mergeAll does not accept arrays anymore about types HOT 2 CLOSED

Hi there thanks for the issue. I found out what was going on here. For types-ramda we updated to the latest ts-toolkit as that was needed to fix some existing types. The way the mergeAll was previously types used type functions from ts-toolkit that no longer exists. So we had to re-type them.

The current type is this:

export function mergeAll<O extends object, Os extends readonly object[]>(list: [O, ...Os]): _.O.Assign<O, Os>;

_.O.Assign is defined here and as the name suggests, a type for Object.assign, which is exactly what mergeAll is under the hood

Our tests included the following

const foo = { foo: 'foo' };
const bar = { bar: 'bar' };
const foo2 = { foo: 2 };

expectType<{ foo: string; }>(mergeAll([foo]));
expectType<{ foo: string; bar: string; }>(mergeAll([foo, bar]));
expectType<{ foo: number; }>(mergeAll([foo, foo2]));

Those tests, as it turns out, only account for passing in array literals of either the same or different types. It turns out, that when you pass in an Array<any> or any[], the typings break down. It breaks down specifically because when you have Array<any> or any[], [O, ...Os] cannot be inferred in the same way when passing an array literal or tuple, Giving you the Source provides no match for required element at position 0 in target. error

Fortunately, this is an easy fix. Since when you mergeAll an Array<T> you simple get back T. Which means the solution is just to add this overload

export function mergeAll<T>(list: readonly T[]): T;

MR here: #23
I'll try to get this merged and released today for you

from types.

Thank you for the swift fix an in depth explanation 💥

from types.