add a simple return, ie the normal kind, not with trailing statements

lib/ast/expression.rb

@@ -36,6 +36,7 @@ require_relative "basic_expressions"
 require_relative "compound_expressions"
 require_relative "if_expression"
 require_relative "while_expression"
+require_relative "return_expression"
 require_relative "function_expression"
 require_relative "operator_expressions"
 require_relative "call_site_expression"

lib/ast/return_expression.rb

@@ -0,0 +1,24 @@
+module Ast
+  class ReturnExpression < Expression
+    attr_reader  :expression
+    def initialize expression
+      @expression = expression
+    end
+    def inspect
+      self.class.name + ".new(" + expression.inspect + " )"  
+    end
+    def to_s
+      "return #{expression}\n"
+    end
+    def attributes
+      [:expression]
+    end
+    def compile context , into
+      expression_value = condition.compile(context , into)
+      puts "compiled return expression #{expression_value.inspect}"
+      return expression_value
+    end
+  end
+
+  
+end