Intelisense gives false error on function definition with an extern defined

Using ESP32 with arduino core I have a function defined in my primary INO file which I extern in a global variables header I use across my project, however intelisense is giving an error of cannot overload functions distinguished by return type alone, however this function has a unique name, I believe it is giving this error because of the extern declaration, the code itself compiles and works fine.

Please give a complete code example for reproducing.