Enable noImplicitOverride in local builds.

apps/api-documenter/src/markdown/CustomMarkdownEmitter.ts

@@ -33,7 +33,7 @@ export class CustomMarkdownEmitter extends MarkdownEmitter {
     this._apiModel = apiModel;
   }
 
-  public emit(
+  public override emit(
     stringBuilder: StringBuilder,
     docNode: DocNode,
     options: ICustomMarkdownEmitterOptions

apps/api-documenter/src/plugin/MarkdownDocumenterFeature.ts

@@ -75,7 +75,7 @@ const uuidMarkdownDocumenterFeature: string = '34196154-9eb3-4de0-a8c8-7e9539dfe
  */
 export class MarkdownDocumenterFeature extends PluginFeature {
   /** {@inheritdoc PluginFeature.context} */
-  public context!: MarkdownDocumenterFeatureContext;
+  public override context!: MarkdownDocumenterFeatureContext;
 
   /**
    * This event occurs before each markdown file is written.  It provides an opportunity to customize the
@@ -94,7 +94,7 @@ export class MarkdownDocumenterFeature extends PluginFeature {
     // (implemented by child class)
   }
 
-  public static [Symbol.hasInstance](instance: object): boolean {
+  public static override [Symbol.hasInstance](instance: object): boolean {
     return TypeUuid.isInstanceOf(instance, uuidMarkdownDocumenterFeature);
   }
 }

build-tests/api-documenter-scenarios/src/inheritedMembers/index.ts

@@ -41,22 +41,22 @@ export class Class2<T> extends Namespace1.Class3 {
 
   /** Some method. Overrides `Class3.someMethod`. */
   // eslint-disable-next-line @typescript-eslint/explicit-member-accessibility
-  someMethod(x: boolean): void {}
+  override someMethod(x: boolean): void {}
 }
 
 /** @public */
 export class Class1 extends Class2<number> {
   /** A second prop. Overrides `Class2.secondProp`. */
   // eslint-disable-next-line @typescript-eslint/explicit-member-accessibility
-  secondProp: boolean;
+  override secondProp: boolean;
 
   /** A fourth prop */
   // eslint-disable-next-line @typescript-eslint/explicit-member-accessibility
   fourthProp: number;
 
   /** Some overload. Overrides `Class3.someOverload`. */
   // eslint-disable-next-line @typescript-eslint/explicit-member-accessibility
-  someOverload(x: boolean | string): void {}
+  override someOverload(x: boolean | string): void {}
 }
 
 /** @public */

build-tests/api-extractor-test-05/dist/tsdoc-metadata.json

@@ -5,7 +5,7 @@
   "toolPackages": [
     {
       "packageName": "@microsoft/api-extractor",
-      "packageVersion": "7.58.10"
+      "packageVersion": "7.58.11"
     }
   ]
 }

common/changes/@microsoft/api-documenter/enable-noImplicitOverride_2026-07-18-00-45-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "type": "none",
+      "packageName": "@microsoft/api-documenter"
+    }
+  ],
+  "packageName": "@microsoft/api-documenter",
+  "email": "iclanton@users.noreply.github.com"
+}

common/changes/@microsoft/rush/enable-noImplicitOverride_2026-07-18-00-45-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "type": "none",
+      "packageName": "@microsoft/rush"
+    }
+  ],
+  "packageName": "@microsoft/rush",
+  "email": "iclanton@users.noreply.github.com"
+}

common/changes/@rushstack/hashed-folder-copy-plugin/enable-noImplicitOverride_2026-07-18-00-45-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "type": "none",
+      "packageName": "@rushstack/hashed-folder-copy-plugin"
+    }
+  ],
+  "packageName": "@rushstack/hashed-folder-copy-plugin",
+  "email": "iclanton@users.noreply.github.com"
+}

common/changes/@rushstack/set-webpack-public-path-plugin/enable-noImplicitOverride_2026-07-18-00-45-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "type": "none",
+      "packageName": "@rushstack/set-webpack-public-path-plugin"
+    }
+  ],
+  "packageName": "@rushstack/set-webpack-public-path-plugin",
+  "email": "iclanton@users.noreply.github.com"
+}

