The `@ClosureParams` annotation [added in Groovy 2.3](http://groovy-lang.org/releasenotes/groovy-2.3.html#Groovy2.3releasenotes-Closureparametertypeinference) gives type inferencing hints. Code of interest: `TIVWR.inferClosureParamTypes` `GroovyUtils.updateClosureWithInferredTypes`