chore: added a few more examples based on code review

test/language/expressions/optional-chaining/iteration-statement-for-await-of.js

@@ -8,6 +8,7 @@ info: |
   IterationStatement
     for await (LeftHandSideExpression of AssignmentExpression) Statement
 features: [optional-chaining]
+flags: [async]
 ---*/
 const obj = {
   iterable: {

test/language/expressions/optional-chaining/iteration-statement-for-of-type-error.js

@@ -11,8 +11,18 @@ features: [optional-chaining]
 ---*/
 
 assert.throws(TypeError, function() {
-  const obj = undefined;
-  for (const key of obj?.a) {
-    str += key;
-  }
+  for (const key of {}?.a) ;
+});
+
+assert.throws(TypeError, function() {
+  for (const key of {}?.a) {}
+});
+
+const obj = undefined;
+assert.throws(TypeError, function() {
+  for (const key of obj?.a) {}
+});
+
+assert.throws(TypeError, function() {
+  for (const key of obj?.a);
 });

test/language/expressions/optional-chaining/iteration-statement-for.js

@@ -16,12 +16,28 @@ const obj = {a: true};
 for (count = 0; obj?.a; count++) {
   if (count > 0) break;
 }
-assert.sameValue(1, count);
+assert.sameValue(count, 1);
 
 // OptionalExpression in init/test/update.
 let count2 = 0;
 const obj2 = undefined;
-for (obj?.a; obj2?.a; obj?.a) {
-  count2++;
+
+for (obj?.a; obj2?.a; obj?.a) { count2++; }
+assert.sameValue(count2, 0);
+
+for (obj?.a; undefined?.a; obj?.a) { count2++; }
+assert.sameValue(count2, 0);
+
+// Short-circuiting
+let touched = 0;
+const obj3 = {
+  get a() {
+    count++;
+    return undefined; // explicit for clarity
+  }
+};
+for (count = 0; true; obj3?.a?.[touched++]) {
+  if (count > 0) { break; }
 }
-assert.sameValue(0, count2);
+assert.sameValue(count, 1);
+assert.sameValue(touched, 0);