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https://issues.apache.org/jira/browse/GROOVY-10979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18131774#comment-18131774
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Scott Murphy Heiberg commented on GROOVY-10979:
-----------------------------------------------
apache/groovy#3026 (https://github.com/apache/groovy/pull/3026) fixes this in
commit f3bf02ac9e: the type checker now resolves a parameter declared with a
type parameter for the call, from the receiver, the type arguments and the
other arguments, and checks a closure, lambda or method reference argument
against the functional interface it is bound to. {{x.<Function<String,
Integer>>reduce(Test::m, y, z)}} and {{x.reduce(Test::m, y, z)}} compile and
run; MethodReferenceTest.testNotFunctionalInterface3 now runs them.
> Cannot provide method reference to a type parameter instantiated with a SAM
> type
> --------------------------------------------------------------------------------
>
> Key: GROOVY-10979
> URL: https://issues.apache.org/jira/browse/GROOVY-10979
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Reporter: Thodoris Sotiropoulos
> Priority: Minor
>
> I have the following program
> {code}
> import java.util.function.*;
> import java.util.stream.*;
> public class Test {
> public static void test() {
> Stream<Number> x = null;
> BiFunction<Function<String, Integer>, Number, Function<String,
> Integer>> y = null;
> BinaryOperator<Function<String, Integer>> z = null;
> x.<Function<String, Integer>>reduce(Test::m, y, z); // fails
> x.reduce(Test::m, y, z); // fails
> x.reduce((d) -> 1, y, z); // works
> }
> public static Integer m(String x) { return 1; }
> }
> {code}
> h3. Actual behavior
> {code}
> org.codehaus.groovy.control.MultipleCompilationErrorsException: startup
> failed:
> test.groovy: 12: The argument is a method reference, but the parameter type
> is not a functional interface
> @ line 12, column 43.
> ction<String, Integer>>reduce(Test::m, y
> ^
> test.groovy: 13: The argument is a method reference, but the parameter type
> is not a functional interface
> @ line 13, column 16.
> x.reduce(Test::m, y, z); // fails
> ^
> 2 errors
> {code}
> h3. Expected behavior
> Compile successfully
> Tested against master (commit: 55c6edfd81a64ce759357a3976070c0811bff637)
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