Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 2062 insertions, 0 deletions

diff --git a/third_party/rust/arrayvec/src/array.rs b/third_party/rust/arrayvec/src/array.rs
new file mode 100644
index 0000000000..96a8bfd284
--- /dev/null
+++ b/third_party/rust/arrayvec/src/array.rs
@@ -0,0 +1,144 @@
+
+/// Trait for fixed size arrays.
+///
+/// This trait is implemented for some specific array sizes, see
+/// the implementor list below. At the current state of Rust we can't
+/// make this fully general for every array size.
+///
+/// The following crate features add more array sizes (and they are not
+/// enabled by default due to their impact on compliation speed).
+///
+/// - `array-sizes-33-128`: All sizes 33 to 128 are implemented
+///   (a few in this range are included by default).
+/// - `array-sizes-129-255`: All sizes 129 to 255 are implemented
+///   (a few in this range are included by default).
+///
+/// ## Safety
+///
+/// This trait can *only* be implemented by fixed-size arrays or types with
+/// *exactly* the representation of a fixed size array (of the right element
+/// type and capacity).
+///
+/// Normally this trait is an implementation detail of arrayvec and doesn’t
+/// need implementing.
+pub unsafe trait Array {
+    /// The array’s element type
+    type Item;
+    /// The smallest type that can index and tell the length of the array.
+    #[doc(hidden)]
+    type Index: Index;
+    /// The array's element capacity
+    const CAPACITY: usize;
+    fn as_slice(&self) -> &[Self::Item];
+    fn as_mut_slice(&mut self) -> &mut [Self::Item];
+}
+
+pub trait Index : PartialEq + Copy {
+    fn to_usize(self) -> usize;
+    fn from(_: usize) -> Self;
+}
+
+impl Index for () {
+    #[inline(always)]
+    fn to_usize(self) -> usize { 0 }
+    #[inline(always)]
+    fn from(_ix: usize) ->  Self { () }
+}
+
+impl Index for bool {
+    #[inline(always)]
+    fn to_usize(self) -> usize { self as usize }
+    #[inline(always)]
+    fn from(ix: usize) ->  Self { ix != 0 }
+}
+
+impl Index for u8 {
+    #[inline(always)]
+    fn to_usize(self) -> usize { self as usize }
+    #[inline(always)]
+    fn from(ix: usize) ->  Self { ix as u8 }
+}
+
+impl Index for u16 {
+    #[inline(always)]
+    fn to_usize(self) -> usize { self as usize }
+    #[inline(always)]
+    fn from(ix: usize) ->  Self { ix as u16 }
+}
+
+impl Index for u32 {
+    #[inline(always)]
+    fn to_usize(self) -> usize { self as usize }
+    #[inline(always)]
+    fn from(ix: usize) ->  Self { ix as u32 }
+}
+
+impl Index for usize {
+    #[inline(always)]
+    fn to_usize(self) -> usize { self }
+    #[inline(always)]
+    fn from(ix: usize) ->  Self { ix }
+}
+
+macro_rules! fix_array_impl {
+    ($index_type:ty, $len:expr ) => (
+        unsafe impl<T> Array for [T; $len] {
+            type Item = T;
+            type Index = $index_type;
+            const CAPACITY: usize = $len;
+            #[doc(hidden)]
+            fn as_slice(&self) -> &[Self::Item] { self }
+            #[doc(hidden)]
+            fn as_mut_slice(&mut self) -> &mut [Self::Item] { self }
+        }
+    )
+}
+
+macro_rules! fix_array_impl_recursive {
+    ($index_type:ty, ) => ();
+    ($index_type:ty, $($len:expr,)*) => (
+        $(fix_array_impl!($index_type, $len);)*
+    );
+}
+
+
+fix_array_impl_recursive!((), 0,);
+fix_array_impl_recursive!(bool, 1,);
+fix_array_impl_recursive!(u8, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+                          15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
+                          28, 29, 30, 31, );
+
+#[cfg(not(feature="array-sizes-33-128"))]
+fix_array_impl_recursive!(u8, 32, 40, 48, 50, 56, 64, 72, 96, 100, 128, );
+
+#[cfg(feature="array-sizes-33-128")]
+fix_array_impl_recursive!(u8, 
+32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
+52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,
+72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91,
+92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108,
+109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124,
+125, 126, 127, 128,
+);
+
+#[cfg(not(feature="array-sizes-129-255"))]
+fix_array_impl_recursive!(u8, 160, 192, 200, 224,);
+
+#[cfg(feature="array-sizes-129-255")]
+fix_array_impl_recursive!(u8,
+129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,
+141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156,
+157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172,
+173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188,
+189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204,
+205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220,
+221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236,
+237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252,
+253, 254, 255,
+);
+
+fix_array_impl_recursive!(u16, 256, 384, 512, 768, 1024, 2048, 4096, 8192, 16384, 32768,);
+// This array size doesn't exist on 16-bit
+#[cfg(any(target_pointer_width="32", target_pointer_width="64"))]
+fix_array_impl_recursive!(u32, 1 << 16,);
+
diff --git a/third_party/rust/arrayvec/src/array_string.rs b/third_party/rust/arrayvec/src/array_string.rs
new file mode 100644
index 0000000000..30aea4a49e
--- /dev/null
+++ b/third_party/rust/arrayvec/src/array_string.rs
@@ -0,0 +1,567 @@
+use std::borrow::Borrow;
+use std::cmp;
+use std::fmt;
+use std::hash::{Hash, Hasher};
+use std::ptr;
+use std::ops::{Deref, DerefMut};
+use std::str;
+use std::str::FromStr;
+use std::str::Utf8Error;
+use std::slice;
+
+use crate::array::Array;
+use crate::array::Index;
+use crate::CapacityError;
+use crate::char::encode_utf8;
+
+#[cfg(feature="serde")]
+use serde::{Serialize, Deserialize, Serializer, Deserializer};
+
+use super::MaybeUninit as MaybeUninitCopy;
+
+/// A string with a fixed capacity.
+///
+/// The `ArrayString` is a string backed by a fixed size array. It keeps track
+/// of its length.
+///
+/// The string is a contiguous value that you can store directly on the stack
+/// if needed.
+#[derive(Copy)]
+pub struct ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    xs: MaybeUninitCopy<A>,
+    len: A::Index,
+}
+
+impl<A> Default for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    /// Return an empty `ArrayString`
+    fn default() -> ArrayString<A> {
+        ArrayString::new()
+    }
+}
+
+impl<A> ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    /// Create a new empty `ArrayString`.
+    ///
+    /// Capacity is inferred from the type parameter.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 16]>::new();
+    /// string.push_str("foo");
+    /// assert_eq!(&string[..], "foo");
+    /// assert_eq!(string.capacity(), 16);
+    /// ```
+    pub fn new() -> ArrayString<A> {
+        unsafe {
+            ArrayString {
+                xs: MaybeUninitCopy::uninitialized(),
+                len: Index::from(0),
+            }
+        }
+    }
+
+    /// Return the length of the string.
+    #[inline]
+    pub fn len(&self) -> usize { self.len.to_usize() }
+
+    /// Create a new `ArrayString` from a `str`.
+    ///
+    /// Capacity is inferred from the type parameter.
+    ///
+    /// **Errors** if the backing array is not large enough to fit the string.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 3]>::from("foo").unwrap();
+    /// assert_eq!(&string[..], "foo");
+    /// assert_eq!(string.len(), 3);
+    /// assert_eq!(string.capacity(), 3);
+    /// ```
+    pub fn from(s: &str) -> Result<Self, CapacityError<&str>> {
+        let mut arraystr = Self::new();
+        arraystr.try_push_str(s)?;
+        Ok(arraystr)
+    }
+
+    /// Create a new `ArrayString` from a byte string literal.
