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]

1 files changed, 9 insertions, 0 deletions

diff --git a/src/libcore/raw.rs b/src/libcore/raw.rs
index d156f71462d..db1be94b2b8 100644
--- a/src/libcore/raw.rs
+++ b/src/libcore/raw.rs
@@ -18,6 +18,7 @@
 //!
 //! Their definition should always match the ABI defined in `rustc::back::abi`.
 
+use kinds::Copy;
 use mem;
 use kinds::Sized;
 
@@ -28,6 +29,8 @@ pub struct Slice<T> {
     pub len: uint,
 }
 
+impl<T> Copy for Slice<T> {}
+
 /// The representation of a Rust closure
 #[repr(C)]
 pub struct Closure {
@@ -35,6 +38,8 @@ pub struct Closure {
     pub env: *mut (),
 }
 
+impl Copy for Closure {}
+
 /// The representation of a Rust procedure (`proc()`)
 #[repr(C)]
 pub struct Procedure {
@@ -42,6 +47,8 @@ pub struct Procedure {
     pub env: *mut (),
 }
 
+impl Copy for Procedure {}
+
 /// The representation of a Rust trait object.
 ///
 /// This struct does not have a `Repr` implementation
@@ -52,6 +59,8 @@ pub struct TraitObject {
     pub vtable: *mut (),
 }
 
+impl Copy for TraitObject {}
+
 /// This trait is meant to map equivalences between raw structs and their
 /// corresponding rust values.
 pub trait Repr<T> for Sized? {