Missing use-before-defined error for enums

[asurance]

TypeScript Version: 3.5.1
Code

class test {
  static log() {
    console.log(Const.value);
  }
}
test.log();
enum Const {
  value = 1
}

class test {
  static instance = new test();
  constructor() {
    console.log(Const.value);
  }
}
enum Const {
  value = 1
}

Expected behavior:
Run with no error
Actual behavior:
Uncaught TypeError: Cannot read property 'value' of undefined
Playground Link:
http://www.typescriptlang.org/play/index.html#code/MYGwhgzhAEAuCmFbQN4FgBQ1pLLAlsNCAPYDmAFAJSqbbbAkB2EJI8AdKZQMLNIcAbmBABXeFQDcdaAF9M8jAgHdq0jPCaiAttD4tk6LNGFj40ALzQAjAsxA
http://www.typescriptlang.org/play/index.html#code/MYGwhgzhAEAuCmFbQN4FgBQ1pLLAlsNPgHa4nDzQC80J8A7nIrABQCUA3JtsAPZlYAJwCuwWHyEdUPbNH5k+IeADoQfAOasAwgKQqAbmBAj4XWQF9MVjPBIiAttF2CZWaEZNVaARmuYgA
More Info
Use const enum or use enum before class declaration can avoid this problem。
Maybe enum object should be moved ahead of file after complied。

[AnyhowStep]

Function hoisting is a language feature but I'm not sure if enum hoisting should be ¯\_(ツ)_/¯

You're running into this problem because variables are hoisted differently from functions.

Sure, JS will let you refer to Const before it's defined, but it will quite naturally have the value undefined until it is defined later.

---

If anything, I would rather usages of Const before its definition to give a compile error.

But I'm sure the general problem of determining if something is used before its definition is probably not easy.

That constructor would be fine if it was invoked after the definition of Const. But your static property forces it to be invoked before.

---

A good workaround is to just move your enum to its own file and export it. Then import the enum whenever you need it.

[AlCalzone]

I used to have my enums at the bottom of source files but when I switched to typescript-eslint all those locations were marked as errors. Now I know why.

[RyanCavanaugh]

TypeScript doesn't enforce TDZ violations inside function bodies since this isn't really detectable apart from the cases where it always fails immediately anyway

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.