d改进翻译

原文
结构可以是函子:

private @safe struct TranslatableStringPlural
{
    string _str, _strpl;
    this(string s1, string s2) { // 必须的!
        _str = s1;
        _strpl = s2;
    }
    string opCall(int n)
    {
        auto fmt = ngettext(_str, _strpl, n);
        if (countFormatSpecifiers(fmt) == 0)
            // 改进该行.
            return ()@trusted{ return fromStringz(&(format(fmt~"\0%s", n)[0])); }();
        return format(fmt, n);
    }
}

现在,变成:

private @safe struct Strplusarg {
    this(string s) {
        fmt = s;
        auto fs = countFormatSpecifiers(fmt);
//修复这句.
        assert(fs==0||fs==1,"无效");
        hasArg = fs == 1;
    }
    string fmt;
    bool hasArg;
}

private @safe struct TranslatableStringPlural
{
    //...前略
    string opCall(int n)
    {
        auto f = n == 1 ? _str : _strpl;
        return f.hasArg ? format(f.fmt, n) : f.fmt;
    }
}

原代码:

@safe: private:
int countFormatSpecifiers(string fmt) pure
{
    int count = 0;
    auto f = FormatSpec!char(fmt);
    if (!__ctfe)
    {//有ctfe
        while (f.writeUpToNextSpec(nullSink))
            count++;
    } else {
        auto a = appender!string; 
        while (f.writeUpToNextSpec(a))
            count++;
    }
    return count;
}

修复为:

@safe: private:
int countFormatSpecifiers(string fmt) pure
{
    static void ns(const(char)[] arr) {} 
// 最简输出区间.
    auto nullSink = &ns;
    int count = 0;
    auto f = FormatSpec!char(fmt);
    while (f.writeUpToNextSpec(nullSink))
        count++;
    return count;
}