[clang-format] Don't misannotate left squares as lambda introducers

[owenpan]

Summary

A left square can start a lambda only if it's not preceded by an identifier other than return and co-wait/co-yield/co-return.

Fixes https://github.com/llvm/llvm-project/issues/54245.
Fixes https://github.com/llvm/llvm-project/issues/61786.

[rymiel]

This is great!

[MyDeveloperDay]

LGTM

[owenpan]

In D147295#4235648, @rymiel wrote:

This is great!

Thanks!

clang/lib/Format/UnwrappedLineParser.cpp

bool UnwrappedLineParser::tryToParseLambda() {
   parseChildBlock();
   return true;
 }
 
 bool UnwrappedLineParser::tryToParseLambdaIntroducer() {
   const FormatToken *Previous = FormatTok->Previous;
   const FormatToken *LeftSquare = FormatTok;
   nextToken();
-  if (Previous &&
-      (Previous->isOneOf(tok::identifier, tok::kw_operator, tok::kw_new,
-                         tok::kw_delete, tok::l_square) ||
-       LeftSquare->isCppStructuredBinding(Style) || Previous->closesScope() ||
-       Previous->isSimpleTypeSpecifier())) {
+  if ((Previous && ((Previous->Tok.getIdentifierInfo() &&
+                     !Previous->isOneOf(tok::kw_return, tok::kw_co_await,
+                                        tok::kw_co_yield, tok::kw_co_return)) ||
+                    Previous->closesScope())) ||
+      LeftSquare->isCppStructuredBinding(Style)) {
     return false;
   }
   if (FormatTok->is(tok::l_square))
     return false;
   if (FormatTok->is(tok::r_square)) {
     const FormatToken *Next = Tokens->peekNextToken(/*SkipComment=*/true);
     if (Next->is(tok::greater))
       return false;
do {
       }
       if (FormatTok->is(tok::l_square)) {
         FormatToken *Previous = FormatTok->Previous;
         if (!Previous ||
             !(Previous->is(tok::r_paren) || Previous->isTypeOrIdentifier())) {
           // Don't try parsing a lambda if we had a closing parenthesis before,
           // it was probably a pointer to an array: int (*)[].
           if (!tryToParseLambda())
-            break;
+            continue;
         } else {
           parseSquare();
           continue;
         }
       }
       if (FormatTok->is(tok::semi))
         return;
       if (Style.isCSharp() && FormatTok->is(Keywords.kw_where)) {

clang/unittests/Format/TokenAnnotatorTest.cpp

TEST_F(TokenAnnotatorTest, UnderstandsStructs) {
 
   Tokens = annotate("struct EXPORT_MACRO [[nodiscard]] C { int i; };");
   EXPECT_EQ(Tokens.size(), 15u) << Tokens;
   EXPECT_TOKEN(Tokens[8], tok::l_brace, TT_StructLBrace);
 
   Tokens = annotate("struct [[deprecated]] [[nodiscard]] C { int i; };");
   EXPECT_EQ(Tokens.size(), 19u) << Tokens;
   EXPECT_TOKEN(Tokens[12], tok::l_brace, TT_StructLBrace);
+
+  Tokens = annotate("template <typename T> struct S<const T[N]> {};");
+  EXPECT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[7], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[10], tok::l_square, TT_ArraySubscriptLSquare);
+  EXPECT_TOKEN(Tokens[13], tok::greater, TT_TemplateCloser);
+  EXPECT_TOKEN(Tokens[14], tok::l_brace, TT_StructLBrace);
+
+  Tokens = annotate("template <typename T> struct S<T const[N]> {};");
+  EXPECT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[7], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[10], tok::l_square, TT_ArraySubscriptLSquare);
+  EXPECT_TOKEN(Tokens[13], tok::greater, TT_TemplateCloser);
+  EXPECT_TOKEN(Tokens[14], tok::l_brace, TT_StructLBrace);
+
+  Tokens = annotate("template <typename T, unsigned n> struct S<T const[n]> {\n"
+                    "  void f(T const (&a)[n]);\n"
+                    "};");
+  EXPECT_EQ(Tokens.size(), 35u) << Tokens;
+  EXPECT_TOKEN(Tokens[10], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[13], tok::l_square, TT_ArraySubscriptLSquare);
+  EXPECT_TOKEN(Tokens[16], tok::greater, TT_TemplateCloser);
+  EXPECT_TOKEN(Tokens[17], tok::l_brace, TT_StructLBrace);
+  EXPECT_TOKEN(Tokens[23], tok::l_paren, TT_FunctionTypeLParen);
+  EXPECT_TOKEN(Tokens[24], tok::amp, TT_UnaryOperator);
+  EXPECT_TOKEN(Tokens[27], tok::l_square, TT_ArraySubscriptLSquare);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsUnions) {
   auto Tokens = annotate("union U {};");
   EXPECT_EQ(Tokens.size(), 6u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_brace, TT_UnionLBrace);
 
   Tokens = annotate("union U { void f() { return; } };");
TEST_F(TokenAnnotatorTest, UnderstandsObjCBlock) {
 
   Tokens = annotate("int *p = ^int*(){ //\n"
                     "  return nullptr;\n"
                     "}();");
   ASSERT_EQ(Tokens.size(), 19u) << Tokens;
   EXPECT_TOKEN(Tokens[9], tok::l_brace, TT_ObjCBlockLBrace);
 }
 
+TEST_F(TokenAnnotatorTest, UnderstandsObjCMethodExpr) {
+  auto Tokens = annotate("void f() {\n"
+                         "  //\n"
+                         "  BOOL a = [b.c n] > 1;\n"
+                         "}");
+  EXPECT_EQ(Tokens.size(), 20u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::l_square, TT_ObjCMethodExpr);
+  EXPECT_TOKEN(Tokens[15], tok::greater, TT_BinaryOperator);
+}
+
 TEST_F(TokenAnnotatorTest, UnderstandsLambdas) {
   auto Tokens = annotate("[]() constexpr {}");
   ASSERT_EQ(Tokens.size(), 8u) << Tokens;
   EXPECT_TOKEN(Tokens[0], tok::l_square, TT_LambdaLSquare);
   EXPECT_TOKEN(Tokens[5], tok::l_brace, TT_LambdaLBrace);
 
   Tokens = annotate("[]() consteval {}");
   ASSERT_EQ(Tokens.size(), 8u) << Tokens;