diff options
Diffstat (limited to 'compiler/rustc_middle/src/ty/relate.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/relate.rs | 841 |
1 files changed, 841 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs new file mode 100644 index 000000000..818affa71 --- /dev/null +++ b/compiler/rustc_middle/src/ty/relate.rs @@ -0,0 +1,841 @@ +//! Generalized type relating mechanism. +//! +//! A type relation `R` relates a pair of values `(A, B)`. `A and B` are usually +//! types or regions but can be other things. Examples of type relations are +//! subtyping, type equality, etc. + +use crate::ty::error::{ExpectedFound, TypeError}; +use crate::ty::subst::{GenericArg, GenericArgKind, Subst, SubstsRef}; +use crate::ty::{self, ImplSubject, Term, Ty, TyCtxt, TypeFoldable}; +use rustc_hir as ast; +use rustc_hir::def_id::DefId; +use rustc_span::DUMMY_SP; +use rustc_target::spec::abi; +use std::iter; + +pub type RelateResult<'tcx, T> = Result<T, TypeError<'tcx>>; + +#[derive(Clone, Debug)] +pub enum Cause { + ExistentialRegionBound, // relating an existential region bound +} + +pub trait TypeRelation<'tcx>: Sized { + fn tcx(&self) -> TyCtxt<'tcx>; + + fn param_env(&self) -> ty::ParamEnv<'tcx>; + + /// Returns a static string we can use for printouts. + fn tag(&self) -> &'static str; + + /// Returns `true` if the value `a` is the "expected" type in the + /// relation. Just affects error messages. + fn a_is_expected(&self) -> bool; + + fn with_cause<F, R>(&mut self, _cause: Cause, f: F) -> R + where + F: FnOnce(&mut Self) -> R, + { + f(self) + } + + /// Generic relation routine suitable for most anything. + fn relate<T: Relate<'tcx>>(&mut self, a: T, b: T) -> RelateResult<'tcx, T> { + Relate::relate(self, a, b) + } + + /// Relate the two substitutions for the given item. The default + /// is to look up the variance for the item and proceed + /// accordingly. + fn relate_item_substs( + &mut self, + item_def_id: DefId, + a_subst: SubstsRef<'tcx>, + b_subst: SubstsRef<'tcx>, + ) -> RelateResult<'tcx, SubstsRef<'tcx>> { + debug!( + "relate_item_substs(item_def_id={:?}, a_subst={:?}, b_subst={:?})", + item_def_id, a_subst, b_subst + ); + + let tcx = self.tcx(); + let opt_variances = tcx.variances_of(item_def_id); + relate_substs_with_variances(self, item_def_id, opt_variances, a_subst, b_subst) + } + + /// Switch variance for the purpose of relating `a` and `b`. + fn relate_with_variance<T: Relate<'tcx>>( + &mut self, + variance: ty::Variance, + info: ty::VarianceDiagInfo<'tcx>, + a: T, + b: T, + ) -> RelateResult<'tcx, T>; + + // Overridable relations. You shouldn't typically call these + // directly, instead call `relate()`, which in turn calls + // these. This is both more uniform but also allows us to add + // additional hooks for other types in the future if needed + // without making older code, which called `relate`, obsolete. + + fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>>; + + fn regions( + &mut self, + a: ty::Region<'tcx>, + b: ty::Region<'tcx>, + ) -> RelateResult<'tcx, ty::Region<'tcx>>; + + fn consts( + &mut self, + a: ty::Const<'tcx>, + b: ty::Const<'tcx>, + ) -> RelateResult<'tcx, ty::Const<'tcx>>; + + fn binders<T>( + &mut self, + a: ty::Binder<'tcx, T>, + b: ty::Binder<'tcx, T>, + ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> + where + T: Relate<'tcx>; +} + +pub trait Relate<'tcx>: TypeFoldable<'tcx> + Copy { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: Self, + b: Self, + ) -> RelateResult<'tcx, Self>; +} + +/////////////////////////////////////////////////////////////////////////// +// Relate impls + +pub fn relate_type_and_mut<'tcx, R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::TypeAndMut<'tcx>, + b: ty::TypeAndMut<'tcx>, + base_ty: Ty<'tcx>, +) -> RelateResult<'tcx, ty::TypeAndMut<'tcx>> { + debug!