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Home Page: http://npm.im/flown
License: MIT License
Type Helpers for Flow (static typechecker)
Home Page: http://npm.im/flown
License: MIT License
First of - thanks @lttb so much for this library! It's a huge help!
I'm running into the following issue best demonstrated by a small repro:
type GetUserInfoArgs = {| user_id: number |};
type GetUserInfo = (GetUserInfoArgs) => { first_name: string, last_name: string };
type DerivedArg = $ElementType<Arguments<GetUserInfo>, 0>; // should be equivalent to `GetUserInfoArgs`?
/**
* Using Arguments<GetUserInfo>:
* - `a` fails type checking as expected
* - `b` does not fail type checking :(
*/
const a: DerivedArg = { foo: 'bar' };
const b: {| ...DerivedArg |} = { foo: 'bar' };
/**
* Without using Arguments<GetUserInfo>:
* - `c` fails type checking as expected
* - `d` fails type checking as expected
*/
const c: GetUserInfoArgs = { foo: 'bar' };
const d: {| ...GetUserInfoArgs |} = { foo: 'bar' };
Perhaps I'm missing something, but I'd expect flow to complain about b
?
Thanks!
Hey, no issue, just wanted to let you know that this is really cool!! Thank you for sharing!
When a function that uses Reduce type is called more than one-time, flow error occurs:
type MergeAll<T> = Reduce<<X, V>(V) => X => { ...$Exact<X>, ...$Exact<V> }, {}, T>
declare function mergeAll<A>(A): MergeAll<A>
const x = mergeAll([{ a: 1 }, { b: 1 }, { c: 1 }, { a: 2 }])
const xx = mergeAll([{ a: 1 }, { b: 1 }, { c: 1 }, { a: 2 }])
// try to comment this line, the error disappears
;(x: { a: 2, b: 1, c: 1 }) // rightly
// or try to comment this line, the error disappears too
;(xx: { a: 2, b: 1, c: 1 }) // error?!
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