error[E0631]: type mismatch in closure arguments
  --> $DIR/issue-36053-2.rs:7:32
   |
LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
   |                                ^^^^^^ ---------
   |                                |      |   |
   |                                |      |   help: consider borrowing the argument: `&&str`
   |                                |      found signature defined here
   |                                expected due to this
   |
   = note: expected closure signature `for<'a> fn(&'a &str) -> _`
              found closure signature `for<'a> fn(&'a str) -> _`
note: required by a bound in `filter`
  --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL

error[E0599]: the method `count` exists for struct `Filter<Fuse<Once<&str>>, [closure@issue-36053-2.rs:7:39]>`, but its trait bounds were not satisfied
  --> $DIR/issue-36053-2.rs:7:55
   |
LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
   |                                       ---------       ^^^^^ method cannot be called due to unsatisfied trait bounds
   |                                       |
   |                                       doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool`
   |                                       doesn't satisfy `_: FnMut<(&&str,)>`
  --> $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
   |
   = note: doesn't satisfy `_: Iterator`
   |
   = note: the following trait bounds were not satisfied:
           `<[closure@$DIR/issue-36053-2.rs:7:39: 7:48] as FnOnce<(&&str,)>>::Output = bool`
           which is required by `Filter<Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:48]>: Iterator`
           `[closure@$DIR/issue-36053-2.rs:7:39: 7:48]: FnMut<(&&str,)>`
           which is required by `Filter<Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:48]>: Iterator`
           `Filter<Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:48]>: Iterator`
           which is required by `&mut Filter<Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:7:39: 7:48]>: Iterator`

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0599, E0631.
For more information about an error, try `rustc --explain E0599`.