`__typename` in `fragment`

[swalker2m]

A co-worker uses a tool (SGQLC) to generate queries. It seems to like inserting __typename wherever it can. One such place is in fragments. Unfortunately this may (?) not be working with Grackle. For example this query is fine:

query {
  human(id: 1002) {
    friends {
      __typename
      ...CharacterFields
    }  
  }
}
fragment CharacterFields on Character {
  id
}

but this similar query fails with No field '__typename' for type Character:

query {
  human(id: 1002) {
    friends {
      ...CharacterFields
    }  
  }
}
fragment CharacterFields on Character {
  __typename
  id
}

[swalker2m]

This inline fragment with __typename also works:

query {
  human(id: 1002) {
    friends {
      ... on Character {
        __typename
        id
      }
    }  
  }
}