This is one of those things which is probably impossible to reproduce outside of a large project:
The above screenshot is from within one of my classes… but the graph that’s been opened after the compile error is from a macro library! But there is nothing wrong wher the error is indicated…
However, what IS wrong is here in said macro library. A variable type for an interface function has changed and this macro’s output plugs into that… leading to the Blueprint editor not understanding where the error is.
These types of “the error is not where you think it is” is quite common in C and C++ but relatively rare in Blueprints…