Improve query cache efficiency

crates/ide/src/def/liveness.rs

@@ -180,7 +180,7 @@ mod tests {
         let (db, f) = TestDB::from_fixture(fixture).unwrap();
         assert_eq!(f.files().len(), 1);
         let file = f.files()[0];
-        assert_eq!(db.module(file).diagnostics(), Vec::new(), "Lower error");
+        assert_eq!(db.source_map(file).diagnostics(), Vec::new(), "Lower error");
         let expect = f.markers().iter().map(|p| p.pos).collect::<Vec<_>>();
         let mut got = db
             .liveness_check(file)

crates/ide/src/def/lower.rs

@@ -26,7 +26,6 @@ pub(super) fn lower(
             names: Arena::new(),
             // Placeholder.
             entry_expr: ExprId::from_raw(0.into()),
-            diagnostics: Vec::new(),
         },
         source_map: ModuleSourceMap::default(),
     };
@@ -60,7 +59,7 @@ impl LowerCtx<'_> {
     }
 
     fn diagnostic(&mut self, diag: Diagnostic) {
-        self.module.diagnostics.push(diag);
+        self.source_map.diagnostics.push(diag);
     }
 
     fn lower_expr_opt(&mut self, expr: Option<ast::Expr>) -> ExprId {
@@ -603,11 +602,12 @@ mod tests {
     fn check_lower(src: &str, expect: Expect) {
         let (db, file_id) = TestDB::single_file(src).unwrap();
         let module = db.module(file_id);
+        let source_map = db.source_map(file_id);
         let mut got = String::new();
-        for diag in module.diagnostics() {
+        for diag in source_map.diagnostics() {
             writeln!(got, "{}", diag.debug_display()).unwrap();
         }
-        if !module.diagnostics.is_empty() {
+        if !source_map.diagnostics.is_empty() {
             writeln!(got).unwrap();
         }
         for (i, e) in module.exprs.iter() {
@@ -640,9 +640,8 @@ mod tests {
     #[track_caller]
     fn check_error(src: &str, expect: Expect) {
         let (db, file_id) = TestDB::single_file(src).unwrap();
-        let module = db.module(file_id);
         let mut got = String::new();
-        for diag in module.diagnostics() {
+        for diag in db.source_map(file_id).diagnostics() {
             writeln!(got, "{}", diag.debug_display()).unwrap();
         }
         expect.assert_eq(&got);

crates/ide/src/def/mod.rs

@@ -108,7 +108,6 @@ pub struct Module {
     exprs: Arena<Expr>,
     names: Arena<Name>,
     entry_expr: ExprId,
-    diagnostics: Vec<Diagnostic>,
 }
 
 pub type ExprId = Idx<Expr>;
@@ -132,17 +131,12 @@ impl Module {
     pub fn shrink_to_fit(&mut self) {
         self.exprs.shrink_to_fit();
         self.names.shrink_to_fit();
-        self.diagnostics.shrink_to_fit();
     }
 
     pub fn entry_expr(&self) -> ExprId {
         self.entry_expr
     }
 
-    pub fn diagnostics(&self) -> &[Diagnostic] {
-        &self.diagnostics
-    }
-
     pub fn exprs(&self) -> impl Iterator<Item = (ExprId, &'_ Expr)> + ExactSizeIterator + '_ {
         self.exprs.iter()
     }
@@ -184,6 +178,9 @@ pub struct ModuleSourceMap {
     expr_map_rev: HashMap<ExprId, AstPtr>,
     name_map: HashMap<AstPtr, NameId>,
     name_map_rev: ArenaMap<NameId, Vec<AstPtr>>,
+
+    // This contains locations, thus is quite volatile.
+    diagnostics: Vec<Diagnostic>,
 }
 
 impl ModuleSourceMap {
@@ -192,6 +189,7 @@ impl ModuleSourceMap {
         self.expr_map_rev.shrink_to_fit();
         self.name_map.shrink_to_fit();
         self.name_map_rev.shrink_to_fit();
+        self.diagnostics.shrink_to_fit();
     }
 
     pub fn expr_for_node(&self, node: AstPtr) -> Option<ExprId> {
@@ -213,6 +211,10 @@ impl ModuleSourceMap {
             .flatten()
             .cloned()
     }
+
+    pub fn diagnostics(&self) -> &[Diagnostic] {
+        &self.diagnostics
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]

crates/ide/src/ide/diagnostics.rs

@@ -8,8 +8,8 @@ pub(crate) fn diagnostics(db: &dyn DefDatabase, file: FileId) -> Vec<Diagnostic>
     diags.extend(parse.errors().iter().map(|&err| Diagnostic::from(err)));
 
     // Lowering.
-    let module = db.module(file);
-    diags.extend(module.diagnostics().iter().cloned());
+    let source_map = db.source_map(file);
+    diags.extend(source_map.diagnostics().iter().cloned());
 
     // Name resolution.
     diags.extend(db.name_resolution(file).to_diagnostics(db, file));

crates/ide/src/ide/mod.rs

@@ -33,6 +33,8 @@ pub use rename::RenameResult;
 pub use symbol_hierarchy::SymbolTree;
 pub use syntax_highlighting::{HlAttrField, HlKeyword, HlOperator, HlPunct, HlRange, HlTag};
 
+pub const DEFAULT_LRU_CAP: usize = 128;
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct NavigationTarget {
     pub file_id: FileId,
@@ -72,6 +74,10 @@ impl Default for RootDatabase {
         let mut db = Self {
             storage: salsa::Storage::default(),
         };
+
+        crate::def::ParseQuery
+            .in_db_mut(&mut db)
+            .set_lru_capacity(DEFAULT_LRU_CAP);
         db.set_flake_graph_with_durability(Default::default(), Durability::MEDIUM);
         db
     }