Code completion: add a lot of infrastructure code

* Added a mode in swift-ide-test to test code completion.  Unlike c-index-test,
  the code completion token in tests is a real token -- we don't need to
  count lines and columns anymore.

* Added support in lexer to produce a code completion token.

* Added a parser interface to code completion.  It is passed down from the
  libFrontend to the parser, but its functions are not called yet.

* Added a sketch of the interface of code completion consumer and code
  completion results.

Note: all this is not doing anything useful yet.


Swift SVN r6128

lib/Parse/Parser.cpp

@@ -20,6 +20,7 @@
 #include "swift/AST/Diagnostics.h"
 #include "swift/AST/PrettyStackTrace.h"
 #include "swift/Parse/Lexer.h"
+#include "swift/Parse/CodeCompletionCallbacks.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/SaveAndRestore.h"
@@ -94,9 +95,23 @@ bool swift::parseIntoTranslationUnit(TranslationUnit *TU,
   return FoundSideEffects;
 }
 
-void swift::performDelayedParsing(TranslationUnit *TU,
-                                  Parser *TheParser) {
-  if (!TU->Ctx.LangOpts.DelayFunctionBodyParsing)
+void swift::performDelayedParsing(
+    TranslationUnit *TU, Parser *TheParser,
+    CodeCompletionCallbacksFactory *CodeCompletionFactory) {
+  bool NeedSecondPass = false;
+  if (TU->Ctx.LangOpts.DelayFunctionBodyParsing)
+    NeedSecondPass = true;
+
+  std::unique_ptr<CodeCompletionCallbacks> CodeCompletion;
+  if (TU->Ctx.LangOpts.isCodeCompletion() && CodeCompletionFactory) {
+    CodeCompletion.reset(
+        CodeCompletionFactory->createCodeCompletionCallbacks(*TheParser));
+    TheParser->setCodeCompletion(TU->Ctx.LangOpts.CodeCompletionOffset,
+                                 CodeCompletion.get());
+    NeedSecondPass = true;
+  }
+
+  if (!NeedSecondPass)
     return;
 
   TheParser->setDelayedParsingSecondPass();