Add tests for issues #10285, #10286, #10289, #10287

tests/ui/transmute_ptr_to_ptr.fixed

@@ -43,6 +43,9 @@ fn transmute_ptr_to_ptr() {
         //~^ 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
+        let u8_ref: &u8 = &0u8;
+        let u64_ref: &u64 = unsafe { &*(u8_ref as *const u8 as *const u64) };
+        //~^ ERROR: transmute from a reference to a reference
     }
 
     // these are recommendations for solving the above; if these lint we need to update

tests/ui/transmute_ptr_to_ptr.rs

@@ -43,6 +43,9 @@ fn transmute_ptr_to_ptr() {
         //~^ ERROR: transmute from a reference to a reference
         let _: &GenericParam<f32> = std::mem::transmute(&GenericParam { t: 1u32 });
         //~^ ERROR: transmute from a reference to a reference
+        let u8_ref: &u8 = &0u8;
+        let u64_ref: &u64 = unsafe { std::mem::transmute(u8_ref) };
+        //~^ ERROR: transmute from a reference to a reference
     }
 
     // these are recommendations for solving the above; if these lint we need to update

tests/ui/transmute_ptr_to_ptr.stderr

@@ -37,5 +37,11 @@ error: transmute from a reference to a reference
 LL |         let _: &GenericParam<f32> = std::mem::transmute(&GenericParam { t: 1u32 });
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(&GenericParam { t: 1u32 } as *const GenericParam<u32> as *const GenericParam<f32>)`
 
-error: aborting due to 6 previous errors
+error: transmute from a reference to a reference
+  --> $DIR/transmute_ptr_to_ptr.rs:47:38
+   |
+LL |         let u64_ref: &u64 = unsafe { std::mem::transmute(u8_ref) };
+   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(u8_ref as *const u8 as *const u64)`
+
+error: aborting due to 7 previous errors
 

tests/ui/transmute_ref_to_ref.rs

@@ -0,0 +1,18 @@
+//@no-rustfix
+
+#![deny(clippy::transmute_ptr_to_ptr)]
+#![allow(dead_code)]
+
+fn main() {
+    unsafe {
+        let single_u64: &[u64] = &[0xDEAD_BEEF_DEAD_BEEF];
+        let bools: &[bool] = unsafe { std::mem::transmute(single_u64) };
+        //~^ ERROR: transmute from a reference to a reference
+        let a: &[u32] = &[0x12345678, 0x90ABCDEF, 0xFEDCBA09, 0x87654321];
+        let b: &[u8] = unsafe { std::mem::transmute(a) };
+        //~^ ERROR: transmute from a reference to a reference
+        let bytes = &[1u8, 2u8, 3u8, 4u8] as &[u8];
+        let alt_slice: &[u32] = unsafe { core::mem::transmute(bytes) };
+        //~^ ERROR: transmute from a reference to a reference
+    }
+}

tests/ui/transmute_ref_to_ref.stderr

@@ -0,0 +1,26 @@
+error: transmute from a reference to a reference
+  --> $DIR/transmute_ref_to_ref.rs:9:39
+   |
+LL |         let bools: &[bool] = unsafe { std::mem::transmute(single_u64) };
+   |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(single_u64 as *const [u64] as *const [bool])`
+   |
+note: the lint level is defined here
+  --> $DIR/transmute_ref_to_ref.rs:3:9
+   |
+LL | #![deny(clippy::transmute_ptr_to_ptr)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: transmute from a reference to a reference
+  --> $DIR/transmute_ref_to_ref.rs:12:33
+   |
+LL |         let b: &[u8] = unsafe { std::mem::transmute(a) };
+   |                                 ^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(a as *const [u32] as *const [u8])`
+
+error: transmute from a reference to a reference
+  --> $DIR/transmute_ref_to_ref.rs:15:42
+   |
+LL |         let alt_slice: &[u32] = unsafe { core::mem::transmute(bytes) };
+   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(bytes as *const [u8] as *const [u32])`
+
+error: aborting due to 3 previous errors
+