[jira] [Comment Edited] (GROOVY-10054) STC: Cannot infer lambda parameter types for a Stream Collector in a generic method

["Lyuben Atanasov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-10054?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17330861#comment-17330861 ] 

Lyuben Atanasov edited comment on GROOVY-10054 at 4/23/21, 3:26 PM:
--------------------------------------------------------------------

I have tried this without the method being generic as well. The following code still fails static type checking:
{code}
import java.util.stream.Collectors;

class Test {

	static interface Named {
		String getName();
	}

	Map<String, List<Named>> group(Set<Named> namedObjects) {
		return namedObjects.stream()
			.collect(Collectors.groupingBy(named -> named.getName()));
	}
	
}
{code}


was (Author: latanasov):
I have tried this without the method being generic as well. The following code still fails static type checking:
{code}
static interface Named {
		String getName();
	}

	Map<String, List<Named>> group(Set<Named> namedObjects) {
		return namedObjects.stream()
			.collect(Collectors.groupingBy(named -> named.getName()));
	}
}
{code}

> STC: Cannot infer lambda parameter types for a Stream Collector in a generic method
> -----------------------------------------------------------------------------------
>
>                 Key: GROOVY-10054
>                 URL: https://issues.apache.org/jira/browse/GROOVY-10054
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static Type Checker
>         Environment: OpenJDK8
>            Reporter: Lyuben Atanasov
>            Priority: Major
>
> This is a follow-up to GROOVY-10049. After the issue there had been fixed I was able to progress further with a chain of Stream method calls. However, the fix doesn't seem to cover the following case:
> {code}
> import java.util.stream.Collectors;
> class Test {
> 	static interface Named {
> 		String getName();
> 	}
> 	<T extends Named> Map<String, List<T>> group(Set<T> namedObjects) {
> 		return namedObjects.stream()
> 			.collect(Collectors.groupingBy(named -> named.getName()));
> 	}
> 	
> }
> {code}
> With static type checking enabled, an error is produced:
> {noformat}
> Script_ce61a645759c941d687680111f9bedbd.groovy: 11: [Static type checking] - Cannot find matching method java.lang.Object#getName(). Please check if the declared type is correct and if the method exists.
>  @ line 11, column 44.
>    ollectors.groupingBy(named -> named.getN
> {noformat}
> The difference between this issue and GROOVY-10049 is that the lambda passed here is not directly assigned to a Stream method. Of course, the issue is probably not limited to Collectors, but this is how I am able to reproduce it.
> I've tested this against https://github.com/apache/groovy/commit/e07f0112c5eff8d9c6828bd0ddb69e4b7f7cc1d6



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