Analyzer erroneously rejects use of nullable extension type representation variable via type parameter

[stereotype441]

The analyzer rejects the following code, but the CFE accepts it:

extension type E(int? value) {}

test<T extends E>(T t) => t.value; // ERROR

The analyzer's error message is: The property 'value' can't be unconditionally accessed because the receiver can be 'null'. It's true that the receiver (t) can be null (because the extension type's representation type is nullable), but that's not a problem; it's still safe to access the property value.

[stereotype441]

I'm going to work on this.