/// still be live when `T` gets dropped. The exact details of this analysis are not yet

/// stably guaranteed and **subject to change**. Currently, the analysis works as follows:

/// - If `T` has no drop glue, then trivially nothing is required to be live. This is the case if

/// neither `T` nor any of its (recursive) fields have a destructor (`impl Drop`). [`PhantomData`]

/// and [`ManuallyDrop`] are considered to never have a destructor, no matter their field type.

/// neither `T` nor any of its (recursive) fields have a destructor (`impl Drop`). [`PhantomData`],

/// arrays of length 0 and [`ManuallyDrop`] are considered to never have a destructor, no matter

/// their field type.

/// - If `T` has drop glue, then, for all types `U` that are *owned* by any field of `T`,

/// recursively add the types and lifetimes that need to be live when `U` gets dropped. The set of

/// owned types is determined by recursively traversing `T`:

/// - Recursively descend through `PhantomData`, `Box`, tuples, and arrays (including arrays of

/// - Recursively descend through `PhantomData`, `Box`, tuples, and arrays (excluding arrays of

/// length 0).

/// - Stop at reference and raw pointer types as well as function pointers and function items;

/// they do not own anything.