False negative typecheck error after using Omit with union type.

[Akiyamka]

Bug Report

Omitting one property from union type broke typecheck of other properties in union.
Typescript completely loose property if it abset at least in one of types from union after Omit helper,
Object literal may only specify known properties, and 'property_that_actually_exist' does not exist in type 'Omit<AnyLayer, "id">'

🔎 Search Terms

omit breaks union

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about

⏯ Playground Link

Playground link with relevant code

💻 Code

interface FillLayer {
    id: string;
    type: 'fill';
    property_that_actually_exist?: string;
}

export interface CustomLayerInterface {
    id: string;
    type: 'custom';
}

export type AnyLayer =
    | FillLayer
    | CustomLayerInterface;


/* Test case with omit */
const layerStyles = Array<Omit<AnyLayer, 'id'>>();
layerStyles.push({
    type: 'fill',
    property_that_actually_exist: 'source',
})

/* Test case without omit */
const layerStyles2 = Array<AnyLayer>();
layerStyles2.push({
    id: 'foo',
    type: 'fill',
    property_that_actually_exist: 'source',
})

🙁 Actual behavior

false negative typecheck error after using Omit with union type.

🙂 Expected behavior

Omit not broke union typecheck

[Akiyamka]

For those who encounter the same problem, a temporary solution looks like this:

export type FixedOmit<T, U> = T extends any ? Pick<T, Exclude<keyof T, U>> : never

Playground link

[RyanCavanaugh]

Omit isn't distributive and the odds we can change it to be distributive seem pretty low. See #53169

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.