Weird error message when returning an &'r T

[TethysSvensson]

This program causes an internal compiler error:

fn new<T>() -> &'static T {
  fail!("placeholder")
}

fn main() {
  let &v = new();
}

I get this error, when compiling it:

error: internal compiler error: ty_region() invoked on in appropriate ty: &ty_err

• The problem disappears, if I force the type of v.
• A more reasonable error message appears if I write let v = new(); instead.
• It remains, if I replace the signature with fn new<'r, T>() -> &'r T.
• It also remain if I replace the type signature with fn new<T>() -> Option<&'static T> and alter main accordingly.

[eddyb]

My guess would be that the ICE happens while trying to format the actual error. IMO, &ty_err should have a valid lifetime, since it's just &T with T = ty_err.