Add typing events for TypeBuilder.

ncc/hierarchy/ClassMembers.n

@@ -934,6 +934,12 @@ public partial class MethodBuilder : MemberBuilder, IMethod
       {
         | FunBody.Parsed =>
           def typer =  Manager.ComponentsFactory.CreateTyper (this);
+
+          // Subscribe to events in typer and forward them to the declaring type.
+          typer.BeforeStage2 += (s, e) => declaring_type.OnMethodBeforeStage2(s, e);
+          typer.BeforeStage3 += (s, e) => declaring_type.OnMethodBeforeStage3(s, e);
+          typer.BeforeStage4 += (s, e) => declaring_type.OnMethodBeforeStage4(s, e);     
+
           typer.RunFullTyping ();
         | _ => ()
       }

ncc/hierarchy/TypeBuilder.n

@@ -126,6 +126,10 @@ public partial class TypeBuilder : TypeInfo
   internal mutable iterate_first : list[TypeBuilder];
 
   mutable is_special_variant_methods_added : bool;
+
+  public event MethodBeforeStage2 : EventHandler[StageEventArgs];
+  public event MethodBeforeStage3 : EventHandler[StageEventArgs];
+  public event MethodBeforeStage4 : EventHandler[StageEventArgs];
 
   public this (manager : TypesManager, par : TypeBuilder, td : PT.TopDeclaration,
                  ns_node : NamespaceTree.Node)
@@ -196,6 +200,37 @@ public partial class TypeBuilder : TypeInfo
       };
   }
 
+  /// <summary>
+  /// Raises MethodBeforeStage2 event.
+  /// </summary>
+  public OnMethodBeforeStage2(_ : object, args : StageEventArgs) : void
+  {
+    RaiseBeforeStage(MethodBeforeStage2, args);
+  }
+
+  /// <summary>
+  /// Raises MethodBeforeStage3 event.
+  /// </summary>
+  public OnMethodBeforeStage3(_ : object, args : StageEventArgs) : void
+  {
+    RaiseBeforeStage(MethodBeforeStage3, args);
+  }
+
+  /// <summary>
+  /// Raises MethodBeforeStage4 event.
+  /// </summary>
+  public OnMethodBeforeStage4(_ : object, args : StageEventArgs) : void
+  {
+    RaiseBeforeStage(MethodBeforeStage4, args);
+  }
+
+  private RaiseBeforeStage(evt : EventHandler[StageEventArgs], args : StageEventArgs) : void
+  {
+    def e = evt;
+    when (e != null)
+      e(this, args);
+  }
+
   internal CalcAccessibility() : void
   {
     mutable resuleAccessModifiers = NemerleModifiers.None;