generics - Inconsistency with scala reflection library -

i'm having trouble understanding why using scala's runtime reflection in 2.11.1 gives me seemingly inconsistent results.

i trying inspect type of field contained in java object, one:

import java.util.list; import java.util.arraylist;  public class example {   private list<integer> listofints;    public example () {     listofints = new arraylist<integer>();   }   } 

now suppose have scala program tries reason type of field inside "example:"

import java.lang.class import java.lang.reflect.field import java.util.list import scala.reflect.runtime.{ universe => ru }  object inspect extends scala.app {   val example = new example    val cls = example.getclass   val listfield = cls.getdeclaredfield("listofints")    println(islisttype(listfield)) // prints false    println(islisttype(listfield)) // prints true, subsequent calls    def islisttype (field: field): boolean = {     /*       function returns whether type of field list.       based on examples @ http://docs.scala-lang.org/overviews/reflection/environment-universes-mirrors.html     */     val fieldcls = field.gettype      val mirror: ru.mirror = ru.runtimemirror(getclass.getclassloader)     val fieldsym: ru.classsymbol = mirror.classsymbol(fieldcls)     val fieldtype: ru.type = fieldsym.totype       (fieldtype <:< ru.typeof[list[_]])   }   } 

in particular code snippet, first call islisttype returns false, , second returns true. if switch type operator <:< =:=, first call returns true, , second false.

i have similar function in larger code body, , have found when function part of static object, behavior occurs. not happen when using unparameterized classes. while intended function pure, not case. further experimentation has shown there persistent state held somewhere. if replace islisttype function straightline code, this:

... val example = new example    val cls = example.getclass val listfield = cls.getdeclaredfield("listofints") val fieldcls = listfield.gettype  val mirror: ru.mirror = ru.runtimemirror(getclass.getclassloader) val fieldsym: ru.classsymbol = mirror.classsymbol(fieldcls) val fieldtype: ru.type = fieldsym.totype   println(fieldtype <:< ru.typeof[list[_]]) // prints false println(fieldtype <:< ru.typeof[list[_]]) // prints false 

but if reassign field type after <:< operator, this:

// replace under fieldsym assignment var fieldtype: ru.type = fieldsym.totype  println(fieldtype <:< ru.typeof[list[_]]) // prints false  fieldtype = fieldsym.totype  println(fieldtype <:< ru.typeof[list[_]]) // prints true 

while reassigning field type before <:< operator gives this:

// replace under fieldsym assignment var fieldtype: ru.type = fieldsym.totype  fieldtype = fieldsym.totype   println(fieldtype <:< ru.typeof[list[_]]) // prints false println(fieldtype <:< ru.typeof[list[_]]) // prints false 

does understand i'm doing wrong here, or @ least have way around this?

the reflection library based on compiler, crying shame. people should demand better. anyway, how is.

here's sample ticket 2 years ago. https://issues.scala-lang.org/browse/si-6826

there persistent state held somewhere

there's nothing but.

addendum: dizzying experience, page through selection of 355 open reflection tickets.