Comma operator = broken design

[bearophile]

Timon Gehr:

> These are the occurences of the comma operator in directory 'std':
> 
> return r2.empty ? (r1 = r, true) : false;
> return binaryFun!pred(r.front, e) ? (r.popFront(), true) : false;
> 
> if (f.flPlus)
>      signChar = '+', ++minw;
> else if (f.flSpace)
>      signChar = ' ', ++minw;
> 
> if (std.ascii.toLower(p.front) == 'n' &&
>         (p.popFront(), std.ascii.toLower(p.front) == 'f') &&
>         (p.popFront(), p.empty))
> 
> enforce((p.popFront(), !p.empty && std.ascii.toUpper(p.front) == 'A')
>          && (p.popFront(), !p.empty && std.ascii.toUpper(p.front) == 'N'),
>         new ConvException("error converting input to floating point"));
> 
> if (indexStart != 0)
>      formatValue(w, indexStart, f), put(w, '$');
> 
> if (c == '\"' || c == '\\')
>      put(w, '\\'), put(w, c);
> else
>      put(w, c);
> 
> return (++mi.m_cRefs, cast(HXModule)mi);
> return (++mi.m_cRefs, hModule);
> 
> return
>      c <= 0x7F ? 1
>      : c <= 0x7FF ? 2
>      : c <= 0xFFFF ? 3
>      : c <= 0x10FFFF ? 4
>      : (assert(false), 6);

It's ugly code worth fixing/rewriting. If I see something like that in production code, I always burn it with fire and rewrite it.
Turning such usages of comma operator into syntax errors looks like a general improvement for D.

Bye,
bearophile