("{}.mts({:?}, {:?})", relation.tag(), a, b); + if a.mutbl != b.mutbl { + Err(TypeError::Mutability) + } else { + let mutbl = a.mutbl; + let (variance, info) = match mutbl { + ast::Mutability::Not => (ty::Covariant, ty::VarianceDiagInfo::None), + ast::Mutability::Mut => { + (ty::Invariant, ty::VarianceDiagInfo::Invariant { ty: base_ty, param_index: 0 }) + } + }; + let ty = relation.relate_with_variance(variance, info, a.ty, b.ty)?; + Ok(ty::TypeAndMut { ty, mutbl }) + } +} + +#[inline] +pub fn relate_substs<'tcx, R: TypeRelation<'tcx>>( + relation: &mut R, + a_subst: SubstsRef<'tcx>, + b_subst: SubstsRef<'tcx>, +) -> RelateResult<'tcx, SubstsRef<'tcx>> { + relation.tcx().mk_substs(iter::zip(a_subst, b_subst).map(|(a, b)| { + relation.relate_with_variance(ty::Invariant, ty::VarianceDiagInfo::default(), a, b) + })) +} + +pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>( + relation: &mut R, + ty_def_id: DefId, + variances: &[ty::Variance], + a_subst: SubstsRef<'tcx>, + b_subst: SubstsRef<'tcx>, +) -> RelateResult<'tcx, SubstsRef<'tcx>> { + let tcx = relation.tcx(); + + let mut cached_ty = None; + let params = iter::zip(a_subst, b_subst).enumerate().map(|(i, (a, b))| { + let variance = variances[i]; + let variance_info = if variance == ty::Invariant { + let ty = + *cached_ty.get_or_insert_with(|| tcx.bound_type_of(ty_def_id).subst(tcx, a_subst)); + ty::VarianceDiagInfo::Invariant { ty, param_index: i.try_into().unwrap() } + } else { + ty::VarianceDiagInfo::default() + }; + relation.relate_with_variance(variance, variance_info, a, b) + }); + + tcx.mk_substs(params) +} + +impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::FnSig<'tcx>, + b: ty::FnSig<'tcx>, + ) -> RelateResult<'tcx, ty::FnSig<'tcx>> { + let tcx = relation.tcx(); + + if a.c_variadic != b.c_variadic { + return Err(TypeError::VariadicMismatch(expected_found( + relation, + a.c_variadic, + b.c_variadic, + ))); + } + let unsafety = relation.relate(a.unsafety, b.unsafety)?; + let abi = relation.relate(a.abi, b.abi)?; + + if a.inputs().len() != b.inputs().len() { + return Err(TypeError::ArgCount); + } + + let inputs_and_output = iter::zip(a.inputs(), b.inputs()) + .map(|(&a, &b)| ((a, b), false)) + .chain(iter::once(((a.output(), b.output()), true))) + .map(|((a, b), is_output)| { + if is_output { + relation.relate(a, b) + } else { + relation.relate_with_variance( + ty::Contravariant, + ty::VarianceDiagInfo::default(), + a, + b, + ) + } + }) + .enumerate() + .map(|(i, r)| match r { + Err(TypeError::Sorts(exp_found) | TypeError::ArgumentSorts(exp_found, _)) => { + Err(TypeError::ArgumentSorts(exp_found, i)) + } + Err(TypeError::Mutability | TypeError::ArgumentMutability(_)) => { + Err(TypeError::ArgumentMutability(i)) + } + r => r, + }); + Ok(ty::FnSig { + inputs_and_output: tcx.mk_type_list(inputs_and_output)?, + c_variadic: a.c_variadic, + unsafety, + abi, + }) + } +} + +impl<'tcx> Relate<'tcx> for ty::BoundConstness { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::BoundConstness, + b: ty::BoundConstness, + ) -> RelateResult<'tcx, ty::BoundConstness> { + if a != b { + Err(TypeError::ConstnessMismatch(expected_found(relation, a, b))) + } else { + Ok(a) + } + } +} + +impl<'tcx> Relate<'tcx> for ast::Unsafety { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ast::Unsafety, + b: