Merge crate `collections` into `alloc`

1 files changed, 2287 insertions, 0 deletions

diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
new file mode 100644
index 00000000000..1d98626e90b
--- /dev/null
+++ b/src/liballoc/string.rs
@@ -0,0 +1,2287 @@
+// Copyright 2014 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.
+
+//! A UTF-8 encoded, growable string.
+//!
+//! This module contains the [`String`] type, a trait for converting
+//! [`ToString`]s, and several error types that may result from working with
+//! [`String`]s.
+//!
+//! [`ToString`]: trait.ToString.html
+//!
+//! # Examples
+//!
+//! There are multiple ways to create a new [`String`] from a string literal:
+//!
+//! ```
+//! let s = "Hello".to_string();
+//!
+//! let s = String::from("world");
+//! let s: String = "also this".into();
+//! ```
+//!
+//! You can create a new [`String`] from an existing one by concatenating with
+//! `+`:
+//!
+//! [`String`]: struct.String.html
+//!
+//! ```
+//! let s = "Hello".to_string();
+//!
+//! let message = s + " world!";
+//! ```
+//!
+//! If you have a vector of valid UTF-8 bytes, you can make a `String` out of
+//! it. You can do the reverse too.
+//!
+//! ```
+//! let sparkle_heart = vec![240, 159, 146, 150];
+//!
+//! // We know these bytes are valid, so we'll use `unwrap()`.
+//! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+//!
+//! assert_eq!("💖", sparkle_heart);
+//!
+//! let bytes = sparkle_heart.into_bytes();
+//!
+//! assert_eq!(bytes, [240, 159, 146, 150]);
+//! ```
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::fmt;
+use core::hash;
+use core::iter::{FromIterator, FusedIterator};
+use core::ops::{self, Add, AddAssign, Index, IndexMut};
+use core::ptr;
+use core::str as core_str;
+use core::str::pattern::Pattern;
+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;
+
+/// A UTF-8 encoded, growable string.
+///
+/// The `String` type is the most common string type that has ownership over the
+/// contents of the string. It has a close relationship with its borrowed
+/// counterpart, the primitive [`str`].
+///
+/// [`str`]: ../../std/primitive.str.html
+///
+/// # Examples
+///
+/// You can create a `String` from a literal string with `String::from`:
+///
+/// ```
+/// let hello = String::from("Hello, world!");
+/// ```
+///
+/// You can append a [`char`] to a `String` with the [`push`] method, and
+/// append a [`&str`] with the [`push_str`] method:
+///
+/// ```
+/// let mut hello = String::from("Hello, ");
+///
+/// hello.push('w');
+/// hello.push_str("orld!");
+/// ```
+///
+/// [`char`]: ../../std/primitive.char.html
+/// [`push`]: #method.push
+/// [`push_str`]: #method.push_str
+///
+/// If you have a vector of UTF-8 bytes, you can create a `String` from it with
+/// the [`from_utf8`] method:
+///
+/// ```
+/// // some bytes, in a vector
+/// let sparkle_heart = vec![240, 159, 146, 150];
+///
+/// // We know these bytes are valid, so we'll use `unwrap()`.
+/// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+///
+/// assert_eq!("💖", sparkle_heart);
+/// ```
+///
+/// [`from_utf8`]: #method.from_utf8
+///
+/// # UTF-8
+///
+/// `String`s are always valid UTF-8. This has a few implications, the first of
+/// which is that if you need a non-UTF-8 string, consider [`OsString`]. It is
+/// similar, but without the UTF-8 constraint. The second implication is that
+/// you cannot index into a `String`:
+///
+/// ```ignore
+/// let s = "hello";
+///
+/// println!("The first letter of s is {}", s[0]); // ERROR!!!
+/// ```
+///
+/// [`OsString`]: ../../std/ffi/struct.OsString.html
+///
+/// Indexing is intended to be a constant-time operation, but UTF-8 encoding
+/// does not allow us to do this. Furthermore, it's not clear what sort of
+/// thing the index should return: a byte, a codepoint, or a grapheme cluster.
+/// The [`bytes`] and [`chars`] methods return iterators over the first
+/// two, respectively.
+///
+/// [`bytes`]: #method.bytes
+/// [`chars`]: #method.chars
+///
+/// # Deref
+///
+/// `String`s implement [`Deref`]`<Target=str>`, and so inherit all of [`str`]'s
+/// methods. In addition, this means that you can pass a `String` to any
+/// function which takes a [`&str`] by using an ampersand (`&`):
+///
+/// ```
+/// fn takes_str(s: &str) { }
+///
+/// let s = String::from("Hello");
+///
+/// takes_str(&s);
+/// ```
+///
+/// [`&str`]: ../../std/primitive.str.html
+/// [`Deref`]: ../../std/ops/trait.Deref.html
+///
+/// This will create a [`&str`] from the `String` and pass it in. This
+/// conversion is very inexpensive, and so generally, functions will accept
+/// [`&str`]s as arguments unless they need a `String` for some specific reason.
+///
+///
+/// # Representation
+///
+/// A `String` is made up of three components: a pointer to some bytes, a
+/// length, and a capacity. The pointer points to an internal buffer `String`
+/// uses to store its data. The length is the number of bytes currently stored
+/// in the buffer, and the capacity is the size of the buffer in bytes. As such,
+/// the length will always be less than or equal to the capacity.
+///
+/// This buffer is always stored on the heap.
+///
+/// You can look at these with the [`as_ptr`], [`len`], and [`capacity`]
+/// methods:
+///
+/// ```
+/// use std::mem;
+///
+/// let story = String::from("Once upon a time...");
+///
+/// let ptr = story.as_ptr();
+/// let len = story.len();
+/// let capacity = story.capacity();
+///
+/// // story has nineteen bytes
+/// assert_eq!(19, len);
+///
+/// // Now that we have our parts, we throw the story away.
+/// mem::forget(story);
+///
+/// // We can re-build a String out of ptr, len, and capacity. This is all
+/// // unsafe because we are responsible for making sure the components are
+/// // valid:
+/// let s = unsafe { String::from_raw_parts(ptr as *mut _, len, capacity) } ;
+///
+/// assert_eq!(String::from("Once upon a time..."), s);
+/// ```
+///
+/// [`as_ptr`]: #method.as_ptr
+/// [`len`]: #method.len
+/// [`capacity`]: #method.capacity
+///
+/// If a `String` has enough capacity, adding elements to it will not
+/// re-allocate. For example, consider this program:
+///
+/// ```
+/// let mut s = String::new();
+///
+/// println!("{}", s.capacity());
+///
+/// for _ in 0..5 {
+///     s.push_str("hello");
+///     println!("{}", s.capacity());
+/// }
+/// ```
+///
+/// This will output the following:
+///
+/// ```text
+/// 0
+/// 5
+/// 10
+/// 20
+/// 20
+/// 40
+/// ```
+///
+/// At first, we have no memory allocated at all, but as we append to the
+/// string, it increases its capacity appropriately. If we instead use the
+/// [`with_capacity`] method to allocate the correct capacity initially:
+///
+/// ```
+/// let mut s = String::with_capacity(25);
+///
+/// println!("{}", s.capacity());
+///
+/// for _ in 0..5 {
+///     s.push_str("hello");
+///     println!("{}", s.capacity());
+/// }
+/// ```
+///
+/// [`with_capacity`]: #method.with_capacity
+///
+/// We end up with a different output:
+///
+/// ```text
+/// 25
+/// 25
+/// 25
+/// 25
+/// 25
+/// 25
+/// ```
+///
+/// Here, there's no need to allocate more memory inside the loop.
