Simple and efficient Vec<[T; N]> into Vec<T> implementation

try_from_vec_array.rs

#![allow(incomplete_features)]
#![feature(const_generics)]

#[derive(Debug)]
pub enum TryFromVecArrayError {
    OverflowedLen,
    OverflowedCap,
}

pub trait TryFromVecArray<T, const N: usize> {
    type Error;
    type Into;
    fn try_from_vec_array(v: Vec<[T; N]>) -> Result<Self::Into, Self::Error>;
}

impl<T, const N: usize> TryFromVecArray<T, N> for Vec<T> {
    type Error = TryFromVecArrayError;
    type Into = Self;
    fn try_from_vec_array(v: Vec<[T; N]>) -> Result<Self::Into, Self::Error> {
        let mut v = std::mem::ManuallyDrop::new(v);
    
        let p = v.as_mut_ptr() as *mut T;
        let len = v.len().checked_mul(N).ok_or(TryFromVecArrayError::OverflowedLen)?;
        let cap = v.capacity().checked_mul(N).ok_or(TryFromVecArrayError::OverflowedCap)?;
    
        unsafe {
            Ok(Vec::from_raw_parts(p, len, cap))
        }
    }
}