rust - How can I concatenate something to the front of a string? -


i keep getting error "use of moved value".

let mut s = "s".to_string(); s = s + &s;

think + desugars to:

s = s.add(&s);

now add from add trait , this:

fn add(self: string, rhs: &str) -> string;

the use of self means taking ownership of string; can’t pass reference second argument, because isn’t yours more.

you might think it’d ok doing this, it’s not; whole class unsound, constituting mutable aliasing—both mutable , immutable reference same thing existing @ same time. specific case, 1 way imagine going wrong if permitted if string pushing reallocate string; rhs conceivably pointing non-existent memory when went use it.


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