From 0b4cbdf5562847c3eb59cf1918e053e3a563738c Mon Sep 17 00:00:00 2001
From: Lukas Wirth <me@lukaswirth.dev>
Date: Fri, 4 Jul 2025 11:05:05 +0200
Subject: [PATCH] minor: Handle match arm commas in `make::match_arm`

Co-authored-by: Giga Bowser <45986823+Giga-Bowser@users.noreply.github.com>
---
 .../src/handlers/unmerge_match_arm.rs         | 23 +++++--------------
 .../crates/syntax/src/ast/make.rs             |  7 +++---
 .../crates/syntax/src/syntax_editor.rs        |  2 +-
 3 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/unmerge_match_arm.rs b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/unmerge_match_arm.rs
index 609ef347183e..7b0f2dc65a78 100644
--- a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/unmerge_match_arm.rs
+++ b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/unmerge_match_arm.rs
@@ -1,6 +1,5 @@
 use syntax::{
     Direction, SyntaxKind, T,
-    algo::neighbor,
     ast::{self, AstNode, edit::IndentLevel, syntax_factory::SyntaxFactory},
     syntax_editor::{Element, Position},
 };
@@ -88,15 +87,8 @@ pub(crate) fn unmerge_match_arm(acc: &mut Assists, ctx: &AssistContext<'_>) -> O
             //    body is a block, but we don't bother to check that.
             //  - Missing after the arm with arms after, if the arm body is a block. In this case
             //    we don't want to insert a comma at all.
-            let has_comma_after =
-                std::iter::successors(match_arm.syntax().last_child_or_token(), |it| {
-                    it.prev_sibling_or_token()
-                })
-                .map(|it| it.kind())
-                .find(|it| !it.is_trivia())
-                    == Some(T![,]);
-            let has_arms_after = neighbor(&match_arm, Direction::Next).is_some();
-            if !has_comma_after && !has_arms_after {
+            let has_comma_after = match_arm.comma_token().is_some();
+            if !has_comma_after && !match_arm.expr().unwrap().is_block_like() {
                 insert_after_old_arm.push(make.token(T![,]).into());
             }
 
@@ -105,9 +97,6 @@ pub(crate) fn unmerge_match_arm(acc: &mut Assists, ctx: &AssistContext<'_>) -> O
 
             insert_after_old_arm.push(new_match_arm.syntax().clone().into());
 
-            if has_comma_after {
-                insert_after_old_arm.push(make.token(T![,]).into());
-            }
             editor.insert_all(Position::after(match_arm.syntax()), insert_after_old_arm);
             editor.add_mappings(make.finish_with_mappings());
             edit.add_file_edits(ctx.vfs_file_id(), editor);
@@ -256,7 +245,7 @@ fn main() {
     let x = X::A;
     let y = match x {
         X::A => 1i32,
-        X::B => 1i32
+        X::B => 1i32,
     };
 }
 "#,
@@ -274,7 +263,7 @@ enum X { A, B }
 fn main() {
     let x = X::A;
     match x {
-        X::A $0| X::B => {},
+        X::A $0| X::B => {}
     }
 }
 "#,
@@ -285,8 +274,8 @@ enum X { A, B }
 fn main() {
     let x = X::A;
     match x {
-        X::A => {},
-        X::B => {},
+        X::A => {}
+        X::B => {}
     }
 }
 "#,
diff --git a/src/tools/rust-analyzer/crates/syntax/src/ast/make.rs b/src/tools/rust-analyzer/crates/syntax/src/ast/make.rs
index 955aadaa25d3..309332873cb8 100644
--- a/src/tools/rust-analyzer/crates/syntax/src/ast/make.rs
+++ b/src/tools/rust-analyzer/crates/syntax/src/ast/make.rs
@@ -842,9 +842,10 @@ pub fn ref_pat(pat: ast::Pat) -> ast::RefPat {
 }
 
 pub fn match_arm(pat: ast::Pat, guard: Option<ast::MatchGuard>, expr: ast::Expr) -> ast::MatchArm {
+    let comma_str = if expr.is_block_like() { "" } else { "," };
     return match guard {
-        Some(guard) => from_text(&format!("{pat} {guard} => {expr}")),
-        None => from_text(&format!("{pat} => {expr}")),
+        Some(guard) => from_text(&format!("{pat} {guard} => {expr}{comma_str}")),
+        None => from_text(&format!("{pat} => {expr}{comma_str}")),
     };
 
     fn from_text(text: &str) -> ast::MatchArm {
@@ -877,7 +878,7 @@ pub fn match_arm_list(arms: impl IntoIterator<Item = ast::MatchArm>) -> ast::Mat
     let arms_str = arms.into_iter().fold(String::new(), |mut acc, arm| {
         let needs_comma =
             arm.comma_token().is_none() && arm.expr().is_none_or(|it| !it.is_block_like());
-        let comma = if needs_comma { "," } else { "" };
+        let comma = if needs_comma && arm.comma_token().is_none() { "," } else { "" };
         let arm = arm.syntax();
         format_to_acc!(acc, "    {arm}{comma}\n")
     });
diff --git a/src/tools/rust-analyzer/crates/syntax/src/syntax_editor.rs b/src/tools/rust-analyzer/crates/syntax/src/syntax_editor.rs
index 31caf618be90..3fa584850f77 100644
--- a/src/tools/rust-analyzer/crates/syntax/src/syntax_editor.rs
+++ b/src/tools/rust-analyzer/crates/syntax/src/syntax_editor.rs
@@ -435,7 +435,7 @@ mod tests {
             _ => {
                 let var_name = 2 + 2;
                 (var_name, true)
-            }"#]];
+            },"#]];
         expect.assert_eq(&edit.new_root.to_string());
 
         assert_eq!(edit.find_annotation(placeholder_snippet).len(), 2);