[clang-format] Fix a crash on parsing requires clause (#125021)

owenca · tstellar · commit a7f00c8ed8c2 · 2025-02-13T18:38:24.000-08:00
Fixes #124921. (cherry picked from commit 14178de)
diff --git 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
@@ -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) {

Original file line number	Diff line number	Diff line change
`@@ -3632,7 +3632,7 @@ void UnwrappedLineParser::parseRequiresClause(FormatToken *RequiresToken) {`
`3632`	`3632`	`// It could be inlined into here.`
`3633`	`3633`	`parseConstraintExpression();`
`3634`	`3634`
`3635`		`- if (!InRequiresExpression)`
	`3635`	`+ if (!InRequiresExpression && FormatTok->Previous)`
`3636`	`3636`	`FormatTok->Previous->ClosesRequiresClause = true;`
`3637`	`3637`	`}`
`3638`	`3638`
Original file line number	Diff line number	Diff line change
`@@ -26478,6 +26478,9 @@ TEST_F(FormatTest, RequiresClauses) {`
`26478`	`26478`	`"foo();\n"`
`26479`	`26479`	`"#endif\n"`
`26480`	`26480`	`"bar(requires);");`
	`26481`	`+`
	`26482`	`+ verifyNoCrash("template <class T>\n"`
	`26483`	`+ " requires(requires { std::declval<T>()");`
`26481`	`26484`	`}`
`26482`	`26485`
`26483`	`26486`	`TEST_F(FormatTest, RequiresExpressionIndentation) {`