override signatures

overrides.ts

export type Overrides<T extends (...args: any) => any> = T extends {
  (...args: infer A0): infer R0;
  (...args: infer A1): infer R1;
  (...args: infer A2): infer R2;
  (...args: infer A3): infer R3;
  (...args: infer A4): infer R4;
  (...args: infer A5): infer R5;
  (...args: infer A6): infer R6;
  (...args: infer A7): infer R7;
  (...args: infer A8): infer R8;
}
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
      (...args: A4) => R4,
      (...args: A5) => R5,
      (...args: A6) => R6,
      (...args: A7) => R7,
      (...args: A8) => R8,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
      (...args: infer A3): infer R3;
      (...args: infer A4): infer R4;
      (...args: infer A5): infer R5;
      (...args: infer A6): infer R6;
      (...args: infer A7): infer R7;
    }
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
      (...args: A4) => R4,
      (...args: A5) => R5,
      (...args: A6) => R6,
      (...args: A7) => R7,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
      (...args: infer A3): infer R3;
      (...args: infer A4): infer R4;
      (...args: infer A5): infer R5;
      (...args: infer A6): infer R6;
    }
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
      (...args: A4) => R4,
      (...args: A5) => R5,
      (...args: A6) => R6,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
      (...args: infer A3): infer R3;
      (...args: infer A4): infer R4;
      (...args: infer A5): infer R5;
    }
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
      (...args: A4) => R4,
      (...args: A5) => R5,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
      (...args: infer A3): infer R3;
      (...args: infer A4): infer R4;
    }
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
      (...args: A4) => R4,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
      (...args: infer A3): infer R3;
    }
  ? [
      (...args: A0) => R0,
      (...args: A1) => R1,
      (...args: A2) => R2,
      (...args: A3) => R3,
    ]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
      (...args: infer A2): infer R2;
    }
  ? [(...args: A0) => R0, (...args: A1) => R1, (...args: A2) => R2]
  : T extends {
      (...args: infer A0): infer R0;
      (...args: infer A1): infer R1;
    }
  ? [(...args: A0) => R0, (...args: A1) => R1]
  : [T];

type ZeroToEight = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8;
export type FromOverrides<T extends { length: ZeroToEight }> = [
  never,
  T extends [infer F] ? F : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
    infer F4 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
        (...args: Parameters<F4>): ReturnType<F4>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
    infer F4 extends (...args: any) => any,
    infer F5 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
        (...args: Parameters<F4>): ReturnType<F4>;
        (...args: Parameters<F5>): ReturnType<F5>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
    infer F4 extends (...args: any) => any,
    infer F5 extends (...args: any) => any,
    infer F6 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
        (...args: Parameters<F4>): ReturnType<F4>;
        (...args: Parameters<F5>): ReturnType<F5>;
        (...args: Parameters<F6>): ReturnType<F6>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
    infer F4 extends (...args: any) => any,
    infer F5 extends (...args: any) => any,
    infer F6 extends (...args: any) => any,
    infer F7 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
        (...args: Parameters<F4>): ReturnType<F4>;
        (...args: Parameters<F5>): ReturnType<F5>;
        (...args: Parameters<F6>): ReturnType<F6>;
        (...args: Parameters<F7>): ReturnType<F7>;
      }
    : never,
  T extends [
    infer F1 extends (...args: any) => any,
    infer F2 extends (...args: any) => any,
    infer F3 extends (...args: any) => any,
    infer F4 extends (...args: any) => any,
    infer F5 extends (...args: any) => any,
    infer F6 extends (...args: any) => any,
    infer F7 extends (...args: any) => any,
    infer F8 extends (...args: any) => any,
  ]
    ? {
        (...args: Parameters<F1>): ReturnType<F1>;
        (...args: Parameters<F2>): ReturnType<F2>;
        (...args: Parameters<F3>): ReturnType<F3>;
        (...args: Parameters<F4>): ReturnType<F4>;
        (...args: Parameters<F5>): ReturnType<F5>;
        (...args: Parameters<F6>): ReturnType<F6>;
        (...args: Parameters<F7>): ReturnType<F7>;
        (...args: Parameters<F8>): ReturnType<F8>;
      }
    : never,
][T['length']];