Both your examples use very simple logic. The Apache Groovy codebase example is of some peripheral functionality, i.e. a builder. All the methods in your Grails codebase example are, at most, 1 line long. I can't be bothered re-investigating what proportion of the core Groovy codebase really uses static compilation -- it certainly wasn't much only 2 years ago. As for Grails, virtually no-one has upgraded from v.2 to Grails 3 since it was released 2.5 yrs ago, or started many new projects with it.
i was just saying i personally found type declarations useful as the couple of small groovy codebases i worked on progressed over the short period (maybe a year?) i worked on them. thinking about how i might declare types made me decompose things a bit differently, which made the logic simpler in some places, which allowed me to do things like get rid of tests where i checked the behavior in a case where a method was missing on a function parameter, because now i knew the parameter was over certain type (and thus would have that method).
