PhantomData confusing documentation

[dimbleby]

Location

https://doc.rust-lang.org/std/marker/struct.PhantomData.html#ownership-and-the-drop-check, via

rust/library/core/src/marker.rs

Line 728 in 21e6de7

/// `T` in very rare circumstances. This in turn has effects on the Rust compiler's [drop check]

Summary

#103413 updated the documentation for PhantomData to say

Currently, adding a field of type PhantomData<T> indicates that your type owns data of type T in very rare circumstances.

I don't understand. How rare must these circumstances be for me to use PhantomData? What should I do if my type always owns data of type T?

I guess this is not what was meant, but I am finding it hard to figure out what the intention was and propose an improvement.

Possibly just remove the phrase "in very rare circumstances"?

[dimbleby]

@wuwbobo2021 this issue covers the specific line of documentation that it describes in the summary, please don't try to use it as a catch-all for PhantomData questions