flag less overly general functions with js/unneeded-defensive-code

Author: erik-krogh

javascript/ql/src/Expressions/UnneededDefensiveProgramming.ql

@@ -51,5 +51,8 @@ where
     or
     // too benign in practice
     e instanceof DefensiveExpressionTest::DefensiveInit
+    or
+    // functions might be written overly general
+    e.getALocalSource() instanceof DataFlow::ParameterNode
   )
 select e, "This guard always evaluates to " + cv + "."

javascript/ql/test/query-tests/Expressions/UnneededDefensiveProgramming/tst.js

@@ -176,4 +176,11 @@
 	u && (u.p, f()); // technically not OK, but it seems like an unlikely pattern
 	u && !u.p; // NOT OK
 	u && !u(); // NOT OK
+
+    
+    function hasCallbacks(success, error) {
+        if (success) success()
+        if (error) error()
+    }
+    hasCallbacks(() => {}, null);
 });