From 096a28607fb80c91e6e2ca64d9ef44c4e550e96c Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Fri, 5 Dec 2014 17:01:33 -0800
Subject: librustc: Make `Copy` opt-in.

This change makes the compiler no longer infer whether types (structures
and enumerations) implement the `Copy` trait (and thus are implicitly
copyable). Rather, you must implement `Copy` yourself via `impl Copy for
MyType {}`.

A new warning has been added, `missing_copy_implementations`, to warn
you if a non-generic public type has been added that could have
implemented `Copy` but didn't.

For convenience, you may *temporarily* opt out of this behavior by using
`#![feature(opt_out_copy)]`. Note though that this feature gate will never be
accepted and will be removed by the time that 1.0 is released, so you should
transition your code away from using it.

This breaks code like:

    #[deriving(Show)]
    struct Point2D {
        x: int,
        y: int,
    }

    fn main() {
        let mypoint = Point2D {
            x: 1,
            y: 1,
        };
        let otherpoint = mypoint;
        println!("{}{}", mypoint, otherpoint);
    }

Change this code to:

    #[deriving(Show)]
    struct Point2D {
        x: int,
        y: int,
    }

    impl Copy for Point2D {}

    fn main() {
        let mypoint = Point2D {
            x: 1,
            y: 1,
        };
        let otherpoint = mypoint;
        println!("{}{}", mypoint, otherpoint);
    }

This is the backwards-incompatible part of #13231.

Part of RFC #3.

[breaking-change]
---
 src/libstd/bitflags.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'src/libstd/bitflags.rs')

diff --git a/src/libstd/bitflags.rs b/src/libstd/bitflags.rs
index 8a90c06f038..ffcd6505dad 100644
--- a/src/libstd/bitflags.rs
+++ b/src/libstd/bitflags.rs
@@ -33,6 +33,8 @@
 ///     }
 /// }
 ///
+/// impl Copy for Flags {}
+///
 /// fn main() {
 ///     let e1 = FLAG_A | FLAG_C;
 ///     let e2 = FLAG_B | FLAG_C;
@@ -55,6 +57,8 @@
 ///     }
 /// }
 ///
+/// impl Copy for Flags {}
+///
 /// impl Flags {
 ///     pub fn clear(&mut self) {
 ///         self.bits = 0;  // The `bits` field can be accessed from within the
@@ -260,6 +264,7 @@ macro_rules! bitflags {
 #[cfg(test)]
 #[allow(non_upper_case_globals)]
 mod tests {
+    use kinds::Copy;
     use hash;
     use option::Option::{Some, None};
     use ops::{BitOr, BitAnd, BitXor, Sub, Not};
@@ -283,12 +288,16 @@ mod tests {
         }
     }
 
+    impl Copy for Flags {}
+
     bitflags! {
         flags AnotherSetOfFlags: i8 {
             const AnotherFlag = -1_i8,
         }
     }
 
+    impl Copy for AnotherSetOfFlags {}
+
     #[test]
     fn test_bits(){
         assert_eq!(Flags::empty().bits(), 0x00000000);
-- 
cgit 1.4.1-3-g733a5