error[E0666]: nested `impl Trait` is not allowed
  --> $DIR/nested_impl_trait.rs:6:56
   |
LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
   |                                              ----------^^^^^^^^^^-
   |                                              |         |
   |                                              |         nested `impl Trait` here
   |                                              outer `impl Trait`

error[E0666]: nested `impl Trait` is not allowed
  --> $DIR/nested_impl_trait.rs:10:42
   |
LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
   |                                ----------^^^^^^^^^^-
   |                                |         |
   |                                |         nested `impl Trait` here
   |                                outer `impl Trait`

error[E0666]: nested `impl Trait` is not allowed
  --> $DIR/nested_impl_trait.rs:14:37
   |
LL | fn bad_in_arg_position(_: impl Into<impl Debug>) { }
   |                           ----------^^^^^^^^^^-
   |                           |         |
   |                           |         nested `impl Trait` here
   |                           outer `impl Trait`

error[E0666]: nested `impl Trait` is not allowed
  --> $DIR/nested_impl_trait.rs:19:44
   |
LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
   |                                  ----------^^^^^^^^^^-
   |                                  |         |
   |                                  |         nested `impl Trait` here
   |                                  outer `impl Trait`

error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
  --> $DIR/nested_impl_trait.rs:10:32
   |
LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
   |                                ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `impl Trait` is only allowed in arguments and return types of functions and methods

error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
  --> $DIR/nested_impl_trait.rs:6:46
   |
LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
   |                                              ^^^^^^^^^^^^^^^^^^^^^   - return type was inferred to be `impl Into<u32>` here
   |                                              |
   |                                              the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
   |
help: the trait `Into<U>` is implemented for `T`
  --> $SRC_DIR/core/src/convert/mod.rs:LL:COL
   = note: required for `impl Into<u32>` to implement `Into<impl Debug>`

error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
  --> $DIR/nested_impl_trait.rs:19:34
   |
LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
   |                                  ^^^^^^^^^^^^^^^^^^^^^   - return type was inferred to be `impl Into<u32>` here
   |                                  |
   |                                  the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
   |
help: the trait `Into<U>` is implemented for `T`
  --> $SRC_DIR/core/src/convert/mod.rs:LL:COL
   = note: required for `impl Into<u32>` to implement `Into<impl Debug>`

error: aborting due to 7 previous errors

Some errors have detailed explanations: E0277, E0562, E0666.
For more information about an error, try `rustc --explain E0277`.