Fix invalid decorator examples in lib.decorators.d.ts

The `@example` blocks on `ClassDecoratorContext.addInitializer` and
`ClassMethodDecoratorContext.addInitializer` referenced two types that do
not exist: `ClassDecoratorFunction` and `ClassMethodDecoratorFunction`.
The second example was also syntactically invalid (a function expression
without `=>`), so neither snippet could be copied into an editor.

Rewrite both snippets so they type check under `--strict` using the
decorator context types that actually ship in this file.

Fixes #54338
Fixes #54099

Author: wfatih

tsc/internal/bundled/libs/lib.decorators.d.ts

@@ -53,16 +53,19 @@ interface ClassDecoratorContext<
      *
      * @example
      * ```ts
-     * function customElement(name: string): ClassDecoratorFunction {
-     *   return (target, context) => {
+     * function customElement(name: string) {
+     *   return <Class extends CustomElementConstructor>(
+     *     target: Class,
+     *     context: ClassDecoratorContext<Class>,
+     *   ) => {
      *     context.addInitializer(function () {
      *       customElements.define(name, this);
      *     });
-     *   }
+     *   };
      * }
      *
      * @customElement("my-element")
-     * class MyElement {}
+     * class MyElement extends HTMLElement {}
      * ```
      */
     addInitializer(initializer: (this: Class) => void): void;
@@ -114,10 +117,14 @@ interface ClassMethodDecoratorContext<
      *
      * @example
      * ```ts
-     * const bound: ClassMethodDecoratorFunction = (value, context) {
+     * function bound<This, Value extends (...args: any) => any>(
+     *   value: Value,
+     *   context: ClassMethodDecoratorContext<This, Value>,
+     * ) {
      *   if (context.private) throw new TypeError("Not supported on private methods.");
-     *   context.addInitializer(function () {
-     *     this[context.name] = this[context.name].bind(this);
+     *   context.addInitializer(function (this: This) {
+     *     const self = this as Record<PropertyKey, any>;
+     *     self[context.name] = self[context.name].bind(this);
      *   });
      * }
      *