`SmallVec` allocates a contiguous array in the struct holding the vector itself (so it can be located on the stack), then if the capacity is insufficent, fallba

`SmallVec` allocates a contiguous array in the struct holding the vector itself (so it can be located on the stack), then if the capacity is insufficent, fallbacks to a heap-allocated `Vec` equivalent. The `Vec` struct contains the capacity and used length integers, as well as a pointer to the heap-allocated storage.