add libcore from 2016-04-11 nightly

1 files changed, 164 insertions, 0 deletions

diff --git a/libcore/default.rs b/libcore/default.rs
new file mode 100644
index 0000000..12c4a5c
--- /dev/null
+++ b/libcore/default.rs
@@ -0,0 +1,164 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `Default` trait for types which may have meaningful default values.
+//!
+//! Sometimes, you want to fall back to some kind of default value, and
+//! don't particularly care what it is. This comes up often with `struct`s
+//! that define a set of options:
+//!
+//! ```
+//! # #[allow(dead_code)]
+//! struct SomeOptions {
+//!     foo: i32,
+//!     bar: f32,
+//! }
+//! ```
+//!
+//! How can we define some default values? You can use `Default`:
+//!
+//! ```
+//! # #[allow(dead_code)]
+//! #[derive(Default)]
+//! struct SomeOptions {
+//!     foo: i32,
+//!     bar: f32,
+//! }
+//!
+//!
+//! fn main() {
+//!     let options: SomeOptions = Default::default();
+//! }
+//! ```
+//!
+//! Now, you get all of the default values. Rust implements `Default` for various primitives types.
+//! If you have your own type, you need to implement `Default` yourself:
+//!
+//! ```
+//! # #![allow(dead_code)]
+//! enum Kind {
+//!     A,
+//!     B,
+//!     C,
+//! }
+//!
+//! impl Default for Kind {
+//!     fn default() -> Kind { Kind::A }
+//! }
+//!
+//! #[derive(Default)]
+//! struct SomeOptions {
+//!     foo: i32,
+//!     bar: f32,
+//!     baz: Kind,
+//! }
+//!
+//!
+//! fn main() {
+//!     let options: SomeOptions = Default::default();
+//! }
+//! ```
+//!
+//! If you want to override a particular option, but still retain the other defaults:
+//!
+//! ```
+//! # #[allow(dead_code)]
+//! # #[derive(Default)]
+//! # struct SomeOptions {
+//! #     foo: i32,
+//! #     bar: f32,
+//! # }
+//! fn main() {
+//!     let options = SomeOptions { foo: 42, ..Default::default() };
+//! }
+//! ```
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use marker::Sized;
+
+/// A trait for giving a type a useful default value.
+///
+/// A struct can derive default implementations of `Default` for basic types using
+/// `#[derive(Default)]`.
+///
+/// # Examples
+///
+/// ```
+/// # #[allow(dead_code)]
+/// #[derive(Default)]
+/// struct SomeOptions {
+///     foo: i32,
+///     bar: f32,
+/// }
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait Default: Sized {
+    /// Returns the "default value" for a type.
+    ///
+    /// Default values are often some kind of initial value, identity value, or anything else that
+    /// may make sense as a default.
+    ///
+    /// # Examples
+    ///
+    /// Using built-in default values:
+    ///
+    /// ```
+    /// let i: i8 = Default::default();
+    /// let (x, y): (Option<String>, f64) = Default::default();
+    /// let (a, b, (c, d)): (i32, u32, (bool, bool)) = Default::default();
+    /// ```
+    ///
+    /// Making your own:
+    ///
+    /// ```
+    /// # #[allow(dead_code)]
+    /// enum Kind {
+    ///     A,
+    ///     B,
+    ///     C,
+    /// }
+    ///
+    /// impl Default for Kind {
+    ///     fn default() -> Kind { Kind::A }
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn default() -> Self;
+}
+
+macro_rules! default_impl {
+    ($t:ty, $v:expr) => {
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl Default for $t {
+            #[inline]
+            fn default() -> $t { $v }
+        }
+    }
+}
+
+default_impl! { (), () }
+default_impl! { bool, false }
+default_impl! { char, '\x00' }
+
+default_impl! { usize, 0 }
+default_impl! { u8, 0 }
+default_impl! { u16, 0 }
+default_impl! { u32, 0 }
+default_impl! { u64, 0 }
+
+default_impl! { isize, 0 }
+default_impl! { i8, 0 }
+default_impl! { i16, 0 }
+default_impl! { i32, 0 }
+default_impl! { i64, 0 }
+
+default_impl! { f32, 0.0f32 }
+default_impl! { f64, 0.0f64 }