AX2012 : CIL generation error : The given key was not present in the dictionary.

Recently I faced this error when generating incremental IL
"CIL generation: The given key was not present in the dictionary."

The quick way to fix this is to check the CIL log file, generally located at "C:\Program Files\Microsoft Dynamics AX\60\Server\MicrosoftDynamicsAX\bin\XppIL\Dynamics.Ax.Application.dll.log"

Here you will find the AOT object for which the CIL generator found the error. Compile that object, fix the error and then regenerate the IL.

Before generating IL it is good practise to make sure that there are no compilation errors in the code.