On Tuesday, 3 October 2017 at 19:25:32 UTC, Walter Bright wrote:
This is specifically designed to prevent nasty surprises. C++
has a big problem with ADL in that overloading is not
encapsulated and any #included header can inadvertently add
more overloads that may be entirely unrelated. Any .h can crack
open any namespace and insert more overloads into it. It's
completely unhygienic and uncontrollable.
As for the specific example you gave, I get:
a.d(3): Error: no property 'front' for type 'int[]'
a.d(4): Error: no property 'save' for type 'int[]'
b.d(8): Error: template instance a.sum!(int[]) error
instantiating
But you can't deny our solution eats expressive power: If you
don't want to change code you're importing, you have to write a
wrapper type for int[] here. Alias this helps, but because save()
and slicing operators have to return the type of this, there's
still manual work to do if you want Phobos algorithms to utilize
it's random access.
It may be that ADL or something similar would cause too much
trouble to be worth it, don't know about that. But what I'm
saying that we definitely have a considerable problem here and it
would solve it.
