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, 16 insertions, 3 deletions

diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
index 06105ca61ca..ffc26738dd7 100644
--- a/src/libtest/lib.rs
+++ b/src/libtest/lib.rs
@@ -109,7 +109,13 @@ impl Show for TestName {
 }
 
 #[deriving(Clone)]
-enum NamePadding { PadNone, PadOnLeft, PadOnRight }
+enum NamePadding {
+    PadNone,
+    PadOnLeft,
+    PadOnRight,
+}
+
+impl Copy for NamePadding {}
 
 impl TestDesc {
     fn padded_name(&self, column_count: uint, align: NamePadding) -> String {
@@ -179,13 +185,14 @@ impl fmt::Show for TestFn {
 /// This is feed into functions marked with `#[bench]` to allow for
 /// set-up & tear-down before running a piece of code repeatedly via a
 /// call to `iter`.
+#[deriving(Copy)]
 pub struct Bencher {
     iterations: u64,
     dur: Duration,
     pub bytes: u64,
 }
 
-#[deriving(Clone, Show, PartialEq, Eq, Hash)]
+#[deriving(Copy, Clone, Show, PartialEq, Eq, Hash)]
 pub enum ShouldFail {
     No,
     Yes(Option<&'static str>)
@@ -212,6 +219,8 @@ pub struct Metric {
     noise: f64
 }
 
+impl Copy for Metric {}
+
 impl Metric {
     pub fn new(value: f64, noise: f64) -> Metric {
         Metric {value: value, noise: noise}
@@ -238,6 +247,8 @@ pub enum MetricChange {
     Regression(f64)
 }
 
+impl Copy for MetricChange {}
+
 pub type MetricDiff = TreeMap<String,MetricChange>;
 
 // The default console test runner. It accepts the command line
@@ -280,6 +291,8 @@ pub enum ColorConfig {
     NeverColor,
 }
 
+impl Copy for ColorConfig {}
+
 pub struct TestOpts {
     pub filter: Option<Regex>,
     pub run_ignored: bool,
@@ -1135,7 +1148,7 @@ pub fn run_test(opts: &TestOpts,
             return;
         }
         StaticBenchFn(benchfn) => {
-            let bs = ::bench::benchmark(|harness| benchfn(harness));
+            let bs = ::bench::benchmark(|harness| (benchfn.clone())(harness));
             monitor_ch.send((desc, TrBench(bs), Vec::new()));
             return;
         }