"nightly" feature (for using allocation in no_std environments)

To use Box, String, and Vec in no_std environments, we need to obtain them from
liballoc, which is presently unstable and therefore requires nightly.

So as to avoid any confusion as to the (in)stability of this approach, the
feature is named "nightly".

Travis CI is configured to check that builds succeed with both the "nightly"
feature along with "std" and "nightly" in combination. To avoid the problem
of nightly changes breaking the build, these combinations are specifically
flagged as allowed failures in the Travis CI configuration.

.travis.yml

@@ -40,6 +40,25 @@ matrix:
     - env: EXTRA_ARGS="--no-default-features"
       script: cargo build $EXTRA_ARGS
 
+    # Ensure crate compiles with "nightly" feature (i.e. for allocation w\ no_std)
+    - env: EXTRA_ARGS="--no-default-features --features nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
+    # Ensure crate compiles with both "std" and "nightly" features
+    - env: EXTRA_ARGS="--no-default-features --features std,nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
+  # Allow "nightly" feature to fail (so we aren't blocked on upstream nightly changes)
+  allow_failures:
+    - env: EXTRA_ARGS="--no-default-features --features nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+    - env: EXTRA_ARGS="--no-default-features --features std,nightly"
+      script: cargo build $EXTRA_ARGS
+      rust: nightly
+
 before_install: set -e
 
 install:

Cargo.toml

@@ -33,4 +33,5 @@ serde_test = "1.0"
 
 [features]
 default = ["std"]
+nightly = []
 std = ["iovec"]

src/buf/buf.rs

@@ -1,11 +1,13 @@
 use super::{IntoBuf, Take, Reader, Iter, Chain};
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 use super::FromBuf;
 
 use byteorder::ByteOrder;
 #[cfg(feature = "std")]
 use iovec::IoVec;
 
+#[cfg(feature = "nightly")]
+use alloc::boxed::Box;
 use core::{cmp, ptr};
 
 #[cfg(feature = "std")]
@@ -528,7 +530,7 @@ pub trait Buf {
     ///
     /// assert_eq!(vec, &b"hello world"[..]);
     /// ```
-    #[cfg(feature = "std")]
+    #[cfg(any(feature = "std", feature = "nightly"))]
     fn collect<B>(self) -> B
         where Self: Sized,
               B: FromBuf,
@@ -681,7 +683,7 @@ impl<'a, T: Buf + ?Sized> Buf for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 impl<T: Buf + ?Sized> Buf for Box<T> {
     fn remaining(&self) -> usize {
         (**self).remaining()

src/buf/buf_mut.rs

@@ -1,8 +1,13 @@
 use super::{IntoBuf, Writer};
 use byteorder::ByteOrder;
+
 #[cfg(feature = "std")]
 use iovec::IoVec;
 
+#[cfg(feature = "nightly")]
+use alloc::boxed::Box;
+#[cfg(feature = "nightly")]
+use alloc::vec::Vec;
 use core::{cmp, ptr, usize};
 
 #[cfg(feature = "std")]
@@ -660,7 +665,7 @@ impl<'a, T: BufMut + ?Sized> BufMut for &'a mut T {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 impl<T: BufMut + ?Sized> BufMut for Box<T> {
     fn remaining_mut(&self) -> usize {
         (**self).remaining_mut()
@@ -709,7 +714,7 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for io::Cursor<T> {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {

src/buf/from_buf.rs

@@ -1,5 +1,8 @@
 use {Buf, BufMut, IntoBuf, Bytes, BytesMut};
 
+#[cfg(feature = "nightly")]
+use alloc::vec::Vec;
+
 /// Conversion from a [`Buf`]
 ///
 /// Implementing `FromBuf` for a type defines how it is created from a buffer.

src/buf/mod.rs

@@ -18,7 +18,7 @@
 
 mod buf;
 mod buf_mut;
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 mod from_buf;
 mod chain;
 mod into_buf;
@@ -29,7 +29,7 @@ mod writer;
 
 pub use self::buf::Buf;
 pub use self::buf_mut::BufMut;
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 pub use self::from_buf::FromBuf;
 pub use self::chain::Chain;
 pub use self::into_buf::IntoBuf;

src/bytes.rs

@@ -1,4 +1,7 @@
-use {IntoBuf, Buf, BufMut};
+#[cfg(feature = "std")]
+use {IntoBuf, Buf};
+use BufMut;
+#[cfg(feature = "std")]
 use buf::Iter;
 use debug;
 
@@ -7,6 +10,13 @@ use core::borrow::Borrow;
 use core::sync::atomic::{self, AtomicUsize, AtomicPtr};
 use core::sync::atomic::Ordering::{Relaxed, Acquire, Release, AcqRel};
 
+#[cfg(feature = "nightly")]
+use alloc::boxed::Box;
+#[cfg(feature = "nightly")]
+use alloc::string::String;
+#[cfg(feature = "nightly")]
+use alloc::vec::Vec;
+
 #[cfg(feature = "std")]
 use std::io;
 
@@ -768,6 +778,7 @@ impl Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for Bytes {
     type Buf = io::Cursor<Self>;
 
@@ -776,6 +787,7 @@ impl IntoBuf for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a Bytes {
     type Buf = io::Cursor<Self>;
 
@@ -886,6 +898,7 @@ impl Borrow<[u8]> for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for Bytes {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<Bytes>>;
@@ -895,6 +908,7 @@ impl IntoIterator for Bytes {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a Bytes {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<&'a Bytes>>;
@@ -1376,6 +1390,7 @@ impl BufMut for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoBuf for BytesMut {
     type Buf = io::Cursor<Self>;
 
@@ -1384,6 +1399,7 @@ impl IntoBuf for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoBuf for &'a BytesMut {
     type Buf = io::Cursor<&'a BytesMut>;
 
@@ -1546,6 +1562,7 @@ impl Clone for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl IntoIterator for BytesMut {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<BytesMut>>;
@@ -1555,6 +1572,7 @@ impl IntoIterator for BytesMut {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a> IntoIterator for &'a BytesMut {
     type Item = u8;
     type IntoIter = Iter<io::Cursor<&'a BytesMut>>;

src/lib.rs

@@ -71,9 +71,12 @@
 #![deny(warnings, missing_docs, missing_debug_implementations)]
 #![doc(html_root_url = "https://docs.rs/bytes/0.4")]
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(feature = "nightly", feature(alloc))]
 
 extern crate byteorder;
 
+#[cfg(feature = "nightly")]
+extern crate alloc;
 #[cfg(feature = "std")]
 extern crate core;
 #[cfg(feature = "std")]
@@ -93,12 +96,12 @@ pub use buf::{
     Take,
 };
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 mod bytes;
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 mod debug;
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "nightly"))]
 pub use bytes::{Bytes, BytesMut};
 
 pub use byteorder::{ByteOrder, BigEndian, LittleEndian};