[llvm-branch-commits] [clang] release/20.x: [clang-format] Fix a crash on parsing requires clause (#125021) (PR #126843)

[via llvm-branch-commits]

https://github.com/llvmbot updated https://github.com/llvm/llvm-project/pull/126843

>From a7f00c8ed8c20a006fd7e592e99f3ca7b725b07e Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Thu, 30 Jan 2025 18:03:04 -0800
Subject: [PATCH] [clang-format] Fix a crash on parsing requires clause
 (#125021)

Fixes #124921.

(cherry picked from commit 14178deab0334d9ce095ae7adce408868659faee)
---
 clang/lib/Format/UnwrappedLineParser.cpp | 2 +-
 clang/unittests/Format/FormatTest.cpp    | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 906fc11a07d5e..120922d271aab 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -3632,7 +3632,7 @@ void UnwrappedLineParser::parseRequiresClause(FormatToken *RequiresToken) {
   // It could be inlined into here.
   parseConstraintExpression();
 
-  if (!InRequiresExpression)
+  if (!InRequiresExpression && FormatTok->Previous)
     FormatTok->Previous->ClosesRequiresClause = true;
 }
 
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 57f12221cdc7e..30f3533ac73f7 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -26478,6 +26478,9 @@ TEST_F(FormatTest, RequiresClauses) {
                "foo();\n"
                "#endif\n"
                "bar(requires);");
+
+  verifyNoCrash("template <class T>\n"
+                "    requires(requires { std::declval<T>()");
 }
 
 TEST_F(FormatTest, RequiresExpressionIndentation) {