Introduce ruff_index crate (#4597)

crates/ruff_python_semantic/src/node.rs

@@ -1,6 +1,6 @@
-use std::num::{NonZeroU32, TryFromIntError};
 use std::ops::{Index, IndexMut};
 
+use ruff_index::{newtype_index, IndexVec};
 use rustc_hash::FxHashMap;
 use rustpython_parser::ast::Stmt;
 
@@ -11,24 +11,9 @@ use ruff_python_ast::types::RefEquality;
 /// Using a `u32` is sufficient because Ruff only supports parsing documents with a size of max `u32::max`
 /// and it is impossible to have more statements than characters in the file. We use a `NonZeroU32` to
 /// take advantage of memory layout optimizations.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Ord, PartialOrd)]
-pub struct NodeId(NonZeroU32);
-
-/// Convert a `usize` to a `NodeId` (by adding 1 to the value, and casting to `NonZeroU32`).
-impl TryFrom<usize> for NodeId {
-    type Error = TryFromIntError;
-
-    fn try_from(value: usize) -> Result<Self, Self::Error> {
-        Ok(Self(NonZeroU32::try_from(u32::try_from(value)? + 1)?))
-    }
-}
-
-/// Convert a `NodeId` to a `usize` (by subtracting 1 from the value, and casting to `usize`).
-impl From<NodeId> for usize {
-    fn from(value: NodeId) -> Self {
-        value.0.get() as usize - 1
-    }
-}
+#[newtype_index]
+#[derive(Ord, PartialOrd)]
+pub struct NodeId;
 
 /// A [`Node`] represents a statement in a program, along with a pointer to its parent (if any).
 #[derive(Debug)]
@@ -44,7 +29,7 @@ struct Node<'a> {
 /// The nodes of a program indexed by [`NodeId`]
 #[derive(Debug, Default)]
 pub struct Nodes<'a> {
-    nodes: Vec<Node<'a>>,
+    nodes: IndexVec<NodeId, Node<'a>>,
     node_to_id: FxHashMap<RefEquality<'a, Stmt>, NodeId>,
 }
 
@@ -53,16 +38,15 @@ impl<'a> Nodes<'a> {
     ///
     /// Panics if a node with the same pointer already exists.
     pub fn insert(&mut self, stmt: &'a Stmt, parent: Option<NodeId>) -> NodeId {
-        let next_id = NodeId::try_from(self.nodes.len()).unwrap();
+        let next_id = self.nodes.next_index();
         if let Some(existing_id) = self.node_to_id.insert(RefEquality(stmt), next_id) {
             panic!("Node already exists with id {existing_id:?}");
         }
         self.nodes.push(Node {
             stmt,
             parent,
-            depth: parent.map_or(0, |parent| self.nodes[usize::from(parent)].depth + 1),
-        });
-        next_id
+            depth: parent.map_or(0, |parent| self.nodes[parent].depth + 1),
+        })
     }
 
     /// Returns the [`NodeId`] of the given node.
@@ -74,26 +58,24 @@ impl<'a> Nodes<'a> {
     /// Return the [`NodeId`] of the parent node.
     #[inline]
     pub fn parent_id(&self, node_id: NodeId) -> Option<NodeId> {
-        self.nodes[usize::from(node_id)].parent
+        self.nodes[node_id].parent
     }
 
     /// Return the depth of the node.
     #[inline]
     pub fn depth(&self, node_id: NodeId) -> u32 {
-        self.nodes[usize::from(node_id)].depth
+        self.nodes[node_id].depth
     }
 
     /// Returns an iterator over all [`NodeId`] ancestors, starting from the given [`NodeId`].
     pub fn ancestor_ids(&self, node_id: NodeId) -> impl Iterator<Item = NodeId> + '_ {
-        std::iter::successors(Some(node_id), |&node_id| {
-            self.nodes[usize::from(node_id)].parent
-        })
+        std::iter::successors(Some(node_id), |&node_id| self.nodes[node_id].parent)
     }
 
     /// Return the parent of the given node.
     pub fn parent(&self, node: &'a Stmt) -> Option<&'a Stmt> {
         let node_id = self.node_to_id.get(&RefEquality(node))?;
-        let parent_id = self.nodes[usize::from(*node_id)].parent?;
+        let parent_id = self.nodes[*node_id].parent?;
         Some(self[parent_id])
     }
 }
@@ -101,13 +83,15 @@ impl<'a> Nodes<'a> {
 impl<'a> Index<NodeId> for Nodes<'a> {
     type Output = &'a Stmt;
 
+    #[inline]
     fn index(&self, index: NodeId) -> &Self::Output {
-        &self.nodes[usize::from(index)].stmt
+        &self.nodes[index].stmt
     }
 }
 
 impl<'a> IndexMut<NodeId> for Nodes<'a> {
+    #[inline]
     fn index_mut(&mut self, index: NodeId) -> &mut Self::Output {
-        &mut self.nodes[usize::from(index)].stmt
+        &mut self.nodes[index].stmt
     }
 }