redef fun read_attribute(a, recv)
	do
		self.check_recv_notnull(recv)

		# What is the declared type of the attribute?
		var ret = a.intro.static_mtype.as(not null)
		var intromclassdef = a.intro.mclassdef
		ret = ret.resolve_for(intromclassdef.bound_mtype, intromclassdef.bound_mtype, intromclassdef.mmodule, true)

		if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
			self.compiler.attr_read_count += 1
			self.add("count_attr_reads++;")
		end

		self.require_declaration(a.const_color)
		if self.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
			# Get the attribute or a box (ie. always a val*)
			var cret = self.object_type.as_nullable
			var res = self.new_var(cret)
			res.mcasttype = ret

			self.add("{res} = {recv}->attrs[{a.const_color}]; /* {a} on {recv.inspect} */")

			# Check for Uninitialized attribute
			if not ret isa MNullableType and not self.compiler.modelbuilder.toolcontext.opt_no_check_attr_isset.value then
				self.add("if (unlikely({res} == NULL)) \{")
				self.add_abort("Uninitialized attribute {a.name}")
				self.add("\}")

				if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
					self.compiler.isset_checks_count += 1
					self.add("count_isset_checks++;")
				end
			end

			# Return the attribute or its unboxed version
			# Note: it is mandatory since we reuse the box on write, we do not whant that the box escapes
			return self.autobox(res, ret)
		else
			var res = self.new_var(ret)
			self.add("{res} = {recv}->attrs[{a.const_color}].{ret.ctypename}; /* {a} on {recv.inspect} */")

			# Check for Uninitialized attribute
			if not ret.is_c_primitive and not ret isa MNullableType and not self.compiler.modelbuilder.toolcontext.opt_no_check_attr_isset.value then
				self.add("if (unlikely({res} == NULL)) \{")
				self.add_abort("Uninitialized attribute {a.name}")
				self.add("\}")
				if self.compiler.modelbuilder.toolcontext.opt_isset_checks_metrics.value then
					self.compiler.isset_checks_count += 1
					self.add("count_isset_checks++;")
				end
			end

			return res
		end
	end

	redef fun read_attribute(a, recv)
	do
		check_recv_notnull(recv)

		var types = self.collect_types(recv)

		var ret = a.intro.static_mtype.as(not null)
		ret = self.resolve_for(ret, recv)
		var res = self.new_var(ret)

		if types.is_empty then
			self.add("/*BUG: no live types for {recv.inspect} . {a}*/")
			self.bugtype(recv)
			return res
		end
		self.add("/* read {a} on {recv.inspect} */")
		self.add("switch({recv}->classid) \{")
		var last = types.last
		for t in types do
			if not self.compiler.hardening and t == last then
				self.add("default: /*{self.compiler.classid(t)}*/")
			else
				self.add("case {self.compiler.classid(t)}:")
			end
			var recv2 = self.autoadapt(recv, t)
			var ta = a.intro.static_mtype.as(not null)
			ta = self.resolve_for(ta, recv2)
			var res2 = self.new_expr("((struct {t.c_name}*){recv})->{a.intro.c_name}", ta)
			if not ta isa MNullableType and not self.compiler.modelbuilder.toolcontext.opt_no_check_attr_isset.value then
				if not ta.is_c_primitive then
					self.add("if ({res2} == NULL) \{")
					self.add_abort("Uninitialized attribute {a.name}")
					self.add("\}")
				else
					self.add("/*NOTYET isset on primitive attributes*/")
				end
			end
			self.assign(res, res2)
			self.add("break;")
		end
		if self.compiler.hardening then
			self.add("default: /* Bug */")
			self.bugtype(recv)
		end
		self.add("\}")

		return res
	end