```swiftlet c1 = JSClosure { _ in .undefined }consume c1```did not release the `JSClosure` itself and it leaked the underlyingJavaScript closure too because `JSClosure` -> JS closure thunk ->Closure registry entry -> `JSClosure` reference cycle was not brokenwhen using FinalizationRegistry. (Without FR, it was broken by manual`release` call.)Note that weakening the reference does not violates the contract thatfunction reference should be unique because holding a weak reference doesdeinit but not deallocate the object, so ObjectIdentifier is not reuseduntil the weak reference in the registry is removed.

The test suite was not properly releasing the closures but they have notbeen revealed as a problem because those closures were leakedconservatively.

…tractThis additional information will help developers to find the root cause