Extending Array in @typedef don't work as expected

[NemoStein]

Bug Report

In a js file (checkJs: true) with JSDoc, extending the Array<T> type doesn't allow to add properties to the extended type.
Considering this:

/**
 * @template T
 * @typedef {Array<T>} ArrayExtA
 * @property {T} prop
 */

// No error here, but should, since `string[]` don't have property `prop`
/** @type {ArrayExtA<string>} */
const extA = ['']

// Error: Property 'prop' does not exist on type 'ArrayExtA<string>'.
console.log(extA.prop)

Typescript understood that ArrayExtA<string> is an extension of Array<string>, allowing [''] to be assigned to the typed const extA, but failed to add the prop property.

Using a Intersection Type works, though

/**
 * @template T
 * @typedef Trait
 * @property {T} prop
 */

/**
 * @template T
 * @typedef {Array<T> & Trait<T>} ArrayExtB
 */

// Error: Type 'string[]' is not assignable to type 'ArrayExtB<string>'.
/** @type {ArrayExtB<string>} */
const extB = ['']

// No error here, as expected
console.log(extB.prop)

Failing to assign [''] to the typed const extB is expected, since string[] lacks the prop property of ArrayExtB

🔎 Search Terms

jsdoc, typedef, extend, array

🕗 Version & Regression Information

4.2.0-dev.20210207

🙁 Actual behavior

@typedef {A} B fails to add properties to type B if type A is Array

🙂 Expected behavior

Expected type B to be a type A with additional properties

[sandersn]

This is a special case of #42877.

@NemoStein I am curious what tool you use that understands this syntax, because I found little usage in the example code bases we use. Can you comment with that information on #42877?