False positive for java 21 switch case with null, default

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#22,040 opened on Jun 24, 2026 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 3/5
Estimated time: 1-2 days
Newbie friendliness: 55/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Quiet
Tech stack: java
Domain: compilers

Research direction

Reproduce the CodeQL Java extraction failure with the minimal Java 21 switch example and the referenced PrintixService.java case. Start by tracing the Java extractor's parsing of switch labels involving null and default. Done means valid Java 21 source extracts successfully and finalization processes the Java code without the reported errors.

Written by the indexing model from the issue text.

Description

false-positive Stale

Version

CodeQL CLI: 2.25.6
github/codeql-action: v3
JDK: 21
OS: ubuntu-latest

What happened?

CodeQL Java extraction fails on valid Java 21 switch syntax.

Error:

Unable to parse source file: .../PrintixService.java
Parse error at line 84 column 23: Syntax error on token "default", invalid Expression

Then finalize fails with:

"CodeQL detected code written in Java/Kotlin but could not process any of it."
exit code 32

Minimal reproducible example

static String f(Object x) {
  return switch (x) {
    case null, default -> "v";
  };
}

Dominant language: CodeQL
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