Nim 1.6.2 : silent program rejection

[ElegantBeef]

It seems the generic cache is not respected for this example which results in 
an endless loop. The following is enough to cause a seg fault. 
    
    
    type
      PCset[T,V] = object of RootObj
      PTa[V] = object of PCset[PTa[V], V]
    
    var a: PTa[int]
    
    
    Run