Preserve comments with object destructuring assignment

リンクされた TypeScript Playground での動作を再現し、直接アクセスされるプロパティと object destructuring によって導入される変数のホバーツールチップを比較します。destructured bindings のコメントを解決する language-service/type-checking の経路を追跡します。x、y、および destructured function parameters に対して宣言されたプロパティのコメントが表示され、runtime output が変わらなければ完了です。

Search Terms

object destructuring assignment, comment

Suggestion

interface MyInterface {
    /**
     * I am x
     */
    x : number;
    /**
     * I am y
     */
    y : number;
}
declare const myInterface : MyInterface;
const {x, y} = myInterface;

/**
 * Expected tooltip to have comment,
 * > I am x
 * 
 * Actual: No comment
 */
x;
/**
 * Expected tooltip to have comment,
 * > I am y
 * 
 * Actual: No comment
 */
y;

/**
 * Expected tooltip to have comment,
 * > I am x
 * 
 * Actual:
 * Tooltip has comment,
 * > I am x
 */
myInterface.x;

/**
 * Expected tooltip to have comment,
 * > I am y
 * 
 * Actual:
 * Tooltip has comment,
 * > I am y
 */
myInterface.y;

/**
 * I am z
 */
const z = 1;

/**
 * Expected tooltip to have comment,
 * > I am z
 * 
 * Actual:
 * Tooltip has comment,
 * > I am z
 */
z;

Playground

Use Cases

I came across this idea after writing code like this,

function foo (
  {
    somePropertyA,
    somePropertyB,
    somePropertyC,
  } : SomeObject
) {
  /* Use these properties */
}

And I was hazy on the details of what each property was for.
So, I hovered my cursor over the variables somePropertyA, somePropertyB, somePropertyC and noticed there were no comments.

I had to go to the declaration of somePropertyA, somePropertyB, somePropertyC and look at each property individually.

---

At the moment, the way to get comments is to just do,

function foo (
  o : SomeObject
) {
  /* Use these properties */
}

Then the tooltip for o.somePropertyA, o.somePropertyB, o.somePropertyC will have comments

Examples

See above suggestion

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, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.