Shouldn’t this be allowed since we are implementing

FooWrapper

(which is allowed) and

FooWrapper

already extends

Foo

?

sealed interface Foo

interface FooWrapper: Foo {
    val wrappedFoo: Foo
}

// other module

class FooWrapperImpl(
    override val wrappedFoo: Foo,
): FooWrapper, Foo by wrappedFoo // Inheritance of sealed classes or interfaces from different module is prohibited

You can mark

FooWrapper

as sealed, and neither would be allowed. But as it stands, FooWrapper is not sealed.

I think the way I see it is that the

Foo by wrappedFoo

is just there as a convenience to implement part of the

FooWrapper

interface. It’s not changing what

FooWrapperImpl

does or does not implement.

Seems reasonable to be allowed, please file an issue.