diff --git a/examples/.idea/misc.xml b/examples/.idea/misc.xml
index 778bf31bc07..dfc122f5da0 100644
--- a/examples/.idea/misc.xml
+++ b/examples/.idea/misc.xml
@@ -3,6 +3,9 @@
   <component name="DependencyValidationManager">
     <option name="SKIP_IMPORT_STATEMENTS" value="false" />
   </component>
+  <component name="EntryPointsManager">
+    <entry_points version="2.0" />
+  </component>
   <component name="JavadocGenerationManager">
     <option name="OUTPUT_DIRECTORY" />
     <option name="OPTION_SCOPE" value="protected" />
diff --git a/examples/.idea/projectCodeStyle.xml b/examples/.idea/projectCodeStyle.xml
index 8b60e241aaf..c621643589d 100644
--- a/examples/.idea/projectCodeStyle.xml
+++ b/examples/.idea/projectCodeStyle.xml
@@ -11,6 +11,7 @@
           <option name="SMART_TABS" value="false" />
           <option name="LABEL_INDENT_SIZE" value="0" />
           <option name="LABEL_INDENT_ABSOLUTE" value="false" />
+          <option name="USE_RELATIVE_INDENTS" value="false" />
         </ADDITIONAL_INDENT_OPTIONS>
         <ADDITIONAL_INDENT_OPTIONS fileType="java">
           <option name="INDENT_SIZE" value="4" />
@@ -20,6 +21,7 @@
           <option name="SMART_TABS" value="false" />
           <option name="LABEL_INDENT_SIZE" value="0" />
           <option name="LABEL_INDENT_ABSOLUTE" value="false" />
+          <option name="USE_RELATIVE_INDENTS" value="false" />
         </ADDITIONAL_INDENT_OPTIONS>
         <ADDITIONAL_INDENT_OPTIONS fileType="xml">
           <option name="INDENT_SIZE" value="4" />
@@ -29,6 +31,7 @@
           <option name="SMART_TABS" value="false" />
           <option name="LABEL_INDENT_SIZE" value="0" />
           <option name="LABEL_INDENT_ABSOLUTE" value="false" />
+          <option name="USE_RELATIVE_INDENTS" value="false" />
         </ADDITIONAL_INDENT_OPTIONS>
       </value>
     </option>
diff --git a/examples/examples.iml b/examples/examples.iml
index 26a958a9c8a..d5c07432750 100644
--- a/examples/examples.iml
+++ b/examples/examples.iml
@@ -5,7 +5,7 @@
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
     </content>
-    <orderEntry type="jdk" jdkName="1.6" jdkType="JavaSDK" />
+    <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
 </module>
diff --git a/examples/src/PolymorphicClassObjects.jetl b/examples/src/PolymorphicClassObjects.jetl
index e69de29bb2d..d9810048d82 100644
--- a/examples/src/PolymorphicClassObjects.jetl
+++ b/examples/src/PolymorphicClassObjects.jetl
@@ -0,0 +1,31 @@
+virtual class Builder<E, R> {
+  [operator] fun plusAssign(item : E)
+  fun result() : R
+}
+
+virtual class Buildable {
+  fun newBuilder<E, R>() : Builder<E, R>
+}
+
+class List<T> {
+
+  class object Buildable {
+    override fun newBuilder<E, R>() : Builder<E, R>
+
+  }
+
+}
+
+extension Map<E> for T
+  where
+    T : Iterable<E>,
+    class object T : Buildable<E, T> {
+
+  fun map<R>(f : {(E) : R}) : T<R> = {
+    val builder = T.newBuilder()
+    for (e in this) {
+      builder += f(e)
+    }
+    builder.result()
+  }
+}
\ No newline at end of file
diff --git a/grammar/src/class_members.grm b/grammar/src/class_members.grm
index d0904bc0878..143c9243f0f 100644
--- a/grammar/src/class_members.grm
+++ b/grammar/src/class_members.grm
@@ -37,6 +37,8 @@ memberDeclaration
   : function
   : property
   : class
+  : extension
+  : typedef
   ;
 
 classObject
diff --git a/grammar/src/expressions.grm b/grammar/src/expressions.grm
index 0fe5ec86337..ed0c6054f16 100644
--- a/grammar/src/expressions.grm
+++ b/grammar/src/expressions.grm
@@ -33,6 +33,9 @@ literalConstant
 declaration
   : function
   : property
+  : extension
+  : class
+  : typedef
   ;
 
 expressionWithPrecedences // See the precedence table, everything associates to the left
diff --git a/grammar/src/modifiers.grm b/grammar/src/modifiers.grm
index 7f9bb4a73ae..9c891bdfcf9 100644
--- a/grammar/src/modifiers.grm
+++ b/grammar/src/modifiers.grm
@@ -43,5 +43,4 @@ parameterKind
   : "lazy"
   : "out"
   : "ref"
-  ;
-
+  ;
\ No newline at end of file
diff --git a/grammar/src/types.grm b/grammar/src/types.grm
index 99561cddcd5..5318da251c7 100644
--- a/grammar/src/types.grm
+++ b/grammar/src/types.grm
@@ -17,7 +17,15 @@ type
   ;
 
 userType
-  : SimpleName{"."} ("<" (modifiers type){","} ">")?
+  : (SimpleName ".")* simpleUserType{"."}
+  ;
+
+simpleUserType
+  : SimpleName ("<" (optionalProjection type){","} ">")?
+  ;
+
+optionalProjection
+  : modifiers
   ;
 
 functionType