test.nim

type
  TData = tuple
    letters: seq[string]
    numbers: seq[int
    
const data: TData = (@["aa", "bb"], @[11, 22])

static:
  # the code works with the following line, because in semVarOrLet fitNode is used, which
  # produces nkHiddenConv for the tuple type
  var m: TData = data
  
  # but the following version won't work 
  # (no nkHiddenConv is produced and the VM crashes while executing it)
  # var m = data
  
  for x in m.letters:
    echo x