[Peaker]

I was a bit surprised by the reverse:

  let x = 5
  let mut y = &x

If I understood correctly, x is immutable, but can still be mutated via (*y)?

[pcwalton]

No, that results in an error. Mutability doesn't inherit through references (`&`).

[coderjames]

[disclaimer: still learning Rust]

I believe it actually means that y can be made to reference something other than x.

  let x = 5
  let mut y = &x
  let i = 13
  y = &i

This is similar to C++'s const-pointers and pointers-to-consts, where either a pointer cannot be made to point at something different or the pointer cannot be used to change what it points at.

[FreeFull]

That actually lets you change what y points at, but you can't mutate x through y. If you want to mutate x, you need something like

    let y = &mut x;

which will result in an error due to x not being mutable.