Daniel Murphy:
This doesn't need a lot of text to explain either: "when
possible, the compiler will check preconditions at compile time"
What defines "possible"? A compiler switch that allows to define
the amount of compile time?
I feel like you're confusing this pull request with another
enhancement. The discussion should be about whether this exact
feature is worthwhile, not if some other feature would solve
some other problems.
The comparison of the two ideas is useful, because they try to
solve the same problem.
Do you really think the compiler opportunistically checking
preconditions would be a bad thing for D?
I think that adding an undefined, growing, compiled-dependent
list of static checks that can cause unpredictable compilation
times is not a good idea. A more general solution has some
advantages:
- It allows the user to choose what to run at compile-time and
what at run-time;
- You can defined _exactly_ what it does in a book, unlike the
growing list;
- Will not grow in features and implementation complexity as
compilers improve (and I think it's sufficiently simple);
- It's going to be mostly the same in all D compilers;
- It allows to specify and run arbitrary tests in CTFE instead of
a set of predefined by unknown simple tests. So you can use it
for SafeIntegers literals, and many other future and
unpredictable purposes;
- It's explicitly visible in the code, because there is a syntax
to denote such static testing parts in the code.
Implementing a special-cased solution instead of a more general
and principled solution could make the implementation of the
better solution more unlikely :-)
Bye,
bearophile
