From 24b3523414190c41576c4a9d83ee4a2023768e19 Mon Sep 17 00:00:00 2001
From: Kevin Newton <kddnewton@gmail.com>
Date: Tue, 13 Oct 2026 19:40:07 -0400
Subject: [PATCH] Make Diagnostic::message in Rust return slice

---
 CHANGELOG.md                                    |  9 ++++++++-
 rust/ruby-prism/src/lib.rs                      | 11 +++++++++++
 rust/ruby-prism/src/parse_result/diagnostics.rs | 10 +++++-----
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b9cab65f65..c0fac11a7c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -57,7 +57,7 @@ Note that for this major version, almost every change listed below is breaking.
 - Comments now live on the source. `Prism::Source#comments` returns them and `Result#comments` delegates to it, so `ParseResult.new`, `LexResult.new`, and `ParseLexResult.new` no longer take a `comments` argument.
 - Comment attachment now happens during parsing with the `attach_comments` option instead of afterward with `ParseResult#attach_comments!`, which was removed. `Node#comments` now returns the comments attached to the node by that option. `Location#comments`, `Location#leading_comments`, `Location#trailing_comments`, `Node#leading_comments`, `Node#trailing_comments`, and the comment fields of `Prism::Relocation` were removed.
 
-#### C/Rust
+#### C
 
 - Most structs are now opaque (except for nodes), and many internal functions have been hidden.
 - Locations are now represented using slices (pairs of 32-bit integers for start offset and length).
@@ -65,6 +65,13 @@ Note that for this major version, almost every change listed below is breaking.
 - You may now build side tables of comment attachments through the `attach_comments` option.
 - `newline_list` was renamed to `list_offset_list`.
 
+#### Rust
+
+- Locations are now represented using slices (pairs of 32-bit integers for start offset and length).
+- Most allocations are now performed through an arena.
+- `newline_list` was renamed to `list_offset_list`.
+- `Diagnostic::message` now returns `&[u8]` instead of `&str`.
+
 #### JavaScript
 
 - The parse method now only accepts `Uint8Array`, instead of forcing a transcoding to UTF-16.
diff --git a/rust/ruby-prism/src/lib.rs b/rust/ruby-prism/src/lib.rs
index 3ae8e70437..071e35d25a 100644
--- a/rust/ruby-prism/src/lib.rs
+++ b/rust/ruby-prism/src/lib.rs
@@ -1160,6 +1160,17 @@ end
         assert!(stmt.as_local_variable_read_node().is_some());
     }
 
+    #[test]
+    fn diagnostic_message_test() {
+        let source = b"# encoding: shift_jis\nx = <<~\x82\xA0\n";
+        let result = parse(source);
+        let error = result.errors().next().unwrap();
+
+        let message = error.message();
+        assert!(std::str::from_utf8(message).is_err());
+        assert!(message.windows(2).any(|window| window == b"\x82\xA0"));
+    }
+
     #[test]
     fn malformed_shebang() {
         let source = "#!\x00";
diff --git a/rust/ruby-prism/src/parse_result/diagnostics.rs b/rust/ruby-prism/src/parse_result/diagnostics.rs
index ba231fabb2..799a7c6513 100644
--- a/rust/ruby-prism/src/parse_result/diagnostics.rs
+++ b/rust/ruby-prism/src/parse_result/diagnostics.rs
@@ -18,14 +18,14 @@ pub struct Diagnostic<'pr> {
 impl<'pr> Diagnostic<'pr> {
     /// Returns the message associated with the diagnostic.
     ///
-    /// # Panics
-    ///
-    /// Panics if the message is not valid UTF-8.
+    /// The message is in the encoding of the source, because some messages
+    /// quote the source directly. It is therefore not guaranteed to be valid
+    /// UTF-8.
     #[must_use]
-    pub fn message(&self) -> &str {
+    pub fn message(&self) -> &[u8] {
         unsafe {
             let message = pm_diagnostic_message(self.raw);
-            CStr::from_ptr(message).to_str().expect("prism allows only UTF-8 for diagnostics.")
+            CStr::from_ptr(message).to_bytes()
         }
     }