Computed object properties in Flow

flow-computed.js

/*
https://flow.org/try/#0FAFwngDgpgBA8jAvDA3jA2gcgIaYLoBcMAziAE4CWAdgOYwC+MAZKhpgEb5FUCuAtuyhkGMAPSiYAewDWMABQADLADpVXGKuUKYFYjGxUdVACZQAHkICUwYKYDGAG2xlYAN2dSicANw3vcyWVsbn5BMksxCSEySWE5c2g7EChja39A4JJyahoI8SlpPwDldhCBK0iC4HSSolJKWjyoshi4hKgklMsgA
*/

type O = { ['a']: string } & { ['b']: number } // ok (`['...']: ...` is an indexer)

declare var o: O;

;(o.a: number) // error (expected)
;(o.a: string) // ok

;(o.b: number) // ok
;(o.b: string) // error (expected)