+    ///
+    /// **Errors** if the byte string literal is not valid UTF-8.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let string = ArrayString::from_byte_string(b"hello world").unwrap();
+    /// ```
+    pub fn from_byte_string(b: &A) -> Result<Self, Utf8Error> {
+        let len = str::from_utf8(b.as_slice())?.len();
+        debug_assert_eq!(len, A::CAPACITY);
+        Ok(ArrayString {
+            xs: MaybeUninitCopy::from(*b),
+            len: Index::from(A::CAPACITY),
+        })
+    }
+
+    /// Return the capacity of the `ArrayString`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let string = ArrayString::<[_; 3]>::new();
+    /// assert_eq!(string.capacity(), 3);
+    /// ```
+    #[inline(always)]
+    pub fn capacity(&self) -> usize { A::CAPACITY }
+
+    /// Return if the `ArrayString` is completely filled.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 1]>::new();
+    /// assert!(!string.is_full());
+    /// string.push_str("A");
+    /// assert!(string.is_full());
+    /// ```
+    pub fn is_full(&self) -> bool { self.len() == self.capacity() }
+
+    /// Adds the given char to the end of the string.
+    ///
+    /// ***Panics*** if the backing array is not large enough to fit the additional char.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 2]>::new();
+    ///
+    /// string.push('a');
+    /// string.push('b');
+    ///
+    /// assert_eq!(&string[..], "ab");
+    /// ```
+    pub fn push(&mut self, c: char) {
+        self.try_push(c).unwrap();
+    }
+
+    /// Adds the given char to the end of the string.
+    ///
+    /// Returns `Ok` if the push succeeds.
+    ///
+    /// **Errors** if the backing array is not large enough to fit the additional char.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 2]>::new();
+    ///
+    /// string.try_push('a').unwrap();
+    /// string.try_push('b').unwrap();
+    /// let overflow = string.try_push('c');
+    ///
+    /// assert_eq!(&string[..], "ab");
+    /// assert_eq!(overflow.unwrap_err().element(), 'c');
+    /// ```
+    pub fn try_push(&mut self, c: char) -> Result<(), CapacityError<char>> {
+        let len = self.len();
+        unsafe {
+            let ptr = self.xs.ptr_mut().add(len);
+            let remaining_cap = self.capacity() - len;
+            match encode_utf8(c, ptr, remaining_cap) {
+                Ok(n) => {
+                    self.set_len(len + n);
+                    Ok(())
+                }
+                Err(_) => Err(CapacityError::new(c)),
+            }
+        }
+    }
+
+    /// Adds the given string slice to the end of the string.
+    ///
+    /// ***Panics*** if the backing array is not large enough to fit the string.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 2]>::new();
+    ///
+    /// string.push_str("a");
+    /// string.push_str("d");
+    ///
+    /// assert_eq!(&string[..], "ad");
+    /// ```
+    pub fn push_str(&mut self, s: &str) {
+        self.try_push_str(s).unwrap()
+    }
+
+    /// Adds the given string slice to the end of the string.
+    ///
+    /// Returns `Ok` if the push succeeds.
+    ///
+    /// **Errors** if the backing array is not large enough to fit the string.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 2]>::new();
+    ///
+    /// string.try_push_str("a").unwrap();
+    /// let overflow1 = string.try_push_str("bc");
+    /// string.try_push_str("d").unwrap();
+    /// let overflow2 = string.try_push_str("ef");
+    ///
+    /// assert_eq!(&string[..], "ad");
+    /// assert_eq!(overflow1.unwrap_err().element(), "bc");
+    /// assert_eq!(overflow2.unwrap_err().element(), "ef");
+    /// ```
+    pub fn try_push_str<'a>(&mut self, s: &'a str) -> Result<(), CapacityError<&'a str>> {
+        if s.len() > self.capacity() - self.len() {
+            return Err(CapacityError::new(s));
+        }
+        unsafe {
+            let dst = self.xs.ptr_mut().offset(self.len() as isize);
+            let src = s.as_ptr();
+            ptr::copy_nonoverlapping(src, dst, s.len());
+            let newl = self.len() + s.len();
+            self.set_len(newl);
+        }
+        Ok(())
+    }
+
+    /// Removes the last character from the string and returns it.
+    ///
+    /// Returns `None` if this `ArrayString` is empty.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    /// 
+    /// let mut s = ArrayString::<[_; 3]>::from("foo").unwrap();
+    ///
+    /// assert_eq!(s.pop(), Some('o'));
+    /// assert_eq!(s.pop(), Some('o'));
+    /// assert_eq!(s.pop(), Some('f'));
+    ///
+    /// assert_eq!(s.pop(), None);
+    /// ```
+    pub fn pop(&mut self) -> Option<char> {
+        let ch = match self.chars().rev().next() {
+            Some(ch) => ch,
+            None => return None,
+        };
+        let new_len = self.len() - ch.len_utf8();
+        unsafe {
+            self.set_len(new_len);
+        }
+        Some(ch)
+    }
+
+    /// Shortens this `ArrayString` to the specified length.
+    ///
+    /// If `new_len` is greater than the string’s current length, this has no
+    /// effect.
+    ///
+    /// ***Panics*** if `new_len` does not lie on a `char` boundary.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    ///
+    /// let mut string = ArrayString::<[_; 6]>::from("foobar").unwrap();
+    /// string.truncate(3);
+    /// assert_eq!(&string[..], "foo");
+    /// string.truncate(4);
+    /// assert_eq!(&string[..], "foo");
+    /// ```
+    pub fn truncate(&mut self, new_len: usize) {
+        if new_len <= self.len() {
+            assert!(self.is_char_boundary(new_len));
+            unsafe { 
+                // In libstd truncate is called on the underlying vector,
+                // which in turns drops each element.
+                // As we know we don't have to worry about Drop,
+                // we can just set the length (a la clear.)
+                self.set_len(new_len);
+            }
+        }
+    }
+
+    /// Removes a `char` from this `ArrayString` at a byte position and returns it.
+    ///
+    /// This is an `O(n)` operation, as it requires copying every element in the
+    /// array.
+    ///
+    /// ***Panics*** if `idx` is larger than or equal to the `ArrayString`’s length,
+    /// or if it does not lie on a `char` boundary.
+    ///
+    /// ```
+    /// use arrayvec::ArrayString;
+    /// 
+    /// let mut s = ArrayString::<[_; 3]>::from("foo").unwrap();
+    ///
+    /// assert_eq!(s.remove(0), 'f');
+    /// assert_eq!(s.remove(1), 'o');
+    /// assert_eq!(s.remove(0), 'o');
+    /// ```
+    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.xs.ptr().offset(next as isize),
+                      self.xs.ptr_mut().offset(idx as isize),
+                      len - next);
+            self.set_len(len - (next - idx));
+        }
+        ch
+    }
+
+    /// Make the string empty.
+    pub fn clear(&mut self) {
+        unsafe {
+            self.set_len(0);
+        }
+    }
+
+    /// Set the strings’s length.
+    ///
+    /// This function is `unsafe` because it changes the notion of the
+    /// number of “valid” bytes in the string. Use with care.
+    ///
+    /// This method uses *debug assertions* to check the validity of `length`
+    /// and may use other debug assertions.
+    pub unsafe fn set_len(&mut self, length: usize) {
+        debug_assert!(length <= self.capacity());
+        self.len = Index::from(length);
+    }
+
+    /// Return a string slice of the whole `ArrayString`.
