[clang-format] Ensure we can correctly parse lambda in the template argument list

https://github.com/llvm/llvm-project/issues/46505

The presence of a lambda in an argument template list ignored the [] as a lambda at all, this caused the contents of the <> to be incorrectly analyzed.

```
struct Y : X < [] {
  return 0;
} > {};
```
Fixes: #46505

Reviewed By: curdeius

Differential Revision: https://reviews.llvm.org/D116806

2 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index c293c236193c..410cce79a087 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2874,6 +2874,8 @@ void UnwrappedLineParser::parseRecord(bool ParseAsExpr) {
         if (!tryToParseBracedList())
           break;
       }
+      if (FormatTok->is(tok::l_square) && !tryToParseLambda())
+        break;
       if (FormatTok->Tok.is(tok::semi))
         return;
       if (Style.isCSharp() && FormatTok->is(Keywords.kw_where)) {
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 85ce3171bbc8..d3e4479a5aa8 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -23212,6 +23212,15 @@ TEST_F(FormatTest, EmptyShortBlock) {
                Style);
 }
 
+TEST_F(FormatTest, ShortTemplatedArgumentLists) {
+  auto Style = getLLVMStyle();
+
+  verifyFormat("struct Y : X<[] { return 0; }> {};", Style);
+  verifyFormat("struct Y<[] { return 0; }> {};", Style);
+
+  verifyFormat("struct Z : X<decltype([] { return 0; }){}> {};", Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang