move ast to tree, remove seperate helper file

lib/typed/tree.rb

@@ -0,0 +1,38 @@
+# Base class for Expresssion and Statement
+module Typed
+
+  class Code              ; end
+  class Statement < Code  ; end
+  class Expression < Code ; end
+
+end
+
+["while_statement", "if_statement" , "return_statement" , "statements",
+  "operator_expression" , "field_access" , "call_site" , "basic_values",
+  "assignment" , "class_statement" , "function_statement" , "to_code"].each do |code|
+    require_relative "tree/" + code
+end
+
+AST::Node.class_eval do
+
+  def [](name)
+    #puts self.inspect
+    children.each do |child|
+      if child.is_a?(AST::Node)
+        #puts child.type
+        if (child.type == name)
+          return child.children
+        end
+      else
+        #puts child.class
+      end
+    end
+    nil
+  end
+
+  def first_from( node_name )
+    from = self[node_name]
+    return nil unless from
+    from.first
+  end
+end