pack_unpack_generics.ts

pack_unpack_generics.ts

export type PackedGenerics<A,B,C> = {
  a: A,
  b: B,
  c: C
}

type testType = PackedGenerics<number, boolean, string>

type unpack2nd<T extends PackedGenerics<any, any, any>> = T extends PackedGenerics<infer A2, infer B2, infer C2> ? {
  a2: A2,
  b2: B2,
  c2: C2,
} : never;

type unpacked2nd = unpack2nd<testType>

type wrongType = unpack2nd<number>
const someWrongValue: wrongType = null as any

const a: unpacked2nd = {
  a2: 3,
  b2: false,
  c2: 'a',
}