Expressions
diff --git a/src/ty.rs b/src/ty.rs
index e87f740..cdfa697 100644
--- a/src/ty.rs
+++ b/src/ty.rs
@@ -40,7 +40,7 @@
     pub mutability: Mutability,
 }
 
-#[derive(Debug, Clone, Eq, PartialEq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum Mutability {
     Mutable,
     Immutable,