error[E0764]: mutable references are not allowed in the final value of constants
  --> $DIR/issue-17718-const-bad-values.rs:3:34
   |
LL | const C1: &'static mut [usize] = &mut [];
   |                                  ^^^^^^^

error[E0658]: referencing statics in constants is unstable
  --> $DIR/issue-17718-const-bad-values.rs:7:46
   |
LL | const C2: &'static mut usize = unsafe { &mut S };
   |                                              ^
   |
   = note: see issue #119618 <https://github.com/rust-lang/rust/issues/119618> for more information
   = help: add `#![feature(const_refs_to_static)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
   = help: to fix this, the value can be extracted to a `const` and then used.

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0658, E0764.
For more information about an error, try `rustc --explain E0658`.