MG, A note on "val" looking similar to "var": any good IDE labels final and non-final variables differently, e.g. IJ uses an underline. Even vim does this afaik. The keywords look similar in isolation, sure, but everywhere besides the declaration, you're not looking at the keyword for that info. And with the underline on the variable, the declarations don't look similar at all from experience. I've never been confused in Kotlin, even coming from Java where var was the only similar keyword.
Plus, from my experience, any declaration that takes multiple words to communicate it (even something as small as "let mut") just feels clunky compared to "val" and "var". It doesn't feel good to use, as it takes up more space in your brain trying to read it. You're also intuitively dissuaded from using the more complicated one because it takes an extra word, so if "final" is the extra word and it's not necessary to basic operation, very few people will use it. (See: Java, C, C++, literally every single language where "final" is the "second word".) On the topic of val meaning value-based semantics: that's never been a thing in any JVM languages, and val isn't used as a keyword in the major languages where it does exist. (Namely C, C++, and Rust.) Cheers, Caleb On Sun, Apr 12, 2026, 6:35 PM MG <[email protected]> wrote: > Hi Paul, > > I still have the following gripes with using "val" (and two other > languages having imho made a bad choice here still does not change that :-) > ): > > 1. "val" for me indicates value- (as opposed to reference) based > semantics, i.e. copy semantics / deep immutabilty, which the proposal > explictly states is not the goal here (see Non-goals @Immutable in the > GEP). > 2. "val" looks a lot like "var". > 1. So if looking over code it is harder to spot an error in this > regard > 2. And it might be confusing for ppl new to Groovy (unless they > come from Kotlin or Scala, which I find unlikely to happen). > 3. "val" is a variable name ppl use (Contrary to final, def and var). > 1. While this would still work , e.g. "val val" just looks akward. > 2. As well as making code using "val" as a variable name generally > worse to read. > 4. I see no need for "val", when it seems the same effect could be > reached by changing the semantics of existing "final" to use RHS type > deduction*. > 1. It seems to me this would not be a breaking change... (?) > 5. So while having type deduction would help our framework quite a > bit, I would argue for: > 1. "final" to finally be type deducing* G-) > 2. Or at least for a different keyword to be used. > 1. It is late and I need to go to sleep, but from the top of my > head: "fvar" or "fin" > 1. ("fin" would hit two birds with one stone: shorten the > quite long "final" and supply type deduction). > > Cheers, > mg > > *straightforward & stable, i.e. 99% what the user expects - make the > frequent case easy/fast, make the rare case correct (i.e. require the > developer to supply an explicit type). > > > > Am 12.04.2026 um 13:59 schrieb Paul King: > > Hi folks, > > We have been asked numerous times about the possibility of having a "val" > keyword to match Kotlin and Scala. We also have had a related Jira open for > more than 6 years. So I created a GEP to help frame a discussion about what > would be involved and help us make a decision: > > https://groovy.apache.org/wiki/GEP-16.html > > I know we have "final", but many developers I speak to from the Kotlin and > Scala worlds are big fans of "val" and believe it was the right name to use > for those two languages. > > Given that it involves changes to only about 15 lines of production Groovy > code and has well-identified impacts (arguably edge cases with > workarounds), I am largely in favor of this proposal, but I am keen to hear > other's thoughts. > > Cheers, Paul. > > > >
