error[E0308]: mismatched types
  --> $DIR/issue-113354.rs:3:24
   |
LL |     let _ = || { while Some(_) = Some(1) { } };
   |                        ^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
   |
help: consider adding `let`
   |
LL |     let _ = || { while let Some(_) = Some(1) { } };
   |                        +++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.