[IDE/CodeCompletion] Register the request evaluator.

Author: Davide Italiano

lib/Frontend/Frontend.cpp

@@ -190,9 +190,12 @@ bool CompilerInstance::setUpASTContextIfNeeded() {
   registerTypeCheckerRequestFunctions(Context->evaluator);
 
   // Migrator, indexing and typo correction need some IDE requests.
+  // The integrated REPL needs IDE requests for completion.
   if (Invocation.getMigratorOptions().shouldRunMigrator() ||
       !Invocation.getFrontendOptions().IndexStorePath.empty() ||
-      Invocation.getLangOptions().TypoCorrectionLimit) {
+      Invocation.getLangOptions().TypoCorrectionLimit ||
+      Invocation.getFrontendOptions().RequestedAction ==
+          FrontendOptions::ActionType::REPL) {
     registerIDERequestFunctions(Context->evaluator);
   }
   if (setUpModuleLoaders())