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]

15 files changed, 125 insertions, 22 deletions

diff --git a/src/libstd/ascii.rs b/src/libstd/ascii.rs
index 2872f74cf88..23eb367dbd1 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -18,6 +18,7 @@
 use core::kinds::Sized;
 use fmt;
 use iter::IteratorExt;
+use kinds::Copy;
 use mem;
 use option::Option;
 use option::Option::{Some, None};
@@ -30,6 +31,8 @@ use vec::Vec;
 #[deriving(Clone, PartialEq, PartialOrd, Ord, Eq, Hash)]
 pub struct Ascii { chr: u8 }
 
+impl Copy for Ascii {}
+
 impl Ascii {
     /// Converts an ascii character into a `u8`.
     #[inline]
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);
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index de06a1e0bbd..ef4cabedc47 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -16,7 +16,7 @@ use clone::Clone;
 use cmp;
 use hash::{Hash, Hasher};
 use iter::{Iterator, count};
-use kinds::{Sized, marker};
+use kinds::{Copy, Sized, marker};
 use mem::{min_align_of, size_of};
 use mem;
 use num::{Int, UnsignedInt};
@@ -81,12 +81,16 @@ struct RawBucket<K, V> {
     val:  *mut V
 }
 
+impl<K,V> Copy for RawBucket<K,V> {}
+
 pub struct Bucket<K, V, M> {
     raw:   RawBucket<K, V>,
     idx:   uint,
     table: M
 }
 
+impl<K,V,M:Copy> Copy for Bucket<K,V,M> {}
+
 pub struct EmptyBucket<K, V, M> {
     raw:   RawBucket<K, V>,
     idx:   uint,
diff --git a/src/libstd/comm/mod.rs b/src/libstd/comm/mod.rs
index d291ed72567..6cff5a3dd23 100644
--- a/src/libstd/comm/mod.rs
+++ b/src/libstd/comm/mod.rs
@@ -405,6 +405,8 @@ pub enum TryRecvError {
     Disconnected,
 }
 
+impl Copy for TryRecvError {}
+
 /// This enumeration is the list of the possible error outcomes for the
 /// `SyncSender::try_send` method.
 #[deriving(PartialEq, Clone, Show)]
diff --git a/src/libstd/dynamic_lib.rs b/src/libstd/dynamic_lib.rs
index aa0c8b53c2e..5609fbf16cd 100644
--- a/src/libstd/dynamic_lib.rs
+++ b/src/libstd/dynamic_lib.rs
@@ -29,7 +29,10 @@ use str;
 use string::String;
 use vec::Vec;
 
-pub struct DynamicLibrary { handle: *mut u8 }
+#[allow(missing_copy_implementations)]
+pub struct DynamicLibrary {
+    handle: *mut u8
+}
 
 impl Drop for DynamicLibrary {
     fn drop(&mut self) {
@@ -210,6 +213,7 @@ pub mod dl {
 
     use c_str::{CString, ToCStr};
     use libc;
+    use kinds::Copy;
     use ptr;
     use result::*;
     use string::String;
@@ -262,6 +266,8 @@ pub mod dl {
         Local = 0,
     }
 
+    impl Copy for Rtld {}
+
     #[link_name = "dl"]
     extern {
         fn dlopen(filename: *const libc::c_char,
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index d43a7a66c5b..dc212e7cab3 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -231,6 +231,7 @@ use error::{FromError, Error};
 use fmt;
 use int;
 use iter::{Iterator, IteratorExt};
+use kinds::Copy;
 use mem::transmute;
 use ops::{BitOr, BitXor, BitAnd, Sub, Not};
 use option::Option;
@@ -420,6 +421,8 @@ pub enum IoErrorKind {
     NoProgress,
 }
 
+impl Copy for IoErrorKind {}
+
 /// A trait that lets you add a `detail` to an IoError easily
 trait UpdateIoError<T> {
     /// Returns an IoError with updated description and detail
@@ -1560,6 +1563,8 @@ pub enum SeekStyle {
     SeekCur,
 }
 
+impl Copy for SeekStyle {}
+
 /// An object implementing `Seek` internally has some form of cursor which can
 /// be moved within a stream of bytes. The stream typically has a fixed size,
 /// allowing seeking relative to either end.
@@ -1682,6 +1687,8 @@ pub enum FileMode {
     Truncate,
 }
 
+impl Copy for FileMode {}
+
 /// Access permissions with which the file should be opened. `File`s
 /// opened with `Read` will return an error if written to.
 pub enum FileAccess {
@@ -1693,6 +1700,8 @@ pub enum FileAccess {
     ReadWrite,
 }
 
