PODness and Type Traits

Make C++ classes track the POD property (C++ [class]p4)
Track the existence of a copy assignment operator.
Implicitly declare the copy assignment operator if none is provided.
Implement most of the parsing job for the G++ type traits extension.
Fully implement the low-hanging fruit of the type traits:
__is_pod: Whether a type is a POD.
__is_class: Whether a type is a (non-union) class.
__is_union: Whether a type is a union.
__is_enum: Whether a type is an enum.
__is_polymorphic: Whether a type is polymorphic (C++ [class.virtual]p1).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61746 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 6cfcdc4..eafa717 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -1092,6 +1092,10 @@
   case CXXDefaultArgExprClass:
     return cast<CXXDefaultArgExpr>(this)
              ->isIntegerConstantExpr(Result, Ctx, Loc, isEvaluated);
+
+  case UnaryTypeTraitExprClass:
+    Result = cast<UnaryTypeTraitExpr>(this)->Evaluate();
+    return true;
   }
 
   // Cases that are valid constant exprs fall through to here.