StreamSignal.dispose() (and FutureSignal) throws SignalsWriteAfterDisposeError

[mernen]

Test:

var signal = streamSignal(() => Stream.value(1));
signal.dispose();

This happens because dispose() calls reset(), which in turn calls AsyncSignal.reset(), which then calls set value, which notices the signal has already been disposed.

The simplest fix is to move super.dispose() to be the last operation in dispose(), since conceptually deinitialization should be done in reverse order of initialization. But I'm a bit worried the library is doing too much during disposal. For example, the last step of reset() is to set _initialized to true, which doesn't make sense in a disposed object.

[rodydavis]

There was some recent changes to autoDisposing and need to update the async signal implementation to reflect the correct order.

That error was a new addition. Will update and add some tests.

On the old version of stream/future signal it was using dispose as a reset to default but not destroying it. Now signals that call dispose should not be written to after.

Thanks for capturing this!