Rust: Fix common FPs for rust/unused-variable and rust/unused-value.

geoffw0 · geoffw0 · commit c160a1f6581c · 2025-12-10T16:56:24.000Z
diff --git a/rust/ql/src/queries/unusedentities/UnusedVariable.qll b/rust/ql/src/queries/unusedentities/UnusedVariable.qll
@@ -43,4 +43,8 @@ predicate isAllowableUnused(Variable v) {
   or
   // a 'self' variable
   v.getText() = "self"
+  or
+  // a common source of false positives is match arms that are misrecognized as
+  // a variable, having not been correctly resolved
+  v.getPat().getParentNode() instanceof MatchArm
 }

Original file line number	Diff line number	Diff line change
`@@ -43,4 +43,8 @@ predicate isAllowableUnused(Variable v) {`
`43`	`43`	`or`
`44`	`44`	`// a 'self' variable`
`45`	`45`	`v.getText() = "self"`
	`46`	`+ or`
	`47`	`+ // a common source of false positives is match arms that are misrecognized as`
	`48`	`+ // a variable, having not been correctly resolved`
	`49`	`+ v.getPat().getParentNode() instanceof MatchArm`
`46`	`50`	`}`