Compiler bug? (was RE: A bit of fun with the Y combinator)

[Millies, Sebastian]

Hello Zhong,

I was about to test your cheat, but the compiler throws an exception (b106).

Here's the code:

import java.util.function.Function;

public class Zhong {

    public static void main(String args[]) {
        int n = Integer.parseInt(args[0]);
        System.out.println(n + "! = " + factorialZhong(n));
    }

    // Zhong Yu's variation, which is *really* cheating :-)
    private static <A,B> Function<A,B> fix2(Function<Function<A,B>, Function<A,B>> f)
    {
        return new Object()
        {
            Function<A,B> r = a -> f.apply(r).apply(a);
        }.r;
    }

    private static int factorialZhong(int n) {
        return  fix2(
                        // Recursive function generator
                        (Function<Integer,Integer> f) -> (Integer x) -> (x == 0) ? 1 : x * f.apply(x - 1)
                )
                .apply(
                        // Argument
                        n);
    }
}

Here's the error message:

Using javac 1.8.0-ea to compile java sources
java: An exception has occurred in the compiler (1.8.0-ea). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport)  after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report.  Thank you.
java: java.lang.ClassCastException: com.sun.tools.javac.code.Symbol$ClassSymbol cannot be cast to com.sun.tools.javac.code.Symbol$MethodSymbol

Can anyone reproduce that?

-- Sebastian

-----Original Message-----
From: Zhong Yu [mailto:zhong.j.yu at gmail.com]
Sent: Wednesday, September 11, 2013 6:36 PM
To: Millies, Sebastian
Cc: lambda-dev at openjdk.java.net
Subject: Re: A bit of fun with the Y combinator

My variation, which is *really* cheating :D

    public static <A,B> Function<A,B> fix2(Function<Function<A,B>, Function<A,B>> f)
    {
        return new Object()
        {
            Function<A,B> r = a -> f.apply(r).apply(a);
        }.r;
    }

Zhong Yu

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