refactor: remove unneeded ErrorKinds (#3936)

39 files changed, 408 insertions, 354 deletions

diff --git a/cli/js/buffer.ts b/cli/js/buffer.ts
index 2dec9fac6..dab5a4bfc 100644
--- a/cli/js/buffer.ts
+++ b/cli/js/buffer.ts
@@ -7,7 +7,6 @@
 import { Reader, Writer, EOF, SyncReader, SyncWriter } from "./io.ts";
 import { assert } from "./util.ts";
 import { TextDecoder } from "./text_encoding.ts";
-import { DenoError, ErrorKind } from "./errors.ts";
 
 // MIN_READ is the minimum ArrayBuffer size passed to a read call by
 // buffer.ReadFrom. As long as the Buffer has at least MIN_READ bytes beyond
@@ -162,7 +161,7 @@ export class Buffer implements Reader, SyncReader, Writer, SyncWriter {
 
   /** _grow() grows the buffer to guarantee space for n more bytes.
    * It returns the index where bytes should be written.
-   * If the buffer can't grow it will throw with ErrTooLarge.
+   * If the buffer can't grow it will throw with Error.
    */
   private _grow(n: number): number {
     const m = this.length;
@@ -183,10 +182,7 @@ export class Buffer implements Reader, SyncReader, Writer, SyncWriter {
       // don't spend all our time copying.
       copyBytes(this.buf, this.buf.subarray(this.off));
     } else if (c > MAX_SIZE - c - n) {
-      throw new DenoError(
-        ErrorKind.TooLarge,
-        "The buffer cannot be grown beyond the maximum size."
-      );
+      throw new Error("The buffer cannot be grown beyond the maximum size.");
     } else {
       // Not enough space anywhere, we need to allocate.
       const buf = new Uint8Array(2 * c + n);
@@ -202,7 +198,7 @@ export class Buffer implements Reader, SyncReader, Writer, SyncWriter {
   /** grow() grows the buffer's capacity, if necessary, to guarantee space for
    * another n bytes. After grow(n), at least n bytes can be written to the
    * buffer without another allocation. If n is negative, grow() will panic. If
-   * the buffer can't grow it will throw ErrTooLarge.
+   * the buffer can't grow it will throw Error.
    * Based on https://golang.org/pkg/bytes/#Buffer.Grow
    */
   grow(n: number): void {
@@ -215,7 +211,7 @@ export class Buffer implements Reader, SyncReader, Writer, SyncWriter {
 
   /** readFrom() reads data from r until EOF and appends it to the buffer,
    * growing the buffer as needed. It returns the number of bytes read. If the
-   * buffer becomes too large, readFrom will panic with ErrTooLarge.
+   * buffer becomes too large, readFrom will panic with Error.
    * Based on https://golang.org/pkg/bytes/#Buffer.ReadFrom
    */
   async readFrom(r: Reader): Promise<number> {
diff --git a/cli/js/buffer_test.ts b/cli/js/buffer_test.ts
index 72c0cab4b..769b46521 100644
--- a/cli/js/buffer_test.ts
+++ b/cli/js/buffer_test.ts
@@ -3,7 +3,7 @@
 // This code has been ported almost directly from Go's src/bytes/buffer_test.go
 // Copyright 2009 The Go Authors. All rights reserved. BSD license.
 // https://github.com/golang/go/blob/master/LICENSE
-import { assert, assertEquals, test } from "./test_util.ts";
+import { assertEquals, assert, assertStrContains, test } from "./test_util.ts";
 
 const { Buffer, readAll, readAllSync, writeAll, writeAllSync } = Deno;
 type Buffer = Deno.Buffer;
@@ -159,8 +159,8 @@ test(async function bufferTooLargeByteWrites(): Promise<void> {
     err = e;
   }
 
-  assertEquals(err.kind, Deno.ErrorKind.TooLarge);
-  assertEquals(err.name, "TooLarge");
+  assert(err instanceof Error);
+  assertStrContains(err.message, "grown beyond the maximum size");
 });
 
 test(async function bufferLargeByteReads(): Promise<void> {
diff --git a/cli/js/chmod_test.ts b/cli/js/chmod_test.ts
index b3b0a2ae2..24c69db7a 100644
--- a/cli/js/chmod_test.ts
+++ b/cli/js/chmod_test.ts
@@ -60,8 +60,7 @@ testPerm({ write: true }, function chmodSyncFailure(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: false }, function chmodSyncPerm(): void {
@@ -71,7 +70,7 @@ testPerm({ write: false }, function chmodSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -134,8 +133,7 @@ testPerm({ write: true }, async function chmodFailure(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: false }, async function chmodPerm(): Promise<void> {
@@ -145,6 +143,6 @@ testPerm({ write: false }, async function chmodPerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
diff --git a/cli/js/chown_test.ts b/cli/js/chown_test.ts
index 61132ae31..a1c12860d 100644
--- a/cli/js/chown_test.ts
+++ b/cli/js/chown_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { testPerm, assertEquals } from "./test_util.ts";
+import { testPerm, assertEquals, assert } from "./test_util.ts";
 
 // chown on Windows is noop for now, so ignore its testing on Windows
 if (Deno.build.os !== "win") {
@@ -31,8 +31,7 @@ if (Deno.build.os !== "win") {
     try {
       await Deno.chown(filePath, 1000, 1000);
     } catch (e) {
-      assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-      assertEquals(e.name, "PermissionDenied");
+      assert(e instanceof Deno.Err.PermissionDenied);
     }
   });
 