common/changes/@rushstack/stream-collator/enable-noImplicitOverride_2026-07-18-00-45-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "type": "none",
+      "packageName": "@rushstack/stream-collator"
+    }
+  ],
+  "packageName": "@rushstack/stream-collator",
+  "email": "iclanton@users.noreply.github.com"
+}

libraries/rush-lib/src/api/LastInstallFlag.ts

@@ -89,7 +89,7 @@ export class LastInstallFlag extends FlagFile<Partial<ILastInstallFlagJson>> {
   /**
    * Returns true if the file exists and the contents match the current state.
    */
-  public async isValidAsync(): Promise<boolean> {
+  public override async isValidAsync(): Promise<boolean> {
     return await this._isValidAsync(false, {});
   }
 

libraries/rush-lib/src/api/SaveCallbackPackageJsonEditor.ts

@@ -24,7 +24,7 @@ export class SaveCallbackPackageJsonEditor extends PackageJsonEditor {
     return new SaveCallbackPackageJsonEditor(options);
   }
 
-  public async saveIfModifiedAsync(): Promise<boolean> {
+  public override async saveIfModifiedAsync(): Promise<boolean> {
     const modified: boolean = await super.saveIfModifiedAsync();
     if (this._onSaved) {
       this._onSaved(this.saveToObject());

libraries/rush-lib/src/cli/RushCommandLineParser.ts

@@ -233,7 +233,7 @@ export class RushCommandLineParser extends CommandLineParser {
     this.telemetry?.flush();
   }
 
-  public async executeAsync(args?: string[]): Promise<boolean> {
+  public override async executeAsync(args?: string[]): Promise<boolean> {
     // debugParameter will be correctly parsed during super.executeAsync(), so manually parse here.
     this._terminalProvider.verboseEnabled = this._terminalProvider.debugEnabled =
       process.argv.indexOf('--debug') >= 0;

libraries/rush-lib/src/cli/actions/BaseRushAction.ts

@@ -115,7 +115,7 @@ export abstract class BaseRushAction extends BaseConfiglessRushAction {
     return this._eventHooksManager;
   }
 
-  protected readonly rushConfiguration!: RushConfiguration;
+  protected override readonly rushConfiguration!: RushConfiguration;
 
   protected override async onExecuteAsync(): Promise<void> {
     if (!this.rushConfiguration) {

libraries/rush-lib/src/cli/actions/UpdateAction.ts

@@ -71,7 +71,7 @@ export class UpdateAction extends BaseInstallAction {
     });
   }
 
-  protected async runAsync(): Promise<void> {
+  protected override async runAsync(): Promise<void> {
     await this.parser.pluginManager.updateAsync();
 
     if (this.parser.pluginManager.error) {

libraries/rush-lib/src/logic/installManager/WorkspaceInstallManager.ts

@@ -550,7 +550,7 @@ export class WorkspaceInstallManager extends BaseInstallManager {
     return { shrinkwrapIsUpToDate, shrinkwrapWarnings };
   }
 
-  protected async canSkipInstallAsync(
+  protected override async canSkipInstallAsync(
     lastModifiedDate: Date,
     subspace: Subspace,
     variant: string | undefined
@@ -887,7 +887,11 @@ export class WorkspaceInstallManager extends BaseInstallManager {
    * Used when invoking the NPM tool.  Appends the common configuration options
    * to the command-line.
    */
-  protected pushConfigurationArgs(args: string[], options: IInstallManagerOptions, subspace: Subspace): void {
+  protected override pushConfigurationArgs(
+    args: string[],
+    options: IInstallManagerOptions,
+    subspace: Subspace
+  ): void {
     super.pushConfigurationArgs(args, options, subspace);
 
     // Add workspace-specific args

libraries/rush-lib/src/logic/npm/NpmPackage.ts

@@ -91,7 +91,10 @@ export class NpmPackage extends BasePackage {
    * @param targetFolderName - Filename where it should have been installed
    *        Example: `C:\MyRepo\common\temp\node_modules\@rush-temp\project1`
    */
-  public static createVirtualTempPackage(packageJsonFilename: string, installFolderName: string): NpmPackage {
+  public static override createVirtualTempPackage(
+    packageJsonFilename: string,
+    installFolderName: string
+  ): NpmPackage {
     const packageJson: IPackageJson = JsonFile.load(packageJsonFilename);
     const npmPackage: readPackageTree.Node = {
       children: [],

libraries/rush-lib/src/logic/operations/OperationError.ts

@@ -14,11 +14,11 @@ export class OperationError extends Error {
     this._type = type;
   }
 
