[clang] [clang-format] Fix for BreakTemplateDeclarations and RequiresClausePosition (PR #159261)

[NagaChaitanya Vellanki via cfe-commits]

https://github.com/chaitanyav updated https://github.com/llvm/llvm-project/pull/159261

>From ec7a0a72497882f18940d71af3911a31b819f9ef Mon Sep 17 00:00:00 2001
From: NagaChaitanya Vellanki <pnagato at protonmail.com>
Date: Wed, 17 Sep 2025 00:04:24 -0700
Subject: [PATCH] [clang-format] Fix for BreakTemplateDeclarations and
 RequiresClausePosition

               when BreakTemplateDeclarations is set to yes and
               RequiresClausePosition is SingleLine or WithPreceding
               requires clause should be on the same line
Fixes #150845
---
 clang/lib/Format/TokenAnnotator.cpp   |  5 +++++
 clang/unittests/Format/FormatTest.cpp | 13 +++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index d97f56751ea69..f22c51af7d3f1 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -5854,6 +5854,11 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
     // concept ...
     if (Right.is(tok::kw_concept))
       return Style.BreakBeforeConceptDeclarations == FormatStyle::BBCDS_Always;
+    if (Right.is(TT_RequiresClause) &&
+        (Style.RequiresClausePosition == FormatStyle::RCPS_WithPreceding ||
+         Style.RequiresClausePosition == FormatStyle::RCPS_SingleLine)) {
+      return false;
+    }
     return Style.BreakTemplateDeclarations == FormatStyle::BTDS_Yes ||
            (Style.BreakTemplateDeclarations == FormatStyle::BTDS_Leave &&
             Right.NewlinesBefore > 0);
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index d9db06667d802..efbc86af72c17 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -10848,6 +10848,19 @@ TEST_F(FormatTest, WrapsTemplateDeclarations) {
                "public:\n"
                "  E *f();\n"
                "};");
+  Style.RequiresClausePosition = FormatStyle::RCPS_SingleLine;
+  verifyNoChange("template <typename T> requires std::floating_point<T>\n"
+                 "using LerpValue = ClampedValue<T, T{ 0 }, T{ 1 }>;",
+                 Style);
+  Style.RequiresClausePosition = FormatStyle::RCPS_WithPreceding;
+  verifyNoChange("template <typename T> requires std::floating_point<T>\n"
+                 "using LerpValue = ClampedValue<T, T{ 0 }, T{ 1 }>;",
+                 Style);
+  Style.RequiresClausePosition = FormatStyle::RCPS_OwnLine;
+  verifyFormat("template <typename T>\n"
+               "requires std::floating_point<T>\n"
+               "using LerpValue = ClampedValue<T, T{ 0 }, T{ 1 }>;",
+               Style);
 
   FormatStyle NeverBreak = getLLVMStyle();
   NeverBreak.BreakTemplateDeclarations = FormatStyle::BTDS_No;