Environments now store a link to the global env. Makes it easy to handle 2-level…

Environments now store a link to the global env. Makes it easy to handle 2-level scope for mixins and arbitrarily nested scopes for variables.

context.hpp

@@ -6,17 +6,17 @@ namespace Sass {
   struct Environment {
     map<Token, Node> current_frame;
     Environment* parent;
+    Environment* global;
     
     Environment()
-    : current_frame(map<Token, Node>()), parent(0)
-    { }
-    Environment(Environment* env)
-    : current_frame(map<Token, Node>()),
-      parent(env)
+    : current_frame(map<Token, Node>()), parent(0), global(0)
     { }
     
     void link(Environment& env)
-    { parent = &env; }
+    {
+      parent = &env;
+      global = parent->global ? parent->global : parent;
+    }
     
     bool query(const Token& key) const
     {

eval_apply.cpp

@@ -277,7 +277,7 @@ namespace Sass {
       }
     }
     // cerr << "BOUND DEFAULT ARGS FOR " << string(mixin[0].token) << endl;
-    m_env.link(env.parent ? *env.parent : env);
+    m_env.link(env.global ? *env.global : env);
     // cerr << "LINKED ENVIRONMENT FOR " << string(mixin[0].token) << endl << endl;
     for (int i = 0; i < body.size(); ++i) {
       body[i] = eval(body[i], m_env);