RefsSpans.cs

    // edit: hmmm, actually I can see cases where this would fail epicly, so
    // probably best to ignore me here - for example:
    // var span = GetSomeType().GetTags() - the SomeType value has now left the
    // logical stack-frame, so our ref is undefined. It *could* perhaps
    // work in the context of a "ref SomeType", but again: hard scoping

    // so yeah, I'm mad - ignore me and ignore this!

===========================


    // some crazy ideas about "ref T" and "Span<T>" in
    // the context of "fixed" fields; I *think* I can
    // emulate all of this at runtime using Unsafe and
    // manually measuring the offset at runtime, and using
    // hacks, but I *think* this is all actually pretty
    // legal to work *without* all that hackery...
    unsafe struct SomeType
    {
        private int _id;
        // moar fields, etc
        private fixed int _tags[10];
        // moar fields, etc

        // I **think** it is legit to talk about a
        // ref directly into the fixed block (compiler
        // doesn't allow it, though)
        public ref int GetTag(int index)
        {
            // not shown, check range
            return ref _tags[index];
        }
        // and by extension, if we can get a ref to that,
        // and if we had the Span<T> semantics that allow
        // us to pass *in* a ref T, then we could do:
        public Span<int> GetTags()
        {
            // this "ref T, int" constructor doesn't
            // exist, note
            return new Span<int>(ref _tags[0], 10);
        }
        // although (and this is a stretch goal) the *compiler*
        // already knows the length... how crazy is this?
        public Span<int> GetTagsWithModestCompilerHelp()
        {
            // this is not a pre-existing legal "sizeof" usage,
            // just spitballing here...
            return new Span<int>(ref _tags[0], sizeof(_tags));
        }
        // or going fully crazy
        public Span<int> GetTagsWithEpicCompilerHelp()
        {
            // lots of implicit stuff here...
            return _tags;
        }
    }