Fix matching on SqlState

Closes #756

codegen/src/sqlstate.rs

@@ -1,5 +1,4 @@
 use linked_hash_map::LinkedHashMap;
-use phf_codegen;
 use std::fs::File;
 use std::io::{BufWriter, Write};
 
@@ -11,7 +10,9 @@ pub fn build() {
     let codes = parse_codes();
 
     make_type(&mut file);
+    make_code(&codes, &mut file);
     make_consts(&codes, &mut file);
+    make_inner(&codes, &mut file);
     make_map(&codes, &mut file);
 }
 
@@ -38,26 +39,51 @@ fn make_type(file: &mut BufWriter<File>) {
     write!(
         file,
         "// Autogenerated file - DO NOT EDIT
-use std::borrow::Cow;
 
 /// A SQLSTATE error code
 #[derive(PartialEq, Eq, Clone, Debug)]
-pub struct SqlState(Cow<'static, str>);
+pub struct SqlState(Inner);
 
 impl SqlState {{
     /// Creates a `SqlState` from its error code.
     pub fn from_code(s: &str) -> SqlState {{
         match SQLSTATE_MAP.get(s) {{
             Some(state) => state.clone(),
-            None => SqlState(Cow::Owned(s.to_string())),
+            None => SqlState(Inner::Other(s.into())),
         }}
     }}
+"
+    )
+    .unwrap();
+}
 
+fn make_code(codes: &LinkedHashMap<String, Vec<String>>, file: &mut BufWriter<File>) {
+    write!(
+        file,
+        r#"
     /// Returns the error code corresponding to the `SqlState`.
     pub fn code(&self) -> &str {{
-        &self.0
+        match &self.0 {{"#,
+    )
+    .unwrap();
+
+    for code in codes.keys() {
+        write!(
+            file,
+            r#"
+            Inner::E{code} => "{code}","#,
+            code = code,
+        )
+        .unwrap();
+    }
+
+    write!(
+        file,
+        r#"
+            Inner::Other(code) => code,
+        }}
     }}
-"
+        "#
     )
     .unwrap();
 }
@@ -69,7 +95,7 @@ fn make_consts(codes: &LinkedHashMap<String, Vec<String>>, file: &mut BufWriter<
                 file,
                 r#"
     /// {code}
-    pub const {name}: SqlState = SqlState(Cow::Borrowed("{code}"));
+    pub const {name}: SqlState = SqlState(Inner::E{code});
 "#,
                 name = name,
                 code = code,
@@ -81,6 +107,34 @@ fn make_consts(codes: &LinkedHashMap<String, Vec<String>>, file: &mut BufWriter<
     write!(file, "}}").unwrap();
 }
 
+fn make_inner(codes: &LinkedHashMap<String, Vec<String>>, file: &mut BufWriter<File>) {
+    write!(
+        file,
+        r#"
+
+#[derive(PartialEq, Eq, Clone, Debug)]
+enum Inner {{"#,
+    )
+    .unwrap();
+    for code in codes.keys() {
+        write!(
+            file,
+            r#"
+    E{},"#,
+            code,
+        )
+        .unwrap();
+    }
+    write!(
+        file,
+        r#"
+    Other(Box<str>),
+}}
+        "#,
+    )
+    .unwrap();
+}
+
 fn make_map(codes: &LinkedHashMap<String, Vec<String>>, file: &mut BufWriter<File>) {
     let mut builder = phf_codegen::Map::new();
     for (code, names) in codes {