error[E0106]: missing lifetime specifier --> $DIR/impl-fn-hrtb-bounds.rs:19:38 | LL | fn d() -> impl Fn() -> (impl Debug + '_) { | ^^ expected named lifetime parameter | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`, or if you will only have owned values | LL | fn d() -> impl Fn() -> (impl Debug + 'static) { | ~~~~~~~ error: higher kinded lifetime bounds on nested opaque types are not supported yet --> $DIR/impl-fn-hrtb-bounds.rs:4:41 | LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) { | ^^ | note: lifetime declared here --> $DIR/impl-fn-hrtb-bounds.rs:4:19 | LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) { | ^ error: higher kinded lifetime bounds on nested opaque types are not supported yet --> $DIR/impl-fn-hrtb-bounds.rs:9:52 | LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) { | ^^ | note: lifetime declared here --> $DIR/impl-fn-hrtb-bounds.rs:9:20 | LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) { | ^^ error: higher kinded lifetime bounds on nested opaque types are not supported yet --> $DIR/impl-fn-hrtb-bounds.rs:14:52 | LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) { | ^^ | note: lifetime declared here --> $DIR/impl-fn-hrtb-bounds.rs:14:20 | LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) { | ^^ error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0106`.