Module translate_closures

In rust, closures behave like ADTs that implement the FnOnce/FnMut/Fn traits automatically.

Here we convert closures to a struct containing the closure’s state (upvars), along with matching trait impls and fun decls (e.g. a Fn closure will have a trait impl for Fn, FnMut and FnOnce, along with 3 matching method implementations for call, call_mut and call_once).

For example, given the following Rust code:

pub fn test_closure_capture<T: Clone>() {
    let mut v = vec![];
    let mut add = |x: &u32| v.push(*x);
    add(&0);
    add(&1);
}

We generate the equivalent desugared code:

struct {test_closure_capture::closure#0}<'a, T: Clone> (&'a mut Vec<u32>);

// The 'a comes from captured variables, the 'b comes from the closure higher-kinded signature.
impl<'a, 'b, T: Clone> FnMut<(&'b u32,)> for {test_closure_capture::closure#0}<'a, T> {
    fn call_mut<'c>(&'c mut self, arg: (&'b u32,)) {
        self.0.push(*arg.0);
    }
}

impl<'a, 'b, T: Clone> FnOnce<(&'b u32,)> for {test_closure_capture::closure#0}<'a, T> {
    type Output = ();
    ...
}

pub fn test_closure_capture<T: Clone>() {
    let mut v = vec![];
    let mut add = {test_closure_capture::closure#0} (&mut v);
    state.call_mut(&0);
    state.call_mut(&1);
}

Functions

translate_closure_kind