[Dart 3.0] GetIt can't detect T type properly

[subzero911]

After the latest Flutter upgrade, registerSingleton inside of VoidCallback is not working anymore:

It worked before Dart 3.0. Now they probably have stricter type checking.
In runtime it crashes with the following error

The bug disappears when I explicitly indicate the type:

This bug appears in VoidCallback only, not in a plain code. It also can be fixed if I used:
() {} instead of () =>

The reason behind: a generic by default takes the root return type (void), and Dart tries to put void into T extends Object constraint, and this apparently causes this assert to be falsely posivite:

Any ideas on it?

[escamoteur]

@subzero911 your analysis seems correct, although I don't think that this can be fixed by GetIt. I always recommend passing the Generic type explicitly because then there is no room for doubt

@mraleph @munificent this comes sort of surprising, is that the intended consequence?

[subzero911]

First of all, it's strange that we can do call GetIt.instance(). Is it a callable class? I personally never did it. Do we actually need this assertion?

[escamoteur]

Actually the assertion isn't about calling it this way, but if people call GetIt.instance() accidentially you get this type of eception too.
And yes GetIt is a callable class from the beginning.
I most of the time to something like this in my setup file:

final di = GetIt.instance;
// and then use it like
di<Mytype>().myMethod();

[subzero911]

I always recommend passing the Generic type explicitly because then there is no room for doubt

But writing GetIt.I.registerSingleton<MyControllerWithVeryLongName>(MyControllerWithVeryLongName()) every time is not concise.

[escamoteur]

That is true, but you don't register that many types and in my case I often register an abstract interface class with a selected implementation then I have to provide the type anyway Am 29. Mai 2023, 11:21 +0200 schrieb Sergey Molchanovsky ***@***.***>:

…

> I always recommend passing the Generic type explicitly because then there is no room for doubt But writing GetIt.I.registerSingleton<MyControllerWithVeryLongName>(MyControllerWithVeryLongName()) every time is not concise. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you commented.Message ID: ***@***.***>

[munificent]

I'm not sure why this behavior is different in Dart 3.0. @stereotype441 or @eernst might know more.

[escamoteur]

@munificent unfortunately I never hot a reply from your colluges

[mraleph]

Just to save some time for Paul and Erik. Reduction is:

void foo(void Function() f) {
  f();
}

T bar<T extends Object>(T v) {
  print(T);
  return v;
}

void main() {
  foo(() => bar(''));
}

This will print Object rather than String.

[escamoteur]

@mraleph but why did that change with Dart 3.0 and was working before?