From a335a12bc9f0f1a44cceee887245c2258e1b99f6 Mon Sep 17 00:00:00 2001
From: Trevor Florence <trevorade@users.noreply.github.com>
Date: Tue, 29 Nov 2022 08:07:46 -0700
Subject: [PATCH] Prevent the .not modifier from being chained (#20)

---
 src/index.ts       | 2 +-
 test/types.test.ts | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/index.ts b/src/index.ts
index 2e4532b..f936b4e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -143,7 +143,7 @@ export interface ExpectTypeOf<Actual, B extends boolean> {
       ? never
       : ExpectTypeOf<T, B>
     : never
-  not: ExpectTypeOf<Actual, Not<B>>
+  not: Omit<ExpectTypeOf<Actual, Not<B>>, 'not'>
 }
 const fn: any = () => true
 
diff --git a/test/types.test.ts b/test/types.test.ts
index 9e69af1..11fbe9b 100644
--- a/test/types.test.ts
+++ b/test/types.test.ts
@@ -70,6 +70,11 @@ test(`never types don't sneak by`, () => {
   expectTypeOf<never>().toMatchTypeOf<{foo: string}>()
 })
 
+test('not cannot be chained', () => {
+  // @ts-expect-error
+  expectTypeOf<number>().not.not.toBeNumber()
+})
+
 test('constructor params', () => {
   // The built-in ConstructorParameters type helper fails to pick up no-argument overloads.
   // This test checks that's still the case to avoid unnecessarily maintaining a workaround,