wip: implemements `@`

[ringabout]

It seems that type inference is not good enough for empty array in templates. I'm struggling with

import std/tables

template accResult() =
  var s = newTable[int, seq[int]]()

  var x = 2
  discard mgetOrPut(s, x, @[])

  # var x = newSeq[int]()
  # x = @[]

proc splitWhitespace*() =
  accResult()

splitWhitespace()