refactor shared visitors

Author: basil-cow

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::{visitors::FindBound, SuperVisit, Visit, VisitResult, Visitor};
+use crate::visit::{SuperVisit, Visit, VisitExt, VisitResult, Visitor};
 use chalk_derive::{Fold, HasInterner, Visit};
 use chalk_engine::fallible::*;
 use std::iter;
@@ -234,8 +234,7 @@ 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 {
-        self.visit_with(&mut FindBound { interner }, DebruijnIndex::INNERMOST)
-            .found
+        self.has_free_vars(interner)
     }
 }
 

chalk-ir/src/visit.rs

@@ -10,6 +10,8 @@ mod binder_impls;
 mod boring_impls;
 pub mod visitors;
 
+pub use visitors::VisitExt;
+
 pub trait VisitResult: Sized {
     fn new() -> Self;
 

chalk-ir/src/visit/visitors.rs

@@ -1,10 +1,28 @@
-use crate::{BoundVar, DebruijnIndex, Interner, VisitResult, Visitor};
+use crate::{BoundVar, DebruijnIndex, Interner, Visit, VisitResult, Visitor};
+
+pub trait VisitExt<I: Interner>: Visit<I> {
+    fn has_free_vars(&self, interner: &I) -> bool {
+        self.visit_with(
+            &mut FindFreeVarsVisitor { interner },
+            DebruijnIndex::INNERMOST,
+        )
+        .to_bool()
+    }
+}
+
+impl<T, I: Interner> VisitExt<I> for T where T: Visit<I> {}
 
 #[derive(Clone, Copy, Debug)]
 pub struct FindAny {
     pub found: bool,
 }
 
+impl FindAny {
+    pub fn to_bool(&self) -> bool {
+        self.found
+    }
+}
+
 impl VisitResult for FindAny {
     fn new() -> Self {
         FindAny { found: false }
@@ -18,11 +36,11 @@ impl VisitResult for FindAny {
     }
 }
 
-pub struct FindBound<'i, I: Interner> {
+pub struct FindFreeVarsVisitor<'i, I: Interner> {
     pub interner: &'i I,
 }
 
-impl<'i, I: Interner> Visitor<'i, I> for FindBound<'i, I> {
+impl<'i, I: Interner> Visitor<'i, I> for FindFreeVarsVisitor<'i, I> {
     type Result = FindAny;
 
     fn as_dyn(&mut self) -> &mut dyn Visitor<'i, I, Result = Self::Result> {