error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:19:9
   |
LL |         (*(a as *const _ as *mut String)).push_str(" world");
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[deny(cast_ref_to_mut)]` on by default

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:21:9
   |
LL |         *(a as *const _ as *mut _) = String::from("Replaced");
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:23:9
   |
LL |         *(a as *const _ as *mut String) += " world";
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:25:25
   |
LL |         let _num = &mut *(num as *const i32 as *mut i32);
   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:27:25
   |
LL |         let _num = &mut *(num as *const i32).cast_mut();
   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:29:20
   |
LL |         let _num = *{ num as *const i32 }.cast_mut();
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:31:9
   |
LL |         *std::ptr::from_ref(num).cast_mut() += 1;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:33:9
   |
LL |         *std::ptr::from_ref({ num }).cast_mut() += 1;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:35:9
   |
LL |         *{ std::ptr::from_ref(num) }.cast_mut() += 1;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/cast_ref_to_mut.rs:37:9
   |
LL |         *(std::ptr::from_ref({ num }) as *mut i32) += 1;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 10 previous errors