[lldb] Fix CXX's SymbolNameFitsToLanguage matching other languages

The current implementation of
CPlusPlusLanguage::SymbolNameFitsToLanguage will return true if there is
any mangling scheme for the symbol, not just C++.

rdar://158352104

Author: augusto2112

lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

@@ -105,7 +105,8 @@ CPlusPlusLanguage::GetFunctionNameInfo(ConstString name) const {
 
 bool CPlusPlusLanguage::SymbolNameFitsToLanguage(Mangled mangled) const {
   const char *mangled_name = mangled.GetMangledName().GetCString();
-  return mangled_name && Mangled::IsMangledName(mangled_name);
+  return mangled_name && Mangled::GetManglingScheme(mangled_name) ==
+                             Mangled::eManglingSchemeItanium;
 }
 
 ConstString CPlusPlusLanguage::GetDemangledFunctionNameWithoutArguments(

lldb/unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp

@@ -397,3 +397,16 @@ TEST(CPlusPlusLanguage, CPlusPlusNameParser) {
   // Don't crash.
   CPlusPlusNameParser((const char *)nullptr);
 }
+
+TEST(CPlusPlusLanguage, DoesNotMatchCxx) {
+  // Test that a symbol name that is NOT C++ does not match C++.
+
+  SubsystemRAII<CPlusPlusLanguage> lang;
+  Language *CPlusPlusLang =
+      Language::FindPlugin(lldb::eLanguageTypeC_plus_plus);
+
+  EXPECT_TRUE(CPlusPlusLang != nullptr);
+
+  Mangled swiftSymbol("$sS");
+  EXPECT_FALSE(CPlusPlusLang->SymbolNameFitsToLanguage(swiftSymbol));
+}