close #16786 (#17598)

tests/async/tasyncintemplate.nim

@@ -1,12 +1,46 @@
 discard """
-  output: 42
+  output: '''
+42
+1
+2
+3
+4
+'''
 """
 
 import asyncdispatch
 
+# bug #16159
 template foo() =
   proc temp(): Future[int] {.async.} = return 42
   proc tempVoid(): Future[void] {.async.} = echo await temp()
 
 foo()
 waitFor tempVoid()
+
+
+block: # bug #16786
+  block:
+    proc main(a: int|string)=
+      proc bar(b: int|string) = echo b
+      bar(a)
+    main(1)
+
+  block:
+    proc main(a: int) : Future[void] {.async.} =
+      proc bar(b: int): Future[void] {.async.} = echo b
+      await bar(a)
+    waitFor main(2)
+
+  block:
+    proc main(a: int) : Future[void] {.async.} =
+      proc bar(b: int | string): Future[void] {.async.} = echo b
+      await bar(a)
+    waitFor main(3)
+
+  block:
+    # bug
+    proc main(a: int|string) =
+      proc bar(b: int): Future[void] {.async.} = echo b
+      waitFor bar(a)
+    main(4)