[TypeScript] const enum should be hoisted

[magic-akari]

Describe the bug

TS Playground

"use strict";
console.log(1 /* A */);

Input code

console.log(Foo.A);

const enum Foo {
    A = 1
}

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false
    },
    "target": "es2022"
  },
  "module": {
    "type": "es6"
  },
  "isModule": true
}

Playground link

https://play.swc.rs/?version=1.2.143&code=H4sIAAAAAAAAA0vOzyvOz0nVy8lP13DLz9dz1LTm4koGCpYopOaV5ioAxRSquRSAwFHBVsGQqxYA10T3ajEAAAA%3D&config=H4sIAAAAAAAAAy2LQQ6AIAwE%2F9KzB8PBA3%2FwEQ1Wg0ElbUk0hL9bjLfdmd0KuwTwFTKyEPckz6l4gwd9MkngmBUGUDG0YhJqVpA3UpuQuNE5MHRcS0nU%2F%2F32qanzKPNvlAu1F9feoEVwAAAA

Expected behavior

see TypeScript output

Actual behavior

No response

Version

1.2.143

Additional context

No response

[magic-akari]

another case:

TypeScript REPL

console.log(Foo.Bar.A)

namespace Foo {
    export const enum Bar {
        A = 1
    }

    console.log("A")
}

console.log(Foo.Bar.B)

namespace Foo {
    export const enum Bar {
        B = 2
    }

    console.log("B")
}

expected output

console.log(1 /* A */);
var Foo;
(function (Foo) {
    console.log("A");
})(Foo || (Foo = {}));
console.log(2 /* B */);
(function (Foo) {
    console.log("B");
})(Foo || (Foo = {}));

[magic-akari]

I think it's partially fixed by #3647. When the const enum is defined and used in the same file, the const enum will be inlined directly, and the hoist issue will disappear.

[kdy1]

Do you think we should close this issue?

[magic-akari]

playground

console.log(Foo.A);
console.log(Bar.Foo.A)

const enum Foo {
    A = 1
}

namespace Bar {
    export const enum Foo {
        A = 1
    }

    console.log("A")
}

console.log(1);
console.log(Bar.Foo.A);
var Foo;
(function(Foo) {
    Foo[Foo["A"] = 1] = "A";
})(Foo || (Foo = {}));
var Bar1;
(function(Bar) {
    let Foo;
    (function(Foo) {
        Foo[Foo["A"] = 1] = "A";
    })(Foo = Bar.Foo || (Bar.Foo = {}));
    console.log("A");
})(Bar1 || (Bar1 = {}));

[magic-akari]

Currently, there is no progress. Furthermore, the new TypeScript 5.0 has made enums even more complex, as opaque computed enum members can now be used.

Reference: microsoft/TypeScript#50528

We cannot completely eliminate const enums like TS, but we can make every effort to replace their references.

[magic-akari]

This issue should be closed.
I will submit a new issue about the complicated enum usage.

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.