error[E0631]: type mismatch in function arguments
  --> $DIR/suggest-option-asderef.rs:25:52
   |
LL | fn takes_str(_: &str) -> Option<()> {
   | ----------------------------------- found signature defined here
...
LL |     let _: Option<()> = produces_string().and_then(takes_str);
   |                                           -------- ^^^^^^^^^ expected due to this
   |                                           |
   |                                           required by a bound introduced by this call
   |
   = note: expected function signature `fn(String) -> _`
              found function signature `for<'a> fn(&'a str) -> _`
note: required by a bound in `Option::<T>::and_then`
  --> $SRC_DIR/core/src/option.rs:LL:COL
help: call `Option::as_deref()` first
   |
LL |     let _: Option<()> = produces_string().as_deref().and_then(takes_str);
   |                                          +++++++++++

error[E0631]: type mismatch in function arguments
  --> $DIR/suggest-option-asderef.rs:28:55
   |
LL | fn takes_str(_: &str) -> Option<()> {
   | ----------------------------------- found signature defined here
...
LL |     let _: Option<Option<()>> = produces_string().map(takes_str);
   |                                                   --- ^^^^^^^^^ expected due to this
   |                                                   |
   |                                                   required by a bound introduced by this call
   |
   = note: expected function signature `fn(String) -> _`
              found function signature `for<'a> fn(&'a str) -> _`
note: required by a bound in `Option::<T>::map`
  --> $SRC_DIR/core/src/option.rs:LL:COL
help: call `Option::as_deref()` first
   |
LL |     let _: Option<Option<()>> = produces_string().as_deref().map(takes_str);
   |                                                  +++++++++++

error[E0631]: type mismatch in function arguments
  --> $DIR/suggest-option-asderef.rs:31:55
   |
LL | fn takes_str_mut(_: &mut str) -> Option<()> {
   | ------------------------------------------- found signature defined here
...
LL |     let _: Option<Option<()>> = produces_string().map(takes_str_mut);
   |                                                   --- ^^^^^^^^^^^^^ expected due to this
   |                                                   |
   |                                                   required by a bound introduced by this call
   |
   = note: expected function signature `fn(String) -> _`
              found function signature `for<'a> fn(&'a mut str) -> _`
note: required by a bound in `Option::<T>::map`
  --> $SRC_DIR/core/src/option.rs:LL:COL
help: call `Option::as_deref_mut()` first
   |
LL |     let _: Option<Option<()>> = produces_string().as_deref_mut().map(takes_str_mut);
   |                                                  +++++++++++++++

error[E0631]: type mismatch in function arguments
  --> $DIR/suggest-option-asderef.rs:36:40
   |
LL | fn generic_ref<T>(_: &T) -> Option<()> {
   | -------------------------------------- found signature defined here
...
LL |     let _ = produces_string().and_then(generic_ref);
   |                               -------- ^^^^^^^^^^^ expected due to this
   |                               |
   |                               required by a bound introduced by this call
   |
   = note: expected function signature `fn(String) -> _`
              found function signature `for<'a> fn(&'a _) -> _`
note: required by a bound in `Option::<T>::and_then`
  --> $SRC_DIR/core/src/option.rs:LL:COL
help: consider adjusting the signature so it does not borrow its argument
   |
LL - fn generic_ref<T>(_: &T) -> Option<()> {
LL + fn generic_ref<T>(_: T) -> Option<()> {
   |
help: call `Option::as_deref()` first
   |
LL |     let _ = produces_string().as_deref().and_then(generic_ref);
   |                              +++++++++++

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0631`.