I would definitely side with it being okay. I like how string are modeled, but it doesn't mean it isn't painful sometimes. Making some common string operations

I would definitely side with it being okay. I like how string are modeled, but it doesn't mean it isn't painful sometimes. Making some common string operations like &str + &str defined but linted is a good balance of ergonomics and efficiency (that'd be a rare bottleneck, but the lint would make it visible).