Red-knot: Track scopes per expression (#11754)

crates/red_knot/src/semantic.rs

@@ -12,6 +12,8 @@ use crate::module::ModuleName;
 use crate::parse::parse;
 use crate::Name;
 use flow_graph::{FlowGraph, FlowGraphBuilder, FlowNodeId, ReachableDefinitionsIterator};
+use ruff_index::newtype_index;
+use rustc_hash::FxHashMap;
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 pub(crate) use symbol_table::{Definition, Dependency, SymbolId};
@@ -49,6 +51,9 @@ pub fn resolve_global_symbol(
     Ok(Some(GlobalSymbolId { file_id, symbol_id }))
 }
 
+#[newtype_index]
+pub struct ExpressionId;
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct GlobalSymbolId {
     pub(crate) file_id: FileId,
@@ -59,6 +64,7 @@ pub struct GlobalSymbolId {
 pub struct SemanticIndex {
     symbol_table: SymbolTable,
     flow_graph: FlowGraph,
+    expressions: FxHashMap<NodeKey, ExpressionId>,
 }
 
 impl SemanticIndex {
@@ -71,6 +77,7 @@ impl SemanticIndex {
                 scope_id: root_scope_id,
                 current_flow_node_id: FlowGraph::start(),
             }],
+            expressions: FxHashMap::default(),
             current_definition: None,
         };
         indexer.visit_body(&module.body);
@@ -85,13 +92,18 @@ impl SemanticIndex {
         symbol_id: SymbolId,
         use_expr: &ast::Expr,
     ) -> ReachableDefinitionsIterator {
+        let expression_id = self.expression_id(use_expr);
         ReachableDefinitionsIterator::new(
             &self.flow_graph,
             symbol_id,
-            self.flow_graph.for_expr(use_expr),
+            self.flow_graph.for_expr(expression_id),
         )
     }
 
+    pub fn expression_id(&self, expression: &ast::Expr) -> ExpressionId {
+        self.expressions[&NodeKey::from_node(expression.into())]
+    }
+
     pub fn symbol_table(&self) -> &SymbolTable {
         &self.symbol_table
     }
@@ -110,6 +122,7 @@ struct SemanticIndexer {
     scopes: Vec<ScopeState>,
     /// the definition whose target(s) we are currently walking
     current_definition: Option<Definition>,
+    expressions: FxHashMap<NodeKey, ExpressionId>,
 }
 
 impl SemanticIndexer {
@@ -122,6 +135,7 @@ impl SemanticIndexer {
         SemanticIndex {
             flow_graph: flow_graph_builder.finish(),
             symbol_table: symbol_table_builder.finish(),
+            expressions: self.expressions,
         }
     }
 
@@ -240,8 +254,19 @@ impl PreorderVisitor<'_> for SemanticIndexer {
                 }
             }
         }
-        self.flow_graph_builder
-            .record_expr(expr, self.current_flow_node());
+
+        let expression_id = self
+            .flow_graph_builder
+            .record_expr(self.current_flow_node());
+
+        debug_assert_eq!(
+            expression_id,
+            self.symbol_table_builder
+                .record_expression(self.cur_scope())
+        );
+
+        self.expressions
+            .insert(NodeKey::from_node(expr.into()), expression_id);
         ast::visitor::preorder::walk_expr(self, expr);
     }
 
@@ -744,4 +769,29 @@ mod tests {
         };
         assert_eq!(*num, 1);
     }
+
+    #[test]
+    fn expression_scope() {
+        let parsed = parse("x = 1;\ndef test():\n  y = 4");
+        let ast = parsed.syntax();
+        let index = SemanticIndex::from_ast(ast);
+        let table = &index.symbol_table;
+
+        let x_sym = table
+            .root_symbol_by_name("x")
+            .expect("x symbol should exist");
+
+        let x_stmt = ast.body[0].as_assign_stmt().unwrap();
+
+        let x_id = index.expression_id(&x_stmt.targets[0]);
+
+        assert_eq!(table.scope_of_expression(x_id).kind(), ScopeKind::Module);
+        assert_eq!(table.scope_id_of_expression(x_id), x_sym.scope_id());
+
+        let def = ast.body[1].as_function_def_stmt().unwrap();
+        let y_stmt = def.body[0].as_assign_stmt().unwrap();
+        let y_id = index.expression_id(&y_stmt.targets[0]);
+
+        assert_eq!(table.scope_of_expression(y_id).kind(), ScopeKind::Function);
+    }
 }

crates/red_knot/src/semantic/flow_graph.rs

@@ -1,8 +1,6 @@
 use super::symbol_table::{Definition, SymbolId};
-use crate::ast_ids::NodeKey;
+use crate::semantic::ExpressionId;
 use ruff_index::{newtype_index, IndexVec};
-use ruff_python_ast as ast;
-use rustc_hash::FxHashMap;
 use std::iter::FusedIterator;
 
