Merge pull request #5 from dtolnay-contrib/invalid

Fix read from invalidated ptr

src/lib.rs

@@ -27,7 +27,11 @@
 //! # }
 //! ```
 
-use core::{any::TypeId, marker::PhantomData, mem};
+use core::{
+    any::TypeId,
+    marker::PhantomData,
+    mem::{self, ManuallyDrop},
+};
 
 /// Untypes your types. For documentation see the root of this crate.
 ///
@@ -36,9 +40,8 @@ use core::{any::TypeId, marker::PhantomData, mem};
 /// This should not be used with types with lifetimes.
 pub unsafe fn unty<Src, Target: 'static>(x: Src) -> Result<Target, Src> {
     if type_equal::<Src, Target>() {
-        let ptr = &x as *const Src as *const Target;
-        mem::forget(x); // we're going to copy this, so don't run the destructor
-        Ok(core::ptr::read(ptr))
+        let x = ManuallyDrop::new(x);
+        Ok(mem::transmute_copy::<Src, Target>(&x))
     } else {
         Err(x)
     }