Introduce ruff_index crate (#4597)

crates/ruff_index/src/idx.rs

@@ -0,0 +1,60 @@
+use std::hash::Hash;
+
+/// Represents a newtype wrapper used to index into a Vec or a slice.
+///
+/// You can use the [`newtype_index`](crate::newtype_index) macro to define your own index.
+pub trait Idx: Copy + PartialEq + Eq + Hash + std::fmt::Debug + 'static {
+    fn new(value: usize) -> Self;
+
+    fn index(self) -> usize;
+}
+
+#[cfg(test)]
+mod tests {
+
+    use crate::newtype_index;
+    use static_assertions::{assert_eq_size, assert_impl_all};
+
+    // Allows the macro invocation below to work
+    use crate as ruff_index;
+
+    #[newtype_index]
+    #[derive(PartialOrd, Ord)]
+    struct MyIndex;
+
+    assert_impl_all!(MyIndex: Ord, PartialOrd);
+    assert_eq_size!(MyIndex, Option<MyIndex>);
+
+    #[test]
+    #[should_panic(expected = "assertion failed: value <= Self::MAX")]
+    fn from_u32_panics_for_u32_max() {
+        MyIndex::from_u32(u32::MAX);
+    }
+
+    #[test]
+    #[should_panic(expected = "assertion failed: value <= Self::MAX")]
+    fn from_usize_panics_for_u32_max() {
+        MyIndex::from_usize(u32::MAX as usize);
+    }
+
+    #[test]
+    fn max_value() {
+        let max_value = MyIndex::from_u32(u32::MAX - 1);
+
+        assert_eq!(max_value.as_u32(), u32::MAX - 1);
+    }
+
+    #[test]
+    fn max_value_usize() {
+        let max_value = MyIndex::from_usize((u32::MAX - 1) as usize);
+
+        assert_eq!(max_value.as_u32(), u32::MAX - 1);
+    }
+
+    #[test]
+    fn debug() {
+        let output = format!("{:?}", MyIndex::from(10u32));
+
+        assert_eq!(output, "MyIndex(10)");
+    }
+}

crates/ruff_index/src/lib.rs

@@ -0,0 +1,13 @@
+//! Provides new-type wrappers for collections that are indexed by a [`Idx`] rather
+//! than `usize`.
+//!
+//! Inspired by [rustc_index](https://github.com/rust-lang/rust/blob/master/compiler/rustc_index/src/lib.rs).
+
+mod idx;
+mod slice;
+mod vec;
+
+pub use idx::Idx;
+pub use ruff_macros::newtype_index;
+pub use slice::IndexSlice;
+pub use vec::IndexVec;

