Error code E0184

The Copy trait was implemented on a type with a Drop implementation.

Erroneous code example:

#![allow(unused)] fn main() { #[derive(Copy)] struct Foo; // error! impl Drop for Foo { fn drop(&mut self) { } } }

Explicitly implementing both Drop and Copy trait on a type is currently disallowed. This feature can make some sense in theory, but the current implementation is incorrect and can lead to memory unsafety (see issue #20126), so it has been disabled for now.