ast::Unsafety, + ) -> RelateResult<'tcx, ast::Unsafety> { + if a != b { + Err(TypeError::UnsafetyMismatch(expected_found(relation, a, b))) + } else { + Ok(a) + } + } +} + +impl<'tcx> Relate<'tcx> for abi::Abi { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: abi::Abi, + b: abi::Abi, + ) -> RelateResult<'tcx, abi::Abi> { + if a == b { Ok(a) } else { Err(TypeError::AbiMismatch(expected_found(relation, a, b))) } + } +} + +impl<'tcx> Relate<'tcx> for ty::ProjectionTy<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ProjectionTy<'tcx>, + b: ty::ProjectionTy<'tcx>, + ) -> RelateResult<'tcx, ty::ProjectionTy<'tcx>> { + if a.item_def_id != b.item_def_id { + Err(TypeError::ProjectionMismatched(expected_found( + relation, + a.item_def_id, + b.item_def_id, + ))) + } else { + let substs = relation.relate(a.substs, b.substs)?; + Ok(ty::ProjectionTy { item_def_id: a.item_def_id, substs: &substs }) + } + } +} + +impl<'tcx> Relate<'tcx> for ty::ExistentialProjection<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ExistentialProjection<'tcx>, + b: ty::ExistentialProjection<'tcx>, + ) -> RelateResult<'tcx, ty::ExistentialProjection<'tcx>> { + if a.item_def_id != b.item_def_id { + Err(TypeError::ProjectionMismatched(expected_found( + relation, + a.item_def_id, + b.item_def_id, + ))) + } else { + let term = relation.relate_with_variance( + ty::Invariant, + ty::VarianceDiagInfo::default(), + a.term, + b.term, + )?; + let substs = relation.relate_with_variance( + ty::Invariant, + ty::VarianceDiagInfo::default(), + a.substs, + b.substs, + )?; + Ok(ty::ExistentialProjection { item_def_id: a.item_def_id, substs, term }) + } + } +} + +impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::TraitRef<'tcx>, + b: ty::TraitRef<'tcx>, + ) -> RelateResult<'tcx, ty::TraitRef<'tcx>> { + // Different traits cannot be related. + if a.def_id != b.def_id { + Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id))) + } else { + let substs = relate_substs(relation, a.substs, b.substs)?; + Ok(ty::TraitRef { def_id: a.def_id, substs }) + } + } +} + +impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ExistentialTraitRef<'tcx>, + b: ty::ExistentialTraitRef<'tcx>, + ) -> RelateResult<'tcx, ty::ExistentialTraitRef<'tcx>> { + // Different traits cannot be related. + if a.def_id != b.def_id { + Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id))) + } else { + let substs = relate_substs(relation, a.substs, b.substs)?; + Ok(ty::ExistentialTraitRef { def_id: a.def_id, substs }) + } + } +} + +#[derive(Copy, Debug, Clone, TypeFoldable, TypeVisitable)] +struct GeneratorWitness<'tcx>(&'tcx ty::List<Ty<'tcx>>); + +impl<'tcx> Relate<'tcx> for GeneratorWitness<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: GeneratorWitness<'tcx>, + b: GeneratorWitness<'tcx>, + ) -> RelateResult<'tcx, GeneratorWitness<'tcx>> { + assert_eq!(a.0.len(), b.0.len()); + let tcx = relation.tcx(); + let types = tcx.mk_type_list(iter::zip(a.0, b.0).map(|(a, b)| relation.relate(a, b)))?; + Ok(GeneratorWitness(types)) + } +} + +impl<'tcx> Relate<'tcx> for ImplSubject<'tcx> { + #[inline] + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ImplSubject<'tcx>, + b: ImplSubject<'tcx>, + ) -> RelateResult<'tcx, ImplSubject<'tcx>> { + match (a, b) { + (ImplSubject::Trait(trait_ref_a), ImplSubject::Trait(trait_ref_b)) => { + let trait_ref = ty::TraitRef::relate(relation, trait_ref_a, trait_ref_b)?; + Ok(ImplSubject::Trait(trait_ref)) + } + (ImplSubject::Inherent(ty_a), ImplSubject::Inherent(ty_b)) => { + let ty = Ty::relate(relation, ty_a, ty_b)?; + Ok(ImplSubject::Inherent(ty)) + } + (ImplSubject::Trait(_), ImplSubject::Inherent(_)) + | (ImplSubject::Inherent(_), ImplSubject::Trait(_)) => { + bug!