Calling an async proc with invalid arguments will now fail at compile-time.

lib/pure/asyncio.nim

@@ -907,6 +907,14 @@ proc transformCallWithArg(call: PNimrodNode): PNimrodNode {.compiletime.} =
       result.add newAssignment(dotExpr, call[1][i])
     else: assert false
 
+  # Add in a call to a pre-generated proc stub so that the compiler verifies
+  # the params for us :)
+  # TODO: Make sure this doesn't actually get called, maybe inline it?
+  var args: seq[PNimrodNode] = @[]
+  for i in 1 .. call[1].len-1:
+    args.add(call[1][i])
+  result.add newCall(call[1][0], args) 
+
 proc toYieldCall(n: PNimrodNode): seq[PNimrodNode] {.compileTime.} =
   ## Transforms a call/command
   if $n[0].ident != "await": error "'await' expected"
@@ -994,6 +1002,14 @@ proc isDocumentation(n: PNimrodNode): bool {.compiletime.} =
     if n[6][i].kind != nnkCommentStmt:
       return false
 
+proc createVerificationProc(procName: PNimrodNode,
+                    formalParams: PNimrodNode): PNimrodNode {.compiletime.} =
+  # TODO: Export this stub if our async proc is exported?
+  var kids: seq[PNimrodNode] = @[]
+  for i in 0 .. formalParams.len-1:
+    kids.add(formalParams[i])
+  result = newProc(procName, kids)
+
 macro async*(n: stmt): stmt {.immediate.} =
   expectKind(n, nnkProcDef)
   #echo(treeRepr(n))
@@ -1041,6 +1057,9 @@ macro async*(n: stmt): stmt {.immediate.} =
     let procDef = copyNimTree(result)
     result = newNimNode(nnkStmtList)
     result.add(transformArgs($n[0].ident, n[3]))
+    # Generate a proc stub to verify that the user passes the correct params.
+    result.add createVerificationProc(n[0], n[3])
+    
     result.add procDef
   
   #echo treeRepr(result)

tests/compile/tasyncitermacro.nim

@@ -1,4 +1,5 @@
 import sockets, asyncio, strutils
+
 proc processRequest(client: PAsyncSocket, test: string) {.async.} =
   assert test == "ahha"
   assert client != nil

tests/reject/tasyncmacroinvalidargs.nim

@@ -0,0 +1,32 @@
+discard """
+  msg: "type mismatch: got (int literal(234)) but expected 'string'"
+"""
+import sockets, asyncio, strutils
+
+proc processRequest(client: PAsyncSocket, test: string) {.async.} =
+  assert test == "ahha"
+  assert client != nil
+  echo("Test = ", test)
+  let line = await(readLine(client))
+  echo("Read: ", line)
+  
+  await send(client, "Goodbye.\c\L")
+  client.close()
+
+proc processServer() {.async.} =
+  var sock = AsyncSocket()
+  
+  # blocks:
+  sock.bindAddr(TPort(6667))
+  sock.listen()
+  
+  # Accept loop
+  while true:
+    let client: PAsyncSocket = await(accept(sock))
+    assert client != nil
+    await processRequest(client, 234)
+
+var disp = newDispatcher(false)
+disp.register(processServer, nil)
+while true:
+  discard disp.poll()