Use Rc instead of Box in AST to allow structural sharing

Closes #29

1 files changed, 1 insertions, 0 deletions

diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index c49d313..40112f1 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -2,6 +2,7 @@
 use dhall_core::core::*;
 use dhall_generator::dhall_expr;
 use std::fmt;
+use std::rc::Rc;
 
 /// Reduce an expression to its weak head normal form, i.e. normalize
 /// just enough to get the first constructor of the final expression