[clang-format] Fix a crash on parsing requires clause

[owenca]

Fixes #124921.

[llvmbot]

@llvm/pr-subscribers-clang-format

Author: Owen Pan (owenca)

Changes

Fixes #124921.

---

Full diff: https://github.com/llvm/llvm-project/pull/125021.diff

2 Files Affected:

• (modified) clang/lib/Format/UnwrappedLineParser.cpp (+1-1)
• (modified) clang/unittests/Format/FormatTest.cpp (+3)

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 906fc11a07d5ee9..120922d271aab74 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 57f12221cdc7e66..30f3533ac73f72f 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) {

[mydeveloperday]

LGTM

[owenca]

/cherry-pick 14178de

[llvmbot]

/pull-request #126843