error[E0384]: cannot assign twice to immutable variable `x`
  --> $DIR/mut-pattern-internal-mutability.rs:5:5
   |
LL |     let &mut x = foo;
   |              - first assignment to `x`
LL |     x += 1;
   |     ^^^^^^ cannot assign twice to immutable variable
   |
help: consider making this binding mutable
   |
LL |     let &mut mut x = foo;
   |              ~~~~~
help: to modify the original value, take a borrow instead
   |
LL |     let &mut ref mut x = foo;
   |              ~~~~~~~~~

error[E0506]: cannot assign to `*foo` because it is borrowed
  --> $DIR/mut-pattern-internal-mutability.rs:13:5
   |
LL |     let &mut ref x = foo;
   |              ----- `*foo` is borrowed here
LL |     *foo += 1;
   |     ^^^^^^^^^ `*foo` is assigned to here but it was already borrowed
LL |     drop(x);
   |          - borrow later used here

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0384, E0506.
For more information about an error, try `rustc --explain E0384`.