Macro __impl_altvec_logical_dataptr 

#[doc(hidden)]
macro_rules! __impl_altvec_logical_dataptr {
    ($ty:ty) => { ... };
}

Internal macro: impl AltVec with materializing dataptr for logical ALTREP.

Thin wrapper: provides a trivial AltrepDataptr (no direct pointer) and delegates to __impl_altvec_dataptr which materializes via RNativeType::elt. R logicals are stored as i32 but accessed through RLogical for type safety.