progress towards adding negative type classes

[unittest bugfixes]
the block form of check now allows comments
errors when inspecting the arguments of var-accepting procs

lib/pure/unittest.nim

@@ -115,7 +115,8 @@ macro check*(conditions: stmt): stmt {.immediate.} =
     counter = 0
 
   template asgn(a, value: expr): stmt =
-    let a = value
+    var a = value # XXX: we need "var: var" here in order to
+                  # preserve the semantics of var params
   
   template print(name, value: expr): stmt =
     when compiles(string($value)):
@@ -150,7 +151,8 @@ macro check*(conditions: stmt): stmt {.immediate.} =
   of nnkStmtList:
     result = newNimNode(nnkStmtList)
     for i in countup(0, checked.len - 1):
-      result.add(newCall(!"check", checked[i]))
+      if checked[i].kind != nnkCommentStmt:
+        result.add(newCall(!"check", checked[i]))
 
   else:
     template rewrite(Exp, lineInfoLit: expr, expLit: string): stmt =