Unused variable with flow type inside destructured parameters

[arthurflachs]

Related to #184 : when declaring the type of destuctured parameters, babel-eslint reports a no-unused-var error :

function DestructuringWithFlowType({x}: MyType): boolean {
  return !!x;
}

Defining the type in a destructuring assignment seems to work fine :

const x = { a: { b: true } };
const { a }: MyType = x;

[arthurflachs]

This seems to prevent the babel lint task from passing, for instance there.

[hzoo]

This is the same as #236 I think so closing as a dupe - Thanks!

[hzoo]

Also should be fixed by #246