+    pub fn as_str(&self) -> &str {
+        self
+    }
+}
+
+impl<A> Deref for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    type Target = str;
+    #[inline]
+    fn deref(&self) -> &str {
+        unsafe {
+            let sl = slice::from_raw_parts(self.xs.ptr(), self.len.to_usize());
+            str::from_utf8_unchecked(sl)
+        }
+    }
+}
+
+impl<A> DerefMut for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    #[inline]
+    fn deref_mut(&mut self) -> &mut str {
+        unsafe {
+            let sl = slice::from_raw_parts_mut(self.xs.ptr_mut(), self.len.to_usize());
+            str::from_utf8_unchecked_mut(sl)
+        }
+    }
+}
+
+impl<A> PartialEq for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn eq(&self, rhs: &Self) -> bool {
+        **self == **rhs
+    }
+}
+
+impl<A> PartialEq<str> for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn eq(&self, rhs: &str) -> bool {
+        &**self == rhs
+    }
+}
+
+impl<A> PartialEq<ArrayString<A>> for str
+    where A: Array<Item=u8> + Copy
+{
+    fn eq(&self, rhs: &ArrayString<A>) -> bool {
+        self == &**rhs
+    }
+}
+
+impl<A> Eq for ArrayString<A> 
+    where A: Array<Item=u8> + Copy
+{ }
+
+impl<A> Hash for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        (**self).hash(h)
+    }
+}
+
+impl<A> Borrow<str> for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn borrow(&self) -> &str { self }
+}
+
+impl<A> AsRef<str> for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn as_ref(&self) -> &str { self }
+}
+
+impl<A> fmt::Debug for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }
+}
+
+impl<A> fmt::Display for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }
+}
+
+/// `Write` appends written data to the end of the string.
+impl<A> fmt::Write for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn write_char(&mut self, c: char) -> fmt::Result {
+        self.try_push(c).map_err(|_| fmt::Error)
+    }
+
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.try_push_str(s).map_err(|_| fmt::Error)
+    }
+}
+
+impl<A> Clone for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn clone(&self) -> ArrayString<A> {
+        *self
+    }
+    fn clone_from(&mut self, rhs: &Self) {
+        // guaranteed to fit due to types matching.
+        self.clear();
+        self.try_push_str(rhs).ok();
+    }
+}
+
+impl<A> PartialOrd for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn partial_cmp(&self, rhs: &Self) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(&**rhs)
+    }
+    fn lt(&self, rhs: &Self) -> bool { **self < **rhs }
+    fn le(&self, rhs: &Self) -> bool { **self <= **rhs }
+    fn gt(&self, rhs: &Self) -> bool { **self > **rhs }
+    fn ge(&self, rhs: &Self) -> bool { **self >= **rhs }
+}
+
+impl<A> PartialOrd<str> for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn partial_cmp(&self, rhs: &str) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(rhs)
+    }
+    fn lt(&self, rhs: &str) -> bool { &**self < rhs }
+    fn le(&self, rhs: &str) -> bool { &**self <= rhs }
+    fn gt(&self, rhs: &str) -> bool { &**self > rhs }
+    fn ge(&self, rhs: &str) -> bool { &**self >= rhs }
+}
+
+impl<A> PartialOrd<ArrayString<A>> for str
+    where A: Array<Item=u8> + Copy
+{
+    fn partial_cmp(&self, rhs: &ArrayString<A>) -> Option<cmp::Ordering> {
+        self.partial_cmp(&**rhs)
+    }
+    fn lt(&self, rhs: &ArrayString<A>) -> bool { self < &**rhs }
+    fn le(&self, rhs: &ArrayString<A>) -> bool { self <= &**rhs }
+    fn gt(&self, rhs: &ArrayString<A>) -> bool { self > &**rhs }
+    fn ge(&self, rhs: &ArrayString<A>) -> bool { self >= &**rhs }
+}
+
+impl<A> Ord for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn cmp(&self, rhs: &Self) -> cmp::Ordering {
+        (**self).cmp(&**rhs)
+    }
+}
+
+impl<A> FromStr for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    type Err = CapacityError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Self::from(s).map_err(CapacityError::simplify)
+    }
+}
+
+#[cfg(feature="serde")]
+/// Requires crate feature `"serde"`
+impl<A> Serialize for ArrayString<A>
+    where A: Array<Item=u8> + Copy
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.serialize_str(&*self)
+    }
+}
+
+#[cfg(feature="serde")]
+/// Requires crate feature `"serde"`
+impl<'de, A> Deserialize<'de> for ArrayString<A> 
+    where A: Array<Item=u8> + Copy
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        use serde::de::{self, Visitor};
+        use std::marker::PhantomData;
+
+        struct ArrayStringVisitor<A: Array<Item=u8>>(PhantomData<A>);
+
+        impl<'de, A: Copy + Array<Item=u8>> Visitor<'de> for ArrayStringVisitor<A> {
+            type Value = ArrayString<A>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                write!(formatter, "a string no more than {} bytes long", A::CAPACITY)
+            }
+
+            fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+                where E: de::Error,
+            {
+                ArrayString::from(v).map_err(|_| E::invalid_length(v.len(), &self))
+            }
+
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+                where E: de::Error,
+            {
+                let s = str::from_utf8(v).map_err(|_| E::invalid_value(de::Unexpected::Bytes(v), &self))?;
+
+                ArrayString::from(s).map_err(|_| E::invalid_length(s.len(), &self))
+            }
+        }
+
+        deserializer.deserialize_str(ArrayStringVisitor::<A>(PhantomData))
+    }
+}
diff --git a/third_party/rust/arrayvec/src/char.rs b/third_party/rust/arrayvec/src/char.rs
new file mode 100644
index 0000000000..c9b00ca967
--- /dev/null
+++ b/third_party/rust/arrayvec/src/char.rs
@@ -0,0 +1,98 @@
+// Copyright 2012-2016 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.
+//
+// Original authors: alexchrichton, bluss
+
+use std::ptr;
+
+// UTF-8 ranges and tags for encoding characters
+const TAG_CONT: u8    = 0b1000_0000;
+const TAG_TWO_B: u8   = 0b1100_0000;
+const TAG_THREE_B: u8 = 0b1110_0000;
+const TAG_FOUR_B: u8  = 0b1111_0000;
+const MAX_ONE_B: u32   =     0x80;
+const MAX_TWO_B: u32   =    0x800;
+const MAX_THREE_B: u32 =  0x10000;
+
+/// Placeholder
+pub struct EncodeUtf8Error;
+
+#[inline]
+unsafe fn write(ptr: *mut u8, index: usize, byte: u8) {
+    ptr::write(ptr.add(index), byte)
+}
+
+/// Encode a char into buf using UTF-8.
+///
+/// On success, return the byte length of the encoding (1, 2, 3 or 4).<br>
+/// On error, return `EncodeUtf8Error` if the buffer was too short for the char.
+///
+/// Safety: `ptr` must be writable for `len` bytes.
