implement primop (filter)

fix-vm/src/instructions/collections.rs

@@ -1,6 +1,6 @@
 use fix_common::StringId;
 use fix_error::Error;
-use gc_arena::Gc;
+use gc_arena::{Gc, RefLock};
 use smallvec::SmallVec;
 
 use crate::value::NixType;
@@ -298,7 +298,12 @@ impl<'gc> crate::Vm<'gc> {
         for _ in 0..count {
             items.push(reader.read_operand_data(ctx).resolve(mc, self));
         }
-        let list = Gc::new(mc, List { inner: items });
+        let list = Gc::new(
+            mc,
+            List {
+                inner: RefLock::new(items),
+            },
+        );
         self.push(Value::new_gc(list));
         Step::Continue(())
     }