当类实现相同的接口时，Lambda 表达式失败并出现 LambdaConversionException？ [复制]

Question

我很惊讶，为什么无法在运行时正确调用 lambda 表达式。是类型推断错误吗？ 工作示例是取消注释显式类型参数声明。

public class LambdaConversionTest {
    @Test
    public void whyDidLambdaExpressionFailsWithLambdaConversionException() {
        try {
            //      v--- when uncomment it, the behavior is what I expected
            Stream./*<Collector>*/of(new Robot(), new Puller())
                  .flatMapToInt(Collector::stream).sum();
            fail("fails with expected behavior");
        } catch (BootstrapMethodError why) {
            assertThat(why.getCause().getMessage()
                 ,containsString("Invalid receiver type interface "));
        }
    }

    interface Marker {
    }

    interface Collector {
        IntStream stream();
    }

    class Robot implements Collector, Marker {
        @Override
        public IntStream stream() {
            return IntStream.empty();
        }
    }

    class Puller implements Collector, Marker {
        @Override
        public IntStream stream() {
            return IntStream.empty();
        }
    }
}

Answer 1

对于this JDK bug这个特定的实例，需要注意的是，在Collector之后声明接口Marker不会失败

失败：

interface Marker {}

interface Collector {
    IntStream stream();
}

通过：

interface Collector {
    IntStream stream();
}
interface Marker {}