Union type dispatch bug

unionbug1.jl

typealias MatOrNothing{T} Union(AbstractMatrix{T}, Vector{None}, Nothing)

my_func{T}(A::MatOrNothing{T}) = println("my_func ok")

M = [1. 2. ; 3. 4.]

my_func(M) # works
my_func([]) # works
my_func(nothing) # fails

unionbug2.jl

typealias VecOrNothing{T} Union(AbstractVector{T}, Vector{None})
typealias MatOrNothing{T} Union(AbstractMatrix{T}, Vector{None})

my_func{T<:Real}(A::MatOrNothing{T}, B::MatOrNothing{T},
        C::MatOrNothing{T}) = println("my_func ok")

M = [ 2. 1. ; 1. 1. ]

my_func(M, M, M)
#my_func([], M, M) # fails
my_func(M, [], M)
my_func(M, M, [])
my_func(M, [], [])
#my_func([], M, []) # fails
#my_func([], [], M) # fails
my_func([], [], [])

# like my_func but C is VecOrNothing : fails more often
my_func2{T<:Real}(A::MatOrNothing{T}, B::MatOrNothing{T},
        C::VecOrNothing{T}) = println("my_func2 ok")

V = [ 0.; 0.]

my_func2(M, M, V)
#my_func2([], M, V) # fails
my_func2(M, [], V)
#my_func2(M, M, []) # fails
#my_func2(M, [], []) # fails
#my_func2([], M, []) # fails
#my_func2([], [], V) # fails
my_func2([], [], [])