+#[derive(PartialOrd, Eq, Ord)]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct String {
+    vec: Vec<u8>,
+}
+
+/// A possible error value when converting a `String` from a UTF-8 byte vector.
+///
+/// This type is the error type for the [`from_utf8`] method on [`String`]. It
+/// is designed in such a way to carefully avoid reallocations: the
+/// [`into_bytes`] method will give back the byte vector that was used in the
+/// conversion attempt.
+///
+/// [`from_utf8`]: struct.String.html#method.from_utf8
+/// [`String`]: struct.String.html
+/// [`into_bytes`]: struct.FromUtf8Error.html#method.into_bytes
+///
+/// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
+/// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
+/// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error`
+/// through the [`utf8_error`] method.
+///
+/// [`Utf8Error`]: ../../std/str/struct.Utf8Error.html
+/// [`std::str`]: ../../std/str/index.html
+/// [`u8`]: ../../std/primitive.u8.html
+/// [`&str`]: ../../std/primitive.str.html
+/// [`utf8_error`]: #method.utf8_error
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // some invalid bytes, in a vector
+/// let bytes = vec![0, 159];
+///
+/// let value = String::from_utf8(bytes);
+///
+/// assert!(value.is_err());
+/// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Debug)]
+pub struct FromUtf8Error {
+    bytes: Vec<u8>,
+    error: Utf8Error,
+}
+
+/// A possible error value when converting a `String` from a UTF-16 byte slice.
+///
+/// This type is the error type for the [`from_utf16`] method on [`String`].
+///
+/// [`from_utf16`]: struct.String.html#method.from_utf16
+/// [`String`]: struct.String.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// // 𝄞mu<invalid>ic
+/// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+///           0xD800, 0x0069, 0x0063];
+///
+/// assert!(String::from_utf16(v).is_err());
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Debug)]
+pub struct FromUtf16Error(());
+
+impl String {
+    /// Creates a new empty `String`.
+    ///
+    /// Given that the `String` is empty, this will not allocate any initial
+    /// buffer. While that means that this initial operation is very
+    /// inexpensive, but may cause excessive allocation later, when you add
+    /// data. If you have an idea of how much data the `String` will hold,
+    /// consider the [`with_capacity`] method to prevent excessive
+    /// re-allocation.
+    ///
+    /// [`with_capacity`]: #method.with_capacity
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = String::new();
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn new() -> String {
+        String { vec: Vec::new() }
+    }
+
+    /// Creates a new empty `String` with a particular capacity.
+    ///
+    /// `String`s have an internal buffer to hold their data. The capacity is
+    /// the length of that buffer, and can be queried with the [`capacity`]
+    /// method. This method creates an empty `String`, but one with an initial
+    /// buffer that can hold `capacity` bytes. This is useful when you may be
+    /// appending a bunch of data to the `String`, reducing the number of
+    /// reallocations it needs to do.
+    ///
+    /// [`capacity`]: #method.capacity
+    ///
+    /// If the given capacity is `0`, no allocation will occur, and this method
+    /// is identical to the [`new`] method.
+    ///
+    /// [`new`]: #method.new
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::with_capacity(10);
+    ///
+    /// // The String contains no chars, even though it has capacity for more
+    /// assert_eq!(s.len(), 0);
+    ///
+    /// // These are all done without reallocating...
+    /// let cap = s.capacity();
+    /// for i in 0..10 {
+    ///     s.push('a');
+    /// }
+    ///
+    /// assert_eq!(s.capacity(), cap);
+    ///
+    /// // ...but this may make the vector reallocate
+    /// s.push('a');
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn with_capacity(capacity: usize) -> String {
+        String { vec: Vec::with_capacity(capacity) }
+    }
+
+    // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
+    // required for this method definition, is not available. Since we don't
+    // require this method for testing purposes, I'll just stub it
+    // NB see the slice::hack module in slice.rs for more information
+    #[inline]
+    #[cfg(test)]
+    pub fn from_str(_: &str) -> String {
+        panic!("not available with cfg(test)");
+    }
+
+    /// Converts a vector of bytes to a `String`.
+    ///
+    /// A string slice ([`&str`]) is made of bytes ([`u8`]), and a vector of bytes
+    /// ([`Vec<u8>`]) is made of bytes, so this function converts between the
+    /// two. Not all byte slices are valid `String`s, however: `String`
+    /// requires that it is valid UTF-8. `from_utf8()` checks to ensure that
+    /// the bytes are valid UTF-8, and then does the conversion.
+    ///
+    /// [`&str`]: ../../std/primitive.str.html
+    /// [`u8`]: ../../std/primitive.u8.html
+    /// [`Vec<u8>`]: ../../std/vec/struct.Vec.html
+    ///
+    /// If you are sure that the byte slice is valid UTF-8, and you don't want
+    /// to incur the overhead of the validity check, there is an unsafe version
+    /// of this function, [`from_utf8_unchecked`], which has the same behavior
+    /// but skips the check.
+    ///
+    /// [`from_utf8_unchecked`]: struct.String.html#method.from_utf8_unchecked
+    ///
+    /// This method will take care to not copy the vector, for efficiency's
+    /// sake.
+    ///
+    /// If you need a `&str` instead of a `String`, consider
+    /// [`str::from_utf8`].
+    ///
+    /// [`str::from_utf8`]: ../../std/str/fn.from_utf8.html
+    ///
+    /// The inverse of this method is [`as_bytes`].
+    ///
+    /// [`as_bytes`]: #method.as_bytes
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the slice is not UTF-8 with a description as to why the
+    /// provided bytes are not UTF-8. The vector you moved in is also included.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // some bytes, in a vector
+    /// let sparkle_heart = vec![240, 159, 146, 150];
+    ///
+    /// // We know these bytes are valid, so we'll use `unwrap()`.
+    /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
+    ///
+    /// assert_eq!("💖", sparkle_heart);
+    /// ```
+    ///
+    /// Incorrect bytes:
+    ///
+    /// ```
+    /// // some invalid bytes, in a vector
+    /// let sparkle_heart = vec![0, 159, 146, 150];
+    ///
+    /// assert!(String::from_utf8(sparkle_heart).is_err());
+    /// ```
+    ///
+    /// See the docs for [`FromUtf8Error`] for more details on what you can do
+    /// with this error.
+    ///
+    /// [`FromUtf8Error`]: struct.FromUtf8Error.html
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> {
+        match str::from_utf8(&vec) {
+            Ok(..) => Ok(String { vec: vec }),
+            Err(e) => {
+                Err(FromUtf8Error {
+                    bytes: vec,
+                    error: e,
+                })
+            }
+        }
+    }
+
+    /// Converts a slice of bytes to a string, including invalid characters.
