Add simple support for tags in YAML I/O

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194644 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/YAMLTraits.cpp

@@ -81,6 +81,16 @@ bool Input::setCurrentDocument() {
 void Input::nextDocument() {
   ++DocIterator;
 }
+  
+bool Input::mapTag(StringRef Tag, bool Default) {
+  StringRef foundTag = CurrentNode->_node->getVerbatimTag();
+  if (foundTag.empty()) {
+    // If no tag found and 'Tag' is the default, say it was found.
+    return Default;
+  }
+  // Return true iff found tag matches supplied tag.
+  return Tag.equals(foundTag);
+}
 
 void Input::beginMapping() {
   if (EC)
@@ -381,6 +391,14 @@ void Output::beginMapping() {
   NeedsNewLine = true;
 }
 
+bool Output::mapTag(StringRef Tag, bool Use) {
+  if (Use) {
+    this->output(" ");
+    this->output(Tag);
+  }
+  return Use;
+}
+
 void Output::endMapping() {
   StateStack.pop_back();
 }