fix(cdk/a11y): allow mixed types to be passed into setActiveItem (#31462)

This is a follow-up to #31371 (comment). `ListKeyManager.setActiveItem` supports both a reference to an item or an index, however there's no override that allows `T | number` which can be inconvenient.

These changes add extra overrides to resolve the issue.

Author: crisbeto

goldens/cdk/a11y/index.api.md

@@ -37,6 +37,7 @@ export class A11yModule {
 export class ActiveDescendantKeyManager<T> extends ListKeyManager<Highlightable & T> {
     setActiveItem(index: number): void;
     setActiveItem(item: T): void;
+    setActiveItem(item: T | number): void;
 }
 
 // @public
@@ -169,6 +170,7 @@ export interface FocusableOption extends ListKeyManagerOption {
 export class FocusKeyManager<T> extends ListKeyManager<FocusableOption & T> {
     setActiveItem(index: number): void;
     setActiveItem(item: T): void;
+    setActiveItem(item: T | number): void;
     setFocusOrigin(origin: FocusOrigin): this;
 }
 
@@ -366,6 +368,7 @@ export class ListKeyManager<T extends ListKeyManagerOption> {
     onKeydown(event: KeyboardEvent): void;
     setActiveItem(index: number): void;
     setActiveItem(item: T): void;
+    setActiveItem(item: T | number): void;
     setFirstItemActive(): void;
     setLastItemActive(): void;
     setNextItemActive(): void;

src/cdk/a11y/key-manager/activedescendant-key-manager.ts

@@ -37,6 +37,13 @@ export class ActiveDescendantKeyManager<T> extends ListKeyManager<Highlightable
    * @param item Item to be set as active.
    */
   override setActiveItem(item: T): void;
+  /**
+   * Sets the active item to the item to the specified one and adds the
+   * active styles to the it. Also removes active styles from the
+   * previously active item.
+   * @param item Item to be set as active.
+   */
+  override setActiveItem(item: T | number): void;
 
   override setActiveItem(index: any): void {
     if (this.activeItem) {

src/cdk/a11y/key-manager/focus-key-manager.ts

@@ -44,6 +44,12 @@ export class FocusKeyManager<T> extends ListKeyManager<FocusableOption & T> {
    */
   override setActiveItem(item: T): void;
 
+  /**
+   * Sets the active item to the item that is specified and focuses it.
+   * @param item Item to be set as active.
+   */
+  override setActiveItem(item: T | number): void;
+
   override setActiveItem(item: any): void {
     super.setActiveItem(item);
 

src/cdk/a11y/key-manager/list-key-manager.ts

@@ -203,6 +203,12 @@ export class ListKeyManager<T extends ListKeyManagerOption> {
    */
   setActiveItem(item: T): void;
 
+  /**
+   * Sets the active item to the specified item.
+   * @param item The item to be set as active.
+   */
+  setActiveItem(item: T | number): void;
+
   setActiveItem(item: any): void {
     const previousActiveItem = this._activeItem();
 

src/cdk/menu/menu-base.ts

@@ -146,13 +146,7 @@ export abstract class CdkMenuBase
    * @param item The index of the item to be set as active, or the CdkMenuItem instance.
    */
   setActiveMenuItem(item: number | CdkMenuItem) {
-    if (this.keyManager) {
-      if (typeof item === 'number') {
-        this.keyManager.setActiveItem(item);
-      } else {
-        this.keyManager.setActiveItem(item);
-      }
-    }
+    this.keyManager?.setActiveItem(item);
   }
 
   /** Gets the tabindex for this menu. */