Document number: P1018r2
Audience: WG21

Ville Voutilainen

Evolution status after San Diego 2018


This paper is a collection of items Evolution has worked on up to and in the San Diego meeting, their status, and plans for the future.


We reviewed P1141R1, Yet another approach for constrained declarations, and approved it. Core moved it in San Diego. In addition, we approved P0848R0, Conditionally Trivial Special Member Functions.

We did not look at P0782R2, Constraining Concepts Overload Sets, despite it being on the agenda. This proposal changes dependent calls in constrained templates to consider only the overloads that were used to satisfy a constraint as viable candidates. We will possibly revisit the proposal in Kona, as we need to decide the fate of this change before C++20 ships.


The merged Modules proposal, P1103R1 was approved, with a bunch of fixes, including

The global module fragment was not removed, and the paper on retiring pernicious language constructs in module contexts was rejected.

The plan has been for quite some time to wait until Kona before moving Modules, so as to give implementers more time to gain implementation experience.


We discussed P1063R1, Core Coroutines. Evolution, again, still, has consensus (but far from unanimity) to move the merge of the Coroutines TS forward.

Aggregate initialization

The proposal to allow paren-initializing aggregates, P0960, was approved.


The change to allow preconditions and postconditions to use private mambers, P1289R0, was approved.

We discussed UB and optimizations at quite some length; the work on that problem is ongoing, and we'll see more in Kona.

Some constexpr extensions

Template argument deduction

We approved fixes that allow CTAD on aggregates, alias templates, and using inherited constructors.

All Your Spaceships Are Belong to Us

The papers P1185 and P1186 were approved. We expect further discussion on spaceship in Kona.

There was no consensus on making comparison operators chain, nor was there encouragement for further work in that area.

Structured bindings

We discussed removing the need for tuple_element and allowing explicit typing of bindings. There was no consensus for either; Pattern Matching can solve the latter problem.

Defaulted special member functions and noexcept

We approved P1286, which changes noexcept on defaulted special member functions to no longer require the noexcept-spec to match what would've been implicitly generated.

Guaranteed constant initialization for non-constexpr variables

We discussed P1143, Adding the [[constinit]] attribute, and we expect to see a revision in Kona. The current guidance is for a keyword instead of an attribute.


Deprecating volatile was discussed; a revised proposal is expected for Kona.

P1161, Deprecate uses of the comma operator in subscripting expressions, was approved. This paves the way to multi-argument subscripting. We didn't approve making that possible yet, but the deprecation is approved.