Enable parsing C++ names generated by lambda functions.

[wengxt]

Summary

CPlusPlusLanguage::MethodName could not parse demangled name generated
by lambda functions. Fix that and add a regression test.

[labath]

Adding eugene, as he wrote that piece of code. Seems reasonable at a first glance though.

[eugene]

Great change! Thanks making it.

[wengxt]

I don't have commit access. May any one help me to commit?

[eugene]

In D34911#808059, @wengxt wrote:

I don't have commit access. May any one help me to commit?

I'll do it for you.

[eugene]

Jim already did it. Thanks Jim.

source/Plugins/Language/CPlusPlus/CPlusPlusNameParser.h

private:
   bool ConsumeArguments();
 
   // Consumes template arguments enclosed within '<' ... '>'
   bool ConsumeTemplateArgs();
 
   // Consumes '(anonymous namespace)'
   bool ConsumeAnonymousNamespace();
 
+  // Consumes '{lambda ...}'
+  bool ConsumeLambda();
+
   // Consumes operator declaration like 'operator *' or 'operator delete []'
   bool ConsumeOperator();
 
   // Skips 'const' and 'volatile'
   void SkipTypeQualifiers();
 
   // Skips 'const', 'volatile', '&', '&&' in the end of the function.
   void SkipFunctionQualifiers();

source/Plugins/Language/CPlusPlus/CPlusPlusNameParser.cpp

bool CPlusPlusNameParser::ConsumeAnonymousNamespace() {
 
   if (!ConsumeToken(tok::r_paren)) {
     return false;
   }
   start_position.Remove();
   return true;
 }
 
+bool CPlusPlusNameParser::ConsumeLambda() {
+  Bookmark start_position = SetBookmark();
+  if (!ConsumeToken(tok::l_brace)) {
+    return false;
+  }
+  constexpr llvm::StringLiteral g_lambda("lambda");
+  if (HasMoreTokens() && Peek().is(tok::raw_identifier) &&
+      Peek().getRawIdentifier() == g_lambda) {
+    // Put the matched brace back so we can use ConsumeBrackets
+    TakeBack();
+  } else {
+    return false;
+  }
+
+  if (!ConsumeBrackets(tok::l_brace, tok::r_brace)) {
+    return false;
+  }
+
+  start_position.Remove();
+  return true;
+}
+
 bool CPlusPlusNameParser::ConsumeBrackets(tok::TokenKind left,
                                           tok::TokenKind right) {
   Bookmark start_position = SetBookmark();
   if (!HasMoreTokens() || Peek().getKind() != left)
     return false;
   Advance();
 
   int counter = 1;
case tok::l_paren: {
         continue_parsing = false;
         break;
       }
       l_paren_position.Remove();
       last_coloncolon_position = coloncolon_position;
       state = State::AfterTwoColons;
       break;
     }
+    case tok::l_brace:
+      if (state == State::Beginning || state == State::AfterTwoColons) {
+        if (ConsumeLambda()) {
+          state = State::AfterIdentifier;
+          break;
+        }
+      }
+      continue_parsing = false;
+      break;
     case tok::coloncolon: // Type nesting delimiter.
       if (state != State::Beginning && state != State::AfterIdentifier &&
           state != State::AfterTemplate) {
         continue_parsing = false;
         break;
       }
       last_coloncolon_position = GetCurrentPosition();
       Advance();

unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp

TestCase test_cases[] = {
       {"SAEC::checkFunction(context&) const::CallBack::CallBack(int)",
        "SAEC::checkFunction(context&) const::CallBack", "CallBack", "(int)", "",
        "SAEC::checkFunction(context&) const::CallBack::CallBack"},
       // Anonymous namespace
       {"XX::(anonymous namespace)::anon_class::anon_func() const",
        "XX::(anonymous namespace)::anon_class", "anon_func", "()", "const",
        "XX::(anonymous namespace)::anon_class::anon_func"},
 
+      // Lambda
+      {"main::{lambda()#1}::operator()() const::{lambda()#1}::operator()() const",
+       "main::{lambda()#1}::operator()() const::{lambda()#1}", "operator()", "()", "const",
+       "main::{lambda()#1}::operator()() const::{lambda()#1}::operator()"},
+
       // Function pointers
       {"string (*f(vector<int>&&))(float)", "", "f", "(vector<int>&&)", "",
        "f"},
       {"void (*&std::_Any_data::_M_access<void (*)()>())()", "std::_Any_data",
        "_M_access<void (*)()>", "()", "",
        "std::_Any_data::_M_access<void (*)()>"},
       {"void (*(*(*(*(*(*(*(* const&func1(int))())())())())())())())()", "",
        "func1", "(int)", "", "func1"},