Extend FindTypes with CompilerContext to allow filtering by language.

This patch is also motivated by the Swift branch and is effectively NFC for the single-TypeSystem llvm.org branch.

In multi-language projects it is extremely common to have, e.g., a
Clang type and a similarly-named rendition of that same type in
another language. When searching for a type It is much cheaper to pass
a set of supported languages to the SymbolFile than having it
materialize every result and then rejecting the materialized types
that have the wrong language.

Differential Revision: https://reviews.llvm.org/D66546

<rdar://problem/54471165>

This reapplies r369690 with a previously missing constructor for LanguageSet.

llvm-svn: 369710
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index 43b19fb..d1d9a73 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -734,32 +734,36 @@
   return lldb::TypeSystemSP();
 }
 
-void ClangASTContext::EnumerateSupportedLanguages(
-    std::set<lldb::LanguageType> &languages_for_types,
-    std::set<lldb::LanguageType> &languages_for_expressions) {
-  static std::vector<lldb::LanguageType> s_supported_languages_for_types(
-      {lldb::eLanguageTypeC89, lldb::eLanguageTypeC, lldb::eLanguageTypeC11,
-       lldb::eLanguageTypeC_plus_plus, lldb::eLanguageTypeC99,
-       lldb::eLanguageTypeObjC, lldb::eLanguageTypeObjC_plus_plus,
-       lldb::eLanguageTypeC_plus_plus_03, lldb::eLanguageTypeC_plus_plus_11,
-       lldb::eLanguageTypeC11, lldb::eLanguageTypeC_plus_plus_14});
+LanguageSet ClangASTContext::GetSupportedLanguagesForTypes() {
+  LanguageSet languages;
+  languages.Insert(lldb::eLanguageTypeC89);
+  languages.Insert(lldb::eLanguageTypeC);
+  languages.Insert(lldb::eLanguageTypeC11);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus);
+  languages.Insert(lldb::eLanguageTypeC99);
+  languages.Insert(lldb::eLanguageTypeObjC);
+  languages.Insert(lldb::eLanguageTypeObjC_plus_plus);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_03);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_11);
+  languages.Insert(lldb::eLanguageTypeC11);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_14);
+  return languages;
+}
 
-  static std::vector<lldb::LanguageType> s_supported_languages_for_expressions(
-      {lldb::eLanguageTypeC_plus_plus, lldb::eLanguageTypeObjC_plus_plus,
-       lldb::eLanguageTypeC_plus_plus_03, lldb::eLanguageTypeC_plus_plus_11,
-       lldb::eLanguageTypeC_plus_plus_14});
-
-  languages_for_types.insert(s_supported_languages_for_types.begin(),
-                             s_supported_languages_for_types.end());
-  languages_for_expressions.insert(
-      s_supported_languages_for_expressions.begin(),
-      s_supported_languages_for_expressions.end());
+LanguageSet ClangASTContext::GetSupportedLanguagesForExpressions() {
+  LanguageSet languages;
+  languages.Insert(lldb::eLanguageTypeC_plus_plus);
+  languages.Insert(lldb::eLanguageTypeObjC_plus_plus);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_03);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_11);
+  languages.Insert(lldb::eLanguageTypeC_plus_plus_14);
+  return languages;
 }
 
 void ClangASTContext::Initialize() {
-  PluginManager::RegisterPlugin(GetPluginNameStatic(),
-                                "clang base AST context plug-in",
-                                CreateInstance, EnumerateSupportedLanguages);
+  PluginManager::RegisterPlugin(
+      GetPluginNameStatic(), "clang base AST context plug-in", CreateInstance,
+      GetSupportedLanguagesForTypes(), GetSupportedLanguagesForExpressions());
 }
 
 void ClangASTContext::Terminate() {