review comments

Cargo.toml

@@ -127,7 +127,6 @@ strum_macros = { version = "0.26.0" }
 syn = { version = "2.0.55" }
 tempfile = { version = "3.9.0" }
 test-case = { version = "3.3.1" }
-textwrap = { version = "0.16.1" }
 thiserror = { version = "1.0.58" }
 tikv-jemallocator = { version = "0.6.0" }
 toml = { version = "0.8.11" }

crates/red_knot_python_semantic/Cargo.toml

@@ -15,6 +15,7 @@ red_knot_module_resolver = { workspace = true }
 ruff_db = { workspace = true }
 ruff_index = { workspace = true }
 ruff_python_ast = { workspace = true }
+ruff_python_trivia = { workspace = true }
 ruff_text_size = { workspace = true }
 
 bitflags = { workspace = true }
@@ -27,7 +28,6 @@ hashbrown = { workspace = true }
 [dev-dependencies]
 anyhow = { workspace = true }
 ruff_python_parser = { workspace = true }
-textwrap = { workspace = true }
 
 [lints]
 workspace = true

crates/red_knot_python_semantic/src/db.rs

@@ -47,6 +47,7 @@ pub(crate) mod tests {
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
     use ruff_db::{Db as SourceDb, Jar as SourceJar, Upcast};
+    use ruff_python_trivia::textwrap;
 
     use super::{Db, Jar};
 
@@ -88,6 +89,12 @@ pub(crate) mod tests {
         pub(crate) fn clear_salsa_events(&mut self) {
             self.take_salsa_events();
         }
+
+        /// Write auto-dedented text to a file.
+        pub(crate) fn write_dedented(&mut self, path: &str, content: &str) -> anyhow::Result<()> {
+            self.write_file(path, textwrap::dedent(content))?;
+            Ok(())
+        }
     }
 
     impl DbWithTestSystem for TestDb {

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -15,15 +15,15 @@ use crate::semantic_index::expression::Expression;
 use crate::semantic_index::symbol::{
     FileScopeId, NodeWithScopeKey, NodeWithScopeRef, Scope, ScopeId, ScopedSymbolId, SymbolTable,
 };
-use crate::semantic_index::usedef::UseDefMap;
+use crate::semantic_index::use_def::UseDefMap;
 use crate::Db;
 
 pub mod ast_ids;
 mod builder;
 pub mod definition;
 pub mod expression;
 pub mod symbol;
-pub mod usedef;
+pub mod use_def;
 
 type SymbolMap = hashbrown::HashMap<ScopedSymbolId, (), ()>;
 
@@ -188,6 +188,9 @@ impl<'db> SemanticIndex<'db> {
     }
 
     /// Returns the [`Expression`] ingredient for an expression node.
+    /// Panics if we have no expression ingredient for that node. We can only call this method for
+    /// standalone-inferable expressions, which we call `add_standalone_expression` for in
+    /// [`SemanticIndexBuilder`].
     pub(crate) fn expression(
         &self,
         expression_key: impl Into<ExpressionNodeKey>,

crates/red_knot_python_semantic/src/semantic_index/builder.rs

@@ -21,7 +21,7 @@ use crate::semantic_index::symbol::{
     FileScopeId, NodeWithScopeKey, NodeWithScopeRef, Scope, ScopeId, ScopedSymbolId, SymbolFlags,
     SymbolTableBuilder,
 };
-use crate::semantic_index::usedef::{FlowSnapshot, UseDefMapBuilder};
+use crate::semantic_index::use_def::{FlowSnapshot, UseDefMapBuilder};
 use crate::semantic_index::SemanticIndex;
 use crate::Db;
 
@@ -176,7 +176,8 @@ impl<'db> SemanticIndexBuilder<'db> {
 
         self.definitions_by_node
             .insert(definition_node.key(), definition);
-        self.current_use_def_map().record_def(symbol, definition);
+        self.current_use_def_map()
+            .record_definition(symbol, definition);
 
         definition
     }

crates/red_knot_python_semantic/src/semantic_index/usedef.rs → crates/red_knot_python_semantic/src/semantic_index/use_def.rs

@@ -44,7 +44,7 @@ struct Definitions {
 impl Default for Definitions {
     fn default() -> Self {
         Self {
-            definitions: 0..0,
+            definitions: Range::default(),
             may_be_unbound: true,
         }
     }
@@ -60,7 +60,7 @@ pub(super) struct UseDefMapBuilder<'db> {
 
     definitions_by_use: IndexVec<ScopedUseId, Definitions>,
 
-    // builder state: currently visible definitions for each symbol
+    /// builder state: currently visible definitions for each symbol
     definitions_by_symbol: IndexVec<ScopedSymbolId, Definitions>,
 }
 
@@ -78,7 +78,11 @@ impl<'db> UseDefMapBuilder<'db> {
         debug_assert_eq!(symbol, new_symbol);
     }
 
-    pub(super) fn record_def(&mut self, symbol: ScopedSymbolId, definition: Definition<'db>) {
+    pub(super) fn record_definition(
+        &mut self,
+        symbol: ScopedSymbolId,
+        definition: Definition<'db>,
+    ) {
         let def_idx = self.all_definitions.len();
         self.all_definitions.push(definition);
         self.definitions_by_symbol[symbol] = Definitions {
@@ -110,7 +114,7 @@ impl<'db> UseDefMapBuilder<'db> {
 
     pub(super) fn merge(&mut self, state: &FlowSnapshot) {
         for (symbol_id, to_merge) in state.definitions_by_symbol.iter_enumerated() {
-            let current = self.definitions_by_symbol.get_mut(symbol_id).unwrap();
+            let current = &mut self.definitions_by_symbol[symbol_id];
             // if the symbol can be unbound in either predecessor, it can be unbound
             current.may_be_unbound |= to_merge.may_be_unbound;
             // merge the definition ranges