From 52166e354617e222cd0a92c581411cb1f60d4fc0 Mon Sep 17 00:00:00 2001
From: n5m <72841454+n5m@users.noreply.github.com>
Date: Mon, 31 Oct 2022 10:20:06 +0000
Subject: [PATCH] allow deferred close of nil stream (#20706)

* allow deferred close of nil stream

* improve example
---
 lib/pure/streams.nim      | 18 ++++++++++++++----
 tests/stdlib/tstreams.nim |  6 ++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/lib/pure/streams.nim b/lib/pure/streams.nim
index 50b3085d2..7ebae3e09 100644
--- a/lib/pure/streams.nim
+++ b/lib/pure/streams.nim
@@ -173,10 +173,20 @@ proc close*(s: Stream) =
   ## See also:
   ## * `flush proc <#flush,Stream>`_
   runnableExamples:
-    var strm = newStringStream("The first line\nthe second line\nthe third line")
-    ## do something...
-    strm.close()
-  if not isNil(s.closeImpl): s.closeImpl(s)
+    block:
+      let strm = newStringStream("The first line\nthe second line\nthe third line")
+      ## do something...
+      strm.close()
+      
+    block:
+      let strm = newFileStream("amissingfile.txt")
+      # deferring works even if newFileStream fails
+      defer: strm.close()
+      if not isNil(strm):
+        ## do something...
+
+  if not isNil(s) and not isNil(s.closeImpl):
+    s.closeImpl(s)
 
 proc atEnd*(s: Stream): bool =
   ## Checks if more data can be read from `s`. Returns ``true`` if all data has
diff --git a/tests/stdlib/tstreams.nim b/tests/stdlib/tstreams.nim
index 08441a766..891b38e20 100644
--- a/tests/stdlib/tstreams.nim
+++ b/tests/stdlib/tstreams.nim
@@ -50,6 +50,12 @@ block tstreams3:
       echo line
     s.close
 
+
+block:
+  let fs = newFileStream("amissingfile.txt")
+  defer: fs.close()
+  doAssert isNil(fs)
+
 # bug #12410
 
 var a = newStringStream "hehohihahuhyh"