From 6085ad95ff4f712d14de2786a8bd5e2cea4397df Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Tue, 9 Jun 2020 20:39:26 +0200
Subject: [PATCH] fixes #14279 (#14618)

---
 compiler/closureiters.nim |  8 ++++++--
 tests/async/tasynctry.nim | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/compiler/closureiters.nim b/compiler/closureiters.nim
index 3422a8a46c..675f1ae413 100644
--- a/compiler/closureiters.nim
+++ b/compiler/closureiters.nim
@@ -129,7 +129,7 @@
 #   break :stateLoop
 
 import
-  ast, msgs, idents,
+  ast, astalgo, msgs, idents,
   renderer, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos
 
 type
@@ -388,6 +388,10 @@ proc hasYieldsInExpressions(n: PNode): bool =
           return true
     else:
       result = n.hasYields
+  of nkCast:
+    for i in 1..<n.len:
+      if n[i].hasYieldsInExpressions:
+        return true
   else:
     for c in n:
       if c.hasYieldsInExpressions:
@@ -686,7 +690,7 @@ proc lowerStmtListExprs(ctx: var Ctx, n: PNode, needsSplit: var bool): PNode =
   of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv,
       nkDerefExpr, nkHiddenDeref:
     var ns = false
-    for i in 0..<n.len:
+    for i in ord(n.kind == nkCast)..<n.len:
       n[i] = ctx.lowerStmtListExprs(n[i], ns)
 
     if ns:
diff --git a/tests/async/tasynctry.nim b/tests/async/tasynctry.nim
index fa34936161..25eab87fbe 100644
--- a/tests/async/tasynctry.nim
+++ b/tests/async/tasynctry.nim
@@ -5,6 +5,7 @@ Specific except
 Multiple idents in except
 Multiple except branches
 Multiple except branches 2
+success
 '''
 targets: "c"
 """
@@ -101,3 +102,17 @@ assert y.waitFor() == 2
 
 y = test4()
 assert y.waitFor() == 2
+
+# bug #14279
+
+proc expandValue: Future[int] {.async.} =
+  return 0
+
+proc a(b: int): Future[void] {.async.} =
+  return
+
+proc b: Future[void] {.async.} =
+  await a(await expandValue())
+  echo "success"
+
+waitFor(b())