JSDOC generics bug for callbacks when args are present

🔎 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

Beginne mit dem verlinkten TypeScript Playground-Repro und vergleiche die inferierten Typen von v1 und v2 mit den erwarteten TypeScript-Ergebnissen. Verfolge anschließend den Inferenzpfad für generische JSDoc-Callbacks im Compiler und füge einen Regressionstest hinzu, der zeigt, dass v1 als VC inferiert wird, wenn der Callback ein Argument hat.