error[E0499]: cannot borrow `i` as mutable more than once at a time
  --> tests/compile/scope_mutable_aliasing.rs:12:51
   |
10 |     lua.scope(|scope| {
   |                ----- has type `&mlua::Scope<'_, '1>`
11 |         let _a = scope.create_userdata(MyUserData(&mut i)).unwrap();
   |                  -----------------------------------------
   |                  |                                |
   |                  |                                first mutable borrow occurs here
   |                  argument requires that `i` is borrowed for `'1`
12 |         let _b = scope.create_userdata(MyUserData(&mut i)).unwrap();
   |                                                   ^^^^^^ second mutable borrow occurs here
   |
note: requirement that the value outlives `'1` introduced here
  --> src/scope.rs
   |
   |         T: UserData + 'env,
   |                       ^^^^