microsoft / microsoft/TypeScript

TypeScript incorrectly says return is not assignable to an intersection containing all the required props

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Bug Domain: Intersection
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Description

Bug Report

🔎 Search Terms

& generic intersection omit spread

🕗 Version & Regression Information
  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about generics
⏯ Playground Link

Playground link with relevant code

💻 Code
export interface BaseProps {
  id?: string;
  name: string;
}

export type PropsWithId<P extends BaseProps> = Omit<
  P,
  'id'
> & { id: string };

export default function usePropsWithId<P extends BaseProps>(
  props: P
): PropsWithId<P> {
  const { id: idProp, name, ...other } = props;
  const id = idProp ?? `${name}-id`;

  return { id, name, ...other };
}
🙁 Actual behavior

The return line gets this TypeScript error:

Type '{ id: string; name: string; } & Omit<P, "id" | "name">' is not assignable to type 'PropsWithId<P>'.
  Type '{ id: string; name: string; } & Omit<P, "id" | "name">' is not assignable to type 'Omit<P, "id">'.

This doesn't make sense since PropsWithId<P> is Omit<P, 'id'> & { id: string };

🙂 Expected behavior

This should work without a TypeScript error.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked TypeScript Playground and the generic intersection example in the issue, then trace how the checker evaluates the returned object against PropsWithId

. The issue names no repository files or tests; done means the sample compiles without the reported assignability error while preserving the expected PropsWithId

type.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
45/100

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