Now that I think about names, I understand why you...

# decompose

[s3rius]

Now that I think about names, I understand why you called it Overlay in the first place!
I think Slot is good. I was also thinking Container or Holder, but both terms sound like they would apply to ChildStack as well.

[Arkadii Ivanov]

Yeah, the rationale was that Child Overlay will be mostly used for dialogs, popups, modal sheets, etc. But now there are other use cases as well.

"Container" sounds ambiguous indeed, it's not clear whether it's just one child component, or a set of components. It's also pretty long name.

"Holder" for some reason sounds like something immutable for me, like a wrapper class holding some references.

"Slot" looks concise, and expresses the "one or none" semantics. The more I think about this name, the more I like it. 😀

[Evegenii Khokhlov]

+, I love “Slot” too