> I was very surprised when Jeremy Siek first showed my the compile-time if that later became std::conditional, but I had aimed for generalty (and gotten Turing completeness modulo translation limits). I opposed restrictions to C++ immediately when Erwin Unruh presented what is widly believed to be the first template metaprogram to the ISO Standards committee's evolution working group. To kill template-metaprogramming, all I would have had to do was to say nothing

Discovered by users after being created as a side effect of the power of the template expansion defined by the committee, and then kept thereafter.

It was a side effect yes, but it’s not like a working compiler was released and a users found this.

It was discovered during the design phase of templates by people involved in standardisation process.

And it sounds like leaving it in was even a contentious point that others were against.

So far from an accident, it was a feature that was extensively discussed and intentionally supported.