Answering your question, maybe a popover with text "Your program is not parsed" would help? Also somehow I am used to "build" (instead of "parse") terminology,

Answering your question, maybe a popover with text "Your program is not parsed" would help? Also somehow I am used to "build" (instead of "parse") terminology, so my eyes just have not caught "parse" keyword. Though, I guess here nothing is built, only parsed. ;) All in all some information, about parsing before running would add extra points to the UX.