The documentation for destructors actually does contain the answer to their motivating example [0]. It's difficult to read, but it's there, and it thoroughly ex

The documentation for destructors actually does contain the answer to their motivating example [0]. It's difficult to read, but it's there, and it thoroughly explains what's happening here. Local variable bindings have the scope of the block they're in. Other expressions have a temporary scope. The _ wildcard pattern is documented [1], and is explicitly not an identifier pattern. The documentation specifically says that it does not copy, move, or borrow values. Therefore, expressions on the right hand side of a let that uses _ as the pattern do not bind to a value and therefore use a temporary scope. Yes, the language here is difficult to understand, but that's true of specifications as well. Just like with these docs, you'll have to refer to multiple sections of the spec in order to piece together the expected behavior. There may be other reasons for a spec (it puts different implementations on equal footing instead of having one official reference implementation), but in this case if the reference is hard to follow I don't see any reason to believe a spec would be better. [0] https://doc.rust-lang.org/reference/destructors.html#temporary-scopes https://doc.rust-lang.org/reference/destructors.html#tempora... [1] https://doc.rust-lang.org/reference/patterns.html#wildcard-pattern https://doc.rust-lang.org/reference/patterns.html#wildcard-p...