[analyzer] Minor: Simplify & assert.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146792 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h

@@ -34,7 +34,10 @@ public:
     : Eng(eng),
       Pred(pred),
       Location(loc),
-      NB(builder) {}
+      NB(builder) {
+    assert(Pred->getState() &&
+           "We should not call the checkers on an empty state.");
+  }
 
   AnalysisManager &getAnalysisManager() {
     return Eng.getAnalysisManager();

lib/StaticAnalyzer/Core/ProgramState.cpp

@@ -692,8 +692,8 @@ bool ProgramState::isTainted(const Stmt *S, TaintTagType Kind) const {
 bool ProgramState::isTainted(SVal V, TaintTagType Kind) const {
   if (const SymExpr *Sym = V.getAsSymExpr())
     return isTainted(Sym, Kind);
-  if (loc::MemRegionVal *RegVal = dyn_cast<loc::MemRegionVal>(&V))
-    return isTainted(RegVal->getRegion(), Kind);
+  if (const MemRegion *Reg = V.getAsRegion())
+    return isTainted(Reg, Kind);
   return false;
 }