type A {
  unrelated: String
  overlapping: Int
}
type B {
  overlapping: Int!
}
type C {
  overlapping: Int
}
union Union = A | B | C
type Query {
  root: Union
}

# There is a conflicting type due to `B.overlapping` and `C.overlapping` both being selected
# to `root.overlapping`, but neither overlap with the initial selection set for `root`.

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