Create ConstantExpr class

A ConstantExpr class represents a full expression that's in a context where a
constant expression is required. This class reflects the path the evaluator
took to reach the expression rather than the syntactic context in which the
expression occurs.

In the future, the class will be expanded to cache the result of the evaluated
expression so that it's not needlessly re-evaluated

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D53475

llvm-svn: 345692
diff --git a/clang/lib/AST/ExprCXX.cpp b/clang/lib/AST/ExprCXX.cpp
index f14f5a3..00a4607 100644
--- a/clang/lib/AST/ExprCXX.cpp
+++ b/clang/lib/AST/ExprCXX.cpp
@@ -1044,12 +1044,7 @@
 ExprWithCleanups::ExprWithCleanups(Expr *subexpr,
                                    bool CleanupsHaveSideEffects,
                                    ArrayRef<CleanupObject> objects)
-    : Expr(ExprWithCleanupsClass, subexpr->getType(),
-           subexpr->getValueKind(), subexpr->getObjectKind(),
-           subexpr->isTypeDependent(), subexpr->isValueDependent(),
-           subexpr->isInstantiationDependent(),
-           subexpr->containsUnexpandedParameterPack()),
-      SubExpr(subexpr) {
+    : FullExpr(ExprWithCleanupsClass, subexpr) {
   ExprWithCleanupsBits.CleanupsHaveSideEffects = CleanupsHaveSideEffects;
   ExprWithCleanupsBits.NumObjects = objects.size();
   for (unsigned i = 0, e = objects.size(); i != e; ++i)
@@ -1066,7 +1061,7 @@
 }
 
 ExprWithCleanups::ExprWithCleanups(EmptyShell empty, unsigned numObjects)
-    : Expr(ExprWithCleanupsClass, empty) {
+    : FullExpr(ExprWithCleanupsClass, empty) {
   ExprWithCleanupsBits.NumObjects = numObjects;
 }