Re: [boost] [GSoC] [Boost.Hana] Formal review request

Subject: Re: [boost] [GSoC] [Boost.Hana] Formal review request
From: pfultz2 (pfultz2_at_[hidden])
Date: 2014-08-01 07:27:08

> I am therefore rather sticking with static_assert to enforce constraints
> with friendly error messages for the time being until Concepts Lite are
> available as TS or part of the standard. 

Using static_assert to enforce constraints can become problematic when used
with concept predicates. That is because static_assert causes a hard error.
So, when its combined with function overloading, I would get a friendly
error
message, rather than the compiler calling the alternative function. This can
be workaround by specializing the trait, which is possible with Tick, but
not
with `concept bool`.

A lot of these problems will start showing up as more people start using
concept predicate in C++11 and beyond. The difference between a hard error
and
template constraint is not really fully understood or utilized by many
libraries. So to be prepared for the future you should use enable_if which
is
a template constraint, instead of static_assert which just produces an
error.
Most modern compilers will produce nice friendly messages for enable_if.

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