Dear,

When you need to manage various file format and trying to fit as a phobos File it appear below feature could be really interesting.

by example you have a parser you want to construct is from various file type you can grant some methods.

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template isFileType(F)
{
    enum bool isFileType = is(typeof(
    {
        ubyte[] buf;
        F f = void;         // can define a FileType object
        if (f.eof) {}       // can test for end of file
        if (f.isOpen) {}    // can test for opened file
        f.name;             // can invoke name
        f.close();          // can invoke close
        r.write();          // can invoke write()
        r.rawWrite( "" );   // can invoke rawWrite()
        r.rawRead( buf );   // can invoke rawRead()
    }));
}


struct FileType( F ) if( isFileType( F ) )
{
    F _f;
    this( F file ){
        _f = file;
    }

    alias _f this;
}