+    ///
+    /// Strings are made of bytes ([`u8`]), and a slice of bytes
+    /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts
+    /// between the two. Not all byte slices are valid strings, however: strings
+    /// are required to be valid UTF-8. During this conversion,
+    /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with
+    /// `U+FFFD REPLACEMENT CHARACTER`, which looks like this: �
+    ///
+    /// [`u8`]: ../../std/primitive.u8.html
+    /// [byteslice]: ../../std/primitive.slice.html
+    ///
+    /// If you are sure that the byte slice is valid UTF-8, and you don't want
+    /// to incur the overhead of the conversion, there is an unsafe version
+    /// of this function, [`from_utf8_unchecked`], which has the same behavior
+    /// but skips the checks.
+    ///
+    /// [`from_utf8_unchecked`]: struct.String.html#method.from_utf8_unchecked
+    ///
+    /// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid
+    /// UTF-8, then we need to insert the replacement characters, which will
+    /// change the size of the string, and hence, require a `String`. But if
+    /// it's already valid UTF-8, we don't need a new allocation. This return
+    /// type allows us to handle both cases.
+    ///
+    /// [`Cow<'a, str>`]: ../../std/borrow/enum.Cow.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // some bytes, in a vector
+    /// let sparkle_heart = vec![240, 159, 146, 150];
+    ///
+    /// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);
+    ///
+    /// assert_eq!("💖", sparkle_heart);
+    /// ```
+    ///
+    /// Incorrect bytes:
+    ///
+    /// ```
+    /// // some invalid bytes
+    /// let input = b"Hello \xF0\x90\x80World";
+    /// let output = String::from_utf8_lossy(input);
+    ///
+    /// assert_eq!("Hello �World", output);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn from_utf8_lossy<'a>(v: &'a [u8]) -> Cow<'a, str> {
+        let mut i;
+        match str::from_utf8(v) {
+            Ok(s) => return Cow::Borrowed(s),
+            Err(e) => i = e.valid_up_to(),
+        }
+
+        const TAG_CONT_U8: u8 = 128;
+        const REPLACEMENT: &'static [u8] = b"\xEF\xBF\xBD"; // U+FFFD in UTF-8
+        let total = v.len();
+        fn unsafe_get(xs: &[u8], i: usize) -> u8 {
+            unsafe { *xs.get_unchecked(i) }
+        }
+        fn safe_get(xs: &[u8], i: usize, total: usize) -> u8 {
+            if i >= total { 0 } else { unsafe_get(xs, i) }
+        }
+
+        let mut res = String::with_capacity(total);
+
+        if i > 0 {
+            unsafe { res.as_mut_vec().extend_from_slice(&v[..i]) };
+        }
+
+        // subseqidx is the index of the first byte of the subsequence we're
+        // looking at.  It's used to copy a bunch of contiguous good codepoints
+        // at once instead of copying them one by one.
+        let mut subseqidx = i;
+
+        while i < total {
+            let i_ = i;
+            let byte = unsafe_get(v, i);
+            i += 1;
+
+            macro_rules! error { () => ({
+                unsafe {
+                    if subseqidx != i_ {
+                        res.as_mut_vec().extend_from_slice(&v[subseqidx..i_]);
+                    }
+                    subseqidx = i;
+                    res.as_mut_vec().extend_from_slice(REPLACEMENT);
+                }
+            })}
+
+            if byte < 128 {
+                // subseqidx handles this
+            } else {
+                let w = core_str::utf8_char_width(byte);
+
+                match w {
+                    2 => {
+                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
+                            error!();
+                            continue;
+                        }
+                        i += 1;
+                    }
+                    3 => {
+                        match (byte, safe_get(v, i, total)) {
+                            (0xE0, 0xA0...0xBF) => (),
+                            (0xE1...0xEC, 0x80...0xBF) => (),
+                            (0xED, 0x80...0x9F) => (),
+                            (0xEE...0xEF, 0x80...0xBF) => (),
+                            _ => {
+                                error!();
+                                continue;
+                            }
+                        }
+                        i += 1;
+                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
+                            error!();
+                            continue;
+                        }
+                        i += 1;
+                    }
+                    4 => {
+                        match (byte, safe_get(v, i, total)) {
+                            (0xF0, 0x90...0xBF) => (),
+                            (0xF1...0xF3, 0x80...0xBF) => (),
+                            (0xF4, 0x80...0x8F) => (),
+                            _ => {
+                                error!();
+                                continue;
+                            }
+                        }
+                        i += 1;
+                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
+                            error!();
+                            continue;
+                        }
+                        i += 1;
+                        if safe_get(v, i, total) & 192 != TAG_CONT_U8 {
+                            error!();
+                            continue;
+                        }
+                        i += 1;
+                    }
+                    _ => {
+                        error!();
+                        continue;
+                    }
+                }
+            }
+        }
+        if subseqidx < total {
+            unsafe { res.as_mut_vec().extend_from_slice(&v[subseqidx..total]) };
+        }
+        Cow::Owned(res)
+    }
+
+    /// Decode a UTF-16 encoded vector `v` into a `String`, returning `Err`
+    /// if `v` contains any invalid data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // 𝄞music
+    /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+    ///           0x0073, 0x0069, 0x0063];
+    /// assert_eq!(String::from("𝄞music"),
+    ///            String::from_utf16(v).unwrap());
+    ///
+    /// // 𝄞mu<invalid>ic
+    /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+    ///           0xD800, 0x0069, 0x0063];
+    /// assert!(String::from_utf16(v).is_err());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> {
+        decode_utf16(v.iter().cloned()).collect::<Result<_, _>>().map_err(|_| FromUtf16Error(()))
+    }
+
+    /// Decode a UTF-16 encoded vector `v` into a string, replacing
+    /// invalid data with the replacement character (U+FFFD).
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // 𝄞mus<invalid>ic<invalid>
+    /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
+    ///           0x0073, 0xDD1E, 0x0069, 0x0063,
+    ///           0xD834];
+    ///
+    /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
+    ///            String::from_utf16_lossy(v));
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn from_utf16_lossy(v: &[u16]) -> String {
+        decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect()
+    }
+
+    /// Creates a new `String` from a length, capacity, and pointer.
+    ///
+    /// # Safety
+    ///
+    /// This is highly unsafe, due to the number of invariants that aren't
+    /// checked:
+    ///
+    /// * The memory at `ptr` needs to have been previously allocated by the
+    ///   same allocator the standard library uses.
+    /// * `length` needs to be less than or equal to `capacity`.
+    /// * `capacity` needs to be the correct value.
+    ///
+    /// Violating these may cause problems like corrupting the allocator's
+    /// internal datastructures.
