Fix #1170.

lib/pure/asyncdispatch.nim

@@ -869,7 +869,8 @@ proc processBody(node, retFutureSym: PNimrodNode,
     else: discard
   of nnkDiscardStmt:
     # discard await x
-    if node[0][0].kind == nnkIdent and node[0][0].ident == !"await":
+    if node[0].kind != nnkEmpty and node[0][0].kind == nnkIdent and
+          node[0][0].ident == !"await":
       var newDiscard = node
       createVar("futureDiscard_" & $toStrLit(node[0][1]), node[0][1],
                 newDiscard[0], newDiscard)

tests/async/tasyncdiscard.nim

@@ -0,0 +1,39 @@
+discard """
+  output: '''
+1
+2
+3
+4
+1
+2
+1
+6
+'''
+"""
+import asyncio, asyncdispatch, asyncnet
+
+proc main {.async.} =
+  proc f: PFuture[int] {.async.} =
+    discard
+    echo 1
+    discard
+    result = 2
+    discard
+
+  let x = await f()
+  echo x
+  echo 3
+
+  proc g: PFuture[int] {.async.} =
+    discard
+    echo 4
+    discard
+    result = 6
+    discard
+    echo await f()
+    discard await f()
+
+  discard await g()
+  echo 6
+
+main()