Because turning the inference dial up often results with what Flow does: it shows the error at all the wrong places and doesn&#x27;t show it at the right one.<p>Try adding the types to the function in your Flow example. The error will finally move to the last line i.e. Flow will actually become useful in tracing down the error.<p><a href="http:&#x2F;&#x2F;tryflow.org&#x2F;#e6512d9c847d504bba8be8b90427ffc3" rel="nofollow">http:&#x2F;&#x2F;tryflow.org&#x2F;#e6512d9c847d504bba8be8b90427ffc3</a><p>I think Microsoft made the right call to demand function argument types. It doesn&#x27;t cost very much at all, but it improves error messages tremendously. It might not matter in a tiny example, but I&#x27;d bet that Flow&#x27;s behaviour can be frustrating in a large project.