src/librustc_data_structures/indexed_vec.rs - third_party/rust - Git at Google

 use rustc_serialize::{Encodable, Decodable, Encoder, Decoder};

 use std::fmt::Debug;
 use std::iter::{self, FromIterator};
 use std::slice;
 use std::marker::PhantomData;
 use std::ops::{Index, IndexMut, Range, RangeBounds};
 use std::fmt;
 use std::hash::Hash;
 use std::vec;
 use std::u32;

 /// Represents some newtyped `usize` wrapper.
 ///
 /// Purpose: avoid mixing indexes for different bitvector domains.
 pub trait Idx: Copy + 'static + Ord + Debug + Hash {
     fn new(idx: usize) -> Self;

     fn index(self) -> usize;

     fn increment_by(&mut self, amount: usize) {
         *self = self.plus(amount);
     }

     fn plus(self, amount: usize) -> Self {
         Self::new(self.index() + amount)
     }
 }

 impl Idx for usize {
     #[inline]
     fn new(idx: usize) -> Self { idx }
     #[inline]
     fn index(self) -> usize { self }
 }

 impl Idx for u32 {
     #[inline]
     fn new(idx: usize) -> Self { assert!(idx <= u32::MAX as usize); idx as u32 }
     #[inline]
     fn index(self) -> usize { self as usize }
 }

 /// Creates a struct type `S` that can be used as an index with
 /// `IndexVec` and so on.
 ///
 /// There are two ways of interacting with these indices:
 ///
 /// - The `From` impls are the preferred way. So you can do
 ///   `S::from(v)` with a `usize` or `u32`. And you can convert back
 ///   to an integer with `u32::from(s)`.
 ///
 /// - Alternatively, you can use the methods `S::new(v)` and `s.index()`
 ///   to create/return a value.
 ///
 /// Internally, the index uses a u32, so the index must not exceed
 /// `u32::MAX`. You can also customize things like the `Debug` impl,
 /// what traits are derived, and so forth via the macro.
 #[macro_export]
 #[allow_internal_unstable(step_trait, rustc_attrs)]
 macro_rules! newtype_index {
     // ---- public rules ----

     // Use default constants
     ($(#[$attrs:meta])* $v:vis struct $name:ident { .. }) => (
         $crate::newtype_index!(
             // Leave out derives marker so we can use its absence to ensure it comes first
             @attrs        [$(#[$attrs])*]
             @type         [$name]
             // shave off 256 indices at the end to allow space for packing these indices into enums
             @max          [0xFFFF_FF00]
             @vis          [$v]
             @debug_format ["{}"]);
     );

     // Define any constants
     ($(#[$attrs:meta])* $v:vis struct $name:ident { $($tokens:tt)+ }) => (
         $crate::newtype_index!(
             // Leave out derives marker so we can use its absence to ensure it comes first
             @attrs        [$(#[$attrs])*]
             @type         [$name]
             // shave off 256 indices at the end to allow space for packing these indices into enums
             @max          [0xFFFF_FF00]
             @vis          [$v]
             @debug_format ["{}"]
                           $($tokens)+);
     );

     // ---- private rules ----

     // Base case, user-defined constants (if any) have already been defined
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]) => (
         $(#[$attrs])*
         #[derive(Copy, PartialEq, Eq, Hash, PartialOrd, Ord, $($derives),*)]
         #[rustc_layout_scalar_valid_range_end($max)]
         $v struct $type {
             private: u32
         }

         impl Clone for $type {
             fn clone(&self) -> Self {
                 *self
             }
         }

         impl $type {
             $v const MAX_AS_U32: u32 = $max;

             $v const MAX: $type = $type::from_u32_const($max);

             #[inline]
             $v fn from_usize(value: usize) -> Self {
                 assert!(value <= ($max as usize));
                 unsafe {
                     $type::from_u32_unchecked(value as u32)
                 }
             }

             #[inline]
             $v fn from_u32(value: u32) -> Self {
                 assert!(value <= $max);
                 unsafe {
                     $type::from_u32_unchecked(value)
                 }
             }

             /// Hacky variant of `from_u32` for use in constants.
             /// This version checks the "max" constraint by using an
             /// invalid array dereference.
             #[inline]
             $v const fn from_u32_const(value: u32) -> Self {
                 // This will fail at const eval time unless `value <=
                 // max` is true (in which case we get the index 0).
                 // It will also fail at runtime, of course, but in a
                 // kind of wacky way.
                 let _ = ["out of range value used"][
                     !(value <= $max) as usize
                 ];

                 unsafe {
                     $type { private: value }
                 }
             }

             #[inline]
             $v const unsafe fn from_u32_unchecked(value: u32) -> Self {
                 unsafe { $type { private: value } }
             }

             /// Extracts the value of this index as an integer.
             #[inline]
             $v fn index(self) -> usize {
                 self.as_usize()
             }

             /// Extracts the value of this index as a `u32`.
             #[inline]
             $v fn as_u32(self) -> u32 {
                 self.private
             }

             /// Extracts the value of this index as a `usize`.
             #[inline]
             $v fn as_usize(self) -> usize {
                 self.as_u32() as usize
             }
         }

         impl std::ops::Add<usize> for $type {
             type Output = Self;

             fn add(self, other: usize) -> Self {
                 Self::new(self.index() + other)
             }
         }

         impl Idx for $type {
             #[inline]
             fn new(value: usize) -> Self {
                 Self::from(value)
             }

