highlights(hack): extend queries add tests

tests/query/highlights/xhp-intro.hack

@@ -0,0 +1,46 @@
+// From https://docs.hhvm.com/hack/XHP/introduction (MIT licensed)
+
+use namespace Facebook\XHP\Core as x;
+use type Facebook\XHP\HTML\{XHPHTMLHelpers, a, form};
+
+
+final xhp class a_post extends x\element {
+// ^ keyword
+//     ^ keyword
+//                        ^ keyword
+  use XHPHTMLHelpers;
+
+  attribute string href @required;
+  //                      ^ attribute
+  attribute string target;
+  // ^ keyword
+
+  <<__Override>>
+  protected async function renderAsync(): Awaitable<x\node> {
+    $id = $this->getID();
+
+    $anchor = <a>{$this->getChildren()}</a>;
+                                    // ^ tag.delimiter
+                                    // ^ tag
+    $form = (
+      <form
+        id={$id}
+        method="post"
+        action={$this->:href}
+        target={$this->:target}
+        class="postLink">
+        {$anchor}
+      </form>
+    );
+
+    $anchor->setAttribute(
+      'onclick',
+      'document.getElementById("'.$id.'").submit(); return false;',
+    );
+    $anchor->setAttribute('href', '#');
+    //        ^ method
+
+    return $form;
+  }
+}
+