chore: Implement strict mode (denoland/deno_std#453)

Original: https://github.com/denoland/deno_std/commit/be24677d15494e83eea2e99bfc5ccfdde31cb892

2 files changed, 8 insertions, 9 deletions

diff --git a/io/bufio.ts b/io/bufio.ts
index 815c94eed..99b563816 100644
--- a/io/bufio.ts
+++ b/io/bufio.ts
@@ -40,8 +40,8 @@ export interface ReadLineResult {
 
 /** BufReader implements buffering for a Reader object. */
 export class BufReader implements Reader {
-  private buf: Uint8Array;
-  private rd: Reader; // Reader provided by caller.
+  private buf!: Uint8Array;
+  private rd!: Reader; // Reader provided by caller.
   private r = 0; // buf read position.
   private w = 0; // buf write position.
   private eof = false;
@@ -342,7 +342,7 @@ export class BufReader implements Reader {
       try {
         await this._fill();
       } catch (err) {
-        err.partial = slice;
+        err.partial = slice!;
         throw err;
       }
     }
@@ -439,7 +439,7 @@ export class BufWriter implements Writer {
     if (this.err !== null) throw this.err;
     if (this.n === 0) return;
 
-    let n: number;
+    let n = 0;
     try {
       n = await this.wr.write(this.buf.subarray(0, this.n));
     } catch (e) {
@@ -479,7 +479,7 @@ export class BufWriter implements Writer {
     if (p.length === 0) return 0;
 
     let nn = 0;
-    let n: number;
+    let n = 0;
     while (p.byteLength > this.available()) {
       if (this.buffered() === 0) {
         // Large write, empty buffer.
diff --git a/io/writers.ts b/io/writers.ts
index 869018728..de070d48a 100644
--- a/io/writers.ts
+++ b/io/writers.ts
@@ -6,6 +6,7 @@ import { decode, encode } from "../strings/mod.ts";
 export class StringWriter implements Writer {
   private chunks: Uint8Array[] = [];
   private byteLength: number = 0;
+  private cache: string | undefined;
 
   constructor(private base: string = "") {
     const c = encode(base);
@@ -16,12 +17,10 @@ export class StringWriter implements Writer {
   async write(p: Uint8Array): Promise<number> {
     this.chunks.push(p);
     this.byteLength += p.byteLength;
-    this.cache = null;
+    this.cache = undefined;
     return p.byteLength;
   }
 
-  private cache: string;
-
   toString(): string {
     if (this.cache) {
       return this.cache;
@@ -33,6 +32,6 @@ export class StringWriter implements Writer {
       offs += chunk.byteLength;
     }
     this.cache = decode(buf);
-    return this.cache;
+    return this.cache!;
   }
 }