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Java: Exclude unnamed variables from java/local-variable-is-never-read - #22994
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aschackmull merged 1 commit intoNov 3, 2026
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An unnamed variable (`_`, Java 22) cannot be read, so reporting it is always a false positive. Fixes github#22993. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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🟢 Approval recommended
No active review issues are identified for the targeted Java 22 unnamed-variable query update.
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What changed in this PR
Updates the Java local-variable-is-never-read query to ignore Java 22 unnamed variables, which cannot be read and should not produce alerts.
Changes:
- Excludes anonymous local variable declarations from query results.
- Adds Java 22 regression coverage for unnamed variables in patterns, enhanced
forloops, and local declarations. - Configures the test directory for Java 22 compilation.
- Documents the behavior change.
| File | Description |
|---|---|
java/ql/test/query-tests/UnreadLocal/UnreadLocal/UnnamedVariables.java |
Adds Java 22 regression cases for unnamed variables. |
java/ql/test/query-tests/UnreadLocal/options |
Enables Java 22 compilation for the test directory. |
java/ql/src/Violations of Best Practice/Dead Code/UnreadLocal.ql |
Excludes unnamed variables from query results. |
java/ql/src/change-notes/2026-11-03-unread-local-unnamed-variables.md |
Documents the query behavior change. |
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Review effort: Lite (auto)
aschackmull
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Nov 3, 2026
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LGTM, thanks for the contribution!
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Fixes #22993.
java/local-variable-is-never-readreports unnamed variables (_, Java 22), for examplecase Foo _ ->. An unnamed variable cannot be read, so every such alert is a false positive.The query now skips variables whose declaration
isAnonymous(). The source version already decides which variables that matches, so the query needs no version check of its own. Before Java 9,_is an ordinary identifier: the extractor keeps its name, and an unread_is still reported. Java 9 to 20 reject_as a name. From Java 22, or Java 21 with preview features,_declares an unnamed variable, which the extractor gives an empty name.UnnamedVariables.javacovers unnamed variables in switch type patterns, record patterns, an enhancedforloop, and a local declaration. The newoptionsfile compiles the test directory with--release 22, asprintAstandpattern-switch/cfgalready do. None of the new cases produce a result, so the three.expectedfiles in the directory are unchanged.Tested locally with CodeQL CLI 2.27.4. Without the query change,
UnreadLocal.qlreffails with five unexpected alerts, one per case inUnnamedVariables.java. With it, all three tests in the directory pass. A separate run with--release 8confirmed that an unreadint _ = 5;is still reported.🤖 Generated with Claude Code