             #[inline]
             fn index(self) -> usize {
                 usize::from(self)
             }
         }

         impl ::std::iter::Step for $type {
             #[inline]
             fn steps_between(start: &Self, end: &Self) -> Option<usize> {
                 <usize as ::std::iter::Step>::steps_between(
                     &Idx::index(*start),
                     &Idx::index(*end),
                 )
             }

             #[inline]
             fn replace_one(&mut self) -> Self {
                 ::std::mem::replace(self, Self::new(1))
             }

             #[inline]
             fn replace_zero(&mut self) -> Self {
                 ::std::mem::replace(self, Self::new(0))
             }

             #[inline]
             fn add_one(&self) -> Self {
                 Self::new(Idx::index(*self) + 1)
             }

             #[inline]
             fn sub_one(&self) -> Self {
                 Self::new(Idx::index(*self) - 1)
             }

             #[inline]
             fn add_usize(&self, u: usize) -> Option<Self> {
                 Idx::index(*self).checked_add(u).map(Self::new)
             }

             #[inline]
             fn sub_usize(&self, u: usize) -> Option<Self> {
                 Idx::index(*self).checked_sub(u).map(Self::new)
             }
         }

         impl From<$type> for u32 {
             #[inline]
             fn from(v: $type) -> u32 {
                 v.as_u32()
             }
         }

         impl From<$type> for usize {
             #[inline]
             fn from(v: $type) -> usize {
                 v.as_usize()
             }
         }

         impl From<usize> for $type {
             #[inline]
             fn from(value: usize) -> Self {
                 $type::from_usize(value)
             }
         }

         impl From<u32> for $type {
             #[inline]
             fn from(value: u32) -> Self {
                 $type::from_u32(value)
             }
         }

         $crate::newtype_index!(
             @handle_debug
             @derives      [$($derives,)*]
             @type         [$type]
             @debug_format [$debug_format]);
     );

     // base case for handle_debug where format is custom. No Debug implementation is emitted.
     (@handle_debug
      @derives      [$($_derives:ident,)*]
      @type         [$type:ident]
      @debug_format [custom]) => ();

     // base case for handle_debug, no debug overrides found, so use default
     (@handle_debug
      @derives      []
      @type         [$type:ident]
      @debug_format [$debug_format:tt]) => (
         impl ::std::fmt::Debug for $type {
             fn fmt(&self, fmt: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
                 write!(fmt, $debug_format, self.as_u32())
             }
         }
     );

     // Debug is requested for derive, don't generate any Debug implementation.
     (@handle_debug
      @derives      [Debug, $($derives:ident,)*]
      @type         [$type:ident]
      @debug_format [$debug_format:tt]) => ();

     // It's not Debug, so just pop it off the front of the derives stack and check the rest.
     (@handle_debug
      @derives      [$_derive:ident, $($derives:ident,)*]
      @type         [$type:ident]
      @debug_format [$debug_format:tt]) => (
         $crate::newtype_index!(
             @handle_debug
             @derives      [$($derives,)*]
             @type         [$type]
             @debug_format [$debug_format]);
     );

     // Append comma to end of derives list if it's missing
     (@attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    derive [$($derives:ident),*]
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           derive [$($derives,)*]
                           $($tokens)*);
     );

     // By not including the @derives marker in this list nor in the default args, we can force it
     // to come first if it exists. When encodable is custom, just use the derives list as-is.
     (@attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    derive [$($derives:ident,)+]
                    ENCODABLE = custom
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @attrs        [$(#[$attrs])*]
             @derives      [$($derives,)+]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
     );

     // By not including the @derives marker in this list nor in the default args, we can force it
     // to come first if it exists. When encodable isn't custom, add serialization traits by default.
     (@attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    derive [$($derives:ident,)+]
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @derives      [$($derives,)+ RustcEncodable,]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
         $crate::newtype_index!(@decodable $type);
     );

     // The case where no derives are added, but encodable is overridden. Don't
     // derive serialization traits
     (@attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    ENCODABLE = custom
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @derives      []
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
     );

     // The case where no derives are added, add serialization derives by default
     (@attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @derives      [RustcEncodable,]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
         $crate::newtype_index!(@decodable $type);
     );

     (@decodable $type:ident) => (
         impl ::rustc_serialize::Decodable for $type {
             fn decode<D: ::rustc_serialize::Decoder>(d: &mut D) -> Result<Self, D::Error> {
                 d.read_u32().map(Self::from)
             }
         }
     );

     // Rewrite final without comma to one that includes comma
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    $name:ident = $constant:expr) => (
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $name = $constant,);
     );

     // Rewrite final const without comma to one that includes comma
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    $(#[doc = $doc:expr])*
                    const $name:ident = $constant:expr) => (
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $(#[doc = $doc])* const $name = $constant,);
     );

     // Replace existing default for max
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$_max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    MAX = $max:expr,
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
     );

     // Replace existing default for debug_format
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$_debug_format:tt]
                    DEBUG_FORMAT = $debug_format:tt,
                    $($tokens:tt)*) => (
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
     );

