safe navigation attrset
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52234 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
safe navigation attrset
attribute assignment. [Feature #11537]
non-attrset as the sign of safe navigation.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52234 b2dd03c8-39d4-4d8f-98ff-823fe69b080e