User Defined N-ary Types, like Array{T,N}?

[Tamas_Papp]

I asked a similar question here, you may find the answers useful:

What are valid type parameters?

I am trying to stuff quite a bit of information into parameters of a type, in the hope that dispatching on this will create efficient code. Doing this, I ran into the question of what is allowed, exactly. Is the following correct: a value V is valid for a type parameter iff either isbits(V) isa(V, Symbol) isa(V, Type) Is there anything else? To make things concrete, what I am trying to encode as type parameters are a return type, and a Vector{Pair{Int,Type}}. The latter does not work, but …