Regex is always mutated into uncompilable code

[eNeRGy164]

Describe the bug
I have a simple regex in my code, all mutations are invalid as the constructor is removed in the result.

public bool TestInput(string input)
{
    var regex = new Regex(@"^[0-9]{3,}$");

    return regex.IsMatch(input);
}

Mutations

There are multiple, all causing the same compilation error, but 3 examples:

Regex anchor removal mutation:

-   var regex = new Regex(@"^[0-9]{3,}$");
+   var regex = "^[0-9]{3,}"

Regex greedy quantifier quantity mutation:

-   var regex = new Regex(@"^[0-9]{3,}$");
+   var regex = "^[0-9]{4,}"

Regex character class range modification:

-   var regex = new Regex(@"^[0-9]{3,}$");
+   var regex = "^[0-8]{3,}$"

Tested both with var and explicit type.

Expected behavior
No compilation errors.

Desktop (please complete the following information):

• OS: Windows
• Type of project: .NET
• Framework Version: 9.0
• Stryker Version: 4.5.1