error[E0282]: type annotations needed for `Option<T>`
  --> $DIR/unboxed-closures-failed-recursive-fn-2.rs:16:32
   |
LL |     let mut closure0 = None;
   |         ------------ consider giving `closure0` the explicit type `Option<T>`, with the type parameters specified
...
LL |                         return c();
   |                                ^^^ cannot infer type
   |
   = note: type must be known at this point

error: aborting due to previous error

For more information about this error, try `rustc --explain E0282`.