unsized-vec

UnsizedVec<T> is like Vec<T>, but T can be ?Sized.

Features

• Similar API to Vec.
• Same time complexity as Vec for indexing, push, pop, insert, remove (more or less)
  • Exception: when T's alignment isn't fixed at compile-time, adding a new element to the Vec with a greater alignment than all elements currently present will take $\mathcal{O}(n)$ time, and will most likely reallocate.
• For T: Sized, only one heap allocation, approximately same memory layout as Vec.
• For unsized T, two heap allocations (one for the elements, one for the pointer metadata).
• #[no_std] (but requires alloc).
• Experimental, nightly-only.

Example

#![feature(unsized_fn_params)]
use core::fmt::Debug;
use unsized_vec::{*, emplace::box_new_with};

// `Box::new()` necessary only to coerce the values to trait objects.
let obj: Box<dyn Debug> = Box::new(1);
let obj_2: Box<dyn Debug> = Box::new((97_u128, "oh noes"));
let mut vec: UnsizedVec<dyn Debug> = unsized_vec![*obj, *obj_2];
for traitobj in &vec {
    dbg!(traitobj);
};

assert_eq!(vec.len(), 2);

let popped = box_new_with(|e| vec.pop_unwrap(e));
dbg!(&*popped);

assert_eq!(vec.len(), 1);