Fix some compilation warnings.

chronos/asyncloop.nim

@@ -362,13 +362,13 @@ when defined(windows) or defined(nimdoc):
     ## Creates a new Dispatcher instance.
     new result
     result.ioPort = createIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 1)
-    when compiles(initHashSet):
+    when declared(initHashSet):
       # After 0.20.0 Nim's stdlib version
       result.handles = initHashSet[AsyncFD]()
     else:
       # Pre 0.20.0 Nim's stdlib version
       result.handles = initSet[AsyncFD]()
-    when compiles(initHeapQueue):
+    when declared(initHeapQueue):
       # After 0.20.0 Nim's stdlib version
       result.timers = initHeapQueue[TimerCallback]()
     else:
@@ -510,7 +510,12 @@ elif unixPlatform:
     ## Create new dispatcher.
     new result
     result.selector = newSelector[SelectorData]()
-    result.timers.newHeapQueue()
+    when declared(initHeapQueue):
+      # After 0.20.0 Nim's stdlib version
+      result.timers = initHeapQueue()
+    else:
+      # Before 0.20.0 Nim's stdlib version
+      result.timers.newHeapQueue()
     result.callbacks = initDeque[AsyncCallback](64)
     result.keys = newSeq[ReadyKey](64)
     result.trackers = initTable[string, TrackerBase]()

tests/testaddress.nim

@@ -8,6 +8,8 @@
 import strutils, unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "TransportAddress test suite":
   test "initTAddress(string)":
     check $initTAddress("0.0.0.0:1") == "0.0.0.0:1"

tests/testasyncstream.nim

@@ -8,6 +8,8 @@
 import strutils, unittest, os
 import ../chronos, ../chronos/streams/tlsstream
 
+when defined(nimHasUsed): {.used.}
+
 const SelfSignedRsaKey = """
 -----BEGIN PRIVATE KEY-----
 MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDSXcKMR6zIIHSy

tests/testbugs.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Asynchronous issues test suite":
   const HELLO_PORT = 45679
   const TEST_MSG = "testmsg"

tests/testdatagram.nim

@@ -8,6 +8,8 @@
 import strutils, net, unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Datagram Transport test suite":
   const
     TestsCount = 2000

tests/testfut.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Future[T] behavior test suite":
   proc testFuture1(): Future[int] {.async.} =
     await sleepAsync(0.milliseconds)

tests/testmacro.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 proc asyncRetValue(n: int): Future[int] {.async.} =
   await sleepAsync(n.milliseconds)
   result = n * 10

tests/testnet.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Network utilities test suite":
 
   const MaskVectors = [

tests/testserver.nim

@@ -8,6 +8,8 @@
 import strutils, unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Server's test suite":
   type
     CustomServer = ref object of StreamServer

tests/testsignal.nim

@@ -8,6 +8,8 @@
 import unittest, strutils
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 when not defined(windows):
   import posix
 

tests/testsoon.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "callSoon() tests suite":
   const CallSoonTests = 10
   var soonTest1 = 0'u

tests/teststream.nim

@@ -8,6 +8,8 @@
 import strutils, unittest, os
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 when defined(windows):
   import winlean
 else:

tests/testsync.nim

@@ -8,6 +8,8 @@
 import unittest
 import ../chronos
 
+when defined(nimHasUsed): {.used.}
+
 suite "Asynchronous sync primitives test suite":
   var testLockResult = ""
   var testEventResult = ""

tests/testtime.nim

@@ -8,6 +8,8 @@
 import os, unittest
 import ../chronos, ../chronos/timer
 
+when defined(nimHasUsed): {.used.}
+
 suite "Asynchronous timers test suite":
   const TimersCount = 10