How to use indexers in switch expression?

How to access indexers in switch expression? There is a nice property pattern syntax in switch expressions, but I can't figure out or find any information about using indexers.

Given following code:

var a = "123";
if(a.Length == 3 && a[0] == '1')
    Console.WriteLine("passed");

How do to convert it to switch expression? Matching a.Length is easy, but how to specify a match for a[0] == '1'?

var b = a switch
{
    { Length: 3, this[0]: '1' } => "passed", // CS8918: Identifier or a simple member access expected.
    _ => "error"
};
Console.WriteLine(b);

Fiddle.

One way to do it is by using when statement. It is not as beautiful as property pattern, but can be a workaround:

var b = a switch
{
    { Length: 3 } when a[0] == '1' => "passed",
    _ => "error"
};

Since C# 11 you can use list patterns:

var b = a switch
{
    ['1', _, _] => "passed", // CS8918: Identifier or a simple member access expected.
    _ => "error"
};

Since c# 8.0. You can acheive it with switch expressions:

var a = "123";
var tuple = (a.Length, a[0]);
switch (tuple)
{
	case (3, '1'):
		//do something
		break;
	case (4, '2'):
		//do something
		break;
}

or

string b = (a.Length, a[0]) switch
{
	(3, '1') => "passed",
	(4, '2') => "failed",
	_ => "error"
};

You can find more usage of switch expressions from this documentation (https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/switch-expression)

Edit:
In a case where you need to check a.Length before evaluating a[index].
You can actually check it when creating a new Tuple.

var a = "323";
var index = 5;
char? ch = (a.Length >= index + 1) ? (char?)a[index] : null;
var b = (a.Length, ch) switch
{
    (_, null) => "error",
    (3, '1') => "pass",
    _ => "default"
};
System.Console.WriteLine(b??"");