+#[inline]
+pub unsafe fn encode_utf8(ch: char, ptr: *mut u8, len: usize) -> Result<usize, EncodeUtf8Error>
+{
+    let code = ch as u32;
+    if code < MAX_ONE_B && len >= 1 {
+        write(ptr, 0, code as u8);
+        return Ok(1);
+    } else if code < MAX_TWO_B && len >= 2 {
+        write(ptr, 0, (code >> 6 & 0x1F) as u8 | TAG_TWO_B);
+        write(ptr, 1, (code & 0x3F) as u8 | TAG_CONT);
+        return Ok(2);
+    } else if code < MAX_THREE_B && len >= 3 {
+        write(ptr, 0, (code >> 12 & 0x0F) as u8 | TAG_THREE_B);
+        write(ptr, 1, (code >>  6 & 0x3F) as u8 | TAG_CONT);
+        write(ptr, 2, (code & 0x3F) as u8 | TAG_CONT);
+        return Ok(3);
+    } else if len >= 4 {
+        write(ptr, 0, (code >> 18 & 0x07) as u8 | TAG_FOUR_B);
+        write(ptr, 1, (code >> 12 & 0x3F) as u8 | TAG_CONT);
+        write(ptr, 2, (code >>  6 & 0x3F) as u8 | TAG_CONT);
+        write(ptr, 3, (code & 0x3F) as u8 | TAG_CONT);
+        return Ok(4);
+    };
+    Err(EncodeUtf8Error)
+}
+
+
+#[test]
+fn test_encode_utf8() {
+    // Test that all codepoints are encoded correctly
+    let mut data = [0u8; 16];
+    for codepoint in 0..=(std::char::MAX as u32) {
+        if let Some(ch) = std::char::from_u32(codepoint) {
+            for elt in &mut data { *elt = 0; }
+            let ptr = data.as_mut_ptr();
+            let len = data.len();
+            unsafe {
+                let res = encode_utf8(ch, ptr, len).ok().unwrap();
+                assert_eq!(res, ch.len_utf8());
+            }
+            let string = std::str::from_utf8(&data).unwrap();
+            assert_eq!(string.chars().next(), Some(ch));
+        }
+    }
+}
+
+#[test]
+fn test_encode_utf8_oob() {
+    // test that we report oob if the buffer is too short
+    let mut data = [0u8; 16];
+    let chars = ['a', 'α', '�', '𐍈'];
+    for (len, &ch) in (1..=4).zip(&chars) {
+        assert_eq!(len, ch.len_utf8(), "Len of ch={}", ch);
+        let ptr = data.as_mut_ptr();
+        unsafe {
+            assert!(matches::matches!(encode_utf8(ch, ptr, len - 1), Err(_)));
+            assert!(matches::matches!(encode_utf8(ch, ptr, len), Ok(_)));
+        }
+    }
+}
+
diff --git a/third_party/rust/arrayvec/src/errors.rs b/third_party/rust/arrayvec/src/errors.rs
new file mode 100644
index 0000000000..5bea98068f
--- /dev/null
+++ b/third_party/rust/arrayvec/src/errors.rs
@@ -0,0 +1,53 @@
+use std::fmt;
+#[cfg(feature="std")]
+use std::any::Any;
+#[cfg(feature="std")]
+use std::error::Error;
+
+/// Error value indicating insufficient capacity
+#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]
+pub struct CapacityError<T = ()> {
+    element: T,
+}
+
+impl<T> CapacityError<T> {
+    /// Create a new `CapacityError` from `element`.
+    pub fn new(element: T) -> CapacityError<T> {
+        CapacityError {
+            element: element,
+        }
+    }
+
+    /// Extract the overflowing element
+    pub fn element(self) -> T {
+        self.element
+    }
+
+    /// Convert into a `CapacityError` that does not carry an element.
+    pub fn simplify(self) -> CapacityError {
+        CapacityError { element: () }
+    }
+}
+
+const CAPERROR: &'static str = "insufficient capacity";
+
+#[cfg(feature="std")]
+/// Requires `features="std"`.
+impl<T: Any> Error for CapacityError<T> {
+    fn description(&self) -> &str {
+        CAPERROR
+    }
+}
+
+impl<T> fmt::Display for CapacityError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", CAPERROR)
+    }
+}
+
+impl<T> fmt::Debug for CapacityError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}: {}", "CapacityError", CAPERROR)
+    }
+}
+
diff --git a/third_party/rust/arrayvec/src/lib.rs b/third_party/rust/arrayvec/src/lib.rs
new file mode 100644
index 0000000000..0fea03faa4
--- /dev/null
+++ b/third_party/rust/arrayvec/src/lib.rs
@@ -0,0 +1,1156 @@
+//! **arrayvec** provides the types `ArrayVec` and `ArrayString`: 
+//! array-backed vector and string types, which store their contents inline.
+//!
+//! The arrayvec package has the following cargo features:
+//!
+//! - `std`
+//!   - Optional, enabled by default
+//!   - Use libstd; disable to use `no_std` instead.
+//!
+//! - `serde`
+//!   - Optional
+//!   - Enable serialization for ArrayVec and ArrayString using serde 1.x
+//! - `array-sizes-33-128`, `array-sizes-129-255`
+//!   - Optional
+//!   - Enable more array sizes (see [Array] for more information)
+//!
+//! ## Rust Version
+//!
+//! This version of arrayvec requires Rust 1.36 or later.
+//!
+#![doc(html_root_url="https://docs.rs/arrayvec/0.4/")]
+#![cfg_attr(not(feature="std"), no_std)]
+
+#[cfg(feature="serde")]
+extern crate serde;
+
+#[cfg(not(feature="std"))]
+extern crate core as std;
+
+use std::cmp;
+use std::iter;
+use std::mem;
+use std::ops::{Bound, Deref, DerefMut, RangeBounds};
+use std::ptr;
+use std::slice;
+
+// extra traits
+use std::borrow::{Borrow, BorrowMut};
+use std::hash::{Hash, Hasher};
+use std::fmt;
+
+#[cfg(feature="std")]
+use std::io;
+
+
+mod maybe_uninit;
+use crate::maybe_uninit::MaybeUninit;
+
+#[cfg(feature="serde")]
+use serde::{Serialize, Deserialize, Serializer, Deserializer};
+
+mod array;
+mod array_string;
+mod char;
+mod errors;
+
+pub use crate::array::Array;
+use crate::array::Index;
+pub use crate::array_string::ArrayString;
+pub use crate::errors::CapacityError;
+
+
+/// A vector with a fixed capacity.
+///
+/// The `ArrayVec` is a vector backed by a fixed size array. It keeps track of
+/// the number of initialized elements.
+///
+/// The vector is a contiguous value that you can store directly on the stack
+/// if needed.
+///
+/// It offers a simple API but also dereferences to a slice, so
+/// that the full slice API is available.
+///
+/// ArrayVec can be converted into a by value iterator.
+pub struct ArrayVec<A: Array> {
+    xs: MaybeUninit<A>,
+    len: A::Index,
+}
+
+impl<A: Array> Drop for ArrayVec<A> {
+    fn drop(&mut self) {
+        self.clear();
+
+        // NoDrop inhibits array's drop
+        // panic safety: NoDrop::drop will trigger on panic, so the inner
+        // array will not drop even after panic.
+    }
+}
+
+macro_rules! panic_oob {
+    ($method_name:expr, $index:expr, $len:expr) => {
+        panic!(concat!("ArrayVec::", $method_name, ": index {} is out of bounds in vector of length {}"),
+               $index, $len)
+    }
+}
+
+impl<A: Array> ArrayVec<A> {
+    /// Create a new empty `ArrayVec`.
+    ///
+    /// Capacity is inferred from the type parameter.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 16]>::new();
+    /// array.push(1);
+    /// array.push(2);
+    /// assert_eq!(&array[..], &[1, 2]);
+    /// assert_eq!(array.capacity(), 16);
+    /// ```
+    pub fn new() -> ArrayVec<A> {
+        unsafe {
+            ArrayVec { xs: MaybeUninit::uninitialized(), len: Index::from(0) }
+        }
+    }
+
+    /// Return the number of elements in the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    /// array.pop();
+    /// assert_eq!(array.len(), 2);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize { self.len.to_usize() }
+
+    /// Return the capacity of the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let array = ArrayVec::from([1, 2, 3]);
+    /// assert_eq!(array.capacity(), 3);
+    /// ```
+    #[inline(always)]
+    pub fn capacity(&self) -> usize { A::CAPACITY }
+
+    /// Return if the `ArrayVec` is completely filled.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 1]>::new();
+    /// assert!(!array.is_full());
+    /// array.push(1);
+    /// assert!(array.is_full());
+    /// ```
+    pub fn is_full(&self) -> bool { self.len() == self.capacity() }
+
+    /// Returns the capacity left in the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    /// array.pop();
+    /// assert_eq!(array.remaining_capacity(), 1);
+    /// ```
+    pub fn remaining_capacity(&self) -> usize {
+        self.capacity() - self.len()
+    }
+
+    /// Push `element` to the end of the vector.
