A strange issue occurred today. I compiled the CIL on a system today, and the system reported an error. The error log included a handful of classes that did not exist in the system. They related to old classes that had been deleted.
A full X++ compile did not resolve the issue, the CIL still failed. I was able to resolve the issue by clearing the CIL directory:
C:\Program Files\Microsoft Dynamics AX\60\Server\<AX Instance>\bin\XppIL
Deleting all the files under this directory, then all the files under the “source” directory. Once done you need to recompile the X++ code, then complete the CIL compile, and presto errors are gone.