feat(types): IsUnknown, IfUnknown

Signed-off-by: Lexus Drumgold <unicornware@flexdevelopment.llc>

src/types/__tests__/if-unknown.spec-d.ts

@@ -0,0 +1,19 @@
+/**
+ * @file Type Tests - IfUnknown
+ * @module tutils/types/tests/unit-d/IfUnknown
+ */
+
+import type TestSubject from '../if-unknown'
+
+describe('unit-d:types/IfUnknown', () => {
+  type False = false
+  type True = true
+
+  it('should equal False if IsUnknown<T> extends false', () => {
+    expectTypeOf<TestSubject<unknown[], True, False>>().toEqualTypeOf<False>()
+  })
+
+  it('should equal True if IsUnknown<T> extends true', () => {
+    expectTypeOf<TestSubject<unknown, True, False>>().toEqualTypeOf<True>()
+  })
+})

src/types/__tests__/is-unknown.spec-d.ts

@@ -0,0 +1,16 @@
+/**
+ * @file Type Tests - IsUnknown
+ * @module tutils/types/tests/unit-d/IsUnknown
+ */
+
+import type TestSubject from '../is-unknown'
+
+describe('unit-d:types/IsUnknown', () => {
+  it('should equal false if T is not unknown', () => {
+    expectTypeOf<TestSubject<null>>().toEqualTypeOf<false>()
+  })
+
+  it('should equal true if T is unknown', () => {
+    expectTypeOf<TestSubject<unknown>>().toEqualTypeOf<true>()
+  })
+})

src/types/if-unknown.ts

@@ -0,0 +1,20 @@
+/**
+ * @file Type Definitions - IfUnknown
+ * @module tutils/types/IfUnknown
+ */
+
+import type IsUnknown from './is-unknown'
+
+/**
+ * Conditional type that resolves depending on whether or not `T` is type
+ * `unknown`.
+ *
+ * @see {@linkcode IsUnknown}
+ *
+ * @template T - Type to evaluate
+ * @template True - Type if `T` is type `unknown`
+ * @template False - Type if `T` is not type `unknown`
+ */
+type IfUnknown<T, True, False> = IsUnknown<T> extends true ? True : False
+
+export type { IfUnknown as default }

src/types/index.ts

@@ -38,6 +38,7 @@ export type { default as IfString } from './if-string'
 export type { default as IfSymbol } from './if-symbol'
 export type { default as IfTuple } from './if-tuple'
 export type { default as IfUndefined } from './if-undefined'
+export type { default as IfUnknown } from './if-unknown'
 export type { default as IndexSignature } from './index-signature'
 export type { default as IsAny } from './is-any'
 export type { default as IsArray } from './is-array'
@@ -55,6 +56,7 @@ export type { default as IsString } from './is-string'
 export type { default as IsSymbol } from './is-symbol'
 export type { default as IsTuple } from './is-tuple'
 export type { default as IsUndefined } from './is-undefined'
+export type { default as IsUnknown } from './is-unknown'
 export type { default as Join } from './join'
 export type { default as JsonArray } from './json-array'
 export type { default as JsonObject } from './json-object'

src/types/is-unknown.ts

@@ -0,0 +1,19 @@
+/**
+ * @file Type Definitions - IsUnknown
+ * @module tutils/types/IsUnknown
+ */
+
+import type IsNull from './is-null'
+
+/**
+ * Returns a boolean indicating if `T` is type `unknown`.
+ *
+ * @template T - Type to evaluate
+ */
+type IsUnknown<T> = unknown extends T
+  ? IsNull<T> extends false
+    ? true
+    : false
+  : false
+
+export type { IsUnknown as default }