Bring back magic constants in the digraph diagnostic

This backs out changes in commit r198605 and part of r198604, replacing the
original tok::kw_template with a slightly more obvious placeholder
tok::unknown.

llvm-svn: 198666
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index f5d5454..9fd6d2a 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -24,6 +24,20 @@
 
 using namespace clang;
 
+static int SelectDigraphErrorMessage(tok::TokenKind Kind) {
+  switch (Kind) {
+    // template name
+    case tok::unknown:             return 0;
+    // casts
+    case tok::kw_const_cast:       return 1;
+    case tok::kw_dynamic_cast:     return 2;
+    case tok::kw_reinterpret_cast: return 3;
+    case tok::kw_static_cast:      return 4;
+    default:
+      llvm_unreachable("Unknown type for digraph error message.");
+  }
+}
+
 // Are the two tokens adjacent in the same source file?
 bool Parser::areTokensAdjacent(const Token &First, const Token &Second) {
   SourceManager &SM = PP.getSourceManager();
@@ -44,7 +58,8 @@
   Range.setBegin(DigraphToken.getLocation());
   Range.setEnd(ColonToken.getLocation());
   P.Diag(DigraphToken.getLocation(), diag::err_missing_whitespace_digraph)
-      << Kind << FixItHint::CreateReplacement(Range, "< ::");
+      << SelectDigraphErrorMessage(Kind)
+      << FixItHint::CreateReplacement(Range, "< ::");
 
   // Update token information to reflect their change in token type.
   ColonToken.setKind(tok::coloncolon);
@@ -80,8 +95,8 @@
                               Template, MemberOfUnknownSpecialization))
     return;
 
-  FixDigraph(*this, PP, Next, SecondToken, tok::annot_template_id,
-             /*AtDigraph*/ false);
+  FixDigraph(*this, PP, Next, SecondToken, tok::unknown,
+             /*AtDigraph*/false);
 }
 
 /// \brief Emits an error for a left parentheses after a double colon.