Incorrect parse of subscripts

SourceKitten seems to have problems with this kind of Swift:

extension Test {
    /// This comment is for subscript()
    subscript(bounds: Range<Int>) -> String  {
        return "dummy 1"
    }
}

extension Test {
    /// This comment is for whatever()
    func whatever() -> String {
        return "dummy 2"
    }
}

When that's run using sourcekitten doc --single-file test.swift it generates the following output:

{
  "\/Users\/twostraws\/Desktop\/Issue\/test.swift" : {
    "key.diagnostic_stage" : "source.diagnostic.stage.swift.parse",
    "key.length" : 261,
    "key.offset" : 0,
    "key.substructure" : [
      {
        "key.bodylength" : 119,
        "key.bodyoffset" : 16,
        "key.kind" : "source.lang.swift.decl.extension",
        "key.length" : 136,
        "key.name" : "Test",
        "key.namelength" : 4,
        "key.nameoffset" : 10,
        "key.offset" : 0,
        "key.substructure" : [

        ]
      },
      {
        "key.bodylength" : 103,
        "key.bodyoffset" : 154,
        "key.doc.comment" : "This comment is for subscript()",
        "key.kind" : "source.lang.swift.decl.extension",
        "key.length" : 120,
        "key.name" : "Test",
        "key.namelength" : 4,
        "key.nameoffset" : 148,
        "key.offset" : 138,
        "key.substructure" : [
          {
            "key.accessibility" : "source.lang.swift.accessibility.internal",
            "key.bodylength" : 30,
            "key.bodyoffset" : 225,
            "key.doc.comment" : "This comment is for whatever()",
            "key.kind" : "source.lang.swift.decl.function.method.instance",
            "key.length" : 58,
            "key.name" : "whatever()",
            "key.namelength" : 10,
            "key.nameoffset" : 203,
            "key.offset" : 198
          }
        ]
      }
    ]
  }
}

So, an empty extension, followed by an extension commented using the comment from my subscript, which in turn contains the whatever() method. I would expect the This comment is for subscript() comment to appear in the first extension, along with subscript().

Start by reproducing the report with the Swift sample in test.swift using sourcekitten doc --single-file test.swift, then inspect the generated key.substructure output. The issue is done when the subscript and its comment appear in the correct extension and the unrelated whatever() method remains correctly represented.