Error while generate DNA with uniform()

[Salih Dincer]

On Saturday, 3 September 2022 at 21:09:09 UTC, Ali Çehreli wrote:
> Salih had asked:
>
> >> Can we solve this issue with our own `generate()` structure?
>
> Yes, I did the following to determine that adding Unqual was a 
> solution:
>
> - Copy generate() functions to your source file,
>
> - Copy the Generator struct to your source file,
>
> - Edit the definition of Generator's elem_ member as I hinted 
> in the bug.

But the bug may be in the templates, not in the structure. Maybe `
template functionTypeOf(alias func)`

For example:

```d
auto gen(alias fun)() {
     auto gen = Gen!fun();
     gen.popFront();
     return gen;
}

struct Gen(alias fn)
{
   import std.traits:
   ReturnType!fn func;

   enum empty = false;
   auto front() { return func; }
   void popFront() { func = fn(); }
}

unittest
{
   import std.random : uniform;
   import std.range : takeExactly;

   enum E {
     O = '0', P, Q, R, S, T, U, V, W, X,
     A = 'A', B, C, D, E, F
   }
   auto range = gen!(function char()  =>
                    uniform!"[]"(E.min, E.max))
                    .takeExactly(15);
   assert(range.to!long(15) < long.max);
}
```
SDB at 79