Fix ICE test

Author: oli-obk

tests/crashes/122548.rs renamed to tests/ui/statics/mutable_memory_validation.rs

@@ -1,4 +1,4 @@
-//@ known-bug: #122548
+//issue: rust-lang/rust#122548
 #![feature(const_mut_refs)]
 #![feature(const_refs_to_static)]
 
@@ -8,9 +8,8 @@ struct Meh {
     x: &'static UnsafeCell<i32>,
 }
 
-const MUH: Meh = Meh {
-    x: &mut *(&READONLY as *const _ as *mut _),
-};
+const MUH: Meh = Meh { x: unsafe { &mut *(&READONLY as *const _ as *mut _) } };
+//~^ ERROR: it is undefined behavior to use this value
 
 static READONLY: i32 = 0;
 

tests/ui/statics/mutable_memory_validation.stderr

@@ -0,0 +1,14 @@
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_memory_validation.rs:11:1
+   |
+LL | const MUH: Meh = Meh { x: unsafe { &mut *(&READONLY as *const _ as *mut _) } };
+   | ^^^^^^^^^^^^^^ constructing invalid value at .x.<deref>: encountered `UnsafeCell` in read-only memory
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾ALLOC0<imm>╼                         │ ╾──────╼
+           }
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.