Why code failed to compile for foo2?

[apz28]

On Tuesday, 14 December 2021 at 05:04:46 UTC, Tejas wrote:
> Is there anything wrong with the answer I posted?
>
> Can you please tell me if there's anything dissatisfactory 
> about it? I feel like it does everything the OP wants.
>
> Also, am I wrong in using `Unconst` over `Unqual`? Isn't 
> `Unqual` overkill if you just want to cast away `const`?

1. A template function should behave as to replace 4 overload 
functions
There is special logic for parameter type (2 vs 4...)

2. Your implementation does not remove 'const' as below
import std.traits : Unconst;
import std.stdio : writeln;

     void foo2(T)(T x) if(is(Unconst!(T) : ulong)) {//You don't 
need Unqual for this
         pragma(msg, T.stringof);
         writeln(x);
     }

     void main()
     {
         import std.math;

         const int s1 = -3;
         int s2 = -2;
         foo2(abs(s1));
         foo2(abs(s2));

         enum byte b1 = 0;
         const byte b2;
         byte b3;
         foo2(b1);
         foo2(b2);
         foo2(b3);
     }
     --Output
     const(int)
     int
     byte
     const(byte)
     3
     2
     0
     0
     0