1 files changed, 7 insertions, 280 deletions

diff --git a/crates/hir_ty/src/walk.rs b/crates/hir_ty/src/walk.rs
index 91116dcda..6ef1d5336 100644
--- a/crates/hir_ty/src/walk.rs
+++ b/crates/hir_ty/src/walk.rs
@@ -1,138 +1,17 @@
 //! The `TypeWalk` trait (probably to be replaced by Chalk's `Fold` and
 //! `Visit`).
 
-use std::mem;
-
-use chalk_ir::DebruijnIndex;
+use chalk_ir::interner::HasInterner;
 
 use crate::{
-    utils::make_mut_slice, AliasEq, AliasTy, Binders, CallableSig, FnSubst, GenericArg,
-    GenericArgData, Interner, OpaqueTy, ProjectionTy, Substitution, TraitRef, Ty, TyKind,
-    WhereClause,
+    AliasEq, AliasTy, Binders, CallableSig, FnSubst, GenericArg, GenericArgData, Interner,
+    OpaqueTy, ProjectionTy, Substitution, TraitRef, Ty, TyKind, WhereClause,
 };
 
 /// This allows walking structures that contain types to do something with those
 /// types, similar to Chalk's `Fold` trait.
 pub trait TypeWalk {
     fn walk(&self, f: &mut impl FnMut(&Ty));
-    fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        self.walk_mut_binders(&mut |ty, _binders| f(ty), DebruijnIndex::INNERMOST);
-    }
-    /// Walk the type, counting entered binders.
-    ///
-    /// `TyKind::Bound` variables use DeBruijn indexing, which means that 0 refers
-    /// to the innermost binder, 1 to the next, etc.. So when we want to
-    /// substitute a certain bound variable, we can't just walk the whole type
-    /// and blindly replace each instance of a certain index; when we 'enter'
-    /// things that introduce new bound variables, we have to keep track of
-    /// that. Currently, the only thing that introduces bound variables on our
-    /// side are `TyKind::Dyn` and `TyKind::Opaque`, which each introduce a bound
-    /// variable for the self type.
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    );
-
-    fn fold_binders(
-        mut self,
-        f: &mut impl FnMut(Ty, DebruijnIndex) -> Ty,
-        binders: DebruijnIndex,
-    ) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut_binders(
-            &mut |ty_mut, binders| {
-                let ty = mem::replace(ty_mut, TyKind::Error.intern(&Interner));
-                *ty_mut = f(ty, binders);
-            },
-            binders,
-        );
-        self
-    }
-
-    fn fold(mut self, f: &mut impl FnMut(Ty) -> Ty) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut(&mut |ty_mut| {
-            let ty = mem::replace(ty_mut, TyKind::Error.intern(&Interner));
-            *ty_mut = f(ty);
-        });
-        self
-    }
-
-    /// Substitutes `TyKind::Bound` vars with the given substitution.
-    fn subst_bound_vars(self, substs: &Substitution) -> Self
-    where
-        Self: Sized,
-    {
-        self.subst_bound_vars_at_depth(substs, DebruijnIndex::INNERMOST)
-    }
-
-    /// Substitutes `TyKind::Bound` vars with the given substitution.
-    fn subst_bound_vars_at_depth(mut self, substs: &Substitution, depth: DebruijnIndex) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut_binders(
-            &mut |ty, binders| {
-                if let &mut TyKind::BoundVar(bound) = ty.interned_mut() {
-                    if bound.debruijn >= binders {
-                        *ty = substs.interned()[bound.index]
-                            .assert_ty_ref(&Interner)
-                            .clone()
-                            .shifted_in_from(binders);
-                    }
-                }
-            },
-            depth,
-        );
-        self
-    }
-
-    fn shifted_in(self, _interner: &Interner) -> Self
-    where
-        Self: Sized,
-    {
-        self.shifted_in_from(DebruijnIndex::ONE)
-    }
-
-    /// Shifts up debruijn indices of `TyKind::Bound` vars by `n`.
-    fn shifted_in_from(self, n: DebruijnIndex) -> Self
-    where
-        Self: Sized,
-    {
-        self.fold_binders(
-            &mut |ty, binders| match ty.kind(&Interner) {
-                TyKind::BoundVar(bound) if bound.debruijn >= binders => {
-                    TyKind::BoundVar(bound.shifted_in_from(n)).intern(&Interner)
-                }
-                _ => ty,
-            },
-            DebruijnIndex::INNERMOST,
-        )
-    }
-
-    /// Shifts debruijn indices of `TyKind::Bound` vars out (down) by `n`.
-    fn shifted_out_to(self, n: DebruijnIndex) -> Option<Self>
-    where
-        Self: Sized + std::fmt::Debug,
-    {
-        Some(self.fold_binders(
-            &mut |ty, binders| {
-                match ty.kind(&Interner) {
-                    TyKind::BoundVar(bound) if bound.debruijn >= binders => {
-                        TyKind::BoundVar(bound.shifted_out_to(n).unwrap_or(bound.clone()))
-                            .intern(&Interner)
-                    }
-                    _ => ty,
-                }
-            },
-            DebruijnIndex::INNERMOST,
-        ))
-    }
 }
 
