rust/tests/compile-fail/modifying_constants.rs

fn main() {
    let x = &1; // the `&1` is promoted to a constant, but it used to be that only the pointer is marked static, not the pointee
    let y = unsafe { &mut *(x as *const i32 as *mut i32) };
    *y = 42;  //~ ERROR constant evaluation error
    //~^ NOTE tried to modify constant memory
    assert_eq!(*x, 42);
}