Archive Rust bootstrap — El compiler is now self-hosting

_archive/rust-bootstrap/engrams/el-fmt/src/error.rs

@@ -0,0 +1,11 @@
+//! Error types for el-fmt.
+
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum FmtError {
+    #[error("lex error: {0}")]
+    Lex(String),
+    #[error("parse error: {0}")]
+    Parse(String),
+}