What the lambda? #WTL

Fix.java

    static class JavaslangGoodies {

        static <T, R> MethodType getType(SerializableFunction<T, R> function) throws Exception {
            // FIXED, DON'T CHECK FOR CAPTURED LAMBDA PARAMETERS
            return getLambdaSignature(function);
        }

        static SerializedLambda getSerializedLambda(Serializable lambda) throws Exception {
            final Method method = lambda.getClass().getDeclaredMethod("writeReplace");
            method.setAccessible(true);
            return (SerializedLambda) method.invoke(lambda);
        }

        static MethodType getLambdaSignature(Serializable lambda) throws Exception {
            // FIXED, WAS: .getImplMethodSignature();
            final String signature = getSerializedLambda(lambda).getInstantiatedMethodType();
            return MethodType.fromMethodDescriptorString(signature, lambda.getClass().getClassLoader());
        }
    }

Test.java

import java.io.Serializable;
import java.lang.invoke.MethodType;
import java.lang.invoke.SerializedLambda;
import java.lang.reflect.Method;
import java.util.function.Function;

public class Test {

    public static void main(String[] args) throws Exception {

        SerializableFunction<Integer, Integer> add1 = i -> i + 1;
        System.out.println(JavaslangGoodies.getType(add1)); // (Integer)Integer

        SerializableFunction<Integer, Integer> add2 = Test::add;
        System.out.println(JavaslangGoodies.getType(add2)); // (Integer)Integer

        SerializableFunction<Integer, Integer> add3 = add1::apply;
        System.out.println(JavaslangGoodies.getType(add3)); // (Object)Object

    }

    static Integer add(Integer i) {
        return i + 1;
    }

    interface SerializableFunction<T, R> extends Function<T, R>, Serializable {
        default int arity() {
            return 1;
        }
    }

    static class JavaslangGoodies {

        static <T, R> MethodType getType(SerializableFunction<T, R> function) throws Exception {
            final MethodType methodType = getLambdaSignature(function);
            return methodType.dropParameterTypes(0, methodType.parameterCount() - function.arity());
        }

        static SerializedLambda getSerializedLambda(Serializable lambda) throws Exception {
            final Method method = lambda.getClass().getDeclaredMethod("writeReplace");
            method.setAccessible(true);
            return (SerializedLambda) method.invoke(lambda);
        }

        static MethodType getLambdaSignature(Serializable lambda) throws Exception {
            final String signature = getSerializedLambda(lambda).getImplMethodSignature();
            return MethodType.fromMethodDescriptorString(signature, lambda.getClass().getClassLoader());
        }
    }
}