Problematic let_and_return (false positive?)

[llogiq]

From carboxyl:

                        let ret = strong.read().unwrap().call();
                        ret

However, when I change to strong.read().unwrap().call(), I get

src/signal.rs:412:25: 412:31 error: `strong` does not live long enough
src/signal.rs:412                         strong.read().unwrap().call()
                                          ^~~~~~
src/signal.rs:410:29: 413:22 note: reference must be valid for the destruction scope surrounding block at 410:28...
src/signal.rs:410                     move || {
src/signal.rs:411                         let strong = sig.upgrade().unwrap();
src/signal.rs:412                         strong.read().unwrap().call()
src/signal.rs:413                     }
src/signal.rs:411:61: 413:22 note: ...but borrowed value is only valid for the block suffix following statement 0 at 411:60
src/signal.rs:411                         let strong = sig.upgrade().unwrap();
src/signal.rs:412                         strong.read().unwrap().call()
src/signal.rs:413                     }

At the very least, the docs should reflect this possible problem. I note that this is within a move || { .. } closure. Perhaps this has something to do with the error.

[oli-obk]

This is a rust-issue: rust-lang/rust#31439

[llogiq]

We should still document this as a possible problem as long as the issue persists.