Struct BitSetPayload 

#[repr(C)]
pub struct BitSetPayload {
    pub words: ReprCVec<u64>,
}

The BitSet payload: a growable vector of 64-bit words. Bit i is in word i / 64 at position i % 64. The field is Drop.

Fields

words: ReprCVec<u64>

The words. Trailing zero words may be present; equality/hash trim them.

A ReprCVec rather than a std::Vec for ADR-118’s reason: generated code reads the words pointer and the word count inline for bs.contains(x), and std::Vec is #[repr(Rust)] — its three words live inside a private RawVec in no guaranteed order. The container gives those three words a fixed layout; Vec still does every allocation.