@@ -45,8 +44,7 @@ if (Deno.build.os !== "win") {
       try {
         Deno.chownSync(filePath, uid, gid);
       } catch (e) {
-        assertEquals(e.kind, Deno.ErrorKind.NotFound);
-        assertEquals(e.name, "NotFound");
+        assert(e instanceof Deno.Err.NotFound);
       }
     }
   );
@@ -60,8 +58,7 @@ if (Deno.build.os !== "win") {
       try {
         await Deno.chown(filePath, uid, gid);
       } catch (e) {
-        assertEquals(e.kind, Deno.ErrorKind.NotFound);
-        assertEquals(e.name, "NotFound");
+        assert(e instanceof Deno.Err.NotFound);
       }
     }
   );
@@ -77,8 +74,7 @@ if (Deno.build.os !== "win") {
       // try changing the file's owner to root
       Deno.chownSync(filePath, 0, 0);
     } catch (e) {
-      assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-      assertEquals(e.name, "PermissionDenied");
+      assert(e instanceof Deno.Err.PermissionDenied);
     }
     Deno.removeSync(dirPath, { recursive: true });
   });
@@ -96,8 +92,7 @@ if (Deno.build.os !== "win") {
       // try changing the file's owner to root
       await Deno.chown(filePath, 0, 0);
     } catch (e) {
-      assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-      assertEquals(e.name, "PermissionDenied");
+      assert(e instanceof Deno.Err.PermissionDenied);
     }
     await Deno.remove(dirPath, { recursive: true });
   });
diff --git a/cli/js/copy_file_test.ts b/cli/js/copy_file_test.ts
index 88dc3fdbf..567b246b7 100644
--- a/cli/js/copy_file_test.ts
+++ b/cli/js/copy_file_test.ts
@@ -43,8 +43,7 @@ testPerm({ write: true, read: true }, function copyFileSyncFailure(): void {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: true, read: false }, function copyFileSyncPerm1(): void {
@@ -53,8 +52,7 @@ testPerm({ write: true, read: false }, function copyFileSyncPerm1(): void {
     Deno.copyFileSync("/from.txt", "/to.txt");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -65,8 +63,7 @@ testPerm({ write: false, read: true }, function copyFileSyncPerm2(): void {
     Deno.copyFileSync("/from.txt", "/to.txt");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -113,8 +110,7 @@ testPerm({ read: true, write: true }, async function copyFileFailure(): Promise<
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm(
@@ -142,8 +138,7 @@ testPerm({ read: false, write: true }, async function copyFilePerm1(): Promise<
     await Deno.copyFile("/from.txt", "/to.txt");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -156,8 +151,7 @@ testPerm({ read: true, write: false }, async function copyFilePerm2(): Promise<
     await Deno.copyFile("/from.txt", "/to.txt");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
diff --git a/cli/js/deno.ts b/cli/js/deno.ts
index cdfedcd76..8ccca9096 100644
--- a/cli/js/deno.ts
+++ b/cli/js/deno.ts
@@ -22,7 +22,7 @@ export {
 } from "./diagnostics.ts";
 export { chdir, cwd } from "./dir.ts";
 export { applySourceMap } from "./error_stack.ts";
-export { ErrorKind, DenoError } from "./errors.ts";
+export { Err } from "./errors.ts";
 export { FileInfo } from "./file_info.ts";
 export {
   File,
diff --git a/cli/js/dir_test.ts b/cli/js/dir_test.ts
index 4b03eaedd..f936986aa 100644
--- a/cli/js/dir_test.ts
+++ b/cli/js/dir_test.ts
@@ -29,7 +29,7 @@ testPerm({ write: true }, function dirCwdError(): void {
       Deno.cwd();
       throw Error("current directory removed, should throw error");
     } catch (err) {
-      if (err instanceof Deno.DenoError) {
+      if (err instanceof Deno.Err.NotFound) {
         console.log(err.name === "NotFound");
       } else {
         throw Error("raised different exception");
@@ -45,7 +45,7 @@ testPerm({ write: true }, function dirChdirError(): void {
     Deno.chdir(path);
     throw Error("directory not available, should throw error");
   } catch (err) {
-    if (err instanceof Deno.DenoError) {
+    if (err instanceof Deno.Err.NotFound) {
       console.log(err.name === "NotFound");
     } else {
       throw Error("raised different exception");
diff --git a/cli/js/dispatch_json.ts b/cli/js/dispatch_json.ts
index adccb69c6..b0859e1ba 100644
--- a/cli/js/dispatch_json.ts
+++ b/cli/js/dispatch_json.ts
@@ -2,7 +2,7 @@
 import * as util from "./util.ts";
 import { TextEncoder, TextDecoder } from "./text_encoding.ts";
 import { core } from "./core.ts";
-import { ErrorKind, DenoError } from "./errors.ts";
+import { ErrorKind, constructError } from "./errors.ts";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 type Ok = any;
@@ -37,7 +37,7 @@ function encode(args: object): Uint8Array {
 
 function unwrapResponse(res: JsonResponse): Ok {
   if (res.err != null) {
-    throw new DenoError(res.err!.kind, res.err!.message);
+    return constructError(res.err!.kind, res.err!.message);
   }
   util.assert(res.ok != null);
   return res.ok;
diff --git a/cli/js/dispatch_json_test.ts b/cli/js/dispatch_json_test.ts
index c3fd6945b..90f93746e 100644
--- a/cli/js/dispatch_json_test.ts
+++ b/cli/js/dispatch_json_test.ts
@@ -2,7 +2,6 @@ import {
   test,
   testPerm,
   assert,
-  assertEquals,
   assertMatch,
   unreachable
 } from "./test_util.ts";
@@ -31,5 +30,4 @@ test(async function malformedJsonControlBuffer(): Promise<void> {
   const resJson = JSON.parse(resText) as any;
   assert(!resJson.ok);
   assert(resJson.err);
-  assertEquals(resJson.err!.kind, Deno.ErrorKind.InvalidInput);
 });
diff --git a/cli/js/dispatch_minimal.ts b/cli/js/dispatch_minimal.ts
index 1ce3fbaef..203701085 100644
--- a/cli/js/dispatch_minimal.ts
+++ b/cli/js/dispatch_minimal.ts
@@ -2,7 +2,7 @@
 import * as util from "./util.ts";
 import { core } from "./core.ts";
 import { TextDecoder } from "./text_encoding.ts";
-import { ErrorKind, DenoError } from "./errors.ts";
+import { Err, ErrorKind, constructError } from "./errors.ts";
 
 const promiseTableMin = new Map<number, util.Resolvable<RecordMinimal>>();
 // Note it's important that promiseId starts at 1 instead of 0, because sync
@@ -43,7 +43,7 @@ export function recordFromBufMinimal(ui8: Uint8Array): RecordMinimal {
     const message = decoder.decode(ui8.slice(12));
     err = { kind, message };
   } else if (ui8.length != 12) {
-    err = { kind: ErrorKind.InvalidData, message: "Bad message" };
+    throw new Err.InvalidData("BadMessage");
   }
 
   return {
@@ -56,7 +56,7 @@ export function recordFromBufMinimal(ui8: Uint8Array): RecordMinimal {
 
