Can't pick a property from an disjoint union

[danielo515]

I have a function with the following signature:

() =>
        | {|
            something: {
              isConnected: boolean,
            },
            isLoading: boolean
          |}
        | {|
            something: null,
            isLoading: boolean
          |}
    >

As you can see, it can return two possible objects, one with a something property which has content and that same objet with null in that property.
I want to use some utility types to pick the non null version of the something property. I tried the following:

type Something = $NonMaybeType<
  $PropertyType<
    $Call<
      () =>
        | {|
            something: {
              connectionError: string,
            },
            isLoading: boolean
          |}
        | {|
            something: null,
            isLoading: boolean
          |}
    >,
    "something"
  >
>

But when I pass any object type with the generated type I still get errors telling me that empty (the null version) is not compatible with object (the thing the function is expecting).

How can I pick the right property of the right side of the sum type?
It can be seen how flow picks the property from the first value of the enum because if I try to nest picks (or elementypes) it says that null does not have any property:

type BambooIntegration = $NonMaybeType<
  $ElementType<
  $ElementType<
    $Call<
      () =>
        | {|
            something: {
              isConnected: boolean,
            },
            isLoading: boolean
          |}
        | {|
            something: null,
            isLoading: boolean
          |}
    >,
    "something"
  >,{}>
>

// => 18:   >,{}>
        ^ Cannot instantiate `$ElementType` because null [1] does not have properties. [incompatible-use]
References:
13:             something: null,
                           ^ [1]

Expected behavior

I expect to get a sum type of the nested property or being able to choose which side of the sum type I want to pick

Actual behavior

It picks the first value (in this case null) from the sum type

• Link to Try-Flow or Github repo:
  https://flow.org/try/#0C4TwDgpgBAQghgWwEYHsUEkB2wIHMBOcwAliplALxQAkAcmQLJwhIQAq4EAPAFBQ0BRADYQEEbB0i9+1YaPHBJ3PvxoBhOEKHTV-ABQBKSgD4Vu-gB8oAbwtnzugM4oxwABbFMuAFw37D3WJHNTJMCABjHAATX1QUEThMABp-AIBfFIDzIIAZFDgozx8oOITMVN0LNIqoK1sapxcIdyLfTABXLUys1Vz8wq9YtDKG2urdY27+ACJnVw8vaZVJ6zTTUx5QSCgAMRR8BC4AajZfagAlCAKAeUwhEC5V40obNZeLq6jb+8eVKKI4L42N19sRcJ5NAARAFnS43O4PNiTHhrHhozacKBYABWEWiAAV8CgwI5jqcaHCvgjHmtnlR6vwAGb7BC+PYHLgfeE-JHPKwANxQxCiKSqPAA9OKoABVEhCYigKBbaDuIhK9r4TCOKCJKDEkhkTRQfmadoqlA6qCYMh6sAGzBGsgQDHbNgoeiYa520gOoQvLhIvTKoFGCjPOiMZisJQBjbKqAhbBErQQKLshCE4mkpHva5IbFMMBcHF41OZkmxpJQN0er32zQbcJkRzABNkYDJkRpln+8uOWGfb4PJ5Vk4D7nDt70taGEyvNHxvsvaz2ZkHNksrjwZBoLA4AhEH2mao8Jta1sADxeiY78S76a4faS27ie7whHtxkMp+brZAvhfXdsHfQ8bSoABWcCgA