Fix assertion in constant expression evaluation. The LHS of a floating-point
binary operator isn't an rvalue if it's an assignment operator.

llvm-svn: 143250
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 89bcacf..6e2e15c 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2492,8 +2492,8 @@
     return Visit(E->getRHS());
   }
 
-  // We can't evaluate pointer-to-member operations.
-  if (E->isPtrMemOp())
+  // We can't evaluate pointer-to-member operations or assignments.
+  if (E->isPtrMemOp() || E->isAssignmentOp())
     return false;
 
   // FIXME: Diagnostics?  I really don't understand how the warnings