Add test for needless_pass_by_ref_mut to ensure that the lint is no…

…t emitted if variable is used in an unsafe block or function

tests/ui/needless_pass_by_ref_mut.rs

@@ -1,4 +1,9 @@
-#![allow(clippy::if_same_then_else, clippy::no_effect, clippy::redundant_closure_call)]
+#![allow(
+    clippy::if_same_then_else,
+    clippy::no_effect,
+    clippy::redundant_closure_call,
+    clippy::mut_from_ref
+)]
 #![warn(clippy::needless_pass_by_ref_mut)]
 #![feature(lint_reasons)]
 //@no-rustfix
@@ -270,6 +275,18 @@ pub async fn closure4(n: &mut usize) {
     })();
 }
 
+struct Data<T: ?Sized> {
+    value: T,
+}
+// Unsafe functions should not warn.
+unsafe fn get_mut_unchecked<T>(ptr: &NonNull<Data<T>>) -> &mut T {
+    &mut (*ptr.as_ptr()).value
+}
+// Unsafe blocks should not warn.
+fn get_mut_unchecked2<T>(ptr: &NonNull<Data<T>>) -> &mut T {
+    unsafe { &mut (*ptr.as_ptr()).value }
+}
+
 fn main() {
     let mut u = 0;
     let mut v = vec![0];