Exact no longer works with recursive types + unions

[abrenneke]

Code that worked in v4.21.0 no longer compiles in v4.22.0 after the change to Exact. Simplified code below:

import { Exact } from 'type-fest';

export type A = { a: Expected; }
export type B = { b: string }
export type Expected = A | B;

const _errors: Exact<Expected, Expected> = {} as Expected;

Playground Link

We believe that the change which caused IsEqual to not be first here causes the type to be distributed early, and the IsEqual check suddenly fails because it distributes to Exact<A, Expected> | Exact<B, Expected> which doesn't make any sense.

isEqual used to be first, which is why this worked previously, so I think moving it first again could fix this issue.

cc @zorji

Upvote & Fund

• We're using Polar.sh so you can upvote and help fund this issue.
• The funding will be given to active contributors.
• Thank you in advance for helping prioritize & fund our backlog.