     // Assign a user-defined constant
     (@derives      [$($derives:ident,)*]
      @attrs        [$(#[$attrs:meta])*]
      @type         [$type:ident]
      @max          [$max:expr]
      @vis          [$v:vis]
      @debug_format [$debug_format:tt]
                    $(#[doc = $doc:expr])*
                    const $name:ident = $constant:expr,
                    $($tokens:tt)*) => (
         $(#[doc = $doc])*
         pub const $name: $type = $type::from_u32_const($constant);
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]
             @type         [$type]
             @max          [$max]
             @vis          [$v]
             @debug_format [$debug_format]
                           $($tokens)*);
     );
 }

 #[derive(Clone, PartialEq, Eq, Hash)]
 pub struct IndexVec<I: Idx, T> {
     pub raw: Vec<T>,
     _marker: PhantomData<fn(&I)>
 }

 // Whether `IndexVec` is `Send` depends only on the data,
 // not the phantom data.
 unsafe impl<I: Idx, T> Send for IndexVec<I, T> where T: Send {}

 impl<I: Idx, T: Encodable> Encodable for IndexVec<I, T> {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         Encodable::encode(&self.raw, s)
     }
 }

 impl<I: Idx, T: Decodable> Decodable for IndexVec<I, T> {
     fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
         Decodable::decode(d).map(|v| {
             IndexVec { raw: v, _marker: PhantomData }
         })
     }
 }

 impl<I: Idx, T: fmt::Debug> fmt::Debug for IndexVec<I, T> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&self.raw, fmt)
     }
 }

 pub type Enumerated<I, J> = iter::Map<iter::Enumerate<J>, IntoIdx<I>>;

 impl<I: Idx, T> IndexVec<I, T> {
     #[inline]
     pub fn new() -> Self {
         IndexVec { raw: Vec::new(), _marker: PhantomData }
     }

     #[inline]
     pub fn from_raw(raw: Vec<T>) -> Self {
         IndexVec { raw, _marker: PhantomData }
     }

     #[inline]
     pub fn with_capacity(capacity: usize) -> Self {
         IndexVec { raw: Vec::with_capacity(capacity), _marker: PhantomData }
     }

     #[inline]
     pub fn from_elem<S>(elem: T, universe: &IndexVec<I, S>) -> Self
         where T: Clone
     {
         IndexVec { raw: vec![elem; universe.len()], _marker: PhantomData }
     }

     #[inline]
     pub fn from_elem_n(elem: T, n: usize) -> Self
         where T: Clone
     {
         IndexVec { raw: vec![elem; n], _marker: PhantomData }
     }

     #[inline]
     pub fn push(&mut self, d: T) -> I {
         let idx = I::new(self.len());
         self.raw.push(d);
         idx
     }

     #[inline]
     pub fn pop(&mut self) -> Option<T> {
         self.raw.pop()
     }

     #[inline]
     pub fn len(&self) -> usize {
         self.raw.len()
     }

     /// Gives the next index that will be assigned when `push` is
     /// called.
     #[inline]
     pub fn next_index(&self) -> I {
         I::new(self.len())
     }

     #[inline]
     pub fn is_empty(&self) -> bool {
         self.raw.is_empty()
     }

     #[inline]
     pub fn into_iter(self) -> vec::IntoIter<T> {
         self.raw.into_iter()
     }

     #[inline]
     pub fn into_iter_enumerated(self) -> Enumerated<I, vec::IntoIter<T>>
     {
         self.raw.into_iter().enumerate().map(IntoIdx { _marker: PhantomData })
     }

     #[inline]
     pub fn iter(&self) -> slice::Iter<'_, T> {
         self.raw.iter()
     }

     #[inline]
     pub fn iter_enumerated(&self) -> Enumerated<I, slice::Iter<'_, T>>
     {
         self.raw.iter().enumerate().map(IntoIdx { _marker: PhantomData })
     }

     #[inline]
     pub fn indices(&self) -> iter::Map<Range<usize>, IntoIdx<I>> {
         (0..self.len()).map(IntoIdx { _marker: PhantomData })
     }

     #[inline]
     pub fn iter_mut(&mut self) -> slice::IterMut<'_, T> {
         self.raw.iter_mut()
     }

     #[inline]
     pub fn iter_enumerated_mut(&mut self) -> Enumerated<I, slice::IterMut<'_, T>>
     {
         self.raw.iter_mut().enumerate().map(IntoIdx { _marker: PhantomData })
     }

     #[inline]
     pub fn drain<'a, R: RangeBounds<usize>>(
         &'a mut self, range: R) -> impl Iterator<Item=T> + 'a {
         self.raw.drain(range)
     }

     #[inline]
     pub fn drain_enumerated<'a, R: RangeBounds<usize>>(
         &'a mut self, range: R) -> impl Iterator<Item=(I, T)> + 'a {
         self.raw.drain(range).enumerate().map(IntoIdx { _marker: PhantomData })
     }

     #[inline]
     pub fn last(&self) -> Option<I> {
         self.len().checked_sub(1).map(I::new)
     }

     #[inline]
     pub fn shrink_to_fit(&mut self) {
         self.raw.shrink_to_fit()
     }

