On Saturday, 11 January 2014 at 05:45:41 UTC, H. S. Teoh wrote:
It's not just about custom error messages; it's about picking
up a
particular template signature even when you don't have an
implementation
for it, because logically speaking, your set of overloads
*should* pick
up all such instantiations to begin with. This is why I
differentiated
between the scope of a template, vs. the actual available
overloads.
With sig constraints, you're declining instantiations that
don't satisfy
certain conditions; I'm arguing that sometimes you *want* to
accept
instantiations that you currently don't implement (yet),
because it
falls under the logical scope of what you intend to handle; you
just
haven't gotten around to actually implementing it yet.
There is nothing stopping you from writing constraints that
accept currently unimplemented instantiations. There is no
difference here with the two approaches.
