We have three, in fact, which disallow various kinds of shadowing. For example, some people like `let x = <expr containing x>` shadows but not `let x = <totally

We have three, in fact, which disallow various kinds of shadowing. For example, some people like `let x = <expr containing x>` shadows but not `let x = <totally unrelated>`. But everyone has wildly different style choices here so we leave all three off by default and you can turn them on if you want. I have yet to see a bug in Rust code caused by shadowing, though.