Implement `From<&[T; N]>` and `From<&mut [T; N]>` for `Vec<T>` where `T: Clone`?

[EFanZh]

Currently we have impl From<&[T]> for Vec<T> where T: Clone and impl From<&mut [T]> for Vec<T> where T: Clone, should From<&[T; N]> and From<&mut [T; N]> also be implemented for Vec<T> where T: Clone?

[vincenzopalazzo]

@rustbot claim

[vincenzopalazzo]

Can you help me with runnable code to understand why the From<&mut [T; N]> [for Vec<T> where T: Clone will be useful and what can be a use case for it?

@rustbot label +T-libs-api

[vincenzopalazzo]

Ah ok, maybe I understand what do you mean, currently we can do

use std::vec::Vec;

#[derive(Clone, Copy, Debug)]
struct Type;

fn main() {
    let mut array = [Type{}];
    let mut vect = vec![];
    vect.extend_from_slice(&array);
    println!("{:?}", vect);  
}

And your proposal is to support

use std::vec::Vec;

#[derive(Clone, Copy, Debug)]
struct Type;

fn main() {
    let mut array = [Type{}];
    let mut vect = Vec::from(&array);
    println!("{:?}", vect);
    
}

[EFanZh]

@vincenzopalazzo I don’t have a use case for From<&mut [T; N]>, adding it is just for matching existing From<&mut [T]>. But for From<&[T; N]>, I want to be able to write:

fn foo(value: Option<&[String; 2]>) -> Option<Vec<String>> {
    value.map(Vec::from)
}

instead of

fn foo(value: Option<&[String; 2]>) -> Option<Vec<String>> {
    value.map(<[_; 2]>::as_slice).map(Vec::from)
}