From a469ee1061fbccd4dda79e07017d35189e367b0e Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 27 Jun 2016 16:12:48 +0200
Subject: [PATCH] lint transmuting references to pointers

---
 clippy_lints/src/transmute.rs   | 17 +++++++++++++++++
 tests/compile-fail/transmute.rs | 15 +++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/clippy_lints/src/transmute.rs b/clippy_lints/src/transmute.rs
index 718111bee65..0d68789e0be 100644
--- a/clippy_lints/src/transmute.rs
+++ b/clippy_lints/src/transmute.rs
@@ -72,6 +72,23 @@ impl LateLintPass for Transmute {
                             e.span,
                             &format!("transmute from a type (`{}`) to itself", from_ty),
                         ),
+                        (&TyRef(_, rty), &TyRawPtr(ptr_ty)) => span_lint_and_then(
+                            cx,
+                            USELESS_TRANSMUTE,
+                            e.span,
+                            "transmute from a reference to a pointer",
+                            |db| {
+                                if let Some(arg) = snippet_opt(cx, args[0].span) {
+                                    let sugg = if ptr_ty == rty {
+                                        format!("{} as {}", arg, to_ty)
+                                    } else {
+                                        format!("{} as {} as {}", arg, cx.tcx.mk_ptr(rty), to_ty)
+                                    };
+
+                                    db.span_suggestion(e.span, "try", sugg);
+                                }
+                            },
+                        ),
                         (&TyRawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
                             cx,
                             CROSSPOINTER_TRANSMUTE,
diff --git a/tests/compile-fail/transmute.rs b/tests/compile-fail/transmute.rs
index ad97410cf65..4cd19f9bec9 100644
--- a/tests/compile-fail/transmute.rs
+++ b/tests/compile-fail/transmute.rs
@@ -21,6 +21,21 @@ unsafe fn _generic<'a, T, U: 'a>(t: &'a T) {
     //~^ ERROR transmute from a type (`&'a T`) to itself
 
     let _: &'a U = core::intrinsics::transmute(t);
+
+    let _: *const T = core::intrinsics::transmute(t);
+    //~^ ERROR transmute from a reference to a pointer
+    //~| HELP try
+    //~| SUGGESTION = t as *const T
+
+    let _: *mut T = core::intrinsics::transmute(t);
+    //~^ ERROR transmute from a reference to a pointer
+    //~| HELP try
+    //~| SUGGESTION = t as *const T as *mut T
+
+    let _: *const U = core::intrinsics::transmute(t);
+    //~^ ERROR transmute from a reference to a pointer
+    //~| HELP try
+    //~| SUGGESTION = t as *const T as *const U
 }
 
 #[deny(transmute_ptr_to_ref)]