1 error: lifetime parameter `'a` only used once
2 --> $DIR/fn-types.rs:9:10
4 LL | a: for<'a> fn(&'a u32),
5 | ^^ -- ...is used only here
9 note: the lint level is defined here
10 --> $DIR/fn-types.rs:1:9
12 LL | #![deny(single_use_lifetimes)]
13 | ^^^^^^^^^^^^^^^^^^^^
15 error[E0581]: return type references lifetime `'a`, which is not constrained by the fn input types
16 --> $DIR/fn-types.rs:12:22
18 LL | d: for<'a> fn() -> &'a u32, // OK, used only in return type.
21 error: aborting due to 2 previous errors
23 For more information about this error, try `rustc --explain E0581`.