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Suspicious back reference

Reports back references that will not be resolvable at runtime. This means that the back reference can never match anything. A back reference will not be resolvable when the group is defined after the back reference, or if the group is defined in a different branch of an alternation.

Example of a group defined after its back reference:

\1(abc)

Example of a group and a back reference in different branches:

a(b)c|(xy)\1z

New in 2022.1

Inspection Details

Available in:

AppCode 2023.3, CLion 2023.3, DataGrip 2023.3, DataSpell 2023.3, GoLand 2023.3, IntelliJ IDEA 2023.3, JetBrains Rider 2023.1, PhpStorm 2023.3, PyCharm 2023.3, Qodana for .NET 2023.1, Qodana for JS 2023.3, Qodana for JVM 2023.3, Qodana for PHP 2023.3, Qodana for Ruby 2023.3, RubyMine 2023.3, WebStorm 2023.3

Plugin:

IDEA CORE, 233.SNAPSHOT

Last modified: 13 July 2023