fix setindex!

src/DirectProducts.jl

@@ -48,8 +48,9 @@ Base.size(g::DirectProductGroupElem) = size(g.elts)
 Base.linearindexing(::Type{DirectProductGroupElem}) = Base.LinearFast()
 Base.getindex(g::DirectProductGroupElem, i::Int) = g.elts[i]
 function Base.setindex!{T<:GroupElem}(g::DirectProductGroupElem{T}, v::T, i::Int)
-   p.part[i] = v
-   return p
+   parent(v) == parent(first(g.elts)) || throw("$g is not an element of $i-th factor of $(parent(G))")
+   g.elts[i] = v
+   return g
 end
 
 ###############################################################################