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https://issues.apache.org/jira/browse/GROOVY-8045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17542214#comment-17542214
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Eric Milles commented on GROOVY-8045:
-------------------------------------
SC:
https://github.com/apache/groovy/commit/496748a118a51b2dad33f9fd03a8039a1cf0127d
> Implicit closure coercion doesn't work for elements of array of functional
> objects
> ----------------------------------------------------------------------------------
>
> Key: GROOVY-8045
> URL: https://issues.apache.org/jira/browse/GROOVY-8045
> Project: Groovy
> Issue Type: Bug
> Components: Compiler
> Affects Versions: 2.4.7
> Reporter: Dimitar Dimitrov
> Assignee: Eric Milles
> Priority: Major
> Labels: varargs
>
> Implicit closure coercion is described
> [here|http://groovy-lang.org/releasenotes/groovy-2.2.html] - it assumes that
> the closures don't need to be casted to functional types and the generic
> types will be inferred by the compiler.
> Here is one contrived case that works from Java (this is not production code
> and is writen explicitly for illustration purposes):
> {code}
> public class GroovyAccDemo {
> @SafeVarargs
> public static <T, R> Function<T, R> ensemble(Function<T, R>...
> hypotheses) {
> return t -> Arrays.stream(hypotheses)
> .map(v -> v.apply(t))
> .collect(Collectors.groupingBy(e -> e,
> Collectors.counting()))
> .entrySet()
> .stream()
> .max(Comparator.comparingLong(Map.Entry::getValue))
> .map(Map.Entry::getKey).orElseGet(() -> null);
> }
> public static void main(String[] args) {
> Function<Integer, Integer> foo = ensemble(
> i -> i*i,
> i -> i+i,
> i -> i*i - (i+i)
> );
> }
> }
> {code}
> Here the {{ensemble()}} method accepts a number of compatible functions and
> returns a single function that calls all hypotheses and returns the most
> popular result.
> The main method illustrates that we can use the {{ensemble()}} function with
> Java Lambdas without any explicit casts.
> If we try to do the same in Groovy, we'll get runtime error (or compile error
> if static compilation is enabled):
> {code}
> foo = GroovyAccDemo.<Integer, Integer> ensemble(
> { i -> i * i },
> { i -> i + i },
> { i -> i * i - (i + i) }
> );
> {code}
> We can make it work by explicitly coercing the closures like this:
> {code}
> foo = GroovyAccDemo.ensemble(
> { i -> i*i } as Function,
> { i -> i+i } as Function,
> { i -> i*i - (i+i ) } as Function
> );
> {code}
> This may seem as contrived use case, but it makes the use of certain API's
> more tedious from Groovy than from Java, which just feels wrong ;-)
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