     #[inline]
     pub fn swap(&mut self, a: I, b: I) {
         self.raw.swap(a.index(), b.index())
     }

     #[inline]
     pub fn truncate(&mut self, a: usize) {
         self.raw.truncate(a)
     }

     #[inline]
     pub fn get(&self, index: I) -> Option<&T> {
         self.raw.get(index.index())
     }

     #[inline]
     pub fn get_mut(&mut self, index: I) -> Option<&mut T> {
         self.raw.get_mut(index.index())
     }

     /// Returns mutable references to two distinct elements, a and b. Panics if a == b.
     #[inline]
     pub fn pick2_mut(&mut self, a: I, b: I) -> (&mut T, &mut T) {
         let (ai, bi) = (a.index(), b.index());
         assert!(ai != bi);

         if ai < bi {
             let (c1, c2) = self.raw.split_at_mut(bi);
             (&mut c1[ai], &mut c2[0])
         } else {
             let (c2, c1) = self.pick2_mut(b, a);
             (c1, c2)
         }
     }

     pub fn convert_index_type<Ix: Idx>(self) -> IndexVec<Ix, T> {
         IndexVec {
             raw: self.raw,
             _marker: PhantomData,
         }
     }
 }

 impl<I: Idx, T: Clone> IndexVec<I, T> {
     /// Grows the index vector so that it contains an entry for
     /// `elem`; if that is already true, then has no
     /// effect. Otherwise, inserts new values as needed by invoking
     /// `fill_value`.
     #[inline]
     pub fn ensure_contains_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
         let min_new_len = elem.index() + 1;
         if self.len() < min_new_len {
             self.raw.resize_with(min_new_len, fill_value);
         }
     }

     #[inline]
     pub fn resize(&mut self, new_len: usize, value: T) {
         self.raw.resize(new_len, value)
     }

     #[inline]
     pub fn resize_to_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
         let min_new_len = elem.index() + 1;
         self.raw.resize_with(min_new_len, fill_value);
     }
 }

 impl<I: Idx, T: Ord> IndexVec<I, T> {
     #[inline]
     pub fn binary_search(&self, value: &T) -> Result<I, I> {
         match self.raw.binary_search(value) {
             Ok(i) => Ok(Idx::new(i)),
             Err(i) => Err(Idx::new(i)),
         }
     }
 }

 impl<I: Idx, T> Index<I> for IndexVec<I, T> {
     type Output = T;

     #[inline]
     fn index(&self, index: I) -> &T {
         &self.raw[index.index()]
     }
 }

 impl<I: Idx, T> IndexMut<I> for IndexVec<I, T> {
     #[inline]
     fn index_mut(&mut self, index: I) -> &mut T {
         &mut self.raw[index.index()]
     }
 }

 impl<I: Idx, T> Default for IndexVec<I, T> {
     #[inline]
     fn default() -> Self {
         Self::new()
     }
 }

 impl<I: Idx, T> Extend<T> for IndexVec<I, T> {
     #[inline]
     fn extend<J: IntoIterator<Item = T>>(&mut self, iter: J) {
         self.raw.extend(iter);
     }
 }

 impl<I: Idx, T> FromIterator<T> for IndexVec<I, T> {
     #[inline]
     fn from_iter<J>(iter: J) -> Self where J: IntoIterator<Item=T> {
         IndexVec { raw: FromIterator::from_iter(iter), _marker: PhantomData }
     }
 }

 impl<I: Idx, T> IntoIterator for IndexVec<I, T> {
     type Item = T;
     type IntoIter = vec::IntoIter<T>;

     #[inline]
     fn into_iter(self) -> vec::IntoIter<T> {
         self.raw.into_iter()
     }

 }

 impl<'a, I: Idx, T> IntoIterator for &'a IndexVec<I, T> {
     type Item = &'a T;
     type IntoIter = slice::Iter<'a, T>;

     #[inline]
     fn into_iter(self) -> slice::Iter<'a, T> {
         self.raw.iter()
     }
 }

 impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
     type Item = &'a mut T;
     type IntoIter = slice::IterMut<'a, T>;

     #[inline]
     fn into_iter(self) -> slice::IterMut<'a, T> {
         self.raw.iter_mut()
     }
 }

 pub struct IntoIdx<I: Idx> { _marker: PhantomData<fn(&I)> }
 impl<I: Idx, T> FnOnce<((usize, T),)> for IntoIdx<I> {
     type Output = (I, T);

     extern "rust-call" fn call_once(self, ((n, t),): ((usize, T),)) -> Self::Output {
         (I::new(n), t)
     }
 }

 impl<I: Idx, T> FnMut<((usize, T),)> for IntoIdx<I> {
     extern "rust-call" fn call_mut(&mut self, ((n, t),): ((usize, T),)) -> Self::Output {
         (I::new(n), t)
     }
 }

 impl<I: Idx> FnOnce<(usize,)> for IntoIdx<I> {
     type Output = I;

     extern "rust-call" fn call_once(self, (n,): (usize,)) -> Self::Output {
         I::new(n)
     }
 }

 impl<I: Idx> FnMut<(usize,)> for IntoIdx<I> {
     extern "rust-call" fn call_mut(&mut self, (n,): (usize,)) -> Self::Output {
         I::new(n)
     }
 }
	use rustc_serialize::{Encodable, Decodable, Encoder, Decoder};

	use std::fmt::Debug;
	use std::iter::{self, FromIterator};
	use std::slice;
	use std::marker::PhantomData;
	use std::ops::{Index, IndexMut, Range, RangeBounds};
	use std::fmt;
	use std::hash::Hash;
	use std::vec;
	use std::u32;

