2023-09-13T09:17:13.105Z

src/080-configuring-typescript/191-no-unchecked-indexed-access.problem/helpers.d.ts

@@ -0,0 +1,17 @@
+type Expect<T extends true> = T;
+type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y
+  ? 1
+  : 2
+  ? true
+  : false;
+
+/**
+ * Checks that Y is assignable to X.
+ *
+ * For instance, `Extends<string, 'a'>` is true. This is because
+ * 'a' can be passed to a function which expects a string.
+ *
+ * But `Extends<'a', string>` is false. This is because a string
+ * CANNOT be passed to a function which expects 'a'.
+ */
+type Extends<X, Y> = Y extends X ? true : false;

src/080-configuring-typescript/191-no-unchecked-indexed-access.problem/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "exercise",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "dev": "tsc --watch"
+  }
+}

src/080-configuring-typescript/191-no-unchecked-indexed-access.problem/src/index.ts

@@ -0,0 +1,5 @@
+const array = [1, 2, 3];
+
+const mightNotExist = array[3];
+
+type test = Expect<Equal<typeof mightNotExist, number | undefined>>;

src/080-configuring-typescript/191-no-unchecked-indexed-access.problem/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "esModuleInterop": true,
+    "noEmit": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "isolatedModules": true,
+  },
+}

src/080-configuring-typescript/191-no-unchecked-indexed-access.solution/helpers.d.ts

@@ -0,0 +1,17 @@
+type Expect<T extends true> = T;
+type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y
+  ? 1
+  : 2
+  ? true
+  : false;
+
+/**
+ * Checks that Y is assignable to X.
+ *
+ * For instance, `Extends<string, 'a'>` is true. This is because
+ * 'a' can be passed to a function which expects a string.
+ *
+ * But `Extends<'a', string>` is false. This is because a string
+ * CANNOT be passed to a function which expects 'a'.
+ */
+type Extends<X, Y> = Y extends X ? true : false;

src/080-configuring-typescript/191-no-unchecked-indexed-access.solution/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "exercise",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "dev": "tsc --watch"
+  }
+}

src/080-configuring-typescript/191-no-unchecked-indexed-access.solution/src/index.ts

@@ -0,0 +1,5 @@
+const array = [1, 2, 3];
+
+const mightNotExist = array[3];
+
+type test = Expect<Equal<typeof mightNotExist, number | undefined>>;

src/080-configuring-typescript/191-no-unchecked-indexed-access.solution/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "esModuleInterop": true,
+    "noEmit": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "isolatedModules": true,
+    "noUncheckedIndexedAccess": true
+  },
+}

src/080-configuring-typescript/192-tsconfig-bases.explainer.ts

@@ -1 +1,3 @@
 // https://github.com/tsconfig/bases
+
+// Note that strictest is not what I recommend