message: [SwiftREPL] Initialize the request evaluator only once.
  <rdar://problem/54196650>
diff: @@ -547,12 +547,13 @@ int SwiftREPL::CompleteCode(const std::string &current_code,
  m_target.GetScratchTypeSystemForLanguage(&error, eLanguageTypeSwift));
  if (target_swift_ast)
  m_swift_ast_sp.reset(new SwiftASTContext(*target_swift_ast));
  + swift::registerIDERequestFunctions(
  + m_swift_ast_sp.get()->GetASTContext()->evaluator);
  }
  SwiftASTContext *swift_ast = m_swift_ast_sp.get();
  if (swift_ast) {
  swift::ASTContext *ast = swift_ast->GetASTContext();
  - swift::registerIDERequestFunctions(ast->evaluator);
  swift::REPLCompletions completions;
  SourceModule completion_module_info;
  completion_module_info.path.push_back(ConstString("repl"));
  