Make values hashable

1 files changed, 13 insertions, 2 deletions

diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index 3e79afc1..1539b4af 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -1,6 +1,7 @@
 use std::cell::RefCell;
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 use std::fmt::{self, Debug, Formatter};
+use std::hash::{Hash, Hasher};
 use std::iter;
 use std::sync::Arc;
 
@@ -68,7 +69,7 @@ impl<'a> Scopes<'a> {
 #[derive(Default, Clone)]
 pub struct Scope {
     /// The mapping from names to slots.
-    values: HashMap<EcoString, Slot>,
+    values: BTreeMap<EcoString, Slot>,
 }
 
 impl Scope {
@@ -126,6 +127,16 @@ impl Scope {
     }
 }
 
+impl Hash for Scope {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.values.len().hash(state);
+        for (name, value) in self.values.iter() {
+            name.hash(state);
+            value.borrow().hash(state);
+        }
+    }
+}
+
 impl Debug for Scope {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         f.write_str("Scope ")?;