[tialaramex]

There is no such restriction, it's just much less common to want that.

  let x: u32 = 5;
  let x: u32 = 10; // You can write this, but why?
  let x: u32 = 20; // I really feel like you should re-consider

If you end up shadowing this way in a long function it more likely means the function got too long. On the other hand, I certainly have had cause to shadow variables in inner scopes e.g.

  let x = some_complicate_stuff();
  for dx in [-1, 0, 1] {
    let x = x + dx;
    // Do stuff with x very naturally here, rather than keep saying "x + dx" everywhere
  }
  // But outside the loop x is just x, it's not x + dx