("can not relate TraitRef and Ty"); + } + } + } +} + +impl<'tcx> Relate<'tcx> for Ty<'tcx> { + #[inline] + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: Ty<'tcx>, + b: Ty<'tcx>, + ) -> RelateResult<'tcx, Ty<'tcx>> { + relation.tys(a, b) + } +} + +/// The main "type relation" routine. Note that this does not handle +/// inference artifacts, so you should filter those out before calling +/// it. +pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>( + relation: &mut R, + a: Ty<'tcx>, + b: Ty<'tcx>, +) -> RelateResult<'tcx, Ty<'tcx>> { + let tcx = relation.tcx(); + debug!("super_relate_tys: a={:?} b={:?}", a, b); + match (a.kind(), b.kind()) { + (&ty::Infer(_), _) | (_, &ty::Infer(_)) => { + // The caller should handle these cases! + bug!("var types encountered in super_relate_tys") + } + + (ty::Bound(..), _) | (_, ty::Bound(..)) => { + bug!("bound types encountered in super_relate_tys") + } + + (&ty::Error(_), _) | (_, &ty::Error(_)) => Ok(tcx.ty_error()), + + (&ty::Never, _) + | (&ty::Char, _) + | (&ty::Bool, _) + | (&ty::Int(_), _) + | (&ty::Uint(_), _) + | (&ty::Float(_), _) + | (&ty::Str, _) + if a == b => + { + Ok(a) + } + + (&ty::Param(ref a_p), &ty::Param(ref b_p)) if a_p.index == b_p.index => Ok(a), + + (ty::Placeholder(p1), ty::Placeholder(p2)) if p1 == p2 => Ok(a), + + (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) if a_def == b_def => { + let substs = relation.relate_item_substs(a_def.did(), a_substs, b_substs)?; + Ok(tcx.mk_adt(a_def, substs)) + } + + (&ty::Foreign(a_id), &ty::Foreign(b_id)) if a_id == b_id => Ok(tcx.mk_foreign(a_id)), + + (&ty::Dynamic(a_obj, a_region), &ty::Dynamic(b_obj, b_region)) => { + let region_bound = relation.with_cause(Cause::ExistentialRegionBound, |relation| { + relation.relate_with_variance( + ty::Contravariant, + ty::VarianceDiagInfo::default(), + a_region, + b_region, + ) + })?; + Ok(tcx.mk_dynamic(relation.relate(a_obj, b_obj)?, region_bound)) + } + + (&ty::Generator(a_id, a_substs, movability), &ty::Generator(b_id, b_substs, _)) + if a_id == b_id => + { + // All Generator types with the same id represent + // the (anonymous) type of the same generator expression. So + // all of their regions should be equated. + let substs = relation.relate(a_substs, b_substs)?; + Ok(tcx.mk_generator(a_id, substs, movability)) + } + + (&ty::GeneratorWitness(a_types), &ty::GeneratorWitness(b_types)) => { + // Wrap our types with a temporary GeneratorWitness struct + // inside the binder so we can related them + let a_types = a_types.map_bound(GeneratorWitness); + let b_types = b_types.map_bound(GeneratorWitness); + // Then remove the GeneratorWitness for the result + let types = relation.relate(a_types, b_types)?.map_bound(|witness| witness.0); + Ok(tcx.mk_generator_witness(types)) + } + + (&ty::Closure(a_id, a_substs), &ty::Closure(b_id, b_substs)) if a_id == b_id => { + // All Closure types with the same id represent + // the (anonymous) type of the same closure expression. So + // all of their regions should be equated. + let substs = relation.relate(a_substs, b_substs)?; + Ok(tcx.mk_closure(a_id, &substs)) + } + + (&ty::RawPtr(a_mt), &ty::RawPtr(b_mt)) => { + let mt = relate_type_and_mut(relation, a_mt, b_mt, a)?; + Ok(tcx.mk_ptr(mt)) + } + + (&ty::Ref(a_r, a_ty, a_mutbl), &ty::Ref(b_r, b_ty, b_mutbl)) => { + let r = relation.relate_with_variance( + ty::Contravariant, + ty::VarianceDiagInfo::default(), + a_r, + b_r, + )?; + let