits::query::NoSolution}; -use rustc_middle::ty::{self, Ty, TyCtxt}; +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}; + +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(super) fn instantiate_constituent_tys_for_auto_trait<'tcx>( - infcx: &InferCtxt<'tcx>, + ecx: &EvalCtxt<'_, 'tcx>, ty: Ty<'tcx>, ) -> Result<Vec<Ty<'tcx>>, NoSolution> { - let tcx = infcx.tcx; + let tcx = ecx.tcx(); match *ty.kind() { ty::Uint(_) | ty::Int(_) @@ -18,21 +21,24 @@ pub(super) fn instantiate_constituent_tys_for_auto_trait<'tcx>( | ty::Float(_) | ty::FnDef(..) | ty::FnPtr(_) - | ty::Str | ty::Error(_) | ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) | ty::Never | ty::Char => Ok(vec![]), - ty::Placeholder(..) - | ty::Dynamic(..) + // Treat this like `struct str([u8]);` + ty::Str => Ok(vec![tcx.mk_slice(tcx.types.u8)]), + + ty::Dynamic(..) | ty::Param(..) | ty::Foreign(..) | ty::Alias(ty::Projection, ..) - | ty::Bound(..) - | ty::Infer(ty::TyVar(_)) => Err(NoSolution), + | ty::Placeholder(..) => Err(NoSolution), - ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => bug!(), + ty::Bound(..) + | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => { + bug!("unexpected type `{ty}`") + } ty::RawPtr(ty::TypeAndMut { ty: element_ty, .. }) | ty::Ref(_, element_ty, _) => { Ok(vec![element_ty]) @@ -52,9 +58,9 @@ pub(super) fn instantiate_constituent_tys_for_auto_trait<'tcx>( Ok(vec![generator_substs.tupled_upvars_ty(), generator_substs.witness()]) } - ty::GeneratorWitness(types) => { - Ok(infcx.replace_bound_vars_with_placeholders(types).to_vec()) - } + ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()), + + ty::GeneratorWitnessMIR(..) => todo!(), // For `PhantomData<T>`, we pass `T`. ty::Adt(def, substs) if def.is_phantom_data() => Ok(vec![substs.type_at(0)]), @@ -65,13 +71,13 @@ pub(super) fn instantiate_constituent_tys_for_auto_trait<'tcx>( // 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.bound_type_of(def_id).subst(tcx, substs)]) + Ok(vec![tcx.type_of(def_id).subst(tcx, substs)]) } } } pub(super) fn instantiate_constituent_tys_for_sized_trait<'tcx>( - infcx: &InferCtxt<'tcx>, + ecx: &EvalCtxt<'_, 'tcx>, ty: Ty<'tcx>, ) -> Result<Vec<Ty<'tcx>>, NoSolution> { match *ty.kind() { @@ -87,6 +93,7 @@ pub(super) fn instantiate_constituent_tys_for_sized_trait<'tcx>( | ty::Ref(..) | ty::Generator(..) | ty::GeneratorWitness(..) + | ty::GeneratorWitnessMIR(..) | ty::Array(..) | ty::Closure(..) | ty::Never @@ -99,27 +106,28 @@ pub(super) fn instantiate_constituent_tys_for_sized_trait<'tcx>( | ty::Foreign(..) | ty::Alias(..) | ty::Param(_) - | ty::Infer(ty::TyVar(_)) => Err(NoSolution), + | ty::Placeholder(..) => Err(NoSolution), - ty::Placeholder(..) - | ty::Bound(..) - | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => bug!(), + 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(infcx.tcx); + let sized_crit = def.sized_constraint(ecx.tcx()); Ok(sized_crit .0 .iter() - .map(|ty| sized_crit.rebind(*ty).subst(infcx.tcx, substs)) + .map(|ty| sized_crit.rebind(*ty).subst(ecx.tcx(), substs)) .collect()) } } } pub(super) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>( - infcx: &InferCtxt<'tcx>, + ecx: &EvalCtxt<'_, 'tcx>, ty: Ty<'tcx>, ) -> Result<Vec<Ty<'tcx>>, NoSolution> { match *ty.kind() { @@ -148,18 +156,19 @@ pub(super) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>( | ty::Adt(_, _) | ty::Alias(_, _) | ty::Param(_) - | ty::Infer(ty::TyVar(_)) => Err(NoSolution), + | ty::Placeholder(..) => Err(NoSolution), - ty::Placeholder(..) - | ty::Bound(..) - | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => bug!(), + 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 infcx.tcx.features().generator_clone { + if ecx.tcx().features().generator_clone { let generator = substs.as_generator(); Ok(vec![generator.tupled_upvars_ty(), generator.witness()]) } else { @@ -167,12 +176,13 @@ pub(super) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>( } } - ty::GeneratorWitness(types) => { - Ok(infcx.replace_bound_vars_with_placeholders(types).to_vec()) - } + ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()), + + ty::GeneratorWitnessMIR(..) => todo!(), } } +// Returns a binder of the tupled inputs types and output type from a builtin callable type. pub(crate) fn extract_tupled_inputs_and_output_from_callable<'tcx>( tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>, @@ -180,13 +190,11 @@ pub(crate) fn extract_tupled_inputs_and_output_from_callable<'tcx>( ) -> Result<Option<ty::Binder<'tcx, (Ty<'tcx>, Ty<'tcx>)>>, NoSolution> { match *self_ty.kind() { ty::FnDef(def_id, substs) => Ok(Some( - tcx.bound_fn_sig(def_id) + tcx.fn_sig(def_id) .subst(tcx, substs) - .map_bound(|sig| (tcx.mk_tup(sig.inputs().iter()), sig.output())), + .map_bound(|sig| (tcx.mk_tup(sig.inputs()), sig.output())), )), - ty::FnPtr(sig) => { - Ok(Some(sig.map_bound(|sig| (tcx.mk_tup(sig.inputs().iter()), sig.output())))) - } + ty::FnPtr(sig) => Ok(Some(sig.map_bound(|sig| (tcx.mk_tup(sig.inputs()), sig.output())))), ty::Closure(_, substs) => { let closure_substs = substs.as_closure(); match closure_substs.kind_ty().to_opt_closure_kind() { @@ -211,13 +219,127 @@ pub(crate) fn extract_tupled_inputs_and_output_from_callable<'tcx>( | ty::Dynamic(_, _, _) | ty::Generator(_, _, _) | ty::GeneratorWitness(_) + | ty::GeneratorWitnessMIR(..) | ty::Never | ty::Tuple(_) | ty::Alias(_, _) | ty::Param(_) - | ty::Placeholder(_) - | ty::Bound(_, _) - | ty::Infer(_) + | 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. +pub(crate) 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(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) + } } } |