.omit does not work with unions

[mrazauskas]

Playground link.

Take a look at the following example. Omit works as expected, but .omit fails:

import {expectTypeOf} from 'expect-type'

type Loading = {
  state: "loading";
};
type Failed = {
  state: "failed";
  code: number;
};

expectTypeOf<Omit<Loading | Failed, 'code'>>().toEqualTypeOf<{state: 'loading' | 'failed'}>()

expectTypeOf<Loading | Failed>().omit<'code'>().toEqualTypeOf<{state: 'loading' | 'failed'}>()
                                   // ^^^^^^ Type '"code"' does not satisfy the constraint '"state"'.

[mmkal]

@mrazauskas thanks for reporting. Note that Omit<...> doesn't seem to have any extends constraints at all (e.g. Omit<{a: 1}, 'b'> is allowed), so this will take away type hinting at which keys could/should be omitted. But I agree it's better to match Omit.

Would you be interested in submitting a pull request?

[mrazauskas]

@aryaemami59 Perhaps you would be interested to take a second look at the implementation?

[aryaemami59]

@mrazauskas

@aryaemami59 Perhaps you would be interested to take a second look at the implementation?

Yes absolutely, I will take a look!