ClassLoader leak in MethodHandle.asType()

[Peter Levart]

Hi,

I think there is a Class(Loader) leak in MethodHandle.asType() 
implementation. If for example some MH (say mhX) is long lived (because 
it is a system cached MH) and a client "generates" variants from it by 
invoking mhX.asType(newType) and the newType contains a type (either 
return type or parameter type) that is loaded by some child ClassLoader, 
then such derived MH is retained strongly from mhX via the 
MethodHandle.asTypeCache field. Until this field is overwriten by some 
other MH, child ClassLoader can not be GCed.

In case this one-element cache is needed to speed things up, it should 
be a WeakReference, like the following:

http://cr.openjdk.java.net/~plevart/jdk9-dev/MethodHandle.asTypeCacheLeak/webrev.01/


Regards, Peter