idx() callbacks may only access properties on the callback parameter!

[xareelee]

I've reported this issue on flowtype: facebook/flow#4729

I also create an issue here.

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The following code raises a flowtype error when using idx with immutable.js:

// `state` is obtained from redux store
// `state.user` is an immutable object; you need to use `getIn()` to access properties
const token = idx(state, _ => _.user.getIn(['userInfo', 'token']));

The flowtype shows the error:

 81:   const countryCode = idx(state, _ => _.country.getIn(['selectCountry', 'countryCode']));
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ function call. idx() callbacks may only access properties on the callback parameter!

I need to change code to this to suppress flowtype warnings:

const tokenS = idx(state, _ => _.user.getIn);
const token = (tokenS) ? tokenS(['userInfo', 'token']) : undefined;

It makes no sense to write such code.

[yungsters]

Call expressions are no longer supported from within idx. Obsoleted by v2.0.0.