[jira] [Commented] (GROOVY-7985) Wrong "incompatible generic type" error

["Michael Wilkowski (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-7985?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15880309#comment-15880309 ] 

Michael Wilkowski commented on GROOVY-7985:
-------------------------------------------

Another example:

{code:title=GroovyFunctionTypeInferenceTest|borderStyle=solid}
import groovy.transform.CompileStatic
import org.apache.commons.lang3.tuple.Pair
import org.junit.Test
import java.util.function.Function

@CompileStatic
class GroovyFunctionTypeInferenceTest {
  @Test
  void functionWithoutPairTest() {
    // some function that operates on list and returns an element of this list
    Function<List<String>, String> function =
        { List<Pair<String, Integer>> it -> it[0] } as Function
    def list = new ArrayList<String>()
    function.apply(list)
  }

  @Test
  void functionWithPair1Test() {
    // some function that operates on list and returns an element of this list
    Function<List<Pair>, Pair> function =
        { List<Pair<String, Integer>> it -> it[0] } as Function
    def list = new ArrayList<Pair>()
    function.apply(list)
  }

  @Test
  void functionWithPair2Test() {
    // some function that operates on list and returns an element of this list
    Function<List<Pair<String, Integer>>, Pair<String, Integer>> function =
        { List<Pair<String, Integer>> it -> it[0] } as Function
    def list = new ArrayList<Pair<String,Integer>>()
    function.apply(list)
  }
}
{code}

functionWithoutPairTest() and functionWithPair1Test() compile, functionWithPair2Test() fails with the following error:
{code}
Error:(36, -1) Groovy-Eclipse: Groovy:[Static type checking] - Incompatible generic argument types. Cannot assign java.util.function.Function <java.util.List, org.apache.commons.lang3.tuple.Pair> to: java.util.function.Function <List, Pair>
Error:(38, -1) Groovy-Eclipse: Groovy:[Static type checking] - Cannot call java.util.function.Function <java.util.List, org.apache.commons.lang3.tuple.Pair>#apply(java.util.List <Pair>) with arguments [java.util.ArrayList <Pair>]
{code}

> Wrong "incompatible generic type" error
> ---------------------------------------
>
>                 Key: GROOVY-7985
>                 URL: https://issues.apache.org/jira/browse/GROOVY-7985
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static Type Checker
>    Affects Versions: 2.4.7
>            Reporter: Mauro Molinari
>
> Consider the following:
> {code}
> package test;
> import java.io.Serializable;
> public final class Pair<L, R> implements Serializable {
> 	public static <L, R> Pair<L, R> of(final L left, final R right) {
> 		return new Pair<>(left, right);
> 	}
> 	public final L left;
> 	public final R right;
> 	private Pair(final L left, final R right) {
> 		this.left = left;
> 		this.right = right;
> 	}
> }
> {code}
> And the following Groovy class:
> {code}
> package test2
> import test.Pair
> import java.util.Date;
> import groovy.transform.CompileStatic
> @CompileStatic
> class Test {
> 	Pair<Pair<Integer, Pair<String, Date>>, Pair<Integer, Pair<String, Date>>> doSmething() {
> 		def left = (Pair<Integer, Pair<String, Date>>) null
> 		def right = (Pair<Integer, Pair<String, Date>>) null
> 		return Pair.of(left, right)
> 	}
> }
> {code}
> Compilation fails with the following error message:
> {noformat}
> [Static type checking] - Incompatible generic argument types. Cannot assign test.Pair <test.Pair, test.Pair> to: test.Pair <Pair, Pair>
>  @ line 15, column 10.
>                 return Pair.of(left, right)
> {noformat}



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