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https://issues.apache.org/jira/browse/GROOVY-10047?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eric Milles updated GROOVY-10047:
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Fix Version/s: 3.0.9
> STC infers Closure instead of SAM for method references
> -------------------------------------------------------
>
> Key: GROOVY-10047
> URL: https://issues.apache.org/jira/browse/GROOVY-10047
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Affects Versions: 3.0.8
> Reporter: Christopher Smith
> Assignee: Eric Milles
> Priority: Major
> Fix For: 4.0.0-beta-1, 3.0.9
>
>
> I thought I had reported this earlier, but I couldn't find the duplicate.
> When using a very basic method reference, the STC is inferring {{Closure}} as
> the type instead of the proper functional interface. Explicitly specify
> {{as}} works, which I think might not have with the {{::}} syntax previously.
> In my particular case, I'm wrapping a {{List<DeleteItemRequest>}} (from the
> Amazon SDK 2 DynamoDB client) into a {{Map<String, List<DeleteItemRequest>>}}
> to feed to its batch API. The line is:
> {code:groovy}
> def requestItems = batch.stream().collect(toMap(DeleteItemRequest::tableName,
> List::of))
> {code}
> In contrast to GROOVY-9881, it seems the STC is correctly identifying the
> signature, at least, but it's inferring {{Closure}} where {{Function}} is
> expected:
> {code}
> /home/christopher/path/CleanupHandler.groovy: 50: [Static type checking] -
> Cannot call <T,K,U>
> java.util.stream.Collectors#toMap(java.util.function.Function <? super T, ?
> extends K>, java.util.function.Function <? super T, ? extends U>) with
> arguments [groovy.lang.Closure <java.lang.String>, groovy.lang.Closure
> <java.util.List>]
> {code}
> Adding an explicit {{as Function}} to each reference fixes the problem
> (though it is still using {{getMethodPointer}} instead of real method
> references).
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