From c02dff716785721c4c992d03ee816d764fb43402 Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Tue, 15 Feb 2022 11:29:02 -0500
Subject: [PATCH] Fix `transmute_undefined_repr` when converting between a
 pointer and a type containing a pointer

---
 .../src/transmute/transmute_undefined_repr.rs |  3 ++-
 tests/ui/transmute_undefined_repr.rs          | 14 ++++++++++
 tests/ui/transmute_undefined_repr.stderr      | 26 ++++++++++++++++---
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/clippy_lints/src/transmute/transmute_undefined_repr.rs b/clippy_lints/src/transmute/transmute_undefined_repr.rs
index 89439862f..74ea7a3b8 100644
--- a/clippy_lints/src/transmute/transmute_undefined_repr.rs
+++ b/clippy_lints/src/transmute/transmute_undefined_repr.rs
@@ -273,7 +273,8 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
                     ReducedTy::UnorderedFields(ty)
                 }
             },
-            ty::Ref(..) | ty::RawPtr(_) => ReducedTy::Ref(ty),
+            ty::Ref(_, ty, _) => ReducedTy::Ref(ty),
+            ty::RawPtr(ty) => ReducedTy::Ref(ty.ty),
             _ => ReducedTy::Other(ty),
         };
     }
diff --git a/tests/ui/transmute_undefined_repr.rs b/tests/ui/transmute_undefined_repr.rs
index f0383a03f..0916da819 100644
--- a/tests/ui/transmute_undefined_repr.rs
+++ b/tests/ui/transmute_undefined_repr.rs
@@ -44,5 +44,19 @@ fn main() {
         // issue #8417
         let _: Ty2C<Ty2<u32, i32>, ()> = core::mem::transmute(value::<Ty2<u32, i32>>()); // Ok, Ty2 types are the same
         let _: Ty2<u32, i32> = core::mem::transmute(value::<Ty2C<Ty2<u32, i32>, ()>>()); // Ok, Ty2 types are the same
+
+        // Ty2 types are the same
+        let _: &'static mut Ty2<u32, u32> = core::mem::transmute(value::<Box<Ty2<u32, u32>>>()); // Ok
+        // Ty2 types are the same
+        let _: Box<Ty2<u32, u32>> = core::mem::transmute(value::<&'static mut Ty2<u32, u32>>()); // Ok
+        let _: *mut Ty2<u32, u32> = core::mem::transmute(value::<Box<Ty2<u32, u32>>>()); // Ok, Ty2 types are the same
+        let _: Box<Ty2<u32, u32>> = core::mem::transmute(value::<*mut Ty2<u32, u32>>()); // Ok, Ty2 types are the same
+
+        // Different Ty2 instances
+        let _: &'static mut Ty2<u32, f32> = core::mem::transmute(value::<Box<Ty2<u32, u32>>>()); // Lint
+        // Different Ty2 instances
+        let _: Box<Ty2<u32, u32>> = core::mem::transmute(value::<&'static mut Ty2<u32, f32>>()); // Lint
+
+
     }
 }
diff --git a/tests/ui/transmute_undefined_repr.stderr b/tests/ui/transmute_undefined_repr.stderr
index 040c63c7a..98035305e 100644
--- a/tests/ui/transmute_undefined_repr.stderr
+++ b/tests/ui/transmute_undefined_repr.stderr
@@ -28,17 +28,37 @@ LL |         let _: Ty<Ty2<u32, i32>> = core::mem::transmute(value::<Ty2<u32, f3
    |
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
-error: transmute to `&Ty2<u32, f32>` which has an undefined layout
+error: transmute from `Ty<&Ty2<u32, i32>>` to `&Ty2<u32, f32>`, both of which have an undefined layout
   --> $DIR/transmute_undefined_repr.rs:35:33
    |
 LL |         let _: &Ty2<u32, f32> = core::mem::transmute(value::<Ty<&Ty2<u32, i32>>>()); // Lint, different Ty2 instances
    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Ty2`) may have different layouts
 
-error: transmute from `&Ty2<u32, f32>` which has an undefined layout
+error: transmute from `&Ty2<u32, f32>` to `Ty<&Ty2<u32, i32>>`, both of which have an undefined layout
   --> $DIR/transmute_undefined_repr.rs:36:37
    |
 LL |         let _: Ty<&Ty2<u32, i32>> = core::mem::transmute(value::<&Ty2<u32, f32>>()); // Lint, different Ty2 instances
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Ty2`) may have different layouts
 
-error: aborting due to 6 previous errors
+error: transmute from `std::boxed::Box<Ty2<u32, u32>>` to `&mut Ty2<u32, f32>`, both of which have an undefined layout
+  --> $DIR/transmute_undefined_repr.rs:56:45
+   |
+LL |         let _: &'static mut Ty2<u32, f32> = core::mem::transmute(value::<Box<Ty2<u32, u32>>>()); // Lint
+   |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Ty2`) may have different layouts
+
+error: transmute from `&mut Ty2<u32, f32>` to `std::boxed::Box<Ty2<u32, u32>>`, both of which have an undefined layout
+  --> $DIR/transmute_undefined_repr.rs:58:37
+   |
+LL |         let _: Box<Ty2<u32, u32>> = core::mem::transmute(value::<&'static mut Ty2<u32, f32>>()); // Lint
+   |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Ty2`) may have different layouts
+
+error: aborting due to 8 previous errors