infer enum types

examples/math/math.nub

@@ -29,7 +29,11 @@ export enum message {
 
 export func add(a: i32 b: i32): i32
 {
-    let message: message = enum math::message::move struct color { r = 23 g = 46 b = 56 }
+    let message: message = enum message::move { 
+        r = 23
+        g = 46
+        b = 56
+    }
 
     match message {
         quit q {}