Fix match enum OR comment indentation

src/lists.rs

@@ -11,8 +11,8 @@ use crate::config::{Config, IndentStyle};
 use crate::rewrite::{ExceedsMaxWidthError, RewriteContext, RewriteError, RewriteResult};
 use crate::shape::{Indent, Shape};
 use crate::utils::{
-    count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline,
-    unicode_str_width,
+    count_newlines, first_line_width, last_line_unindented_width, last_line_width, mk_sp,
+    starts_with_newline, unicode_str_width,
 };
 use crate::visitor::SnippetProvider;
 
@@ -468,8 +468,13 @@ where
 
             if !starts_with_newline(comment) {
                 if formatting.align_comments {
+                    // If it's a multiline inner item, the length of indentation shouldn't
+                    // be counted when evaluating line length with respect to comments.
+                    let inner_item_width = last_line_unindented_width(&inner_item)
+                        .unwrap_or_else(|| unicode_str_width(inner_item));
+
                     let mut comment_alignment =
-                        post_comment_alignment(item_max_width, unicode_str_width(inner_item));
+                        post_comment_alignment(item_max_width, inner_item_width);
                     if first_line_width(&formatted_comment)
                         + last_line_width(&result)
                         + comment_alignment

src/utils.rs

@@ -208,6 +208,14 @@ pub(crate) fn last_line_width(s: &str) -> usize {
     unicode_str_width(s.rsplitn(2, '\n').next().unwrap_or(""))
 }
 
+#[inline]
+pub(crate) fn last_line_unindented_width(s: &str) -> Option<usize> {
+    s.rsplitn(2, '\n').next().map(|s| {
+        let trimmed = s.trim_start();
+        unicode_str_width(trimmed)
+    })
+}
+
 /// The total used width of the last line.
 #[inline]
 pub(crate) fn last_line_used_width(s: &str, offset: usize) -> usize {

tests/source/issue-6060/line_split.rs

@@ -0,0 +1,9 @@
+fn dummy() {
+    let error_code = match err {
+        msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
+        msgs::DecodeError::UnknownRequiredFeature
+        | msgs::DecodeError::InvalidValue
+        | msgs::DecodeError::ShortReadNowExceedesMaxLineWidthAndTriggersAnotherBranch => 0x4000 | 22,   // invalid_onion
+        _ => 0x2000 | 2,                                 // Should never happen
+    };
+}

tests/target/issue-6060/line_split.rs

@@ -0,0 +1,11 @@
+fn dummy() {
+    let error_code = match err {
+        msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
+        msgs::DecodeError::UnknownRequiredFeature
+        | msgs::DecodeError::InvalidValue
+        | msgs::DecodeError::ShortReadNowExceedesMaxLineWidthAndTriggersAnotherBranch => {
+            0x4000 | 22
+        }                                                // invalid_onion
+        _ => 0x2000 | 2,                                 // Should never happen
+    };
+}

tests/target/issue-6060/no_line_split.rs

@@ -0,0 +1,9 @@
+fn dummy() {
+    let error_code = match err {
+        msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
+        msgs::DecodeError::UnknownRequiredFeature
+        | msgs::DecodeError::InvalidValue
+        | msgs::DecodeError::ShortRead => 0x4000 | 22,   // invalid_onion
+        _ => 0x2000 | 2,                                 // Should never happen
+    };
+}