extension_type_representation_type_bottom

The representation type can't be a bottom type.

The analyzer produces this diagnostic when the representation type of an extension type is the bottom type Never. The type Never can't be the representation type of an extension type because there are no values that can be extended.

The following code produces this diagnostic because the representation type of the extension type E is Never:

extension type E(Never n) {}

Replace the extension type with a different type:

extension type E(String s) {}