Proposed resolution, June, 2019:

Change _N4868_.6.5.6 [basic.lookup.classref] paragraph 1 as follows:

In a class member access expression (7.6.1.5 [expr.ref]), if the . or -> token is immediately followed by an identifier followed by a <, the identifier must be looked up to determine whether the < is the beginning of a template argument list (13.3 [temp.names]) or a less-than operator. The identifier is first looked up in the class of the object expression (6.5.2 [class.member.lookup]). If the identifier is not found, it is then looked up in the context of the entire postfix-expression and shall name a class template whose specializations are types.

[Accepted as a DR at the July, 2019 meeting.]

_N4868_.6.5.6 [basic.lookup.classref] does not mention template aliases as the possible result of the lookup but should do so.