3 replies

Typescript Generics

I want to create a class who's signature is modified by function calls.

For example;

const thing = new Thing(); // Thing<"">

const thing = new Thing(); // Thing<"">

const thing = new Thing(); // Thing<"foo" | "bar">
thing.add("foo"); // Thing<"foo" | "bar">
thing.add("bar"); // Thing<"foo" | "bar">

const thing = new Thing(); // Thing<"foo" | "bar">
thing.add("foo"); // Thing<"foo" | "bar">
thing.add("bar"); // Thing<"foo" | "bar">

I know that I can add to the generic by chaining

.add().add()

.add().add()

and having

add

add

's signature be

add<T>(arg: T): Thing<ThingGeneric | T>

add<T>(arg: T): Thing<ThingGeneric | T>

, but I would like to be able to perform some kind of operation where if

add

add

is called with some parameter

, then

thing

thing

always has been of a type such that it's first generic includes

.

Is this even remotely possible?