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Rationale (October, 2012):

CWG felt that this language design question would be betterconsidered by EWG.

[Accepted at the February, 2016 meeting as part of paper P0017R1.]

The definition of an aggregate class 9.5.2 [dcl.init.aggr]was originally intended to include only C-like classes because properC++ classes were expected to encapsulate data members and useconstructors for initialization. Consequently, classes with baseswere excluded from being aggregates.

With the inclusion of aggregate initialization in list-initialization,the consequence of this decision could be surprising, so it should bereexamined. For example,

  struct A {    int& val;  };  struct B { };  struct C : B {    int& val;  };  int main() {    int i = 0;    A a { i } ;         // #1    C c { i } ;         // #2    return 0;  }

it is not clear that there is a good rationale for #1 beingwell-formed but #2 being ill-formed.