these signatures are not matched correctly

[JeffBezanson]

Stefan found this a while ago. These two signatures:

assign{K,V}(h::HashTable{K,V}, v::V, key::K)
assign{K,V}(h::HashTable{K,V}, v, k) = assign(h, convert(V,v), convert(K,k))

are not dispatched correctly. I believe the second one called itself.

The root of the problem is that jl_type_match doesn't handle invariant vs. covariant contexts correctly, unlike type intersection.

[JeffBezanson]

As part of commit 7d0c9e1 I made these sort correctly, so I consider this fixed to the extent possible.
The remaining issue is that HashTable{Any,Any} will not match the first signature since the container's element type is never the same as the argument's type. But for the time being this is the intended behavior.