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https://issues.apache.org/jira/browse/GROOVY-10979?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18134407#comment-18134407
]
Scott Murphy Heiberg commented on GROOVY-10979:
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The fix is in https://github.com/apache/groovy/pull/3089. Besides the method
reference in the description, it covers a closure or lambda passed for a
parameter declared with a type parameter that the call binds to a functional
interface. Under {{@CompileStatic}}, such a closure was stored unconverted, and
failed with a ClassCastException when used as the interface:
{code:groovy}
@groovy.transform.CompileStatic
String f() {
List<java.util.function.Supplier<String>> list = []
list.add { 'x' }
list[0].get() // ClassCastException: _f_closure1 cannot be cast to
java.util.function.Supplier
}
{code}
The same happens for {{map.put('k')}} with a closure, {{set}}, {{putIfAbsent}},
{{list <<}} with a closure, a constructor argument of a parameterized type, and
varargs. Seen in 4.0.33, 5.0.8 and 6.0.0.
> 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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