IncompatibleClassChangeError example

[Paul Sandoz]

Hi Peter.

Replace "this.get()" with just "get()" or "Value.this.get()" and it runs OK, but i am not even sure it is entirely correct looking at the diffs of javap output of not this vs. this.

e.g. public vs. private static interface for the method lambda$0.


When using "this.get()" the following method is generated by javac:

  private static java.lang.Object lambda$0(java.util.function.Function);
    flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0       
         1: aload_0       
         2: invokeinterface #4,  1            // InterfaceMethod get:()Ljava/lang/Object;
         7: invokeinterface #5,  2            // InterfaceMethod java/util/function/Function.apply:(Ljava/lang/Object;)Ljava/lang/Object;
        12: areturn       
      LineNumberTable:
        line 1: 0
        line 9: 2

To my untrained eye that looks dodgy with the two aload_0 instructions, it's trying to invoked the Value.get method on the Function interface. I would expect the method to have two args.

Paul.

16c16
<         #36 invokeinterface Test$Value.lambda$0:(Ljava/util/function/Function;)Ljava/lang/Object;
---
>         #36 invokestatic Test$Value.lambda$0:(Ljava/util/function/Function;)Ljava/lang/Object;
23c23
<    #2 = InvokeDynamic      #0:#38         //  #0:lambda$:(LTest$Value;Ljava/util/function/Function;)Ljava/util/function/Supplier;
---
>    #2 = InvokeDynamic      #0:#38         //  #0:lambda$:(Ljava/util/function/Function;)Ljava/util/function/Supplier;
57c57
<   #36 = MethodHandle       #9:#49         //  invokeinterface Test$Value.lambda$0:(Ljava/util/function/Function;)Ljava/lang/Object;
---
>   #36 = MethodHandle       #6:#49         //  invokestatic Test$Value.lambda$0:(Ljava/util/function/Function;)Ljava/lang/Object;
59c59
<   #38 = NameAndType        #51:#52        //  lambda$:(LTest$Value;Ljava/util/function/Function;)Ljava/util/function/Supplier;
---
>   #38 = NameAndType        #51:#52        //  lambda$:(Ljava/util/function/Function;)Ljava/util/function/Supplier;
73c73
<   #52 = Utf8               (LTest$Value;Ljava/util/function/Function;)Ljava/util/function/Supplier;
---
>   #52 = Utf8               (Ljava/util/function/Function;)Ljava/util/function/Supplier;
95c95
<       stack=4, locals=2, args_size=2
---
>       stack=3, locals=2, args_size=2
98,102c98,101
<          4: aload_0       
<          5: aload_1       
<          6: invokedynamic #2,  0              // InvokeDynamic #0:lambda$:(LTest$Value;Ljava/util/function/Function;)Ljava/util/function/Supplier;
<         11: invokespecial #3                  // Method Test$SuppliedValue."<init>":(Ljava/util/function/Supplier;)V
<         14: areturn       
---
>          4: aload_1       
>          5: invokedynamic #2,  0              // InvokeDynamic #0:lambda$:(Ljava/util/function/Function;)Ljava/util/function/Supplier;
>         10: invokespecial #3                  // Method Test$SuppliedValue."<init>":(Ljava/util/function/Supplier;)V
>         13: areturn       
107,108c106,107
<                0      15     0  this   LTest$Value;
<                0      15     1 mapper   Ljava/util/function/Function;
---
>                0      14     0  this   LTest$Value;
>                0      14     1 mapper   Ljava/util/function/Function;
111,112c110,111
<             0      15     0  this   LTest$Value<TT;>;
<             0      15     1 mapper   Ljava/util/function/Function<-TT;+TR;>;
---
>             0      14     0  this   LTest$Value<TT;>;
>             0      14     1 mapper   Ljava/util/function/Function<-TT;+TR;>;
115,116c114,115
<   public java.lang.Object lambda$0(java.util.function.Function);
<     flags: ACC_PUBLIC, ACC_SYNTHETIC
---
>   private static java.lang.Object lambda$0(java.util.function.Function);
>     flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
118,119c117,118
<       stack=2, locals=2, args_size=2
<          0: aload_1       
---
>       stack=2, locals=1, args_size=1
>          0: aload_0       
127,132d125
<       LocalVariableTable:
<         Start  Length  Slot  Name   Signature
<                0      13     0  this   LTest$Value;
<       LocalVariableTypeTable:
<         Start  Length  Slot  Name   Signature
<             0      13     0  this   LTest$Value<TT;>;



On Jun 18, 2013, at 9:29 AM, Peter Levart <peter.levart at gmail.com> wrote:

> Just a reminder that the following problem is still present...
> 
> Regards, Peter
> 
> On 06/09/2013 05:24 PM, Peter Levart wrote:
>> Hi,
>> 
>> When I compile and run the following program with the latest tip of 
>> lambda repo:
>> 
>> 
>> import java.util.function.Function;
>> import java.util.function.Supplier;
>> 
>> public class ICCEBug {
>> 
>>    interface Value<T> extends Supplier<T> {
>>        default <R> Value<R> map(Function<? super T, ? extends R> 
>> mapper) {
>>            return new SuppliedValue<>(() -> mapper.apply(this.get()));
>>        }
>>    }
>> 
>>    static class SuppliedValue<T> implements Value<T> {
>>        private final Supplier<T> supplier;
>> 
>>        SuppliedValue(Supplier<T> supplier) {
>>            this.supplier = supplier;
>>        }
>> 
>>        @Override
>>        public T get() {
>>            return supplier.get();
>>        }
>>    }
>> 
>>    public static void main(String[] args) {
>>        Value<String> name = () -> "Peter";
>>        Value<String> sentence = name.map(nm -> "Hello " + nm + "!");
>>        System.out.println(sentence.get());
>>    }
>> }
>> 
>> 
>> 
>> ... I get the following exception:
>> 
>> Exception in thread "main" java.lang.IncompatibleClassChangeError: 
>> Class ICCEBug$$Lambda$2 does not implement the requested interface 
>> ICCEBug$Value
>>    at ICCEBug$Value.lambda$0(ICCEBug.java:17)
>>    at ICCEBug$Value$$Lambda$3.get(Unknown Source)
>>    at ICCEBug$SuppliedValue.get(ICCEBug.java:30)
>>    at ICCEBug.main(ICCEBug.java:37)
>> 
>> 
>> 
>> It looks like something is not compiled correctly.
>> 
>> Regards, Peter
>> 
> 
>