Redundant call on 'Flow' type

Reports redundant calls on Flows from kotlinx.coroutines library.

This inspection detects two kinds of redundancy:

Redundant filter… calls on already filtered Flows. Functions such as filterNotNull() or filterIsInstance have sense only when they are called on receivers that have types distinct from the resulting one. Otherwise, such calls can be omitted as the result will be the same.
Redundant mapNotNull calls. mapNotNull is redundant when the transformation result is already guaranteed to be non-nullable. In that case, the NotNull suffix can be dropped (e.g., mapNotNull → map).

A quick-fix is available to omit the redundant call or replace it with a simpler alternative.

Examples:

  fun test(flow: Flow<String>) {
      val x = flow.filterNotNull() // can be simplified to 'flow'
      val y = flow.filterIsInstance<String>() // can be simplified to 'flow'
  }

  fun test(flow: Flow<Int>) {
      val x = flow.mapNotNull { it + 1 } // can be replaced with 'map'
  }

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.

UselessCallOnFlow

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 | Coroutine inspections

Inspection ID: UselessCallOnFlow

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 UselessCallOnFlow

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

IntelliJ IDEA 2026.1

Inspection Details
By default bundled with:	IntelliJ IDEA 2026.1, Qodana for JVM 2026.1,

Last modified: 31 March 2026