I have come across this issue using UE4.7.4(binary build) on a Win8.1 x64 using VS2013 Ultimate. When trying to add C++ code through the appropriate menu entry in the editor, and selecting the WidgetBlueprint as parent class an error message pops up saying:
"Failed to add class WhateverYourClassIsNamed. Failed to automatically hot reload the ‘YourProjectName’ module."
After pressing “OK” on the popup, a red warning appears on the class creation window saying:
"The name WhateverYourClassIsNamed is already used by another class."
The thing is, the corresponding .h and .cpp DO get created, however the hot reload fails. What’s more, whenever the newly created class needs to include a header (i.e. all classes except the ones created through the “None” category, right?) the compiler fails to locate the file, no matter how much I fiddle around with the include folders/paths. I’ve checked through the file explorer and the required headers do exist precisely in the folder pointed at by the include path. I’ve also tried to clear the Temp folder as per this. Regenerating the project files doesn’t help either.
I’d like to know whether there is any known solution for this and/or if this is a known bug. It would be a pity having to downgrade to 4.6 again, since I love the C++ improvements of 4.7