 function unwrapResponse(res: RecordMinimal): number {
   if (res.err != null) {
-    throw new DenoError(res.err!.kind, res.err!.message);
+    return constructError(res.err!.kind, res.err!.message);
   }
   return res.result;
 }
diff --git a/cli/js/dispatch_minimal_test.ts b/cli/js/dispatch_minimal_test.ts
index 12c70d375..75381204f 100644
--- a/cli/js/dispatch_minimal_test.ts
+++ b/cli/js/dispatch_minimal_test.ts
@@ -36,9 +36,7 @@ test(async function malformedMinimalControlBuffer(): Promise<void> {
     header.byteLength / 4
   );
   const arg = buf32[1];
-  const result = buf32[2];
   const message = new TextDecoder().decode(res.slice(12)).trim();
   assert(arg < 0);
-  assertEquals(result, Deno.ErrorKind.InvalidInput);
   assertEquals(message, "Unparsable control buffer");
 });
diff --git a/cli/js/errors.ts b/cli/js/errors.ts
index 0f75453ce..0844b0a56 100644
--- a/cli/js/errors.ts
+++ b/cli/js/errors.ts
@@ -1,27 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-/** A Deno specific error.  The `kind` property is set to a specific error code
- * which can be used to in application logic.
- *
- *       try {
- *         somethingThatMightThrow();
- *       } catch (e) {
- *         if (
- *           e instanceof Deno.DenoError &&
- *           e.kind === Deno.ErrorKind.NotFound
- *         ) {
- *           console.error("NotFound error!");
- *         }
- *       }
- *
- */
-export class DenoError<T extends ErrorKind> extends Error {
-  constructor(readonly kind: T, msg: string) {
-    super(msg);
-    this.name = ErrorKind[kind];
-  }
-}
-
 // Warning! The values in this enum are duplicated in cli/msg.rs
 // Update carefully!
 export enum ErrorKind {
@@ -35,22 +13,189 @@ export enum ErrorKind {
   AddrNotAvailable = 8,
   BrokenPipe = 9,
   AlreadyExists = 10,
-  WouldBlock = 11,
-  InvalidInput = 12,
   InvalidData = 13,
   TimedOut = 14,
   Interrupted = 15,
   WriteZero = 16,
-  Other = 17,
-  UnexpectedEof = 18,
-  BadResource = 19,
-  UrlParse = 20,
-  Http = 21,
-  TooLarge = 22,
-  InvalidSeekMode = 23,
-  UnixError = 24,
-  InvalidPath = 25,
-  ImportPrefixMissing = 26,
-  Diagnostic = 27,
-  JSError = 28
+  UnexpectedEof = 17,
+  BadResource = 18,
+  Http = 19,
+  URIError = 20,
+  TypeError = 21,
+  Other = 22
+}
+
+export function constructError(kind: ErrorKind, msg: string): never {
+  switch (kind) {
+    case ErrorKind.TypeError:
+      throw new TypeError(msg);
+    case ErrorKind.Other:
+      throw new Error(msg);
+    case ErrorKind.URIError:
+      throw new URIError(msg);
+    case ErrorKind.NotFound:
+      throw new NotFound(msg);
+    case ErrorKind.PermissionDenied:
+      throw new PermissionDenied(msg);
+    case ErrorKind.ConnectionRefused:
+      throw new ConnectionRefused(msg);
+    case ErrorKind.ConnectionReset:
+      throw new ConnectionReset(msg);
+    case ErrorKind.ConnectionAborted:
+      throw new ConnectionAborted(msg);
+    case ErrorKind.NotConnected:
+      throw new NotConnected(msg);
+    case ErrorKind.AddrInUse:
+      throw new AddrInUse(msg);
+    case ErrorKind.AddrNotAvailable:
+      throw new AddrNotAvailable(msg);
+    case ErrorKind.BrokenPipe:
+      throw new BrokenPipe(msg);
+    case ErrorKind.AlreadyExists:
+      throw new AlreadyExists(msg);
+    case ErrorKind.InvalidData:
+      throw new InvalidData(msg);
+    case ErrorKind.TimedOut:
+      throw new TimedOut(msg);
+    case ErrorKind.Interrupted:
+      throw new Interrupted(msg);
+    case ErrorKind.WriteZero:
+      throw new WriteZero(msg);
+    case ErrorKind.UnexpectedEof:
+      throw new UnexpectedEof(msg);
+    case ErrorKind.BadResource:
+      throw new BadResource(msg);
+    case ErrorKind.Http:
+      throw new Http(msg);
+  }
+}
+
+class NotFound extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "NotFound";
+  }
+}
+class PermissionDenied extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "PermissionDenied";
+  }
+}
+class ConnectionRefused extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "ConnectionRefused";
+  }
+}
+class ConnectionReset extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "ConnectionReset";
+  }
+}
+class ConnectionAborted extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "ConnectionAborted";
+  }
+}
+class NotConnected extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "NotConnected";
+  }
+}
+class AddrInUse extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "AddrInUse";
+  }
+}
+class AddrNotAvailable extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "AddrNotAvailable";
+  }
 }
+class BrokenPipe extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "BrokenPipe";
+  }
+}
+class AlreadyExists extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "AlreadyExists";
+  }
+}
+class InvalidData extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "InvalidData";
+  }
+}
+class TimedOut extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "TimedOut";
+  }
+}
+class Interrupted extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "Interrupted";
+  }
+}
+class WriteZero extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "WriteZero";
+  }
+}
+class Other extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "Other";
+  }
+}
+class UnexpectedEof extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "UnexpectedEof";
+  }
+}
+class BadResource extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "BadResource";
+  }
+}
+class Http extends Error {
+  constructor(msg: string) {
+    super(msg);
+    this.name = "Http";
+  }
+}
+
+export const Err = {
+  NotFound: NotFound,
+  PermissionDenied: PermissionDenied,
+  ConnectionRefused: ConnectionRefused,
+  ConnectionReset: ConnectionReset,
+  ConnectionAborted: ConnectionAborted,
+  NotConnected: NotConnected,
+  AddrInUse: AddrInUse,
+  AddrNotAvailable: AddrNotAvailable,
+  BrokenPipe: BrokenPipe,
+  AlreadyExists: AlreadyExists,
+  InvalidData: InvalidData,
+  TimedOut: TimedOut,
+  Interrupted: Interrupted,
+  WriteZero: WriteZero,
+  Other: Other,
+  UnexpectedEof: UnexpectedEof,
+  BadResource: BadResource,
+  Http: Http
+};
diff --git a/cli/js/event_target.ts b/cli/js/event_target.ts
index 495c8a042..daa73eb23 100644
--- a/cli/js/event_target.ts
+++ b/cli/js/event_target.ts
@@ -1,6 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import * as domTypes from "./dom_types.ts";
-import { DenoError, ErrorKind } from "./errors.ts";
 import { hasOwnProperty, requiredArguments } from "./util.ts";
 import {
   getRoot,
@@ -134,17 +133,15 @@ export class EventTarget implements domTypes.EventTarget {
     }
 
     if (event.dispatched || !event.initialized) {
-      throw new DenoError(
-        ErrorKind.InvalidData,
-        "Tried to dispatch an uninitialized event"
-      );
+      // TODO(bartlomieju): very likely that different error
+      // should be thrown here (DOMException?)
+      throw new TypeError("Tried to dispatch an uninitialized event");
     }
 
     if (event.eventPhase !== domTypes.EventPhase.NONE) {
-      throw new DenoError(
-        ErrorKind.InvalidData,
-        "Tried to dispatch a dispatching event"
-      );
+      // TODO(bartlomieju): very likely that different error
+      // should be thrown here (DOMException?)
+      throw new TypeError("Tried to dispatch a dispatching event");
     }
 
     return eventTargetHelpers.dispatch(this_, event);
@@ -418,7 +415,9 @@ const eventTargetHelpers = {
       try {
         listener.handleEvent(eventImpl);
       } catch (error) {
-        throw new DenoError(ErrorKind.Interrupted, error.message);
+        // TODO(bartlomieju): very likely that different error
+        // should be thrown here (DOMException?)
+        throw new Error(error.message);
       }
 
       eventImpl.inPassiveListener = false;
diff --git a/cli/js/fetch_test.ts b/cli/js/fetch_test.ts
index c63d05501..2912d5d2d 100644
--- a/cli/js/fetch_test.ts
+++ b/cli/js/fetch_test.ts
@@ -16,8 +16,7 @@ testPerm({ net: true }, async function fetchConnectionError(): Promise<void> {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.Http);
-  assertEquals(err.name, "Http");
+  assert(err instanceof Deno.Err.Http);
   assertStrContains(err.message, "error trying to connect");
 });
 
@@ -34,7 +33,7 @@ test(async function fetchPerm(): Promise<void> {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -107,8 +106,7 @@ testPerm({ net: true }, async function fetchEmptyInvalid(): Promise<void> {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.UrlParse);
-  assertEquals(err.name, "UrlParse");
+  assert(err instanceof URIError);
 });
 
 testPerm({ net: true }, async function fetchMultipartFormDataSuccess(): Promise<
diff --git a/cli/js/files_test.ts b/cli/js/files_test.ts
index 03e4d00e9..f71bfecc0 100644
--- a/cli/js/files_test.ts
+++ b/cli/js/files_test.ts
@@ -79,7 +79,7 @@ testPerm({ write: false }, async function writePermFailure(): Promise<void> {
       err = e;
     }
     assert(!!err);
-    assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+    assert(err instanceof Deno.Err.PermissionDenied);
     assertEquals(err.name, "PermissionDenied");
   }
 });
@@ -136,8 +136,7 @@ testPerm({ read: false }, async function readPermFailure(): Promise<void> {
     await Deno.open("cli/tests/fixture.json", "r");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -209,7 +208,7 @@ testPerm(
         err = e;
       }
       assert(!!err);
-      assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+      assert(err instanceof Deno.Err.PermissionDenied);
       assertEquals(err.name, "PermissionDenied");
     }
   }
@@ -380,8 +379,8 @@ testPerm({ read: true }, async function seekMode(): Promise<void> {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.InvalidSeekMode);
-  assertEquals(err.name, "InvalidSeekMode");
+  assert(err instanceof TypeError);
+  assertStrContains(err.message, "Invalid seek mode");
 
