[css-easings-2] When does a `linear()` includes a point with a null `input`?

[cdoublev]

https://drafts.csswg.org/css-easing-2/#create-a-linear-easing-function

5. For runs of items in function’s points that have a null input, [...]

Can you please add an example when this happens?

I cannot figure it out.

function createLinearEasingFunction(list) {
  const points = []
  const fn = { points }
  let largestInput = -Infinity
  list.forEach((stop, index) => {
    const [progress, time] = stop
    const point = { input: null, output: progress }
    points.push(point)
    if (isOmitted(time)) {
      if (index === 0) {
        point.input = 0
        largestInput = 0
      } else {
        point.input = Math.max(1, largestInput)
      }
      return
    }
    const [start, end] = time
    largestInput = point.input = Math.max(start / 100, largestInput)
    if (end) {
      const input = largestInput = Math.max(end / 100, largestInput)
      const extraPoint = { input, output: progress }
      points.push(extraPoint)
    }
  })
}

[cdoublev]

Oh, this happens for interleaved points that are specified only with an output value. I guess the coffee did not reached my brain because this seems obvious and not worth a more specific note, therefore I close this issue.