 #[newtype_index]
@@ -40,7 +38,7 @@ pub(crate) struct PhiFlowNode {
 #[derive(Debug)]
 pub struct FlowGraph {
     flow_nodes_by_id: IndexVec<FlowNodeId, FlowNode>,
-    ast_to_flow: FxHashMap<NodeKey, FlowNodeId>,
+    expression_map: IndexVec<ExpressionId, FlowNodeId>,
 }
 
 impl FlowGraph {
@@ -48,9 +46,8 @@ impl FlowGraph {
         FlowNodeId::from_usize(0)
     }
 
-    pub fn for_expr(&self, expr: &ast::Expr) -> FlowNodeId {
-        let node_key = NodeKey::from_node(expr.into());
-        self.ast_to_flow[&node_key]
+    pub fn for_expr(&self, expr: ExpressionId) -> FlowNodeId {
+        self.expression_map[expr]
     }
 }
 
@@ -63,7 +60,7 @@ impl FlowGraphBuilder {
     pub(crate) fn new() -> Self {
         let mut graph = FlowGraph {
             flow_nodes_by_id: IndexVec::default(),
-            ast_to_flow: FxHashMap::default(),
+            expression_map: IndexVec::default(),
         };
         graph.flow_nodes_by_id.push(FlowNode::Start);
         Self { flow_graph: graph }
@@ -101,13 +98,13 @@ impl FlowGraphBuilder {
         }))
     }
 
-    pub(crate) fn record_expr(&mut self, expr: &ast::Expr, node_id: FlowNodeId) {
-        self.flow_graph
-            .ast_to_flow
-            .insert(NodeKey::from_node(expr.into()), node_id);
+    pub(super) fn record_expr(&mut self, node_id: FlowNodeId) -> ExpressionId {
+        self.flow_graph.expression_map.push(node_id)
     }
 
-    pub(crate) fn finish(self) -> FlowGraph {
+    pub(super) fn finish(mut self) -> FlowGraph {
+        self.flow_graph.flow_nodes_by_id.shrink_to_fit();
+        self.flow_graph.expression_map.shrink_to_fit();
         self.flow_graph
     }
 }

crates/red_knot/src/semantic/symbol_table.rs

@@ -13,6 +13,7 @@ use ruff_python_ast as ast;
 
 use crate::ast_ids::{NodeKey, TypedNodeKey};
 use crate::module::ModuleName;
+use crate::semantic::ExpressionId;
 use crate::Name;
 
 type Map<K, V> = hashbrown::HashMap<K, V, ()>;
@@ -192,6 +193,8 @@ pub struct SymbolTable {
     defs: FxHashMap<SymbolId, Vec<Definition>>,
     /// map of AST node (e.g. class/function def) to sub-scope it creates
     scopes_by_node: FxHashMap<NodeKey, ScopeId>,
+    /// Maps expressions to their enclosing scope.
+    expression_scopes: IndexVec<ExpressionId, ScopeId>,
     /// dependencies of this module
     dependencies: Vec<Dependency>,
 }
@@ -283,6 +286,14 @@ impl SymbolTable {
         &self.scopes_by_id[self.scope_id_of_symbol(symbol_id)]
     }
 
+    pub fn scope_id_of_expression(&self, expression: ExpressionId) -> ScopeId {
+        self.expression_scopes[expression]
+    }
+
+    pub fn scope_of_expression(&self, expr_id: ExpressionId) -> &Scope {
+        &self.scopes_by_id[self.scope_id_of_expression(expr_id)]
+    }
+
     pub fn parent_scopes(
         &self,
         scope_id: ScopeId,
@@ -393,17 +404,18 @@ where
 }
 
 #[derive(Debug)]
-pub(crate) struct SymbolTableBuilder {
+pub(super) struct SymbolTableBuilder {
     symbol_table: SymbolTable,
 }
 
 impl SymbolTableBuilder {
-    pub(crate) fn new() -> Self {
+    pub(super) fn new() -> Self {
         let mut table = SymbolTable {
             scopes_by_id: IndexVec::new(),
             symbols_by_id: IndexVec::new(),
             defs: FxHashMap::default(),
             scopes_by_node: FxHashMap::default(),
+            expression_scopes: IndexVec::new(),
             dependencies: Vec::new(),
         };
         table.scopes_by_id.push(Scope {
@@ -420,11 +432,18 @@ impl SymbolTableBuilder {
         }
     }
 