   // We should still be able to read the file
   // since it is still open.
diff --git a/cli/js/lib.deno.ns.d.ts b/cli/js/lib.deno.ns.d.ts
index b5a469f0b..fda2270a8 100644
--- a/cli/js/lib.deno.ns.d.ts
+++ b/cli/js/lib.deno.ns.d.ts
@@ -602,19 +602,19 @@ declare namespace Deno {
     write(p: Uint8Array): Promise<number>;
     /** _grow() grows the buffer to guarantee space for n more bytes.
      * It returns the index where bytes should be written.
-     * If the buffer can't grow it will throw with ErrTooLarge.
+     * If the buffer can't grow it will throw with Error.
      */
     private _grow;
     /** grow() grows the buffer's capacity, if necessary, to guarantee space for
      * another n bytes. After grow(n), at least n bytes can be written to the
      * buffer without another allocation. If n is negative, grow() will panic. If
-     * the buffer can't grow it will throw ErrTooLarge.
+     * the buffer can't grow it will throw Error.
      * Based on https://golang.org/pkg/bytes/#Buffer.Grow
      */
     grow(n: number): void;
     /** readFrom() reads data from r until EOF and appends it to the buffer,
      * growing the buffer as needed. It returns the number of bytes read. If the
-     * buffer becomes too large, readFrom will panic with ErrTooLarge.
+     * buffer becomes too large, readFrom will panic with Error.
      * Based on https://golang.org/pkg/bytes/#Buffer.ReadFrom
      */
     readFrom(r: Reader): Promise<number>;
@@ -1204,55 +1204,64 @@ declare namespace Deno {
    */
   export function applySourceMap(location: Location): Location;
 
-  /** A Deno specific error.  The `kind` property is set to a specific error code
-   * which can be used to in application logic.
-   *
-   *       try {
-   *         somethingThatMightThrow();
-   *       } catch (e) {
-   *         if (
-   *           e instanceof Deno.DenoError &&
-   *           e.kind === Deno.ErrorKind.NotFound
-   *         ) {
-   *           console.error("NotFound error!");
-   *         }
-   *       }
-   *
-   */
-  export class DenoError<T extends ErrorKind> extends Error {
-    readonly kind: T;
-    constructor(kind: T, msg: string);
-  }
-  export enum ErrorKind {
-    NotFound = 1,
-    PermissionDenied = 2,
-    ConnectionRefused = 3,
-    ConnectionReset = 4,
-    ConnectionAborted = 5,
-    NotConnected = 6,
-    AddrInUse = 7,
-    AddrNotAvailable = 8,
-    BrokenPipe = 9,
-    AlreadyExists = 10,
-    WouldBlock = 11,
-    InvalidInput = 12,
-    InvalidData = 13,
-    TimedOut = 14,
-    Interrupted = 15,
-    WriteZero = 16,
-    Other = 17,
-    UnexpectedEof = 18,
-    BadResource = 19,
-    UrlParse = 20,
-    Http = 21,
-    TooLarge = 22,
-    InvalidSeekMode = 23,
-    UnixError = 24,
-    InvalidPath = 25,
-    ImportPrefixMissing = 26,
-    Diagnostic = 27,
-    JSError = 28
+  /* eslint-disable @typescript-eslint/no-unused-vars */
+  namespace Err {
+    class NotFound extends Error {
+      constructor(msg: string);
+    }
+    class PermissionDenied extends Error {
+      constructor(msg: string);
+    }
+    class ConnectionRefused extends Error {
+      constructor(msg: string);
+    }
+    class ConnectionReset extends Error {
+      constructor(msg: string);
+    }
+    class ConnectionAborted extends Error {
+      constructor(msg: string);
+    }
+    class NotConnected extends Error {
+      constructor(msg: string);
+    }
+    class AddrInUse extends Error {
+      constructor(msg: string);
+    }
+    class AddrNotAvailable extends Error {
+      constructor(msg: string);
+    }
+    class BrokenPipe extends Error {
+      constructor(msg: string);
+    }
+    class AlreadyExists extends Error {
+      constructor(msg: string);
+    }
+    class InvalidData extends Error {
+      constructor(msg: string);
+    }
+    class TimedOut extends Error {
+      constructor(msg: string);
+    }
+    class Interrupted extends Error {
+      constructor(msg: string);
+    }
+    class WriteZero extends Error {
+      constructor(msg: string);
+    }
+    class Other extends Error {
+      constructor(msg: string);
+    }
+    class UnexpectedEof extends Error {
+      constructor(msg: string);
+    }
+    class BadResource extends Error {
+      constructor(msg: string);
+    }
+    class Http extends Error {
+      constructor(msg: string);
+    }
   }
+  /* eslint-enable @typescript-eslint/no-unused-vars */
 
   /** UNSTABLE: potentially want names to overlap more with browser.
    *
diff --git a/cli/js/link_test.ts b/cli/js/link_test.ts
index aada34b84..229207137 100644
--- a/cli/js/link_test.ts
+++ b/cli/js/link_test.ts
@@ -43,8 +43,7 @@ testPerm({ read: true, write: true }, function linkSyncExists(): void {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.AlreadyExists);
-  assertEquals(err.name, "AlreadyExists");
+  assert(err instanceof Deno.Err.AlreadyExists);
 });
 
 testPerm({ read: true, write: true }, function linkSyncNotFound(): void {
@@ -59,8 +58,7 @@ testPerm({ read: true, write: true }, function linkSyncNotFound(): void {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ read: false, write: true }, function linkSyncReadPerm(): void {
@@ -70,7 +68,7 @@ testPerm({ read: false, write: true }, function linkSyncReadPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -81,7 +79,7 @@ testPerm({ read: true, write: false }, function linkSyncWritePerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
diff --git a/cli/js/make_temp_test.ts b/cli/js/make_temp_test.ts
index f6bf59d32..06bfe0373 100644
--- a/cli/js/make_temp_test.ts
+++ b/cli/js/make_temp_test.ts
@@ -23,8 +23,7 @@ testPerm({ write: true }, function makeTempDirSyncSuccess(): void {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 test(function makeTempDirSyncPerm(): void {
@@ -35,7 +34,7 @@ test(function makeTempDirSyncPerm(): void {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -61,8 +60,7 @@ testPerm({ write: true }, async function makeTempDirSuccess(): Promise<void> {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: true }, function makeTempFileSyncSuccess(): void {
@@ -88,8 +86,7 @@ testPerm({ write: true }, function makeTempFileSyncSuccess(): void {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 test(function makeTempFileSyncPerm(): void {
@@ -100,7 +97,7 @@ test(function makeTempFileSyncPerm(): void {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -127,6 +124,5 @@ testPerm({ write: true }, async function makeTempFileSuccess(): Promise<void> {
   } catch (err_) {
     err = err_;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
diff --git a/cli/js/mkdir_test.ts b/cli/js/mkdir_test.ts
index dad61c1a4..856cbdeb5 100644
--- a/cli/js/mkdir_test.ts
+++ b/cli/js/mkdir_test.ts
@@ -25,7 +25,7 @@ testPerm({ write: false }, function mkdirSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -45,8 +45,7 @@ testPerm({ write: true }, function mkdirErrIfExists(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.AlreadyExists);
-  assertEquals(err.name, "AlreadyExists");
+  assert(err instanceof Deno.Err.AlreadyExists);
 });
 
