[Migrator] Add the simple transformation from global variables to static member variables. (#8865)

This should also handle global string to string enum migration.

lib/Migrator/SyntacticMigratorPass.cpp

@@ -0,0 +1,98 @@
+//===--- SyntacticMigratorPass.cpp ----------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/AST/USRGeneration.h"
+#include "swift/Frontend/Frontend.h"
+#include "swift/Migrator/EditorAdapter.h"
+#include "swift/Migrator/FixitApplyDiagnosticConsumer.h"
+#include "swift/Migrator/Migrator.h"
+#include "swift/Migrator/RewriteBufferEditsReceiver.h"
+#include "swift/Migrator/SyntacticMigratorPass.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Edit/EditedSource.h"
+#include "clang/Rewrite/Core/RewriteBuffer.h"
+#include "llvm/Support/FileSystem.h"
+#include "swift/IDE/APIDigesterData.h"
+
+using namespace swift;
+using namespace swift::migrator;
+using namespace swift::ide::api;
+
+struct SyntacticMigratorPass::Implementation : public SourceEntityWalker {
+  SourceFile *SF;
+  const StringRef FileName;
+  unsigned BufferId;
+  SourceManager &SM;
+  EditorAdapter &Editor;
+  const MigratorOptions &Opts;
+
+  APIDiffItemStore DiffStore;
+
+  ArrayRef<APIDiffItem*> getRelatedDiffItems(ValueDecl *VD) {
+    llvm::SmallString<64> Buffer;
+    llvm::raw_svector_ostream OS(Buffer);
+    if (swift::ide::printDeclUSR(VD, OS))
+      return {};
+    // FIXME: overrides and conformances.
+    return DiffStore.getDiffItems(Buffer.str());
+  }
+
+  bool isSimpleReplacement(APIDiffItem *Item, std::string &Text) {
+    if (auto *MD = dyn_cast<TypeMemberDiffItem>(Item)) {
+      // We need to pull the self if self index is set.
+      if (MD->selfIndex.hasValue())
+        return false;
+      Text = (llvm::Twine(MD->newTypeName) + "." + MD->newPrintedName).str();
+      return true;
+    }
+    return false;
+  }
+
+  Implementation(SourceFile *SF, EditorAdapter &Editor,
+                 const MigratorOptions &Opts) :
+    SF(SF), FileName(SF->getFilename()), BufferId(SF->getBufferID().getValue()),
+      SM(SF->getASTContext().SourceMgr), Editor(Editor), Opts(Opts) {}
+
+  void run() {
+    if (Opts.APIDigesterDataStorePath.empty())
+      return;
+    DiffStore.addStorePath(Opts.APIDigesterDataStorePath);
+    walk(SF);
+  }
+
+  bool visitDeclReference(ValueDecl *D, CharSourceRange Range,
+                          TypeDecl *CtorTyRef, ExtensionDecl *ExtTyRef,
+                          Type T, ReferenceMetaData Data) override {
+    for (auto* Item : getRelatedDiffItems(D)) {
+      std::string RepText;
+      if (isSimpleReplacement(Item, RepText)) {
+        Editor.replace(Range, RepText);
+        return true;
+      }
+    }
+    return true;
+  }
+};
+
+SyntacticMigratorPass::
+SyntacticMigratorPass(EditorAdapter &Editor, SourceFile *SF,
+  const MigratorOptions &Opts) : Impl(*new Implementation(SF, Editor, Opts)) {}
+
+SyntacticMigratorPass::~SyntacticMigratorPass() { delete &Impl; }
+
+void SyntacticMigratorPass::run() { Impl.run(); }
+
+const clang::edit::Commit &SyntacticMigratorPass::getEdits() const {
+  return Impl.Editor.getEdits();
+}