Rust: Correct + clarify qldoc.

Author: geoffw0

rust/ql/lib/codeql/rust/security/AccessInvalidPointerExtensions.qll

@@ -62,8 +62,8 @@ module AccessInvalidPointer {
   }
 
   /**
-   * A barrier for invalid pointer access vulnerabilities for values found to be `null` in
-   * a comparison.
+   * A barrier for invalid pointer access vulnerabilities for values checked to
+   * be non-`null`.
    */
-  private class NullCheckBarrier extends Barrier instanceof Barriers::NotNullCheckBarrier { }
+  private class NotNullCheckBarrier extends Barrier instanceof Barriers::NotNullCheckBarrier { }
 }

rust/ql/lib/codeql/rust/security/Barriers.qll

@@ -58,7 +58,7 @@ private predicate notNullCheck(CfgNodes::AstCfgNode g, Cfg::CfgNode node, boolea
 }
 
 /**
- * A node representing a check that the value is not null, which may be an
+ * A node representing a value checked to be non-null. This may be an
  * appropriate taint flow barrier for some queries.
  */
 class NotNullCheckBarrier extends DataFlow::Node {