Ambiguous logical expressions in 'when' branches since 1.7

Reports ambiguous logical expressions in when branches which cause compilation errors in Kotlin 1.8 and later.

  fun Int.matches(strict: Boolean): Boolean = when (strict) {
      true -> this == 6
      this in (4..7) -> true // is ambiguous
      else -> false
  }

After the quick-fix is applied:

  fun Int.matches(strict: Boolean): Boolean = when (strict) {
      true -> this == 6
      (this in (4..7)) -> true // wrapped in parentheses
      else -> false
  }

Inspection is available for Kotlin language level starting from 1.7.

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.

AmbiguousExpressionInWhenBranchMigration

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 | Migration

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection AmbiguousExpressionInWhenBranchMigration

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025