On Tuesday, 25 August 2020 at 12:50:35 UTC, Steven Schveighoffer
wrote:
The situation is still confusing though. If only
'std.range.ElementType' is imported, a static array does not
have a 'front' member, but ElementType still gets the correct
type. (This is where the documentation says it'll return void.)
You are maybe thinking of how C works? D imports are different,
the code is defined the same no matter how it is imported.
*your* module cannot see std.range.primitives.front, but the
range module itself can see that UFCS function.
This is a good characteristic. But the reason it surprised me was
that I expected to be able to manually expand the ElementType (or
ElementEncodingType) template see the results of the expressions
it uses.
template ElementType(R)
{
static if (is(typeof(R.init.front.init) T))
alias ElementType = T;
else
alias ElementType = void;
}
So, yes, I was expecting this to behave like an inline code
expansion.
Yesterday I was doing that for 'hasSlicing', which has a more
complicated set of tests. I wanted to see exactly which
expression in 'hasSlicing' was causing it to return false for a
struct I wrote. (Turned out to be a test for 'length'.)
I'll have to be more careful about this.
