Auto merge of #42991 - sfackler:unstable-rangeargument, r=alexcrichton

Revert "Stabilize RangeArgument"

This reverts commit 143206d54d7558c2326212df99efc98110904fdb.

From the discussion in #30877 it seems like this is premature.

7 files changed, 200 insertions, 12 deletions

diff --git a/src/liballoc/btree/map.rs b/src/liballoc/btree/map.rs
index 5243fb6ae0e..a51c70159db 100644
--- a/src/liballoc/btree/map.rs
+++ b/src/liballoc/btree/map.rs
@@ -13,11 +13,12 @@ use core::fmt::Debug;
 use core::hash::{Hash, Hasher};
 use core::iter::{FromIterator, Peekable, FusedIterator};
 use core::marker::PhantomData;
-use core::ops::{Index, RangeArgument};
-use core::ops::Bound::{Excluded, Included, Unbounded};
+use core::ops::Index;
 use core::{fmt, intrinsics, mem, ptr};
 
 use borrow::Borrow;
+use Bound::{Excluded, Included, Unbounded};
+use range::RangeArgument;
 
 use super::node::{self, Handle, NodeRef, marker};
 use super::search;
diff --git a/src/liballoc/btree/set.rs b/src/liballoc/btree/set.rs
index c755d2d8b85..d32460da939 100644
--- a/src/liballoc/btree/set.rs
+++ b/src/liballoc/btree/set.rs
@@ -16,11 +16,12 @@ use core::cmp::{min, max};
 use core::fmt::Debug;
 use core::fmt;
 use core::iter::{Peekable, FromIterator, FusedIterator};
-use core::ops::{BitOr, BitAnd, BitXor, Sub, RangeArgument};
+use core::ops::{BitOr, BitAnd, BitXor, Sub};
 
 use borrow::Borrow;
 use btree_map::{BTreeMap, Keys};
 use super::Recover;
+use range::RangeArgument;
 
 // FIXME(conventions): implement bounded iterators
 
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 6f4e300fd3c..ca52943ea97 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -203,7 +203,56 @@ mod std {
     pub use core::ops;      // RangeFull
 }
 
-pub use core::ops::Bound;
+/// An endpoint of a range of keys.
+///
+/// # Examples
+///
+/// `Bound`s are range endpoints:
+///
+/// ```
+/// #![feature(collections_range)]
+///
+/// use std::collections::range::RangeArgument;
+/// use std::collections::Bound::*;
+///
+/// assert_eq!((..100).start(), Unbounded);
+/// assert_eq!((1..12).start(), Included(&1));
+/// assert_eq!((1..12).end(), Excluded(&12));
+/// ```
+///
+/// Using a tuple of `Bound`s as an argument to [`BTreeMap::range`].
+/// Note that in most cases, it's better to use range syntax (`1..5`) instead.
+///
+/// ```
+/// use std::collections::BTreeMap;
+/// use std::collections::Bound::{Excluded, Included, Unbounded};
+///
+/// let mut map = BTreeMap::new();
+/// map.insert(3, "a");
+/// map.insert(5, "b");
+/// map.insert(8, "c");
+///
+/// for (key, value) in map.range((Excluded(3), Included(8))) {
+///     println!("{}: {}", key, value);
+/// }
+///
+/// assert_eq!(Some((&3, &"a")), map.range((Unbounded, Included(5))).next());
+/// ```
+///
+/// [`BTreeMap::range`]: btree_map/struct.BTreeMap.html#method.range
+#[stable(feature = "collections_bound", since = "1.17.0")]
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+pub enum Bound<T> {
+    /// An inclusive bound.
+    #[stable(feature = "collections_bound", since = "1.17.0")]
+    Included(T),
+    /// An exclusive bound.
+    #[stable(feature = "collections_bound", since = "1.17.0")]
+    Excluded(T),
+    /// An infinite endpoint. Indicates that there is no bound in this direction.
+    #[stable(feature = "collections_bound", since = "1.17.0")]
+    Unbounded,
+}
 
 /// An intermediate trait for specialization of `Extend`.
 #[doc(hidden)]
diff --git a/src/liballoc/range.rs b/src/liballoc/range.rs
index 0a058c47a50..f862da0d61e 100644
--- a/src/liballoc/range.rs
+++ b/src/liballoc/range.rs
@@ -11,8 +11,142 @@
 #![unstable(feature = "collections_range",
             reason = "waiting for dust to settle on inclusive ranges",
             issue = "30877")]
-#![rustc_deprecated(reason = "moved to core::ops", since = "1.19.0")]
 
 //! Range syntax.
 