	/// Represents some newtyped `usize` wrapper.
	///
	/// Purpose: avoid mixing indexes for different bitvector domains.
	pub trait Idx: Copy + 'static + Ord + Debug + Hash {
	fn new(idx: usize) -> Self;

	fn index(self) -> usize;

	fn increment_by(&mut self, amount: usize) {
	*self = self.plus(amount);
	}

	fn plus(self, amount: usize) -> Self {
	Self::new(self.index() + amount)
	}
	}

	impl Idx for usize {
	#[inline]
	fn new(idx: usize) -> Self { idx }
	#[inline]
	fn index(self) -> usize { self }
	}

	impl Idx for u32 {
	#[inline]
	fn new(idx: usize) -> Self { assert!(idx <= u32::MAX as usize); idx as u32 }
	#[inline]
	fn index(self) -> usize { self as usize }
	}

	/// Creates a struct type `S` that can be used as an index with
	/// `IndexVec` and so on.
	///
	/// There are two ways of interacting with these indices:
	///
	/// - The `From` impls are the preferred way. So you can do
	/// `S::from(v)` with a `usize` or `u32`. And you can convert back
	/// to an integer with `u32::from(s)`.
	///
	/// - Alternatively, you can use the methods `S::new(v)` and `s.index()`
	/// to create/return a value.
	///
	/// Internally, the index uses a u32, so the index must not exceed
	/// `u32::MAX`. You can also customize things like the `Debug` impl,
	/// what traits are derived, and so forth via the macro.
	#[macro_export]
	#[allow_internal_unstable(step_trait, rustc_attrs)]
	macro_rules! newtype_index {
	// ---- public rules ----

	// Use default constants
	($(#[$attrs:meta])* $v:vis struct $name:ident { .. }) => (
	$crate::newtype_index!(
	// Leave out derives marker so we can use its absence to ensure it comes first
	@attrs [$(#[$attrs])*]
	@type [$name]
	// shave off 256 indices at the end to allow space for packing these indices into enums
	@max [0xFFFF_FF00]
	@vis [$v]
	@debug_format ["{}"]);
	);

	// Define any constants
	($(#[$attrs:meta])* $v:vis struct $name:ident { $($tokens:tt)+ }) => (
	$crate::newtype_index!(
	// Leave out derives marker so we can use its absence to ensure it comes first
	@attrs [$(#[$attrs])*]
	@type [$name]
	// shave off 256 indices at the end to allow space for packing these indices into enums
	@max [0xFFFF_FF00]
	@vis [$v]
	@debug_format ["{}"]
	$($tokens)+);
	);

	// ---- private rules ----

	// Base case, user-defined constants (if any) have already been defined
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]) => (
	$(#[$attrs])*
	#[derive(Copy, PartialEq, Eq, Hash, PartialOrd, Ord, $($derives),*)]
	#[rustc_layout_scalar_valid_range_end($max)]
	$v struct $type {
	private: u32
	}

	impl Clone for $type {
	fn clone(&self) -> Self {
	*self
	}
	}

	impl $type {
	$v const MAX_AS_U32: u32 = $max;

	$v const MAX: $type = $type::from_u32_const($max);

	#[inline]
	$v fn from_usize(value: usize) -> Self {
	assert!(value <= ($max as usize));
	unsafe {
	$type::from_u32_unchecked(value as u32)
	}
	}

	#[inline]
	$v fn from_u32(value: u32) -> Self {
	assert!(value <= $max);
	unsafe {
	$type::from_u32_unchecked(value)
	}
	}

	/// Hacky variant of `from_u32` for use in constants.
	/// This version checks the "max" constraint by using an
	/// invalid array dereference.
	#[inline]
	$v const fn from_u32_const(value: u32) -> Self {
	// This will fail at const eval time unless `value <=
	// max` is true (in which case we get the index 0).
	// It will also fail at runtime, of course, but in a
	// kind of wacky way.
	let _ = ["out of range value used"][
	!(value <= $max) as usize
	];

	unsafe {
	$type { private: value }
	}
	}

	#[inline]
	$v const unsafe fn from_u32_unchecked(value: u32) -> Self {
	unsafe { $type { private: value } }
	}

	/// Extracts the value of this index as an integer.
	#[inline]
	$v fn index(self) -> usize {
	self.as_usize()
	}

	/// Extracts the value of this index as a `u32`.
	#[inline]
	$v fn as_u32(self) -> u32 {
	self.private
	}

	/// Extracts the value of this index as a `usize`.
	#[inline]
	$v fn as_usize(self) -> usize {
	self.as_u32() as usize
	}
	}

	impl std::ops::Add<usize> for $type {
	type Output = Self;

	fn add(self, other: usize) -> Self {
	Self::new(self.index() + other)
	}
	}

	impl Idx for $type {
	#[inline]
	fn new(value: usize) -> Self {
	Self::from(value)
	}

