Implement correct !global assignments

Author: mgreter

environment.hpp

@@ -37,12 +37,29 @@ namespace Sass {
     bool current_frame_has(const string key) const
     { return !!current_frame_.count(key); }
 
+    void current_frame_set(const string key, T val)
+    { current_frame_[key] = val; }
+
+    void global_frame_set(const string key, T val)
+    { global_frame()->current_frame_[key] = val; }
+
     Environment* grandparent() const
     {
       if(parent_ && parent_->parent_) return parent_->parent_;
       else return 0;
     }
 
+    Environment* global_frame()
+    {
+      Environment* cur = this;
+      // looks like global variables
+      // are in the second last parent
+      while (cur->grandparent()) {
+        cur = cur->parent_;
+      }
+      return cur;
+    }
+
     bool global_frame_has(const string key) const
     {
       if(parent_ && !grandparent()) {

eval.cpp

@@ -64,12 +64,15 @@ namespace Sass {
   Expression* Eval::operator()(Assignment* a)
   {
     string var(a->variable());
-    if (env->has(var)) {
+    if (a->is_global()) {
+      env->global_frame_set(var, a->value()->perform(this));
+    }
+    else if (env->has(var)) {
       Expression* v = static_cast<Expression*>((*env)[var]);
       if (!a->is_guarded() || v->concrete_type() == Expression::NULL_VAL) (*env)[var] = a->value()->perform(this);
     }
     else {
-      env->current_frame()[var] = a->value()->perform(this);
+      env->current_frame_set(var, a->value()->perform(this));
     }
     return 0;
   }

expand.cpp

@@ -219,12 +219,15 @@ namespace Sass {
   {
     string var(a->variable());
     Selector* p = selector_stack.size() <= 1 ? 0 : selector_stack.back();
-    if (env->has(var)) {
+    if (a->is_global()) {
+      env->global_frame_set(var, a->value()->perform(eval->with(p, env, backtrace)));
+    }
+    else if (env->has(var)) {
       Expression* v = static_cast<Expression*>((*env)[var]);
       if (!a->is_guarded() || v->concrete_type() == Expression::NULL_VAL) (*env)[var] = a->value()->perform(eval->with(p, env, backtrace));
     }
     else {
-      env->current_frame()[var] = a->value()->perform(eval->with(p, env, backtrace));
+      env->current_frame_set(var, a->value()->perform(eval->with(p, env, backtrace)));
     }
     return 0;
   }

functions.cpp

@@ -145,7 +145,9 @@ namespace Sass {
     static mt19937 rand(static_cast<unsigned int>(GetSeed()));
 
     // features
-    static set<string> features;
+    static set<string> features {
+      "global-variable-shadowing"
+    };
 
     ////////////////
     // RGB FUNCTIONS