Performance issue for big (1000+ lines) xsemantics files

[SimonCockx]

The type system of the Rosetta DSL has grown into a sizeable Xsemantics definition (1000+ lines). Unfortunately, I have noticed a serious degradation in the performance of Eclipse while this Xsemantics file is open in the editor. Splitting the Xsemantics file into three separate files of no more than 540 lines did improve the situation, but I'm still somewhat troubled by the waiting time, especially because I foresee another significant growth in file size in the future.

I'm not sure about the cause of this issue. I've worked with other Xtext-based DSL's of greater file size in the past without trouble.

See finos/rune-dsl#537 for more information.