+    ///
+    /// The ownership of `ptr` is effectively transferred to the
+    /// `String` which may then deallocate, reallocate or change the
+    /// contents of memory pointed to by the pointer at will. Ensure
+    /// that nothing else uses the pointer after calling this
+    /// function.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// use std::mem;
+    ///
+    /// unsafe {
+    ///     let s = String::from("hello");
+    ///     let ptr = s.as_ptr();
+    ///     let len = s.len();
+    ///     let capacity = s.capacity();
+    ///
+    ///     mem::forget(s);
+    ///
+    ///     let s = String::from_raw_parts(ptr as *mut _, len, capacity);
+    ///
+    ///     assert_eq!(String::from("hello"), s);
+    /// }
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String {
+        String { vec: Vec::from_raw_parts(buf, length, capacity) }
+    }
+
+    /// Converts a vector of bytes to a `String` without checking that the
+    /// string contains valid UTF-8.
+    ///
+    /// See the safe version, [`from_utf8`], for more details.
+    ///
+    /// [`from_utf8`]: struct.String.html#method.from_utf8
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe because it does not check that the bytes passed
+    /// to it are valid UTF-8. If this constraint is violated, it may cause
+    /// memory unsafety issues with future users of the `String`, as the rest of
+    /// the standard library assumes that `String`s are valid UTF-8.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // some bytes, in a vector
+    /// let sparkle_heart = vec![240, 159, 146, 150];
+    ///
+    /// let sparkle_heart = unsafe {
+    ///     String::from_utf8_unchecked(sparkle_heart)
+    /// };
+    ///
+    /// assert_eq!("💖", sparkle_heart);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String {
+        String { vec: bytes }
+    }
+
+    /// Converts a `String` into a byte vector.
+    ///
+    /// This consumes the `String`, so we do not need to copy its contents.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = String::from("hello");
+    /// let bytes = s.into_bytes();
+    ///
+    /// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn into_bytes(self) -> Vec<u8> {
+        self.vec
+    }
+
+    /// Extracts a string slice containing the entire string.
+    #[inline]
+    #[stable(feature = "string_as_str", since = "1.7.0")]
+    pub fn as_str(&self) -> &str {
+        self
+    }
+
+    /// Extracts a string slice containing the entire string.
+    #[inline]
+    #[stable(feature = "string_as_str", since = "1.7.0")]
+    pub fn as_mut_str(&mut self) -> &mut str {
+        self
+    }
+
+    /// Appends a given string slice onto the end of this `String`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("foo");
+    ///
+    /// s.push_str("bar");
+    ///
+    /// assert_eq!("foobar", s);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn push_str(&mut self, string: &str) {
+        self.vec.extend_from_slice(string.as_bytes())
+    }
+
+    /// Returns this `String`'s capacity, in bytes.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = String::with_capacity(10);
+    ///
+    /// assert!(s.capacity() >= 10);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn capacity(&self) -> usize {
+        self.vec.capacity()
+    }
+
+    /// Ensures that this `String`'s capacity is at least `additional` bytes
+    /// larger than its length.
+    ///
+    /// The capacity may be increased by more than `additional` bytes if it
+    /// chooses, to prevent frequent reallocations.
+    ///
+    /// If you do not want this "at least" behavior, see the [`reserve_exact`]
+    /// method.
+    ///
+    /// [`reserve_exact`]: #method.reserve_exact
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity overflows `usize`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::new();
+    ///
+    /// s.reserve(10);
+    ///
+    /// assert!(s.capacity() >= 10);
+    /// ```
+    ///
+    /// This may not actually increase the capacity:
+    ///
+    /// ```
+    /// let mut s = String::with_capacity(10);
+    /// s.push('a');
+    /// s.push('b');
+    ///
+    /// // s now has a length of 2 and a capacity of 10
+    /// assert_eq!(2, s.len());
+    /// assert_eq!(10, s.capacity());
+    ///
+    /// // Since we already have an extra 8 capacity, calling this...
+    /// s.reserve(8);
+    ///
+    /// // ... doesn't actually increase.
+    /// assert_eq!(10, s.capacity());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn reserve(&mut self, additional: usize) {
+        self.vec.reserve(additional)
+    }
+
+    /// Ensures that this `String`'s capacity is `additional` bytes
+    /// larger than its length.
+    ///
+    /// Consider using the [`reserve`] method unless you absolutely know
+    /// better than the allocator.
+    ///
+    /// [`reserve`]: #method.reserve
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity overflows `usize`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::new();
+    ///
+    /// s.reserve_exact(10);
+    ///
+    /// assert!(s.capacity() >= 10);
+    /// ```
+    ///
+    /// This may not actually increase the capacity:
+    ///
+    /// ```
+    /// let mut s = String::with_capacity(10);
+    /// s.push('a');
+    /// s.push('b');
+    ///
+    /// // s now has a length of 2 and a capacity of 10
+    /// assert_eq!(2, s.len());
+    /// assert_eq!(10, s.capacity());
+    ///
+    /// // Since we already have an extra 8 capacity, calling this...
+    /// s.reserve_exact(8);
+    ///
+    /// // ... doesn't actually increase.
+    /// assert_eq!(10, s.capacity());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn reserve_exact(&mut self, additional: usize) {
+        self.vec.reserve_exact(additional)
+    }
+
+    /// Shrinks the capacity of this `String` to match its length.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("foo");
+    ///
+    /// s.reserve(100);
+    /// assert!(s.capacity() >= 100);
+    ///
+    /// s.shrink_to_fit();
+    /// assert_eq!(3, s.capacity());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn shrink_to_fit(&mut self) {
+        self.vec.shrink_to_fit()
+    }
+
+    /// Appends the given `char` to the end of this `String`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("abc");
+    ///
+    /// s.push('1');
+    /// s.push('2');
+    /// s.push('3');
+    ///
+    /// assert_eq!("abc123", s);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn push(&mut self, ch: char) {
+        match ch.len_utf8() {
+            1 => self.vec.push(ch as u8),
+            _ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()),
+        }
+    }
+
+    /// Returns a byte slice of this `String`'s contents.
+    ///
+    /// The inverse of this method is [`from_utf8`].
+    ///
+    /// [`from_utf8`]: #method.from_utf8
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = String::from("hello");
+    ///
+    /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn as_bytes(&self) -> &[u8] {
+        &self.vec
+    }
+
+    /// Shortens this `String` to the specified length.
+    ///
+    /// If `new_len` is greater than the string's current length, this has no
+    /// effect.
+    ///
+    /// Note that this method has no effect on the allocated capacity
+    /// of the string
+    ///
+    /// # Panics
+    ///
+    /// Panics if `new_len` does not lie on a [`char`] boundary.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("hello");
+    ///
+    /// s.truncate(2);
+    ///
+    /// assert_eq!("he", s);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn truncate(&mut self, new_len: usize) {
+        if new_len <= self.len() {
+            assert!(self.is_char_boundary(new_len));
+            self.vec.truncate(new_len)
+        }
+    }
+
+    /// Removes the last character from the string buffer and returns it.
+    ///
+    /// Returns `None` if this `String` is empty.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("foo");
+    ///
+    /// assert_eq!(s.pop(), Some('o'));
+    /// assert_eq!(s.pop(), Some('o'));
+    /// assert_eq!(s.pop(), Some('f'));
+    ///
+    /// assert_eq!(s.pop(), None);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn pop(&mut self) -> Option<char> {
+        let ch = match self.chars().rev().next() {
+            Some(ch) => ch,
+            None => return None,
+        };
+        let newlen = self.len() - ch.len_utf8();
+        unsafe {
+            self.vec.set_len(newlen);
+        }
+        Some(ch)
+    }
+
+    /// Removes a `char` from this `String` at a byte position and returns it.
