[jira] [Resolved] (GROOVY-9891) Wrongly detected incompatible generic arguments for Java collections

["Eric Milles (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/GROOVY-9891?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eric Milles resolved GROOVY-9891.
---------------------------------
    Fix Version/s: 4.0.0-alpha-3
       Resolution: Fixed

> Wrongly detected incompatible generic arguments for Java collections
> --------------------------------------------------------------------
>
>                 Key: GROOVY-9891
>                 URL: https://issues.apache.org/jira/browse/GROOVY-9891
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static compilation, Static Type Checker
>    Affects Versions: 3.0.7, 4.0.0-alpha-2
>            Reporter: Arthur Sengileyev
>            Assignee: Eric Milles
>            Priority: Major
>             Fix For: 4.0.0-alpha-3
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> When static type checks are enabled, then groovyc sometimes fails to assign compatible (with the same generic type selected) java Collection to java Iterable.
> This code fails to compile with groovyc (tested with 3.0.7 and 4.0.0-alpha-2)
> {code:groovy}
> @Grab(group='org.apache.kafka', module='kafka-clients', version='2.7.0')
> @Grab(group='org.apache.kafka', module='kafka-streams', version='2.7.0')
> import org.apache.kafka.streams.KafkaStreams
> import org.apache.kafka.common.MetricName
> import org.apache.kafka.common.Metric
> import java.lang.Iterable
> import java.util.Collections
> import java.util.Map
> import groovy.transform.CompileStatic
> @CompileStatic
> class TestStaticChecks {
>   KafkaStreams streams
>   void method1() {
>     Map<MetricName, ? extends Metric> metricsMap = Collections.emptyMap()
>     Iterable<? extends Metric> metrics = metricsMap.values()
>   }
>   void method2() {
>     Map<MetricName, ? extends Metric> metricsMap = streams.metrics()
>     Iterable<? extends Metric> metrics = metricsMap.values()
>   }
>   void method3() {
>     Iterable<? extends Metric> metrics = streams.metrics().values()
>   }
> }
> {code}
> method2 and method3 will fail to compile with error
> {code:java}
> [Static type checking] - Incompatible generic argument types. Cannot assign java.util.Collection <? extends org.apache.kafka.common.Metric> to: java.lang.Iterable <? extends org.apache.kafka.common.Metric>{code}
>  
> Same code reworked to Java compiles just fine with javac (when dependencies are in classapath)
> {code:java}
> import org.apache.kafka.streams.KafkaStreams;
> import org.apache.kafka.common.MetricName;
> import org.apache.kafka.common.Metric;
> import java.lang.Iterable;
> import java.util.Collections;
> import java.util.Map;
> class TestStaticChecks {
>   KafkaStreams streams;
>   void method1() {
>     Map<MetricName, ? extends Metric> metricsMap = Collections.emptyMap();
>     Iterable<? extends Metric> metrics = metricsMap.values();
>   }
>   void method2() {
>     Map<MetricName, ? extends Metric> metricsMap = streams.metrics();
>     Iterable<? extends Metric> metrics = metricsMap.values();
>   }
>   void method3() {
>     Iterable<? extends Metric> metrics = streams.metrics().values();
>   }
> }
>  {code}



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