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From Basurita <basuraparabar...@gmail.com>
Subject Re: Unexpected behaviour for getAt operator operloading with static compilation
Date Sat, 21 Oct 2017 16:43:15 GMT
I'm not 100% certain, but my understanding is the following:
When you @CompileStatic the expression `int i= pippo['a']` the compiler will generate bytecode
for a method with signature `getAt(String)` that
returns an `Object`
    See  http://docs.groovy-lang.org/latest/html/groovy-jdk/java/lang/Object.html#getAt(java.lang.String)

The return type is not part of the method's signature, but Object is the expected value according
to the specification.
Then, you can't assign an Object to an int without casting. This is the same as in Java, which
is what happens when you @CompileStatic.
This has nothing to do with Pippo. You can change Pippo's `getAt` so it returns Object, and
you'll get the same error which is correct.
If you KNOW that it's going to be an int at run time, then use a cast, or else define variable
`i` as Object (or def).
Or don't use @CompileStatic in Demo (you can leave it for Pippo), and everythin will be resolved
dynamically at run time


BBB

On 10/21/17 1:06 PM, Mirco wrote:
> Hi,
> I've encountered a strange compile error with the getAt method and the @CompileStatic
annotation.
> Below some scripts to reproduce the error with the GroovyConsole:
>
> import groovy.transform.CompileStatic
> @CompileStatic
> class Pippo {
>     int getAt(String pluto) { return 1 }
>     int plus(String paperino) { return 1 }
> }
> @CompileStatic
> public class Demo {
>     public static void main(String[] args) {
>         def pippo = new Pippo()
>         int i = pippo['a']          // [Static type checking] - Cannot assign
value of type java.lang.Object to variable of type int
>         //int i = pippo.getAt('a')  // Works
>         //int i = pippo + 'a'       // Works
>     }
> }
> Demo.main()
>
> At first I thought of some general issue with operator overloading but the plus method
does not seem to be affected (last commented line above).
> Morevover, my actual code involves generics and in this case new errors came up even
with the cast:
>
> import groovy.transform.CompileStatic
> @CompileStatic
> class Pippo<K,V> {
>     V paperino
>     V getAt(K pluto) { return paperino }
> }
> @CompileStatic
> public class Demo {
>     public static void main(String[] args) {
>         Pippo<String, Integer> pippo = new Pippo<>()
>         pippo.paperino = 313
>         int i = (int) pippo['a']       // groovy.lang.MissingPropertyException:
No such property: a for class: Pippo
>         // int i = pippo.getAt('a')    // works
>         println i
>     }
> }
> Demo.main()
>
> If the two generic types are the same (ex. both Integer):
>
> BUG! exception in phase 'class generation' in source unit 'ConsoleScript0' At line 12
column 23
> On receiver: pippo with message: getAt and arguments: 1
> This method should not have been called. Please try to create a simple example reproducing
this error and filea bug report at
> https://issues.apache.org/jira/browse/GROOVY <https://issues.apache.org/jira/browse/GROOVY>
>
> import groovy.transform.CompileStatic
> @CompileStatic
> class Pippo<K,V> {
>     V paperino
>     V getAt(K pluto) { return paperino }
> }
> @CompileStatic
> public class Demo {
>     public static void main(String[] args) {
>         Pippo<Integer, Integer> pippo = new Pippo<>()
>         pippo.paperino = 313
>         int i = (int) pippo[1]       // groovy.lang.MissingPropertyException:
No such property: a for class: Pippo
>         // int i = pippo.getAt('a')    // works
>         println i
>     }
> }
> Demo.main()
>
> Is there some known issue about getAt and CompileStatic or simply I misunderstood its
use?
>
> Thanks,
>
> M




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