Hello,
I would suggest to add a "regex literal" type to make ensuring that a string data matches a pattern at assigment.

As the literal string feature has been added in the latest release, i found very convenient to type my variables with, e.g. for typing my react props (size : "small"| "big" )... On the same idea, it could be convenient to be able to type a variable with a pattern.

Example :

    var myString : /\d{3}.*\d{2}/;
    myString="555hhhhh44" ; //correct
    myString="55dsds5dss4"; //error

In react it could be vey useful for defining a react prop like phone numbers, emails, dates, ...

regards
Xavier