src/test/ui/consts/miri_unleashed/mutable_references.rs

   1 // compile-flags: -Zunleash-the-miri-inside-of-you
   2 #![feature(const_mut_refs)]
   3 #![allow(const_err)]
   4
   5 use std::cell::UnsafeCell;
   6
   7 // a test demonstrating what things we could allow with a smarter const qualification
   8
   9 // this is fine because is not possible to mutate through an immutable reference.
  10 static FOO: &&mut u32 = &&mut 42;
  11
  12 // this is fine because accessing an immutable static `BAR` is equivalent to accessing `*&BAR`
  13 // which puts the mutable reference behind an immutable one.
  14 static BAR: &mut () = &mut ();
  15
  16 struct Foo<T>(T);
  17
  18 // this is fine for the same reason as `BAR`.
  19 static BOO: &mut Foo<()> = &mut Foo(());
  20
  21 struct Meh {
  22     x: &'static UnsafeCell<i32>,
  23 }
  24
  25 unsafe impl Sync for Meh {}
  26
  27 static MEH: Meh = Meh {
  28     x: &UnsafeCell::new(42),
  29     //~^ WARN: skipping const checks
  30 };
  31
  32 // this is fine for the same reason as `BAR`.
  33 static OH_YES: &mut i32 = &mut 42;
  34
  35 fn main() {
  36     unsafe {
  37         *MEH.x.get() = 99;
  38     }
  39     *OH_YES = 99; //~ ERROR cannot assign to `*OH_YES`, as `OH_YES` is an immutable static item
  40 }