perf(javascript): reduce retained semantic analysis allocations (#1601)

Reduce retained semantic allocations and memoize lexical scope ancestry while preserving semantic identities. Refs #1065 and #1563; the complete-directory memory failure remains open.

src/domain/javascript/javascriptSemanticState.ts

@@ -60,6 +60,7 @@ export interface JavaScriptSemanticAnalysisState {
   readonly parentsByNode: WeakMap<t.Node, t.Node>;
   readonly scopes: JavaScriptSemanticScopeState[];
   readonly scopesById: Map<string, JavaScriptSemanticScopeState>;
+  /** Scope boundaries and descendant scopes resolved on demand. */
   readonly scopeByNode: WeakMap<t.Node, JavaScriptSemanticScopeState>;
   readonly bindingsById: Map<string, JavaScriptSemanticBindingState>;
   readonly callables: JavaScriptSemanticCallable[];
@@ -94,7 +95,7 @@ export const resolveSemanticBindingState = (
   node: t.Node,
   name: string,
 ): JavaScriptSemanticBindingState | undefined => {
-  let scope = state.scopeByNode.get(node);
+  let scope = semanticScopeForNode(state, node);
   while (scope !== undefined) {
     const binding = scope.bindings.get(name);
     if (binding !== undefined) return binding;
@@ -113,7 +114,7 @@ export const semanticResolutionBlocked = (
   node: t.Node,
   name: string,
 ): boolean => {
-  let scope = state.scopeByNode.get(node);
+  let scope = semanticScopeForNode(state, node);
   while (scope !== undefined) {
     if (scope.bindings.has(name)) return false;
     if (!scope.bindingsComplete) return true;
@@ -125,6 +126,28 @@ export const semanticResolutionBlocked = (
   return false;
 };
 
+const semanticScopeForNode = (
+  state: JavaScriptSemanticAnalysisState,
+  node: t.Node,
+): JavaScriptSemanticScopeState | undefined => {
+  let candidate: t.Node | undefined = node;
+  while (candidate !== undefined) {
+    const scope = state.scopeByNode.get(candidate);
+    if (scope !== undefined) {
+      // Repeated references in a deep expression share this ancestry. Cache
+      // the traversed path without eagerly indexing nodes never resolved.
+      let descendant: t.Node | undefined = node;
+      while (descendant !== undefined && descendant !== candidate) {
+        state.scopeByNode.set(descendant, scope);
+        descendant = state.parentsByNode.get(descendant);
+      }
+      return scope;
+    }
+    candidate = state.parentsByNode.get(candidate);
+  }
+  return undefined;
+};
+
 /** Resolve one name starting from an explicitly selected lexical scope. */
 export const resolveSemanticBindingFromScope = (
   scope: JavaScriptSemanticScopeState,