feat: add unknown export

infer.types.ts

@@ -738,3 +738,13 @@ let _pa3 = t.partial(
 	// @ts-expect-error wrong type
 	t.string(),
 );
+
+// ---
+// UNKNOWN
+// ---
+
+let u1 = t.unknown();
+declare let U1: t.Infer<typeof u1>;
+assert<unknown>(U1);
+
+assert<unknown>(123);

mod.test.ts

@@ -41,6 +41,42 @@ describe('Null', () => {
 	});
 });
 
+describe('Unknown', () => {
+	it('should be a function', () => {
+		assert(typeof t.unknown === 'function');
+	});
+
+	// https://json-schema.org/understanding-json-schema/reference/null
+	it('should be JSON schema', () => {
+		assertEquals(t.unknown(), {
+			// empty
+		});
+	});
+
+	it('should allow annotations', () => {
+		let output = t.unknown({
+			deprecated: true,
+			description: 'foobar',
+		});
+
+		assertEquals(output, {
+			deprecated: true,
+			description: 'foobar',
+		});
+	});
+
+	it('should force "type" property', () => {
+		let output = t.null({
+			// @ts-expect-error; not in options definition
+			type: 'other',
+		});
+
+		assertEquals(output, {
+			type: 'null',
+		});
+	});
+});
+
 describe('Constant', () => {
 	it('should be a function', () => {
 		assert(typeof t.constant === 'function');

mod.ts

@@ -51,6 +51,7 @@ export type Infer<T> =
 			& { [K in keyof P as P[K] extends _optional<infer _> ? K : never]?: Infer<P[K]> }
 			& { [K in keyof P as P[K] extends _optional<infer _> ? never : K]: Infer<P[K]> }
 		>
+	: T extends _unknown ? unknown
 	: T;
 
 /**
@@ -90,6 +91,7 @@ export type Type =
 	| _object
 	| _string
 	| _tuple<unknown>
+	| _unknown
 	| _all<unknown>
 	| _any<unknown>
 	| _one<unknown>
@@ -211,6 +213,27 @@ function _null(options?: Omit<_null, 'type'>): _null {
 	return { ...options, type: 'null' };
 }
 
+/**
+ * An unknown type.
+ *
+ * > [!IMPORTANT]
+ * > Equivalent to `unknown` in TypeScript, which allows any value.
+ */
+type _unknown = Annotations & {
+	default?: unknown;
+	examples?: unknown[];
+};
+
+/**
+ * Defines a schema of unknown type.
+ *
+ * > [!IMPORTANT]
+ * > Equivalent to `unknown` in TypeScript, which allows any value.
+ */
+function _unknown(options?: _unknown): _unknown {
+	return options || {};
+}
+
 /**
 * A constant literal value.
 
@@ -817,4 +840,5 @@ export {
 	_object as object,
 	_string as string,
 	_tuple as tuple,
+	_unknown as unknown,
 }