False positive for S1854 "Unused assignments should be removed"

SonarQube for IDE
1
  • Operating system: Linux
  • IDE name and flavor/env:
    Using sonarlint as Java library via gradle:
    {module = “org.sonarsource.sonarlint.core:sonarlint-core”, version = “9.8.0.76914” }
    { module = “org.sonarsource.java:sonar-java-plugin”, version = “7.31.0.34839” }

Getting a false positive for the following code:

package com;

public class BCid51 {
  void HJid232(EJid229 YHid199, Yid24.RIid217<MBid37> QJid241) {
    for (XFid148 RJid242 : YHid199.WIid222()) {
      int DHid178;
      if (Fid5.BGid151() == CGid152.DGid153) {
        MBid37 IHid183 = RJid242.OFid139();
        IHid183.AGid150();
      }
    }
  }
}

Message is for line 8:

Remove this useless assignment to local variable IHid183

That’s obviously wrong as the object is used in the next line.

1 Like
Sonar Community Roundup: April 27 - May 3
4

Hi David,

My assumption is: We have 2 problems:

  1. The project does not have a valid classpath and some of the types are not resolved properly.
  2. The rule S1854 raises false positives when some types are not resolved. We should remove this noise, I created this ticket SONARJAVA-4960.

Probably, by fixing the classpath used by the analysis, you should be able to remove those false positives.
And if it’s not related to a classpath problem, you should be able to provide a small reproducer using only known types.

Thanks for your feedback,
Alban

8

Hi Alban,

I have the same false positive issue with rule S1854. I am writing java code on Windows 11 in IntelliJ. I use IntelliJ version 2024.1(.4) with SonarLint plugin version 10.9.0(.79423)

I don’t think there are problems with the classpath (when I ctrl + click on the type of the parameter instance from the reproducible example below, IntelliJ takes me to the correct definition of the class). A smaller reproducible example can be found below:
Random file:

public String doSomething(AClass.BClass<String> instance) {
    String c = "Hi"; // Rule S1854
    return instance.b + c;
}

File AClass.java:

public class AClass {
    public class BClass<T> {
        public T b;
    }
}

Please let me know if you would prefer if I create a new topic for this.

Edit: A couple of days later I reopen the same file and see that the sonarlint warnings have disappeared.

Best regards,
Simon

12

Same situation with an enhanced switch setting a local variable:

// all the switch statement is signaled as "useless assignment"
final DocumentStatus status = switch(event) {
  case SimpleStatusChangedEvent ignored → DocumentStatus.DOC01;
  case NeedClientRecheckEvent ignored -> DocumentStatus.DOC02;
};
document.setStatus(status);
// ...
documentRepository.save(document);

If it can be of any help, for me those are the specs:

IntelliJ IDEA 2025.3
Build #IU-253.28294.334, built on December 5, 2025
Source revision: f50d587f27abb
Runtime version: 21.0.8+9-b1163.69 amd64 (JCEF 137.0.17)
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.awt.windows.WToolkit
Windows 11.0
GC: ZGC Minor Cycles, ZGC Minor Pauses, ZGC Major Cycles, ZGC Major Pauses
Memory: 2048M
Cores: 12
Registry:
vcs.log.index.enable=true
ide.experimental.ui=true
llm.jcp.analytics.endpoint.url=https://api.jetbrains.cloud/analytics/events/push
Non-Bundled Plugins:
com.intellij.notebooks.core (253.28294.337)
com.intellij.debugger.collections.visualizer (253.28294.336)
Subversion (253.28294.351)
org.editorconfig.editorconfigjetbrains (253.28294.335)
com.intellij.javaee (253.28294.336)
fr.pralexio.perplexityintegration (1.5)
com.intellij.spring (253.28294.351)
com.haulmont.jpab (253.28294.251)
intellij.jupyter (253.28294.337)
com.intellij.ml.llm (253.28294.337)
org.mapstruct.intellij (1.9.1)
com.intellij.mcpServer (253.28294.336)
org.sonarlint.idea (11.6.0.83783)
org.jetbrains.security.package-checker (253.28294.335)
Kotlin: 253.28294.334-IJ

15

Hi Marco,

Thanks for sharing this example and the detailed environment specifications.

I tried to reproduce the issue using the enhanced switch snippet you provided, but I was unable to trigger the S1854 false positive on my side.

To help us investigate this further, could you please clarify a few points:

  • Type Resolution: Are the types used in your switch (e.g., DocumentStatus, SimpleStatusChangedEvent) fully resolved in your IDE?

  • Java Version: Could you confirm the specific Java language level configured for this project module?

  • Reproducer: If possible, could you provide a small sample project (e.g. a GitHub repository or a zip file) that demonstrates the issue? This would allow us to analyze the configuration and classpath context that triggers the false positive.

Thanks for your help!

Romain