	#[inline]
	fn index(self) -> usize {
	usize::from(self)
	}
	}

	impl ::std::iter::Step for $type {
	#[inline]
	fn steps_between(start: &Self, end: &Self) -> Option<usize> {
	<usize as ::std::iter::Step>::steps_between(
	&Idx::index(*start),
	&Idx::index(*end),
	)
	}

	#[inline]
	fn replace_one(&mut self) -> Self {
	::std::mem::replace(self, Self::new(1))
	}

	#[inline]
	fn replace_zero(&mut self) -> Self {
	::std::mem::replace(self, Self::new(0))
	}

	#[inline]
	fn add_one(&self) -> Self {
	Self::new(Idx::index(*self) + 1)
	}

	#[inline]
	fn sub_one(&self) -> Self {
	Self::new(Idx::index(*self) - 1)
	}

	#[inline]
	fn add_usize(&self, u: usize) -> Option<Self> {
	Idx::index(*self).checked_add(u).map(Self::new)
	}

	#[inline]
	fn sub_usize(&self, u: usize) -> Option<Self> {
	Idx::index(*self).checked_sub(u).map(Self::new)
	}
	}

	impl From<$type> for u32 {
	#[inline]
	fn from(v: $type) -> u32 {
	v.as_u32()
	}
	}

	impl From<$type> for usize {
	#[inline]
	fn from(v: $type) -> usize {
	v.as_usize()
	}
	}

	impl From<usize> for $type {
	#[inline]
	fn from(value: usize) -> Self {
	$type::from_usize(value)
	}
	}

	impl From<u32> for $type {
	#[inline]
	fn from(value: u32) -> Self {
	$type::from_u32(value)
	}
	}

	$crate::newtype_index!(
	@handle_debug
	@derives [$($derives,)*]
	@type [$type]
	@debug_format [$debug_format]);
	);

	// base case for handle_debug where format is custom. No Debug implementation is emitted.
	(@handle_debug
	@derives [$($_derives:ident,)*]
	@type [$type:ident]
	@debug_format [custom]) => ();

	// base case for handle_debug, no debug overrides found, so use default
	(@handle_debug
	@derives []
	@type [$type:ident]
	@debug_format [$debug_format:tt]) => (
	impl ::std::fmt::Debug for $type {
	fn fmt(&self, fmt: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
	write!(fmt, $debug_format, self.as_u32())
	}
	}
	);

	// Debug is requested for derive, don't generate any Debug implementation.
	(@handle_debug
	@derives [Debug, $($derives:ident,)*]
	@type [$type:ident]
	@debug_format [$debug_format:tt]) => ();

	// It's not Debug, so just pop it off the front of the derives stack and check the rest.
	(@handle_debug
	@derives [$_derive:ident, $($derives:ident,)*]
	@type [$type:ident]
	@debug_format [$debug_format:tt]) => (
	$crate::newtype_index!(
	@handle_debug
	@derives [$($derives,)*]
	@type [$type]
	@debug_format [$debug_format]);
	);

	// Append comma to end of derives list if it's missing
	(@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	derive [$($derives:ident),*]
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	derive [$($derives,)*]
	$($tokens)*);
	);

	// By not including the @derives marker in this list nor in the default args, we can force it
	// to come first if it exists. When encodable is custom, just use the derives list as-is.
	(@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	derive [$($derives:ident,)+]
	ENCODABLE = custom
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@attrs [$(#[$attrs])*]
	@derives [$($derives,)+]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	);

	// By not including the @derives marker in this list nor in the default args, we can force it
	// to come first if it exists. When encodable isn't custom, add serialization traits by default.
	(@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	derive [$($derives:ident,)+]
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@derives [$($derives,)+ RustcEncodable,]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	$crate::newtype_index!(@decodable $type);
	);

	// The case where no derives are added, but encodable is overridden. Don't
	// derive serialization traits
	(@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	ENCODABLE = custom
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@derives []
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	);

	// The case where no derives are added, add serialization derives by default
	(@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@derives [RustcEncodable,]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	$crate::newtype_index!(@decodable $type);
	);

	(@decodable $type:ident) => (
	impl ::rustc_serialize::Decodable for $type {
	fn decode<D: ::rustc_serialize::Decoder>(d: &mut D) -> Result<Self, D::Error> {
	d.read_u32().map(Self::from)
	}
	}
	);

	// Rewrite final without comma to one that includes comma
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	$name:ident = $constant:expr) => (
	$crate::newtype_index!(
	@derives [$($derives,)*]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$name = $constant,);
	);

	// Rewrite final const without comma to one that includes comma
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	$(#[doc = $doc:expr])*
	const $name:ident = $constant:expr) => (
	$crate::newtype_index!(
	@derives [$($derives,)*]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$(#[doc = $doc])* const $name = $constant,);
	);

	// Replace existing default for max
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$_max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	MAX = $max:expr,
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@derives [$($derives,)*]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	);

	// Replace existing default for debug_format
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$_debug_format:tt]
	DEBUG_FORMAT = $debug_format:tt,
	$($tokens:tt)*) => (
	$crate::newtype_index!(
	@derives [$($derives,)*]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	);

