Argument could be converted to 'Set' to improve performance

Detects the function calls that could work faster with an argument converted to Set.

Operations like 'minus' or 'intersect' are more effective when their argument is a set. An explicit conversion of an Iterable<T> or an Array<T> into a Set<T> can often make code more effective.

The quick-fix adds an explicit conversion to the function call.

Example:

  fun <T> f(a: Iterable<T>, b: Iterable<T>): Int =
      a.intersect(b).size

After the quick-fix is applied:

  fun <T> f(a: Iterable<T>, b: Iterable<T>): Int =
      a.intersect(b.toSet()).size

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.

ConvertArgumentToSet

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 | Other problems

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 ConvertArgumentToSet

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