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 ( reports 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.