remove unused function shift_out_to_binders

Author: nikomatsakis

chalk-ir/src/lib.rs

@@ -494,30 +494,6 @@ impl DebruijnIndex {
             Some(DebruijnIndex::from(self.as_usize() - amount))
         }
     }
-
-    /// Adjusts any De Bruijn indices so as to make `to_binder` the
-    /// innermost binder. That is, if we have something bound at `to_binder`,
-    /// it will now be bound at INNERMOST. This is an appropriate thing to do
-    /// when moving a region out from inside binders:
-    ///
-    /// ```ignore
-    ///             for<'a>   fn(for<'b>   for<'c>   fn(&'a u32), _)
-    /// // Binder:  D3           D2        D1            ^^
-    /// ```
-    ///
-    /// Here, the region `'a` would have the De Bruijn index D3,
-    /// because it is the bound 3 binders out. However, if we wanted
-    /// to refer to that region `'a` in the second argument (the `_`),
-    /// those two binders would not be in scope. In that case, we
-    /// might invoke `shift_out_to_binder(D3)`. This would adjust the
-    /// De Bruijn index of `'a` to D1 (the innermost binder).
-    ///
-    /// If we invoke `shift_out_to_binder` and the region is in fact
-    /// bound by one of the binders we are shifting out of, that is an
-    /// error (and should fail an assertion failure).
-    pub fn shifted_out_to_binder(self, to_binder: DebruijnIndex) -> Option<Self> {
-        self.shifted_out_by(to_binder.as_usize() - Self::INNERMOST.as_usize())
-    }
 }
 
 /// A "DynTy" could be either a `dyn Trait` or an (opaque) `impl