tuple destruction to initialized variables

[ghost]

(I hope I am in the right repo and this isn't a duplicate or a dump question :)

Currently (using rust 1.34.1) destructing a tuple is only possible to newly created variables.

let mut foo = 0;
let mut bar = 1;

(foo, bar) = (2,3);

This code fails with following error.

 |
 | (foo, bar) = (2,3);
 | ^^^^^^^^^^^^^^^^^^ left-hand of expression not valid

---

But this is valid.

let mut foo = 0;
let mut bar = 1;

let test = (2,3);

foo = test.0;
bar = test.1;

I think it would be intuitive to destruct into already known variables rather than having to create a new one.

[varkor]

This is rust-lang/rfcs#372.