 impl TypeWalk for Ty {
@@ -174,45 +53,6 @@ impl TypeWalk for Ty {
         }
         f(self);
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self.interned_mut() {
-            TyKind::Alias(AliasTy::Projection(p_ty)) => {
-                p_ty.substitution.walk_mut_binders(f, binders);
-            }
-            TyKind::Dyn(dyn_ty) => {
-                for p in make_mut_slice(dyn_ty.bounds.skip_binders_mut().interned_mut()) {
-                    p.walk_mut_binders(f, binders.shifted_in());
-                }
-            }
-            TyKind::Alias(AliasTy::Opaque(o_ty)) => {
-                o_ty.substitution.walk_mut_binders(f, binders);
-            }
-            TyKind::Slice(ty)
-            | TyKind::Array(ty, _)
-            | TyKind::Ref(_, _, ty)
-            | TyKind::Raw(_, ty) => {
-                ty.walk_mut_binders(f, binders);
-            }
-            TyKind::Function(fn_pointer) => {
-                fn_pointer.substitution.0.walk_mut_binders(f, binders.shifted_in());
-            }
-            TyKind::Adt(_, substs)
-            | TyKind::FnDef(_, substs)
-            | TyKind::Tuple(_, substs)
-            | TyKind::OpaqueType(_, substs)
-            | TyKind::AssociatedType(_, substs)
-            | TyKind::Closure(.., substs) => {
-                substs.walk_mut_binders(f, binders);
-            }
-            _ => {}
-        }
-        f(self, binders);
-    }
 }
 
 impl<T: TypeWalk> TypeWalk for Vec<T> {
@@ -221,43 +61,18 @@ impl<T: TypeWalk> TypeWalk for Vec<T> {
             t.walk(f);
         }
     }
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in self {
-            t.walk_mut_binders(f, binders);
-        }
-    }
 }
 
 impl TypeWalk for OpaqueTy {
     fn walk(&self, f: &mut impl FnMut(&Ty)) {
         self.substitution.walk(f);
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
 }
 
 impl TypeWalk for ProjectionTy {
     fn walk(&self, f: &mut impl FnMut(&Ty)) {
         self.substitution.walk(f);
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
 }
 
 impl TypeWalk for AliasTy {
@@ -267,17 +82,6 @@ impl TypeWalk for AliasTy {
             AliasTy::Opaque(it) => it.walk(f),
         }
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self {
-            AliasTy::Projection(it) => it.walk_mut_binders(f, binders),
-            AliasTy::Opaque(it) => it.walk_mut_binders(f, binders),
-        }
-    }
 }
 
 impl TypeWalk for GenericArg {
@@ -286,18 +90,7 @@ impl TypeWalk for GenericArg {
             GenericArgData::Ty(ty) => {
                 ty.walk(f);
             }
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self.interned_mut() {
-            GenericArgData::Ty(ty) => {
-                ty.walk_mut_binders(f, binders);
-            }
+            _ => {}
         }
     }
 }
@@ -308,44 +101,18 @@ impl TypeWalk for Substitution {
             t.walk(f);
         }
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in self.interned_mut() {
-            t.walk_mut_binders(f, binders);
-        }
-    }
 }
 
-impl<T: TypeWalk> TypeWalk for Binders<T> {
+impl<T: TypeWalk + HasInterner<Interner = Interner>> TypeWalk for Binders<T> {
     fn walk(&self, f: &mut impl FnMut(&Ty)) {
         self.skip_binders().walk(f);
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.skip_binders_mut().walk_mut_binders(f, binders.shifted_in())
-    }
 }
 
 impl TypeWalk for TraitRef {
     fn walk(&self, f: &mut impl FnMut(&Ty)) {
         self.substitution.walk(f);
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
 }
 
 impl TypeWalk for WhereClause {
@@ -353,17 +120,7 @@ impl TypeWalk for WhereClause {
         match self {
             WhereClause::Implemented(trait_ref) => trait_ref.walk(f),
             WhereClause::AliasEq(alias_eq) => alias_eq.walk(f),
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self {
-            WhereClause::Implemented(trait_ref) => trait_ref.walk_mut_binders(f, binders),
-            WhereClause::AliasEq(alias_eq) => alias_eq.walk_mut_binders(f, binders),
+            _ => {}
         }
     }
 }
@@ -374,16 +131,6 @@ impl TypeWalk for CallableSig {
             t.walk(f);
         }
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in make_mut_slice(&mut self.params_and_return) {
-            t.walk_mut_binders(f, binders);
-        }
-    }
 }
 
 impl TypeWalk for AliasEq {
@@ -394,30 +141,10 @@ impl TypeWalk for AliasEq {
             AliasTy::Opaque(opaque) => opaque.walk(f),
         }
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.ty.walk_mut_binders(f, binders);
-        match &mut self.alias {
-            AliasTy::Projection(projection_ty) => projection_ty.walk_mut_binders(f, binders),
-            AliasTy::Opaque(opaque) => opaque.walk_mut_binders(f, binders),
-        }
-    }
 }
 
-impl TypeWalk for FnSubst {
+impl TypeWalk for FnSubst<Interner> {
     fn walk(&self, f: &mut impl FnMut(&Ty)) {
         self.0.walk(f)
     }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.0.walk_mut_binders(f, binders)
-    }
 }