Moved value with drop gets borrowed on reassignment

[laurmaedje]

In the following example, Dropper contains a mutable reference and a destructor that uses that reference. The compiler thinks that Dropper's drop code runs when reassigning to the variable v. But since here the value is already moved and v is basically just an empty slot, that shouldn't haben and as such I would expect that I can reuse the variable.

It works if I create a new let binding, but in my actual use case that doesn't work because I want to reassign in a loop.

fn main() {
    let mut s = "hi".to_string();

    let mut v = Dropper(&mut s);
    drop(v);

    // error: first borrow might be used here, when `v` is dropped
    //        second mutable borrow occurs here
    v = Dropper(&mut s);
}

struct Dropper<'a>(&'a mut String);

impl Drop for Dropper<'_> {
    fn drop(&mut self) {
        self.0.push_str("dropped!");
    }
}

Meta

rustc --version --verbose:

rustc 1.50.0 (cb75ad5db 2021-02-10)
binary: rustc
commit-hash: cb75ad5db02783e8b0222fee363c5f63f7e2cf5b
commit-date: 2021-02-10
host: x86_64-pc-windows-msvc
release: 1.50.0

[shepmaster]

Duplicate of #70919?

[WaffleLapkin]

This indeed looks like a dupe of #70919, which itself was fixed by #107844 (cc @zeegomo, can you double check this is correct?), closing as such.