Parse/Generate call signature with keeping argument name

[whatasoda]

I want to do like this.

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)

[AlCalzone]

This would be very helpful when combined with #26190 as we could fix the problem that the inferred parameter names are off by one there.

[ahejlsberg]

Seems to me this can be accomplished using ReturnType<T> (added to lib.d.ts in 3.0) and the Parameters<T> type I suggest here #24897 (comment). The only one thing we don't support is extracting the parameter names, but that doesn't appear to be significant in the example.

[jednano]

@ahejlsberg the Parameters<T> type doesn't preserve the original argument names or TSDoc comments. I think what @whatasoda wants is very similar to the new feature request I just created #30351.

[typescript-bot]

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