type A {
  unrelated: String
  overlapping: Int
}

type B {
  overlapping: Int!
}

type C {
  overlapping: Int
}

union Union = A | B | C

type Query {
  root: Union
}

query {
  root {
    ... on A {
      unrelated
    }
  }
  root {
    ... on B {
      overlapping
    }
  }
  root {
    ... on C {
      overlapping
    }
  }
}