Overriding to!string on enum types

[monarch_dodra via Digitalmars-d-learn]

On Tuesday, 2 September 2014 at 12:54:55 UTC, Nordlöw wrote:
> Is it possible to override the behaviour of to!string(x) when x 
> is an enum. I'm asking because this
>
> enum CxxRefQualifier
> {
>     none,
>     normalRef,
>     rvalueRef
> }
>
> string toString(CxxRefQualifier refQ) @safe pure nothrow
> {
>     final switch (refQ)
>     {
>         case CxxRefQualifier.none: return "";
>         case CxxRefQualifier.normalRef: return "&";
>         case CxxRefQualifier.rvalueRef: return "&&";
>     }
> }
>
> doesn't affect behaviour of to!string(x) when x is an instance 
> of CxxRefQualifier.

That won't work, because your "toString" is a free function. The 
module system doesn't allow this kind of "Koenig lookup"-like 
hijack. The only reason it allows for things like front/popFront 
and arrays, is that the other modules import std.array, and are 
"aware" of the functions. This is not true for user defined 
types. This may or may not be a feature :)

Unless we allow defining "enum-member functions", AFAIK, it is 
impossible to override the printing behavior for enums... short 
of injecting your own modules in std.format/std.conv. Or to have 
a parameter "moduleLookup" in said template functions.