JSDOC generics bug for callbacks when args are present

[simonyarde]

🔎 Search Terms

"Generics", "JSDOC", "Callback"

🕗 Version & Regression Information

TS 5.7.3
v5.8.0-dev.20250131

⏯ Playground Link

https://www.typescriptlang.org/play/?filetype=js#code/PQKgUGBSDKAiDyBhABAcwKYDt0CcCWAxgM7IBGArqsgGYD2OyBAhgDYulMEDWJA7gBZZkTHKhIj0yAA450RLABcIASUzIFgmrTa1eeTFXQAPJgFspLdABpkAAwAm6avvQAKAJS3kRfrXIt7ZFkFchw1WwA1RAAeaAA+WxsKBWQBIRFUMFtmNg5uL34mcVESPBT7WjlkTFoU2SJtADdJW2gvJkxA4NDMEkiYjoBPBIA6CBBgCFBwZBBkAAEFdHMWJiXkaDBZhakRM2QAb1cMgAYALkPkWlJ5HGacC4BReGQAX3dkAF44jdfGVnYnC4yC2c3muxw+wO8CkCjwtF6fwA2rRYfDegBdEHbebdMIkA5RWJxV6gyagUELBSDKSSA7IYmuaiYC7HUTnS7XW73J7wADcbw+3w2NlRcIRRAA-BcYeLekKfkT4m8yWBqORMAQ5chHM5sK4coDuKK0RKPgctsgrQQJSl6ZgzJI-p8rqbeshJZLDqSrdbbVcbrh7l9quheMhnh5LX7eikiAo1pIXYa8lxXPSuUHcILo0F0CEwqHw1FXPHE+4wKSwNNKYtlhZExtVQRVkQSFFDrnplSaXToH8Jrmy0suyAZr6cRCof3vAn1rnZpMJzbYzhyFr6KW5+hzQvfRo8EQRsOk7PE7nSVXu4te7rDvbHdLZ-gDG8-rL0SRB2AW0USM9vSmYBkAAQVEOwUyBLw9A0YQSmQABaZAYAQFAKjkTAAHI6jkJpJGgMZgGAlCkGXf1GgARguIkhjiatgIAFWgCdfRXeNkEo6iYlIWhtHQDo6LYlJKJDXUXFcNlUBOBV1DXaxLgdUx0AuTDdSYfwFEwnN6NA8DsgBVNoLKXxyBSDISCQki0MqEh6jwjZCOIuBSNY8iACYuOiHi+IEnSmJYmN2MaDzkCJbzLF8oSOLc0SnHEjwvh+BQ5JsB8lJUtSNK094wCAA

💻 Code

In the following example, define() should return VC<S>, but when arg callback has args it does not resolve S and returns VC<any>.

/**
 * @template S
 * @param {(arg0: { observer: EO }) => S} callback 
 * @param {Options} [options] 
 * @returns {VC<S>}
 */
/*
 * @type { <S>(fn: (arg0: { observer: EO; }) => S, options?: Options) => VC<S> }
 */
function define(callback, options) {
    const { name } = options ?? {}
    const observer = new EO()
    const state = callback({ observer })
    return new VC(state)
}

/**
 * @template S
 */
class VC {
    /** @type {S} */
    state
    /**
     * @param {S} state 
     */
    constructor(state) {
        this.state = state
    }
}

/** @typedef {{ name?: string }} Options */

class EO {}

// Arg `callback` with args - JSDOC doesn't resolve S.
// JSDOC    const v1: VC<any>
// TS       const v1: VC<boolean>
const v1 = define((arg0) => true, { name: 'default' })

// Arg `callback` without args - JSDOC does resolve S.
// JSDOC    const v2: VC<boolean>
// TS       const v2: VC<boolean>
const v2 = define(() => true, { name: 'default' })

🙁 Actual behavior

JSDOC doesn't resolve S

🙂 Expected behavior

JSDOC should resolve S in the same way as TS.

Additional information about the issue

No response

[Andarist]

When you report an issue like this it's always good to provide the equivalent TS code so the maintainers can quickly verify the report. I've already done that for this short example, so here it is: TS playground

[simonyarde]

Thanks @Andarist