 testPerm({ read: true, write: true }, function mkdirSyncRecursive(): void {
diff --git a/cli/js/net_test.ts b/cli/js/net_test.ts
index 68b1918b9..a2f086f0a 100644
--- a/cli/js/net_test.ts
+++ b/cli/js/net_test.ts
@@ -20,15 +20,14 @@ testPerm({ net: true }, async function netCloseWhileAccept(): Promise<void> {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.Other);
+  assert(err instanceof Error);
   assertEquals(err.message, "Listener has been closed");
 });
 
 testPerm({ net: true }, async function netConcurrentAccept(): Promise<void> {
   const listener = Deno.listen({ port: 4502 });
   let acceptErrCount = 0;
-  const checkErr = (e: Deno.DenoError<Deno.ErrorKind>): void => {
-    assertEquals(e.kind, Deno.ErrorKind.Other);
+  const checkErr = (e: Error): void => {
     if (e.message === "Listener has been closed") {
       assertEquals(acceptErrCount, 1);
     } else if (e.message === "Another accept task is ongoing") {
@@ -170,8 +169,7 @@ testPerm({ net: true }, async function netDoubleCloseRead() {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.NotConnected);
-  assertEquals(err.name, "NotConnected");
+  assert(err instanceof Deno.Err.NotConnected);
   closeDeferred.resolve();
   listener.close();
   conn.close();
@@ -205,8 +203,7 @@ testPerm({ net: true }, async function netCloseWriteSuccess() {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.BrokenPipe);
-  assertEquals(err.name, "BrokenPipe");
+  assert(err instanceof Deno.Err.BrokenPipe);
   closeDeferred.resolve();
   listener.close();
   conn.close();
@@ -232,8 +229,7 @@ testPerm({ net: true }, async function netDoubleCloseWrite() {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.kind, Deno.ErrorKind.NotConnected);
-  assertEquals(err.name, "NotConnected");
+  assert(err instanceof Deno.Err.NotConnected);
   closeDeferred.resolve();
   listener.close();
   conn.close();
diff --git a/cli/js/os.ts b/cli/js/os.ts
index 554d4f78d..275dbdf1d 100644
--- a/cli/js/os.ts
+++ b/cli/js/os.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import * as dispatch from "./dispatch.ts";
 import { sendSync } from "./dispatch_json.ts";
-import { ErrorKind } from "./errors.ts";
+import { Err } from "./errors.ts";
 import * as util from "./util.ts";
 
 /** Check if running in terminal.
@@ -193,7 +193,7 @@ export function dir(kind: DirKind): string | null {
   try {
     return sendSync(dispatch.OP_GET_DIR, { kind });
   } catch (error) {
-    if (error.kind == ErrorKind.PermissionDenied) {
+    if (error instanceof Err.PermissionDenied) {
       throw error;
     }
     return null;
diff --git a/cli/js/os_test.ts b/cli/js/os_test.ts
index a461ba63e..fa4bf636b 100644
--- a/cli/js/os_test.ts
+++ b/cli/js/os_test.ts
@@ -31,7 +31,7 @@ test(function envPermissionDenied1(): void {
     err = e;
   }
   assertNotEquals(err, undefined);
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -43,7 +43,7 @@ test(function envPermissionDenied2(): void {
     err = e;
   }
   assertNotEquals(err, undefined);
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -262,7 +262,7 @@ testPerm({ env: true }, function getDir(): void {
 testPerm({}, function getDirWithoutPermission(): void {
   assertThrows(
     () => Deno.dir("home"),
-    Deno.DenoError,
+    Deno.Err.PermissionDenied,
     `run again with the --allow-env flag`
   );
 });
@@ -277,7 +277,7 @@ testPerm({ env: false }, function execPathPerm(): void {
     Deno.execPath();
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+    assert(err instanceof Deno.Err.PermissionDenied);
     assertEquals(err.name, "PermissionDenied");
   }
   assert(caughtError);
@@ -293,7 +293,7 @@ testPerm({ env: false }, function hostnamePerm(): void {
     Deno.hostname();
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+    assert(err instanceof Deno.Err.PermissionDenied);
     assertEquals(err.name, "PermissionDenied");
   }
   assert(caughtError);
diff --git a/cli/js/permissions_test.ts b/cli/js/permissions_test.ts
index d63dddb15..6d79cfec0 100644
--- a/cli/js/permissions_test.ts
+++ b/cli/js/permissions_test.ts
@@ -31,18 +31,26 @@ for (const grant of knownPermissions) {
 }
 
 test(async function permissionInvalidName(): Promise<void> {
+  let thrown = false;
   try {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     await Deno.permissions.query({ name: "foo" as any });
   } catch (e) {
-    assert(e.name === "Other");
+    thrown = true;
+    assert(e instanceof Error);
+  } finally {
+    assert(thrown);
   }
 });
 
 test(async function permissionNetInvalidUrl(): Promise<void> {
+  let thrown = false;
   try {
     await Deno.permissions.query({ name: "net", url: ":" });
   } catch (e) {
-    assert(e.name === "UrlParse");
+    thrown = true;
+    assert(e instanceof URIError);
+  } finally {
+    assert(thrown);
   }
 });
diff --git a/cli/js/process_test.ts b/cli/js/process_test.ts
index dce4d9918..51ba8bfb3 100644
--- a/cli/js/process_test.ts
+++ b/cli/js/process_test.ts
@@ -6,16 +6,7 @@ import {
   assertEquals,
   assertStrContains
 } from "./test_util.ts";
-const {
-  kill,
-  run,
-  DenoError,
-  ErrorKind,
-  readFile,
-  open,
-  makeTempDir,
-  writeFile
-} = Deno;
+const { kill, run, readFile, open, makeTempDir, writeFile } = Deno;
 
 test(function runPermissions(): void {
   let caughtError = false;
@@ -23,8 +14,7 @@ test(function runPermissions(): void {
     Deno.run({ args: ["python", "-c", "print('hello world')"] });
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -78,8 +68,7 @@ testPerm({ run: true }, function runNotFound(): void {
     error = e;
   }
   assert(error !== undefined);
-  assert(error instanceof DenoError);
-  assertEquals(error.kind, ErrorKind.NotFound);
+  assert(error instanceof Deno.Err.NotFound);
 });
 
 testPerm(
@@ -332,8 +321,7 @@ if (Deno.build.os !== "win") {
       Deno.kill(Deno.pid, Deno.Signal.SIGCONT);
     } catch (e) {
       caughtError = true;
-      assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-      assertEquals(e.name, "PermissionDenied");
+      assert(e instanceof Deno.Err.PermissionDenied);
     }
     assert(caughtError);
   });
@@ -370,8 +358,7 @@ if (Deno.build.os !== "win") {
     }
 