	// Assign a user-defined constant
	(@derives [$($derives:ident,)*]
	@attrs [$(#[$attrs:meta])*]
	@type [$type:ident]
	@max [$max:expr]
	@vis [$v:vis]
	@debug_format [$debug_format:tt]
	$(#[doc = $doc:expr])*
	const $name:ident = $constant:expr,
	$($tokens:tt)*) => (
	$(#[doc = $doc])*
	pub const $name: $type = $type::from_u32_const($constant);
	$crate::newtype_index!(
	@derives [$($derives,)*]
	@attrs [$(#[$attrs])*]
	@type [$type]
	@max [$max]
	@vis [$v]
	@debug_format [$debug_format]
	$($tokens)*);
	);
	}

	#[derive(Clone, PartialEq, Eq, Hash)]
	pub struct IndexVec<I: Idx, T> {
	pub raw: Vec<T>,
	_marker: PhantomData<fn(&I)>
	}

	// Whether `IndexVec` is `Send` depends only on the data,
	// not the phantom data.
	unsafe impl<I: Idx, T> Send for IndexVec<I, T> where T: Send {}

	impl<I: Idx, T: Encodable> Encodable for IndexVec<I, T> {
	fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
	Encodable::encode(&self.raw, s)
	}
	}

	impl<I: Idx, T: Decodable> Decodable for IndexVec<I, T> {
	fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
	Decodable::decode(d).map(\|v\| {
	IndexVec { raw: v, _marker: PhantomData }
	})
	}
	}

	impl<I: Idx, T: fmt::Debug> fmt::Debug for IndexVec<I, T> {
	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
	fmt::Debug::fmt(&self.raw, fmt)
	}
	}

	pub type Enumerated<I, J> = iter::Map<iter::Enumerate<J>, IntoIdx<I>>;

	impl<I: Idx, T> IndexVec<I, T> {
	#[inline]
	pub fn new() -> Self {
	IndexVec { raw: Vec::new(), _marker: PhantomData }
	}

	#[inline]
	pub fn from_raw(raw: Vec<T>) -> Self {
	IndexVec { raw, _marker: PhantomData }
	}

	#[inline]
	pub fn with_capacity(capacity: usize) -> Self {
	IndexVec { raw: Vec::with_capacity(capacity), _marker: PhantomData }
	}

	#[inline]
	pub fn from_elem<S>(elem: T, universe: &IndexVec<I, S>) -> Self
	where T: Clone
	{
	IndexVec { raw: vec![elem; universe.len()], _marker: PhantomData }
	}

	#[inline]
	pub fn from_elem_n(elem: T, n: usize) -> Self
	where T: Clone
	{
	IndexVec { raw: vec![elem; n], _marker: PhantomData }
	}

	#[inline]
	pub fn push(&mut self, d: T) -> I {
	let idx = I::new(self.len());
	self.raw.push(d);
	idx
	}

	#[inline]
	pub fn pop(&mut self) -> Option<T> {
	self.raw.pop()
	}

	#[inline]
	pub fn len(&self) -> usize {
	self.raw.len()
	}

	/// Gives the next index that will be assigned when `push` is
	/// called.
	#[inline]
	pub fn next_index(&self) -> I {
	I::new(self.len())
	}

	#[inline]
	pub fn is_empty(&self) -> bool {
	self.raw.is_empty()
	}

	#[inline]
	pub fn into_iter(self) -> vec::IntoIter<T> {
	self.raw.into_iter()
	}

	#[inline]
	pub fn into_iter_enumerated(self) -> Enumerated<I, vec::IntoIter<T>>
	{
	self.raw.into_iter().enumerate().map(IntoIdx { _marker: PhantomData })
	}

	#[inline]
	pub fn iter(&self) -> slice::Iter<'_, T> {
	self.raw.iter()
	}

	#[inline]
	pub fn iter_enumerated(&self) -> Enumerated<I, slice::Iter<'_, T>>
	{
	self.raw.iter().enumerate().map(IntoIdx { _marker: PhantomData })
	}

	#[inline]
	pub fn indices(&self) -> iter::Map<Range<usize>, IntoIdx<I>> {
	(0..self.len()).map(IntoIdx { _marker: PhantomData })
	}

	#[inline]
	pub fn iter_mut(&mut self) -> slice::IterMut<'_, T> {
	self.raw.iter_mut()
	}

	#[inline]
	pub fn iter_enumerated_mut(&mut self) -> Enumerated<I, slice::IterMut<'_, T>>
	{
	self.raw.iter_mut().enumerate().map(IntoIdx { _marker: PhantomData })
	}

	#[inline]
	pub fn drain<'a, R: RangeBounds<usize>>(
	&'a mut self, range: R) -> impl Iterator<Item=T> + 'a {
	self.raw.drain(range)
	}

	#[inline]
	pub fn drain_enumerated<'a, R: RangeBounds<usize>>(
	&'a mut self, range: R) -> impl Iterator<Item=(I, T)> + 'a {
	self.raw.drain(range).enumerate().map(IntoIdx { _marker: PhantomData })
	}

	#[inline]
	pub fn last(&self) -> Option<I> {
	self.len().checked_sub(1).map(I::new)
	}

	#[inline]
	pub fn shrink_to_fit(&mut self) {
	self.raw.shrink_to_fit()
	}

	#[inline]
	pub fn swap(&mut self, a: I, b: I) {
	self.raw.swap(a.index(), b.index())
	}

