fix: proper typing on foreach return inside the pipe

src/filter/filter.ts

@@ -1,6 +1,5 @@
 import { Kind } from '../common';
 
-// export type FilterFn<T> = (value: T, index: number) => boolean;
 export type Filter<T> = {
   kind: Kind.FILTER;
   run: (value: T, index: number) => T;

src/forEach/forEach.ts

@@ -1,18 +1,17 @@
 import { Kind } from '../common';
 
-export type ForEachFn<T> = (value: T, index: number) => void;
 export type ForEach<T> = {
   kind: Kind.FOR_EACH;
-  run: ForEachFn<T>;
+  run: (value: T, index: number) => T;
 };
 
 /**
  * rxjs "tap" analogue
  * does not change array values
  */
-export function forEach<TValue>(fn: ForEachFn<TValue>): ForEach<TValue> {
+export function forEach<T>(fn: (value: T, index: number) => void): ForEach<T> {
   return {
     kind: Kind.FOR_EACH,
-    run: fn
+    run: fn as (value: T, index: number) => T,
   };
 }

src/fuzion.test.ts

@@ -82,6 +82,17 @@ describe('fuzion', () => {
     ).toEqual([false, false]);
   });
 
+  test('should do nothing in foreach, then filter and map values', () => {
+    expect(
+      fuzion(
+        [true, false, true],
+        forEach(() => {}),
+        filter(a => a === true),
+        map(a => !a),
+      ),
+    ).toEqual([false, false]);
+  });
+
   test('should apply 9 operators', () => {
     expect(
       fuzion(