Expressing range constraints in CNF form

[Nick Treleaven via Digitalmars-d]

On Sunday, 11 June 2017 at 00:28:58 UTC, Andrei Alexandrescu 
wrote:
> https://github.com/dlang/phobos/pull/5461
>
> There's many good advantages to this. The immediate one is the 
> constraint is better structured and easier to understand. Then, 
> the compiler can print the exact clause that failed, which 
> improves the precision and quality of the error message.

Great!

> // Also possible (no change to the language)
> enum bool isInputRange(R) =
>     is(typeof((ref R r) => r)) && msg("must be copyable")
>     && is(ReturnType!((R r) => r.empty) == bool) && msg("must 
> support bool empty")
>     && is(typeof(lvalueOf!R.front)) && msg("must support front")
>     && is(typeof(lvalueOf!R.popFront)) && msg("must support 
> back");

I'm not getting how this works.