Whoa, this seems weird. Do you have a test-case for it, because running `-Z ast-json` on

```rust
#![no_std]

mod bar {}
```

gives 

```json
{
  "module": {
    "view_items": [],
    "items": [
      {
        "ident": "bar",
        "attrs": [],
        "id": 1,
        "node": [
          "ItemMod",
          {
            "view_items": [],
            "items": []
          }
        ],
        "vis": "Inherited",
        "span": null
      }
    ]
  },
```

In particular, the inner `items` is empty. (`no_std` is just to avoid the `view_items` stuff that's inserted automatically, doesn't seem to change the output.)