Error code E0312

Note: this error code is no longer emitted by the compiler.

Reference's lifetime of borrowed content doesn't match the expected lifetime.

Erroneous code example:

#![allow(unused)] fn main() { pub fn opt_str<'a>(maybestr: &'a Option<String>) -> &'static str { if maybestr.is_none() { "(none)" } else { let s: &'a str = maybestr.as_ref().unwrap(); s // Invalid lifetime! } } }

To fix this error, either lessen the expected lifetime or find a way to not have to use this reference outside of its current scope (by running the code directly in the same block for example?):

#![allow(unused)] fn main() { // In this case, we can fix the issue by switching from "static" lifetime to 'a pub fn opt_str<'a>(maybestr: &'a Option<String>) -> &'a str { if maybestr.is_none() { "(none)" } else { let s: &'a str = maybestr.as_ref().unwrap(); s // Ok! } } }