error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:21:27
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |         let _f = to_fn(|| x = 42);
   |                  ----- -- ^^^^^^ cannot assign
   |                  |     |
   |                  |     in this closure
   |                  expects `Fn` instead of `FnMut`

error[E0596]: cannot borrow `y` as mutable, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:24:31
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |         let _g = to_fn(|| set(&mut y));
   |                  ----- --     ^^^^^^ cannot borrow as mutable
   |                  |     |
   |                  |     in this closure
   |                  expects `Fn` instead of `FnMut`

error[E0594]: cannot assign to `z`, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:29:22
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |             to_fn(|| z = 42);
   |             ----- -- ^^^^^^ cannot assign
   |             |     |
   |             |     in this closure
   |             expects `Fn` instead of `FnMut`

error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:36:32
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |         let _f = to_fn(move || x = 42);
   |                  ----- ------- ^^^^^^ cannot assign
   |                  |     |
   |                  |     in this closure
   |                  expects `Fn` instead of `FnMut`

error[E0596]: cannot borrow `y` as mutable, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:39:36
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |         let _g = to_fn(move || set(&mut y));
   |                  ----- -------     ^^^^^^ cannot borrow as mutable
   |                  |     |
   |                  |     in this closure
   |                  expects `Fn` instead of `FnMut`

error[E0594]: cannot assign to `z`, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:44:27
   |
LL | fn to_fn<A: std::marker::Tuple, F: Fn<A>>(f: F) -> F {
   |                                              - change this to accept `FnMut` instead of `Fn`
...
LL |             to_fn(move || z = 42);
   |             ----- ------- ^^^^^^ cannot assign
   |             |     |
   |             |     in this closure
   |             expects `Fn` instead of `FnMut`

error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
  --> $DIR/borrow-immutable-upvar-mutation.rs:53:9
   |
LL | fn foo() -> Box<dyn Fn() -> usize> {
   |    ---      ---------------------- change this to return `FnMut` instead of `Fn`
LL |     let mut x = 0;
LL |     Box::new(move || {
   |              ------- in this closure
LL |         x += 1;
   |         ^^^^^^ cannot assign

error: aborting due to 7 previous errors

Some errors have detailed explanations: E0594, E0596.
For more information about an error, try `rustc --explain E0594`.