error[E0277]: the trait bound `&Thing: ref_cast::custom::RefCastOkay<&String>` is not satisfied
 --> tests/ui/no-custom.rs:8:36
  |
8 |     pub fn ref_cast(s: &String) -> &Self;
  |                                    ^^^^^ unsatisfied trait bound
  |
help: the trait `ref_cast::__private25::RefCastCustom<String>` is not implemented for `Thing`
 --> tests/ui/no-custom.rs:4:1
  |
4 | pub struct Thing(String);
  | ^^^^^^^^^^^^^^^^
help: the following other types implement trait `ref_cast::custom::RefCastOkay<From>`
 --> src/custom.rs
  |
  | / unsafe impl<'a, From, To> RefCastOkay<&'a From> for &'a To
  | | where
  | |     From: ?Sized,
  | |     To: ?Sized + RefCastCustom<From>,
  | |_____________________________________^ `&'a To` implements `ref_cast::custom::RefCastOkay<&'a From>`
...
  | / unsafe impl<'a, From, To> RefCastOkay<&'a mut From> for &'a mut To
  | | where
  | |     From: ?Sized,
  | |     To: ?Sized + RefCastCustom<From>,
  | |_____________________________________^ `&'a mut To` implements `ref_cast::custom::RefCastOkay<&'a mut From>`
  = note: required for `&Thing` to implement `ref_cast::custom::RefCastOkay<&String>`
note: required by a bound in `ref_cast::__private25::ref_cast_custom`
 --> src/custom.rs
  |
  | pub fn ref_cast_custom<From, To>(_arg: From)
  |        --------------- required by a bound in this function
  | where
  |     To: RefCastOkay<From>,
  |         ^^^^^^^^^^^^^^^^^ required by this bound in `ref_cast_custom`

error[E0071]: expected struct, variant or union type, found inferred type
 --> tests/ui/no-custom.rs:8:41
  |
8 |     pub fn ref_cast(s: &String) -> &Self;
  |                                         ^ not a struct

error[E0277]: the trait bound `Thing: ref_cast::__private25::RefCastCustom<String>` is not satisfied
 --> tests/ui/no-custom.rs:8:41
  |
8 |     pub fn ref_cast(s: &String) -> &Self;
  |                                         ^ unsatisfied trait bound
  |
help: the trait `ref_cast::__private25::RefCastCustom<String>` is not implemented for `Thing`
 --> tests/ui/no-custom.rs:4:1
  |
4 | pub struct Thing(String);
  | ^^^^^^^^^^^^^^^^
help: the following other types implement trait `ref_cast::custom::RefCastOkay<From>`
 --> src/custom.rs
  |
  | / unsafe impl<'a, From, To> RefCastOkay<&'a From> for &'a To
  | | where
  | |     From: ?Sized,
  | |     To: ?Sized + RefCastCustom<From>,
  | |_____________________________________^ `&'a To` implements `ref_cast::custom::RefCastOkay<&'a From>`
...
  | / unsafe impl<'a, From, To> RefCastOkay<&'a mut From> for &'a mut To
  | | where
  | |     From: ?Sized,
  | |     To: ?Sized + RefCastCustom<From>,
  | |_____________________________________^ `&'a mut To` implements `ref_cast::custom::RefCastOkay<&'a mut From>`
  = note: required for `&Thing` to implement `ref_cast::custom::RefCastOkay<&String>`