Rustdoc-Json: Pub mod in private mod adds both to index

[aDotInTheVoid]

#![feature(no_core)]
#![no_core]

mod m1 {
    pub mod m2{}
}

Produces

{
  "crate_version": null,
  "external_crates": {},
  "format_version": 18,
  "includes_private": false,
  "index": {
    "0:0:1567": {
      "crate_id": 0,
      "id": "0:0:1567",
      "inner": {"is_crate": true, "is_stripped": false, "items": []},
      "kind": "module",
      "name": "bug"
    },
    "0:1:1565": {
      "crate_id": 0,
      "id": "0:1:1565",
      "inner": {"is_crate": false, "is_stripped": true, "items": ["0:2:1566"]},
      "kind": "module",
      "name": "m1"
    },
    "0:2:1566": {
      "crate_id": 0,
      "id": "0:2:1566",
      "inner": {"is_crate": false, "is_stripped": false, "items": []},
      "kind": "module",
      "name": "m2"
    }
  },
  "root": "0:0:1567"
}

@rustbot modify labels: +A-rustdoc-json +T-rustdoc

[aDotInTheVoid]

Interestingly, if the inner item is a pub fn, we get the correct result.

#![feature(no_core)]
#![no_core]

mod m1 {
    pub fn m2 (){}
}

{
  "crate_version": null,
  "external_crates": {},
  "format_version": 18,
  "includes_private": false,
  "index": {
    "0:0:1567": {
      "crate_id": 0,
      "id": "0:0:1567",
      "inner": {"is_crate": true, "is_stripped": false, "items": []},
      "kind": "module",
      "name": "bug"
    }
  },
  "root": "0:0:1567"
}

[aDotInTheVoid]

Caused by

rust/src/librustdoc/json/mod.rs

Lines 181 to 185 in eaadb89

	// Flatten items that recursively store other items. We include orphaned items from
	// stripped modules and etc that are otherwise reachable.
	if let ItemKind::StrippedItem(inner) = &*item.kind {
	inner.inner_items().for_each(|i| self.item(i.clone()).unwrap());
	}

which needs to be more conservitive