error[E0106]: missing lifetime specifier
  --> $DIR/issue-30255.rs:9:24
   |
LL | fn f(a: &S, b: i32) -> &i32 {
   |                        ^ expected lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but the signature does not say which one of `a`'s 2 lifetimes it is borrowed from

error[E0106]: missing lifetime specifier
  --> $DIR/issue-30255.rs:14:34
   |
LL | fn g(a: &S, b: bool, c: &i32) -> &i32 {
   |                                  ^ expected lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `a`'s 2 lifetimes or `c`

error[E0106]: missing lifetime specifier
  --> $DIR/issue-30255.rs:19:44
   |
LL | fn h(a: &bool, b: bool, c: &S, d: &i32) -> &i32 {
   |                                            ^ expected lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a`, one of `c`'s 2 lifetimes, or `d`

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0106`.