groovy-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jamie Echlin <>
Subject Re: infer return type of script
Date Tue, 22 Sep 2015 09:36:53 GMT
No, I guess so. So it sounds like you're saying I should forget it and move
on to the next thing? I.e. it's not feasible to get at this in a static
analysis context?

On Tue, Sep 22, 2015 at 10:24 AM, C├ędric Champeau <
> wrote:

> Just for context and history, early versions of the type checker had
> return type inference for methods too. However, we removed it for a good
> reason: overrides. A method "foo" in class A can have an inferred type T,
> but "foo" from B extends A could very well have a different inferred type
> T2. So you can make no guarantee, at least for non private methods.
> 2015-09-22 11:19 GMT+02:00 Jamie Echlin <>:
>> Hi Shil,
>> I did that actually, but it tells me the return type of the run method of
>> Script is Object. Which is expected, if it's just looking at the actual
>> method signature.
>> But what I was hoping for is that given a script:
>> "new Double(2)"
>> it would be able to infer the actual return type is a Double. Now, I can
>> imagine scripts where you randomly pick from any class on the classpath,
>> invoke a no-args constructor, and return that... in that case I don't
>> expect magic. But most scripts have one or two possible return statements
>> (maybe implicit), I'm wondering if there is already code that can
>> statically analyse a method/script and say that there are only one, two or
>> whatever possible return types.
>> I'll take a look at ReturnAdder, thanks for that.
>> cheers, jamie
>> On Mon, Sep 21, 2015 at 11:55 PM, Shil Sinha <>
>> wrote:
>>> Actually, the second option can be made safe by initializing ReturnAdder
>>> with a listener, which will allow you to 'visit' all implicit returns
>>> without actually adding return statements.
>>> On Mon, Sep 21, 2015 at 5:30 PM, Shil Sinha <>
>>> wrote:
>>>> You could call 'getInferredReturnType' on the 'run' method node of your
>>>> script class, but inferred return types only appear to be stored for
>>>> closures and certain binary expressions (based on the usages of the
>>>> INFERRED_RETURN_TYPE marker and the storeInferredReturnType method).
>>>> You could also add all implicit return statements to the 'run' method
>>>> via ReturnAdder, and then infer a return type by visiting all of the return
>>>> statements, but I'm not sure if that kind of AST modification in a type
>>>> checking extension is safe.
>>>> Shil
>>>> On Mon, Sep 21, 2015 at 4:34 PM, Jamie Echlin <>
>>>> wrote:
>>>>> Hi...
>>>>> Is it possible to infer the return type, or types of a script during
>>>>> static compilation? Presumably there is always a finite list of branches
>>>>> where the script could end.
>>>>> I'm looking
>>>>> at,
>>>>> but I'm not really sure how to call it from a type checking script, nor
>>>>> what adds the inferred return type to the metadata which is used in that
>>>>> method.
>>>>> cheers, jamie

View raw message