redef fun isset_attribute(a, recv)
	do
		self.check_recv_notnull(recv)
		var res = self.new_var(bool_type)

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

		if mtype isa MNullableType then
			self.add("{res} = 1; /* easy isset: {a} on {recv.inspect} */")
			return res
		end

		self.require_declaration(a.const_color)
		if self.compiler.modelbuilder.toolcontext.opt_no_union_attribute.value then
			self.add("{res} = {recv}->attrs[{a.const_color}] != NULL; /* {a} on {recv.inspect}*/")
		else

			if not mtype.is_c_primitive and not mtype.is_tagged then
				self.add("{res} = {recv}->attrs[{a.const_color}].val != NULL; /* {a} on {recv.inspect} */")
			else
				self.add("{res} = 1; /* NOT YET IMPLEMENTED: isset of primitives: {a} on {recv.inspect} */")
			end
		end
		return res
	end

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

		var types = self.collect_types(recv)
		var res = self.new_var(bool_type)

		if types.is_empty then
			self.add("/*BUG: no live types for {recv.inspect} . {a}*/")
			self.bugtype(recv)
			return res
		end
		self.add("/* isset {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 attr = self.new_expr("((struct {t.c_name}*){recv})->{a.intro.c_name}", ta)
			if not ta isa MNullableType then
				if not ta.is_c_primitive then
					self.add("{res} = ({attr} != NULL);")
				else
					self.add("{res} = 1; /*NOTYET isset on primitive attributes*/")
				end
			end
			self.add("break;")
		end
		if self.compiler.hardening then
			self.add("default: /* Bug */")
			self.bugtype(recv)
		end
		self.add("\}")

		return res
	end