+    ///
+    /// This is an `O(n)` operation, as it requires copying every element in the
+    /// buffer.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `idx` is larger than or equal to the `String`'s length,
+    /// or if it does not lie on a [`char`] boundary.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("foo");
+    ///
+    /// assert_eq!(s.remove(0), 'f');
+    /// assert_eq!(s.remove(1), 'o');
+    /// assert_eq!(s.remove(0), 'o');
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn remove(&mut self, idx: usize) -> char {
+        let ch = match self[idx..].chars().next() {
+            Some(ch) => ch,
+            None => panic!("cannot remove a char from the end of a string"),
+        };
+
+        let next = idx + ch.len_utf8();
+        let len = self.len();
+        unsafe {
+            ptr::copy(self.vec.as_ptr().offset(next as isize),
+                      self.vec.as_mut_ptr().offset(idx as isize),
+                      len - next);
+            self.vec.set_len(len - (next - idx));
+        }
+        ch
+    }
+
+    /// Inserts a character into this `String` at a byte position.
+    ///
+    /// This is an `O(n)` operation as it requires copying every element in the
+    /// buffer.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `idx` is larger than the `String`'s length, or if it does not
+    /// lie on a [`char`] boundary.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::with_capacity(3);
+    ///
+    /// s.insert(0, 'f');
+    /// s.insert(1, 'o');
+    /// s.insert(2, 'o');
+    ///
+    /// assert_eq!("foo", s);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn insert(&mut self, idx: usize, ch: char) {
+        assert!(self.is_char_boundary(idx));
+        let mut bits = [0; 4];
+        let bits = ch.encode_utf8(&mut bits).as_bytes();
+
+        unsafe {
+            self.insert_bytes(idx, bits);
+        }
+    }
+
+    unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) {
+        let len = self.len();
+        let amt = bytes.len();
+        self.vec.reserve(amt);
+
+        ptr::copy(self.vec.as_ptr().offset(idx as isize),
+                  self.vec.as_mut_ptr().offset((idx + amt) as isize),
+                  len - idx);
+        ptr::copy(bytes.as_ptr(),
+                  self.vec.as_mut_ptr().offset(idx as isize),
+                  amt);
+        self.vec.set_len(len + amt);
+    }
+
+    /// Inserts a string slice into this `String` at a byte position.
+    ///
+    /// This is an `O(n)` operation as it requires copying every element in the
+    /// buffer.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `idx` is larger than the `String`'s length, or if it does not
+    /// lie on a [`char`] boundary.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("bar");
+    ///
+    /// s.insert_str(0, "foo");
+    ///
+    /// assert_eq!("foobar", s);
+    /// ```
+    #[inline]
+    #[stable(feature = "insert_str", since = "1.16.0")]
+    pub fn insert_str(&mut self, idx: usize, string: &str) {
+        assert!(self.is_char_boundary(idx));
+
+        unsafe {
+            self.insert_bytes(idx, string.as_bytes());
+        }
+    }
+
+    /// Returns a mutable reference to the contents of this `String`.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe because it does not check that the bytes passed
+    /// to it are valid UTF-8. If this constraint is violated, it may cause
+    /// memory unsafety issues with future users of the `String`, as the rest of
+    /// the standard library assumes that `String`s are valid UTF-8.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("hello");
+    ///
+    /// unsafe {
+    ///     let vec = s.as_mut_vec();
+    ///     assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);
+    ///
+    ///     vec.reverse();
+    /// }
+    /// assert_eq!(s, "olleh");
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> {
+        &mut self.vec
+    }
+
+    /// Returns the length of this `String`, in bytes.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let a = String::from("foo");
+    ///
+    /// assert_eq!(a.len(), 3);
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn len(&self) -> usize {
+        self.vec.len()
+    }
+
+    /// Returns `true` if this `String` has a length of zero.
+    ///
+    /// Returns `false` otherwise.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut v = String::new();
+    /// assert!(v.is_empty());
+    ///
+    /// v.push('a');
+    /// assert!(!v.is_empty());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Splits the string into two at the given index.
+    ///
+    /// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and
+    /// the returned `String` contains bytes `[at, len)`. `at` must be on the
+    /// boundary of a UTF-8 code point.
+    ///
+    /// Note that the capacity of `self` does not change.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last
+    /// code point of the string.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # fn main() {
+    /// let mut hello = String::from("Hello, World!");
+    /// let world = hello.split_off(7);
+    /// assert_eq!(hello, "Hello, ");
+    /// assert_eq!(world, "World!");
+    /// # }
+    /// ```
+    #[inline]
+    #[stable(feature = "string_split_off", since = "1.16.0")]
+    pub fn split_off(&mut self, at: usize) -> String {
+        assert!(self.is_char_boundary(at));
+        let other = self.vec.split_off(at);
+        unsafe { String::from_utf8_unchecked(other) }
+    }
+
+    /// Truncates this `String`, removing all contents.
+    ///
+    /// While this means the `String` will have a length of zero, it does not
+    /// touch its capacity.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("foo");
+    ///
+    /// s.clear();
+    ///
+    /// assert!(s.is_empty());
+    /// assert_eq!(0, s.len());
+    /// assert_eq!(3, s.capacity());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn clear(&mut self) {
+        self.vec.clear()
+    }
+
+    /// Creates a draining iterator that removes the specified range in the string
+    /// and yields the removed chars.
+    ///
+    /// Note: The element range is removed even if the iterator is not
+    /// consumed until the end.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the starting point or end point do not lie on a [`char`]
+    /// boundary, or if they're out of bounds.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = String::from("α is alpha, β is beta");
+    /// let beta_offset = s.find('β').unwrap_or(s.len());
+    ///
+    /// // Remove the range up until the β from the string
+    /// let t: String = s.drain(..beta_offset).collect();
+    /// assert_eq!(t, "α is alpha, ");
+    /// assert_eq!(s, "β is beta");
+    ///
+    /// // A full range clears the string
+    /// s.drain(..);
+    /// assert_eq!(s, "");
+    /// ```
+    #[stable(feature = "drain", since = "1.6.0")]
+    pub fn drain<R>(&mut self, range: R) -> Drain
+        where R: RangeArgument<usize>
+    {
+        // Memory safety
+        //
+        // The String version of Drain does not have the memory safety issues
+        // of the vector version. The data is just plain bytes.
+        // Because the range removal happens in Drop, if the Drain iterator is leaked,
+        // the removal will not happen.
+        let len = self.len();
+        let start = match range.start() {
+            Included(&n) => n,
+            Excluded(&n) => n + 1,
+            Unbounded => 0,
+        };
+        let end = match range.end() {
+            Included(&n) => n + 1,
+            Excluded(&n) => n,
+            Unbounded => len,
+        };
+
+        // Take out two simultaneous borrows. The &mut String won't be accessed
+        // until iteration is over, in Drop.