crates/ruff_index/src/slice.rs

@@ -0,0 +1,178 @@
+use crate::vec::IndexVec;
+use crate::Idx;
+use std::fmt::{Debug, Formatter};
+use std::marker::PhantomData;
+use std::ops::{Index, IndexMut};
+
+/// A view into contiguous `T`s, indexed by `I` rather than by `usize`.
+#[derive(PartialEq, Eq, Hash)]
+#[repr(transparent)]
+pub struct IndexSlice<I, T> {
+    index: PhantomData<I>,
+    pub raw: [T],
+}
+
+impl<I: Idx, T> IndexSlice<I, T> {
+    #[inline]
+    pub const fn empty() -> &'static Self {
+        Self::from_raw(&[])
+    }
+
+    #[inline]
+    pub const fn from_raw(raw: &[T]) -> &Self {
+        let ptr: *const [T] = raw;
+
+        #[allow(unsafe_code)]
+        // SAFETY: `IndexSlice` is `repr(transparent)` over a normal slice
+        unsafe {
+            &*(ptr as *const Self)
+        }
+    }
+
+    #[inline]
+    pub fn from_raw_mut(raw: &mut [T]) -> &mut Self {
+        let ptr: *mut [T] = raw;
+
+        #[allow(unsafe_code)]
+        // SAFETY: `IndexSlice` is `repr(transparent)` over a normal slice
+        unsafe {
+            &mut *(ptr as *mut Self)
+        }
+    }
+
+    #[inline]
+    pub const fn len(&self) -> usize {
+        self.raw.len()
+    }
+
+    #[inline]
+    pub const fn is_empty(&self) -> bool {
+        self.raw.is_empty()
+    }
+
+    #[inline]
+    pub fn iter(&self) -> std::slice::Iter<'_, T> {
+        self.raw.iter()
+    }
+
+    /// Returns an iterator over the indices
+    #[inline]
+    pub fn indices(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = I> + ExactSizeIterator + Clone + 'static {
+        (0..self.len()).map(|n| I::new(n))
+    }
+
+    #[inline]
+    pub fn iter_mut(&mut self) -> std::slice::IterMut<'_, T> {
+        self.raw.iter_mut()
+    }
+
+    #[inline]
+    pub fn last_index(&self) -> Option<I> {
+        self.len().checked_sub(1).map(I::new)
+    }
+
+    #[inline]
+    pub fn swap(&mut self, a: I, b: I) {
+        self.raw.swap(a.index(), b.index());
+    }
+
+    #[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())
+    }
+
+    #[inline]
+    pub fn binary_search(&self, value: &T) -> Result<I, I>
+    where
+        T: Ord,
+    {
+        match self.raw.binary_search(value) {
+            Ok(i) => Ok(Idx::new(i)),
+            Err(i) => Err(Idx::new(i)),
+        }
+    }
+}
+
+impl<I, T> Debug for IndexSlice<I, T>
+where
+    I: Idx,
+    T: Debug,
+{
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Debug::fmt(&self.raw, fmt)
+    }
+}
+
+impl<I: Idx, T> Index<I> for IndexSlice<I, T> {
+    type Output = T;
+
+    #[inline]
+    fn index(&self, index: I) -> &T {
+        &self.raw[index.index()]
+    }
+}
+
+impl<I: Idx, T> IndexMut<I> for IndexSlice<I, T> {
+    #[inline]
+    fn index_mut(&mut self, index: I) -> &mut T {
+        &mut self.raw[index.index()]
+    }
+}
+
+impl<'a, I: Idx, T> IntoIterator for &'a IndexSlice<I, T> {
+    type Item = &'a T;
+    type IntoIter = std::slice::Iter<'a, T>;
+
+    #[inline]
+    fn into_iter(self) -> std::slice::Iter<'a, T> {
+        self.raw.iter()
+    }
+}
+
+impl<'a, I: Idx, T> IntoIterator for &'a mut IndexSlice<I, T> {
+    type Item = &'a mut T;
+    type IntoIter = std::slice::IterMut<'a, T>;
+
+    #[inline]
+    fn into_iter(self) -> std::slice::IterMut<'a, T> {
+        self.raw.iter_mut()
+    }
+}
+
+impl<I: Idx, T: Clone> ToOwned for IndexSlice<I, T> {
+    type Owned = IndexVec<I, T>;
+
+    fn to_owned(&self) -> IndexVec<I, T> {
+        IndexVec::from_raw(self.raw.to_owned())
+    }
+
+    fn clone_into(&self, target: &mut IndexVec<I, T>) {
+        self.raw.clone_into(&mut target.raw);
+    }
+}
+
+impl<I: Idx, T> Default for &IndexSlice<I, T> {
+    #[inline]
+    fn default() -> Self {
+        IndexSlice::from_raw(Default::default())
+    }
+}
+
+impl<I: Idx, T> Default for &mut IndexSlice<I, T> {
+    #[inline]
+    fn default() -> Self {
+        IndexSlice::from_raw_mut(Default::default())
+    }
+}
+
+// Whether `IndexSlice` is `Send` depends only on the data,
+// not the phantom data.
+#[allow(unsafe_code)]
+unsafe impl<I: Idx, T> Send for IndexSlice<I, T> where T: Send {}

