Allow for typemaps that reduce everything except null.

tests/MyString.hx

@@ -0,0 +1 @@
+typedef MyString = String;

tests/TypeMapTest.hx

@@ -1,17 +1,17 @@
 package;
 
 import haxe.unit.TestCase;
+import haxe.macro.Expr;
 
-import tink.macro.TypeMap;
-using haxe.macro.Context;
+using tink.MacroApi;
 
 class TypeMapTest extends TestCase {
 
   function testMap() {
     var t = new TypeMap();
-    var t1 = (macro [{ foo: [{ bar: '5' }]}]).typeof();
-    var t2 = (macro [{ foo: [{ bar: 5 }]}]).typeof();
-    
+    var t1 = (macro [{ foo: [{ bar: '5' }]}]).typeof().sure();
+    var t2 = (macro [{ foo: [{ bar: 5 }]}]).typeof().sure();
+
     t.set(t1, 0);
     assertEquals(Lambda.count(t), 1);
     t.set(t2, 1);
@@ -20,11 +20,29 @@ class TypeMapTest extends TestCase {
     assertEquals(Lambda.count(t), 2);
     t.set(t2, 3);
     assertEquals(Lambda.count(t), 2);
-    
+
     assertEquals(t.get(t1), 2);
     assertEquals(t.get(t2), 3);
-    
+
     assertTrue(true);
   }
-  
+
+  function testNormalization() {
+    for (settings in [
+      { count: 4, map: new TypeMap(TypeMap.noFollow)},
+      { count: 2, map: new TypeMap(TypeMap.keepNull)},
+      { count: 1, map: new TypeMap()},
+    ]) {
+
+      function set(ct:ComplexType)
+        settings.map.set(ct.toType().sure(), ct);
+
+      set(macro : String);
+      set(macro : MyString);
+      set(macro : Null<String>);
+      set(macro : Null<MyString>);
+
+      assertEquals(settings.count, Lambda.count(settings.map));
+    }
+  }
 }