[clang] [clang-format] Disalbe IntegerLiteralSeparator for C++ before c++14 (PR #151273)

[Owen Pan via cfe-commits]

https://github.com/owenca updated https://github.com/llvm/llvm-project/pull/151273

>From 9fab68a7aa71e6ffe6ad6476359a21884b084576 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Tue, 29 Jul 2025 21:09:46 -0700
Subject: [PATCH] [clang-format] Disalbe IntegerLiteralSeparator for C++ before
 c++14

Fixes #151102
---
 clang/lib/Format/IntegerLiteralSeparatorFixer.cpp     | 11 +++++++----
 .../unittests/Format/IntegerLiteralSeparatorTest.cpp  |  3 +++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Format/IntegerLiteralSeparatorFixer.cpp b/clang/lib/Format/IntegerLiteralSeparatorFixer.cpp
index 80487fa673bf0..7772a5619c4bd 100644
--- a/clang/lib/Format/IntegerLiteralSeparatorFixer.cpp
+++ b/clang/lib/Format/IntegerLiteralSeparatorFixer.cpp
@@ -45,15 +45,18 @@ std::pair<tooling::Replacements, unsigned>
 IntegerLiteralSeparatorFixer::process(const Environment &Env,
                                       const FormatStyle &Style) {
   switch (Style.Language) {
-  case FormatStyle::LK_Cpp:
-  case FormatStyle::LK_ObjC:
-    Separator = '\'';
-    break;
   case FormatStyle::LK_CSharp:
   case FormatStyle::LK_Java:
   case FormatStyle::LK_JavaScript:
     Separator = '_';
     break;
+  case FormatStyle::LK_Cpp:
+  case FormatStyle::LK_ObjC:
+    if (Style.Standard >= FormatStyle::LS_Cpp14) {
+      Separator = '\'';
+      break;
+    }
+    [[fallthrough]];
   default:
     return {};
   }
diff --git a/clang/unittests/Format/IntegerLiteralSeparatorTest.cpp b/clang/unittests/Format/IntegerLiteralSeparatorTest.cpp
index 8681c3d2f89ce..53b6dd8efadff 100644
--- a/clang/unittests/Format/IntegerLiteralSeparatorTest.cpp
+++ b/clang/unittests/Format/IntegerLiteralSeparatorTest.cpp
@@ -83,6 +83,9 @@ TEST_F(IntegerLiteralSeparatorTest, SingleQuoteAsSeparator) {
                "d = 5678_km;\n"
                "h = 0xDEF_u16;",
                Style);
+
+  Style.Standard = FormatStyle::LS_Cpp11;
+  verifyFormat("ld = 1234L;", Style);
 }
 
 TEST_F(IntegerLiteralSeparatorTest, UnderscoreAsSeparator) {