Display signature help or completions for tuples with labels

Suggestion

🔍 Search Terms

List of keywords you searched for before creating this issue. Write them down here so that others can find this suggestion more easily and help provide feedback.

✅ Viability Checklist

My suggestion meets these guidelines:

• [x This wouldn't be a breaking change in existing TypeScript/JavaScript code
• [x This wouldn't change the runtime behavior of existing JavaScript code
• [x This could be implemented without emitting different JS based on the types of the expressions
• [x This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• [x This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

📃 Motivating Example

declare const coords: [x: number, y: number]

const [/**/] = coords

The problem: having no idea what a name to type as you don't know what the type of it.

I'm using it with my plugin and it looks very simple (and useful IMO):

Of course, you can hover of the variable to fiture it out, but what about the following example:

const a: {
    coords: [x: number, y: number] | string | { x: number; y: number }/* | even more types */
} = {
    coords: [/**/], // the type with x, y tuples can be even truncated, so you can only guess names of labels
}

I understand that labeled tuples introduced in ts4.0 were designed primarily for parameters usage, but I've seen them used for shorter static data declarations as well.

However, if you think that usage signature help is redundant and incorrect, what about having completions for tuple labels at least? There is already completions when acessing such symbols via dot property access. For example for first example it would be keyword completion with label x and [0]: number detail.

💻 Use Cases

Comienza revisando los ejemplos de labeled tuples y los dos comportamientos propuestos: signature help durante la desestructuración de tuplas y completions para tuple labels. Define qué comportamiento debería admitirse y cómo debería funcionar para unions o truncated tuple types; después, identifica los entry points y las pruebas relevantes de TypeScript language-service. Se considera terminado cuando la interacción elegida proporciona información útil sobre las labels sin cambiar la salida en runtime.