Refactorings to convert from function declarations to function expressions

Suggestion

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refactoring quick fix vs code action

✅ 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

We already have refactorings to convert function expressions (arrow or non-arrow) to a function declaration, e.g. we can use "convert to named function" on both of these:

const fn1 = function () {
    return 1;
};

const fn2 = () => {
    return 1;
};

However, there is no refactoring to convert in the opposite direction—from a function declaration to a function expression.

I would like to suggest adding these refactorings so we cover all possibilities.

Note we do already have these refactorings (https://github.com/microsoft/TypeScript/pull/28250):

• "Convert to arrow function"
• "Convert to anonymous function"

However these only work on function expressions—they don't work on function declarations. Perhaps we could fix this by extending the scope of those refactorings so they do work on function declarations.

既存の "Convert to arrow function" および "Convert to anonymous function" リファクタリングを調べることから始め、現在 function expressions をどのように処理しているかに注目してください。関連するリファクタリングの対象範囲を function declarations に拡張し、実行時の動作を変更せずに declarations を要求された形式へ変換できることを確認してください。