[NNBD] Conflicting generic type in Navigator's push methods

[sma]

In class Navigator, there is Future<T> push<T>(Route<T> route) and static Future<T> push<T extends Object>(BuildContext context, Route<T> route). The latter restricts T to a subclass of Object which means that a Route<void> doesn't work here. I think, it should be possible to use such a route with both variants. The same if true for other variants of push or replace.

If there is a reason for not allowing Route<void> this should be documented, I think. Currently the documentation stats:

/// The type argument `T` is the route's return type, as used by
/// [currentResult], [popped], and [didPop]. The type `void` may be used if the
/// route does not return a value.

[ndawod]

This is a recent change (horrible decision, btw) in Fluter -- it was possible to use void just yesterday.

The same can be said about many of the changes from today's upgrade. Apps are breaking because of the nullability changes.

[sma]

Some time ago I ported a 7000 LOC app to NNBD and now I regularly check the progress and this was the first problem so far. Therefore, I can't deny or confirm other breakage :) I was able to work around this problem by using Navigator.of(context).push() and my app still runs. BTW, I don't think this is a documentation bug but a a typing error.

[goderbauer]

/cc @a14n @chunhtai

I agree that Route<void> still needs to be allowed.

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.