2 files changed, 31 insertions(+), 6 deletions(-)

M lib/dhall/as_dhall.rb
M lib/dhall/util.rb

@@ 1,6 1,7 @@
 # frozen_string_literal: true
 
 require "ostruct"
+require "psych"
 
 module Dhall
 	module AsDhall


@@ 189,18 190,28 @@ module Dhall
 			end
 		end
 
-		refine ::Object do
+		refine ::Psych::Coder do
 			def as_dhall
-				ivars = instance_variables.each_with_object({}) { |ivar, h|
-					h[ivar.to_s[1..-1]] = instance_variable_get(ivar)
-				}.as_dhall
+				case type
+				when :seq
+					seq
+				when :map
+					map
+				else
+					scalar
+				end.as_dhall
+			end
+		end
 
-				type = TypeChecker.for(ivars).annotate(TypeChecker::Context.new).type
+		refine ::Object do
+			def as_dhall
 				tag = self.class.name
+				expr = Util.psych_coder_from(tag, self).as_dhall
+				type = TypeChecker.for(expr).annotate(TypeChecker::Context.new).type
 				Union.from(
 					UnionType.new(alternatives: { tag => type }),
 					tag,
-					ivars
+					expr
 				)
 			end
 		end

@@ 84,5 84,19 @@ module Dhall
 				end]
 			end
 		end
+
+		def self.psych_coder_from(tag, o)
+			coder = Psych::Coder.new(tag)
+
+			if o.respond_to?(:encode_with)
+				o.encode_with(coder)
+			else
+				o.instance_variables.each do |ivar|
+					coder[ivar.to_s[1..-1]] = o.instance_variable_get(ivar)
+				end
+			end
+
+			coder
+		end
 	end
 end