error[E0599]: no method named `closure` found for type `Obj<[closure@$DIR/issue-18343.rs:16:28: 16:33]>` in the current scope
  --> $DIR/issue-18343.rs:17:7
   |
11 | struct Obj<F> where F: FnMut() -> u32 {
   | ------------------------------------- method `closure` not found for this
...
17 |     o.closure();
   |       ^^^^^^^ field, not a method
   |
   = help: use `(o.closure)(...)` if you meant to call the function stored in the `closure` field

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0599"