a_mt = ty::TypeAndMut { ty: a_ty, mutbl: a_mutbl }; + let b_mt = ty::TypeAndMut { ty: b_ty, mutbl: b_mutbl }; + let mt = relate_type_and_mut(relation, a_mt, b_mt, a)?; + Ok(tcx.mk_ref(r, mt)) + } + + (&ty::Array(a_t, sz_a), &ty::Array(b_t, sz_b)) => { + let t = relation.relate(a_t, b_t)?; + match relation.relate(sz_a, sz_b) { + Ok(sz) => Ok(tcx.mk_ty(ty::Array(t, sz))), + Err(err) => { + // Check whether the lengths are both concrete/known values, + // but are unequal, for better diagnostics. + // + // It might seem dubious to eagerly evaluate these constants here, + // we however cannot end up with errors in `Relate` during both + // `type_of` and `predicates_of`. This means that evaluating the + // constants should not cause cycle errors here. + let sz_a = sz_a.try_eval_usize(tcx, relation.param_env()); + let sz_b = sz_b.try_eval_usize(tcx, relation.param_env()); + match (sz_a, sz_b) { + (Some(sz_a_val), Some(sz_b_val)) if sz_a_val != sz_b_val => Err( + TypeError::FixedArraySize(expected_found(relation, sz_a_val, sz_b_val)), + ), + _ => Err(err), + } + } + } + } + + (&ty::Slice(a_t), &ty::Slice(b_t)) => { + let t = relation.relate(a_t, b_t)?; + Ok(tcx.mk_slice(t)) + } + + (&ty::Tuple(as_), &ty::Tuple(bs)) => { + if as_.len() == bs.len() { + Ok(tcx.mk_tup(iter::zip(as_, bs).map(|(a, b)| relation.relate(a, b)))?) + } else if !(as_.is_empty() || bs.is_empty()) { + Err(TypeError::TupleSize(expected_found(relation, as_.len(), bs.len()))) + } else { + Err(TypeError::Sorts(expected_found(relation, a, b))) + } + } + + (&ty::FnDef(a_def_id, a_substs), &ty::FnDef(b_def_id, b_substs)) + if a_def_id == b_def_id => + { + let substs = relation.relate_item_substs(a_def_id, a_substs, b_substs)?; + Ok(tcx.mk_fn_def(a_def_id, substs)) + } + + (&ty::FnPtr(a_fty), &ty::FnPtr(b_fty)) => { + let fty = relation.relate(a_fty, b_fty)?; + Ok(tcx.mk_fn_ptr(fty)) + } + + // these two are already handled downstream in case of lazy normalization + (&ty::Projection(a_data), &ty::Projection(b_data)) => { + let projection_ty = relation.relate(a_data, b_data)?; + Ok(tcx.mk_projection(projection_ty.item_def_id, projection_ty.substs)) + } + + (&ty::Opaque(a_def_id, a_substs), &ty::Opaque(b_def_id, b_substs)) + if a_def_id == b_def_id => + { + let substs = relate_substs(relation, a_substs, b_substs)?; + Ok(tcx.mk_opaque(a_def_id, substs)) + } + + _ => Err(TypeError::Sorts(expected_found(relation, a, b))), + } +} + +/// The main "const relation" routine. Note that this does not handle +/// inference artifacts, so you should filter those out before calling +/// it. +pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::Const<'tcx>, + b: ty::Const<'tcx>, +) -> RelateResult<'tcx, ty::Const<'tcx>> { + debug!("{}.super_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b); + let tcx = relation.tcx(); + + let a_ty; + let b_ty; + if relation.tcx().features().adt_const_params { + a_ty = tcx.normalize_erasing_regions(relation.param_env(), a.ty()); + b_ty = tcx.normalize_erasing_regions(relation.param_env(), b.ty()); + } else { + a_ty = tcx.erase_regions(a.ty()); + b_ty = tcx.erase_regions(b.ty()); + } + if a_ty != b_ty { + relation.tcx().sess.delay_span_bug( + DUMMY_SP, + &format!("cannot relate constants of different types: {} != {}", a_ty, b_ty), + ); + } + + let eagerly_eval = |x: ty::Const<'tcx>| x.eval(tcx, relation.param_env()); + let a = eagerly_eval(a); + let b = eagerly_eval(b); + + // Currently, the values that can be unified are primitive types, + // and those that derive both `PartialEq` and `Eq`, corresponding + // to structural-match types. + let is_match = match (a.kind(), b.kind()) { + (ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => { + // The caller should handle these cases! + bug!