+        let self_ptr = self as *mut _;
+        // slicing does the appropriate bounds checks
+        let chars_iter = self[start..end].chars();
+
+        Drain {
+            start: start,
+            end: end,
+            iter: chars_iter,
+            string: self_ptr,
+        }
+    }
+
+    /// Creates a splicing iterator that removes the specified range in the string,
+    /// replaces with the given string, and yields the removed chars.
+    /// The given string doesn’t need to be the same length as the range.
+    ///
+    /// Note: The element range is removed when the `Splice` is dropped,
+    /// even if the iterator is not consumed until the end.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the starting point or end point do not lie on a [`char`]
+    /// boundary, or if they're out of bounds.
+    ///
+    /// [`char`]: ../../std/primitive.char.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(splice)]
+    /// let mut s = String::from("α is alpha, β is beta");
+    /// let beta_offset = s.find('β').unwrap_or(s.len());
+    ///
+    /// // Replace the range up until the β from the string
+    /// let t: String = s.splice(..beta_offset, "Α is capital alpha; ").collect();
+    /// assert_eq!(t, "α is alpha, ");
+    /// assert_eq!(s, "Α is capital alpha; β is beta");
+    /// ```
+    #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+    pub fn splice<'a, 'b, R>(&'a mut self, range: R, replace_with: &'b str) -> Splice<'a, 'b>
+        where R: RangeArgument<usize>
+    {
+        // Memory safety
+        //
+        // The String version of Splice does not have the memory safety issues
+        // of the vector version. The data is just plain bytes.
+        // Because the range removal happens in Drop, if the Splice iterator is leaked,
+        // the removal will not happen.
+        let len = self.len();
+        let start = match range.start() {
+             Included(&n) => n,
+             Excluded(&n) => n + 1,
+             Unbounded => 0,
+        };
+        let end = match range.end() {
+             Included(&n) => n + 1,
+             Excluded(&n) => n,
+             Unbounded => len,
+        };
+
+        // Take out two simultaneous borrows. The &mut String won't be accessed
+        // until iteration is over, in Drop.
+        let self_ptr = self as *mut _;
+        // slicing does the appropriate bounds checks
+        let chars_iter = self[start..end].chars();
+
+        Splice {
+            start: start,
+            end: end,
+            iter: chars_iter,
+            string: self_ptr,
+            replace_with: replace_with
+        }
+    }
+
+    /// Converts this `String` into a `Box<str>`.
+    ///
+    /// This will drop any excess capacity.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s = String::from("hello");
+    ///
+    /// let b = s.into_boxed_str();
+    /// ```
+    #[stable(feature = "box_str", since = "1.4.0")]
+    pub fn into_boxed_str(self) -> Box<str> {
+        let slice = self.vec.into_boxed_slice();
+        unsafe { from_boxed_utf8_unchecked(slice) }
+    }
+}
+
+impl FromUtf8Error {
+    /// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(from_utf8_error_as_bytes)]
+    /// // some invalid bytes, in a vector
+    /// let bytes = vec![0, 159];
+    ///
+    /// let value = String::from_utf8(bytes);
+    ///
+    /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes());
+    /// ```
+    #[unstable(feature = "from_utf8_error_as_bytes", reason = "recently added", issue = "40895")]
+    pub fn as_bytes(&self) -> &[u8] {
+        &self.bytes[..]
+    }
+
+    /// Returns the bytes that were attempted to convert to a `String`.
+    ///
+    /// This method is carefully constructed to avoid allocation. It will
+    /// consume the error, moving out the bytes, so that a copy of the bytes
+    /// does not need to be made.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // some invalid bytes, in a vector
+    /// let bytes = vec![0, 159];
+    ///
+    /// let value = String::from_utf8(bytes);
+    ///
+    /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn into_bytes(self) -> Vec<u8> {
+        self.bytes
+    }
+
+    /// Fetch a `Utf8Error` to get more details about the conversion failure.
+    ///
+    /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may
+    /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's
+    /// an analogue to `FromUtf8Error`. See its documentation for more details
+    /// on using it.
+    ///
+    /// [`Utf8Error`]: ../../std/str/struct.Utf8Error.html
+    /// [`std::str`]: ../../std/str/index.html
+    /// [`u8`]: ../../std/primitive.u8.html
+    /// [`&str`]: ../../std/primitive.str.html
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // some invalid bytes, in a vector
+    /// let bytes = vec![0, 159];
+    ///
+    /// let error = String::from_utf8(bytes).unwrap_err().utf8_error();
+    ///
+    /// // the first byte is invalid here
+    /// assert_eq!(1, error.valid_up_to());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn utf8_error(&self) -> Utf8Error {
+        self.error
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for FromUtf8Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.error, f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for FromUtf16Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt("invalid utf-16: lone surrogate found", f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Clone for String {
+    fn clone(&self) -> Self {
+        String { vec: self.vec.clone() }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        self.vec.clone_from(&source.vec);
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl FromIterator<char> for String {
+    fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String {
+        let mut buf = String::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[stable(feature = "string_from_iter_by_ref", since = "1.17.0")]
+impl<'a> FromIterator<&'a char> for String {
+    fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String {
+        let mut buf = String::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> FromIterator<&'a str> for String {
+    fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String {
+        let mut buf = String::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[stable(feature = "extend_string", since = "1.4.0")]
+impl FromIterator<String> for String {
+    fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
+        let mut buf = String::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[stable(feature = "herd_cows", since = "1.19.0")]
+impl<'a> FromIterator<Cow<'a, str>> for String {
+    fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String {
+        let mut buf = String::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Extend<char> for String {
+    fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) {
+        let iterator = iter.into_iter();
+        let (lower_bound, _) = iterator.size_hint();
+        self.reserve(lower_bound);
+        for ch in iterator {
+            self.push(ch)
+        }
+    }
+}
+
+#[stable(feature = "extend_ref", since = "1.2.0")]
+impl<'a> Extend<&'a char> for String {
+    fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) {
+        self.extend(iter.into_iter().cloned());
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> Extend<&'a str> for String {
+    fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
+        for s in iter {
+            self.push_str(s)
+        }
+    }
+}
+
+#[stable(feature = "extend_string", since = "1.4.0")]
+impl Extend<String> for String {
+    fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
+        for s in iter {
+            self.push_str(&s)
+        }
+    }
+}
+
+#[stable(feature = "herd_cows", since = "1.19.0")]
+impl<'a> Extend<Cow<'a, str>> for String {
+    fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) {
+        for s in iter {
+            self.push_str(&s)
+        }
+    }
+}
+
+/// A convenience impl that delegates to the impl for `&str`
+#[unstable(feature = "pattern",
+           reason = "API not fully fleshed out and ready to be stabilized",
+           issue = "27721")]
+impl<'a, 'b> Pattern<'a> for &'b String {
+    type Searcher = <&'b str as Pattern<'a>>::Searcher;
+
+    fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
+        self[..].into_searcher(haystack)
+    }
+
+    #[inline]
+    fn is_contained_in(self, haystack: &'a str) -> bool {
+        self[..].is_contained_in(haystack)
+    }
+
+    #[inline]
+    fn is_prefix_of(self, haystack: &'a str) -> bool {
+        self[..].is_prefix_of(haystack)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl PartialEq for String {
+    #[inline]
+    fn eq(&self, other: &String) -> bool {
+        PartialEq::eq(&self[..], &other[..])
