mozilla/rust — pull request #11773 by huonw (2014-01-24 13:04:29+00:00)
Title: Add a lint for non-exported local types in visible type signatures.

Except for traits, to allow them to be used as closed type-classes and/or PIMPL-style polymorphic trait objects

```rust
struct Private;
pub fn warning(x: Private) {}

trait Priv {}
pub fn ok() {}
```