Use AST's type field and merge types for unary, binary & compare ICs

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 59931bf5ddb3ba7a9908e97b43aaa7915e731791..9a03f3d53e13ad91f8998bd0d587932e17d057d6 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -399,6 +399,18 @@ enum LanguageMode {
 };
 
 
+// A simple Maybe type, that can be passed by value.
+template<class T>
+struct Maybe {
+  Maybe() : has_value(false) {}
+  explicit Maybe(T t) : has_value(true), value(t) {}
+  Maybe(bool has, T t) : has_value(has), value(t) {}
+
+  bool has_value;
+  T value;
+};
+
+
 // The Strict Mode (ECMA-262 5th edition, 4.2.2).
 //
 // This flag is used in the backend to represent the language mode. So far