{"ast_node_type":"variable","tokens":[{"end":87,"kind":"keyword","start":0,"text":"let"}]}
                    let vtable_entries_b = self.vtable_entries(data_b.principal(), ty);
                    // one vtable is a prefix of the other, so we double-check that.
                    assert!(&vtable_entries[..vtable_entries_b.len()] == vtable_entries_b);