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lib.es2022: hasOwn appears to be defined on Object prototype rather than on constructor #48206
Description
Activity
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
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.
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
hasOwnas 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'.
No, you're totally right, this is just the lib being wrong. Misread what you were getting at.
No problem! I should've provided the more specific error case up front.
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.
I'll put up a PR. Thanks for the report 👍
Reacted by Derrick Liu- added a commit that references this issue
on Mar 10, 2022 - added a commit that references this issue
on Mar 10, 2022 - added a commit that references this issue
on Mar 11, 2022 Do you know if or when this might land in a patch version?
We'll be doing a patch release in the next week or two (just waiting to see if other patchworthy things appear first)
Reacted by Rendall- locked as resolved and limited conversation to collaborators
on Oct 22, 2025
Bug Report
🔎 Search Terms
hasOwn, Object.hasOwn, es2022, prototype, lib.es2022.object.d.ts
🕗 Version & Regression Information
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 (e80a0ca) running TypeScript 4.6.2.
💻 Code
🙁 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
hasOwnas a boolean property.🙂 Expected behavior
hasOwnshould be a method of theObjectconstructor (Object.hasOwn), not the prototype (foo.hasOwn).