Definition types in Library

src/main/scala/leon/utils/Library.scala

@@ -7,12 +7,12 @@ import purescala.Definitions._
 import purescala.DefOps.searchByFullName
 
 case class Library(pgm: Program) {
-  lazy val List = lookup("leon.collection.List")
-  lazy val Cons = lookup("leon.collection.Cons")
-  lazy val Nil  = lookup("leon.collection.Nil")
-
-  lazy val String = lookup("leon.lang.string.String")
+  lazy val List = lookup("leon.collection.List") collect { case acd : AbstractClassDef => acd }
+  lazy val Cons = lookup("leon.collection.Cons") collect { case ccd : CaseClassDef => ccd }
+  lazy val Nil  = lookup("leon.collection.Nil") collect { case ccd : CaseClassDef => ccd }
 
+  lazy val String = lookup("leon.lang.string.String") collect { case ccd : CaseClassDef => ccd }
+  
   def lookup(name: String): Option[Definition] = {
     searchByFullName(name, pgm)
   }