makeIndex not working

[bearophile]

Johann MacDonagh:

> I'm confused, what am I doing wrong here?

I think that Phobos needs way more&better unittests.

I think the error you receive reduces to this:

import std.range: isForwardRange;

void foo(R)(R r) if (isForwardRange!R) {}

void main() {
     immutable arr = [1, 2];
     foo(arr);
}

Bye,
bearophile