ensure that we cannot use (wrapping_)offset to go from an int ptr to a real ptr

Author: RalfJung

tests/compile-fail/ptr_offset_int_plus_ptr.rs

@@ -0,0 +1,9 @@
+// error-pattern: pointer value as raw bytes
+
+fn main() {
+    let ptr = &mut *Box::new(0u32) as *mut u32;
+    // Can't start with an integer pointer and get to something usable
+    unsafe {
+        let _ = (1 as *mut u8).offset(ptr as isize);
+    }
+}

tests/compile-fail/ptr_wrapping_offset_int_plus_ptr.rs

@@ -0,0 +1,8 @@
+// error-pattern: pointer value as raw bytes
+
+fn main() {
+    let ptr = &mut *Box::new(0u32) as *mut u32;
+    // Can't start with an integer pointer and get to something usable
+    let ptr = (1 as *mut u8).wrapping_offset(ptr as isize);
+    let _ = unsafe { *ptr };
+}