-pub use core::ops::RangeArgument;
+use core::ops::{RangeFull, Range, RangeTo, RangeFrom, RangeInclusive, RangeToInclusive};
+use Bound::{self, Excluded, Included, Unbounded};
+
+/// `RangeArgument` is implemented by Rust's built-in range types, produced
+/// by range syntax like `..`, `a..`, `..b` or `c..d`.
+pub trait RangeArgument<T: ?Sized> {
+    /// Start index bound.
+    ///
+    /// Returns the start value as a `Bound`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(alloc)]
+    /// #![feature(collections_range)]
+    ///
+    /// extern crate alloc;
+    ///
+    /// # fn main() {
+    /// use alloc::range::RangeArgument;
+    /// use alloc::Bound::*;
+    ///
+    /// assert_eq!((..10).start(), Unbounded);
+    /// assert_eq!((3..10).start(), Included(&3));
+    /// # }
+    /// ```
+    fn start(&self) -> Bound<&T>;
+
+    /// End index bound.
+    ///
+    /// Returns the end value as a `Bound`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(alloc)]
+    /// #![feature(collections_range)]
+    ///
+    /// extern crate alloc;
+    ///
+    /// # fn main() {
+    /// use alloc::range::RangeArgument;
+    /// use alloc::Bound::*;
+    ///
+    /// assert_eq!((3..).end(), Unbounded);
+    /// assert_eq!((3..10).end(), Excluded(&10));
+    /// # }
+    /// ```
+    fn end(&self) -> Bound<&T>;
+}
+
+// FIXME add inclusive ranges to RangeArgument
+
+impl<T: ?Sized> RangeArgument<T> for RangeFull {
+    fn start(&self) -> Bound<&T> {
+        Unbounded
+    }
+    fn end(&self) -> Bound<&T> {
+        Unbounded
+    }
+}
+
+impl<T> RangeArgument<T> for RangeFrom<T> {
+    fn start(&self) -> Bound<&T> {
+        Included(&self.start)
+    }
+    fn end(&self) -> Bound<&T> {
+        Unbounded
+    }
+}
+
+impl<T> RangeArgument<T> for RangeTo<T> {
+    fn start(&self) -> Bound<&T> {
+        Unbounded
+    }
+    fn end(&self) -> Bound<&T> {
+        Excluded(&self.end)
+    }
+}
+
+impl<T> RangeArgument<T> for Range<T> {
+    fn start(&self) -> Bound<&T> {
+        Included(&self.start)
+    }
+    fn end(&self) -> Bound<&T> {
+        Excluded(&self.end)
+    }
+}
+
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl<T> RangeArgument<T> for RangeInclusive<T> {
+    fn start(&self) -> Bound<&T> {
+        Included(&self.start)
+    }
+    fn end(&self) -> Bound<&T> {
+        Included(&self.end)
+    }
+}
+
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl<T> RangeArgument<T> for RangeToInclusive<T> {
+    fn start(&self) -> Bound<&T> {
+        Unbounded
+    }
+    fn end(&self) -> Bound<&T> {
+        Included(&self.end)
+    }
+}
+
+impl<T> RangeArgument<T> for (Bound<T>, Bound<T>) {
+    fn start(&self) -> Bound<&T> {
+        match *self {
+            (Included(ref start), _) => Included(start),
+            (Excluded(ref start), _) => Excluded(start),
+            (Unbounded, _)           => Unbounded,
+        }
+    }
+
+    fn end(&self) -> Bound<&T> {
+        match *self {
+            (_, Included(ref end)) => Included(end),
+            (_, Excluded(ref end)) => Excluded(end),
+            (_, Unbounded)         => Unbounded,
+        }
+    }
+}
+
+impl<'a, T: ?Sized + 'a> RangeArgument<T> for (Bound<&'a T>, Bound<&'a T>) {
+    fn start(&self) -> Bound<&T> {
+        self.0
+    }
+
+    fn end(&self) -> Bound<&T> {
+        self.1
+    }
+}
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 1f0894d39d4..79d1ccf637d 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -59,14 +59,15 @@
 use core::fmt;
 use core::hash;
 use core::iter::{FromIterator, FusedIterator};
-use core::ops::{self, Add, AddAssign, Index, IndexMut, RangeArgument};
-use core::ops::Bound::{Excluded, Included, Unbounded};
+use core::ops::{self, Add, AddAssign, Index, IndexMut};
 use core::ptr;
 use core::str::pattern::Pattern;
 use std_unicode::lossy;
 use std_unicode::char::{decode_utf16, REPLACEMENT_CHARACTER};
 
 use borrow::{Cow, ToOwned};
+use range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 use str::{self, from_boxed_utf8_unchecked, FromStr, Utf8Error, Chars};
 use vec::Vec;
 use boxed::Box;
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index e118d406ecf..5d1999a4262 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -74,8 +74,7 @@ use core::iter::{FromIterator, FusedIterator, TrustedLen};
 use core::mem;
 #[cfg(not(test))]
 use core::num::Float;
-use core::ops::{InPlace, Index, IndexMut, Place, Placer, RangeArgument};
-use core::ops::Bound::{Excluded, Included, Unbounded};
+use core::ops::{InPlace, Index, IndexMut, Place, Placer};
 use core::ops;
 use core::ptr;
 use core::ptr::Shared;
@@ -85,6 +84,8 @@ use borrow::ToOwned;
 use borrow::Cow;
 use boxed::Box;
 use raw_vec::RawVec;
+use super::range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 
 /// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
 ///
diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs
index d1d334267bc..18175a5d01b 100644
--- a/src/liballoc/vec_deque.rs
+++ b/src/liballoc/vec_deque.rs
@@ -21,8 +21,7 @@ use core::cmp::Ordering;
 use core::fmt;
 use core::iter::{repeat, FromIterator, FusedIterator};
 use core::mem;
-use core::ops::{Index, IndexMut, Place, Placer, InPlace, RangeArgument};
-use core::ops::Bound::{Excluded, Included, Unbounded};
+use core::ops::{Index, IndexMut, Place, Placer, InPlace};
 use core::ptr;
 use core::ptr::Shared;
 use core::slice;
@@ -32,6 +31,8 @@ use core::cmp;
 
 use raw_vec::RawVec;
 
+use super::range::RangeArgument;
+use Bound::{Excluded, Included, Unbounded};
 use super::vec::Vec;
 
 const INITIAL_CAPACITY: usize = 7; // 2^3 - 1