Add eager forward merging

Author: mgreter

src/ast_css.hpp

@@ -8,6 +8,8 @@
 #include "ast_nodes.hpp"
 #include "ast_selectors.hpp"
 #include "visitor_css.hpp"
+#include "ast_statements.hpp"
+#include "environment_stack.hpp"
 // #include "ast_def_macros.hpp"
 
 namespace Sass {
@@ -554,6 +556,12 @@ namespace Sass {
     bool isActive = false;
     bool isLoading = false;
 
+
+    EnvKeyMap<VarRef> mergedFwdVars;
+    EnvKeyMap<VarRef> mergedFwdMixs;
+    EnvKeyMap<VarRef> mergedFwdFns;
+
+
     sass::vector<std::pair<VarRefs*, Root*>> forwarded;
 
     Root(const SourceSpan& pstate, size_t reserve = 0)

src/environment_stack.hpp

@@ -59,6 +59,11 @@ namespace Sass {
         && offset == rhs.offset;
     }
 
+    bool operator!=(const VarRef& rhs) const {
+      return frame != rhs.frame
+        || offset != rhs.offset;
+    }
+
     bool operator<(const VarRef& rhs) const {
       if (frame < rhs.frame) return true;
       return offset < rhs.offset;

src/extender.cpp

@@ -73,7 +73,8 @@ namespace Sass {
 
       if (complex->size() > 1) {
         throw Exception::RuntimeException(traces,
-          "complex selectors may not be extended.");
+          "Can't extend complex selector " +
+          complex->inspect() + ".");
       }
 
       if (const CompoundSelector* compound = complex->first()->isaCompoundSelector()) {