Pattern matching with UTF-8 String Literals

[tmds]

C# 11 preview blog post includes UTF-8 String Literals, and Pattern matching with spans (specifically: [ReadOnly]Span<char>).

It would be interesting if both can be combined, allowing pattern matching against [ReadOnly]Span<byte>.

For example:

static HttpMethod ParseHttpMethod(ReadOnlySpan<byte> method)
{
    return method switch { 
        "GET"  => HttpMethod.Get, 
        "POST" => HttpMethod.Post, 
...
        _ => HttpVerb.Unknown };
}

This is interesting for use-cases that involve parsing UTF-8.

cc @KathleenDollard

Originally posted by @tmds in #6036

[tmds]

cc @davidfowl

[RikkiGibson]

Moving discussion back to the discussion thread for now. Thanks!