This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 109b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2022-09-25


2321. Conditional operator and cv-qualified class prvalues

Section: 7.6.16  [expr.cond]     Status: CD5     Submitter: Richard Smith     Date: 2016-09-06

[Accepted as a DR at the June, 2018 (Rapperswil) meeting.]

The following example is ill-formed:

  struct A {};
  struct B : A {};
  using T = const B;
  A a = true ? A() : T();

We don't convert from A to T because we can't form an implicit conversion sequence. We don't convert from T to A because T is more cv-qualified (even though we could form an implicit conversion sequence). It would seem reasonable to accept this case; it seems that we should only be using cv-qualifiers as a tie-breaker if the class types are otherwise the same.

Proposed resolution (March, 2018):

Change 7.6.16 [expr.cond] bullet 4.3 as follows:

...Attempts are made to form an implicit conversion sequence from an operand expression E1 of type T1 to a target type related to the type T2 of the operand expression E2 as follows: