Following code causes UnsupportedOperationException.
combination of break and detach statement seems to cause the problem.
@startuml
while ( TRUE )
if (A) then (yes)
break
endif
if (B) then (yes)
:return error;
detach
endif
endwhile
:return 0;
@enduml
Environment:
PlantUML(1.2019.02)
Java 1.8.0_191-b12
OS: Windows10 64bit