https://doc.rust-lang.org/error_codes/E0230.html
E0230 - Error codes index
Book listing all Rust error codes
error codesindex
https://doc.rust-lang.org/beta/nightly-rustc/rustc_errors/codes/constant.E0230.html
E0230 in rustc_errors::codes - Rust
API documentation for the Rust `E0230` constant in crate `rustc_errors`.
rustcerrorscodes