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https://issues.apache.org/jira/browse/SOLR-13658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16897135#comment-16897135
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Erick Erickson commented on SOLR-13658:
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I should think we can come reasonably close with something like
^\s*var\s
over in ./lucene/tools/src/groovy/check-source-patterns.groovy
Although I'm more interested in deciding if we're going to allow "var" _ever_.
If the answer is "no", then we should start establishing that norm now, and
perhaps put a regex test in. If we are going to allow that construct (and so
far of my main objection that it'd be easy to introduce runtime errors appears
to be unfounded) then I don't think it needs action....
> Discuss adding the new "var" construct to the forbidden API list.
> -----------------------------------------------------------------
>
> Key: SOLR-13658
> URL: https://issues.apache.org/jira/browse/SOLR-13658
> Project: Solr
> Issue Type: Wish
> Security Level: Public(Default Security Level. Issues are Public)
> Affects Versions: master (9.0)
> Reporter: Erick Erickson
> Assignee: Erick Erickson
> Priority: Major
>
> Personally, I'm strongly against allowing the "var" construct in Lucene/Solr
> code. I think it's a wonderful opportunity to introduce bugs that won't be
> found until runtime as well as making maintainence significantly harder. I
> don't even think for a project like Solr it would save any time overall...
> So let's discuss this ahead of time and see if we can reach a consensus. I'll
> start the discussion off:
> My baseline argument is that for a large complex project, especially ones
> with many different people coding, I want the compiler to give me all the
> help possible. And the "var" construct takes away some of that help.
> I’ve seen this argument go around at least 4 times in my career. The argument
> that “it takes longer to write if you have to type all this stuff” is bogus.
> Last I knew, 80% of the time spent is in maintaining/reading it. So the
> argument “I can write faster” means I can save some fraction of the 20% of
> the time writing the original code but spend many times that figuring out
> what the code is actually doing the other 80% of the time.
> The IDE makes _writing_ this slightly faster, admittedly.
> {code:java}
> Whatever what = new Whatever();
> var kidding = what.getComplex();
> var blivet = kidding.get("stuff");
> {code}
> But once that’s done, if I’m reading the code again I don't have any clue what
> {code:java}
> kidding or blivet
> {code}
> are. Here's the signature for getComplex:
> {code:java}
> Map<String, Map<Integer, Integer>> getComplex()
> {code}
> I have to go over to the definition (which I admit is easier than it used to
> be in the bad old days, but still) to find out.
> HERE'S THE PART I REALLY OBJECT TO!
> The above I could probably live with, maybe we could get the InteliJ
> developers and see if they can make hover show the inference. What I will
> kick and scream about is introducing bugs that are not found until runtime.
> Even this obvious stupidity fails with a ClassCastException:
> {code:java}
> var corny = new TreeMap<String, String>();
> corny.put("one", "two");
> corny.get(1);
> {code}
> But it's much worse when using classes from somewhere else. For instance,
> change the underlying class in the first example to return
> {code:java}
> Map<String, Map<String, Integer>>{code}
> .
> This code that used to work now throws an error, _but it compiles_.
> {code:java}
> var kidding = what.getComplex();
> var blivet = kidding.get("stuff");
> var blah = kidding.get("stuff").get(1); // generates ClassCastException:
> class java.lang.String cannot be cast to class java.lang.Integer
> {code}
> So in order to save some time writing (that I claim will be lost multiple
> times over when maintaining the code) we'll introduce run-time errors that
> will take a bunch _more_ time to figure out, and won’t be found during unit
> tests unless and until we have complete code coverage.
> If there's a way to insure that this kind of thing can't get into the code
> and we implement that, I could be persuaded, but let's make that an explicit
> requirement (and find a suitable task for the build system, precommit or
> whatever).
> The floor is open...
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