`VersatileBuffer<A>` (tantivy-common) keeps an allocation and lends it
as an empty `Vec<T>`, for any `T` with the size and alignment of `A`.
The allocation goes back to the buffer when the guard is dropped,
including on panic. If the guard is leaked, the buffer starts again
from an empty `Vec`.
This makes it possible to reuse a buffer of values borrowing data with
a short lifetime, without self-referential structs.
The jitexpr predicate uses it for its argument slots. It replaces the
`ClearOnDrop` guard, which transmuted a `Vec<VariableValue<'static>>`
to a shorter lifetime.
Co-authored-by: Paul Masurel <paul.masurel@datadoghq.com>
Paul MasurelandPaul Masurel
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