[Basic] Extend DiagnosticEngine to store and format Qualifiers.
 
Qualifiers can now be streamed into the DiagnosticEngine using
regular << operator. If Qualifiers are empty 'unqualified' will
be printed in the diagnostic otherwise regular qual syntax is
used.

Differential Revision: https://reviews.llvm.org/D56198

llvm-svn: 350386
diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index 50d2d29..dd05855 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -334,6 +334,20 @@
 
   switch (Kind) {
     default: llvm_unreachable("unknown ArgumentKind");
+    case DiagnosticsEngine::ak_qual: {
+      assert(Modifier.empty() && Argument.empty() &&
+             "Invalid modifier for Qualfiers argument");
+
+      Qualifiers Q(Qualifiers::fromOpaqueValue(Val));
+      auto S = Q.getAsString();
+      if (S.empty()) {
+        OS << "unqualified";
+        NeedQuotes = false;
+      } else {
+        OS << Q.getAsString();
+      }
+      break;
+    }
     case DiagnosticsEngine::ak_qualtype_pair: {
       TemplateDiffTypes &TDT = *reinterpret_cast<TemplateDiffTypes*>(Val);
       QualType FromType =