+    }
+    #[inline]
+    fn ne(&self, other: &String) -> bool {
+        PartialEq::ne(&self[..], &other[..])
+    }
+}
+
+macro_rules! impl_eq {
+    ($lhs:ty, $rhs: ty) => {
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl<'a, 'b> PartialEq<$rhs> for $lhs {
+            #[inline]
+            fn eq(&self, other: &$rhs) -> bool { PartialEq::eq(&self[..], &other[..]) }
+            #[inline]
+            fn ne(&self, other: &$rhs) -> bool { PartialEq::ne(&self[..], &other[..]) }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl<'a, 'b> PartialEq<$lhs> for $rhs {
+            #[inline]
+            fn eq(&self, other: &$lhs) -> bool { PartialEq::eq(&self[..], &other[..]) }
+            #[inline]
+            fn ne(&self, other: &$lhs) -> bool { PartialEq::ne(&self[..], &other[..]) }
+        }
+
+    }
+}
+
+impl_eq! { String, str }
+impl_eq! { String, &'a str }
+impl_eq! { Cow<'a, str>, str }
+impl_eq! { Cow<'a, str>, &'b str }
+impl_eq! { Cow<'a, str>, String }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl Default for String {
+    /// Creates an empty `String`.
+    #[inline]
+    fn default() -> String {
+        String::new()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Display for String {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&**self, f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for String {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl hash::Hash for String {
+    #[inline]
+    fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
+        (**self).hash(hasher)
+    }
+}
+
+/// Implements the `+` operator for concatenating two strings.
+///
+/// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if
+/// necessary). This is done to avoid allocating a new `String` and copying the entire contents on
+/// every operation, which would lead to `O(n^2)` running time when building an `n`-byte string by
+/// repeated concatenation.
+///
+/// The string on the right-hand side is only borrowed; its contents are copied into the returned
+/// `String`.
+///
+/// # Examples
+///
+/// Concatenating two `String`s takes the first by value and borrows the second:
+///
+/// ```
+/// let a = String::from("hello");
+/// let b = String::from(" world");
+/// let c = a + &b;
+/// // `a` is moved and can no longer be used here.
+/// ```
+///
+/// If you want to keep using the first `String`, you can clone it and append to the clone instead:
+///
+/// ```
+/// let a = String::from("hello");
+/// let b = String::from(" world");
+/// let c = a.clone() + &b;
+/// // `a` is still valid here.
+/// ```
+///
+/// Concatenating `&str` slices can be done by converting the first to a `String`:
+///
+/// ```
+/// let a = "hello";
+/// let b = " world";
+/// let c = a.to_string() + b;
+/// ```
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> Add<&'a str> for String {
+    type Output = String;
+
+    #[inline]
+    fn add(mut self, other: &str) -> String {
+        self.push_str(other);
+        self
+    }
+}
+
+/// Implements the `+=` operator for appending to a `String`.
+///
+/// This has the same behavior as the [`push_str`] method.
+///
+/// [`push_str`]: struct.String.html#method.push_str
+#[stable(feature = "stringaddassign", since = "1.12.0")]
+impl<'a> AddAssign<&'a str> for String {
+    #[inline]
+    fn add_assign(&mut self, other: &str) {
+        self.push_str(other);
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::Range<usize>> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, index: ops::Range<usize>) -> &str {
+        &self[..][index]
+    }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeTo<usize>> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, index: ops::RangeTo<usize>) -> &str {
+        &self[..][index]
+    }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeFrom<usize>> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, index: ops::RangeFrom<usize>) -> &str {
+        &self[..][index]
+    }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Index<ops::RangeFull> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, _index: ops::RangeFull) -> &str {
+        unsafe { str::from_utf8_unchecked(&self.vec) }
+    }
+}
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl ops::Index<ops::RangeInclusive<usize>> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, index: ops::RangeInclusive<usize>) -> &str {
+        Index::index(&**self, index)
+    }
+}
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl ops::Index<ops::RangeToInclusive<usize>> for String {
+    type Output = str;
+
+    #[inline]
+    fn index(&self, index: ops::RangeToInclusive<usize>) -> &str {
+        Index::index(&**self, index)
+    }
+}
+
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::Range<usize>> for String {
+    #[inline]
+    fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str {
+        &mut self[..][index]
+    }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeTo<usize>> for String {
+    #[inline]
+    fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str {
+        &mut self[..][index]
+    }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeFrom<usize>> for String {
+    #[inline]
+    fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str {
+        &mut self[..][index]
+    }
+}
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::IndexMut<ops::RangeFull> for String {
+    #[inline]
+    fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str {
+        unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
+    }
+}
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl ops::IndexMut<ops::RangeInclusive<usize>> for String {
+    #[inline]
+    fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str {
+        IndexMut::index_mut(&mut **self, index)
+    }
+}
+#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
+impl ops::IndexMut<ops::RangeToInclusive<usize>> for String {
+    #[inline]
+    fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str {
+        IndexMut::index_mut(&mut **self, index)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl ops::Deref for String {
+    type Target = str;
+
+    #[inline]
+    fn deref(&self) -> &str {
+        unsafe { str::from_utf8_unchecked(&self.vec) }
+    }
+}
+
+#[stable(feature = "derefmut_for_string", since = "1.3.0")]
+impl ops::DerefMut for String {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut str {
+        unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
+    }
+}
+
+/// An error when parsing a `String`.
+///
+/// This `enum` is slightly awkward: it will never actually exist. This error is
+/// part of the type signature of the implementation of [`FromStr`] on
+/// [`String`]. The return type of [`from_str`], requires that an error be
+/// defined, but, given that a [`String`] can always be made into a new
+/// [`String`] without error, this type will never actually be returned. As
+/// such, it is only here to satisfy said signature, and is useless otherwise.
+///
+/// [`FromStr`]: ../../std/str/trait.FromStr.html
+/// [`String`]: struct.String.html
+/// [`from_str`]: ../../std/str/trait.FromStr.html#tymethod.from_str
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+#[derive(Copy)]
+pub enum ParseError {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl FromStr for String {
+    type Err = ParseError;
+    #[inline]
+    fn from_str(s: &str) -> Result<String, ParseError> {
+        Ok(String::from(s))
+    }
+}
+
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+impl Clone for ParseError {
+    fn clone(&self) -> ParseError {
+        match *self {}
+    }
+}
+
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+impl fmt::Debug for ParseError {
+    fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
+        match *self {}
+    }
+}
+
+#[stable(feature = "str_parse_error2", since = "1.8.0")]
+impl fmt::Display for ParseError {
+    fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
+        match *self {}
+    }
+}
+
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+impl PartialEq for ParseError {
+    fn eq(&self, _: &ParseError) -> bool {
+        match *self {}
+    }
+}
+
+#[stable(feature = "str_parse_error", since = "1.5.0")]
+impl Eq for ParseError {}
+
+/// A trait for converting a value to a `String`.
