map.setIfUndefined doesn't consider inheritance in parameters

[byrond]

Describe the bug
When we attempt to call map.setIfUndefined(A, 'key', () => new B) where class B extends the class used in Map A, we get the following:

Argument of type 'Map<string, A>' is not assignable to parameter of type 'Map<string, B>'.
  Type 'A' is missing the following properties from type 'B': ... ts(2345)

This seems to be related to its definition:

 * @function
 * @template V,K
 * @template {Map<K,V>} MAP
 * @param {MAP} map
 * @param {K} key
 * @param {function():V} createT
 * @return {V}

We have worked around the issue by copying the logic inline instead of using map.setifUndefined, but it would be great to be able to use it with inherited classes.

To Reproduce
Steps to reproduce the behavior:

Use the following JS, and attempt to generate types with tsc:

import * as map from 'lib0/map'

class A {
  constructor() {
    this.property1 = 1
  }
}

class B extends A {
  constructor() {
    super()
    this.property2 = 2
  }
}

/**
 * @type {Map<string, A>}
 */
const set = new Map()

const item = map.setIfUndefined(set, 'key', () => new B)

Expected behavior
We can call map.setIfUndefined(A, 'key', () => new B) where class B extends the class used in Map A, and the function adds a new instance of B to the map without errors.

Screenshots
If applicable, add screenshots to help explain your problem. Tip: you can drag-drop images into this textarea.

Environment Information

• Node 18.18.2

Additional context
Add any other context about the problem here.

[Kevin Jahns]

Makes sense. I fixed it.