Handle multiple childs for opensymchoice (#266)

And more tests. Follow up of #261

chronos/asyncmacro2.nim

@@ -77,10 +77,9 @@ proc cleanupOpenSymChoice(node: NimNode): NimNode {.compileTime.} =
   # ref https://github.com/nim-lang/Nim/issues/11091
   if node.kind in nnkCallKinds and
     node[0].kind == nnkOpenSymChoice and node[0].eqIdent("[]"):
-    result = newNimNode(nnkBracketExpr).add(
-      cleanupOpenSymChoice(node[1]),
-      cleanupOpenSymChoice(node[2])
-    )
+    result = newNimNode(nnkBracketExpr)
+    for child in node[1..^1]:
+      result.add(cleanupOpenSymChoice(child))
   else:
     result = node.copyNimNode()
     for child in node:

tests/testmacro.nim

@@ -97,3 +97,10 @@ suite "Macro transformations test suite":
     type OpenObject = object
     macroAsync(testMacro, seq, OpenObject)
     check waitFor(testMacro()).len == 0
+
+    macro macroAsync2(name, restype, inner1, inner2, inner3, inner4: untyped): untyped =
+      quote do:
+        proc `name`(): Future[`restype`[`inner1`[`inner2`[`inner3`, `inner4`]]]] {.async.} = return
+
+    macroAsync2(testMacro2, seq, Opt, Result, OpenObject, cstring)
+    check waitFor(testMacro2()).len == 0