Passing &Foo for newtype struct Foo

[luqmana]

It seems like this was broken as a result of the recent change to make newtypes structs immediate in certain cases.

struct TestNode(@int);

fn mm(_x: &TestNode) {}

fn main() {
    let x = &TestNode(@21);
    mm(x);
}

% rustc foo.rs
error: internal compiler error: drop_ty_immediate: non-box ty

[metajack]

This was found in Servo's rust-css tests.

nominating production ready

[catamorphism]

Accepted for production-ready

[thestinger]

Closing as a duplicate of #9446. I have a fix in the pipeline for this (#9643).