Implement handling of nested :not pseudo selectors

They should not appear in the output. Ruby sass seems to
have a minor bug, as it inserts additional spaces before
the comma when the pseudo selector gets eliminated.

ast.hpp

@@ -1745,6 +1745,8 @@ namespace Sass {
     virtual unsigned long specificity() {
       return Constants::Specificity_Universal;
     };
+    virtual bool is_child(const string& name) { return false; }
+    virtual bool has_child(const string& name) { return false; }
   };
   inline Selector::~Selector() { }
 
@@ -1931,6 +1933,13 @@ namespace Sass {
     Wrapped_Selector(ParserState pstate, string n, Selector* sel)
     : Simple_Selector(pstate), name_(n), selector_(sel)
     { }
+    virtual bool is_child(const string& name) {
+      return name_ == name;
+    }
+    virtual bool has_child(const string& name) {
+      if (selector_ == 0) return false;
+      return selector_->has_child(name);
+    }
     // Selectors inside the negation pseudo-class are counted like any
     // other, but the negation itself does not count as a pseudo-class.
     virtual unsigned long specificity()
@@ -1984,6 +1993,13 @@ namespace Sass {
       { sum += (*this)[i]->specificity(); }
       return sum;
     }
+    virtual bool has_child(const string& name) {
+      for (auto el : elements()) {
+        if (el->is_child(name)) return true;
+        if (el->has_child(name)) return true;
+      }
+      return false;
+    }
     bool is_empty_reference()
     {
       return length() == 1 &&
@@ -2045,6 +2061,12 @@ namespace Sass {
       if (tail()) sum += tail()->specificity();
       return sum;
     }
+    virtual bool has_child(const string& name) {
+      return (head_ && head_->is_child(name)) ||
+             (head_ && head_->has_child(name)) ||
+             (tail_ && tail_->is_child(name)) ||
+             (tail_ && tail_->has_child(name));
+    }
     bool operator<(const Complex_Selector& rhs) const;
     bool operator==(const Complex_Selector& rhs) const;
     inline bool operator!=(const Complex_Selector& rhs) const { return !(*this == rhs); }
@@ -2126,6 +2148,15 @@ namespace Sass {
       { sum += (*this)[i]->specificity(); }
       return sum;
     }
+    virtual bool has_child(const string& name)
+    {
+      for (size_t i = 0, L = length(); i < L; ++i)
+      {
+        if ((*this)[i]->is_child(name)) return true;
+        if ((*this)[i]->has_child(name)) return true;
+      }
+      return false;
+    }
     // vector<Complex_Selector*> members() { return elements_; }
     ATTACH_OPERATIONS();
   };

output.cpp

@@ -72,6 +72,16 @@ namespace Sass {
 
   }
 
+  void Output::operator()(Wrapped_Selector* s)
+  {
+    if (s->name() == ":not(") {
+      if (s->has_child(":has(") || s->has_child(":not(")) {
+        return; // abort
+      }
+    }
+    return Inspect::operator()(s);
+  }
+
   void Output::operator()(Comment* c)
   {
     To_String to_string(ctx);

output.hpp

@@ -42,6 +42,7 @@ namespace Sass {
     virtual void operator()(Media_Block*);
     virtual void operator()(At_Rule*);
     virtual void operator()(Keyframe_Rule*);
+    virtual void operator()(Wrapped_Selector*);
     virtual void operator()(Import*);
     virtual void operator()(Comment*);
     virtual void operator()(String_Quoted*);