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#![feature(unboxed_closures, tuple_trait)]
// Tests that we can't assign to or mutably borrow upvars from `Fn`
// closures (issue #17780)
fn set(x: &mut usize) {
*x = 5;
}
fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
f
}
fn to_fn_mut<A: std::marker::Tuple, F: FnMut<A>>(f: F) -> F {
f
}
fn main() {
// By-ref captures
{
let mut x = 0;
let _f = to_fn(|| x = 42); //~ ERROR cannot assign
let mut y = 0;
let _g = to_fn(|| set(&mut y)); //~ ERROR cannot borrow
let mut z = 0;
let _h = to_fn_mut(|| {
set(&mut z);
to_fn(|| z = 42); //~ ERROR cannot assign
});
}
// By-value captures
{
let mut x = 0;
let _f = to_fn(move || x = 42); //~ ERROR cannot assign
let mut y = 0;
let _g = to_fn(move || set(&mut y)); //~ ERROR cannot borrow
let mut z = 0;
let _h = to_fn_mut(move || {
set(&mut z);
to_fn(move || z = 42);
//~^ ERROR cannot assign
});
}
}
fn foo() -> Box<dyn Fn() -> usize> {
let mut x = 0;
Box::new(move || {
x += 1; //~ ERROR cannot assign
x
})
}
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