5 files changed, 69 insertions, 29 deletions

diff --git a/cli/dts/lib.deno.shared_globals.d.ts b/cli/dts/lib.deno.shared_globals.d.ts
index 6b6a1bf85..03b85f50d 100644
--- a/cli/dts/lib.deno.shared_globals.d.ts
+++ b/cli/dts/lib.deno.shared_globals.d.ts
@@ -606,15 +606,20 @@ declare class URL {
   toJSON(): string;
 }
 
-interface MessageEventInit extends EventInit {
-  data?: any;
+interface MessageEventInit<T = any> extends EventInit {
+  data?: T;
   origin?: string;
   lastEventId?: string;
 }
 
-declare class MessageEvent extends Event {
-  readonly data: any;
-  readonly origin: string;
+declare class MessageEvent<T = any> extends Event {
+  /**
+   * Returns the data of the message.
+   */
+  readonly data: T;
+  /**
+   * Returns the last event ID string, for server-sent events.
+   */
   readonly lastEventId: string;
   constructor(type: string, eventInitDict?: MessageEventInit);
 }
diff --git a/cli/dts/lib.deno.worker.d.ts b/cli/dts/lib.deno.worker.d.ts
index 9f8845f4a..3fc95a97e 100644
--- a/cli/dts/lib.deno.worker.d.ts
+++ b/cli/dts/lib.deno.worker.d.ts
@@ -9,35 +9,51 @@
 
 declare interface DedicatedWorkerGlobalScope {
   self: DedicatedWorkerGlobalScope & typeof globalThis;
-  onmessage: (e: MessageEvent) => void;
-  onmessageerror: (e: MessageEvent) => void;
-  onerror: undefined | typeof onerror;
-  name: typeof __workerMain.name;
-  close: typeof __workerMain.close;
-  postMessage: typeof __workerMain.postMessage;
+  onmessage:
+    | ((
+      this: DedicatedWorkerGlobalScope & typeof globalThis,
+      ev: MessageEvent,
+    ) => any)
+    | null;
+  onmessageerror:
+    | ((
+      this: DedicatedWorkerGlobalScope & typeof globalThis,
+      ev: MessageEvent,
+    ) => any)
+    | null;
+  onerror:
+    | ((
+      this: DedicatedWorkerGlobalScope & typeof globalThis,
+      ev: ErrorEvent,
+    ) => any)
+    | null;
+  name: string;
+  close: () => void;
+  postMessage: (message: any) => void;
   Deno: typeof Deno;
 }
 
 declare var self: DedicatedWorkerGlobalScope & typeof globalThis;
-declare var onmessage: ((e: { data: any }) => Promise<void> | void) | undefined;
+declare var onmessage:
+  | ((
+    this: DedicatedWorkerGlobalScope & typeof globalThis,
+    ev: MessageEvent,
+  ) => any)
+  | null;
+declare var onmessageerror:
+  | ((
+    this: DedicatedWorkerGlobalScope & typeof globalThis,
+    ev: MessageEvent,
+  ) => any)
+  | null;
 declare var onerror:
   | ((
-    msg: string,
-    source: string,
-    lineno: number,
-    colno: number,
-    e: Event,
-  ) => boolean | void)
-  | undefined;
-declare var close: typeof __workerMain.close;
-declare var name: typeof __workerMain.name;
-declare var postMessage: typeof __workerMain.postMessage;
-
-declare namespace __workerMain {
-  export let onmessage: (e: { data: any }) => void;
-  export function postMessage(data: any): void;
-  export function close(): void;
-  export const name: string;
-}
+    this: DedicatedWorkerGlobalScope & typeof globalThis,
+    ev: ErrorEvent,
+  ) => any)
+  | null;
+declare var close: () => void;
+declare var name: string;
+declare var postMessage: (message: any) => void;
 
 /* eslint-enable @typescript-eslint/no-unused-vars, @typescript-eslint/no-explicit-any */
diff --git a/cli/tests/subdir/worker_types.ts b/cli/tests/subdir/worker_types.ts
new file mode 100644
index 000000000..7a651e35a
--- /dev/null
+++ b/cli/tests/subdir/worker_types.ts
@@ -0,0 +1,4 @@
+// eslint-disable-next-line require-await
+self.onmessage = async (_msg: MessageEvent) => {
+  self.postMessage("hello");
+};
diff --git a/cli/tests/unit/unit_tests.ts b/cli/tests/unit/unit_tests.ts
index e97c485a8..f545e55fa 100644
--- a/cli/tests/unit/unit_tests.ts
+++ b/cli/tests/unit/unit_tests.ts
@@ -74,6 +74,7 @@ import "./umask_test.ts";
 import "./url_test.ts";
 import "./url_search_params_test.ts";
 import "./utime_test.ts";
+import "./worker_types.ts";
 import "./write_file_test.ts";
 import "./write_text_file_test.ts";
 import "./performance_test.ts";
diff --git a/cli/tests/unit/worker_types.ts b/cli/tests/unit/worker_types.ts
new file mode 100644
index 000000000..e8bc7eb78
--- /dev/null
+++ b/cli/tests/unit/worker_types.ts
@@ -0,0 +1,14 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { assert, unitTest } from "./test_util.ts";
+
+unitTest(
+  { perms: { read: true } },
+  function utimeSyncFileSuccess() {
+    const w = new Worker(
+      new URL("../subdir/worker_types.ts", import.meta.url).href,
+      { type: "module" },
+    );
+    assert(w);
+    w.terminate();
+  },
+);