Name "is used by another variable or function" after renaming BP interface

This is a bugreport, I hope it is correct to post it here:

Renaming input variables in blueprint interfaces does not work correctly in UE 4.12.5. After renaming, I cannot use the original name any more.

Steps to reproduce:

  • create an empty blueprint project
  • create a new blueprint interface
  • set the name of the interface function
  • add one input parameter “Owner” of type Actor reference
  • create a new blueprint based on Actor class
  • add the blueprint interface that was just created (in class settings)
  • compile
  • insert an event for the blueprint interface function to event graph, this event has a parameter called “Owner”
  • rename “Owner” in the blueprint interface to “Parent”
  • try to create a variable named “Owner” in the blueprint which implements the interface

The name “Owner” cannot be used any more. I tried to recompile everything, build, restart UE, but still I cannot use the name “Owner”. I keep getting the message that “Owner is used by another variable or function”.

This seems to be a bug. Is there a known workaround?

I just got a hint: The name “Owner” is reserved, as there is already a variable named Owner. So this issue is not related to BP interfaces. Maybe the error message should state “The variable name Owner is reserved” instead…