Type is not cast

[AlexanderFarkas]

Same without <dynamic,dynamic>

But in that case it starts working

• Dart SDK version: 2.17.6 (stable)
• Mac OS arm64

[lrhn]

You're not showing us the original declaration of origin.
If the third example allows promotion to work, most likely the origin variable is a local variable declared as something like Provider<T, dynamic>, some type where FactoryProvider<T, dynamic> is a subtype, but FactoryProvider<dynamic, dynamic> (or the equivalent FactoryProvider) is not, because the dynamic type argument is not a subtype of T.

Dart promotion requires the new type to be a subtype of the current type, otherwise it wouldn't be promotion.

Now, it would be nice if we could infer type arguments for is FactoryProvider which allows promotion, but we currently don't.

[AlexanderFarkas]

Great explanation. Thanks