+impl Copy for FileAccess {}
+
 /// Different kinds of files which can be identified by a call to stat
 #[deriving(PartialEq, Show, Hash, Clone)]
 pub enum FileType {
@@ -1715,6 +1724,8 @@ pub enum FileType {
     Unknown,
 }
 
+impl Copy for FileType {}
+
 /// A structure used to describe metadata information about a file. This
 /// structure is created through the `stat` method on a `Path`.
 ///
@@ -1766,6 +1777,8 @@ pub struct FileStat {
     pub unstable: UnstableFileStat,
 }
 
+impl Copy for FileStat {}
+
 /// This structure represents all of the possible information which can be
 /// returned from a `stat` syscall which is not contained in the `FileStat`
 /// structure. This information is not necessarily platform independent, and may
@@ -1795,6 +1808,8 @@ pub struct UnstableFileStat {
     pub gen: u64,
 }
 
+impl Copy for UnstableFileStat {}
+
 bitflags! {
     #[doc = "A set of permissions for a file or directory is represented"]
     #[doc = "by a set of flags which are or'd together."]
@@ -1889,6 +1904,8 @@ bitflags! {
     }
 }
 
+impl Copy for FilePermission {}
+
 impl Default for FilePermission {
     #[inline]
     fn default() -> FilePermission { FilePermission::empty() }
diff --git a/src/libstd/io/net/addrinfo.rs b/src/libstd/io/net/addrinfo.rs
index fea8372733c..fc81ab7b57a 100644
--- a/src/libstd/io/net/addrinfo.rs
+++ b/src/libstd/io/net/addrinfo.rs
@@ -22,6 +22,7 @@ pub use self::Protocol::*;
 use iter::IteratorExt;
 use io::{IoResult};
 use io::net::ip::{SocketAddr, IpAddr};
+use kinds::Copy;
 use option::Option;
 use option::Option::{Some, None};
 use sys;
@@ -32,6 +33,8 @@ pub enum SocketType {
     Stream, Datagram, Raw
 }
 
+impl Copy for SocketType {}
+
 /// Flags which can be or'd into the `flags` field of a `Hint`. These are used
 /// to manipulate how a query is performed.
 ///
@@ -46,12 +49,16 @@ pub enum Flag {
     V4Mapped,
 }
 
+impl Copy for Flag {}
+
 /// A transport protocol associated with either a hint or a return value of
 /// `lookup`
 pub enum Protocol {
     TCP, UDP
 }
 
+impl Copy for Protocol {}
+
 /// This structure is used to provide hints when fetching addresses for a
 /// remote host to control how the lookup is performed.
 ///
@@ -64,6 +71,8 @@ pub struct Hint {
     pub flags: uint,
 }
 
+impl Copy for Hint {}
+
 pub struct Info {
     pub address: SocketAddr,
     pub family: uint,
@@ -72,6 +81,8 @@ pub struct Info {
     pub flags: uint,
 }
 
+impl Copy for Info {}
+
 /// Easy name resolution. Given a hostname, returns the list of IP addresses for
 /// that hostname.
 pub fn get_host_addresses(host: &str) -> IoResult<Vec<IpAddr>> {
diff --git a/src/libstd/io/net/ip.rs b/src/libstd/io/net/ip.rs
index 3fa6f4a6091..f59dd37c0da 100644
--- a/src/libstd/io/net/ip.rs
+++ b/src/libstd/io/net/ip.rs
@@ -18,6 +18,7 @@
 pub use self::IpAddr::*;
 
 use fmt;
+use kinds::Copy;
 use io::{mod, IoResult, IoError};
 use io::net;
 use iter::{Iterator, IteratorExt};
@@ -36,6 +37,8 @@ pub enum IpAddr {
     Ipv6Addr(u16, u16, u16, u16, u16, u16, u16, u16)
 }
 
+impl Copy for IpAddr {}
+
 impl fmt::Show for IpAddr {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match *self {
@@ -67,6 +70,8 @@ pub struct SocketAddr {
     pub port: Port,
 }
 
+impl Copy for SocketAddr {}
+
 impl fmt::Show for SocketAddr {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self.ip {
diff --git a/src/libstd/io/process.rs b/src/libstd/io/process.rs
index 61ebfb06c71..c46a6e82e44 100644
--- a/src/libstd/io/process.rs
+++ b/src/libstd/io/process.rs
@@ -480,6 +480,8 @@ pub enum StdioContainer {
     CreatePipe(bool /* readable */, bool /* writable */),
 }
 
+impl Copy for StdioContainer {}
+
 /// Describes the result of a process after it has terminated.
 /// Note that Windows have no signals, so the result is usually ExitStatus.
 #[deriving(PartialEq, Eq, Clone)]
@@ -491,6 +493,8 @@ pub enum ProcessExit {
     ExitSignal(int),
 }
 
