class property inference in constructors not working

[trusktr]

Bug Report

According to this feature we should be able to define properties inside constructors.

🔎 Search Terms

class property inference in constructor not working

🕗 Version & Regression Information

• This is a crash
• This changed between versions ______ and _______
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
• I was unable to test this on prior versions because _______

⏯ Playground Link

Playground link with relevant code

💻 Code

class Foo {
  constructor() {
    this.greeting = 'hello!'; // ERROR
  }
}
var x = new Foo();
console.log(x.greeting); // ERROR

🙁 Actual behavior

TS does not recognize that the property exists

🙂 Expected behavior

TS should recognize that the property exists

[MartinJohns]

According to this feature we should be able to define properties inside constructors.

It does work, but your playground is incorrectly set to TypeScript, not JavaScript. This is currently a JavaScript only feature (the issue title mentions JavaScript). TypeScript support is tracked at #12613.

[trusktr]

I see! That's unexpected that the same code behaves differently based on file type.

[trusktr]

I see! That's unexpected that the same code behaves differently based on file type. I'd expect the difference to be type annotations or no type annotations, but not different forms of type inference.