Cascade 'if' can be replaced with 'when'

Reports if statements with three or more branches that can be replaced with the when expression.

Example:

  fun checkIdentifier(id: String) {
      fun Char.isIdentifierStart() = this in 'A'..'z'
      fun Char.isIdentifierPart() = isIdentifierStart() || this in '0'..'9'

      if (id.isEmpty()) {
          print("Identifier is empty")
      } else if (!id.first().isIdentifierStart()) {
          print("Identifier should start with a letter")
      } else if (!id.subSequence(1, id.length).all(Char::isIdentifierPart)) {
          print("Identifier should contain only letters and numbers")
      }
  }

The quick-fix converts the if expression to when:

  fun checkIdentifier(id: String) {
      fun Char.isIdentifierStart() = this in 'A'..'z'
      fun Char.isIdentifierPart() = isIdentifierStart() || this in '0'..'9'

      when {
          id.isEmpty() -> {
              print("Identifier is empty")
          }
          !id.first().isIdentifierStart() -> {
              print("Identifier should start with a letter")
          }
          !id.subSequence(1, id.length).all(Char::isIdentifierPart) -> {
              print("Identifier should contain only letters and numbers")
          }
      }
  }

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

CascadeIf

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Kotlin | Style issues

Inspection Details
By default bundled with:	IntelliJ IDEA 2024.3, Qodana for JVM 2024.3,
Can be installed with plugin:	Kotlin, 243.26483-IJ

01 April 2025