JavaScript: Fix false positive on Flow type annotations in ExprHasNoEffect

Author: Napalys

javascript/ql/lib/Expressions/ExprHasNoEffect.qll

@@ -174,7 +174,10 @@ predicate hasNoEffect(Expr e) {
     not exists(fe.getName())
   ) and
   // exclude block-level flow type annotations. For example: `(name: empty)`.
-  not e.(ParExpr).getExpression().getLastToken().getNextToken().getValue() = ":" and
+  not exists(ParExpr parent |
+    e.getParent() = parent and
+    e.getLastToken().getNextToken().getValue() = ":"
+  ) and
   // exclude the first statement of a try block
   not e = any(TryStmt stmt).getBody().getStmt(0).(ExprStmt).getExpr() and
   // exclude expressions that are alone in a file, and file doesn't contain a function.

javascript/ql/test/query-tests/Expressions/ExprHasNoEffect/ExprHasNoEffect.expected

@@ -11,6 +11,5 @@
 | tst.js:49:3:49:49 | new Syn ... o me?") | This expression has no effect. |
 | tst.js:50:3:50:36 | new Err ... age(e)) | This expression has no effect. |
 | tst.js:61:2:61:20 | o.trivialNonGetter1 | This expression has no effect. |
-| tst.js:75:3:75:3 | o | This expression has no effect. |
 | tst.js:77:24:77:24 | o | This expression has no effect. |
 | uselessfn.js:1:2:1:26 | functio ... d.");\\n} | This expression has no effect. |

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

@@ -72,7 +72,7 @@ function g() {
 	Object.defineProperty(o, "nonTrivialGetter2", unknownGetterDef());
 	o.nonTrivialGetter2;
 
-	(o: empty); // $SPURIOUS:Alert
+	(o: empty);
 
 	testSomeCondition() ? o : // $ Alert
 		doSomethingDangerous();