crates/ruff_index/src/vec.rs

@@ -0,0 +1,170 @@
+use crate::slice::IndexSlice;
+use crate::Idx;
+use std::borrow::{Borrow, BorrowMut};
+use std::fmt::{Debug, Formatter};
+use std::marker::PhantomData;
+use std::ops::{Deref, DerefMut, RangeBounds};
+
+/// An owned sequence of `T` indexed by `I`
+#[derive(Clone, PartialEq, Eq, Hash)]
+#[repr(transparent)]
+pub struct IndexVec<I, T> {
+    pub raw: Vec<T>,
+    index: PhantomData<I>,
+}
+
+impl<I: Idx, T> IndexVec<I, T> {
+    #[inline]
+    pub fn new() -> Self {
+        Self {
+            raw: Vec::new(),
+            index: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self {
+            raw: Vec::with_capacity(capacity),
+            index: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn from_raw(raw: Vec<T>) -> Self {
+        Self {
+            raw,
+            index: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn drain<R: RangeBounds<usize>>(&mut self, range: R) -> impl Iterator<Item = T> + '_ {
+        self.raw.drain(range)
+    }
+
+    #[inline]
+    pub fn truncate(&mut self, a: usize) {
+        self.raw.truncate(a);
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &IndexSlice<I, T> {
+        IndexSlice::from_raw(&self.raw)
+    }
+
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut IndexSlice<I, T> {
+        IndexSlice::from_raw_mut(&mut self.raw)
+    }
+
+    #[inline]
+    pub fn push(&mut self, data: T) -> I {
+        let index = self.next_index();
+        self.raw.push(data);
+        index
+    }
+
+    #[inline]
+    pub fn next_index(&self) -> I {
+        I::new(self.raw.len())
+    }
+}
+
+impl<I, T> Debug for IndexVec<I, T>
+where
+    T: Debug,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Debug::fmt(&self.raw, f)
+    }
+}
+
+impl<I: Idx, T> Deref for IndexVec<I, T> {
+    type Target = IndexSlice<I, T>;
+
+    fn deref(&self) -> &Self::Target {
+        self.as_slice()
+    }
+}
+
+impl<I: Idx, T> DerefMut for IndexVec<I, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.as_mut_slice()
+    }
+}
+
+impl<I: Idx, T> Borrow<IndexSlice<I, T>> for IndexVec<I, T> {
+    fn borrow(&self) -> &IndexSlice<I, T> {
+        self
+    }
+}
+
+impl<I: Idx, T> BorrowMut<IndexSlice<I, T>> for IndexVec<I, T> {
+    fn borrow_mut(&mut self) -> &mut IndexSlice<I, T> {
+        self
+    }
+}
+
+impl<I, T> Extend<T> for IndexVec<I, T> {
+    #[inline]
+    fn extend<Iter: IntoIterator<Item = T>>(&mut self, iter: Iter) {
+        self.raw.extend(iter);
+    }
+}
+
+impl<I: Idx, T> FromIterator<T> for IndexVec<I, T> {
+    #[inline]
+    fn from_iter<Iter: IntoIterator<Item = T>>(iter: Iter) -> Self {
+        Self::from_raw(Vec::from_iter(iter))
+    }
+}
+
+impl<I: Idx, T> IntoIterator for IndexVec<I, T> {
+    type Item = T;
+    type IntoIter = std::vec::IntoIter<T>;
+
+    #[inline]
+    fn into_iter(self) -> std::vec::IntoIter<T> {
+        self.raw.into_iter()
+    }
+}
+
+impl<'a, I: Idx, T> IntoIterator for &'a IndexVec<I, T> {
+    type Item = &'a T;
+    type IntoIter = std::slice::Iter<'a, T>;
+
+    #[inline]
+    fn into_iter(self) -> std::slice::Iter<'a, T> {
+        self.iter()
+    }
+}
+
+impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
+    type Item = &'a mut T;
+    type IntoIter = std::slice::IterMut<'a, T>;
+
+    #[inline]
+    fn into_iter(self) -> std::slice::IterMut<'a, T> {
+        self.iter_mut()
+    }
+}
+
+impl<I: Idx, T> Default for IndexVec<I, T> {
+    #[inline]
+    fn default() -> Self {
+        IndexVec::new()
+    }
+}
+
+impl<I: Idx, T, const N: usize> From<[T; N]> for IndexVec<I, T> {
+    #[inline]
+    fn from(array: [T; N]) -> Self {
+        IndexVec::from_raw(array.into())
+    }
+}
+
+// Whether `IndexVec` is `Send` depends only on the data,
+// not the phantom data.
+#[allow(unsafe_code)]
+unsafe impl<I: Idx, T> Send for IndexVec<I, T> where T: Send {}