     assert(!!err);
-    assertEquals(err.kind, Deno.ErrorKind.InvalidInput);
-    assertEquals(err.name, "InvalidInput");
+    assert(err instanceof TypeError);
 
     p.close();
   });
diff --git a/cli/js/read_dir_test.ts b/cli/js/read_dir_test.ts
index 77d2cbfe2..4496d7447 100644
--- a/cli/js/read_dir_test.ts
+++ b/cli/js/read_dir_test.ts
@@ -32,8 +32,7 @@ testPerm({ read: false }, function readDirSyncPerm(): void {
     Deno.readDirSync("tests/");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -46,7 +45,7 @@ testPerm({ read: true }, function readDirSyncNotDir(): void {
     src = Deno.readDirSync("cli/tests/fixture.json");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.Other);
+    assert(err instanceof Error);
   }
   assert(caughtError);
   assertEquals(src, undefined);
@@ -60,7 +59,7 @@ testPerm({ read: true }, function readDirSyncNotFound(): void {
     src = Deno.readDirSync("bad_dir_name");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
+    assert(err instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
   assertEquals(src, undefined);
@@ -77,8 +76,7 @@ testPerm({ read: false }, async function readDirPerm(): Promise<void> {
     await Deno.readDir("tests/");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
diff --git a/cli/js/read_file_test.ts b/cli/js/read_file_test.ts
index d40ea1b7b..726f08413 100644
--- a/cli/js/read_file_test.ts
+++ b/cli/js/read_file_test.ts
@@ -16,8 +16,7 @@ testPerm({ read: false }, function readFileSyncPerm(): void {
     Deno.readFileSync("cli/tests/fixture.json");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -29,7 +28,7 @@ testPerm({ read: true }, function readFileSyncNotFound(): void {
     data = Deno.readFileSync("bad_filename");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
   assert(data === undefined);
@@ -50,8 +49,7 @@ testPerm({ read: false }, async function readFilePerm(): Promise<void> {
     await Deno.readFile("cli/tests/fixture.json");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
diff --git a/cli/js/read_link_test.ts b/cli/js/read_link_test.ts
index c8db1cb58..6f028c08d 100644
--- a/cli/js/read_link_test.ts
+++ b/cli/js/read_link_test.ts
@@ -21,8 +21,7 @@ testPerm({ read: false }, async function readlinkSyncPerm(): Promise<void> {
     Deno.readlinkSync("/symlink");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -34,7 +33,7 @@ testPerm({ read: true }, function readlinkSyncNotFound(): void {
     data = Deno.readlinkSync("bad_filename");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
   assertEquals(data, undefined);
@@ -62,8 +61,7 @@ testPerm({ read: false }, async function readlinkPerm(): Promise<void> {
     await Deno.readlink("/symlink");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
diff --git a/cli/js/realpath_test.ts b/cli/js/realpath_test.ts
index 7443c7897..6dfec45fc 100644
--- a/cli/js/realpath_test.ts
+++ b/cli/js/realpath_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { testPerm, assert, assertEquals } from "./test_util.ts";
+import { testPerm, assert } from "./test_util.ts";
 
 testPerm({ read: true }, function realpathSyncSuccess(): void {
   const incompletePath = "cli/tests/fixture.json";
@@ -31,8 +31,7 @@ testPerm({ read: false }, function realpathSyncPerm(): void {
     Deno.realpathSync("some_file");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -43,7 +42,7 @@ testPerm({ read: true }, function realpathSyncNotFound(): void {
     Deno.realpathSync("bad_filename");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 });
@@ -81,8 +80,7 @@ testPerm({ read: false }, async function realpathPerm(): Promise<void> {
     await Deno.realpath("some_file");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -93,7 +91,7 @@ testPerm({ read: true }, async function realpathNotFound(): Promise<void> {
     await Deno.realpath("bad_filename");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 });
diff --git a/cli/js/remove_test.ts b/cli/js/remove_test.ts
index d686d1314..cb89ea1a9 100644
--- a/cli/js/remove_test.ts
+++ b/cli/js/remove_test.ts
@@ -18,8 +18,7 @@ testPerm({ write: true, read: true }, function removeSyncDirSuccess(): void {
     err = e;
   }
   // Directory is gone
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: true, read: true }, function removeSyncFileSuccess(): void {
@@ -39,8 +38,7 @@ testPerm({ write: true, read: true }, function removeSyncFileSuccess(): void {
     err = e;
   }
   // File is gone
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: true, read: true }, function removeSyncFail(): void {
@@ -61,8 +59,7 @@ testPerm({ write: true, read: true }, function removeSyncFail(): void {
     err = e;
   }
   // TODO(ry) Is Other really the error we should get here? What would Go do?
-  assertEquals(err.kind, Deno.ErrorKind.Other);
-  assertEquals(err.name, "Other");
+  assert(err instanceof Error);
   // NON-EXISTENT DIRECTORY/FILE
   try {
     // Non-existent
@@ -70,8 +67,7 @@ testPerm({ write: true, read: true }, function removeSyncFail(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm(
@@ -86,7 +82,6 @@ testPerm(
       errOnWindows = err;
     }
     if (Deno.build.os === "win") {
-      assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
       assertEquals(errOnWindows.message, "Not implemented");
     } else {
       const pathInfo = Deno.lstatSync(danglingSymlinkPath);
@@ -98,8 +93,7 @@ testPerm(
       } catch (e) {
         err = e;
       }
-      assertEquals(err.kind, Deno.ErrorKind.NotFound);
-      assertEquals(err.name, "NotFound");
+      assert(err instanceof Deno.Err.NotFound);
     }
   }
 );
@@ -121,7 +115,6 @@ testPerm(
       errOnWindows = err;
     }
     if (Deno.build.os === "win") {
-      assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
       assertEquals(errOnWindows.message, "Not implemented");
     } else {
       const symlinkPathInfo = Deno.statSync(validSymlinkPath);
@@ -134,8 +127,7 @@ testPerm(
         err = e;
       }
       Deno.removeSync(filePath);
-      assertEquals(err.kind, Deno.ErrorKind.NotFound);
-      assertEquals(err.name, "NotFound");
+      assert(err instanceof Deno.Err.NotFound);
     }
   }
 );
@@ -147,7 +139,7 @@ testPerm({ write: false }, function removeSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -166,8 +158,8 @@ testPerm({ write: true, read: true }, function removeAllSyncDirSuccess(): void {
     err = e;
   }
   // Directory is gone
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
+
   // REMOVE NON-EMPTY DIRECTORY
   path = Deno.makeTempDirSync() + "/dir/subdir";
   const subPath = path + "/subsubdir";
@@ -185,8 +177,7 @@ testPerm({ write: true, read: true }, function removeAllSyncDirSuccess(): void {
     err = e;
   }
   // Directory is gone
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm(
@@ -208,8 +199,7 @@ testPerm(
       err = e;
     }
     // File is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -222,8 +212,7 @@ testPerm({ write: true }, function removeAllSyncFail(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: false }, function removeAllSyncPerm(): void {
@@ -233,7 +222,7 @@ testPerm({ write: false }, function removeAllSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -256,8 +245,7 @@ testPerm(
       err = e;
     }
     // Directory is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -280,8 +268,7 @@ testPerm(
       err = e;
     }
     // File is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -304,8 +291,7 @@ testPerm({ write: true, read: true }, async function removeFail(): Promise<
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.Other);
-  assertEquals(err.name, "Other");
+  assert(err instanceof Error);
   // NON-EXISTENT DIRECTORY/FILE
   try {
     // Non-existent
@@ -313,8 +299,7 @@ testPerm({ write: true, read: true }, async function removeFail(): Promise<
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm(
@@ -329,7 +314,6 @@ testPerm(
       errOnWindows = e;
     }
     if (Deno.build.os === "win") {
-      assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
       assertEquals(errOnWindows.message, "Not implemented");
     } else {
       const pathInfo = Deno.lstatSync(danglingSymlinkPath);
@@ -341,8 +325,7 @@ testPerm(
       } catch (e) {
         err = e;
       }
-      assertEquals(err.kind, Deno.ErrorKind.NotFound);
-      assertEquals(err.name, "NotFound");
+      assert(err instanceof Deno.Err.NotFound);
     }
   }
 );
@@ -364,7 +347,6 @@ testPerm(
       errOnWindows = e;
     }
     if (Deno.build.os === "win") {
-      assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
       assertEquals(errOnWindows.message, "Not implemented");
     } else {
       const symlinkPathInfo = Deno.statSync(validSymlinkPath);
@@ -377,8 +359,7 @@ testPerm(
         err = e;
       }
       Deno.removeSync(filePath);
-      assertEquals(err.kind, Deno.ErrorKind.NotFound);
-      assertEquals(err.name, "NotFound");
+      assert(err instanceof Deno.Err.NotFound);
     }
   }
 );
@@ -390,7 +371,7 @@ testPerm({ write: false }, async function removePerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -411,8 +392,8 @@ testPerm(
       err = e;
     }
     // Directory is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
+
     // REMOVE NON-EMPTY DIRECTORY
     path = Deno.makeTempDirSync() + "/dir/subdir";
     const subPath = path + "/subsubdir";
@@ -430,8 +411,7 @@ testPerm(
       err = e;
     }
     // Directory is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -454,8 +434,7 @@ testPerm(
       err = e;
     }
     // File is gone
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -468,8 +447,7 @@ testPerm({ write: true }, async function removeAllFail(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.NotFound);
-  assertEquals(err.name, "NotFound");
+  assert(err instanceof Deno.Err.NotFound);
 });
 
