1 files changed, 21 insertions, 0 deletions
diff --git a/ext/node/polyfills/_util/asserts.ts b/ext/node/polyfills/_util/asserts.ts
new file mode 100644
index 000000000..7760c8639
--- /dev/null
+++ b/ext/node/polyfills/_util/asserts.ts
@@ -0,0 +1,21 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+/** Assertion error class for node compat layer's internal code. */
+export class NodeCompatAssertionError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "NodeCompatAssertionError";
+  }
+}
+
+/** Make an assertion, if not `true`, then throw. */
+export function assert(expr: unknown, msg = ""): asserts expr {
+  if (!expr) {
+    throw new NodeCompatAssertionError(msg);
+  }
+}
+
+/** Use this to assert unreachable code. */
+export function unreachable(): never {
+  throw new NodeCompatAssertionError("unreachable");
+}