Note that End is perfectly admitted as a class method (fortunately for libGDX) but the main problem is not exactly here because I agree and I will change the name of the Loop function. It is in the error message that is reported to the user. It should be something like "Loop is a reserved keyword". And if I put the word "Loop" alone, the parser should be able to make the difference and warns me with a message like "Do is missing", but certainly not with "End Sub is missing", which is wrong and doesn't give any clue to the developper. Same problem with "Next".