Add support for historical uppercase user IDs

CHANGELOG.md

@@ -1,5 +1,9 @@
 # [unreleased]
 
+Improvements:
+
+* Add support for historical uppercase MXIDs 
+
 # 0.14.1
 
 Breaking changes:

src/user_id.rs

@@ -123,10 +123,9 @@ impl TryFrom<&str> for UserId {
     /// server name.
     fn try_from(user_id: &str) -> Result<Self, Error> {
         let (localpart, host, port) = parse_id('@', user_id)?;
-        let downcased_localpart = localpart.to_lowercase();
 
         // See https://matrix.org/docs/spec/appendices#user-identifiers
-        let is_fully_conforming = downcased_localpart.bytes().all(|b| match b {
+        let is_fully_conforming = localpart.bytes().all(|b| match b {
             b'0'..=b'9' | b'a'..=b'z' | b'-' | b'.' | b'=' | b'_' | b'/' => true,
             _ => false,
         });
@@ -134,18 +133,14 @@ impl TryFrom<&str> for UserId {
         // If it's not fully conforming, check if it contains characters that are also disallowed
         // for historical user IDs. If there are, return an error.
         // See https://matrix.org/docs/spec/appendices#historical-user-ids
-        if !is_fully_conforming
-            && downcased_localpart
-                .bytes()
-                .any(|b| b < 0x21 || b == b':' || b > 0x7E)
-        {
+        if !is_fully_conforming && localpart.bytes().any(|b| b < 0x21 || b == b':' || b > 0x7E) {
             return Err(Error::InvalidCharacters);
         }
 
         Ok(Self {
             hostname: host,
             port,
-            localpart: downcased_localpart,
+            localpart: localpart.to_owned(),
             is_historical: !is_fully_conforming,
         })
     }
@@ -176,12 +171,9 @@ mod tests {
 
     #[test]
     fn downcase_user_id() {
-        assert_eq!(
-            UserId::try_from("@CARL:example.com")
-                .expect("Failed to create UserId.")
-                .to_string(),
-            "@carl:example.com"
-        );
+        let user_id = UserId::try_from("@CARL:example.com").expect("Failed to create UserId.");
+        assert_eq!(user_id.to_string(), "@CARL:example.com");
+        assert!(user_id.is_historical());
     }
 
     #[test]