Now that's a DIP that could use some love

[Andrei Alexandrescu]

On 9/17/20 5:39 PM, Jonathan M Davis wrote:
> private traits in the public constraints. But even then, the actual template
> constraints are pretty short, and the traits used are descriptive enough
> that I wouldn't expect them to be hard to understand or that repeating them
> in English text would help much.

Here goes, straight from the horse's mouth 
(https://dlang.org/library/std/algorithm/iteration/each.each.html):

Flag!"each" each(Range) (
   Range r
)
if (!isForeachIterable!Range && (isRangeIterable!Range || 
__traits(compiles, typeof(r.front).length)));

Flag!"each" each(Iterable) (
   auto ref Iterable r
)
if (isForeachIterable!Iterable || __traits(compiles, 
Parameters!(Parameters!(r.opApply))));

Compare to "`each` requires type MyRange to work with foreach".

Let's see:

"pretty short" .................................................. FAIL
"descriptive enough" ............................................ FAIL
"wouldn't expect them to be hard to understand"  ................ FAIL
"repeating them in English text wouldn't help much" ............. FAIL