On Thursday, 31 January 2019 at 02:41:00 UTC, Steven
Schveighoffer wrote:
Apples and oranges :)
ReturnType!(produceS!(42)) is a TYPE, not a variable. When you
apply the brackets, it's not calling your opindex, but rather
changing it to an array. So let's make it clearer by saying:
alias T = ReturnType!(produceS!(42));
So now, your assert becomes:
static assert(isInputRange!(T[]));
Which, is not coming up as a valid range, because you can't
copy the front value (this(this) is disabled).
In the other expression, you are first calling the index
operator on an instance of the type, which returns a DIFFERENT
type, and then asserting the type of that is an input range.
The equivalent (still using T) is:
static assert(isInputRange!(typeof(T.init[])));
replacing T with the original is:
static
assert(isInputRange!(typeof(ReturnType!(produceS!(42)).init[])));
-Steve
Yeah... maybe, it was too much code for a single day yesterday...
:P