+    ///
+    /// ***Panics*** if the vector is already full.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// array.push(1);
+    /// array.push(2);
+    ///
+    /// assert_eq!(&array[..], &[1, 2]);
+    /// ```
+    pub fn push(&mut self, element: A::Item) {
+        self.try_push(element).unwrap()
+    }
+
+    /// Push `element` to the end of the vector.
+    ///
+    /// Return `Ok` if the push succeeds, or return an error if the vector
+    /// is already full.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// let push1 = array.try_push(1);
+    /// let push2 = array.try_push(2);
+    ///
+    /// assert!(push1.is_ok());
+    /// assert!(push2.is_ok());
+    ///
+    /// assert_eq!(&array[..], &[1, 2]);
+    ///
+    /// let overflow = array.try_push(3);
+    ///
+    /// assert!(overflow.is_err());
+    /// ```
+    pub fn try_push(&mut self, element: A::Item) -> Result<(), CapacityError<A::Item>> {
+        if self.len() < A::CAPACITY {
+            unsafe {
+                self.push_unchecked(element);
+            }
+            Ok(())
+        } else {
+            Err(CapacityError::new(element))
+        }
+    }
+
+
+    /// Push `element` to the end of the vector without checking the capacity.
+    ///
+    /// It is up to the caller to ensure the capacity of the vector is
+    /// sufficiently large.
+    ///
+    /// This method uses *debug assertions* to check that the arrayvec is not full.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// if array.len() + 2 <= array.capacity() {
+    ///     unsafe {
+    ///         array.push_unchecked(1);
+    ///         array.push_unchecked(2);
+    ///     }
+    /// }
+    ///
+    /// assert_eq!(&array[..], &[1, 2]);
+    /// ```
+    pub unsafe fn push_unchecked(&mut self, element: A::Item) {
+        let len = self.len();
+        debug_assert!(len < A::CAPACITY);
+        ptr::write(self.get_unchecked_ptr(len), element);
+        self.set_len(len + 1);
+    }
+
+    /// Get pointer to where element at `index` would be
+    unsafe fn get_unchecked_ptr(&mut self, index: usize) -> *mut A::Item {
+        self.xs.ptr_mut().add(index)
+    }
+
+    /// Insert `element` at position `index`.
+    ///
+    /// Shift up all elements after `index`.
+    ///
+    /// It is an error if the index is greater than the length or if the
+    /// arrayvec is full.
+    ///
+    /// ***Panics*** if the array is full or the `index` is out of bounds. See
+    /// `try_insert` for fallible version.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// array.insert(0, "x");
+    /// array.insert(0, "y");
+    /// assert_eq!(&array[..], &["y", "x"]);
+    ///
+    /// ```
+    pub fn insert(&mut self, index: usize, element: A::Item) {
+        self.try_insert(index, element).unwrap()
+    }
+
+    /// Insert `element` at position `index`.
+    ///
+    /// Shift up all elements after `index`; the `index` must be less than
+    /// or equal to the length.
+    ///
+    /// Returns an error if vector is already at full capacity.
+    ///
+    /// ***Panics*** `index` is out of bounds.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// assert!(array.try_insert(0, "x").is_ok());
+    /// assert!(array.try_insert(0, "y").is_ok());
+    /// assert!(array.try_insert(0, "z").is_err());
+    /// assert_eq!(&array[..], &["y", "x"]);
+    ///
+    /// ```
+    pub fn try_insert(&mut self, index: usize, element: A::Item) -> Result<(), CapacityError<A::Item>> {
+        if index > self.len() {
+            panic_oob!("try_insert", index, self.len())
+        }
+        if self.len() == self.capacity() {
+            return Err(CapacityError::new(element));
+        }
+        let len = self.len();
+
+        // follows is just like Vec<T>
+        unsafe { // infallible
+            // The spot to put the new value
+            {
+                let p: *mut _ = self.get_unchecked_ptr(index);
+                // Shift everything over to make space. (Duplicating the
+                // `index`th element into two consecutive places.)
+                ptr::copy(p, p.offset(1), len - index);
+                // Write it in, overwriting the first copy of the `index`th
+                // element.
+                ptr::write(p, element);
+            }
+            self.set_len(len + 1);
+        }
+        Ok(())
+    }
+
+    /// Remove the last element in the vector and return it.
+    ///
+    /// Return `Some(` *element* `)` if the vector is non-empty, else `None`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::<[_; 2]>::new();
+    ///
+    /// array.push(1);
+    ///
+    /// assert_eq!(array.pop(), Some(1));
+    /// assert_eq!(array.pop(), None);
+    /// ```
+    pub fn pop(&mut self) -> Option<A::Item> {
+        if self.len() == 0 {
+            return None;
+        }
+        unsafe {
+            let new_len = self.len() - 1;
+            self.set_len(new_len);
+            Some(ptr::read(self.get_unchecked_ptr(new_len)))
+        }
+    }
+
+    /// Remove the element at `index` and swap the last element into its place.
+    ///
+    /// This operation is O(1).
+    ///
+    /// Return the *element* if the index is in bounds, else panic.
+    ///
+    /// ***Panics*** if the `index` is out of bounds.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    ///
+    /// assert_eq!(array.swap_remove(0), 1);
+    /// assert_eq!(&array[..], &[3, 2]);
+    ///
+    /// assert_eq!(array.swap_remove(1), 2);
+    /// assert_eq!(&array[..], &[3]);
+    /// ```
+    pub fn swap_remove(&mut self, index: usize) -> A::Item {
+        self.swap_pop(index)
+            .unwrap_or_else(|| {
+                panic_oob!("swap_remove", index, self.len())
+            })
+    }
+
+    /// Remove the element at `index` and swap the last element into its place.
+    ///
+    /// This is a checked version of `.swap_remove`.  
+    /// This operation is O(1).
+    ///
+    /// Return `Some(` *element* `)` if the index is in bounds, else `None`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    ///
+    /// assert_eq!(array.swap_pop(0), Some(1));
+    /// assert_eq!(&array[..], &[3, 2]);
+    ///
+    /// assert_eq!(array.swap_pop(10), None);
+    /// ```
+    pub fn swap_pop(&mut self, index: usize) -> Option<A::Item> {
+        let len = self.len();
+        if index >= len {
+            return None;
+        }
+        self.swap(index, len - 1);
+        self.pop()
+    }
+
+    /// Remove the element at `index` and shift down the following elements.
+    ///
+    /// The `index` must be strictly less than the length of the vector.
+    ///
+    /// ***Panics*** if the `index` is out of bounds.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    ///
+    /// let removed_elt = array.remove(0);
+    /// assert_eq!(removed_elt, 1);
+    /// assert_eq!(&array[..], &[2, 3]);
+    /// ```
+    pub fn remove(&mut self, index: usize) -> A::Item {
+        self.pop_at(index)
+            .unwrap_or_else(|| {
+                panic_oob!("remove", index, self.len())
+            })
+    }
+
+    /// Remove the element at `index` and shift down the following elements.
+    ///
+    /// This is a checked version of `.remove(index)`. Returns `None` if there
+    /// is no element at `index`. Otherwise, return the element inside `Some`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3]);
+    ///
+    /// assert!(array.pop_at(0).is_some());
+    /// assert_eq!(&array[..], &[2, 3]);
+    ///
+    /// assert!(array.pop_at(2).is_none());
+    /// assert!(array.pop_at(10).is_none());
+    /// ```
+    pub fn pop_at(&mut self, index: usize) -> Option<A::Item> {
+        if index >= self.len() {
+            None
+        } else {
+            self.drain(index..index + 1).next()
+        }
+    }
+
+    /// Shortens the vector, keeping the first `len` elements and dropping
+    /// the rest.
