[rzmmm]

Is there benefit of using this branded type over just encapsulating the raw string in a private variable in closure or class? This feels a bit like forced nominal typing. The Email type doesn't have to be a string, it can be encapsulated so that invalid Emails are not representable.

[iainmerrick]

The main advantage of branding is that it’s a zero-cost abstraction -- the boilerplate vanishes at runtime. Just using a string instead of a containing object can give you a lighter-weight runtime.