-    pub(crate) fn finish(self) -> SymbolTable {
-        self.symbol_table
+    pub(super) fn finish(self) -> SymbolTable {
+        let mut symbol_table = self.symbol_table;
+        symbol_table.scopes_by_id.shrink_to_fit();
+        symbol_table.symbols_by_id.shrink_to_fit();
+        symbol_table.defs.shrink_to_fit();
+        symbol_table.scopes_by_node.shrink_to_fit();
+        symbol_table.expression_scopes.shrink_to_fit();
+        symbol_table.dependencies.shrink_to_fit();
+        symbol_table
     }
 
-    pub(crate) fn add_or_update_symbol(
+    pub(super) fn add_or_update_symbol(
         &mut self,
         scope_id: ScopeId,
         name: &str,
@@ -462,7 +481,7 @@ impl SymbolTableBuilder {
         }
     }
 
-    pub(crate) fn add_definition(&mut self, symbol_id: SymbolId, definition: Definition) {
+    pub(super) fn add_definition(&mut self, symbol_id: SymbolId, definition: Definition) {
         self.symbol_table
             .defs
             .entry(symbol_id)
@@ -470,7 +489,7 @@ impl SymbolTableBuilder {
             .push(definition);
     }
 
-    pub(crate) fn add_child_scope(
+    pub(super) fn add_child_scope(
         &mut self,
         parent_scope_id: ScopeId,
         name: &str,
@@ -492,13 +511,18 @@ impl SymbolTableBuilder {
         new_scope_id
     }
 
-    pub(crate) fn record_scope_for_node(&mut self, node_key: NodeKey, scope_id: ScopeId) {
+    pub(super) fn record_scope_for_node(&mut self, node_key: NodeKey, scope_id: ScopeId) {
         self.symbol_table.scopes_by_node.insert(node_key, scope_id);
     }
 
-    pub(crate) fn add_dependency(&mut self, dependency: Dependency) {
+    pub(super) fn add_dependency(&mut self, dependency: Dependency) {
         self.symbol_table.dependencies.push(dependency);
     }
+
+    /// Records the scope for the current expression
+    pub(super) fn record_expression(&mut self, scope: ScopeId) -> ExpressionId {
+        self.symbol_table.expression_scopes.push(scope)
+    }
 }
 
 #[cfg(test)]

crates/ruff_index/src/slice.rs

@@ -2,7 +2,7 @@ use crate::vec::IndexVec;
 use crate::Idx;
 use std::fmt::{Debug, Formatter};
 use std::marker::PhantomData;
-use std::ops::{Index, IndexMut};
+use std::ops::{Index, IndexMut, Range};
 
 /// A view into contiguous `T`s, indexed by `I` rather than by `usize`.
 #[derive(PartialEq, Eq, Hash)]
@@ -131,6 +131,15 @@ impl<I: Idx, T> Index<I> for IndexSlice<I, T> {
     }
 }
 
+impl<I: Idx, T> Index<Range<I>> for IndexSlice<I, T> {
+    type Output = [T];
+
+    #[inline]
+    fn index(&self, range: Range<I>) -> &[T] {
+        &self.raw[range.start.index()..range.end.index()]
+    }
+}
+
 impl<I: Idx, T> IndexMut<I> for IndexSlice<I, T> {
     #[inline]
     fn index_mut(&mut self, index: I) -> &mut T {
@@ -138,6 +147,13 @@ impl<I: Idx, T> IndexMut<I> for IndexSlice<I, T> {
     }
 }
 
+impl<I: Idx, T> IndexMut<Range<I>> for IndexSlice<I, T> {
+    #[inline]
+    fn index_mut(&mut self, range: Range<I>) -> &mut [T] {
+        &mut self.raw[range.start.index()..range.end.index()]
+    }
+}
+
 impl<'a, I: Idx, T> IntoIterator for &'a IndexSlice<I, T> {
     type IntoIter = std::slice::Iter<'a, T>;
     type Item = &'a T;

crates/ruff_index/src/vec.rs

@@ -69,6 +69,11 @@ impl<I: Idx, T> IndexVec<I, T> {
     pub fn next_index(&self) -> I {
         I::new(self.raw.len())
     }
+
+    #[inline]
+    pub fn shrink_to_fit(&mut self) {
+        self.raw.shrink_to_fit();
+    }
 }
 
 impl<I, T> Debug for IndexVec<I, T>