poor performance on lodash flow check

I found that #1696 (better handling null/undefined) introduced bad performance to flow checking

tested with flow version 0.63, 0.64 tested script

// @flow

import _ from 'lodash';

_.map([], () => 0);

comparison	file	time spent
before	before pr #1696	~2 seconds
after	current master	~45 seconds

Could we do anything to improve this?

[Zmetser]

Removing all the individual module declarations (introduced here) solved this for me. @maxmalov

[Zmetser]

@maxmalov You’re right, I’m sorry. You just added the fp exports and I removed all.

Still, removing all the individual exports speeds up flow. Here’s a test repo where flow only reads the lodash libdef and does nothing else when you run yarn flow and there’s almost a minute difference. https://github.com/Zmetser/lodash_flow_test