error[E0308]: mismatched types --> $DIR/return-impl-trait-bad.rs:5:5 | LL | fn bad_echo(_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` error[E0308]: mismatched types --> $DIR/return-impl-trait-bad.rs:9:5 | LL | fn bad_echo_2(_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` error[E0308]: mismatched types --> $DIR/return-impl-trait-bad.rs:17:5 | LL | fn other_bounds_bad() -> T | - - expected `T` because of return type | | | expected this type parameter ... LL | "don't suggest this, because Option places additional constraints" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected type parameter `T`, found `&str` | = note: expected type parameter `T` found reference `&'static str` error[E0308]: mismatched types --> $DIR/return-impl-trait-bad.rs:28:5 | LL | fn used_in_trait() -> 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` error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0308`.