Cannot call a Box<FnBox(_)> with a reference parameter

[KyleMayes]

#![feature(core)]

use std::boxed::{FnBox};

type Closure = Box<FnBox(i32)>;
type ClosureReference = Box<FnBox(&i32)>;

fn works(closure: Closure) {
    closure(42);
}

fn does_not_work(closure: ClosureReference) {
    closure(&42); // <- the error
}

fn main() {
    works(Box::new(|integer| println!("{}", integer)));

    does_not_work(Box::new(|integer: &i32| println!("{}", integer)));
}

Rust Playpen

Error

<anon>:13:5: 13:17 error: expected function, found `Box<for<'r> alloc::boxed::FnBox<(&'r i32,), Output=()>>`
<anon>:13     closure(&42); // <- the error
              ^~~~~~~~~~~~

On a semi-related note, the closure argument type is inferred for the Closure passed to works but not for the ClosureReference passed to does_not_work, but I think this is likely an extension of #24680.

Meta

rustc 1.2.0-nightly (c23a9d42e 2015-05-17) (built 2015-05-17)
binary: rustc
commit-hash: c23a9d42ea082830593a73d25821842baf9ccf33
commit-date: 2015-05-17
build-date: 2015-05-17
host: x86_64-pc-windows-gnu
release: 1.2.0-nightly

[Thiez]

Strangely, the function does work if you change the body to

closure.call_box((&42,)); // <- no longer an error

Looks like the sugar confuses the compiler?

[abonander]

This is still a problem in the 1.7 nightly.

[shepmaster]

This is still a problem in the Rust 1.26 nightly.

[smcmurray]

This is still a problem in Rust 1.28 nightly.

[KyleMayes]

It seems to work now.
Plus, FnBox is no longer needed in the latest stable version.