[9] RFR (S) 8057656: Improve MethodType.isCastableTo() & MethodType.isConvertibleTo() checks

[Vladimir Ivanov]

Thank you, Paul.

Best regards,
Vladimir Ivanov

On 9/9/14, 2:05 PM, Paul Sandoz wrote:
> On Sep 5, 2014, at 6:42 PM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:
>>>> http://cr.openjdk.java.net/~vlivanov/8057656/webrev.00/
>>>> https://bugs.openjdk.java.net/browse/JDK-8057656
>>>>
>>>
>>>   854         if (!canConvert(returnType(), newType.returnType()))
>>>   855             return false;
>>>   856         Class<?>[] srcTypes = newType.ptypes;
>>>   857         Class<?>[] dstTypes = ptypes;
>>>
>>> Are the src and dst the wrong way around?
>>>
>>>     srcTypes = ptypes
>>>     dstTypes = newType.ptypes
>> No, they are right. Parameters and return type conversions have opposite directions.
>>
>
> Doh! of course, silly me.
>
>
>>>   896     private static boolean canCast(Class<?> src, Class<?> dst) {
>>>   897         if (src.isPrimitive() && !dst.isPrimitive()) {
>>>   898             if (dst == Object.class || dst.isInterface())  return true;
>>>
>>> How come if the src is primitive and the dst is an interface it returns true for any interface? I guess there are subtly different rules here for casting and conversion.
>> There are 2 types of converstions: MH.asType() and MHs.explicitCastArguemnts() with more relaxed semantics.
>> One of the differences is that interfaces are coerced to Object, since verifier allows any interface to be treated as Object.
>>
>> Your questions reminded me about related changes waiting in the queue and I decided to include then here.
>>
>> Updated webrev:
>> http://cr.openjdk.java.net/~vlivanov/8057656/webrev.01/
>>
>> Got rid of MT.isCastableTo(). MHs.explicitCastEquivalentToAsType() is used instead. Also, it has detailed overview of differences between MT.asType() and MHs.explicitCastArguments().
>>
>
> Much clearer IMO.
>
> +1
>
> Paul.
>