rustc::hir::HirVec

type HirVec<T> = P<[T]>;

Unstable (rustc_private)

HIR doesn't commit to a concrete storage type and have its own alias for a vector. It can be Vec, P<[T]> or potentially Box<[T]>, or some other container with similar behavior. Unlike AST, HIR is mostly a static structure, so we can use an owned slice instead of Vec to avoid keeping extra capacity.