Okay quite a bit was wrong with that, but now it's right

src/compiler.c

@@ -2322,6 +2322,7 @@ static void generatorInner(KrkScanner scannerBefore, Parser parserBefore) {
 
 	emitLoop(loopStart);
 	patchJump(exitJump);
+	emitByte(OP_POP);
 }
 
 /**

src/obj_gen.c

@@ -90,6 +90,11 @@ KRK_METHOD(generator,__call__,{
 	size_t stackAfter = krk_currentThread.stackTop - krk_currentThread.stack;
 	self->running = 0;
 
+	if (IS_KWARGS(result) && AS_INTEGER(result) == 0) {
+		_set_generator_done(self);
+		return OBJECT_VAL(self);
+	}
+
 	/* Was there an exception? */
 	if (krk_currentThread.flags & KRK_THREAD_HAS_EXCEPTION) {
 		_set_generator_done(self);
@@ -102,8 +107,9 @@ KRK_METHOD(generator,__call__,{
 		self->args = realloc(self->args, sizeof(KrkValue) * (self->argCount + newArgs));
 		self->argCount += newArgs;
 	} else if (stackAfter < stackBefore) {
-		_set_generator_done(self);
-		return OBJECT_VAL(self);
+		size_t deadArgs = stackBefore - stackAfter;
+		self->args = realloc(self->args, sizeof(KrkValue) * (self->argCount - deadArgs));
+		self->argCount -= deadArgs;
 	}
 
 	/* Save stack entries */

src/vm.c

@@ -1870,6 +1870,9 @@ _resumeHook: (void)0;
 				}
 				krk_currentThread.stackTop = &krk_currentThread.stack[frame->outSlots];
 				if (krk_currentThread.frameCount == (size_t)krk_currentThread.exitOnFrame) {
+					if (frame->closure->function->isGenerator) {
+						return KWARGS_VAL(0);
+					}
 					return result;
 				}
 				krk_push(result);

test/testComplicatedGeneratorFunction.krk

@@ -0,0 +1,16 @@
+def agenerator(a=42):
+    print("First yield")
+    yield 1
+    if True:
+        yield 2
+    yield 3
+    print("Into the loops")
+    for i in range(a):
+        yield i
+        print("nest loop", i, a)
+        for j in range(a):
+            print("yielding",j)
+            yield j
+        print("Done with inner nest from",i)
+
+print(list(agenerator()))