("var types encountered in super_relate_consts: {:?} {:?}", a, b) + } + + (ty::ConstKind::Error(_), _) => return Ok(a), + (_, ty::ConstKind::Error(_)) => return Ok(b), + + (ty::ConstKind::Param(a_p), ty::ConstKind::Param(b_p)) => a_p.index == b_p.index, + (ty::ConstKind::Placeholder(p1), ty::ConstKind::Placeholder(p2)) => p1 == p2, + (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val, + + (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu)) + if tcx.features().generic_const_exprs => + { + tcx.try_unify_abstract_consts(relation.param_env().and((au.shrink(), bu.shrink()))) + } + + // While this is slightly incorrect, it shouldn't matter for `min_const_generics` + // and is the better alternative to waiting until `generic_const_exprs` can + // be stabilized. + (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu)) + if au.def == bu.def && au.promoted == bu.promoted => + { + let substs = relation.relate_with_variance( + ty::Variance::Invariant, + ty::VarianceDiagInfo::default(), + au.substs, + bu.substs, + )?; + return Ok(tcx.mk_const(ty::ConstS { + kind: ty::ConstKind::Unevaluated(ty::Unevaluated { + def: au.def, + substs, + promoted: au.promoted, + }), + ty: a.ty(), + })); + } + _ => false, + }; + if is_match { Ok(a) } else { Err(TypeError::ConstMismatch(expected_found(relation, a, b))) } +} + +impl<'tcx> Relate<'tcx> for &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: Self, + b: Self, + ) -> RelateResult<'tcx, Self> { + let tcx = relation.tcx(); + + // FIXME: this is wasteful, but want to do a perf run to see how slow it is. + // We need to perform this deduplication as we sometimes generate duplicate projections + // in `a`. + let mut a_v: Vec<_> = a.into_iter().collect(); + let mut b_v: Vec<_> = b.into_iter().collect(); + // `skip_binder` here is okay because `stable_cmp` doesn't look at binders + a_v.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder())); + a_v.dedup(); + b_v.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder())); + b_v.dedup(); + if a_v.len() != b_v.len() { + return Err(TypeError::ExistentialMismatch(expected_found(relation, a, b))); + } + + let v = iter::zip(a_v, b_v).map(|(ep_a, ep_b)| { + use crate::ty::ExistentialPredicate::*; + match (ep_a.skip_binder(), ep_b.skip_binder()) { + (Trait(a), Trait(b)) => Ok(ep_a + .rebind(Trait(relation.relate(ep_a.rebind(a), ep_b.rebind(b))?.skip_binder()))), + (Projection(a), Projection(b)) => Ok(ep_a.rebind(Projection( + relation.relate(ep_a.rebind(a), ep_b.rebind(b))?.skip_binder(), + ))), + (AutoTrait(a), AutoTrait(b)) if a == b => Ok(ep_a.rebind(AutoTrait(a))), + _ => Err(TypeError::ExistentialMismatch(expected_found(relation, a, b))), + } + }); + tcx.mk_poly_existential_predicates(v) + } +} + +impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ClosureSubsts<'tcx>, + b: ty::ClosureSubsts<'tcx>, + ) -> RelateResult<'tcx, ty::ClosureSubsts<'tcx>> { + let substs = relate_substs(relation, a.substs, b.substs)?; + Ok(ty::ClosureSubsts { substs }) + } +} + +impl<'tcx> Relate<'tcx> for ty::GeneratorSubsts<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::GeneratorSubsts<'tcx>, + b: ty::GeneratorSubsts<'tcx>, + ) -> RelateResult<'tcx, ty::GeneratorSubsts<'tcx>> { + let substs = relate_substs(relation, a.substs, b.substs)?; + Ok(ty::GeneratorSubsts { substs }) + } +} + +impl<'tcx> Relate<'tcx> for