Error code E0297

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

Patterns used to bind names must be irrefutable. That is, they must guarantee that a name will be extracted in all cases. Instead of pattern matching the loop variable, consider using a match or if let inside the loop body. For instance:

#![allow(unused)] fn main() { let xs : Vec<Option<i32>> = vec![Some(1), None]; // This fails because `None` is not covered. for Some(x) in xs { // ... } }

Match inside the loop instead:

#![allow(unused)] fn main() { let xs : Vec<Option<i32>> = vec![Some(1), None]; for item in xs { match item { Some(x) => {}, None => {}, } } }

Or use if let:

#![allow(unused)] fn main() { let xs : Vec<Option<i32>> = vec![Some(1), None]; for item in xs { if let Some(x) = item { // ... } } }