IntrospectionResultData: fix broken typing

[avindra]

The types:

Original : what is currently on master
Fixed: proposal in this PR

---

data represents a schema that will break due to invalid typing of possibleTypes.

data2 will generate an error.

---

TL;DR;, I am trying to consume a GraphQL endpoint that is returning [] in possibleTypes, which apollo-client is refusing to accept.

 type Fixed = {
  __schema: {
    types: [{
      kind: string,
      name: string,
      possibleTypes: {
        name: string,
      }[],
    }],
  },
};

type Original = {
  __schema: {
    types: [{
      kind: string,
      name: string,
      possibleTypes: [{
        name: string,
      }],
    }],
  },
};

const data: Fixed = {
    __schema: {
        types: [
            {
                kind: 'someKind',
                name: 'someName',
                possibleTypes: []
            }
        ]
    }
};

const data2: Original = data; 

[apollo-cla]

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[stubailo]

Whoa. In TypeScript [X] and X[] are actually different?

[avindra]

@stubailo yes. You can verify this by pasting the code above in http://www.typescriptlang.org/play

[stubailo]

Wow, I did not know that. Mind adding a changelog entry for this?

[avindra]

@stubailo Updated PR

[stubailo]

Thanks a lot!