2 files changed, 30 insertions, 7 deletions
diff --git a/st/ClassInstance.java b/st/ClassInstance.java
index d51446f..804b1b0 100644
--- a/st/ClassInstance.java
+++ b/st/ClassInstance.java
@@ -29,13 +29,9 @@ public class ClassInstance extends AbstractInstance {
         else
             return false;
 
-        if (o.getName().equals(this.getName())) {
-            MinimalLogger.info(String.format("Found extension end."));
-            if (o.getExtend() != null && o.getExtend().equals(this.getExtend()))
-                throw new TypecheckException(String.format("Recursive extension on %s detected",
-                                                           this.toString()));
+        if (o.getName().equals(this.getName()))
             return true;
-        } else
+        else
             MinimalLogger.info(String.format("I (%s) do not have the same name as %s... Checking if I extend...",
                                              this.getName(), o.getName()));
 
@@ -53,6 +49,33 @@ public class ClassInstance extends AbstractInstance {
         return false;
     }
 
+    public void recursiveExtendFilter() {
+        ClassInstance ce = this.getExtend();
+        if (ce != null)
+            this.findMyselfHelper(ce);
+    }
+
+    public boolean findMyselfHelper(ClassInstance c) {
+        /**
+         * Returns true if there is a path through extensions that reaches
+         * the original class. Such a case is a type error.
+         */
+        if (this.getName().equals(c.getName())) {
+            MinimalLogger.info(String.format("%s is part of an extension loop!",
+                                             this.getName()));
+            throw new TypecheckException(String.format("Recursive extension detected!"));
+        }
+
+        if (c.getExtend() == null) {
+            MinimalLogger.info(String.format("Search ended at %s.",
+                                             c.getName()));
+            return false;
+        }
+
+        ClassInstance ce = c.getExtend();
+        return this.findMyselfHelper(ce);
+    }
+
     public ClassInstance getExtend() {
         /**
          * Returns the parent class, or
diff --git a/st/SymbolTable.java b/st/SymbolTable.java
index 7b509b2..68a2829 100644
--- a/st/SymbolTable.java
+++ b/st/SymbolTable.java
@@ -56,7 +56,7 @@ public class SymbolTable {
                                          cls.getName(),
                                          ext.getName()));
         cls.setExtend(ext);
-        ext.equalsOnExtend(cls); // finds recursive extensions
+        cls.recursiveExtendFilter();
         TokenKey k;
         for (TypeInstance t : ext.getLocals()) {
             k = new TokenKey(t.getName(), TypeEnum.integer,