findMember

On Thu, Jul 2, 2009 at 11:52 AM, Lukas Rytz wrote:
> Hi,
>
> while fixing #2116, I found the following. Given
>
>   trait A { def f(x: Int): Object }
>   class B extends A { def f(x: Int): String = "x" }
>
> calling .findMember("f") returns
> - before erasure only the overrding method, f:(x: Int)String
> - after erasure both methods, f:(x: Int)String f:(x: Int)Object
>
> this is because matchesType is false after erasure. matchesType does
>   case _ =>
>     alwaysMatchSimple || tp1 =:= tp2
> where by default, "alwaysMatchSimple = !phase.erasedTypes".
>
>
> I fixed my ticked without touching findMember, but I'm not sure if the
> described behavior is a feature or we need to correct it.
>
It's a feature. After erasure, the two findMembers are no longer in
overriding relationship. (after erasure, overriding is the way the JVM
sees it). That's why we need bridge methods.

Cheers

On Thu, Jul 2, 2009 at 11:52 AM, Lukas Rytz<lukas.rytz@epfl.ch> wrote:
> Hi,
>
> while fixing #2116, I found the following. Given
>
>   trait A { def f(x: Int): Object }
>   class B extends A { def f(x: Int): String = "x" }
>
> calling <BClassInfo>.findMember("f") returns
> - before erasure only the overrding method, f:(x: Int)String
> - after erasure both methods, f:(x: Int)String <and> f:(x: Int)Object
>
> this is because matchesType is false after erasure. matchesType does
>   case _ =>
>     alwaysMatchSimple || tp1 =:= tp2
> where by default, "alwaysMatchSimple = !phase.erasedTypes".
>
>
> I fixed my ticked without touching findMember, but I'm not sure if the
> described behavior is a feature or we need to correct it.
>
It's a feature. After erasure, the two findMembers are no longer in
overriding relationship. (after erasure, overriding is the way the JVM
sees it). That's why we need bridge methods.

On Sun, Jul 5, 2009 at 10:48 PM, Lukas Rytz wrote:
>
>
> On Sun, Jul 5, 2009 at 22:34, martin odersky wrote:
>>
>> On Thu, Jul 2, 2009 at 11:52 AM, Lukas Rytz wrote:
>> > Hi,
>> >
>> > while fixing #2116, I found the following. Given
>> >
>> >   trait A { def f(x: Int): Object }
>> >   class B extends A { def f(x: Int): String = "x" }
>> >
>> > calling .findMember("f") returns
>> > - before erasure only the overrding method, f:(x: Int)String
>> > - after erasure both methods, f:(x: Int)String f:(x: Int)Object
>> >
>> > this is because matchesType is false after erasure. matchesType does
>> >   case _ =>
>> >     alwaysMatchSimple || tp1 =:= tp2
>> > where by default, "alwaysMatchSimple = !phase.erasedTypes".
>> >
>> >
>> > I fixed my ticked without touching findMember, but I'm not sure if the
>> > described behavior is a feature or we need to correct it.
>> >
>> It's a feature. After erasure, the two findMembers are no longer in
>> overriding relationship. (after erasure, overriding is the way the JVM
>> sees it). That's why we need bridge methods.
>
> But they are not in an overloading relationship, (Int):String is overriding
> (Int):Object, for instance

Before erasure, yes, of course. After erasure, no.

Cheers