How can I define a type in typescript so that I can e.g. all the first parameter types of a function type:

Playground: https://tsplay.dev/m3Gqqm

I have types that enforce relationship between both members of a tuple within array of these tuples when passed as argument to function i.e. second member is a function that takes in a data parameter matching first member.

I have an interesting and, I think, a little crazy question. The answer to which I not only couldn’t find, but I couldn’t even figure out how to briefly formulate it for a search query. And so, the question is:

I came across some unexpected behavior when trying to expand mapped type I created from an union of object types, when trying to use this type within conditional type: Playground

I’ve been fiddling with some transformation of arguments of a function via a recursive type, have some issue to make the type work, I made same simplified example to highlight the issue, together with examples using mapped type (for this toy example mapped type would be enough): Playground

Consider the following code:

Consider the following code:

I have some Set, which defines some IDs:
export const IDS: Set<number> = new Set<number>([1, 30, 50, 9999]);

I have a type that generates Function type with parameters from tuple provided as an arbitrarily long tuple, this is further transformed so that every param may be undefined: