remove non-null assertion operator from std (part1) (#3900)

std/datetime/mod.ts

@@ -1,8 +1,14 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { pad } from "../strings/pad.ts";
+import { assert } from "../testing/mod.ts";
 
 export type DateFormat = "mm-dd-yyyy" | "dd-mm-yyyy" | "yyyy-mm-dd";
 
+function execForce(reg: RegExp, pat: string): RegExpExecArray {
+  const v = reg.exec(pat);
+  assert(v != null);
+  return v;
+}
 /**
  * Parse date from string using format string
  * @param dateStr Date string
@@ -16,15 +22,15 @@ export function parseDate(dateStr: string, format: DateFormat): Date {
   switch (format) {
     case "mm-dd-yyyy":
       datePattern = /^(\d{2})-(\d{2})-(\d{4})$/;
-      [, m, d, y] = datePattern.exec(dateStr)!;
+      [, m, d, y] = execForce(datePattern, dateStr);
       break;
     case "dd-mm-yyyy":
       datePattern = /^(\d{2})-(\d{2})-(\d{4})$/;
-      [, d, m, y] = datePattern.exec(dateStr)!;
+      [, d, m, y] = execForce(datePattern, dateStr);
       break;
     case "yyyy-mm-dd":
       datePattern = /^(\d{4})-(\d{2})-(\d{2})$/;
-      [, y, m, d] = datePattern.exec(dateStr)!;
+      [, y, m, d] = execForce(datePattern, dateStr);
       break;
     default:
       throw new Error("Invalid date format!");
@@ -57,27 +63,27 @@ export function parseDateTime(
   switch (format) {
     case "mm-dd-yyyy hh:mm":
       datePattern = /^(\d{2})-(\d{2})-(\d{4}) (\d{2}):(\d{2})$/;
-      [, m, d, y, ho, mi] = datePattern.exec(datetimeStr)!;
+      [, m, d, y, ho, mi] = execForce(datePattern, datetimeStr);
       break;
     case "dd-mm-yyyy hh:mm":
       datePattern = /^(\d{2})-(\d{2})-(\d{4}) (\d{2}):(\d{2})$/;
-      [, d, m, y, ho, mi] = datePattern.exec(datetimeStr)!;
+      [, d, m, y, ho, mi] = execForce(datePattern, datetimeStr);
       break;
     case "yyyy-mm-dd hh:mm":
       datePattern = /^(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2})$/;
-      [, y, m, d, ho, mi] = datePattern.exec(datetimeStr)!;
+      [, y, m, d, ho, mi] = execForce(datePattern, datetimeStr);
       break;
     case "hh:mm mm-dd-yyyy":
       datePattern = /^(\d{2}):(\d{2}) (\d{2})-(\d{2})-(\d{4})$/;
-      [, ho, mi, m, d, y] = datePattern.exec(datetimeStr)!;
+      [, ho, mi, m, d, y] = execForce(datePattern, datetimeStr);
       break;
     case "hh:mm dd-mm-yyyy":
       datePattern = /^(\d{2}):(\d{2}) (\d{2})-(\d{2})-(\d{4})$/;
-      [, ho, mi, d, m, y] = datePattern.exec(datetimeStr)!;
+      [, ho, mi, d, m, y] = execForce(datePattern, datetimeStr);
       break;
     case "hh:mm yyyy-mm-dd":
       datePattern = /^(\d{2}):(\d{2}) (\d{4})-(\d{2})-(\d{2})$/;
-      [, ho, mi, y, m, d] = datePattern.exec(datetimeStr)!;
+      [, ho, mi, y, m, d] = execForce(datePattern, datetimeStr);
       break;
     default:
       throw new Error("Invalid datetime format!");

std/encoding/base32.ts

@@ -14,10 +14,10 @@ for (let i = 0, len = code.length; i < len; ++i) {
 const placeHolderPadLookup = [0, 1, , 2, 3, , 4];
 function _getPadLen(placeHoldersLen: number): number {
   const maybeLen = placeHolderPadLookup[placeHoldersLen];
-  if (maybeLen === undefined) {
+  if (typeof maybeLen !== "number") {
     throw new Error("Invalid pad length");
   }
-  return maybeLen!;
+  return maybeLen;
 }
 
 function getLens(b32: string): [number, number] {

std/examples/tests/xeval_test.ts

@@ -1,7 +1,11 @@
 import { xeval } from "../xeval.ts";
 import { stringsReader } from "../../io/util.ts";
 import { decode, encode } from "../../strings/mod.ts";
-import { assertEquals, assertStrContains } from "../../testing/asserts.ts";
+import {
+  assertEquals,
+  assertStrContains,
+  assert
+} from "../../testing/asserts.ts";
 import { test } from "../../testing/mod.ts";
 const { execPath, run } = Deno;
 
@@ -29,8 +33,9 @@ test(async function xevalCliReplvar(): Promise<void> {
     stdout: "piped",
     stderr: "null"
   });
-  await p.stdin!.write(encode("hello"));
+  assert(p.stdin != null);
-  await p.stdin!.close();
+  await p.stdin.write(encode("hello"));
+  await p.stdin.close();
   assertEquals(await p.status(), { code: 0, success: true });
   assertEquals(decode(await p.output()).trimEnd(), "hello");
 });

std/fs/expand_glob.ts

@@ -9,6 +9,7 @@ import {
   normalize
 } from "../path/mod.ts";
 import { WalkInfo, walk, walkSync } from "./walk.ts";
+import { assert } from "../testing/mod.ts";
 const { ErrorKind, cwd, stat, statSync } = Deno;
 type ErrorKind = Deno.ErrorKind;
 type DenoError = Deno.DenoError<ErrorKind>;
@@ -80,7 +81,9 @@ export async function* expandGlob(
 
   let fixedRoot = winRoot != undefined ? winRoot : "/";
   while (segments.length > 0 && !isGlob(segments[0])) {
-    fixedRoot = joinGlobs([fixedRoot, segments.shift()!], globOptions);
+    const seg = segments.shift();
+    assert(seg != null);
+    fixedRoot = joinGlobs([fixedRoot, seg], globOptions);
   }
 
   let fixedRootInfo: WalkInfo;
@@ -182,7 +185,9 @@ export function* expandGlobSync(
 
   let fixedRoot = winRoot != undefined ? winRoot : "/";
   while (segments.length > 0 && !isGlob(segments[0])) {
-    fixedRoot = joinGlobs([fixedRoot, segments.shift()!], globOptions);
+    const seg = segments.shift();
+    assert(seg != null);
+    fixedRoot = joinGlobs([fixedRoot, seg], globOptions);
   }
 
   let fixedRootInfo: WalkInfo;

std/fs/walk.ts

@@ -1,7 +1,7 @@
 // Documentation and interface for walk were adapted from Go
 // https://golang.org/pkg/path/filepath/#Walk
 // Copyright 2009 The Go Authors. All rights reserved. BSD license.
-import { unimplemented } from "../testing/asserts.ts";
+import { unimplemented, assert } from "../testing/asserts.ts";
 import { join } from "../path/mod.ts";
 const { readDir, readDirSync, stat, statSync } = Deno;
 type FileInfo = Deno.FileInfo;
@@ -90,7 +90,8 @@ export async function* walk(
       }
     }
 
-    const filename = join(root, info.name!);
+    assert(info.name != null);
+    const filename = join(root, info.name);
 
     if (info.isFile()) {
       if (includeFiles && include(filename, exts, match, skip)) {
@@ -142,7 +143,8 @@ export function* walkSync(
       }
     }
 
-    const filename = join(root, info.name!);
+    assert(info.name != null);
+    const filename = join(root, info.name);
 
     if (info.isFile()) {
       if (includeFiles && include(filename, exts, match, skip)) {

std/http/cookie.ts

@@ -45,8 +45,8 @@ function toString(cookie: Cookie): string {
   if (cookie.httpOnly) {
     out.push("HttpOnly");
   }
-  if (Number.isInteger(cookie.maxAge!)) {
+  if (Number.isInteger(cookie.maxAge)) {
-    assert(cookie.maxAge! > 0, "Max-Age must be an integer superior to 0");
+    assert(cookie.maxAge > 0, "Max-Age must be an integer superior to 0");
     out.push(`Max-Age=${cookie.maxAge}`);
   }
   if (cookie.domain) {
@@ -73,12 +73,14 @@ function toString(cookie: Cookie): string {
  * @param req Server Request
  */
 export function getCookies(req: ServerRequest): Cookies {
-  if (req.headers.has("Cookie")) {
+  const cookie = req.headers.get("Cookie");
+  if (cookie != null) {
     const out: Cookies = {};
-    const c = req.headers.get("Cookie")!.split(";");
+    const c = cookie.split(";");
     for (const kv of c) {
-      const cookieVal = kv.split("=");
+      const [cookieKey, ...cookieVal] = kv.split("=");
-      const key = cookieVal.shift()!.trim();
+      assert(cookieKey != null);
+      const key = cookieKey.trim();
       out[key] = cookieVal.join("=");
     }
     return out;

std/http/cookie_test.ts

@@ -38,7 +38,7 @@ test({
     const res: Response = {};
     delCookie(res, "deno");
     assertEquals(
-      res.headers!.get("Set-Cookie"),
+      res.headers?.get("Set-Cookie"),
       "deno=; Expires=Thu, 01 Jan 1970 00:00:00 GMT"
     );
   }

std/http/file_server.ts

@@ -66,7 +66,7 @@ function modeToString(isDir: boolean, maybeMode: number | null): string {
   if (maybeMode === null) {
     return "(unknown mode)";
   }
-  const mode = maybeMode!.toString(8);
+  const mode = maybeMode.toString(8);
   if (mode.length < 3) {
     return "(unknown mode)";
   }
@@ -186,8 +186,8 @@ function setCORS(res: Response): void {
   if (!res.headers) {
     res.headers = new Headers();
   }
-  res.headers!.append("access-control-allow-origin", "*");
+  res.headers.append("access-control-allow-origin", "*");
-  res.headers!.append(
+  res.headers.append(
     "access-control-allow-headers",
     "Origin, X-Requested-With, Content-Type, Accept, Range"
   );

std/http/file_server_test.ts

@@ -20,14 +20,15 @@ async function startFileServer(): Promise<void> {
     stdout: "piped"
   });
   // Once fileServer is ready it will write to its stdout.
-  const r = new TextProtoReader(new BufReader(fileServer.stdout!));
+  assert(fileServer.stdout != null);
+  const r = new TextProtoReader(new BufReader(fileServer.stdout));
   const s = await r.readLine();
   assert(s !== Deno.EOF && s.includes("server listening"));
 }
 
 function killFileServer(): void {
   fileServer.close();
-  fileServer.stdout!.close();
+  fileServer.stdout?.close();
 }
 
 test(async function serveFile(): Promise<void> {
@@ -102,8 +103,10 @@ test(async function servePermissionDenied(): Promise<void> {
     stdout: "piped",
     stderr: "piped"
   });
-  const reader = new TextProtoReader(new BufReader(deniedServer.stdout!));
+  assert(deniedServer.stdout != null);
-  const errReader = new TextProtoReader(new BufReader(deniedServer.stderr!));
+  const reader = new TextProtoReader(new BufReader(deniedServer.stdout));
+  assert(deniedServer.stderr != null);
+  const errReader = new TextProtoReader(new BufReader(deniedServer.stderr));
   const s = await reader.readLine();
   assert(s !== Deno.EOF && s.includes("server listening"));
 
@@ -115,8 +118,8 @@ test(async function servePermissionDenied(): Promise<void> {
     );
   } finally {
     deniedServer.close();
-    deniedServer.stdout!.close();
+    deniedServer.stdout.close();
-    deniedServer.stderr!.close();
+    deniedServer.stderr.close();
   }
 });
 
@@ -125,9 +128,10 @@ test(async function printHelp(): Promise<void> {
     args: [Deno.execPath(), "run", "http/file_server.ts", "--help"],
     stdout: "piped"
   });
-  const r = new TextProtoReader(new BufReader(helpProcess.stdout!));
+  assert(helpProcess.stdout != null);
+  const r = new TextProtoReader(new BufReader(helpProcess.stdout));
   const s = await r.readLine();
   assert(s !== Deno.EOF && s.includes("Deno File Server"));
   helpProcess.close();
-  helpProcess.stdout!.close();
+  helpProcess.stdout.close();
 });

std/http/racing_server_test.ts

@@ -12,13 +12,14 @@ async function startServer(): Promise<void> {
     stdout: "piped"
   });
   // Once racing server is ready it will write to its stdout.
-  const r = new TextProtoReader(new BufReader(server.stdout!));
+  assert(server.stdout != null);
+  const r = new TextProtoReader(new BufReader(server.stdout));
   const s = await r.readLine();
   assert(s !== Deno.EOF && s.includes("Racing server listening..."));
 }
 function killServer(): void {
   server.close();
-  server.stdout!.close();
+  server.stdout?.close();
 }
 
 const input = `GET / HTTP/1.1

std/http/server.ts

@@ -73,9 +73,10 @@ export async function writeResponse(w: Writer, r: Response): Promise<void> {
   let out = `HTTP/${protoMajor}.${protoMinor} ${statusCode} ${statusText}\r\n`;
 
   setContentLength(r);
-  const headers = r.headers!;
+  assert(r.headers != null);
+  const headers = r.headers;
 
-  for (const [key, value] of headers!) {
+  for (const [key, value] of headers) {
     out += `${key}: ${value}\r\n`;
   }
   out += "\r\n";
@@ -88,7 +89,9 @@ export async function writeResponse(w: Writer, r: Response): Promise<void> {
     const n = await writer.write(r.body);
     assert(n === r.body.byteLength);
   } else if (headers.has("content-length")) {
-    const bodyLength = parseInt(headers.get("content-length")!);
+    const contentLength = headers.get("content-length");
+    assert(contentLength != null);
+    const bodyLength = parseInt(contentLength);
     const n = await copy(writer, r.body);
     assert(n === bodyLength);
   } else {
@@ -129,8 +132,9 @@ export class ServerRequest {
     // undefined means not cached.
     // null means invalid or not provided.
     if (this._contentLength === undefined) {
-      if (this.headers.has("content-length")) {
+      const cl = this.headers.get("content-length");
-        this._contentLength = +this.headers.get("content-length")!;
+      if (cl) {
+        this._contentLength = parseInt(cl);
         // Convert NaN to null (as NaN harder to test)
         if (Number.isNaN(this._contentLength)) {
           this._contentLength = null;
@@ -190,12 +194,12 @@ export class ServerRequest {
       }
       yield nread;
     } else {
-      if (this.headers.has("transfer-encoding")) {
+      const transferEncoding = this.headers.get("transfer-encoding");
-        const transferEncodings = this.headers
+      if (transferEncoding) {
-          .get("transfer-encoding")!
+        const parts = transferEncoding
           .split(",")
           .map((e): string => e.trim().toLowerCase());
-        if (transferEncodings.includes("chunked")) {
+        if (parts.includes("chunked")) {
           // Based on https://tools.ietf.org/html/rfc2616#section-19.4.6
           const tp = new TextProtoReader(this.r);
           let line = await tp.readLine();
@@ -413,7 +417,7 @@ export class Server implements AsyncIterable<ServerRequest> {
 
       // Wait for the request to be processed before we accept a new request on
       // this connection.
-      const procError = await req!.done;
+      const procError = await req.done;
       if (procError) {
         // Something bad happened during response.
         // (likely other side closed during pipelined req)
@@ -422,12 +426,12 @@ export class Server implements AsyncIterable<ServerRequest> {
       }
     }
 
-    if (req! === Deno.EOF) {
+    if (req === Deno.EOF) {
       // The connection was gracefully closed.
-    } else if (err) {
+    } else if (err && req) {
       // An error was thrown while parsing request headers.
       try {
-        await writeResponse(req!.w, {
+        await writeResponse(req.w, {
           status: 400,
           body: encoder.encode(`${err.message}\r\n\r\n`)
         });

std/http/server_test.ts

@@ -506,8 +506,7 @@ test(async function testReadRequestError(): Promise<void> {
   for (const test of testCases) {
     const reader = new BufReader(new StringReader(test.in));
     let err;
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    let req: ServerRequest | Deno.EOF;
-    let req: any;
     try {
       req = await readRequest(mockConn as Deno.Conn, reader);
     } catch (e) {
@@ -520,10 +519,12 @@ test(async function testReadRequestError(): Promise<void> {
     } else if (test.err) {
       assert(err instanceof (test.err as typeof UnexpectedEOFError));
     } else {
+      assert(req instanceof ServerRequest);
+      assert(test.headers != null);
       assertEquals(err, undefined);
       assertNotEquals(req, Deno.EOF);
-      for (const h of test.headers!) {
+      for (const h of test.headers) {
-        assertEquals((req! as ServerRequest).headers.get(h.key), h.value);
+        assertEquals(req.headers.get(h.key), h.value);
       }
     }
   }

std/io/writers.ts

@@ -32,6 +32,6 @@ export class StringWriter implements Writer {
       offs += chunk.byteLength;
     }
     this.cache = decode(buf);
-    return this.cache!;
+    return this.cache;
   }
 }

std/log/mod.ts

@@ -6,6 +6,7 @@ import {
   WriterHandler,
   FileHandler
 } from "./handlers.ts";
+import { assert } from "../testing/mod.ts";
 
 export class LoggerConfig {
   level?: string;
@@ -50,16 +51,20 @@ export const handlers = {
 
 export function getLogger(name?: string): Logger {
   if (!name) {
-    return state.loggers.get("default")!;
+    const d = state.loggers.get("default");
+    assert(
+      d != null,
+      `"default" logger must be set for getting logger without name`
+    );
+    return d;
   }
-
+  const result = state.loggers.get(name);
-  if (!state.loggers.has(name)) {
+  if (!result) {
     const logger = new Logger("NOTSET", []);
     state.loggers.set(name, logger);
     return logger;
   }
-
+  return result;
-  return state.loggers.get(name)!;
 }
 
 export const debug = (msg: string, ...args: unknown[]): void =>
@@ -105,8 +110,9 @@ export async function setup(config: LogConfig): Promise<void> {
     const handlers: BaseHandler[] = [];
 
     handlerNames.forEach((handlerName): void => {
-      if (state.handlers.has(handlerName)) {
+      const handler = state.handlers.get(handlerName);
-        handlers.push(state.handlers.get(handlerName)!);
+      if (handler) {
+        handlers.push(handler);
       }
     });
 

std/media_types/mod.ts

@@ -56,8 +56,8 @@ function populateMaps(
     extensions.set(type, exts);
 
     for (const ext of exts) {
-      if (types.has(ext)) {
+      const current = types.get(ext);
-        const current = types.get(ext)!;
+      if (current) {
         const from = preference.indexOf(db[current].source);
         const to = preference.indexOf(mime.source);
 

std/mime/multipart.ts

@@ -12,7 +12,7 @@ import { extname } from "../path/mod.ts";
 import { tempFile } from "../io/util.ts";
 import { BufReader, BufWriter, UnexpectedEOFError } from "../io/bufio.ts";
 import { encoder } from "../strings/mod.ts";
-import { assertStrictEq } from "../testing/asserts.ts";
+import { assertStrictEq, assert } from "../testing/asserts.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
 import { hasOwnProperty } from "../util/has_own_property.ts";
 
@@ -205,7 +205,8 @@ class PartReader implements Reader, Closer {
     if (this.contentDispositionParams) return this.contentDispositionParams;
     const cd = this.headers.get("content-disposition");
     const params: { [key: string]: string } = {};
-    const comps = cd!.split(";");
+    assert(cd != null, "content-disposition must be set");
+    const comps = cd.split(";");
     this.contentDisposition = comps[0];
     comps
       .slice(1)
@@ -265,10 +266,12 @@ export class MultipartReader {
   /** Read all form data from stream.
    * If total size of stored data in memory exceed maxMemory,
    * overflowed file data will be written to temporal files.
-   * String field values are never written to files */
+   * String field values are never written to files.
+   * null value means parsing or writing to file was failed in some reason.
+   *  */
   async readForm(
     maxMemory: number
-  ): Promise<{ [key: string]: string | FormFile }> {
+  ): Promise<{ [key: string]: null | string | FormFile }> {
     const result = Object.create(null);
     let maxValueBytes = maxMemory + (10 << 20);
     const buf = new Buffer(new Uint8Array(maxValueBytes));
@@ -293,8 +296,10 @@ export class MultipartReader {
         continue;
       }
       // file
-      let formFile: FormFile;
+      let formFile: FormFile | null = null;
       const n = await copy(buf, p);
+      const contentType = p.headers.get("content-type");
+      assert(contentType != null, "content-type must be set");
       if (n > maxMemory) {
         // too big, write to disk and flush buffer
         const ext = extname(p.fileName);
@@ -311,7 +316,7 @@ export class MultipartReader {
           file.close();
           formFile = {
             filename: p.fileName,
-            type: p.headers.get("content-type")!,
+            type: contentType,
             tempfile: filepath,
             size
           };
@@ -321,14 +326,14 @@ export class MultipartReader {
       } else {
         formFile = {
           filename: p.fileName,
-          type: p.headers.get("content-type")!,
+          type: contentType,
           content: buf.bytes(),
           size: buf.length
         };
         maxMemory -= n;
         maxValueBytes -= n;
       }
-      result[p.formName] = formFile!;
+      result[p.formName] = formFile;
     }
     return result;
   }

std/mime/multipart_test.ts

@@ -199,7 +199,8 @@ test(async function multipartMultipartReader2(): Promise<void> {
     assertEquals(form["bar"], "bar");
     const file = form["file"] as FormFile;
     assertEquals(file.type, "application/octet-stream");
-    const f = await open(file.tempfile!);
+    assert(file.tempfile != null);
+    const f = await open(file.tempfile);
     const w = new StringWriter();
     await copy(w, f);
     const json = JSON.parse(w.toString());
@@ -207,7 +208,9 @@ test(async function multipartMultipartReader2(): Promise<void> {
     f.close();
   } finally {
     const file = form["file"] as FormFile;
-    await remove(file.tempfile!);
+    if (file.tempfile) {
+      await remove(file.tempfile);
+    }
   }
 });
 

std/path/glob.ts

@@ -1,6 +1,8 @@
 import { SEP, SEP_PATTERN } from "./constants.ts";
 import { globrex } from "./globrex.ts";
 import { join, normalize } from "./mod.ts";
+import { assert } from "../testing/asserts.ts";
+
 const { DenoError, ErrorKind } = Deno;
 
 export interface GlobOptions {
@@ -46,7 +48,8 @@ export function globToRegExp(
     strict: false,
     filepath: true
   });
-  return result.path!.regex;
+  assert(result.path != null);
+  return result.path.regex;
 }
 
 /** Test whether the given string is a glob */

std/path/utils.ts

@@ -49,7 +49,7 @@ export function normalizeString(
   let code: number;
   for (let i = 0, len = path.length; i <= len; ++i) {
     if (i < len) code = path.charCodeAt(i);
-    else if (isPathSeparator(code!)) break;
+    else if (isPathSeparator(code)) break;
     else code = CHAR_FORWARD_SLASH;
 
     if (isPathSeparator(code)) {

std/path/win32.ts

@@ -17,6 +17,7 @@ import {
   normalizeString,
   _format
 } from "./utils.ts";
+import { assert } from "../testing/asserts.ts";
 
 export const sep = "\\";
 export const delimiter = ";";
@@ -329,7 +330,7 @@ export function join(...paths: string[]): string {
   //   path.join('//server', 'share') -> '\\\\server\\share\\')
   let needsReplace = true;
   let slashCount = 0;
-  firstPart = firstPart!;
+  assert(firstPart != null);
   if (isPathSeparator(firstPart.charCodeAt(0))) {
     ++slashCount;
     const firstLen = firstPart.length;

std/testing/format.ts

@@ -1,3 +1,5 @@
+import { assert } from "./asserts.ts";
+
 // This file is ported from pretty-format@24.0.0
 /**
  * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
@@ -361,7 +363,9 @@ const getKeysOfEnumerableProperties = (object: {}): Array<string | symbol> => {
 
   if (Object.getOwnPropertySymbols) {
     Object.getOwnPropertySymbols(object).forEach((symbol): void => {
-      if (Object.getOwnPropertyDescriptor(object, symbol)!.enumerable) {
+      const d = Object.getOwnPropertyDescriptor(object, symbol);
+      assert(d != null);
+      if (d.enumerable) {
         keys.push(symbol);
       }
     });

std/testing/mod.ts

@@ -261,11 +261,14 @@ function printResults(
 }
 
 function previousPrinted(name: string, results: TestResults): boolean {
-  const curIndex: number = results.keys.get(name)!;
+  const curIndex = results.keys.get(name);
+  assert(curIndex != null);
   if (curIndex === 0) {
     return true;
   }
-  return results.cases.get(curIndex - 1)!.printed;
+  const prev = results.cases.get(curIndex - 1);
+  assert(prev != null);
+  return prev.printed;
 }
 
 async function createTestCase(
@@ -274,7 +277,10 @@ async function createTestCase(
   exitOnFail: boolean,
   { fn, name }: TestDefinition
 ): Promise<void> {
-  const result: TestResult = results.cases.get(results.keys.get(name)!)!;
+  const i = results.keys.get(name);
+  assert(i != null);
+  const result = results.cases.get(i);
+  assert(result != null);
   try {
     const start = performance.now();
     await fn();

std/textproto/mod.ts

@@ -7,7 +7,7 @@ import { BufReader, UnexpectedEOFError } from "../io/bufio.ts";
 import { charCode } from "../io/util.ts";
 
 const asciiDecoder = new TextDecoder();
-function str(buf: Uint8Array): string {
+function str(buf: Uint8Array | null | undefined): string {
   if (buf == null) {
     return "";
   } else {
@@ -82,7 +82,7 @@ export class TextProtoReader {
       throw new UnexpectedEOFError();
     } else if (buf[0] == charCode(" ") || buf[0] == charCode("\t")) {
       throw new ProtocolError(
-        `malformed MIME header initial line: ${str(line!)}`
+        `malformed MIME header initial line: ${str(line)}`
       );
     }
 
@@ -142,7 +142,7 @@ export class TextProtoReader {
       const { line: l, more } = r;
 
       // Avoid the copy if the first call produced a full line.
-      if (!line! && !more) {
+      if (!line && !more) {
         // TODO(ry):
         // This skipSpace() is definitely misplaced, but I don't know where it
         // comes from nor how to fix it.

std/util/async.ts

@@ -23,7 +23,7 @@ export function deferred<T>(): Deferred<T> {
   const promise = new Promise<T>((resolve, reject): void => {
     methods = { resolve, reject };
   });
-  return Object.assign(promise, methods)! as Deferred<T>;
+  return Object.assign(promise, methods) as Deferred<T>;
 }
 
 interface TaggedYieldedValue<T> {

std/util/deep_assign.ts

@@ -24,7 +24,7 @@ export function deepAssign(
       if (typeof target[key] !== `object` || !target[key]) {
         target[key] = {};
       }
-      deepAssign(target[key] as Record<string, unknown>, value!);
+      deepAssign(target[key] as Record<string, unknown>, value);
     });
   }
   return target;

std/ws/mod.ts

@@ -97,7 +97,7 @@ export interface WebSocket {
 export function unmask(payload: Uint8Array, mask?: Uint8Array): void {
   if (mask) {
     for (let i = 0, len = payload.length; i < len; i++) {
-      payload[i] ^= mask![i & 3];
+      payload[i] ^= mask[i & 3];
     }
   }
 }