👍 Add isUnknown predicate function

is.ts

@@ -18,6 +18,13 @@ export function isAny(_x: unknown): _x is any {
   return true;
 }
 
+/**
+ * Always return `true` regardless of the type of `x`.
+ */
+export function isUnknown(_x: unknown): _x is unknown {
+  return true;
+}
+
 /**
  * Return `true` if the type of `x` is `string`.
  */
@@ -508,6 +515,7 @@ export function isOptionalOf<T>(
 
 export default {
   Any: isAny,
+  Unknown: isUnknown,
   String: isString,
   Number: isNumber,
   BigInt: isBigInt,

is_test.ts

@@ -36,6 +36,7 @@ import is, {
   isTupleOf,
   isUndefined,
   isUniformTupleOf,
+  isUnknown,
   Predicate,
   PredicateType,
 } from "./is.ts";
@@ -135,6 +136,26 @@ Deno.test("isAny", async (t) => {
   });
 });
 
+Deno.test("isUnknown", async (t) => {
+  await testWithExamples(t, isUnknown, {
+    validExamples: [
+      "string",
+      "number",
+      "bigint",
+      "boolean",
+      "array",
+      "record",
+      "syncFunction",
+      "asyncFunction",
+      "null",
+      "undefined",
+      "symbol",
+      "date",
+      "promise",
+    ],
+  });
+});
+
 Deno.test("isString", async (t) => {
   await testWithExamples(t, isString, { validExamples: ["string"] });
 });