+///
+/// This trait is automatically implemented for any type which implements the
+/// [`Display`] trait. As such, `ToString` shouldn't be implemented directly:
+/// [`Display`] should be implemented instead, and you get the `ToString`
+/// implementation for free.
+///
+/// [`Display`]: ../../std/fmt/trait.Display.html
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait ToString {
+    /// Converts the given value to a `String`.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let i = 5;
+    /// let five = String::from("5");
+    ///
+    /// assert_eq!(five, i.to_string());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn to_string(&self) -> String;
+}
+
+/// # Panics
+///
+/// In this implementation, the `to_string` method panics
+/// if the `Display` implementation returns an error.
+/// This indicates an incorrect `Display` implementation
+/// since `fmt::Write for String` never returns an error itself.
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: fmt::Display + ?Sized> ToString for T {
+    #[inline]
+    default fn to_string(&self) -> String {
+        use core::fmt::Write;
+        let mut buf = String::new();
+        buf.write_fmt(format_args!("{}", self))
+           .expect("a Display implementation return an error unexpectedly");
+        buf.shrink_to_fit();
+        buf
+    }
+}
+
+#[stable(feature = "str_to_string_specialization", since = "1.9.0")]
+impl ToString for str {
+    #[inline]
+    fn to_string(&self) -> String {
+        String::from(self)
+    }
+}
+
+#[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")]
+impl<'a> ToString for Cow<'a, str> {
+    #[inline]
+    fn to_string(&self) -> String {
+        self[..].to_owned()
+    }
+}
+
+#[stable(feature = "string_to_string_specialization", since = "1.17.0")]
+impl ToString for String {
+    #[inline]
+    fn to_string(&self) -> String {
+        self.to_owned()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl AsRef<str> for String {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl AsRef<[u8]> for String {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_bytes()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<&'a str> for String {
+    fn from(s: &'a str) -> String {
+        s.to_owned()
+    }
+}
+
+// note: test pulls in libstd, which causes errors here
+#[cfg(not(test))]
+#[stable(feature = "string_from_box", since = "1.18.0")]
+impl From<Box<str>> for String {
+    fn from(s: Box<str>) -> String {
+        s.into_string()
+    }
+}
+
+#[stable(feature = "box_from_str", since = "1.18.0")]
+impl Into<Box<str>> for String {
+    fn into(self) -> Box<str> {
+        self.into_boxed_str()
+    }
+}
+
+#[stable(feature = "string_from_cow_str", since = "1.14.0")]
+impl<'a> From<Cow<'a, str>> for String {
+    fn from(s: Cow<'a, str>) -> String {
+        s.into_owned()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<&'a str> for Cow<'a, str> {
+    #[inline]
+    fn from(s: &'a str) -> Cow<'a, str> {
+        Cow::Borrowed(s)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<String> for Cow<'a, str> {
+    #[inline]
+    fn from(s: String) -> Cow<'a, str> {
+        Cow::Owned(s)
+    }
+}
+
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a> FromIterator<char> for Cow<'a, str> {
+    fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> {
+        Cow::Owned(FromIterator::from_iter(it))
+    }
+}
+
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> {
+    fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> {
+        Cow::Owned(FromIterator::from_iter(it))
+    }
+}
+
+#[stable(feature = "cow_str_from_iter", since = "1.12.0")]
+impl<'a> FromIterator<String> for Cow<'a, str> {
+    fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> {
+        Cow::Owned(FromIterator::from_iter(it))
+    }
+}
+
+#[stable(feature = "from_string_for_vec_u8", since = "1.14.0")]
+impl From<String> for Vec<u8> {
+    fn from(string: String) -> Vec<u8> {
+        string.into_bytes()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Write for String {
+    #[inline]
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.push_str(s);
+        Ok(())
+    }
+
+    #[inline]
+    fn write_char(&mut self, c: char) -> fmt::Result {
+        self.push(c);
+        Ok(())
+    }
+}
+
+/// A draining iterator for `String`.
+///
+/// This struct is created by the [`drain`] method on [`String`]. See its
+/// documentation for more.
+///
+/// [`drain`]: struct.String.html#method.drain
+/// [`String`]: struct.String.html
+#[stable(feature = "drain", since = "1.6.0")]
+pub struct Drain<'a> {
+    /// Will be used as &'a mut String in the destructor
+    string: *mut String,
+    /// Start of part to remove
+    start: usize,
+    /// End of part to remove
+    end: usize,
+    /// Current remaining range to remove
+    iter: Chars<'a>,
+}
+
+#[stable(feature = "collection_debug", since = "1.17.0")]
+impl<'a> fmt::Debug for Drain<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Drain { .. }")
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<'a> Sync for Drain<'a> {}
+#[stable(feature = "drain", since = "1.6.0")]
+unsafe impl<'a> Send for Drain<'a> {}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<'a> Drop for Drain<'a> {
+    fn drop(&mut self) {
+        unsafe {
+            // Use Vec::drain. "Reaffirm" the bounds checks to avoid
+            // panic code being inserted again.
+            let self_vec = (*self.string).as_mut_vec();
+            if self.start <= self.end && self.end <= self_vec.len() {
+                self_vec.drain(self.start..self.end);
+            }
+        }
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<'a> Iterator for Drain<'a> {
+    type Item = char;
+
+    #[inline]
+    fn next(&mut self) -> Option<char> {
+        self.iter.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[stable(feature = "drain", since = "1.6.0")]
+impl<'a> DoubleEndedIterator for Drain<'a> {
+    #[inline]
+    fn next_back(&mut self) -> Option<char> {
+        self.iter.next_back()
+    }
+}
+
+#[unstable(feature = "fused", issue = "35602")]
+impl<'a> FusedIterator for Drain<'a> {}
+
+/// A splicing iterator for `String`.
+///
+/// This struct is created by the [`splice()`] method on [`String`]. See its
+/// documentation for more.
+///
+/// [`splice()`]: struct.String.html#method.splice
+/// [`String`]: struct.String.html
+#[derive(Debug)]
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+pub struct Splice<'a, 'b> {
+    /// Will be used as &'a mut String in the destructor
+    string: *mut String,
+    /// Start of part to remove
+    start: usize,
+    /// End of part to remove
+    end: usize,
+    /// Current remaining range to remove
+    iter: Chars<'a>,
+    replace_with: &'b str,
+}
+
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+unsafe impl<'a, 'b> Sync for Splice<'a, 'b> {}
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+unsafe impl<'a, 'b> Send for Splice<'a, 'b> {}
+
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+impl<'a, 'b> Drop for Splice<'a, 'b> {
+    fn drop(&mut self) {
+        unsafe {
+            let vec = (*self.string).as_mut_vec();
+            vec.splice(self.start..self.end, self.replace_with.bytes());
+        }
+    }
+}
+
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+impl<'a, 'b> Iterator for Splice<'a, 'b> {
+    type Item = char;
+
+    #[inline]
+    fn next(&mut self) -> Option<char> {
+        self.iter.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+impl<'a, 'b> DoubleEndedIterator for Splice<'a, 'b> {
+    #[inline]
+    fn next_back(&mut self) -> Option<char> {
+        self.iter.next_back()
+    }
+}