From 5c4b26e684da9e8d472f33c0837a1d83479a38ab Mon Sep 17 00:00:00 2001
From: Jesse McNelis <jessta@gmail.com>
Date: Tue, 6 Jun 2023 17:15:59 +1000
Subject: [PATCH] Fix type of Base argument to createError (#106)

---
 types/index.d.ts      | 12 ++++++------
 types/index.test-d.ts |  4 ++++
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/types/index.d.ts b/types/index.d.ts
index 3dd0873..e0d7a12 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -1,22 +1,22 @@
-declare function createError<C extends string, SC extends number, Arg extends unknown[] = [any?, any?, any?]> (
+declare function createError<C extends string, SC extends number, Arg extends unknown[] = [any?, any?, any?], Err extends Error = Error> (
   code: C,
   message: string,
   statusCode: SC,
-  Base?: Error
+  Base?: new () => Err
 ): createError.FastifyErrorConstructor<{ code: C, statusCode: SC }, Arg>
 
-declare function createError<C extends string, Arg extends unknown[] = [any?, any?, any?]> (
+declare function createError<C extends string, Arg extends unknown[] = [any?, any?, any?], Err extends Error = Error> (
   code: C,
   message: string,
   statusCode?: number,
-  Base?: Error
+  Base?: new () => Err
 ): createError.FastifyErrorConstructor<{ code: C }, Arg>
 
-declare function createError<Arg extends unknown[] = [any?, any?, any?]> (
+declare function createError<Arg extends unknown[] = [any?, any?, any?], Err extends Error = Error> (
   code: string,
   message: string,
   statusCode?: number,
-  Base?: Error
+  Base?: new () => Err
 ): createError.FastifyErrorConstructor<{ code: string }, Arg>
 
 type CreateError = typeof createError
diff --git a/types/index.test-d.ts b/types/index.test-d.ts
index a31a4b0..69eaaaf 100644
--- a/types/index.test-d.ts
+++ b/types/index.test-d.ts
@@ -65,3 +65,7 @@ expectError(new CustomTypedArgError6('a', 'b'))
 expectError(new CustomTypedArgError6('a', 'b', 'c'))
 CustomTypedArgError6('a', 'b', 'c', 'd')
 expectError(new CustomTypedArgError6('a', 'b', 'c', 'd', 'e'))
+
+
+const CustomErrorWithErrorConstructor = createError('ERROR_CODE', 'message', 500, TypeError)
+expectType<FastifyErrorConstructor<{ code: 'ERROR_CODE', statusCode: 500 }>>(CustomErrorWithErrorConstructor)