The use of `Language.findInstance()` implicitly depended on the fact that
`SimpleLanguage.INSTANCE` was referenced at some earlier point in time. In this
case, that happens because the instantiation of `SimpleParserDefinition`
triggers the instantiation of `COMMENTS`, which relies on
`SimpleTypes.COMMENT`.
When basing one's work on this sample project, however, one may run into
issues. Specifically, the absence of a custom comment token type will mean a
failure to correctly instantiate the singleton language object. Making the
dependence on `SimpleLanguage.INSTANCE` explicit prevents that issue from
occurring.
If it is static then there are multi-threading issues. When indexing multiple threads are running and overwriting the lexer state that the word scanner uses.
I copied the SimplePlugin find usages class and spent hours chasing index out range bugs. I also noticed that the SimplePlugin which I have installed in my plugin dev environment would once in a while cause an exception but I did not pay it much attention. The static word scanner is the source.
