string interpolation fun

[Jonathan Marler]

On Thursday, 13 December 2018 at 16:01:52 UTC, Steven 
Schveighoffer wrote:
> On 12/13/18 10:53 AM, Steven Schveighoffer wrote:
>> void main()
>> {
>>      import std.stdio;
>>      int x = 1;
>>      int y = 2;
>>      auto s = make!(S, i"x: $(y), y: $(x)"); // name the 
>> fields to assign
>>      auto s2 = make!(S, i":$(x), :$(y)"); // use symbol name 
>> as field name
>>      auto s3 = make!(S, i"x: $(6), y: $(7)"); // use literals 
>> to assign
>>      writeln(i"$(s), $(s2), $(s3)"); // runtime parameters
>> }
>> 
>> 
>
> Also, this would be a lot less noisy if we didn't need the 
> parens after the $, but the PR doesn't support that (yet?).
>
> -Steve

Very cool use case.

Adding support for the `$foo` case (no parens) would be fairly 
trival, but requires making a decision of what type of grammar 
node/token to use.  We could use the same mechanism that 
templates use, but that would mean that something like $foo.max 
would be $(foo).max instead of $(foo.max) which seems a bit 
unexpected.  That would be a good thing include in the DIP, a 
list of the obvious tokens/grammar nodes we could use and their 
pros/cons.