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Useless call on collection type

Reports filter… calls from the standard library on already filtered collections.

Several functions from the standard library 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.

Remove redundant call quick-fix can be used to amend the code automatically.


fun test(list: List<String>) { val x = list.filterNotNull() // quick-fix simplifies to 'list' val y = list.filterIsInstance<String>() // quick-fix simplifies to 'list' }

Inspection Details

By default bundled with:

IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,

Can be installed with plugin:

Kotlin, 241.16690-IJ

Last modified: 29 April 2024