Clarify `invalid_reference_casting` lint around interior mutable types

1 files changed, 8 insertions, 0 deletions

diff --git a/tests/ui/lint/reference_casting.rs b/tests/ui/lint/reference_casting.rs
index fba8789e999..25e0c75f70d 100644
--- a/tests/ui/lint/reference_casting.rs
+++ b/tests/ui/lint/reference_casting.rs
@@ -64,6 +64,10 @@ unsafe fn ref_to_mut() {
     let _num = &mut *num;
     //~^ ERROR casting `&T` to `&mut T` is undefined behavior
 
+    let cell = &std::cell::UnsafeCell::new(0);
+    let _num = &mut *(cell as *const _ as *mut i32);
+    //~^ ERROR casting `&T` to `&mut T` is undefined behavior
+
     unsafe fn generic_ref_cast_mut<T>(this: &T) -> &mut T {
         &mut *((this as *const _) as *mut _)
         //~^ ERROR casting `&T` to `&mut T` is undefined behavior
@@ -106,6 +110,8 @@ unsafe fn assign_to_ref() {
         std::mem::transmute::<*const i32, *mut i32>(num),
         -1i32,
     );
+    *((&std::cell::UnsafeCell::new(0)) as *const _ as *mut i32) = 5;
+    //~^ ERROR assigning to `&T` is undefined behavior
 
     let value = num as *const i32 as *mut i32;
     *value = 1;
@@ -148,6 +154,8 @@ unsafe fn no_warn() {
     *RAW_PTR = 42; // RAW_PTR is defined outside the function body,
                    // make sure we don't ICE on it when trying to
                    // determine if we should lint on it or not.
+    let cell = &std::cell::UnsafeCell::new(0);
+    let _num = &mut *(cell.get() as *mut i32);
 
     fn safe_as_mut<T>(x: &std::cell::UnsafeCell<T>) -> &mut T {
         unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }