[TypeCategory] IsApplicable doesn't seem to apply.

[davide]

Please don't merge this yet. I'm mostly trying to understand if this is dead code or not.

@jingham , this is one of the places in generic code where we hardcode knowledge about the languages. Needless to say, it causes conflicts downstream and feels wrong anyway.
After some amount of yak shaving I realized this is not quite used. What do you think about it? I thought this might be needed for some sort of filtering on language but I really can't seem to be able to trigger it on a testcase [or reading the code].

[clayborg]

This seems like it will make a lot more work happen. Many C++ formatters are regex based and are quite expensive to compare against type names. Seems worthwhile to skip if the language doesn't match?

[davide]

Nevermind, I found a better way.

lldb/include/lldb/DataFormatters/TypeCategory.h

public:
   const char *GetName() { return m_name.GetCString(); }
 
   size_t GetNumLanguages();
 
   lldb::LanguageType GetLanguageAtIndex(size_t idx);
 
   void AddLanguage(lldb::LanguageType lang);
 
-  bool HasLanguage(lldb::LanguageType lang);
-
   std::string GetDescription();
 
   bool AnyMatches(ConstString type_name,
                   FormatCategoryItems items = ALL_ITEM_TYPES,
                   bool only_enabled = true,
                   const char **matching_category = nullptr,
                   FormatCategoryItems *matching_type = nullptr);
 

lldb/source/DataFormatters/TypeCategory.cpp

TypeCategoryImpl::TypeCategoryImpl(IFormatChangeListener *clist,
                                    ConstString name)
     : m_format_cont("format", "regex-format", clist),
       m_summary_cont("summary", "regex-summary", clist),
       m_filter_cont("filter", "regex-filter", clist),
       m_synth_cont("synth", "regex-synth", clist),
       m_validator_cont("validator", "regex-validator", clist), m_enabled(false),
       m_change_listener(clist), m_mutex(), m_name(name), m_languages() {}
 
-static bool IsApplicable(lldb::LanguageType category_lang,
-                         lldb::LanguageType valobj_lang) {
-  switch (category_lang) {
-  // Unless we know better, allow only exact equality.
-  default:
-    return category_lang == valobj_lang;
-
-  // the C family, we consider it as one
-  case eLanguageTypeC89:
-  case eLanguageTypeC:
-  case eLanguageTypeC99:
-    return valobj_lang == eLanguageTypeC89 || valobj_lang == eLanguageTypeC ||
-           valobj_lang == eLanguageTypeC99;
-
-  // ObjC knows about C and itself
-  case eLanguageTypeObjC:
-    return valobj_lang == eLanguageTypeC89 || valobj_lang == eLanguageTypeC ||
-           valobj_lang == eLanguageTypeC99 || valobj_lang == eLanguageTypeObjC;
-
-  // C++ knows about C and C++
-  case eLanguageTypeC_plus_plus:
-    return valobj_lang == eLanguageTypeC89 || valobj_lang == eLanguageTypeC ||
-           valobj_lang == eLanguageTypeC99 ||
-           valobj_lang == eLanguageTypeC_plus_plus;
-
-  // ObjC++ knows about C,C++,ObjC and ObjC++
-  case eLanguageTypeObjC_plus_plus:
-    return valobj_lang == eLanguageTypeC89 || valobj_lang == eLanguageTypeC ||
-           valobj_lang == eLanguageTypeC99 ||
-           valobj_lang == eLanguageTypeC_plus_plus ||
-           valobj_lang == eLanguageTypeObjC;
-
-  // Categories with unspecified language match everything.
-  case eLanguageTypeUnknown:
-    return true;
-  }
-}
-
-bool TypeCategoryImpl::IsApplicable(ValueObject &valobj) {
-  lldb::LanguageType valobj_lang = valobj.GetObjectRuntimeLanguage();
-  for (size_t idx = 0; idx < GetNumLanguages(); idx++) {
-    const lldb::LanguageType category_lang = GetLanguageAtIndex(idx);
-    if (::IsApplicable(category_lang, valobj_lang))
-      return true;
-  }
-  return false;
-}
-
 size_t TypeCategoryImpl::GetNumLanguages() {
   if (m_languages.empty())
     return 1;
   return m_languages.size();
 }
 
 lldb::LanguageType TypeCategoryImpl::GetLanguageAtIndex(size_t idx) {
   if (m_languages.empty())
     return lldb::eLanguageTypeUnknown;
   return m_languages[idx];
 }
 
 void TypeCategoryImpl::AddLanguage(lldb::LanguageType lang) {
   m_languages.push_back(lang);
 }
 
-bool TypeCategoryImpl::HasLanguage(lldb::LanguageType lang) {
-  const auto iter = std::find(m_languages.begin(), m_languages.end(), lang),
-             end = m_languages.end();
-  return (iter != end);
-}
-
 bool TypeCategoryImpl::Get(ValueObject &valobj,
                            const FormattersMatchVector &candidates,
                            lldb::TypeFormatImplSP &entry, uint32_t *reason) {
-  if (!IsEnabled() || !IsApplicable(valobj))
+  if (!IsEnabled())
     return false;
   if (GetTypeFormatsContainer()->Get(candidates, entry, reason))
     return true;
   bool regex = GetRegexTypeFormatsContainer()->Get(candidates, entry, reason);
   if (regex && reason)
     *reason |= lldb_private::eFormatterChoiceCriterionRegularExpressionSummary;
   return regex;
 }
 
 bool TypeCategoryImpl::Get(ValueObject &valobj,
                            const FormattersMatchVector &candidates,
                            lldb::TypeSummaryImplSP &entry, uint32_t *reason) {
-  if (!IsEnabled() || !IsApplicable(valobj))
+  if (!IsEnabled())
     return false;
   if (GetTypeSummariesContainer()->Get(candidates, entry, reason))
     return true;
   bool regex = GetRegexTypeSummariesContainer()->Get(candidates, entry, reason);
   if (regex && reason)
     *reason |= lldb_private::eFormatterChoiceCriterionRegularExpressionSummary;
   return regex;
 }
 
 bool TypeCategoryImpl::Get(ValueObject &valobj,
                            const FormattersMatchVector &candidates,
                            lldb::SyntheticChildrenSP &entry, uint32_t *reason) {
-  if (!IsEnabled() || !IsApplicable(valobj))
+  if (!IsEnabled())
     return false;
   TypeFilterImpl::SharedPointer filter_sp;
   uint32_t reason_filter = 0;
   bool regex_filter = false;
   // first find both Filter and Synth, and then check which is most recent
 
   if (!GetTypeFiltersContainer()->Get(candidates, filter_sp, &reason_filter))
     regex_filter = GetRegexTypeFiltersContainer()->Get(candidates, filter_sp,