+    ///
+    /// If `len` is greater than the vector’s current length this has no
+    /// effect.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3, 4, 5]);
+    /// array.truncate(3);
+    /// assert_eq!(&array[..], &[1, 2, 3]);
+    /// array.truncate(4);
+    /// assert_eq!(&array[..], &[1, 2, 3]);
+    /// ```
+    pub fn truncate(&mut self, new_len: usize) {
+        unsafe {
+            if new_len < self.len() {
+                let tail: *mut [_] = &mut self[new_len..];
+                self.len = Index::from(new_len);
+                ptr::drop_in_place(tail);
+            }
+        }
+    }
+
+    /// Remove all elements in the vector.
+    pub fn clear(&mut self) {
+        self.truncate(0)
+    }
+
+    /// Retains only the elements specified by the predicate.
+    ///
+    /// In other words, remove all elements `e` such that `f(&mut e)` returns false.
+    /// This method operates in place and preserves the order of the retained
+    /// elements.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut array = ArrayVec::from([1, 2, 3, 4]);
+    /// array.retain(|x| *x & 1 != 0 );
+    /// assert_eq!(&array[..], &[1, 3]);
+    /// ```
+    pub fn retain<F>(&mut self, mut f: F)
+        where F: FnMut(&mut A::Item) -> bool
+    {
+        let len = self.len();
+        let mut del = 0;
+        {
+            let v = &mut **self;
+
+            for i in 0..len {
+                if !f(&mut v[i]) {
+                    del += 1;
+                } else if del > 0 {
+                    v.swap(i - del, i);
+                }
+            }
+        }
+        if del > 0 {
+            self.drain(len - del..);
+        }
+    }
+
+    /// Set the vector’s length without dropping or moving out elements
+    ///
+    /// This method is `unsafe` because it changes the notion of the
+    /// number of “valid” elements in the vector. Use with care.
+    ///
+    /// This method uses *debug assertions* to check that `length` is
+    /// not greater than the capacity.
+    pub unsafe fn set_len(&mut self, length: usize) {
+        debug_assert!(length <= self.capacity());
+        self.len = Index::from(length);
+    }
+
+    /// Copy and appends all elements in a slice to the `ArrayVec`.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut vec: ArrayVec<[usize; 10]> = ArrayVec::new();
+    /// vec.push(1);
+    /// vec.try_extend_from_slice(&[2, 3]).unwrap();
+    /// assert_eq!(&vec[..], &[1, 2, 3]);
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// This method will return an error if the capacity left (see
+    /// [`remaining_capacity`]) is smaller then the length of the provided
+    /// slice.
+    ///
+    /// [`remaining_capacity`]: #method.remaining_capacity
+    pub fn try_extend_from_slice(&mut self, other: &[A::Item]) -> Result<(), CapacityError>
+        where A::Item: Copy,
+    {
+        if self.remaining_capacity() < other.len() {
+            return Err(CapacityError::new(()));
+        }
+
+        let self_len = self.len();
+        let other_len = other.len();
+
+        unsafe {
+            let dst = self.xs.ptr_mut().offset(self_len as isize);
+            ptr::copy_nonoverlapping(other.as_ptr(), dst, other_len);
+            self.set_len(self_len + other_len);
+        }
+        Ok(())
+    }
+
+    /// Create a draining iterator that removes the specified range in the vector
+    /// and yields the removed items from start to end. The element range is
+    /// removed even if the iterator is not consumed until the end.
+    ///
+    /// Note: It is unspecified how many elements are removed from the vector,
+    /// if the `Drain` value is leaked.
+    ///
+    /// **Panics** if the starting point is greater than the end point or if
+    /// the end point is greater than the length of the vector.
+    ///
+    /// ```
+    /// use arrayvec::ArrayVec;
+    ///
+    /// let mut v = ArrayVec::from([1, 2, 3]);
+    /// let u: ArrayVec<[_; 3]> = v.drain(0..2).collect();
+    /// assert_eq!(&v[..], &[3]);
+    /// assert_eq!(&u[..], &[1, 2]);
+    /// ```
+    pub fn drain<R>(&mut self, range: R) -> Drain<A>
+        where R: RangeBounds<usize>
+    {
+        // Memory safety
+        //
+        // When the Drain is first created, it shortens the length of
+        // the source vector to make sure no uninitialized or moved-from elements
+        // are accessible at all if the Drain's destructor never gets to run.
+        //
+        // Drain will ptr::read out the values to remove.
+        // When finished, remaining tail of the vec is copied back to cover
+        // the hole, and the vector length is restored to the new length.
+        //
+        let len = self.len();
+        let start = match range.start_bound() {
+            Bound::Unbounded => 0,
+            Bound::Included(&i) => i,
+            Bound::Excluded(&i) => i.saturating_add(1),
+        };
+        let end = match range.end_bound() {
+            Bound::Excluded(&j) => j,
+            Bound::Included(&j) => j.saturating_add(1),
+            Bound::Unbounded => len,
+        };
+        self.drain_range(start, end)
+    }
+
+    fn drain_range(&mut self, start: usize, end: usize) -> Drain<A>
+    {
+        let len = self.len();
+        // bounds check happens here
+        let range_slice: *const _ = &self[start..end];
+
+        unsafe {
+            // set self.vec length's to start, to be safe in case Drain is leaked
+            self.set_len(start);
+            Drain {
+                tail_start: end,
+                tail_len: len - end,
+                iter: (*range_slice).iter(),
+                vec: self as *mut _,
+            }
+        }
+    }
+
+    /// Return the inner fixed size array, if it is full to its capacity.
+    ///
+    /// Return an `Ok` value with the array if length equals capacity,
+    /// return an `Err` with self otherwise.
+    pub fn into_inner(self) -> Result<A, Self> {
+        if self.len() < self.capacity() {
+            Err(self)
+        } else {
+            unsafe {
+                let array = ptr::read(self.xs.ptr() as *const A);
+                mem::forget(self);
+                Ok(array)
+            }
+        }
+    }
+
+    /// Dispose of `self` (same as drop)
+    #[deprecated="Use std::mem::drop instead, if at all needed."]
+    pub fn dispose(mut self) {
+        self.clear();
+        mem::forget(self);
+    }
+
+    /// Return a slice containing all elements of the vector.
+    pub fn as_slice(&self) -> &[A::Item] {
+        self
+    }
+
+    /// Return a mutable slice containing all elements of the vector.
+    pub fn as_mut_slice(&mut self) -> &mut [A::Item] {
+        self
+    }
+
+    /// Return a raw pointer to the vector's buffer.
+    pub fn as_ptr(&self) -> *const A::Item {
+        self.xs.ptr()
+    }
+
+    /// Return a raw mutable pointer to the vector's buffer.
+    pub fn as_mut_ptr(&mut self) -> *mut A::Item {
+        self.xs.ptr_mut()
+    }
+}
+
+impl<A: Array> Deref for ArrayVec<A> {
+    type Target = [A::Item];
+    #[inline]
+    fn deref(&self) -> &[A::Item] {
+        unsafe {
+            slice::from_raw_parts(self.xs.ptr(), self.len())
+        }
+    }
+}
+
+impl<A: Array> DerefMut for ArrayVec<A> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut [A::Item] {
+        let len = self.len();
+        unsafe {
+            slice::from_raw_parts_mut(self.xs.ptr_mut(), len)
+        }
+    }
+}
+
+/// Create an `ArrayVec` from an array.
+///
+/// ```
+/// use arrayvec::ArrayVec;
+///
+/// let mut array = ArrayVec::from([1, 2, 3]);
+/// assert_eq!(array.len(), 3);
+/// assert_eq!(array.capacity(), 3);
+/// ```
+impl<A: Array> From<A> for ArrayVec<A> {
+    fn from(array: A) -> Self {
+        ArrayVec { xs: MaybeUninit::from(array), len: Index::from(A::CAPACITY) }
+    }
+}
+
+
+/// Iterate the `ArrayVec` with references to each element.
