main()1 fn main() { 2 let mut value = 3; 3 let _borrow = &mut value; 4 let _sum = value + 1; //~ ERROR E0503 5 _borrow.use_mut(); 6 } 7 use_mut(&mut self)8 trait Fake { fn use_mut(&mut self) { } fn use_ref(&self) { } } 9 impl<T> Fake for T { } 10