fix(pipe): align static pipe to Observable pipe rest parameters overl… (#4112)

* fix(pipe): align static pipe to Observable pipe rest parameters overload (#4109)

* test(pipe): add dtslint test for rest parameters overload (#4109)

Author: dkosasih

spec-dtslint/util/pipe-spec.ts

@@ -44,6 +44,14 @@ it('should infer for 9 arguments', () => {
   const o = pipe(a('0', '1'), a('1', '2'), a('2', '3'), a('3', '4'), a('4', '5'), a('5', '6'), a('6', '7'), a('7', '8'), a('8', '9')); // $ExpectType UnaryFunction<"0", "9">
 });
 
+it('should infer {} for more than 9 arguments', () => {
+  const o =  pipe(a('0', '1'), a('1', '2'), a('2', '3'), a('3', '4'), a('4', '5'), a('5', '6'), a('6', '7'), a('7', '8'), a('8', '9'), a('9', '10'));  // $ExpectType UnaryFunction<"0", {}>
+});
+
+it('should require a type assertion for more than 9 arguments', () => {
+  const o: UnaryFunction<'0', '10'> = pipe(a('0', '1'), a('1', '2'), a('2', '3'), a('3', '4'), a('4', '5'), a('5', '6'), a('6', '7'), a('7', '8'), a('8', '9'), a('9', '10')); // $ExpectError
+});
+
 it('should enforce types for the 2nd argument', () => {
   const o = pipe(a('0', '1'), a('#', '2')); // $ExpectError
 });

src/internal/util/pipe.ts

@@ -15,9 +15,10 @@ export function pipe<T, A, B, C, D, E, F>(op1: UnaryFunction<T, A>, op2: UnaryFu
 export function pipe<T, A, B, C, D, E, F, G>(op1: UnaryFunction<T, A>, op2: UnaryFunction<A, B>, op3: UnaryFunction<B, C>, op4: UnaryFunction<C, D>, op5: UnaryFunction<D, E>, op6: UnaryFunction<E, F>, op7: UnaryFunction<F, G>): UnaryFunction<T, G>;
 export function pipe<T, A, B, C, D, E, F, G, H>(op1: UnaryFunction<T, A>, op2: UnaryFunction<A, B>, op3: UnaryFunction<B, C>, op4: UnaryFunction<C, D>, op5: UnaryFunction<D, E>, op6: UnaryFunction<E, F>, op7: UnaryFunction<F, G>, op8: UnaryFunction<G, H>): UnaryFunction<T, H>;
 export function pipe<T, A, B, C, D, E, F, G, H, I>(op1: UnaryFunction<T, A>, op2: UnaryFunction<A, B>, op3: UnaryFunction<B, C>, op4: UnaryFunction<C, D>, op5: UnaryFunction<D, E>, op6: UnaryFunction<E, F>, op7: UnaryFunction<F, G>, op8: UnaryFunction<G, H>, op9: UnaryFunction<H, I>): UnaryFunction<T, I>;
+export function pipe<T, A, B, C, D, E, F, G, H, I>(op1: UnaryFunction<T, A>, op2: UnaryFunction<A, B>, op3: UnaryFunction<B, C>, op4: UnaryFunction<C, D>, op5: UnaryFunction<D, E>, op6: UnaryFunction<E, F>, op7: UnaryFunction<F, G>, op8: UnaryFunction<G, H>, op9: UnaryFunction<H, I>, ...operations: UnaryFunction<any, any>[]): UnaryFunction<T, {}>;
 /* tslint:enable:max-line-length */
 
-export function pipe<T, R>(...fns: Array<UnaryFunction<T, R>>): UnaryFunction<T, R> {
+export function pipe(...fns: Array<UnaryFunction<any, any>>): UnaryFunction<any, any> {
   return pipeFromArray(fns);
 }