+impl Copy for ProcessExit {}
+
 impl fmt::Show for ProcessExit {
     /// Format a ProcessExit enum, to nicely present the information.
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
diff --git a/src/libstd/io/util.rs b/src/libstd/io/util.rs
index e78bd1dd33f..faa52226a03 100644
--- a/src/libstd/io/util.rs
+++ b/src/libstd/io/util.rs
@@ -83,6 +83,8 @@ impl<R: Buffer> Buffer for LimitReader<R> {
 /// A `Writer` which ignores bytes written to it, like /dev/null.
 pub struct NullWriter;
 
+impl Copy for NullWriter {}
+
 impl Writer for NullWriter {
     #[inline]
     fn write(&mut self, _buf: &[u8]) -> io::IoResult<()> { Ok(()) }
@@ -91,6 +93,8 @@ impl Writer for NullWriter {
 /// A `Reader` which returns an infinite stream of 0 bytes, like /dev/zero.
 pub struct ZeroReader;
 
+impl Copy for ZeroReader {}
+
 impl Reader for ZeroReader {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> io::IoResult<uint> {
@@ -111,6 +115,8 @@ impl Buffer for ZeroReader {
 /// A `Reader` which is always at EOF, like /dev/null.
 pub struct NullReader;
 
+impl Copy for NullReader {}
+
 impl Reader for NullReader {
     #[inline]
     fn read(&mut self, _buf: &mut [u8]) -> io::IoResult<uint> {
diff --git a/src/libstd/num/strconv.rs b/src/libstd/num/strconv.rs
index c87f40f351b..1c9826ff5ac 100644
--- a/src/libstd/num/strconv.rs
+++ b/src/libstd/num/strconv.rs
@@ -18,6 +18,7 @@ pub use self::SignFormat::*;
 
 use char;
 use char::Char;
+use kinds::Copy;
 use num;
 use num::{Int, Float, FPNaN, FPInfinite, ToPrimitive};
 use slice::{SlicePrelude, CloneSliceAllocPrelude};
@@ -38,6 +39,8 @@ pub enum ExponentFormat {
     ExpBin,
 }
 
+impl Copy for ExponentFormat {}
+
 /// The number of digits used for emitting the fractional part of a number, if
 /// any.
 pub enum SignificantDigits {
@@ -55,6 +58,8 @@ pub enum SignificantDigits {
     DigExact(uint)
 }
 
+impl Copy for SignificantDigits {}
+
 /// How to emit the sign of a number.
 pub enum SignFormat {
     /// No sign will be printed. The exponent sign will also be emitted.
@@ -67,25 +72,33 @@ pub enum SignFormat {
     SignAll,
 }
 
-/// Converts an integral number to its string representation as a byte vector.
-/// This is meant to be a common base implementation for all integral string
-/// conversion functions like `to_string()` or `to_str_radix()`.
-///
-/// # Arguments
-///
-/// - `num`           - The number to convert. Accepts any number that
-///                     implements the numeric traits.
-/// - `radix`         - Base to use. Accepts only the values 2-36.
-/// - `sign`          - How to emit the sign. Options are:
-///     - `SignNone`: No sign at all. Basically emits `abs(num)`.
-///     - `SignNeg`:  Only `-` on negative values.
-///     - `SignAll`:  Both `+` on positive, and `-` on negative numbers.
-/// - `f`             - a callback which will be invoked for each ascii character
-///                     which composes the string representation of this integer
-///
-/// # Panics
-///
-/// - Panics if `radix` < 2 or `radix` > 36.
+impl Copy for SignFormat {}
+
+/**
+ * Converts an integral number to its string representation as a byte vector.
+ * This is meant to be a common base implementation for all integral string
+ * conversion functions like `to_string()` or `to_str_radix()`.
+ *
+ * # Arguments
+ * - `num`           - The number to convert. Accepts any number that
+ *                     implements the numeric traits.
+ * - `radix`         - Base to use. Accepts only the values 2-36.
+ * - `sign`          - How to emit the sign. Options are:
+ *     - `SignNone`: No sign at all. Basically emits `abs(num)`.
+ *     - `SignNeg`:  Only `-` on negative values.
+ *     - `SignAll`:  Both `+` on positive, and `-` on negative numbers.
+ * - `f`             - a callback which will be invoked for each ascii character
+ *                     which composes the string representation of this integer
+ *
+ * # Return value
+ * A tuple containing the byte vector, and a boolean flag indicating
+ * whether it represents a special value like `inf`, `-inf`, `NaN` or not.
+ * It returns a tuple because there can be ambiguity between a special value
+ * and a number representation at higher bases.
+ *
+ * # Failure
+ * - Fails if `radix` < 2 or `radix` > 36.
+ */
 fn int_to_str_bytes_common<T: Int>(num: T, radix: uint, sign: SignFormat, f: |u8|) {
     assert!(2 <= radix && radix <= 36);
 
diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index 2b904acb565..f298ec74f6a 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -36,6 +36,7 @@ use error::{FromError, Error};
 use fmt;
 use io::{IoResult, IoError};
 use iter::{Iterator, IteratorExt};
+use kinds::Copy;
 use libc::{c_void, c_int};
 use libc;
 use boxed::Box;
@@ -619,6 +620,8 @@ pub struct Pipe {
     pub writer: c_int,
 }
 
+impl Copy for Pipe {}
+
 /// Creates a new low-level OS in-memory pipe.
 ///
 /// This function can fail to succeed if there are no more resources available
@@ -1185,6 +1188,9 @@ pub struct MemoryMap {
     kind: MemoryMapKind,
 }
 
+#[cfg(not(stage0))]
+impl Copy for MemoryMap {}
+
 /// Type of memory map
 pub enum MemoryMapKind {
     /// Virtual memory map. Usually used to change the permissions of a given
@@ -1196,6 +1202,8 @@ pub enum MemoryMapKind {
     MapVirtual
 }
 
+impl Copy for MemoryMapKind {}
+
 /// Options the memory map is created with
 pub enum MapOption {
     /// The memory should be readable
@@ -1219,6 +1227,8 @@ pub enum MapOption {
     MapNonStandardFlags(c_int),
 }
 
+impl Copy for MapOption {}
+
 /// Possible errors when creating a map.
 pub enum MapError {
     /// ## The following are POSIX-specific
@@ -1264,6 +1274,8 @@ pub enum MapError {
     ErrMapViewOfFile(uint)
 }
 
+impl Copy for MapError {}
+
 impl fmt::Show for MapError {
     fn fmt(&self, out: &mut fmt::Formatter) -> fmt::Result {
         let str = match *self {
diff --git a/src/libstd/path/windows.rs b/src/libstd/path/windows.rs
index b53e6b2a5e0..ea522536d22 100644
--- a/src/libstd/path/windows.rs
+++ b/src/libstd/path/windows.rs
@@ -22,6 +22,7 @@ use hash;
 use io::Writer;
 use iter::{AdditiveIterator, DoubleEndedIteratorExt, Extend};
 use iter::{Iterator, IteratorExt, Map};
+use kinds::Copy;
 use mem;
 use option::Option;
 use option::Option::{Some, None};
@@ -985,6 +986,8 @@ pub enum PathPrefix {
     DiskPrefix
 }
 
+impl Copy for PathPrefix {}
+
 fn parse_prefix<'a>(mut path: &'a str) -> Option<PathPrefix> {
     if path.starts_with("\\\\") {
         // \\
diff --git a/src/libstd/rand/mod.rs b/src/libstd/rand/mod.rs
index cc3c46f3610..a359fcf7a9f 100644
--- a/src/libstd/rand/mod.rs
+++ b/src/libstd/rand/mod.rs
@@ -225,6 +225,7 @@ use cell::RefCell;
 use clone::Clone;
 use io::IoResult;
 use iter::{Iterator, IteratorExt};
+use kinds::Copy;
 use mem;
 use rc::Rc;
 use result::Result::{Ok, Err};
@@ -245,7 +246,11 @@ pub mod reader;
 
 /// The standard RNG. This is designed to be efficient on the current
 /// platform.
-pub struct StdRng { rng: IsaacWordRng }
+pub struct StdRng {
+    rng: IsaacWordRng,
+}
+
+impl Copy for StdRng {}
 
 impl StdRng {
     /// Create a randomly seeded instance of `StdRng`.
diff --git a/src/libstd/time/duration.rs b/src/libstd/time/duration.rs
index 86c3a1fdd32..7e6065129a3 100644
--- a/src/libstd/time/duration.rs
+++ b/src/libstd/time/duration.rs
@@ -13,6 +13,7 @@
 #![experimental]
 
 use {fmt, i64};
+use kinds::Copy;
 use ops::{Add, Sub, Mul, Div, Neg};
 use option::Option;
 use option::Option::{Some, None};
@@ -64,6 +65,8 @@ pub const MAX: Duration = Duration {
     nanos: (i64::MAX % MILLIS_PER_SEC) as i32 * NANOS_PER_MILLI
 };
 
+impl Copy for Duration {}
+
 impl Duration {
     /// Makes a new `Duration` with given number of weeks.
     /// Equivalent to `Duration::seconds(weeks * 7 * 24 * 60 * 60), with overflow checks.