	#[inline]
	pub fn truncate(&mut self, a: usize) {
	self.raw.truncate(a)
	}

	#[inline]
	pub fn get(&self, index: I) -> Option<&T> {
	self.raw.get(index.index())
	}

	#[inline]
	pub fn get_mut(&mut self, index: I) -> Option<&mut T> {
	self.raw.get_mut(index.index())
	}

	/// Returns mutable references to two distinct elements, a and b. Panics if a == b.
	#[inline]
	pub fn pick2_mut(&mut self, a: I, b: I) -> (&mut T, &mut T) {
	let (ai, bi) = (a.index(), b.index());
	assert!(ai != bi);

	if ai < bi {
	let (c1, c2) = self.raw.split_at_mut(bi);
	(&mut c1[ai], &mut c2[0])
	} else {
	let (c2, c1) = self.pick2_mut(b, a);
	(c1, c2)
	}
	}

	pub fn convert_index_type<Ix: Idx>(self) -> IndexVec<Ix, T> {
	IndexVec {
	raw: self.raw,
	_marker: PhantomData,
	}
	}
	}

	impl<I: Idx, T: Clone> IndexVec<I, T> {
	/// Grows the index vector so that it contains an entry for
	/// `elem`; if that is already true, then has no
	/// effect. Otherwise, inserts new values as needed by invoking
	/// `fill_value`.
	#[inline]
	pub fn ensure_contains_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
	let min_new_len = elem.index() + 1;
	if self.len() < min_new_len {
	self.raw.resize_with(min_new_len, fill_value);
	}
	}

	#[inline]
	pub fn resize(&mut self, new_len: usize, value: T) {
	self.raw.resize(new_len, value)
	}

	#[inline]
	pub fn resize_to_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
	let min_new_len = elem.index() + 1;
	self.raw.resize_with(min_new_len, fill_value);
	}
	}

	impl<I: Idx, T: Ord> IndexVec<I, T> {
	#[inline]
	pub fn binary_search(&self, value: &T) -> Result<I, I> {
	match self.raw.binary_search(value) {
	Ok(i) => Ok(Idx::new(i)),
	Err(i) => Err(Idx::new(i)),
	}
	}
	}

	impl<I: Idx, T> Index<I> for IndexVec<I, T> {
	type Output = T;

	#[inline]
	fn index(&self, index: I) -> &T {
	&self.raw[index.index()]
	}
	}

	impl<I: Idx, T> IndexMut<I> for IndexVec<I, T> {
	#[inline]
	fn index_mut(&mut self, index: I) -> &mut T {
	&mut self.raw[index.index()]
	}
	}

	impl<I: Idx, T> Default for IndexVec<I, T> {
	#[inline]
	fn default() -> Self {
	Self::new()
	}
	}

	impl<I: Idx, T> Extend<T> for IndexVec<I, T> {
	#[inline]
	fn extend<J: IntoIterator<Item = T>>(&mut self, iter: J) {
	self.raw.extend(iter);
	}
	}

	impl<I: Idx, T> FromIterator<T> for IndexVec<I, T> {
	#[inline]
	fn from_iter<J>(iter: J) -> Self where J: IntoIterator<Item=T> {
	IndexVec { raw: FromIterator::from_iter(iter), _marker: PhantomData }
	}
	}

	impl<I: Idx, T> IntoIterator for IndexVec<I, T> {
	type Item = T;
	type IntoIter = vec::IntoIter<T>;

	#[inline]
	fn into_iter(self) -> vec::IntoIter<T> {
	self.raw.into_iter()
	}

	}

	impl<'a, I: Idx, T> IntoIterator for &'a IndexVec<I, T> {
	type Item = &'a T;
	type IntoIter = slice::Iter<'a, T>;

	#[inline]
	fn into_iter(self) -> slice::Iter<'a, T> {
	self.raw.iter()
	}
	}

	impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
	type Item = &'a mut T;
	type IntoIter = slice::IterMut<'a, T>;

	#[inline]
	fn into_iter(self) -> slice::IterMut<'a, T> {
	self.raw.iter_mut()
	}
	}

	pub struct IntoIdx<I: Idx> { _marker: PhantomData<fn(&I)> }
	impl<I: Idx, T> FnOnce<((usize, T),)> for IntoIdx<I> {
	type Output = (I, T);

	extern "rust-call" fn call_once(self, ((n, t),): ((usize, T),)) -> Self::Output {
	(I::new(n), t)
	}
	}

	impl<I: Idx, T> FnMut<((usize, T),)> for IntoIdx<I> {
	extern "rust-call" fn call_mut(&mut self, ((n, t),): ((usize, T),)) -> Self::Output {
	(I::new(n), t)
	}
	}

	impl<I: Idx> FnOnce<(usize,)> for IntoIdx<I> {
	type Output = I;

	extern "rust-call" fn call_once(self, (n,): (usize,)) -> Self::Output {
	I::new(n)
	}
	}

	impl<I: Idx> FnMut<(usize,)> for IntoIdx<I> {
	extern "rust-call" fn call_mut(&mut self, (n,): (usize,)) -> Self::Output {
	I::new(n)
	}
	}