error[E0308]: mismatched types
  --> $DIR/return-impl-trait-bad.rs:5:5
   |
LL | fn bad_echo<T>(_t: T) -> T {
   |             -            - expected `T` because of return type
   |             |
   |             expected this type parameter
LL |     "this should not suggest impl Trait"
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found `&str`
   |
   = note: expected type parameter `T`
                   found reference `&'static str`
   = note: the caller chooses a type for `T` which can be different from `&'static str`

error[E0308]: mismatched types
  --> $DIR/return-impl-trait-bad.rs:9:5
   |
LL | fn bad_echo_2<T: Trait>(_t: T) -> T {
   |               -                   - expected `T` because of return type
   |               |
   |               expected this type parameter
LL |     "this will not suggest it, because that would probably be wrong"
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found `&str`
   |
   = note: expected type parameter `T`
                   found reference `&'static str`
   = note: the caller chooses a type for `T` which can be different from `&'static str`

error[E0308]: mismatched types
  --> $DIR/return-impl-trait-bad.rs:17:5
   |
LL | fn other_bounds_bad<T>() -> T
   |                     -       - expected `T` because of return type
   |                     |
   |                     expected this type parameter
...
LL |     "don't suggest this, because Option<T> places additional constraints"
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found `&str`
   |
   = note: expected type parameter `T`
                   found reference `&'static str`
   = note: the caller chooses a type for `T` which can be different from `&'static str`

error[E0308]: mismatched types
  --> $DIR/return-impl-trait-bad.rs:28:5
   |
LL | fn used_in_trait<T>() -> T
   |                  -       -
   |                  |       |
   |                  |       expected `T` because of return type
   |                  |       help: consider using an impl return type: `impl Send`
   |                  expected this type parameter
...
LL |     "don't suggest this, because the generic param is used in the bound."
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found `&str`
   |
   = note: expected type parameter `T`
                   found reference `&'static str`
   = note: the caller chooses a type for `T` which can be different from `&'static str`

error: aborting due to 4 previous errors

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