Add dropLast to tests and parser

compiler/test_gen/src/gen_list.rs

@@ -235,6 +235,38 @@ fn list_drop_at_mutable() {
     );
 }
 
+#[test]
+fn list_drop_last() {
+    assert_evals_to!(
+        "List.dropLast [1, 2, 3]",
+        RocList::from_slice(&[1, 2]),
+        RocList<i64>
+    );
+    assert_evals_to!("List.dropLast []", RocList::from_slice(&[]), RocList<i64>);
+    assert_evals_to!("List.dropLast [0]", RocList::from_slice(&[]), RocList<i64>);
+}
+
+#[test]
+fn list_drop_last_mutable() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+               list : List I64
+               list = [ if True then 4 else 4, 5, 6 ]
+
+               { newList: List.dropLast list, original: list }
+               "#
+        ),
+        (
+            // new_list
+            RocList::from_slice(&[4, 5]),
+            // original
+            RocList::from_slice(&[4, 5, 6]),
+        ),
+        (RocList<i64>, RocList<i64>,)
+    );
+}
+
 #[test]
 fn list_swap() {
     assert_evals_to!("List.swap [] 0 1", RocList::from_slice(&[]), RocList<i64>);