Implement simple effect typing for variables

src/types.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 285 matching lines @@
 struct Bounds {
   Handle<Type> lower;
   Handle<Type> upper;
 
   Bounds() {}
   Bounds(Handle<Type> l, Handle<Type> u) : lower(l), upper(u) {}
   Bounds(Type* l, Type* u, Isolate* isl) : lower(l, isl), upper(u, isl) {}
   explicit Bounds(Handle<Type> t) : lower(t), upper(t) {}
   Bounds(Type* t, Isolate* isl) : lower(t, isl), upper(t, isl) {}
 
+  // Unrestricted bounds.
+  static Bounds Unbounded(Isolate* isl) {
+    return Bounds(Type::None(), Type::Any(), isl);
+  }
+
   // Meet: both b1 and b2 are known to hold.
   static Bounds Both(Bounds b1, Bounds b2, Isolate* isl) {
     return Bounds(
         handle(Type::Union(b1.lower, b2.lower), isl),
         handle(Type::Intersect(b1.upper, b2.upper), isl));
   }
 
   // Join: either b1 or b2 is known to hold.
   static Bounds Either(Bounds b1, Bounds b2, Isolate* isl) {
     return Bounds(
         handle(Type::Intersect(b1.lower, b2.lower), isl),
         handle(Type::Union(b1.upper, b2.upper), isl));
   }
 
   static Bounds NarrowLower(Bounds b, Handle<Type> t, Isolate* isl) {
     return Bounds(handle(Type::Union(b.lower, t), isl), b.upper);
   }
   static Bounds NarrowUpper(Bounds b, Handle<Type> t, Isolate* isl) {
     return Bounds(b.lower, handle(Type::Intersect(b.upper, t), isl));
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_TYPES_H_