error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:24:24
   |
LL |     let c1 = to_fn_mut(|| x = 4);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^ - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:35:24
   |
LL |     let c1 = to_fn_mut(|| set(&mut x));
   |                        --          - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^          - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:42:24
   |
LL |     let c1 = to_fn_mut(|| x = 5);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^          - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:49:24
   |
LL |     let c1 = to_fn_mut(|| x = 5);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
   |                        ^^                                  - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
...
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:61:24
   |
LL |     let c1 = to_fn_mut(|| set(&mut *x.f));
   |                        --           - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut *x.f));
   |                        ^^           - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
...
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:24:24
   |
LL |     let c1 = to_fn_mut(|| x = 4);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^ - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:35:24
   |
LL |     let c1 = to_fn_mut(|| set(&mut x));
   |                        --          - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^          - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:42:24
   |
LL |     let c1 = to_fn_mut(|| x = 5);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^          - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
LL |     //~| ERROR cannot borrow `x` as mutable more than once
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:49:24
   |
LL |     let c1 = to_fn_mut(|| x = 5);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
   |                        ^^                                  - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
...
LL | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:61:24
   |
LL |     let c1 = to_fn_mut(|| set(&mut *x.f));
   |                        --           - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
LL |     let c2 = to_fn_mut(|| set(&mut *x.f));
   |                        ^^           - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
...
LL | }
   | - first borrow ends here

error: aborting due to 10 previous errors

If you want more information on this error, try using "rustc --explain E0499"