VerifyError was thrown by "() -> f1.invoke()"

[bitter_fox]

Hi.

VerifyError was thrown with the message, "Exception in thread "main"
java.lang.VerifyError: Bad return type in method
Main$3.invoke()Ljava/lang/String; at offset 9".
(Compiling is in success)

This is the test program.

// code

public class Main
{
    interface Functional0<RET>
    {
        public RET invoke();
    }

    public static String getString()
    {
        return "Hello Lambda World";
    }

    public static void main(String[] args)
    {
        Functional0<String> f1 = Main#getString;
        Functional0<String> f2 = () -> (String)f1.invoke(); // OK
        Functional0<String> f3 = () -> f1.invoke(); // VerifyError

        Functional0<String> f4 = f1#invoke; // VerifyError
    }
}

Should this program be VerifyError?

I investigated the byte-code by jad.

--------------------Main$2(f2)--------------------
// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3) disassembler
// Source File Name:   Main.java


static class Main$2
    implements nctional0
{

    Main$2(nctional0 nctional0)
    {
    //    0    0:aload_0
    //    1    1:invokespecial   #2   <Method void Object()>
    //    2    4:aload_0
    //    3    5:aload_1
    //    4    6:putfield        #3   <Field Main$Functional0 cap$0>
    //    5    9:return
    }

    public String invoke()
    {
    //    0    0:aload_0
    //    1    1:getfield        #3   <Field Main$Functional0 cap$0>
    //    2    4:invokeinterface #4   <Method Object
Main$Functional0.invoke()>
    //    3    9:checkcast       #5   <Class String>
    //    4   12:areturn
    }

    public volatile Object invoke()
    {
    //    0    0:aload_0
    //    1    1:invokevirtual   #1   <Method String invoke()>
    //    2    4:areturn
    }

    nctional0 cap$0;
}

--------------------Main$3(f3)--------------------
// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3) disassembler
// Source File Name:   Main.java


static class Main$3
    implements nctional0
{

    Main$3(nctional0 nctional0)
    {
    //    0    0:aload_0
    //    1    1:invokespecial   #2   <Method void Object()>
    //    2    4:aload_0
    //    3    5:aload_1
    //    4    6:putfield        #3   <Field Main$Functional0 cap$0>
    //    5    9:return
    }

    public String invoke()
    {
    //    0    0:aload_0
    //    1    1:getfield        #3   <Field Main$Functional0 cap$0>
    //    2    4:invokeinterface #4   <Method Object
Main$Functional0.invoke()>
    //    3    9:areturn
    }

    public volatile Object invoke()
    {
    //    0    0:aload_0
    //    1    1:invokevirtual   #1   <Method String invoke()>
    //    2    4:areturn
    }

    nctional0 cap$0;
}

I guess the cause of VerifyError is there is no checkcast in Main$3#String
invoke().

Is this problem already known?
Please check this.

Thank you.
bitter_fox