[analyzer] Fix a crash reported in PR 14400.

The AllocaRegion did not have the superRegion (based on LocationContext)
as part of it's hash. As a consequence, the AllocaRegions from
different frames were uniqued to be the same region.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168599 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp b/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
index 6ef022b..24f8cdd 100644
--- a/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
@@ -68,6 +68,7 @@
     DefinedOrUnknownSVal extentMatchesSizeArg =
       svalBuilder.evalEQ(state, Extent, Size);
     state = state->assume(extentMatchesSizeArg, true);
+    assert(state && "The region should not have any previous constraints");
 
     C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
     return true;