[analyzer] CastValueChecker: Correctly model results of based-to-derived casts.

Our SVal hierarchy doesn't allow modeling pointer casts as no-op. The
pointer type is instead encoded into the pointer object. Defer to our
usual pointer casting facility, SValBuilder::evalBinOp().

Fixes a crash.

llvm-svn: 369729
diff --git a/clang/test/Analysis/cast-value-logic.cpp b/clang/test/Analysis/cast-value-logic.cpp
index 5317728..221ae7f 100644
--- a/clang/test/Analysis/cast-value-logic.cpp
+++ b/clang/test/Analysis/cast-value-logic.cpp
@@ -19,7 +19,11 @@
   virtual double area();
 };
 class Triangle : public Shape {};
-class Circle : public Shape {};
+class Circle : public Shape {
+public:
+  ~Circle();
+};
+class SuspiciouslySpecificCircle : public Circle {};
 } // namespace clang
 
 using namespace llvm;
@@ -149,4 +153,10 @@
     return S->area();
   return S->area() / 2;
 }
+
+void test_delete_crash() {
+  extern Circle *makeCircle();
+  Shape *S = makeCircle();
+  delete cast<SuspiciouslySpecificCircle>(S);
+}
 } // namespace crashes