So the answer is yesn’t? Like, the logic for checking whether a `#[repr(transparent)]` ADT will reveal the layout of your type to the type checker with no regards for visibility but an end user in another crate will at least get a lint.

Here is the compiler’s logic for checking whether a transparent structure has a legal layout.

github.com/rust-lang/ru...

It seems to have the notion of an unsuited type, which is a non-local ADT with private fields or a `non_exhaustive` attribute, and will lint if you use it as a ZST.

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