Proposed resolution (October, 2015):

Change 9.7.1 [dcl.enum] paragraph 1 as follows:

...A : following “enum nested-name-specifier_opt identifier” within the decl-specifier-seq of a member-declaration is parsed as part of an enum-base. [Note: This resolves a potential ambiguity...

[Adopted at the February, 2016 meeting.]

The resolution of issue 1966 does not apply to the case where the enumeration name is qualified, e.g.,

  enum E : int;
  struct X {
    enum ::E : int();
  };