+///
+/// ```
+/// use arrayvec::ArrayVec;
+///
+/// let array = ArrayVec::from([1, 2, 3]);
+///
+/// for elt in &array {
+///     // ...
+/// }
+/// ```
+impl<'a, A: Array> IntoIterator for &'a ArrayVec<A> {
+    type Item = &'a A::Item;
+    type IntoIter = slice::Iter<'a, A::Item>;
+    fn into_iter(self) -> Self::IntoIter { self.iter() }
+}
+
+/// Iterate the `ArrayVec` with mutable references to each element.
+///
+/// ```
+/// use arrayvec::ArrayVec;
+///
+/// let mut array = ArrayVec::from([1, 2, 3]);
+///
+/// for elt in &mut array {
+///     // ...
+/// }
+/// ```
+impl<'a, A: Array> IntoIterator for &'a mut ArrayVec<A> {
+    type Item = &'a mut A::Item;
+    type IntoIter = slice::IterMut<'a, A::Item>;
+    fn into_iter(self) -> Self::IntoIter { self.iter_mut() }
+}
+
+/// Iterate the `ArrayVec` with each element by value.
+///
+/// The vector is consumed by this operation.
+///
+/// ```
+/// use arrayvec::ArrayVec;
+///
+/// for elt in ArrayVec::from([1, 2, 3]) {
+///     // ...
+/// }
+/// ```
+impl<A: Array> IntoIterator for ArrayVec<A> {
+    type Item = A::Item;
+    type IntoIter = IntoIter<A>;
+    fn into_iter(self) -> IntoIter<A> {
+        IntoIter { index: Index::from(0), v: self, }
+    }
+}
+
+
+/// By-value iterator for `ArrayVec`.
+pub struct IntoIter<A: Array> {
+    index: A::Index,
+    v: ArrayVec<A>,
+}
+
+impl<A: Array> Iterator for IntoIter<A> {
+    type Item = A::Item;
+
+    fn next(&mut self) -> Option<A::Item> {
+        if self.index == self.v.len {
+            None
+        } else {
+            unsafe {
+                let index = self.index.to_usize();
+                self.index = Index::from(index + 1);
+                Some(ptr::read(self.v.get_unchecked_ptr(index)))
+            }
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.v.len() - self.index.to_usize();
+        (len, Some(len))
+    }
+}
+
+impl<A: Array> DoubleEndedIterator for IntoIter<A> {
+    fn next_back(&mut self) -> Option<A::Item> {
+        if self.index == self.v.len {
+            None
+        } else {
+            unsafe {
+                let new_len = self.v.len() - 1;
+                self.v.set_len(new_len);
+                Some(ptr::read(self.v.get_unchecked_ptr(new_len)))
+            }
+        }
+    }
+}
+
+impl<A: Array> ExactSizeIterator for IntoIter<A> { }
+
+impl<A: Array> Drop for IntoIter<A> {
+    fn drop(&mut self) {
+        // panic safety: Set length to 0 before dropping elements.
+        let index = self.index.to_usize();
+        let len = self.v.len();
+        unsafe {
+            self.v.set_len(0);
+            let elements = slice::from_raw_parts_mut(
+                self.v.get_unchecked_ptr(index),
+                len - index);
+            ptr::drop_in_place(elements);
+        }
+    }
+}
+
+impl<A: Array> Clone for IntoIter<A>
+where
+    A::Item: Clone,
+{
+    fn clone(&self) -> IntoIter<A> {
+        self.v[self.index.to_usize()..]
+            .iter()
+            .cloned()
+            .collect::<ArrayVec<A>>()
+            .into_iter()
+    }
+}
+
+impl<A: Array> fmt::Debug for IntoIter<A>
+where
+    A::Item: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(&self.v[self.index.to_usize()..])
+            .finish()
+    }
+}
+
+/// A draining iterator for `ArrayVec`.
+pub struct Drain<'a, A> 
+    where A: Array,
+          A::Item: 'a,
+{
+    /// Index of tail to preserve
+    tail_start: usize,
+    /// Length of tail
+    tail_len: usize,
+    /// Current remaining range to remove
+    iter: slice::Iter<'a, A::Item>,
+    vec: *mut ArrayVec<A>,
+}
+
+unsafe impl<'a, A: Array + Sync> Sync for Drain<'a, A> {}
+unsafe impl<'a, A: Array + Send> Send for Drain<'a, A> {}
+
+impl<'a, A: Array> Iterator for Drain<'a, A>
+    where A::Item: 'a,
+{
+    type Item = A::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next().map(|elt|
+            unsafe {
+                ptr::read(elt as *const _)
+            }
+        )
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a, A: Array> DoubleEndedIterator for Drain<'a, A>
+    where A::Item: 'a,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter.next_back().map(|elt|
+            unsafe {
+                ptr::read(elt as *const _)
+            }
+        )
+    }
+}
+
+impl<'a, A: Array> ExactSizeIterator for Drain<'a, A> where A::Item: 'a {}
+
+impl<'a, A: Array> Drop for Drain<'a, A> 
+    where A::Item: 'a
+{
+    fn drop(&mut self) {
+        // len is currently 0 so panicking while dropping will not cause a double drop.
+
+        // exhaust self first
+        while let Some(_) = self.next() { }
+
+        if self.tail_len > 0 {
+            unsafe {
+                let source_vec = &mut *self.vec;
+                // memmove back untouched tail, update to new length
+                let start = source_vec.len();
+                let tail = self.tail_start;
+                let src = source_vec.as_ptr().offset(tail as isize);
+                let dst = source_vec.as_mut_ptr().offset(start as isize);
+                ptr::copy(src, dst, self.tail_len);
+                source_vec.set_len(start + self.tail_len);
+            }
+        }
+    }
+}
+
+struct ScopeExitGuard<T, Data, F>
+    where F: FnMut(&Data, &mut T)
+{
+    value: T,
+    data: Data,
+    f: F,
+}
+
+impl<T, Data, F> Drop for ScopeExitGuard<T, Data, F>
+    where F: FnMut(&Data, &mut T)
+{
+    fn drop(&mut self) {
+        (self.f)(&self.data, &mut self.value)
+    }
+}
+
+
+
+/// Extend the `ArrayVec` with an iterator.
+/// 
+/// Does not extract more items than there is space for. No error
+/// occurs if there are more iterator elements.
+impl<A: Array> Extend<A::Item> for ArrayVec<A> {
+    fn extend<T: IntoIterator<Item=A::Item>>(&mut self, iter: T) {
+        let take = self.capacity() - self.len();
+        unsafe {
+            let len = self.len();
+            let mut ptr = raw_ptr_add(self.as_mut_ptr(), len);
+            let end_ptr = raw_ptr_add(ptr, take);
+            // Keep the length in a separate variable, write it back on scope
+            // exit. To help the compiler with alias analysis and stuff.
+            // We update the length to handle panic in the iteration of the
+            // user's iterator, without dropping any elements on the floor.
+            let mut guard = ScopeExitGuard {
+                value: &mut self.len,
+                data: len,
+                f: move |&len, self_len| {
+                    **self_len = Index::from(len);
+                }
+            };
+            let mut iter = iter.into_iter();
+            loop {
+                if ptr == end_ptr { break; }
+                if let Some(elt) = iter.next() {
+                    raw_ptr_write(ptr, elt);
+                    ptr = raw_ptr_add(ptr, 1);
+                    guard.data += 1;
+                } else {
+                    break;
+                }
+            }
+        }
+    }
+}
+
+/// Rawptr add but uses arithmetic distance for ZST
+unsafe fn raw_ptr_add<T>(ptr: *mut T, offset: usize) -> *mut T {
+    if mem::size_of::<T>() == 0 {
+        // Special case for ZST
+        (ptr as usize).wrapping_add(offset) as _
+    } else {
+        ptr.offset(offset as isize)
+    }
+}
+
+unsafe fn raw_ptr_write<T>(ptr: *mut T, value: T) {
+    if mem::size_of::<T>() == 0 {
+        /* nothing */
+    } else {
+        ptr::write(ptr, value)
+    }
+}
+
+/// Create an `ArrayVec` from an iterator.
