E0054

Warning name: ambiguous_range_direction

The direction of an inclusive range is ambiguous.

This warning is emitted when an inclusive range such as 10..=0 is used in a loop. The endpoints suggest a descending loop, but the range syntax does not make the direction explicit.

Erroneous example

///|
pub fn values() -> Array[Int] {
  let result = []
  for i in 10..=0 {
    result.push(i)
  }
  result
}

Suggestion

Use explicit descending range syntax when the loop should count down.

///|
pub fn values() -> Array[Int] {
  let result = []
  for i in 10>=..0 {
    result.push(i)
  }
  result
}