union of tuples is broken

[ajkeller34]

On 0.6.2:

julia> union((1,2))
2-element Array{Int64,1}:
 1
 2

0.7.0-DEV.3222:

julia> union((1,2))
ERROR: MethodError: no method matching emptymutable(::Tuple{Int64,Int64}, ::Type{Int64})
...

You can try to take the union of multiple tuples (e.g. union((1,2), (3,))) and that doesn't work either. I haven't bisected to be sure, but this broke quite recently so I think #23528 is responsible.

cc @rfourquet

[rfourquet]

Thanks for reporting! emptymutable was meant to have a default fall-back, but I forgot about it and no test caught this.