d关键字作为构字段

原文
基于opDispatch+__traits(getMember)的库解决方案.

template FieldOfKeyword(string[2][] keywordFieldPairs)
{
    template opDispatch(string member)
    {
        static foreach (pair; keywordFieldPairs)
            static if (member == pair[0])
                mixin("alias opDispatch = ", pair[1], ";" );
    }
}
///
unittest
{
    struct Foo
    {
        mixin FieldOfKeyword!([["scope", "scope_"],["class", "class_"]]);
        string scope_;
        string class_;
    }

    Foo foo;
    __traits(getMember, foo, "scope") = "The Universe";
    assert(__traits(getMember, foo, "scope") == "The Universe");
    __traits(getMember, foo, "class") = "Atom";
    assert(__traits(getMember, foo, "class") == "Atom");
}