> Unlike nearly every language I’ve ever used, Rust actually encourages variable shadowing. Haskell does it too, for the same reason/purpose / with the same effect.
Swift does, but typically for Optional promotion. You see stuff like `guard let delegate = delegate else { return }` inside functions all the time, shadowing a property with a local & promoting the type from Optional to T. It's not the same as the Rust example because you're shadowing an ivar to a local, but since `self.` is implicit you're still shadowing.
I actually really try to avoid this pattern. For one it pollutes the function scope with a shadowed binding and it's pretty unnecessary boilerplate. Most always you can map across the optional and use the unwrapped version as the block scoped argument identifier, e.g. `$0`. When you can't or you want to handle both cases, I find a simple `if let delegate = delegate {} else {}` is more explicit and scopes the binding to the block instead of polluting the current scope. I'm not saying `guard` is bad, I use it all the time when there are good names to bind things to, but I dislike how much it proliferates and how often it doesn't actually provide value and just lets the program silently fail instead of loudly fail which half the time is worse than a nullpointerexception anyway...