PlainObject not working with Interfaces

[Kagu-chan]

The Type PlainObject, which is used as type constrain for functions like merge does not accept interfaces.

type R = Record<PropertyKey, unknown>; // same as PlainObject, but its not exported. So lets rebuild it here
type Foo = {
  a: number;
  b: number;
};
interface Boo {
  a: number;
  b: number;
}

function f<x extends R>(x: x): void {
  /* NOP */
}

f<Foo>({ a: 1, b: 1 }); // This is OK
f<Boo>({ a: 1, b: 1 }); // This fails and requires a symbol and a string key

/*
Type 'Boo' does not satisfy the constraint 'R'.
  Index signature for type 'string' is missing in type 'Boo'.ts(2344)
*/

TS Playground: https://www.typescriptlang.org/play?ts=4.8.4#code/C4TwDgpgBASlC8sIGMD2AnAJgHgArtUnVAGkIQAaKAVwDsBrW1Ad1oD4BuKAem6gGcAhgFtog-lFwAbQQEtaAeQBGAKxTAqS6sCizgEpjogAPMBmARMAOigBlVFCkR9UdBC2ypmXToAWENwBYAChQSCgAMVQHRABvEKgoQQAuKFpqYSUAjgSoJVT0zOyQgF8c4PkLdAAzQWRoACFoqHjgxJS0jKz0csT8zqKe0pCQ6rpkYFlUWihq7GMoEwtaTAkYNgAKY1TjAEpUgDdUWW9WxO4AKigAOQVcKAvuYeDR7CjUTdik1IBGTV+oCVdlxeFAACq+WQSKFQBQkV5ND4bL4dP55AFAkF8CEw2qeCSCFauCAAR2osjcBIEIEyqCkSSJggEwHQ8gA5lB6OQgA

[kemaric]

I can take a look into this.

[Maggi64]

🤔 I've tried a few things but haven't found a good solution. If anyone has a good solution, please let me know.

[Maggi64]

Making use of Record<PropertyKey, any> fixes it. And will be released shortly (bc9aeec). The tradeoff is that now other objects like Date, RegEx also can be passed into the function. I think this is better then dealing with TS when using interfaces.