add types for just-curry-it (#446)

packages/function-curry/index.d.ts

@@ -1,7 +1,18 @@
 export default curry;
 
-// TODO: get more specific with permssible param types for returned function
-declare function curry(
-  fn: Function,
-  arity?: number,
-) : Function;
+type MakeTuple<LEN extends number, T extends any = any, C extends T[] = []> = C['length'] extends LEN ? C : MakeTuple<LEN, T, [T, ...C]>
+type CurryOverload<F extends (...args: any[]) => any, N extends unknown[], P extends unknown[]> =
+  N extends [infer L, ...infer R]
+  ? ((...args: [...P, L]) => CurryInternal<F, R>) & CurryOverload<F, R, [...P, L]>
+  : () => CurryInternal<F, P>
+type CurryInternal<F extends (...args: any[]) => any, N extends unknown[]> =
+  0 extends N['length'] ? ReturnType<F> : CurryOverload<F, N, []>
+type Curry<F extends (...args: any[]) => any, LEN extends number | undefined = undefined, I extends any = any> =
+  0 extends (LEN extends undefined ? Parameters<F>['length'] : LEN)
+  ? () => ReturnType<F>
+  : CurryInternal<F, LEN extends undefined ? Parameters<F> : MakeTuple<LEN extends undefined ? 0 : LEN, I>>
+
+declare function curry<F extends (...args: any[]) => any, L extends number>(
+  fn: F,
+  arity?: L | undefined,
+) : Curry<F, number extends L ? undefined : L, Parameters<F>[number]>;

packages/function-curry/index.tests.ts

@@ -12,10 +12,50 @@ curry(add)(1)(2)(3);
 
 curry(add, 1);
 curry(add, 1)(1);
+
+function many(a: string, b: number, c: boolean, d: bigint, e: number[], f: string | undefined, g: Record<any, any>): boolean {
+  return true
+}
+const return1 = curry(many)('')(123)(false)(BigInt(2))([1])(undefined)({})
+const return2 = curry(many)('', 123)(false, BigInt(2))([1], '123')({})
+const return3 = curry(many)('', 123, false)(BigInt(2), [1], undefined)({})
+const return4 = curry(many)('', 123, false, BigInt(2))([1], undefined, {})
+const return5 = curry(many)('', 123, false, BigInt(2), [1])(undefined, {})
+const return6 = curry(many)('', 123, false, BigInt(2), [1], undefined)({})
+const return7 = curry(many)('', 123, false)(BigInt(2), [1])(undefined)({})
+const returns: boolean[] = [return1, return2, return3, return4, return5, return6, return7]
+
+function dynamic(...args: string[]): number {
+  return args.length
+}
+const dy1 = curry(dynamic, 1)('')
+const dy2 = curry(dynamic, 2)('')('')
+const dy3 = curry(dynamic, 3)('')('')('')
+const dys: number[] = [dy1, dy2, dy3]
+
+// not OK
+// @ts-expect-error
 curry(add, 1)(1)(2);
+// @ts-expect-error
 curry(add, 1)(1)(2)(3);
+// @ts-expect-error
+curry(add, 4)('');
+
+// @ts-expect-error
+curry(many)(123)
+// @ts-expect-error
+curry(many)('', 123)(123)
+// @ts-expect-error
+curry(many)('', 123, true)('')
+// @ts-expect-error
+curry(many)('', 123, true, BigInt(2))('')
+// @ts-expect-error
+curry(many)('', 123, true, BigInt(2), [1])(123)
+// @ts-expect-error
+curry(many)('', 123, true, BigInt(2), [1,1], '')('')
+// @ts-expect-error
+curry(dynamic)(123)
 
-// not OK
 // @ts-expect-error
 curry();
 // @ts-expect-error