 testPerm({ write: false }, async function removeAllPerm(): Promise<void> {
@@ -479,6 +457,6 @@ testPerm({ write: false }, async function removeAllPerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
diff --git a/cli/js/rename_test.ts b/cli/js/rename_test.ts
index 9c60e4d8c..3673d8489 100644
--- a/cli/js/rename_test.ts
+++ b/cli/js/rename_test.ts
@@ -17,7 +17,7 @@ testPerm({ read: true, write: true }, function renameSyncSuccess(): void {
     oldPathInfo = Deno.statSync(oldpath);
   } catch (e) {
     caughtErr = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtErr);
   assertEquals(oldPathInfo, undefined);
@@ -32,7 +32,7 @@ testPerm({ read: false, write: true }, function renameSyncReadPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -45,7 +45,7 @@ testPerm({ read: true, write: false }, function renameSyncWritePerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -67,7 +67,7 @@ testPerm({ read: true, write: true }, async function renameSuccess(): Promise<
     oldPathInfo = Deno.statSync(oldpath);
   } catch (e) {
     caughtErr = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtErr);
   assertEquals(oldPathInfo, undefined);
diff --git a/cli/js/stat_test.ts b/cli/js/stat_test.ts
index bce5449ac..3914f877c 100644
--- a/cli/js/stat_test.ts
+++ b/cli/js/stat_test.ts
@@ -23,8 +23,7 @@ testPerm({ read: false }, async function statSyncPerm(): Promise<void> {
     Deno.statSync("README.md");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -37,8 +36,7 @@ testPerm({ read: true }, async function statSyncNotFound(): Promise<void> {
     badInfo = Deno.statSync("bad_file_name");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 
   assert(caughtError);
@@ -65,8 +63,7 @@ testPerm({ read: false }, async function lstatSyncPerm(): Promise<void> {
     Deno.lstatSync("README.md");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -79,8 +76,7 @@ testPerm({ read: true }, async function lstatSyncNotFound(): Promise<void> {
     badInfo = Deno.lstatSync("bad_file_name");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 
   assert(caughtError);
@@ -107,8 +103,7 @@ testPerm({ read: false }, async function statPerm(): Promise<void> {
     await Deno.stat("README.md");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -121,8 +116,7 @@ testPerm({ read: true }, async function statNotFound(): Promise<void> {
     badInfo = await Deno.stat("bad_file_name");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 
   assert(caughtError);
@@ -149,8 +143,7 @@ testPerm({ read: false }, async function lstatPerm(): Promise<void> {
     await Deno.lstat("README.md");
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -163,8 +156,7 @@ testPerm({ read: true }, async function lstatNotFound(): Promise<void> {
     badInfo = await Deno.lstat("bad_file_name");
   } catch (err) {
     caughtError = true;
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 
   assert(caughtError);
diff --git a/cli/js/streams/pipe-to.ts b/cli/js/streams/pipe-to.ts
index 3764e605b..01608b955 100644
--- a/cli/js/streams/pipe-to.ts
+++ b/cli/js/streams/pipe-to.ts
@@ -19,7 +19,7 @@
 // import { ReadableStreamDefaultReader } from "./readable-stream-default-reader.ts";
 // import { WritableStreamDefaultWriter } from "./writable-stream-default-writer.ts";
 // import { PipeOptions } from "../dom_types.ts";
-// import { DenoError, ErrorKind } from "../errors.ts";
+// import { Err } from "../errors.ts";
 
 // // add a wrapper to handle falsy rejections
 // interface ErrorWrapper {
@@ -50,7 +50,7 @@
 //     abortAlgorithm = (): void => {
 //       // TODO this should be a DOMException,
 //       // https://github.com/stardazed/sd-streams/blob/master/packages/streams/src/pipe-to.ts#L38
-//       const error = new DenoError(ErrorKind.AbortError, "Aborted");
+//       const error = new Err.Aborted("Aborted");
 //       const actions: Array<() => Promise<void>> = [];
 //       if (preventAbort === false) {
 //         actions.push(() => {
diff --git a/cli/js/symlink_test.ts b/cli/js/symlink_test.ts
index b25c2e9c7..b89b718b3 100644
--- a/cli/js/symlink_test.ts
+++ b/cli/js/symlink_test.ts
@@ -15,7 +15,6 @@ testPerm({ read: true, write: true }, function symlinkSyncSuccess(): void {
   }
   if (errOnWindows) {
     assertEquals(Deno.build.os, "win");
-    assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
     assertEquals(errOnWindows.message, "Not implemented");
   } else {
     const newNameInfoLStat = Deno.lstatSync(newname);
@@ -32,7 +31,7 @@ test(function symlinkSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -69,7 +68,6 @@ testPerm({ read: true, write: true }, async function symlinkSuccess(): Promise<
     errOnWindows = e;
   }
   if (errOnWindows) {
-    assertEquals(errOnWindows.kind, Deno.ErrorKind.Other);
     assertEquals(errOnWindows.message, "Not implemented");
   } else {
     const newNameInfoLStat = Deno.lstatSync(newname);
diff --git a/cli/js/text_encoding.ts b/cli/js/text_encoding.ts
index ceb2f3fdc..0709e7123 100644
--- a/cli/js/text_encoding.ts
+++ b/cli/js/text_encoding.ts
@@ -27,7 +27,6 @@ import * as base64 from "./base64.ts";
 import { decodeUtf8 } from "./decode_utf8.ts";
 import * as domTypes from "./dom_types.ts";
 import { encodeUtf8 } from "./encode_utf8.ts";
-import { DenoError, ErrorKind } from "./errors.ts";
 
 const CONTINUE = null;
 const END_OF_STREAM = -1;
@@ -105,10 +104,7 @@ export function atob(s: string): string {
   const rem = s.length % 4;
   if (rem === 1 || /[^+/0-9A-Za-z]/.test(s)) {
     // TODO: throw `DOMException`
-    throw new DenoError(
-      ErrorKind.InvalidInput,
-      "The string to be decoded is not correctly encoded"
-    );
+    throw new TypeError("The string to be decoded is not correctly encoded");
   }
 
