Freeze emptyArray, make emptyMap and emptySet immutable

src/compiler/core.ts

@@ -13,11 +13,31 @@ import {
 } from "./_namespaces/ts";
 
 /** @internal */
-export const emptyArray: never[] = [] as never[];
+export const emptyArray: never[] = Object.freeze([]) as never[];
 /** @internal */
-export const emptyMap: ReadonlyMap<never, never> = new Map<never, never>();
+export const emptyMap: ReadonlyMap<never, never> = createReadonlyMap();
 /** @internal */
-export const emptySet: ReadonlySet<never> = new Set<never>();
+export const emptySet: ReadonlySet<never> = createReadonlySet();
+
+function createReadonlyMap<K, V>(): ReadonlyMap<K, V> {
+    const map: ReadonlyMap<K, V> = new Map();
+    Object.defineProperties(map, {
+        clear: { value: notImplemented },
+        delete: { value: notImplemented },
+        set: { value: notImplemented },
+    });
+    return Object.freeze(map);
+}
+
+function createReadonlySet<T>(): ReadonlySet<T> {
+    const set: ReadonlySet<T> = new Set();
+    Object.defineProperties(set, {
+        add: { value: notImplemented },
+        clear: { value: notImplemented },
+        delete: { value: notImplemented },
+    });
+    return Object.freeze(set);
+}
 
 /** @internal */
 export function length(array: readonly any[] | undefined): number {

src/compiler/utilities.ts

@@ -568,7 +568,7 @@ import {
 } from "./_namespaces/ts";
 
 /** @internal */
-export const resolvingEmptyArray: never[] = [];
+export const resolvingEmptyArray: never[] = Object.freeze([]) as never[];
 
 /** @internal */
 export const externalHelpersModuleNameText = "tslib";

src/server/utilitiesPublic.ts

@@ -19,7 +19,7 @@ export enum LogLevel {
     verbose,
 }
 
-export const emptyArray: SortedReadonlyArray<never> = createSortedArray<never>();
+export const emptyArray: SortedReadonlyArray<never> = Object.freeze(createSortedArray<never>());
 
 export interface Logger {
     close(): void;