Adding simple implicit return

Ruby return semantics are easy to grasp, not so easy to code. So many cases.
Added support for common cases, return const/variable or call.

lib/ruby/method_statement.rb

@@ -9,9 +9,31 @@ module Ruby
     end
 
     def to_vool
+      if @body.is_a?(Statements)
+          @body << replace_return( @body.pop )
+      else
+        @body = replace_return( @body )
+      end
       Vool::MethodStatement.new( @name , @args.dup , @body.to_vool)
     end
 
+    def replace_return(statement)
+      case statement
+      when SendStatement , YieldStatement, Variable , Constant
+         return ReturnStatement.new( statement )
+      when IvarAssignment
+        ret = ReturnStatement.new( InstanceVariable.new(statement.name) )
+        return Statements.new([statement , ret])
+      when LocalAssignment
+        ret = ReturnStatement.new( LocalVariable.new(statement.name) )
+        return Statements.new([statement , ret])
+      when ReturnStatement , IfStatement , WhileStatement ,BlockStatement
+        return statement
+      else
+        raise "Not implemented implicit return #{statement.class}"
+      end
+    end
+
     def to_s(depth = 0)
       arg_str = @args.collect{|a| a.to_s}.join(', ')
       at_depth(depth , "def #{name}(#{arg_str})" , @body.to_s(depth + 1) , "end")

lib/ruby/return_statement.rb

@@ -5,7 +5,7 @@ module Ruby
     attr_reader :return_value
 
     def initialize(value)
-      @return_value = value
+      @return_value = value || NilConstant.new 
     end
 
     def to_vool

lib/ruby/statements.rb

@@ -23,6 +23,9 @@ module Ruby
     def shift
       @statements.shift
     end
+    def pop
+      @statements.pop
+    end
     def [](i)
       @statements[i]
     end

lib/vool/while_statement.rb

@@ -29,7 +29,9 @@ module Vool
     end
 
     def to_s(depth = 0)
-      at_depth(depth , "while (#{@condition})" , @body.to_s(depth + 1) , "end" )
+      lines =[ "while (#{@condition})" , @body.to_s(1) , "end"]
+      lines.unshift( @hoisted.to_s) if @hoisted
+      at_depth(depth , *lines )
     end
 
   end