[jira] [Created] (GROOVY-9762) Wrong type resolved if method reference used with typed method

["Marcin Zajaczkowski (Jira)" <ji...@apache.org>]

Marcin Zajaczkowski created GROOVY-9762:
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             Summary: Wrong type resolved if method reference used with typed method
                 Key: GROOVY-9762
                 URL: https://issues.apache.org/jira/browse/GROOVY-9762
             Project: Groovy
          Issue Type: Bug
          Components: Compiler
    Affects Versions: 3.0.5
            Reporter: Marcin Zajaczkowski


I've encountered a problem with type checking if a method reference is used.

In following (stripped down from the original production case) code in the line with the error variable the following error is reported:
{code:java}
> Task :compileTestGroovy
startup failed:
/home/foobar.../MethodReferenceProblemWithType.groovy: 15: [Static type checking] - Cannot assign value of type java.lang.Object to variable of type java.util.List <Integer>
 @ line 15, column 31.
 List<Integer> error = opt.map(this::just).get()  {code}
{code:java}
@CompileStatic
class MethodReferenceProblemWithType {

    static void reproduce() {
        Optional<Integer> opt = Optional.ofNullable(Integer.valueOf(1))
        List<Integer> ok = opt.map(o -> just(o)).get()    //ok
        List<Integer> error = opt.map(this::just).get()   //problem
    }
    private static <T> List<T> just(T data) {
        return new ArrayList<T>();
    }
}  {code}

If `@CompileStatic` is removed, I still see a type incompatibility warning in Idea. Switching to lambda is an workaround. Tested with Groovy 3.0.5.



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