Use @:persistent as necessary.

.haxerc

@@ -1,4 +1,4 @@
 {
-  "version": "4.0.0-rc.1",
+  "version": "4.0.0-rc.3",
   "resolveLibs": "scoped"
 }

src/tink/MacroApi.hx

@@ -42,7 +42,7 @@ class MacroApi {
     return None;
   }
 
-  static var idCounter = 0;  
+  @:persistent static var idCounter = 0;  
   
   @:noUsing static public inline function tempName(?prefix:String = 'tmp'):String
     return '__tink_' + prefix + Std.string(idCounter++);

src/tink/macro/BuildCache.hx

@@ -33,7 +33,7 @@ typedef BuildContext3 = {>BuildContext2,
 
 class BuildCache { 
   
-  static var cache = new Map();
+  @:persistent static var cache = new Map();
   
   static public function getType3(name, ?types, ?pos:Position, build:BuildContext3->TypeDefinition) {
      if (types == null)