On Thursday, 6 December 2018 at 02:14:12 UTC, Neia Neutuladh
wrote:
> However, that would also force druntime to include formatting
> code that it currently lacks.

Not necessarily. There is precedent in the language for a
built-in feature actually lowering to a Phobos call: the **
operator is translated to std.math.pow.

The interpolate thing could very well be translated to a call to
std.conv.text.