Feedback on Átila's Vision for D

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On Tuesday, 15 October 2019 at 13:09:15 UTC, Mike Parker wrote:
> This thread is for general feedback and discussion regarding 
> Átila's blog post on his vision for D's future.
>
> https://dlang.org/blog/2019/10/15/my-vision-of-ds-future/

"Instead of disparate ways of getting things done with fragmented 
APIs (__traits, std.traits, custom code), I’d like for there to 
be a library that centralizes all reflection needs with a great 
API."

Yes, 100% agreed. Another benefit of having one unified API is 
that it's easier to paper over the weird differences between 
various methods of doing reflection.

Ex:

is(typeof({ return x + x; })) vs __traits(compiles, { return x + 
x; })

__traits(identifier, x) vs. x.stringof (x.stringof will fail to 
compile if x is a function with at least 1 parameter, but 
__traits(identifier) works)

I'm curious, is Atila's work on this building on Andrei's? I 
remember him talking about his work on a reflection library at a 
recent DConf (I think it was last year's).

"String interpolation"

I've been finding a lot of places in my code where string 
interpolation would make it much more readable. It would be nice 
to be able to use them in invariants, in contracts, out 
contracts, and assert statements, e.g.:

struct OneIndexedArray(T)
{
     T[] store;

     T opIndex(size_t i)
     in (i > 0, "Index $i is out of range for 
$(OneIndexedArray.stringof)")
     in (i < store.length,
          "Index is out of range for $(OneIndexedArray.stringof) 
(length: $(store.length), index: $i")
     {
         ...
     }
}

It's a real pain having to stick a 
`.format(OneIndexedArray.stringof, store.length, i)` at the end 
of the message.

pragma(msg) get's this right, presumably because it's a compile 
time-only construct.