error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds
  --> $DIR/issue-105227.rs:7:5
   |
LL | fn chars0(v :(& str, &str)) -> impl Iterator<Item = char> {
   |               ----- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here
LL |
LL |     v.0.chars().chain(v.1.chars())
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a`
   |
LL | fn chars0<'a>(v :(&'a  str, &'a str)) -> impl Iterator<Item = char> + 'a  {
   |          ++++      ++        ++                                     ++++

error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds
  --> $DIR/issue-105227.rs:13:5
   |
LL | fn chars1(v0 : & str, v1 : &str) -> impl Iterator<Item = char> {
   |                ----- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here
LL |
LL |     v0.chars().chain(v1.chars())
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: to declare that `impl Iterator<Item = char>` captures `'_`, you can introduce a named lifetime parameter `'a`
   |
LL | fn chars1<'a>(v0 : &'a  str, v1 : &'a str) -> impl Iterator<Item = char> + 'a  {
   |          ++++       ++             ++                                    ++++

error[E0700]: hidden type for `impl Iterator<Item = char>` captures lifetime that does not appear in bounds
  --> $DIR/issue-105227.rs:21:5
   |
LL | fn chars2<'b>(v0 : &str, v1 : &'_ str, v2 : &'b str) ->
   |                    ---- hidden type `std::iter::Chain<Chars<'_>, Chars<'_>>` captures the anonymous lifetime defined here
...
LL |     (v0.chars().chain(v1.chars()), v2)
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: to declare that `impl Iterator<Item = char>` captures `'_`, you can use the named lifetime parameter `'b`
   |
LL ~ fn chars2<'b>(v0 : &'b str, v1 : &'b str, v2 : &'b str) ->
LL |
LL ~     (impl Iterator<Item = char> + 'b , &'b str)
   |

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0700`.