[Feature] make generated codes from enum could be minified when not used

Search Terms

For now TypeScript will transform enum from

enum Test {
    Key = 1
}

to

var Test;
(function (Test) {
    Test[Test["Key"] = 1] = "Key";
})(Test || (Test = {}));

This result is not friendly for uglyify or tree-shaking.
When Test is not be used, the generated code block always remain as dead codes.

Suggestion

prefer to generate codes below:

var Test = /*#__PURE__*/(function () {
    var e = {}
    e[e["Key"] = 1] = "Key";
    return e
})();

Examples

The suggestion version will be removed.

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. new expression-level syntax)

ソースファイル、テスト、エントリポイントのいずれも指定されていません。まず TypeScript の enum emitter と既存の enum 出力テストを見つけ、次に出力された形式を minifier と tree-shaking の動作と比較してください。実行時の動作を変更せず、合意した出力戦略が回帰テストでカバーされれば完了です。