Indeed, as said Steve, you are using 4.11 and from the log and the 4.11 source the overlap singature is
(AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult);
so you need to have :
UFUNCTION()
void OnOverlapBegin(AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult);
void AMyActor::OnOverlapBegin(AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult)