warning: taking a mutable reference to a `const` item
  --> $DIR/E0017.rs:5:30
   |
LL | const CR: &'static mut i32 = &mut C;
   |                              ^^^^^^
   |
   = note: `#[warn(const_item_mutation)]` on by default
   = note: each usage of a `const` item creates a new temporary
   = note: the mutable reference will refer to this temporary, not the original `const` item
note: `const` item defined here
  --> $DIR/E0017.rs:2:1
   |
LL | const C: i32 = 2;
   | ^^^^^^^^^^^^^^^^^

error[E0764]: mutable references are not allowed in constants
  --> $DIR/E0017.rs:5:30
   |
LL | const CR: &'static mut i32 = &mut C;
   |                              ^^^^^^ `&mut` is only allowed in `const fn`

error[E0019]: static contains unimplemented expression type
  --> $DIR/E0017.rs:7:39
   |
LL | static STATIC_REF: &'static mut i32 = &mut X;
   |                                       ^^^^^^
   |
   = help: add `#![feature(const_mut_refs)]` to the crate attributes to enable

error[E0764]: mutable references are not allowed in statics
  --> $DIR/E0017.rs:7:39
   |
LL | static STATIC_REF: &'static mut i32 = &mut X;
   |                                       ^^^^^^ `&mut` is only allowed in `const fn`

error[E0596]: cannot borrow immutable static item `X` as mutable
  --> $DIR/E0017.rs:7:39
   |
LL | static STATIC_REF: &'static mut i32 = &mut X;
   |                                       ^^^^^^ cannot borrow as mutable

warning: taking a mutable reference to a `const` item
  --> $DIR/E0017.rs:10:38
   |
LL | static CONST_REF: &'static mut i32 = &mut C;
   |                                      ^^^^^^
   |
   = note: each usage of a `const` item creates a new temporary
   = note: the mutable reference will refer to this temporary, not the original `const` item
note: `const` item defined here
  --> $DIR/E0017.rs:2:1
   |
LL | const C: i32 = 2;
   | ^^^^^^^^^^^^^^^^^

error[E0764]: mutable references are not allowed in statics
  --> $DIR/E0017.rs:10:38
   |
LL | static CONST_REF: &'static mut i32 = &mut C;
   |                                      ^^^^^^ `&mut` is only allowed in `const fn`

error[E0764]: mutable references are not allowed in statics
  --> $DIR/E0017.rs:12:52
   |
LL | static STATIC_MUT_REF: &'static mut i32 = unsafe { &mut M };
   |                                                    ^^^^^^ `&mut` is only allowed in `const fn`

error: aborting due to 6 previous errors; 2 warnings emitted

Some errors have detailed explanations: E0019, E0596, E0764.
For more information about an error, try `rustc --explain E0019`.