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
