| #### Note: this error code is no longer emitted by the compiler. |
| |
| Sub-bindings, e.g. `ref x @ Some(ref y)` are now allowed under |
| `#![feature(bindings_after_at)]` and checked to make sure that |
| memory safety is upheld. |
| |
| -------------- |
| |
| In certain cases it is possible for sub-bindings to violate memory safety. |
| Updates to the borrow checker in a future version of Rust may remove this |
| restriction, but for now patterns must be rewritten without sub-bindings. |
| |
| Before: |
| |
| ```compile_fail |
| match Some("hi".to_string()) { |
| ref op_string_ref @ Some(s) => {}, |
| None => {}, |
| } |
| ``` |
| |
| After: |
| |
| ``` |
| match Some("hi".to_string()) { |
| Some(ref s) => { |
| let op_string_ref = &Some(s); |
| // ... |
| }, |
| None => {}, |
| } |
| ``` |
| |
| The `op_string_ref` binding has type `&Option<&String>` in both cases. |
| |
| See also [Issue 14587][issue-14587]. |
| |
| [issue-14587]: https://github.com/rust-lang/rust/issues/14587 |
