warning[E0502]: cannot borrow `*x.1` as immutable because it is also borrowed as mutable
  --> $DIR/feature-gate-nll.rs:14:13
   |
LL |     let m = &mut x;
   |             ------ mutable borrow occurs here
LL |     let p = &*x.1;
   |             ^^^^^ immutable borrow occurs here
...
LL |     m;
   |     - mutable borrow later used here
   |
   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future

error: compilation successful
  --> $DIR/feature-gate-nll.rs:10:1
   |
LL | / fn main() {
LL | |     let mut x = (33, &0);
LL | |
LL | |     let m = &mut x;
...  |
LL | |     m;
LL | | }
   | |_^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0502`.