Simplify a bit

1 files changed, 16 insertions, 0 deletions

diff --git a/dhall/src/semantics/core/var.rs b/dhall/src/semantics/core/var.rs
index a110632..7c2c4de 100644
--- a/dhall/src/semantics/core/var.rs
+++ b/dhall/src/semantics/core/var.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use crate::syntax::{Label, V};
 
 /// Stores a pair of variables: a normal one and one
@@ -38,6 +40,20 @@ impl AlphaVar {
         // Can't fail since delta is positive
         self.shift(1, &x.into()).unwrap()
     }
+    pub(crate) fn under_multiple_binders(
+        &self,
+        shift_map: &HashMap<Label, usize>,
+    ) -> Self
+    where
+        Self: Clone,
+    {
+        let mut v = self.clone();
+        for (x, n) in shift_map {
+            // Can't fail since delta is positive
+            v = v.shift(*n as isize, &x.into()).unwrap();
+        }
+        v
+    }
 }
 
 impl Binder {