[Proposal] Custom literals for string-based objects.

[orthoxerox]

A string literal or a raw string literal can be prepended by an identifier:

var element = xml@"<foo>
    <bar/>
</foo>";
var pattern = r"^[[:alpha:]]+$";

This is automatically rewritten to a class constructor or a static function invocation that has a matching attribute:

[StringLiteral("r")]
public class Regex
{
    public Regex(string pattern) //A constructor that can accept a single string argument is required.
    { ... }

    [StringLiteral("ri")] [EditorBrowsable(EditorBrowsableState.Never)]
    public static Regex CreateIgnoreCase(string pattern)
    { ... }
}

If there are two StringLiteral attributes with the same parameter in scope, it is a compilation error.

Potential use cases: simplifying the syntax for regexes, constant byte arrays or UTF-8 encoded strings. If compile-time metaprogramming is ever implemented in C#, the same syntax can be reused for safe XML literals, like in VB.

[alrz]

Dup of #4971

[dsaf]

Actually, it's a duplicate of #263. #4971 was a duplicate itself. I am pretty sure we will see more of these.

[gafter]

You can already do this using an extension method:

var element = @"<foo>
    <bar/>
</foo>".Xml();
var pattern = "^[[:alpha:]]+$".Regex();