lib.es2022: hasOwn appears to be defined on Object prototype rather than on constructor

[lediur]

Bug Report

🔎 Search Terms

hasOwn, Object.hasOwn, es2022, prototype, lib.es2022.object.d.ts

🕗 Version & Regression Information

• This changed between versions 4.2.4 and 4.6.2

Appears to be introduced by #46291

⏯ Playground Link

Doesn't appear to reproduce on Playground or Bug Workbench, reproduces in VS Code 1.66.0-insider (e80a0ca648fe9bef07070e4f7fb04e67f2243252) running TypeScript 4.6.2.

💻 Code

interface SomeComponentProps {
  requiredProp: boolean
  hasOwn?: boolean;
}

const SomeComponent: React.FC<SomeComponentProps> = () => {}

return <SomeComponent requiredProp />

🙁 Actual behavior

I ran into this issue because I was trying to upgrade the project from 4.3.5 to 4.6.2. The project has some object types with hasOwn as a boolean property.

// TS2322: Type '{ requiredProp: boolean }' is not assignable to type 'SomeComponentProps'.
  Types of property 'hasOwn' are incompatible.
    Type '(o: object, v: PropertyKey) => boolean' is not assignable to type 'boolean'.

🙂 Expected behavior

hasOwn should be a method of the Object constructor (Object.hasOwn), not the prototype (foo.hasOwn).

[RyanCavanaugh]

This is an intended UX trade-off in JS files. Since often you'll have untyped variables, we show method help based on name-matching; this way if you're looking for help for a common method name, it shows up even without matching type information.

For more precise behavior, you can turn on checkJs.

See also #33565

[lediur]

Thanks for the reply! I'm seeing this in a TypeScript file in a TypeScript React project when trying to upgrade from 4.3.5 to 4.6.2. Does the same behavior apply?

Let me get a more specific example of the issue I'm running into, one sec.

[lediur]

I ran into this issue because I was trying to upgrade the project from 4.3.5 to 4.6.2. The project has some object types with hasOwn as a boolean property.

e.g.

interface SomeComponentProps {
  requiredProp: boolean
  hasOwn?: boolean;
}

Using those types started failing to typecheck after the upgrade since TypeScript. For example:

const SomeComponent: React.FC<SomeComponentProps> = () => {}

return <SomeComponent requiredProp />
// TS2322: Type '{ requiredProp: boolean }' is not assignable to type 'SomeComponentProps'.
  Types of property 'hasOwn' are incompatible.
    Type '(o: object, v: PropertyKey) => boolean' is not assignable to type 'boolean'.

[RyanCavanaugh]

No, you're totally right, this is just the lib being wrong. Misread what you were getting at.

[lediur]

No problem! I should've provided the more specific error case up front.

[lediur]

I'm happy to make a PR with test cases for the fix, though it might take me a bit longer since I haven't contributed to TypeScript before. If you'd like to fix this internally that's fine by me.

[RyanCavanaugh]

I'll put up a PR. Thanks for the report 👍

[lediur]

Do you know if or when this might land in a patch version?

[RyanCavanaugh]

We'll be doing a patch release in the next week or two (just waiting to see if other patchworthy things appear first)