[jira] [Resolved] (GROOVY-7691) Type checking error on generic property with covariant type in subclass

["Daniel Sun (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/GROOVY-7691?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Sun resolved GROOVY-7691.
--------------------------------
    Resolution: Fixed
      Assignee: Daniel Sun

It is fixed by the proposed PR. Thanks!
https://github.com/apache/groovy/pull/198

> Type checking error on generic property with covariant type in subclass
> -----------------------------------------------------------------------
>
>                 Key: GROOVY-7691
>                 URL: https://issues.apache.org/jira/browse/GROOVY-7691
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static Type Checker
>    Affects Versions: 2.4.5
>            Reporter: Frank Pavageau
>            Assignee: Daniel Sun
>            Priority: Major
>              Labels: test
>
> A property declared with a generic type in a superclass is not seen with the correct covariant type in a subclass narrowing the type:
> {code}
> abstract class AbstractNumberWrapper<S extends Number> {
>     protected final S number;
>     AbstractNumberWrapper(S number) {
>         this.number = number
>     }
> }
> class LongWrapper<S extends Long> extends AbstractNumberWrapper<S> {
>     LongWrapper(S longNumber) {
>         super(longNumber)
>     }
>     S getValue() {
>         return number;
>     }
> }
> assert new LongWrapper<Long>(42L).value == 42L
> {code}
> raises the following error when type checked:
> {noformat}
> [Static type checking] - Cannot return value of type java.lang.Number on method returning type S
>  @ line 15, column 28.
>                        return number;
>                               ^
> 1 error{noformat}



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