fix #13899 defer now works with async (#14723)

lib/pure/asyncmacro.nim

@@ -207,6 +207,9 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
                                     futureVarIdents)
   # don't do anything with forward bodies (empty)
   if procBody.kind != nnkEmpty:
+    # fix #13899, defer should not escape its original scope
+    procBody = newStmtList(newTree(nnkBlockStmt, newEmptyNode(), procBody))
+
     procBody.add(createFutureVarCompletions(futureVarIdents, nil))
 
     if not subtypeIsVoid:

tests/async/tasync_misc.nim

@@ -1,8 +1,3 @@
-discard """
-  exitcode: 0
-  output: "ok"
-"""
-
 import json, asyncdispatch
 block: #6100
   let done = newFuture[int]()
@@ -61,5 +56,21 @@ block: # 12743
 
   waitFor prc()
 
-
+block: # issue #13899
-echo "ok"
+  proc someConnect() {.async.} =
+    await sleepAsync(1)
+  proc someClose() {.async.} =
+    await sleepAsync(2)
+  proc testFooFails(): Future[bool] {.async.} =
+    await someConnect()
+    defer:
+      await someClose()
+      result = true
+  proc testFooSucceed(): Future[bool] {.async.} =
+    try:
+      await someConnect()
+    finally:
+      await someClose()
+      result = true
+  doAssert waitFor testFooSucceed()
+  doAssert waitFor testFooFails()