Thanks!

Let's follow this, as another commit in the same PR, accompany this, squashed into the same commit, with bumping the minimum Flutter version in pubspec.yaml. As is, this change fixes things when you have a new Flutter version, but breaks them if you have an older Flutter version:

$ tools/check 
Running analyze...
Resolving dependencies... 
Note: intl is pinned to version 0.18.1 by flutter_localizations from the flutter SDK.
See https://dart.dev/go/sdk-version-pinning for details.


Because zulip depends on flutter_localizations from sdk which depends on intl
  0.18.1, intl 0.18.1 is required.
So, because zulip depends on intl ^0.19.0, version solving failed.


You can try the following suggestion to make the pubspec resolve:
* Consider downgrading your constraint on intl: flutter pub add intl:^0.18.1
Running test...
Resolving dependencies... 
Note: intl is pinned to version 0.18.1 by flutter_localizations from the flutter SDK.
See https://dart.dev/go/sdk-version-pinning for details.


Because zulip depends on flutter_localizations from sdk which depends on intl
  0.18.1, intl 0.18.1 is required.
So, because zulip depends on intl ^0.19.0, version solving failed.


You can try the following suggestion to make the pubspec resolve:
* Consider downgrading your constraint on intl: flutter pub add intl:^0.18.1
Running build_runner...
Running drift...
Running icons...

FAILED: analyze test

To rerun the suites that failed, run:
  $ tools/check analyze test

Fundamentally the root issue here is #15 — we should at some point get around to pinning the Flutter version, and then this sort of thing would just be another version constraint we update at the same time as updating that pin. But pending that, when we make a change that causes things to stop working on an older Flutter version, we should reflect that in the Flutter version constraint we do express.

In particular I think it'd be good to maintain an invariant that if you take the Flutter version lower bound in the pubspec, and you do interpret it as a pin of an exact version, then things work. (Hence squashing this change with the Flutter version bump.) That way there's always a straightforward, unambiguous way to get a working setup — and what's missing (for #15) is just the automation to update to that exact version.

(I also just filed #575 for the issue this fixes; so please add a "fixes" line for that in the commit message.)

Thanks for the review! Revision pushed, and did a quick manual smoke test on my iPhone. I saw in particular that the send button on the compose box looks right.

Thanks for taking care of this!

The changes all LGTM. I'd like the commit message to foreground the Flutter version bump more; I'll revise that and merge.