missing type in typecache?

[vtjnash]

there's a hack in object_id that allows recursive types to give a stable hash after the bind field gets corrupted at the end of creating a type. however, this might still be allowing the creation of invalid type objects:

julia> type A{T} end

julia> type B{T,S}
         a::A{B{Int,S}}
       end

julia> A.name.cache
svec()

julia> A.name.linearcache
svec() # expected A{B{Int}} here

julia> B.types[1] === A{B{Int}}
true # good

julia> A{B{Int}}.instance
A{B{Int64,S}}()

julia> A{B{Int}}.instance === B.types[1].instance
false #oops

fwiw, however, i don't seem to be able to find anything that this breaks