Better argument description for inferred argument types #26563

Search Terms

tsserver, server, infer, argument help

Suggestion

Get a better argument description when accessing the argument help of an inferred argument list.

When accessing the argument information for the following code (Playground), both vscode and the playground only show fun2(...args: [number, string]): string:

type Parameters<T> = T extends (...args: infer U) => any ? U : never;
declare function fun1(x: number, y: string): number;
declare function fun2(...args: Parameters<typeof fun1>): string;

fun2(/* get parameter help here */);

fun2(10, "text");
/* ^ hover here */

It'd be a lot more intuitive, if the help would resemble the actual parameters.

When hovering over fun2 in the playground, it even shows the more readable information fun2(x: number, y: string): number, so this might be an easy improvement.

Use Cases

Even though the current display is perfectly valid, it makes it hard to understand what the parameters were meant for, so the only use case for this would be readability/UX.

Related Issues

Not exactly a duplicate of #26132 (which seems fixed in 3.1.0-dev.20180818), but also not a totally different one. If you consider this feature request a duplicate, feel free to close it.

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)