-  public get message(): string {
+  public override get message(): string {
     return `[${this._type}] '${super.message}'`;
   }
 
-  public toString(): string {
+  public override toString(): string {
     return this.message;
   }
 }

libraries/rush-lib/src/logic/operations/ProjectLogWritable.ts

@@ -119,7 +119,7 @@ export class JsonLFileWritable extends TerminalWritable {
     this._writer.write(JSON.stringify(chunk) + '\n');
   }
 
-  protected onClose(): void {
+  protected override onClose(): void {
     if (this._writer) {
       try {
         this._writer.close();
@@ -176,7 +176,7 @@ export class SplitLogFileWritable extends TerminalWritable {
     }
   }
 
-  protected onClose(): void {
+  protected override onClose(): void {
     if (this._logWriter) {
       try {
         this._logWriter.close();

libraries/rush-lib/src/logic/setup/TerminalInput.ts

@@ -35,7 +35,7 @@ class YesNoKeyboardLoop extends KeyboardLoop {
     this.options = options;
   }
 
-  protected onStart(): void {
+  protected override onStart(): void {
     this.stderr.write(Colorize.green('==>') + ' ');
     this.stderr.write(Colorize.bold(this.options.message));
     let optionSuffix: string = '';
@@ -53,7 +53,7 @@ class YesNoKeyboardLoop extends KeyboardLoop {
     this.stderr.write(' ' + Colorize.bold(optionSuffix) + ' ');
   }
 
-  protected onKeypress(character: string, key: readline.Key): void {
+  protected override onKeypress(character: string, key: readline.Key): void {
     if (this.result !== undefined) {
       return;
     }
@@ -102,7 +102,7 @@ class PasswordKeyboardLoop extends KeyboardLoop {
     return this.stderr.columns ? this.stderr.columns : 80;
   }
 
-  protected onStart(): void {
+  protected override onStart(): void {
     this.result = '';
 
     readline.cursorTo(this.stderr, 0);
@@ -118,7 +118,7 @@ class PasswordKeyboardLoop extends KeyboardLoop {
     this._startX = AnsiEscape.removeCodes(line).length % this._getLineWrapWidth();
   }
 
-  protected onKeypress(character: string, key: readline.Key): void {
+  protected override onKeypress(character: string, key: readline.Key): void {
     switch (key.name) {
       case 'enter':
       case 'return':

libraries/rush-lib/src/logic/test/BaseInstallManager.test.ts

@@ -36,7 +36,12 @@ class FakeBaseInstallManager extends BaseInstallManager {
   protected postInstallAsync(): Promise<void> {
     return Promise.resolve();
   }
-  public pushConfigurationArgs(args: string[], options: IInstallManagerOptions, subspace: Subspace): void {
+
+  public override pushConfigurationArgs(
+    args: string[],
+    options: IInstallManagerOptions,
+    subspace: Subspace
+  ): void {
     return super.pushConfigurationArgs(args, options, subspace);
   }
 }

libraries/rushell/src/AstNode.ts

@@ -78,7 +78,7 @@ export abstract class AstBaseNode {
  * Represents a complete script that can be executed.
  */
 export class AstScript extends AstBaseNode {
-  public readonly kind: AstKind.Script = AstKind.Script;
+  public override readonly kind: AstKind.Script = AstKind.Script;
 
   public body: AstNode | undefined;
 
@@ -93,7 +93,7 @@ export class AstScript extends AstBaseNode {
  * Represents the "&&" operator, which is used to join two individual commands.
  */
 export class AstAndIf extends AstBaseNode {
-  public readonly kind: AstKind.AndIf = AstKind.AndIf;
+  public override readonly kind: AstKind.AndIf = AstKind.AndIf;
 
