1 files changed, 70 insertions, 0 deletions
diff --git a/tests/ui/transmute_ptr_to_ptr.fixed b/tests/ui/transmute_ptr_to_ptr.fixed
new file mode 100644
index 00000000000..19abced98bb
--- /dev/null
+++ b/tests/ui/transmute_ptr_to_ptr.fixed
@@ -0,0 +1,70 @@
+#![warn(clippy::transmute_ptr_to_ptr)]
+#![allow(clippy::borrow_as_ptr)]
+
+// Make sure we can modify lifetimes, which is one of the recommended uses
+// of transmute
+
+// Make sure we can do static lifetime transmutes
+unsafe fn transmute_lifetime_to_static<'a, T>(t: &'a T) -> &'static T {
+    std::mem::transmute::<&'a T, &'static T>(t)
+}
+
+// Make sure we can do non-static lifetime transmutes
+unsafe fn transmute_lifetime<'a, 'b, T>(t: &'a T, u: &'b T) -> &'b T {
+    std::mem::transmute::<&'a T, &'b T>(t)
+}
+
+struct LifetimeParam<'a> {
+    s: &'a str,
+}
+
+struct GenericParam<T> {
+    t: T,
+}
+
+fn transmute_ptr_to_ptr() {
+    let ptr = &1u32 as *const u32;
+    let mut_ptr = &mut 1u32 as *mut u32;
+    unsafe {
+        // pointer-to-pointer transmutes; bad
+        let _: *const f32 = ptr as *const f32;
+        //~^ ERROR: transmute from a pointer to a pointer
+        //~| NOTE: `-D clippy::transmute-ptr-to-ptr` implied by `-D warnings`
+        let _: *mut f32 = mut_ptr as *mut f32;
+        //~^ ERROR: transmute from a pointer to a pointer
+        // ref-ref transmutes; bad
+        let _: &f32 = &*(&1u32 as *const u32 as *const f32);
+        //~^ ERROR: transmute from a reference to a reference
+        let _: &f64 = &*(&1f32 as *const f32 as *const f64);
+        //~^ ERROR: transmute from a reference to a reference
+        //:^ this test is here because both f32 and f64 are the same TypeVariant, but they are not
+        // the same type
+        let _: &mut f32 = &mut *(&mut 1u32 as *mut u32 as *mut f32);
+        //~^ ERROR: transmute from a reference to a reference
+        let _: &GenericParam<f32> = &*(&GenericParam { t: 1u32 } as *const GenericParam<u32> as *const GenericParam<f32>);
+        //~^ ERROR: transmute from a reference to a reference
+    }
+
+    // these are recommendations for solving the above; if these lint we need to update
+    // those suggestions
+    let _ = ptr as *const f32;
+    let _ = mut_ptr as *mut f32;
+    let _ = unsafe { &*(&1u32 as *const u32 as *const f32) };
+    let _ = unsafe { &mut *(&mut 1u32 as *mut u32 as *mut f32) };
+
+    // transmute internal lifetimes, should not lint
+    let s = "hello world".to_owned();
+    let lp = LifetimeParam { s: &s };
+    let _: &LifetimeParam<'static> = unsafe { std::mem::transmute(&lp) };
+    let _: &GenericParam<&LifetimeParam<'static>> = unsafe { std::mem::transmute(&GenericParam { t: &lp }) };
+}
+
+// dereferencing raw pointers in const contexts, should not lint as it's unstable (issue 5959)
+const _: &() = {
+    struct Zst;
+    let zst = &Zst;
+
+    unsafe { std::mem::transmute::<&'static Zst, &'static ()>(zst) }
+};
+
+fn main() {}