[llvm-branch-commits] [clang] release/23.x: [clang-format] Fix short functions with nested braced-init (#213550) (PR #216717)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/216717

Backport e98256cc6abdc97701a3b1fa2588e2628180ead2

Requested by: @HazardyKnusperkeks

>From 839efd31d6e7f4af21954b104fda6819b8abb3e3 Mon Sep 17 00:00:00 2001
From: Gauarv Chaudhary <137998824+ANAMASGARD at users.noreply.github.com>
Date: Mon, 17 Aug 2026 17:36:47 +0530
Subject: [PATCH] [clang-format] Fix short functions with nested braced-init
 (#213550)

Fixes #213286.

Keep short functions on one line when their return statement contains
nested braced initializers.

The closing brace now checks the kind of its matching opening brace, so
braced-init lists are allowed while structural
  braces still prevent merging.

  Tests:
  - `FormatTest.CustomShortFunctionOptions`
  - `FormatTest.AllowShortRecordOnASingleLine`
  - full `FormatTests` suite (1275 passed)

Signed-off-by: Gaurav Chaudhary <chaudharygaurav2004 at gmail.com>
(cherry picked from commit e98256cc6abdc97701a3b1fa2588e2628180ead2)
---
 clang/lib/Format/UnwrappedLineFormatter.cpp | 12 ++++++++----
 clang/unittests/Format/FormatTest.cpp       |  1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 7ea424349d923..7afc7a46dd1c0 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -983,13 +983,17 @@ class LineJoiner {
         if (!nextTwoLinesFitInto(I, Limit))
           return 0;
 
-        // Second, check that the next line does not contain any braces - if it
-        // does, readability declines when putting it into a single line.
+        // Second, check that the next line does not contain non-braced-init
+        // braces - if it does, readability declines when putting it into a
+        // single line.
         if (I[1]->Last->is(TT_LineComment))
           return 0;
         do {
-          if (Tok->isOneOf(tok::l_brace, tok::r_brace) &&
-              Tok->isNot(BK_BracedInit)) {
+          if (Tok->is(tok::l_brace) && Tok->isNot(BK_BracedInit))
+            return 0;
+          if (Tok->is(tok::r_brace) &&
+              (!Tok->MatchingParen ||
+               Tok->MatchingParen->isNot(BK_BracedInit))) {
             return 0;
           }
           Tok = Tok->Next;
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index ec9ad612832f5..72e0182181763 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -15368,6 +15368,7 @@ TEST_F(FormatTest, CustomShortFunctionOptions) {
   // All functions should be on a single line if they fit
   verifyFormat("int f() { return 42; }", CustomAll);
   verifyFormat("int g() { return f() + h(); }", CustomAll);
+  verifyFormat("pair<int, int> g() { return {1, {}}; }", CustomAll);
   verifyFormat("class C {\n"
                "  int f() { return 42; }\n"
                "};",