   /**
    * The command that executes first, and always.
@@ -119,7 +119,7 @@ export class AstAndIf extends AstBaseNode {
  * Represents a command.  For example, the name of an executable to be started.
  */
 export class AstCommand extends AstBaseNode {
-  public readonly kind: AstKind.Command = AstKind.Command;
+  public override readonly kind: AstKind.Command = AstKind.Command;
 
   public commandPath: AstCompoundWord | undefined;
   public arguments: AstCompoundWord[] = [];
@@ -136,7 +136,7 @@ export class AstCommand extends AstBaseNode {
  * Represents a compound word, e.g. "--the-thing" or "./the/thing".
  */
 export class AstCompoundWord extends AstBaseNode {
-  public readonly kind: AstKind.CompoundWord = AstKind.CompoundWord;
+  public override readonly kind: AstKind.CompoundWord = AstKind.CompoundWord;
 
   public readonly parts: AstNode[] = [];
 
@@ -149,7 +149,7 @@ export class AstCompoundWord extends AstBaseNode {
  * Represents an environment variable expansion expression, e.g. "${VARIABLE}"
  */
 export class AstVariableExpansion extends AstBaseNode {
-  public readonly kind: AstKind.VariableExpansion = AstKind.VariableExpansion;
+  public override readonly kind: AstKind.VariableExpansion = AstKind.VariableExpansion;
 
   protected override collectChildNodesInto(nodes: AstNode[]): void {
     // no children
@@ -160,7 +160,7 @@ export class AstVariableExpansion extends AstBaseNode {
  * Represents some plain text.
  */
 export class AstText extends AstBaseNode {
-  public readonly kind: AstKind.Text = AstKind.Text;
+  public override readonly kind: AstKind.Text = AstKind.Text;
 
   public token: Token | undefined;
 

libraries/stream-collator/src/CollatedWriter.ts

@@ -50,7 +50,7 @@ export class CollatedWriter extends TerminalWritable {
   }
 
   /** {@inheritDoc @rushstack/terminal#TerminalWritable.onClose} */
-  public onClose(): void {
+  public override onClose(): void {
     this._collator._writerClose(this, this._bufferedChunks);
   }
 

repo-scripts/doc-plugin-rush-stack/src/RushStackFeature.ts

@@ -25,12 +25,12 @@ interface INavigationFile {
 export class RushStackFeature extends MarkdownDocumenterFeature {
   private _apiItemsWithPages: Set<ApiItem> = new Set<ApiItem>();
 
-  public onInitialized(): void {
+  public override onInitialized(): void {
     // eslint-disable-next-line no-console
     console.log('RushStackFeature: onInitialized()');
   }
 
-  public onBeforeWritePage(eventArgs: IMarkdownDocumenterFeatureOnBeforeWritePageArgs): void {
+  public override onBeforeWritePage(eventArgs: IMarkdownDocumenterFeatureOnBeforeWritePageArgs): void {
     // Add the Jekyll header
     const header: string = [
       '---',
@@ -45,7 +45,7 @@ export class RushStackFeature extends MarkdownDocumenterFeature {
     this._apiItemsWithPages.add(eventArgs.apiItem);
   }
 
-  public onFinished(eventArgs: IMarkdownDocumenterFeatureOnFinishedArgs): void {
+  public override onFinished(eventArgs: IMarkdownDocumenterFeatureOnFinishedArgs): void {
     const navigationFile: INavigationFile = {
       api_nav: [
         {

rigs/local-node-rig/profiles/default/tsconfig-base.json

@@ -6,6 +6,7 @@
   "compilerOptions": {
     "resolveJsonModule": true,
     "isolatedModules": true,
+    "noImplicitOverride": true,
     "target": "es2018",
 
     "outDir": "${configDir}/lib-commonjs",

rigs/local-web-rig/profiles/app/tsconfig-base.json

@@ -6,6 +6,7 @@
   "compilerOptions": {
     "resolveJsonModule": true,
     "isolatedModules": true,
+    "noImplicitOverride": true,
 
     "target": "es2017",
     "lib": [

rigs/local-web-rig/profiles/library/tsconfig-base.json

@@ -6,6 +6,7 @@
   "compilerOptions": {
     "resolveJsonModule": true,
     "isolatedModules": true,
+    "noImplicitOverride": true,
 
     "outDir": "${configDir}/lib-esm",
     "declarationDir": "${configDir}/lib-dts",