emit needless_return on return stmts using borrow

[dswij]

Fix #8978

This check is added on #5903 to fix #5858. Though, the test added here compiles as of today, so this can be removed. (playground)

changelog: [needless_return] now emits on on return stmts using borrow

[rust-highfive]

r? @giraffate

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[Alexendoo]

I think that's due to rust-lang/rust#93965

use std::cell::RefCell;

fn foo(x: RefCell<String>) -> String {
    let y = x;
    return y.borrow().clone();
}

wouldn't compile if the return were removed (from https://github.com/rust-lang/rust/blob/9a74608543d499bcc7dd505e195e8bfab9447315/src/test/ui/span/issue-23338-locals-die-before-temps-of-body.rs)

[dswij]

Oh wait, you're right. 😅
Closing this one