SubstsRef<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: SubstsRef<'tcx>, + b: SubstsRef<'tcx>, + ) -> RelateResult<'tcx, SubstsRef<'tcx>> { + relate_substs(relation, a, b) + } +} + +impl<'tcx> Relate<'tcx> for ty::Region<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::Region<'tcx>, + b: ty::Region<'tcx>, + ) -> RelateResult<'tcx, ty::Region<'tcx>> { + relation.regions(a, b) + } +} + +impl<'tcx> Relate<'tcx> for ty::Const<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::Const<'tcx>, + b: ty::Const<'tcx>, + ) -> RelateResult<'tcx, ty::Const<'tcx>> { + relation.consts(a, b) + } +} + +impl<'tcx, T: Relate<'tcx>> Relate<'tcx> for ty::Binder<'tcx, T> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::Binder<'tcx, T>, + b: ty::Binder<'tcx, T>, + ) -> RelateResult<'tcx, ty::Binder<'tcx, T>> { + relation.binders(a, b) + } +} + +impl<'tcx> Relate<'tcx> for GenericArg<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: GenericArg<'tcx>, + b: GenericArg<'tcx>, + ) -> RelateResult<'tcx, GenericArg<'tcx>> { + match (a.unpack(), b.unpack()) { + (GenericArgKind::Lifetime(a_lt), GenericArgKind::Lifetime(b_lt)) => { + Ok(relation.relate(a_lt, b_lt)?.into()) + } + (GenericArgKind::Type(a_ty), GenericArgKind::Type(b_ty)) => { + Ok(relation.relate(a_ty, b_ty)?.into()) + } + (GenericArgKind::Const(a_ct), GenericArgKind::Const(b_ct)) => { + Ok(relation.relate(a_ct, b_ct)?.into()) + } + (GenericArgKind::Lifetime(unpacked), x) => { + bug!("impossible case reached: can't relate: {:?} with {:?}", unpacked, x) + } + (GenericArgKind::Type(unpacked), x) => { + bug!("impossible case reached: can't relate: {:?} with {:?}", unpacked, x) + } + (GenericArgKind::Const(unpacked), x) => { + bug!("impossible case reached: can't relate: {:?} with {:?}", unpacked, x) + } + } + } +} + +impl<'tcx> Relate<'tcx> for ty::ImplPolarity { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ImplPolarity, + b: ty::ImplPolarity, + ) -> RelateResult<'tcx, ty::ImplPolarity> { + if a != b { + Err(TypeError::PolarityMismatch(expected_found(relation, a, b))) + } else { + Ok(a) + } + } +} + +impl<'tcx> Relate<'tcx> for ty::TraitPredicate<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::TraitPredicate<'tcx>, + b: ty::TraitPredicate<'tcx>, + ) -> RelateResult<'tcx, ty::TraitPredicate<'tcx>> { + Ok(ty::TraitPredicate { + trait_ref: relation.relate(a.trait_ref, b.trait_ref)?, + constness: relation.relate(a.constness, b.constness)?, + polarity: relation.relate(a.polarity, b.polarity)?, + }) + } +} + +impl<'tcx> Relate<'tcx> for ty::Term<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: Self, + b: Self, + ) -> RelateResult<'tcx, Self> { + Ok(match (a, b) { + (Term::Ty(a), Term::Ty(b)) => relation.relate(a, b)?.into(), + (Term::Const(a), Term::Const(b)) => relation.relate(a, b)?.into(), + _ => return Err(TypeError::Mismatch), + }) + } +} + +impl<'tcx> Relate<'tcx> for ty::ProjectionPredicate<'tcx> { + fn relate<R: TypeRelation<'tcx>>( + relation: &mut R, + a: ty::ProjectionPredicate<'tcx>, + b: ty::ProjectionPredicate<'tcx>, + ) -> RelateResult<'tcx, ty::ProjectionPredicate<'tcx>> { + Ok(ty::ProjectionPredicate { + projection_ty: relation.relate(a.projection_ty, b.projection_ty)?, + term: relation.relate(a.term, b.term)?, + }) + } +} + +/////////////////////////////////////////////////////////////////////////// +// Error handling + +pub fn expected_found<'tcx, R, T>(relation: &mut R, a: T, b: T) -> ExpectedFound<T> +where + R: TypeRelation<'tcx>, +{ + ExpectedFound::new(relation.a_is_expected(), a, b) +} |