If you read the paper, From Modula to Oberon by Wirth, I already linked in a pervious comment when answering the question about subranges, you can also find the

If you read the paper, From Modula to Oberon by Wirth, I already linked in a pervious comment when answering the question about subranges, you can also find the reasoning behind the removal of enumerations. "Enumeration types appear to be a simple enough feature to be uncontroversial. However, they defy extensibility over module boundaries. Either a facility to extend given enumeration types has to be introduced, or they have to be dropped. A reason in favour of the latter, radical solution was the observation that in a growing number of programs the indiscriminate use of enumerations(and subranges) had led to a type explosion that contributed not to program clarity but rather to verbosity. In connection with import and export, enumerations give rise to the exceptional rule that the import of a type identifier also causes the (automatic) import of all associated constant identifiers. This exceptional rule defies conceptual simplicity and causes unpleasant problems for the implementor." http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.578.3109&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.578...