Shouldn't this show some unchecked cast warning?

Unchecked cast warnings are for generic casts (where it won't go wrong when casting but when accessing the type) (Badly worded but something like that)

Why do you think it should be an unchecked cast? B is a subtype of A so

a

could be a

B

and this check will be carried out at runtime

I mean a warning showing that this cast can have a

ClassCastException

because its not checked that

a

is B type, it can be A or C also

Every cast can have a ClassCastException If the compiler could guarantee the type then it wouldn't need the cast. So a cast is in theory always "dangerous"

Well you can check it before, like if(a is B){ a.sayHi()} right?

I don't know if there is an inspection you can activate in Intellij warning you about unsafe casts

Maybe its a rule in some linters I know in Java there's SonarLint that'll give you a warning when casting (without checking)

@carlos cdmp If you check it before then the compiler smartcasts and you don't need it either.

Yes, because when you cast to a generic type parameter, the code has to "assume" that the object is an instance of that type, because the type has been erased.