using/await using rejects bound functions and proxied callables as dispose methods

Start by running the issue's reproduction under Node v24.18.0 and read the V8 / explicit resource management implementation involved in dispose-method lookup. Compare the callable checks for ordinary, bound, and proxied functions with the proposal's GetMethod behavior. Done means all four examples dispose successfully, with regression coverage for bound and proxied callables.

Version

v24.18.0

Platform

Microsoft Windows NT 10.0.26200.0 x64 (also reproduced on Linux x64 per downstream reports)

Subsystem

V8 / explicit resource management

What steps will reproduce the bug?

const fn = async function () { console.log('disposed'); };

// 1. bound function as async dispose method: throws
try {
  await using a = { [Symbol.asyncDispose]: fn.bind(null) };
} catch (e) { console.log('bound async:', e.message); }

// 2. bound function as sync dispose method: throws
try {
  using b = { [Symbol.dispose]: (function () {}).bind(null) };
} catch (e) { console.log('bound sync :', e.message); }

// 3. proxy-wrapped callable as dispose method: throws
try {
  await using c = { [Symbol.asyncDispose]: new Proxy(fn, {}) };
} catch (e) { console.log('proxied fn :', e.message); }

// 4. ordinary function: works
await using d = { [Symbol.asyncDispose]: fn };
console.log('plain fn accepted');

Output:

bound async: Symbol(Symbol.asyncDispose) is not a function
bound sync : Symbol(Symbol.dispose) is not a function
proxied fn : Symbol(Symbol.asyncDispose) is not a function
plain fn accepted
disposed

What is the expected behavior? Why is that the expected behavior?

All four cases should dispose. Per the Explicit Resource Management proposal, the dispose method is retrieved with GetMethod, which throws only when the value is neither undefined nor callable. Bound function exotic objects and proxies over callables are both callable (typeof reports "function" and they invoke fine), so rejecting them deviates from the spec. It looks like the implementation checks for a specific function instance type rather than IsCallable.

What do you see instead?

TypeError: Symbol(Symbol.asyncDispose) is not a function (respectively Symbol.dispose) at the using declaration site, for values that are callable.

Additional information

Found while debugging unjs/jiti#437: jiti's interopDefault proxy returns bound methods, so any default export with [Symbol.asyncDispose] fails under native await using while typeof mod[Symbol.asyncDispose] === 'function' reports a callable. Downstream is working around it by not binding symbol-keyed methods, but the engine behavior affects any code that binds or proxies dispose methods, which is common in DI containers and instrumentation wrappers.

If this is already tracked in the V8 tracker, a pointer would be appreciated and this can be closed as upstream.