Well, today I had a look, curious to see what would happen. Here's my Groovy script, with a variable called "thing", which is first defined as "Tom" and then later as "50":
First, once we've stepped past the first definition, the debugger shows us the correct value as well as the type:
Next, it does the same for the number:
Pretty cool. Untyped variables in Groovy are correctly reflected according to type in the NetBeans debugger.