error[E0499]: cannot borrow `forward_a` as mutable more than once at a time
--> $DIR/locking_from_same_forward_twice.rs:15:13
|
13 | let _b = forward_a.lock_m1();
| --------- first mutable borrow occurs here
14 | // Invalid
15 | let _ = forward_a.lock_m1();
| ^^^^^^^^^ second mutable borrow occurs here
16 | }
| - first borrow might be used here, when `_b` is dropped and runs the destructor for type `(std::sync::MutexGuard<'_, ()>, MainLockTreeM1<'_>)`