Skip to content

Type [x, x] is not assignable to type x[] & { length: 2; } #44508

Open
@strogonoff

Description

@strogonoff

Bug Report

This error is probably self-explanatory. Either this is supposed to work and it’s a bug, or I’m misunderstanding something in which case please feel free to close.

Type '(Record<string, any> | null)[] & { length: 2; }' is not assignable to type '[Record<string, any> | null, Record<string, any> | null]'.ts(2322)

Outer function is typed to return the latter. It calls an inner function, typed to return the former. One would assume this should work.

Possibly related: #44309

🔎 Search Terms

array literal length

🕗 Version & Regression Information

TypeScript 4.1.3

💻 Code

async function readObjectVersions
<L extends number, C extends string[] & { length: L }>
(objectPath: string, versions: C):
Promise<(Record<string, any> | null)[] & { length: L }> {
  return versions.map(version => ({ foo: 'bar' }));
}

const version1: string = 'x';
const version2: string = 'y';

async function _readObjectVersions(objectPath: string):
Promise<[ Record<string, any> | null, Record<string, any> | null ]> {
  return await readObjectVersions(objectPath, [version1, version2]);
}

_readObjectVersions('abc');

🙁 Actual behavior

The error as described above.

🙂 Expected behavior

No type error.

Metadata

Metadata

Assignees

No one assigned

    Labels

    In DiscussionNot yet reached consensusSuggestionAn idea for TypeScript

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions