[pcwalton]

> If the intention of the language is to "properly" work with a lot of strings (and it should be) it would be good not to have glaring inefficiencies? Wouldn't it be a good optimization to have the free routine check if the pointer is inside of the static area and then not do anything.

You can implement that yourself, by using an enum for example or by using a custom smart pointer. The moment you start adding more magic to "free" beyond "call free" you become less low level of a language.

[acqq]

Can I ask in the language if the address points to the item constructed by the compiler in the static area?

The thing I miss most in C is the possibility for the some kind of"introspection" -- reaching out to the info that the compiler or linker has to know anyway. As far as I know D language is very good for such things.

[dbaupp]

You can use lifetimes to enforce that a certain thing is static data, and combined with an enum, you get the best of both worlds: compile-time constants require no allocations, but still flexible enough to allow run-time construction:

  enum StringRef {
      Static(&'static str),
      Owned(~str)
  }

and then `error` would take `StringRef` and be called like:

  self.error(Static("trailing characters"))
  // or
  self.error(Owned(fmt!("%u trailing characters", count)))

(There was even a pull request that added this and the corresponding one for vectors to the stdlib, but it didn't landed (yet): https://github.com/mozilla/rust/pull/7599)

[pcwalton]

> Ca I ask in the language if the address points to the item constructed by the compiler in the static area?

It'd require some OS-specific magic. But you could probably do it.