Fixed yield in nkCheckedFieldExpr (#12429) [backport]

compiler/closureiters.nim

@@ -683,7 +683,8 @@ proc lowerStmtListExprs(ctx: var Ctx, n: PNode, needsSplit: var bool): PNode =
       n[0] = ex
       result.add(n)
 
-  of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv:
+  of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv,
+      nkDerefExpr, nkHiddenDeref:
     var ns = false
     for i in 0 ..< n.len:
       n[i] = ctx.lowerStmtListExprs(n[i], ns)
@@ -757,7 +758,7 @@ proc lowerStmtListExprs(ctx: var Ctx, n: PNode, needsSplit: var bool): PNode =
         n[0] = newSymNode(ctx.g.getSysSym(n[0].info, "true"))
         n[1] = newBody
 
-  of nkDotExpr:
+  of nkDotExpr, nkCheckedFieldExpr:
     var ns = false
     n[0] = ctx.lowerStmtListExprs(n[0], ns)
     if ns:

tests/async/tasync_misc.nim

@@ -43,4 +43,14 @@ block: #8399
 
   waitFor foo("$asd")
 
+block: # nkCheckedFieldExpr
+  proc bar(): Future[JsonNode] {.async.} =
+    return newJInt(5)
+
+  proc foo() {.async.} =
+    let n = 10 + (await bar()).num
+    doAssert(n == 15)
+
+  waitFor foo()
+
 echo "ok"