Julia: Ayuda a la regresión para Rational en 0.6

En Julia 0.5:

help?> Rational
search: Rational rationalize Irrational SerializationState permutations

  No documentation found.

  Summary:

  immutable Rational{T<:Integer} <: Real

  Fields:

  num :: T<:Integer
  den :: T<:Integer

mientras que en Julia 0.6

help?> Rational
search: Rational rationalize Irrational SerializationState Factorization

  No documentation found.

  Base.Rational is of type UnionAll.

  Summary:

  struct UnionAll <: Type{T}

  Fields:

  var  :: TypeVar
  body :: Any

Los detalles en 0.6 son incorrectos:

julia> Rational <: UnionAll
false

julia> fieldnames(Rational)
2-element Array{Symbol,1}:
 :num
 :den