Allow Object.defineProperty() to definitely assign properties

Suggestion

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

It would be nice if Object.defineProperty() and Object.defineProperties() calls could be read via the constructor to definitely assign class properties.

📃 Motivating Example

https://www.typescriptlang.org/play?ssl=12&ssc=2&pln=1&pc=1#code/MYGwhgzhAEDiBOBTRAXR9oG8BQ0-QDswBbRALmghXgEsCBzAbl33qVTvoqtoef2jAA9gR4BXYCiHwAFEVLdqnAJRYWAvCgAWNCADp5iaAF5CJRPw14A8gCMAVokl6AJogBmdRAAV4QgA7oKACeMtq6ADTQAERsyCic0VE4Vlb0qDKqKak5SChi8ATQAAZaiCAgQtAAJJiGAL7F6jnQ9c0C9cqWeG31QA

class Greeter {
    name: string;
    greeting: string;
    constructor(name: string) {
        this.name = name;
        Object.defineProperty(this, "greeting", {
            get() {
                return `hello ${name}`
            }
        });
    }
}

Currently the greeting property in the class will cause the error Property 'greeting' has no initializer and is not definitely assigned in the constructor.

💻 Use Cases

This is not a big deal because we can use a “definite assignment assertion“ (!) after the greeting property identifier, but it would be nice for TypeScript to be aware of these defineProperty calls.

🔍 Search Terms

constructor, Object.defineProperty, Object.defineProperties, definitely assigned, strictPropertyInitialization, definite assignment operator
Property has no initializer and is not definitely assigned in the constructor.

This is potentially a duplicate of the following issues:

• https://github.com/microsoft/TypeScript/issues/28694 The same issue, but focused on JavaScript source files.
• https://github.com/microsoft/TypeScript/issues/38115 Might be a duplicate of this issue, but the phrasing of this issue is a little less clear to me based on the examples.

Feel free to close as duplicate!

Start by running the linked TypeScript Playground example and compare the reported strictPropertyInitialization error with the constructor's Object.defineProperty call. Trace how Object.defineProperty and Object.defineProperties are handled during type checking and define the accepted semantics; done means the motivating example is checked without the error while existing behavior remains unchanged.