Ensure cloned interner can still look up the same symbols (#34)

Author: alamb

src/interner.rs

@@ -82,12 +82,12 @@ impl<S, B, H> Clone for StringInterner<S, B, H>
 where
     S: Symbol,
     B: Backend<S> + Clone,
-    H: BuildHasher + Default,
+    H: BuildHasher + Clone,
 {
     fn clone(&self) -> Self {
         Self {
             dedup: self.dedup.clone(),
-            hasher: Default::default(),
+            hasher: self.hasher.clone(),
             backend: self.backend.clone(),
         }
     }

src/tests.rs

@@ -102,9 +102,13 @@ macro_rules! gen_tests_for_backend {
 
         #[test]
         fn clone_works() {
-            let interner = StringInterner::new();
-            let cloned = interner.clone();
+            let mut interner = StringInterner::new();
+            assert_eq!(interner.get_or_intern("a").to_usize(), 0);
+
+            let mut cloned = interner.clone();
             assert_eq!(interner, cloned);
+            // And the clone should have the same interned values
+            assert_eq!(cloned.get_or_intern("a").to_usize(), 0);
         }
 
         #[test]