From e155dc6f44e131201196c5537bff363d9d0b79bb Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=A9r=C3=B4me=20Benoit?= <jerome.benoit@piment-noir.org>
Date: Wed, 16 Oct 2024 17:50:36 +0200
Subject: [PATCH] perf: speed up isAsyncFunction() helper
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Signed-off-by: Jérôme Benoit <jerome.benoit@piment-noir.org>
---
 src/utils.ts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/utils.ts b/src/utils.ts
index 0e1266a1..3e22b8c1 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -141,6 +141,8 @@ export const isKillBehavior = <KB extends KillBehavior>(
   return value === killBehavior
 }
 
+type AsyncFunctionType<A extends unknown[], R> = (...args: A) => PromiseLike<R>
+
 /**
  * Detects whether the given value is an asynchronous function or not.
  * @param fn - Unknown value.
@@ -149,8 +151,9 @@ export const isKillBehavior = <KB extends KillBehavior>(
  */
 export const isAsyncFunction = (
   fn: unknown
-): fn is (...args: unknown[]) => Promise<unknown> => {
-  return typeof fn === 'function' && fn.constructor.name === 'AsyncFunction'
+): fn is AsyncFunctionType<unknown[], unknown> => {
+  // eslint-disable-next-line @typescript-eslint/no-empty-function
+  return fn?.constructor === (async () => {}).constructor
 }
 
 /**
-- 
2.34.1