error[E0277]: `()` doesn't implement `std::fmt::Display`
  --> $DIR/issue-81098.rs:3:13
   |
LL | fn wat() -> impl core::fmt::Display {
   |             ^^^^^^^^^^^^^^^^^^^^^^^ `()` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `()`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

error[E0277]: `()` doesn't implement `std::fmt::Display`
  --> $DIR/issue-81098.rs:3:37
   |
LL |   fn wat() -> impl core::fmt::Display {
   |  _____________________________________^
LL | |
LL | |     fn why() {}
LL | | }
   | |_^ `()` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `()`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

error[E0277]: `()` doesn't implement `std::fmt::Display`
  --> $DIR/issue-81098.rs:10:12
   |
LL | fn ok() -> impl core::fmt::Display {
   |            ^^^^^^^^^^^^^^^^^^^^^^^ `()` cannot be formatted with the default formatter
LL |
LL |     1;
   |     -- help: remove this semicolon
   |     |
   |     this expression has type `{integer}`, which implements `std::fmt::Display`
   |
   = help: the trait `std::fmt::Display` is not implemented for `()`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

error[E0277]: `()` doesn't implement `std::fmt::Display`
  --> $DIR/issue-81098.rs:10:36
   |
LL |   fn ok() -> impl core::fmt::Display {
   |  ____________________________________^
LL | |
LL | |     1;
LL | | }
   | |_^ `()` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `()`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0277`.