An underscore `_` character has been used as the identifier for a lifetime.
-Erroneous example:
+Erroneous code example:
+
```compile_fail,E0106,E0637
fn longest<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
//^^ `'_` is a reserved lifetime name
}
}
```
+
`'_`, cannot be used as a lifetime identifier because it is a reserved for the
anonymous lifetime. To fix this, use a lowercase letter such as 'a, or a series
of lowercase letters such as `'foo`. For more information, see [the
nightly, see [the nightly book][bk-al].
Corrected example:
+
```
fn longest<'a>(str1: &'a str, str2: &'a str) -> &'a str {
if str1.len() > str2.len() {