change needs_shift to use visitor

Author: basil-cow

chalk-derive/src/lib.rs

@@ -356,7 +356,7 @@ pub fn derive_visit(item: TokenStream) -> TokenStream {
         // Hardcoded interner:
         //
         // impl Visit<ChalkIr> for Type {
-        // 
+        //
         // }
         let arg = attr
             .parse_args::<proc_macro2::TokenStream>()
@@ -369,8 +369,8 @@ pub fn derive_visit(item: TokenStream) -> TokenStream {
                     visitor: &mut dyn Visitor < 'i, #arg, Result = R >,
                     outer_binder: DebruijnIndex,
                 ) -> R
-                where 
-                    I: 'i 
+                where
+                    I: 'i
                 {
                     #body
                 }
@@ -404,9 +404,9 @@ pub fn derive_visit(item: TokenStream) -> TokenStream {
         // }
 
         let mut impl_generics = input.generics.clone();
-        impl_generics.params.extend(vec![
-            GenericParam::Type(syn::parse(quote! { _I: Interner }.into()).unwrap()),
-        ]);
+        impl_generics.params.extend(vec![GenericParam::Type(
+            syn::parse(quote! { _I: Interner }.into()).unwrap(),
+        )]);
 
         let mut where_clause = where_clause_ref
             .cloned()
@@ -524,4 +524,4 @@ fn derive_visit_body(type_name: &Ident, data: Data) -> proc_macro2::TokenStream
         }
         Data::Union(..) => panic!("Visit can not be derived for unions"),
     }
-}
+}

chalk-ir/src/lib.rs

@@ -3,7 +3,7 @@
 use crate::cast::{Cast, CastTo};
 use crate::fold::shift::Shift;
 use crate::fold::{Fold, Folder, Subst, SuperFold};
-use crate::visit::{VisitResult, Visit, SuperVisit, Visitor};
+use crate::visit::{visitors::FindBound, SuperVisit, Visit, VisitResult, Visitor};
 use chalk_derive::{Fold, HasInterner, Visit};
 use chalk_engine::fallible::*;
 use std::iter;
@@ -237,8 +237,8 @@ impl<I: Interner> Ty<I> {
     /// needs to be shifted across binders. This is a very inefficient
     /// check, intended only for debug assertions, because I am lazy.
     pub fn needs_shift(&self, interner: &I) -> bool {
-        let ty = self.clone();
-        ty != ty.shifted_in(interner)
+        self.visit_with(&mut FindBound { interner }, DebruijnIndex::INNERMOST)
+            .found
     }
 }
 

chalk-ir/src/visit.rs

@@ -8,24 +8,24 @@ use crate::{
 
 mod binder_impls;
 mod boring_impls;
+pub mod visitors;
 
 pub trait VisitResult: Sized {
     fn new() -> Self;
 
     fn and_then(self, op: impl FnOnce() -> Self) -> Self;
 }
 
-
 impl VisitResult for () {
     fn new() -> () {}
-    fn and_then(self, op: impl FnOnce() -> () ) -> () {
+    fn and_then(self, op: impl FnOnce() -> ()) -> () {
         op()
     }
 }
 
 /// A "visitor" recursively folds some term -- that is, some bit of IR,
-/// such as a `Goal`, and computes a value as a result. 
-/// 
+/// such as a `Goal`, and computes a value as a result.
+///
 ///
 /// To **apply** a visitor, use the `Visit::visit_with` method, like so
 ///
@@ -34,7 +34,7 @@ impl VisitResult for () {
 /// ```
 pub trait Visitor<'i, I: Interner>
 where
-I: 'i
+    I: 'i,
 {
     type Result: VisitResult;
 
@@ -219,7 +219,9 @@ pub trait Visit<I: Interner>: Debug {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i;
+    ) -> R
+    where
+        I: 'i;
 }
 
 /// For types where "visit" invokes a callback on the `visitor`, the
@@ -230,7 +232,9 @@ pub trait SuperVisit<I: Interner>: Visit<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i;
+    ) -> R
+    where
+        I: 'i;
 }
 
 /// "visiting" a type invokes the `visit_ty` method on the visitor; this
@@ -241,7 +245,10 @@ impl<I: Interner> Visit<I> for Ty<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         visitor.visit_ty(self, outer_binder)
     }
 }
@@ -255,7 +262,10 @@ where
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         let interner = visitor.interner();
         match self.data(interner) {
             TyData::BoundVar(bound_var) => {
@@ -280,7 +290,10 @@ impl<I: Interner> Visit<I> for Lifetime<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         visitor.visit_lifetime(self, outer_binder)
     }
 }
@@ -290,7 +303,10 @@ impl<I: Interner> SuperVisit<I> for Lifetime<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         let interner = visitor.interner();
         match self.data(interner) {
             LifetimeData::BoundVar(bound_var) => {
@@ -314,7 +330,10 @@ impl<I: Interner> Visit<I> for Goal<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         visitor.visit_goal(self, outer_binder)
     }
 }
@@ -324,7 +343,10 @@ impl<I: Interner> SuperVisit<I> for Goal<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         let interner = visitor.interner();
         self.data(interner).visit_with(visitor, outer_binder)
     }
@@ -335,7 +357,10 @@ impl<I: Interner> Visit<I> for ProgramClause<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         visitor.visit_program_clause(self, outer_binder)
     }
 }

chalk-ir/src/visit/binder_impls.rs

@@ -10,7 +10,10 @@ impl<I: Interner> Visit<I> for Fn<I> {
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         self.parameters
             .visit_with(visitor, outer_binder.shifted_in())
     }
@@ -24,7 +27,10 @@ where
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         self.value.visit_with(visitor, outer_binder.shifted_in())
     }
 }
@@ -38,7 +44,10 @@ where
         &self,
         visitor: &mut dyn Visitor<'i, I, Result = R>,
         outer_binder: DebruijnIndex,
-    ) -> R where I: 'i {
+    ) -> R
+    where
+        I: 'i,
+    {
         self.value.visit_with(visitor, outer_binder.shifted_in())
     }
 }