   // base64-js requires length exactly times of 4
@@ -130,8 +126,7 @@ export function btoa(s: string): string {
   for (let i = 0; i < s.length; i++) {
     const charCode = s[i].charCodeAt(0);
     if (charCode > 0xff) {
-      throw new DenoError(
-        ErrorKind.InvalidInput,
+      throw new TypeError(
         "The string to be encoded contains characters " +
           "outside of the Latin1 range."
       );
diff --git a/cli/js/text_encoding_test.ts b/cli/js/text_encoding_test.ts
index 2422f86f6..28f23511a 100644
--- a/cli/js/text_encoding_test.ts
+++ b/cli/js/text_encoding_test.ts
@@ -59,7 +59,7 @@ test(function btoaFailed(): void {
     err = e;
   }
   assert(!!err);
-  assertEquals(err.name, "InvalidInput");
+  assert(err instanceof TypeError);
 });
 
 test(function textDecoder2(): void {
diff --git a/cli/js/tls_test.ts b/cli/js/tls_test.ts
index ac59a2eb9..dabbb2c89 100644
--- a/cli/js/tls_test.ts
+++ b/cli/js/tls_test.ts
@@ -13,7 +13,7 @@ test(async function connectTLSNoPerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -28,7 +28,7 @@ test(async function connectTLSCertFileNoReadPerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -51,8 +51,7 @@ testPerm(
     } catch (e) {
       err = e;
     }
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
 
     try {
       Deno.listenTLS({
@@ -62,8 +61,7 @@ testPerm(
     } catch (e) {
       err = e;
     }
-    assertEquals(err.kind, Deno.ErrorKind.NotFound);
-    assertEquals(err.name, "NotFound");
+    assert(err instanceof Deno.Err.NotFound);
   }
 );
 
@@ -79,7 +77,7 @@ testPerm({ net: true }, async function listenTLSNoReadPerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -108,8 +106,7 @@ testPerm(
     } catch (e) {
       err = e;
     }
-    assertEquals(err.kind, Deno.ErrorKind.Other);
-    assertEquals(err.name, "Other");
+    assert(err instanceof Error);
   }
 );
 
@@ -138,8 +135,7 @@ testPerm(
     } catch (e) {
       err = e;
     }
-    assertEquals(err.kind, Deno.ErrorKind.Other);
-    assertEquals(err.name, "Other");
+    assert(err instanceof Error);
   }
 );
 
diff --git a/cli/js/truncate_test.ts b/cli/js/truncate_test.ts
index c8809df9e..42583354c 100644
--- a/cli/js/truncate_test.ts
+++ b/cli/js/truncate_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { testPerm, assertEquals } from "./test_util.ts";
+import { testPerm, assertEquals, assert } from "./test_util.ts";
 
 function readDataSync(name: string): string {
   const data = Deno.readFileSync(name);
@@ -58,7 +58,7 @@ testPerm({ write: false }, function truncateSyncPerm(): void {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
 
@@ -69,6 +69,6 @@ testPerm({ write: false }, async function truncatePerm(): Promise<void> {
   } catch (e) {
     err = e;
   }
-  assertEquals(err.kind, Deno.ErrorKind.PermissionDenied);
+  assert(err instanceof Deno.Err.PermissionDenied);
   assertEquals(err.name, "PermissionDenied");
 });
diff --git a/cli/js/utime_test.ts b/cli/js/utime_test.ts
index 72a4a6477..c7e4293bf 100644
--- a/cli/js/utime_test.ts
+++ b/cli/js/utime_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { testPerm, assert, assertEquals } from "./test_util.ts";
+import { testPerm, assert } from "./test_util.ts";
 
 // Allow 10 second difference.
 // Note this might not be enough for FAT (but we are not testing on such fs).
@@ -78,8 +78,7 @@ testPerm({ read: true, write: true }, function utimeSyncNotFound(): void {
     Deno.utimeSync("/baddir", atime, mtime);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
-    assertEquals(e.name, "NotFound");
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 });
@@ -93,8 +92,7 @@ testPerm({ read: true, write: false }, function utimeSyncPerm(): void {
     Deno.utimeSync("/some_dir", atime, mtime);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -159,8 +157,7 @@ testPerm({ read: true, write: true }, async function utimeNotFound(): Promise<
     await Deno.utime("/baddir", atime, mtime);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
-    assertEquals(e.name, "NotFound");
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 });
@@ -176,8 +173,7 @@ testPerm({ read: true, write: false }, async function utimeSyncPerm(): Promise<
     await Deno.utime("/some_dir", atime, mtime);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
diff --git a/cli/js/write_file_test.ts b/cli/js/write_file_test.ts
index 2b952655f..9f58f4460 100644
--- a/cli/js/write_file_test.ts
+++ b/cli/js/write_file_test.ts
@@ -22,8 +22,7 @@ testPerm({ write: true }, function writeFileSyncFail(): void {
     Deno.writeFileSync(filename, data);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
-    assertEquals(e.name, "NotFound");
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 });
@@ -38,8 +37,7 @@ testPerm({ write: false }, function writeFileSyncPerm(): void {
     Deno.writeFileSync(filename, data);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -66,8 +64,7 @@ testPerm({ read: true, write: true }, function writeFileSyncCreate(): void {
     Deno.writeFileSync(filename, data, { create: false });
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
-    assertEquals(e.name, "NotFound");
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);
 
@@ -128,8 +125,7 @@ testPerm(
       await Deno.writeFile(filename, data);
     } catch (e) {
       caughtError = true;
-      assertEquals(e.kind, Deno.ErrorKind.NotFound);
-      assertEquals(e.name, "NotFound");
+      assert(e instanceof Deno.Err.NotFound);
     }
     assert(caughtError);
   }
@@ -147,8 +143,7 @@ testPerm({ read: true, write: false }, async function writeFilePerm(): Promise<
     await Deno.writeFile(filename, data);
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.PermissionDenied);
-    assertEquals(e.name, "PermissionDenied");
+    assert(e instanceof Deno.Err.PermissionDenied);
   }
   assert(caughtError);
 });
@@ -180,8 +175,7 @@ testPerm({ read: true, write: true }, async function writeFileCreate(): Promise<
     await Deno.writeFile(filename, data, { create: false });
   } catch (e) {
     caughtError = true;
-    assertEquals(e.kind, Deno.ErrorKind.NotFound);
-    assertEquals(e.name, "NotFound");
+    assert(e instanceof Deno.Err.NotFound);
   }
   assert(caughtError);