Seq API parsing issue

[ericzhang6222]

1.With code //seq.join(",",{}) and //seq.join(",",[]), both {} and [] are parsed to rel.GenericSet, I think [] should be pared to rel.Array.
2.With code //seq.join(",",["", "", ""]), "" is parsed to rel.GenericSet too, "" should be parsed to rel.String.

[ericzhang6222]

@marcelocantos can you help to confirm?

[ChloePlanet]

Not a bug, all empty sets are the same. "", {} and [] are indistinguishable.

[marcelocantos]

The suggested change would make it easier to implement the given functions under normal circumstances. However, since all empty sets are identical (that is, there is only one kind of empty set), the expressions //seq.join(",",{}) and //seq.join(",",[]) mean exactly the same thing and produce exactly the same result: {}. This is why the empty array is modelled as rel.None internally. I'm even thinking to add a Go type that represents the empty set so that GenericSet isn't considered special.