adding test for mutable_adt_argument_transmute lint

Author: mendelsshop

clippy_lints/src/transmute/mod.rs

@@ -53,7 +53,7 @@ declare_clippy_lint! {
     ///
     /// ```ignore
     /// unsafe {
-    ///    std::mem::transmute::<Option<&i32>, Option<&mut i32>>(&Some(5));
+    ///    std::mem::transmute::<Option<&i32>, Option<&mut i32>>(Some(&5));
     /// }
     /// ```
     #[clippy::version = "1.92.0"]

tests/ui/mutable_adt_argument_transmute.rs

@@ -1,5 +1,8 @@
 #![warn(clippy::mutable_adt_argument_transmute)]
 
 fn main() {
-    // test code goes here
+    unsafe {
+        let _: Option<&mut i32> = std::mem::transmute(Some(&5i32));
+        //~^ mutable_adt_argument_transmute
+    }
 }

tests/ui/mutable_adt_argument_transmute.stderr

@@ -0,0 +1,11 @@
+error: transmute of type argument &i32 to &i32
+  --> tests/ui/mutable_adt_argument_transmute.rs:5:35
+   |
+LL |         let _: Option<&mut i32> = std::mem::transmute(Some(&5i32));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::mutable-adt-argument-transmute` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::mutable_adt_argument_transmute)]`
+
+error: aborting due to 1 previous error
+