Invalid Range

ID

kotlin.invalid_range

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Kotlin

Tags

correctness, range

Description

Reports range expressions whose literal bounds produce an empty range:

  • a..b where a > b — the .. operator creates an ascending range; if start exceeds end, no iterations occur.

  • a..<b where a >= b — the exclusive upper bound makes the range empty when start equals or exceeds end.

Rationale

for (i in 10..5)  { }   // FLAW — empty, loop body never runs
for (i in 5..<5)  { }   // FLAW — empty (exclusive end equals start)
for (i in 10..<5) { }   // FLAW — empty

for (i in 1..10)  { }            // OK — ascending
for (i in 10 downTo 1) { }       // OK — explicit descending

Remediation

  • To iterate in descending order, use 10 downTo 1.

  • To iterate up to (excluding) n, use 0..<n.

  • Review the bounds to ensure the range covers the intended values.

References