support never for type testing (#37)

huan · Mar 25, 2022 · 4a9462a · 4a9462a
1 parent 0917837
commit 4a9462a
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Showing 2 changed files with 14 additions and 2 deletions.
diff --git a/src/assert-equal.spec.ts b/src/assert-equal.spec.ts
@@ -11,3 +11,15 @@ test('AssertEqual smoke testing', async (t) => {
 
   t.ok(typeTest, 'should pass the typing test')
 })
+
+/**
+ * Issue #37
+ *  @link https://github.com/huan/tstest/issues/37
+ */
+test('AssertEqual with `never`', async (t) => {
+  type T = never
+  type EXPECTED_TYPE = never
+  const typeTest: AssertEqual<T, EXPECTED_TYPE> = true
+
+  t.ok(typeTest, 'should pass the typing test')
+})
diff --git a/src/assert-equal.ts b/src/assert-equal.ts
@@ -6,8 +6,8 @@
  *    https://2ality.com/2019/07/testing-static-types.html
  */
 type AssertEqual<T, Expected> =
-  T extends Expected
-    ? (Expected extends T ? true : never)
+  [T] extends [Expected]
+    ? ([Expected] extends [T] ? true : never)
     : never
 
 export type {