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

["Paul King (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-9762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17217243#comment-17217243 ] 

Paul King edited comment on GROOVY-9762 at 10/20/20, 3:59 AM:
--------------------------------------------------------------

The build is currently failing, just for GROOVY_3_0_X not master, on the final variant added in the test case:
{code}
def <T> List<T> list(T item) {
    return [item]
}
@groovy.transform.CompileStatic
def test() {
    Optional<Integer> opt = Optional.ofNullable(1)
    List<Integer> ret = opt.map(this::list).get()
    println ret
    return ret
}
assert test() == [1]
{code}
So, I have temporarily comment it out.


was (Author: paulk):
The build is currently failing on the final variant added in the test case:
{code}
def <T> List<T> list(T item) {
    return [item]
}
@groovy.transform.CompileStatic
def test() {
    Optional<Integer> opt = Optional.ofNullable(1)
    List<Integer> ret = opt.map(this::list).get()
    println ret
    return ret
}
assert test() == [1]
{code}
So, I have temporarily comment it out.

> 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
>            Assignee: Eric Milles
>            Priority: Minor
>             Fix For: 3.0.7, 4.0.0-alpha-2
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> 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 a workaround, therefore it's just a minor glitch. Tested with Groovy 3.0.5.



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