GroovyLint is a library for Groovy that adds additional compile time checks. That makes sense as Groovy is a dynamically typed language and catches most of the errors at runtime, Java would catch at compile time. You know, the sooner a problem is caught, the less time you have to spend debugging it.
GroovyLint is an AST (abstract syntax tree) transformation that performs various checks on the abstract syntax tree of your program. To get GroovyLint working, all you have to do is add the GroovyLint jar file to your classpath. You need Groovy 1.7 or higher.
The currently implemented errors that by GroovyLint are described here. Through Groovys dynamic meta programming capabilities, some of GroovyLint errors could be valid Groovy code. But you can always turn of certain GroovyLint errors if they clash with your style of programming. See here for more informations.