+/// 
+/// Does not extract more items than there is space for. No error
+/// occurs if there are more iterator elements.
+impl<A: Array> iter::FromIterator<A::Item> for ArrayVec<A> {
+    fn from_iter<T: IntoIterator<Item=A::Item>>(iter: T) -> Self {
+        let mut array = ArrayVec::new();
+        array.extend(iter);
+        array
+    }
+}
+
+impl<A: Array> Clone for ArrayVec<A>
+    where A::Item: Clone
+{
+    fn clone(&self) -> Self {
+        self.iter().cloned().collect()
+    }
+
+    fn clone_from(&mut self, rhs: &Self) {
+        // recursive case for the common prefix
+        let prefix = cmp::min(self.len(), rhs.len());
+        self[..prefix].clone_from_slice(&rhs[..prefix]);
+
+        if prefix < self.len() {
+            // rhs was shorter
+            for _ in 0..self.len() - prefix {
+                self.pop();
+            }
+        } else {
+            let rhs_elems = rhs[self.len()..].iter().cloned();
+            self.extend(rhs_elems);
+        }
+    }
+}
+
+impl<A: Array> Hash for ArrayVec<A>
+    where A::Item: Hash
+{
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Hash::hash(&**self, state)
+    }
+}
+
+impl<A: Array> PartialEq for ArrayVec<A>
+    where A::Item: PartialEq
+{
+    fn eq(&self, other: &Self) -> bool {
+        **self == **other
+    }
+}
+
+impl<A: Array> PartialEq<[A::Item]> for ArrayVec<A>
+    where A::Item: PartialEq
+{
+    fn eq(&self, other: &[A::Item]) -> bool {
+        **self == *other
+    }
+}
+
+impl<A: Array> Eq for ArrayVec<A> where A::Item: Eq { }
+
+impl<A: Array> Borrow<[A::Item]> for ArrayVec<A> {
+    fn borrow(&self) -> &[A::Item] { self }
+}
+
+impl<A: Array> BorrowMut<[A::Item]> for ArrayVec<A> {
+    fn borrow_mut(&mut self) -> &mut [A::Item] { self }
+}
+
+impl<A: Array> AsRef<[A::Item]> for ArrayVec<A> {
+    fn as_ref(&self) -> &[A::Item] { self }
+}
+
+impl<A: Array> AsMut<[A::Item]> for ArrayVec<A> {
+    fn as_mut(&mut self) -> &mut [A::Item] { self }
+}
+
+impl<A: Array> fmt::Debug for ArrayVec<A> where A::Item: fmt::Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { (**self).fmt(f) }
+}
+
+impl<A: Array> Default for ArrayVec<A> {
+    /// Return an empty array
+    fn default() -> ArrayVec<A> {
+        ArrayVec::new()
+    }
+}
+
+impl<A: Array> PartialOrd for ArrayVec<A> where A::Item: PartialOrd {
+    fn partial_cmp(&self, other: &ArrayVec<A>) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(other)
+    }
+
+    fn lt(&self, other: &Self) -> bool {
+        (**self).lt(other)
+    }
+
+    fn le(&self, other: &Self) -> bool {
+        (**self).le(other)
+    }
+
+    fn ge(&self, other: &Self) -> bool {
+        (**self).ge(other)
+    }
+
+    fn gt(&self, other: &Self) -> bool {
+        (**self).gt(other)
+    }
+}
+
+impl<A: Array> Ord for ArrayVec<A> where A::Item: Ord {
+    fn cmp(&self, other: &ArrayVec<A>) -> cmp::Ordering {
+        (**self).cmp(other)
+    }
+}
+
+#[cfg(feature="std")]
+/// `Write` appends written data to the end of the vector.
+///
+/// Requires `features="std"`.
+impl<A: Array<Item=u8>> io::Write for ArrayVec<A> {
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        let len = cmp::min(self.remaining_capacity(), data.len());
+        let _result = self.try_extend_from_slice(&data[..len]);
+        debug_assert!(_result.is_ok());
+        Ok(len)
+    }
+    fn flush(&mut self) -> io::Result<()> { Ok(()) }
+}
+
+#[cfg(feature="serde")]
+/// Requires crate feature `"serde"`
+impl<T: Serialize, A: Array<Item=T>> Serialize for ArrayVec<A> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        serializer.collect_seq(self)
+    }
+}
+
+#[cfg(feature="serde")]
+/// Requires crate feature `"serde"`
+impl<'de, T: Deserialize<'de>, A: Array<Item=T>> Deserialize<'de> for ArrayVec<A> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        use serde::de::{Visitor, SeqAccess, Error};
+        use std::marker::PhantomData;
+
+        struct ArrayVecVisitor<'de, T: Deserialize<'de>, A: Array<Item=T>>(PhantomData<(&'de (), T, A)>);
+
+        impl<'de, T: Deserialize<'de>, A: Array<Item=T>> Visitor<'de> for ArrayVecVisitor<'de, T, A> {
+            type Value = ArrayVec<A>;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                write!(formatter, "an array with no more than {} items", A::CAPACITY)
+            }
+
+            fn visit_seq<SA>(self, mut seq: SA) -> Result<Self::Value, SA::Error>
+                where SA: SeqAccess<'de>,
+            {
+                let mut values = ArrayVec::<A>::new();
+
+                while let Some(value) = seq.next_element()? {
+                    if let Err(_) = values.try_push(value) {
+                        return Err(SA::Error::invalid_length(A::CAPACITY + 1, &self));
+                    }
+                }
+
+                Ok(values)
+            }
+        }
+
+        deserializer.deserialize_seq(ArrayVecVisitor::<T, A>(PhantomData))
+    }
+}
diff --git a/third_party/rust/arrayvec/src/maybe_uninit.rs b/third_party/rust/arrayvec/src/maybe_uninit.rs
new file mode 100644
index 0000000000..fc69a3f801
--- /dev/null
+++ b/third_party/rust/arrayvec/src/maybe_uninit.rs
@@ -0,0 +1,44 @@
+
+
+use crate::array::Array;
+use std::mem::MaybeUninit as StdMaybeUninit;
+
+#[derive(Copy)]
+pub struct MaybeUninit<T> {
+    inner: StdMaybeUninit<T>,
+}
+
+impl<T> Clone for MaybeUninit<T>
+    where T: Copy
+{
+    fn clone(&self) -> Self { *self }
+}
+
+impl<T> MaybeUninit<T> {
+    /// Create a new MaybeUninit with uninitialized interior
+    pub unsafe fn uninitialized() -> Self {
+        MaybeUninit { inner: StdMaybeUninit::uninit() }
+    }
+
+    /// Create a new MaybeUninit from the value `v`.
+    pub fn from(v: T) -> Self {
+        MaybeUninit { inner: StdMaybeUninit::new(v) }
+    }
+
+    // Raw pointer casts written so that we don't reference or access the
+    // uninitialized interior value
+
+    /// Return a raw pointer to the start of the interior array
+    pub fn ptr(&self) -> *const T::Item
+        where T: Array
+    {
+        self.inner.as_ptr() as *const T::Item
+    }
+
+    /// Return a mut raw pointer to the start of the interior array
+    pub fn ptr_mut(&mut self) -> *mut T::Item
+        where T: Array
+    {
+        self.inner.as_mut_ptr() as *mut T::Item
+    }
+}