Some regex-automata migration follow-ups

engine/Cargo.toml

@@ -38,5 +38,5 @@ criterion.workspace = true
 indoc.workspace = true
 
 [features]
-regex = ["dep:regex-automata"]
 default = [ "regex" ]
+regex = ["dep:regex-automata"]

engine/src/rhs_types/regex/imp_real.rs

@@ -16,15 +16,15 @@ pub struct Regex {
 impl Regex {
     /// Retrieves the syntax configuration that will be used to build the regex.
     #[inline]
-    pub fn syntax_config() -> regex_automata::util::syntax::Config {
+    fn syntax_config() -> regex_automata::util::syntax::Config {
         regex_automata::util::syntax::Config::new()
             .unicode(false)
             .utf8(false)
     }
 
     /// Retrieves the meta configuration that will be used to build the regex.
     #[inline]
-    pub fn meta_config(settings: &ParserSettings) -> regex_automata::meta::Config {
+    fn meta_config(settings: &ParserSettings) -> regex_automata::meta::Config {
         regex_automata::meta::Config::new()
             .match_kind(MatchKind::LeftmostFirst)
             .utf8_empty(false)
@@ -56,7 +56,7 @@ impl Regex {
                 } else if let Some(syntax) = err.syntax_error() {
                     Error::Syntax(syntax.to_string())
                 } else {
-                    unreachable!()
+                    Error::Other(err.to_string())
                 }
             })
     }

engine/src/rhs_types/regex/mod.rs

@@ -135,21 +135,15 @@ impl Serialize for Regex {
 #[derive(Clone, Debug, Error, PartialEq)]
 pub enum Error {
     /// A syntax error.
+    #[error("{0}")]
     Syntax(String),
     /// The compiled regex exceeded the configured
     /// regex compiled size limit.
+    #[error("Compiled regex exceeds size limit of {0} bytes.")]
     CompiledTooBig(usize),
-}
-
-impl Display for Error {
-    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        match *self {
-            Error::Syntax(ref err) => Display::fmt(err, f),
-            Error::CompiledTooBig(limit) => {
-                write!(f, "Compiled regex exceeds size limit of {} bytes.", limit)
-            }
-        }
-    }
+    /// An uncategorized error.
+    #[error("{0}")]
+    Other(String),
 }
 
 #[cfg(test)]