Flutter intl version conflict - flutter

Question

I get this error:
Because my_rents depends on flutter_localizations any from sdk which
depends on intl 0.17.0-nullsafety.2, intl 0.17.0-nullsafety.2 is
required. So, because my_rents depends on intl ^0.16.0, version
solving failed. pub get failed (1; So, because my_rents depends on
intl ^0.16.0, version solving failed.)
my_rents is the name of my app, it's not an specific package
If instead of
intl: ^0.16.1
I have
intl: 0.17.0-nullsafety.2
The error I get is
Because firebase_auth >=0.18.0+1 <0.18.1 depends on firebase_auth_web
^0.3.0+1 and firebase_auth >=0.18.1 <=0.18.1+1 depends on
firebase_auth_web ^0.3.1, firebase_auth >=0.18.0+1 <=0.18.1+1 requires
firebase_auth_web ^0.3.0+1. And because firebase_auth >=0.18.1+2
<0.18.2 depends on firebase_auth_web ^0.3.1+1, firebase_auth
=0.18.0+1 <0.18.2 requires firebase_auth_web ^0.3.0+1. And because firebase_auth >=0.18.2 <0.18.3 depends on firebase_auth_web ^0.3.1+2
and firebase_auth >=0.18.3+1 <0.18.4 depends on firebase_auth_web
^0.3.2+1, firebase_auth >=0.18.0+1 <0.18.3-∞ or >=0.18.3+1 <0.18.4-∞
requires firebase_auth_web ^0.3.0+1. And because firebase_auth
=0.18.3 <=0.18.3 depends on firebase_auth_web ^0.3.2 and firebase_auth >=0.18.4 <=0.18.4 depends on firebase_auth_web ^0.3.2+2,
firebase_auth >=0.18.0+1 <=0.18.4 requires firebase_auth_web ^0.3.0+1.
And because firebase_auth ^0.18.4+1 depends on firebase_auth_web
^0.3.2+3 which depends on intl ^0.16.1, firebase_auth ^0.18.0+1
requires intl ^0.16.1. So, because my_rents depends on both
firebase_auth ^0.18.0+1 and intl 0.17.0-nullsafety.2, version solving
failed. pub get failed (1; So, because my_rents depends on both
firebase_auth ^0.18.0+1 and intl 0.17.0-nullsafety.2, version solving
failed.)

Answer 1

The dart and flutter teams are transitioning to null-safety feature. It is still in beta (that is why you get this error just with the beta channel). Not every package are already upgraded to null-sefety. You can fix this issue either by:
asking the developer of the package to upgrade to null safety
use a version of flutter which has not null-safety enabled
use a beta version of the package with null-sefty enabled
Check also this issue
Original answer: Pubspec.yaml resolving version failed in master channel but works in stable channel in Flutter
For now easiest solution is:
flutter channel stable
flutter upgrade

Answer 2

You can resolve the issue by settings the 'any' to resolve issue
https://stackoverflow.com/a/65971167/14950155
Intl: any