[clang-format] Fix a bug in annotating lambda l_square (#95084)

Fixes #95072.

Author: owenca

clang/lib/Format/UnwrappedLineParser.cpp

@@ -2257,6 +2257,8 @@ bool UnwrappedLineParser::tryToParseLambda() {
       break;
     case tok::kw_auto:
     case tok::kw_class:
+    case tok::kw_struct:
+    case tok::kw_union:
     case tok::kw_template:
     case tok::kw_typename:
     case tok::amp:

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -1655,6 +1655,12 @@ TEST_F(TokenAnnotatorTest, UnderstandsLambdas) {
   EXPECT_TOKEN(Tokens[2], tok::arrow, TT_TrailingReturnArrow);
   EXPECT_TOKEN(Tokens[4], tok::l_brace, TT_LambdaLBrace);
 
+  Tokens = annotate("[] -> struct S { return {}; }");
+  ASSERT_EQ(Tokens.size(), 12u) << Tokens;
+  EXPECT_TOKEN(Tokens[0], tok::l_square, TT_LambdaLSquare);
+  EXPECT_TOKEN(Tokens[2], tok::arrow, TT_TrailingReturnArrow);
+  EXPECT_TOKEN(Tokens[5], tok::l_brace, TT_LambdaLBrace);
+
   Tokens = annotate("foo([&](u32 bar) __attribute__((attr)) -> void {});");
   ASSERT_EQ(Tokens.size(), 22u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_square, TT_LambdaLSquare);