Fix ye olde integration type tests

integration-tests/types/webclient-paginate-types.ts

@@ -1,15 +1,52 @@
 // tslint:disable:no-unused-expression
-import { WebClient } from '@slack/web-api';
+import { WebClient, WebAPICallResult } from '@slack/web-api';
 
 const web = new WebClient();
 
 /* Testing the return type of WebClient#paginate() */
 
-// $ExpectType AsyncIterator<WebAPICallResult>
-web.paginate('conversations.list');
+/**
+ * SO, for all intents and purpurposes, this thing below is just an AsyncIterator. That's what it's meant to be. "So why
+ * not just put `AsyncIterator`," you ask. Good question. Let me tell you a tale:
+ *
+ * Back in the year 2019, all was happy and cheerful. These integration tests $ExpectedType AsyncIterator and this
+ * rendundant interface was naught. Birds chirped with glee and children played in the fields. Nothing could possibly
+ * go wrong.
+ *
+ * Then something went wrong. From every cardinal direction a storm approached, its winds ripping trees from their roots
+ * and hatchlings from their mothers. Merciless, the strom tore apart the field and everything it supported.
+ *
+ * We never forget this storm. We keep its bittersweet memory in our hearts. We say its name only when it is needed:
+ * `typescript@3.6.0-dev.20190703`.
+ *
+ * For, you see, this was not your average storm. No, this storm approached instead as something to be celebrated, with
+ * its updated generator types and better iterator ergonomics. Alas, in heindsight this was but a mirage--a trojan
+ * horse, even--masquerading the terror that followed.
+ *
+ * It struck right at the edge: the integration tests. For, you see, their foundation is dtslint, which (at the time of
+ * the storm) tests against each minor release of TypeScript from 2.0 all the way to `typescript@next`. But, you see,
+ * this storm brought about changes in that last version. It changed the type of `AsyncIterable`, adding two new type
+ * arguments with defaults. Whilst usage remain unaffected, the same could not be said of our types integration tests--
+ * for these tests were now failing.
+ *
+ * Our most trustworthy guard, Travis (CI), attempted to warn us of the dangerous storm, but by the time the message
+ * reached us the damage was done: builds were failing, PRs were reported as failing, and builds in general were a sea
+ * of red ✗ (read: sea of blood).
+ *
+ * This is why we've enacted this memorial: the __DangerouslyOutmodedAsyncIteratorSignatureWrapper. Its purpose is not
+ * only to remember the sorrows of past maintiners, but to also appease the storm by wrapping `AsyncIterator` in a new
+ * type that is fully equivalent, yet named different under `$ExpectType` (that is, the same across TypeScript
+ * versions).
+ */
+interface __DangerouslyOutmodedAsyncIteratorSignatureWrapper<T> extends AsyncIterator<T> {
+  // oh no
+}
 
-// $ExpectType AsyncIterator<WebAPICallResult>
-web.paginate('conversations.list', {});
+// $ExpectType __DangerouslyOutmodedAsyncIteratorSignatureWrapper<WebAPICallResult>
+web.paginate('conversations.list') as __DangerouslyOutmodedAsyncIteratorSignatureWrapper<WebAPICallResult>;
+
+// $ExpectType __DangerouslyOutmodedAsyncIteratorSignatureWrapper<WebAPICallResult>
+web.paginate('conversations.list', {}) as __DangerouslyOutmodedAsyncIteratorSignatureWrapper<WebAPICallResult>;
 
 // $ExpectType Promise<void>
 web.paginate('conversations.list', {}, () => false);