keyof an interface that extends an anyObject

[dolphinlin]

TypeScript Version: 3.7.2

Search Terms:

Code

// A *self-contained* demonstration of the problem follows...
// Test this by running `tsc` on the command-line, rather than through another build tool such as Gulp, Webpack, etc.
type AnyObject = {
  [key: string]: any;
};

interface Test extends AnyObject {
  name: string;
  age: number;
  handsome: boolean;
}

type TestKey = keyof Test;

const testObject: Test = {
  name: 'Dolphin',
  age: 999,
  handsome: true,
};

Expected behavior:

type TestKey = 'name' | 'age' | 'handsome';

Actual behavior:

type TestKey = string | number;

Playground Link:
https://www.typescriptlang.org/play/index.html#code/C4TwDgpgBAggdiA8gIwFYQMbCgXigbwCgooBtAawhAC4oBnYAJwEs4BzAXVoEMEBuQgF8BhVsAiMAZtwzQAKhAZQIAD3FwAJnVgIU6LAWJQ43ALYRaDFuwElubC8YCup5BIGDChUJCgKGANJUuFCUIAD2kn6KwCIY4XBK4gx6mMC0-th4RCQm5rQA5AAi4QA2YAAWrAUANEb2jgCczUJ8QA

Related Issues:

[dolphinlin]

if Test ain't extends AnyObject, TestKey will be correct.

[jcalz]

This is working as intended. testObject.blarf = 1; is acceptable because Test has an index signature because Test extends AnyObject. so keyof Test is going to reflect that index signature type which absorbs all string literals.

[dolphinlin]

This is working as intended. testObject.blarf = 1; is acceptable because Test has an index signature because Test extends AnyObject. so keyof Test is going to reflect that index signature type which absorbs all string literals.

Yes, agree ur opinion, but that maybe shouldn’t lost the keys of Test type ('name' | 'age' | 'handsome').

[jcalz]

So is this a duplicate of #33471 then?

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.