On Tue, Oct 1, 2019 at 12:56 PM Phil Bouchard via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

[I apologize for my mistakes, I wrote the email very quickly]

2 things here:

1. "constexpr" would ideally need to be treated like a qualifier. This way it could propagate like cv qualifier.

constexpr is not part of the type system, it cannot be treated like qualifier. Given:

constexpr int i = 1;
int const j = 2;

The types of i and j are the same, both int const. There is a proposal (P1045) for constexpr parameters, but there constexpr would work very differently than the way qualifiers work: a constexpr parameter would [have to] behave like a template.

If you want to "propagate" constexpr, you just declare your function constexpr. constexpr is already conditionally constexpr.