From 326994dfe63ae8a892cdfadc107cd36c113f6bb1 Mon Sep 17 00:00:00 2001 From: Guillaume Gomez Date: Wed, 8 Jan 2020 14:24:25 +0100 Subject: [PATCH] Improve E0184 explanation --- src/librustc_error_codes/error_codes/E0184.md | 22 +++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/src/librustc_error_codes/error_codes/E0184.md b/src/librustc_error_codes/error_codes/E0184.md index e7fa8dfd8313e..4624f9e5b8531 100644 --- a/src/librustc_error_codes/error_codes/E0184.md +++ b/src/librustc_error_codes/error_codes/E0184.md @@ -1,6 +1,20 @@ -Explicitly implementing both Drop and Copy for 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][iss20126]), so -it has been disabled for now. +The `Copy` trait was implemented on a type with a `Drop` implementation. + +Erroneous code example: + +```compile_fail,E0184 +#[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][iss20126]), so it has been disabled for now. [iss20126]: https://github.com/rust-lang/rust/issues/20126