//! 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::{self, Expr, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldable}; use crate::ty::{GenericArg, GenericArgKind, SubstsRef}; use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_target::spec::abi; use std::iter; pub type RelateResult<'tcx, T> = Result>; #[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(&mut self, _cause: Cause, f: F) -> R where F: FnOnce(&mut Self) -> R, { f(self) } /// Generic relation routine suitable for most anything. fn relate>(&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, true) } /// Switch variance for the purpose of relating `a` and `b`. fn relate_with_variance>( &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( &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> + PartialEq + Copy { fn relate>( 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 { hir::Mutability::Not => (ty::Covariant, ty::VarianceDiagInfo::None), hir::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_from_iter(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>, fetch_ty_for_diag: bool, ) -> 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 && fetch_ty_for_diag { let ty = *cached_ty.get_or_insert_with(|| tcx.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_from_iter(params) } impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> { fn relate>( 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_from_iter(inputs_and_output)?, c_variadic: a.c_variadic, unsafety, abi, }) } } impl<'tcx> Relate<'tcx> for ty::BoundConstness { fn relate>( 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 hir::Unsafety { fn relate>( relation: &mut R, a: hir::Unsafety, b: hir::Unsafety, ) -> RelateResult<'tcx, hir::Unsafety> { if a != b { Err(TypeError::UnsafetyMismatch(expected_found(relation, a, b))) } else { Ok(a) } } } impl<'tcx> Relate<'tcx> for abi::Abi { fn relate>( 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::AliasTy<'tcx> { fn relate>( relation: &mut R, a: ty::AliasTy<'tcx>, b: ty::AliasTy<'tcx>, ) -> RelateResult<'tcx, ty::AliasTy<'tcx>> { if a.def_id != b.def_id { Err(TypeError::ProjectionMismatched(expected_found(relation, a.def_id, b.def_id))) } else { let substs = relation.relate(a.substs, b.substs)?; Ok(relation.tcx().mk_alias_ty(a.def_id, substs)) } } } impl<'tcx> Relate<'tcx> for ty::ExistentialProjection<'tcx> { fn relate>( relation: &mut R, a: ty::ExistentialProjection<'tcx>, b: ty::ExistentialProjection<'tcx>, ) -> RelateResult<'tcx, ty::ExistentialProjection<'tcx>> { if a.def_id != b.def_id { Err(TypeError::ProjectionMismatched(expected_found(relation, a.def_id, b.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 { def_id: a.def_id, substs, term }) } } } impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> { fn relate>( 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::new(relation.tcx(), a.def_id, substs)) } } } impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> { fn relate>( 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(PartialEq, Copy, Debug, Clone, TypeFoldable, TypeVisitable)] struct GeneratorWitness<'tcx>(&'tcx ty::List>); impl<'tcx> Relate<'tcx> for GeneratorWitness<'tcx> { fn relate>( 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_from_iter(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>( 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>( relation: &mut R, a: Ty<'tcx>, b: Ty<'tcx>, ) -> RelateResult<'tcx, Ty<'tcx>> { relation.tys(a, b) } } /// Relates `a` and `b` structurally, calling the relation for all nested values. /// Any semantic equality, e.g. of projections, and inference variables have to be /// handled by the caller. pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>( relation: &mut R, a: Ty<'tcx>, b: Ty<'tcx>, ) -> RelateResult<'tcx, Ty<'tcx>> { let tcx = relation.tcx(); debug!("structurally_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 structurally_relate_tys") } (ty::Bound(..), _) | (_, ty::Bound(..)) => { bug!("bound types encountered in structurally_relate_tys") } (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error(guar)), (&ty::Never, _) | (&ty::Char, _) | (&ty::Bool, _) | (&ty::Int(_), _) | (&ty::Uint(_), _) | (&ty::Float(_), _) | (&ty::Str, _) if a == b => { Ok(a) } (ty::Param(a_p), ty::Param(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, a_repr), &ty::Dynamic(b_obj, b_region, b_repr)) if a_repr == b_repr => { let region_bound = relation.with_cause(Cause::ExistentialRegionBound, |relation| { relation.relate(a_region, b_region) })?; Ok(tcx.mk_dynamic(relation.relate(a_obj, b_obj)?, region_bound, a_repr)) } (&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::GeneratorWitnessMIR(a_id, a_substs), &ty::GeneratorWitnessMIR(b_id, b_substs)) if a_id == b_id => { // All GeneratorWitness 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_witness_mir(a_id, substs)) } (&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(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_array_with_const_len(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_target_usize(tcx, relation.param_env()); let sz_b = sz_b.try_eval_target_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_from_iter(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::Alias(ty::Projection, a_data), &ty::Alias(ty::Projection, b_data)) => { let projection_ty = relation.relate(a_data, b_data)?; Ok(tcx.mk_projection(projection_ty.def_id, projection_ty.substs)) } (&ty::Alias(ty::Inherent, a_data), &ty::Alias(ty::Inherent, b_data)) => { let alias_ty = relation.relate(a_data, b_data)?; Ok(tcx.mk_alias(ty::Inherent, tcx.mk_alias_ty(alias_ty.def_id, alias_ty.substs))) } ( &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, substs: a_substs, .. }), &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, substs: b_substs, .. }), ) if a_def_id == b_def_id => { let opt_variances = tcx.variances_of(a_def_id); let substs = relate_substs_with_variances( relation, a_def_id, opt_variances, a_substs, b_substs, false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle )?; Ok(tcx.mk_opaque(a_def_id, substs)) } _ => Err(TypeError::Sorts(expected_found(relation, a, b))), } } /// Relates `a` and `b` structurally, calling the relation for all nested values. /// Any semantic equality, e.g. of unevaluated consts, and inference variables have /// to be handled by the caller. /// /// FIXME: This is not totally structual, which probably should be fixed. /// See the HACKs below. pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>( relation: &mut R, mut a: ty::Const<'tcx>, mut b: ty::Const<'tcx>, ) -> RelateResult<'tcx, ty::Const<'tcx>> { debug!("{}.structurally_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b); let tcx = relation.tcx(); // HACK(const_generics): We still need to eagerly evaluate consts when // relating them because during `normalize_param_env_or_error`, // we may relate an evaluated constant in a obligation against // an unnormalized (i.e. unevaluated) const in the param-env. // FIXME(generic_const_exprs): Once we always lazily unify unevaluated constants // these `eval` calls can be removed. if !tcx.features().generic_const_exprs { a = a.eval(tcx, relation.param_env()); b = b.eval(tcx, relation.param_env()); } if tcx.features().generic_const_exprs { a = tcx.expand_abstract_consts(a); b = tcx.expand_abstract_consts(b); } debug!("{}.structurally_relate_consts(normed_a = {:?}, normed_b = {:?})", relation.tag(), a, 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 structurally_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, // 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 => { assert_eq!(a.ty(), b.ty()); let substs = relation.relate_with_variance( ty::Variance::Invariant, ty::VarianceDiagInfo::default(), au.substs, bu.substs, )?; return Ok(tcx.mk_const(ty::UnevaluatedConst { def: au.def, substs }, a.ty())); } // Before calling relate on exprs, it is necessary to ensure that the nested consts // have identical types. (ty::ConstKind::Expr(ae), ty::ConstKind::Expr(be)) => { let r = relation; // FIXME(generic_const_exprs): is it possible to relate two consts which are not identical // exprs? Should we care about that? // FIXME(generic_const_exprs): relating the `ty()`s is a little weird since it is supposed to // ICE If they mismatch. Unfortunately `ConstKind::Expr` is a little special and can be thought // of as being generic over the argument types, however this is implicit so these types don't get // related when we relate the substs of the item this const arg is for. let expr = match (ae, be) { (Expr::Binop(a_op, al, ar), Expr::Binop(b_op, bl, br)) if a_op == b_op => { r.relate(al.ty(), bl.ty())?; r.relate(ar.ty(), br.ty())?; Expr::Binop(a_op, r.consts(al, bl)?, r.consts(ar, br)?) } (Expr::UnOp(a_op, av), Expr::UnOp(b_op, bv)) if a_op == b_op => { r.relate(av.ty(), bv.ty())?; Expr::UnOp(a_op, r.consts(av, bv)?) } (Expr::Cast(ak, av, at), Expr::Cast(bk, bv, bt)) if ak == bk => { r.relate(av.ty(), bv.ty())?; Expr::Cast(ak, r.consts(av, bv)?, r.tys(at, bt)?) } (Expr::FunctionCall(af, aa), Expr::FunctionCall(bf, ba)) if aa.len() == ba.len() => { r.relate(af.ty(), bf.ty())?; let func = r.consts(af, bf)?; let mut related_args = Vec::with_capacity(aa.len()); for (a_arg, b_arg) in aa.iter().zip(ba.iter()) { related_args.push(r.consts(a_arg, b_arg)?); } let related_args = tcx.mk_const_list(&related_args); Expr::FunctionCall(func, related_args) } _ => return Err(TypeError::ConstMismatch(expected_found(r, a, b))), }; let kind = ty::ConstKind::Expr(expr); return Ok(tcx.mk_const(kind, 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> { fn relate>( 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_from_iter(v) } } impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> { fn relate>( 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>( 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>( 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>( 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>( 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>( 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>( 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>( 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>( 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 Term<'tcx> { fn relate>( relation: &mut R, a: Self, b: Self, ) -> RelateResult<'tcx, Self> { Ok(match (a.unpack(), b.unpack()) { (TermKind::Ty(a), TermKind::Ty(b)) => relation.relate(a, b)?.into(), (TermKind::Const(a), TermKind::Const(b)) => relation.relate(a, b)?.into(), _ => return Err(TypeError::Mismatch), }) } } impl<'tcx> Relate<'tcx> for ty::ProjectionPredicate<'tcx> { fn relate>( 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 where R: TypeRelation<'tcx>, { ExpectedFound::new(relation.a_is_expected(), a, b) }