From f02de25ca1b660b0b6e1ae2d4981106744814fe3 Mon Sep 17 00:00:00 2001
From: konsumlamm <44230978+konsumlamm@users.noreply.github.com>
Date: Tue, 31 Aug 2021 08:14:05 +0200
Subject: [PATCH] Fix  #15150 (#18730)

---
 lib/pure/asyncfile.nim | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/pure/asyncfile.nim b/lib/pure/asyncfile.nim
index c51b338e3..222a89b97 100644
--- a/lib/pure/asyncfile.nim
+++ b/lib/pure/asyncfile.nim
@@ -202,10 +202,11 @@ proc readBuffer*(f: AsyncFile, buf: pointer, size: int): Future[int] =
 
 proc read*(f: AsyncFile, size: int): Future[string] =
   ## Read `size` bytes from the specified file asynchronously starting at
-  ## the current position of the file pointer.
+  ## the current position of the file pointer. `size` should be greater than zero.
   ##
   ## If the file pointer is past the end of the file then an empty string is
   ## returned.
+  assert size > 0
   var retFuture = newFuture[string]("asyncfile.read")
 
   when defined(windows) or defined(nimdoc):