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From Paul King <pa...@asert.com.au>
Subject Re: Possible New Groovy Features... - Deduce the type of final fields from their assigned value
Date Fri, 25 Aug 2017 02:28:01 GMT
I've only seen it used in the context of testing, e.g. where a Map of
Closures might be returned instead of the real object. But I don't know
what other uses people may have used it for in situations like DSLs.

Cheers, Paul.

On Fri, Aug 25, 2017 at 11:00 AM, MG <mgbiz@arscreat.com> wrote:

> Ehm - but that is something that _should_ fail in my book, since it
> violates the contract of what a ctor does (namely create an object of his
> type).
> I am not saying Groovy should go out of its way to _prevent_ code like
> this - but if I had to choose between _this_ working and the imho helpful
> (and to me obvious) feature that final defined objects automatically carry
> their actual type instead of all being Object|s... well... you get my
> drift...
> Or do you see any application of doing something like this in a real word
> scenario, e.g. in the context of a DSL ?
> Markus
>
>
> On 24.08.2017 14:07, Paul King wrote:
>
> It might be something that could work with @CompileStatic. For dynamic
> Groovy, I am not sure this can be done. Consider the following example
> which, although is dubious style, is valid Groovy:
>
> Date.metaClass.constructor = { 42 }
> final result = new Date()
> assert result instanceof Integer
> assert result == 42
>
> Cheers, Paul.
>
> On Wed, Aug 23, 2017 at 8:45 AM, MG <mgbiz@arscreat.com> wrote:
>
>> Hi Paul,
>>
>> On 21.08.2017 04:30, Paul King wrote:
>>
>> Deduce the type of final fields from their assigned value:
>>
>>> class Foo {
>>> final device = new PrinterDevice(...) // device field will have type
>>> PrinterDevice instead of Object when reflection is used on class Foo
>>> }
>>> Rationale: While IntelliJ does a good job at deducing the type of final
>>> fields, it would still be better if the Groovy language itself would use
>>> the more specialized type here, for e.g. reflection purposes
>>>
>> With @Typechecked or @CompileStatic type inferencing is going to be in
>> play. During debugging the runtime type is going to be available. What
>> "reflective purposes" did you have in mind?
>>
>>
>> In my framework I iterate over the fields of classes, which are of type
>> Object, if the have been defined in a compact way using just final, without
>> an explicit type - it would be helpful to have the type here.
>> And in general it just feels like a lost opportunity that final
>> fields/variables do not auto get the type of their assigned value - having
>> more information available is never bad.
>> Of course I am talking about this naively from a user's perspective: Do
>> you think adding this would a) be hard / time intensive (naively I would
>> have thought no), b) break backwards comptability (since the final
>> variable/field cannot be reassigned... (?))...
>>
>> Cheers,
>> Markus
>>
>>
>>
>>
>
>

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