Is this normal behavior or am I missing something?

[Andrew Mezoni]

The code compiles and runs fine, but throws an exception. 

Is that how it should be?

void main() {

  final c = LC<String>('foo');

  // CP want c<List<int>?, T> but c is C<List<int>, T>

  final cp = CP<List<int>?, String>(c);

  cp.p(null);

}

abstract class C<I, O> {

  O c(I v);

}

class CP<I, T> {

  final C<I, T> c;

  CP(this.c);

  T p(I v) => c.c(v);

}

class LC<T> implements C<List<int>, T> {

  final T v;

  LC(this.v);

  @override

  // Unhandled exception:

  // type 'Null' is not a subtype of type 'List<int>' of 'v'

  T c(List<int> v) => this.v;

}

[Lasse R.H. Nielsen]

Yes, that's expected behavior (if I read the example correctly).

Dart's covariant generics are unsound, which is why methods parameters typed with the type arguments get run-time checks added.

It's the same issue as:

  List<int?> list = <int>[];

  list.add(null); // run-time error.

/L

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Lasse R.H. Nielsen - l...@google.com  

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[Andrew Mezoni]

Yeah...
Thank you.

среда, 26 мая 2021 г. в 00:05:34 UTC+5, Lasse Reichstein Holst Nielsen:

[Andrew Mezoni]

You have to add rule to the linter for such cases.

For Lists.

 List<int?> list = <int>[]; // <= Some warning about possible unpredictable behavior at runtime.

среда, 26 мая 2021 г. в 00:11:08 UTC+5, Andrew Mezoni: