Typescript remove first argument from a function

I think you can do that in a more generic way:

type OmitFirstArg<F> = F extends (x: any, ...args: infer P) => infer R ? (...args: P) => R : never;

and then:

type PostTransformationFn<F extends InitialFn> = OmitFirstArg<F>;

PG

You can use a conditional type to extract the rest of the parameters:

type State = { something: any }

type InitialFn = (state: State, ...args: string[]) => void

// this doesn't work, as F is unused, and args doesn't correspond to the previous arguments
type PostTransformationFn<F extends InitialFn> = F extends (state: State, ...args: infer P) => void ? (...args: P) => void : never

type X = PostTransformationFn<(state: State, someArg: string) => void> // (someArg: string) => void

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