E4137

Range operators are currently only supported in for .. in loops.

This means you cannot save the range operator in a variable or use it later in other contexts.

Erroneous example

fn main {
  let range = 0..<10 // Error: Range operators are currently only supported in `for .. in` loops.
}

Suggestion

One can use the until method to generate a range of numbers:

fn main {
  let range = (0).until(10)
  for i in range {
    println(i)
  }
}