Provide spec for multiple platform-specific non-actuals with identical DRIs

[owengray-google]

An example of this is KAnnotatedElement, which has definitions in JVM and native but not common, with the same DRI/fully-qualified-name.

In this case, it seems very reasonable to have a unified page, but what if these two members had meaningfully different definitions, e.g. Field.jvm.kt: interface Field : PSIElement and Field.native.kt: class Field : GrassyTerrain or something.
(Or just a significant difference in supertypes like UASTElement and SomeNativeSyntaxTreeElement that lead to completely disjoint API surfaces.)

What I would propose is banning this at a compiler level and e.g. making @Suppress("NO_ACTUAL_FOR_EXPECT") expect interface KAnnotatedElement, or diverging the names by platform.

[owengray-google]

It's possible case may be a blocker for fully supporting android and JVM as different things, because it's very possible to have an android app import both?

[owengray-google]

We've just run into someone doing this in androidx, but not because they wanted--because of https://youtrack.jetbrains.com/issue/KT-69741.

They want to define an expect class in commonMain, and then in another intermediate sourceSet jvmCommon add an inner expect class to it, which syntax doesn't seem to exist for, so they defined unconnected versions in each leaf sourceSet instead.
I think the simplest syntax here would be an extension class, in which you define a class Foo.Bar as an inner class of Foo, without being inside the definition of Foo?