Selections within a projection are usually represented as sequences of classes extending `ColumnRef`. `ColumnName` is a common example as its instances are used to select tables columns.
Despite it is possible to find classes representing complex selections such as counts, there is not a class to represent functions (UDFs or built-in) calls.
On the other hand, `ColumnRef` is a sealed trait which implies that other projects' classes can't it.
It would be nice to include a `FunctionCallRef` within `ColumnRef.scala`. e.g:
It seems to be a PR easy to review and gives a great flexibly to the functions
Resolving as fixed because the PR has already been merged into branch b1.5.