[analyzer][NFC] Use MemRegion::getRegion()'s return value unconditionally

[steakhal]

arc used the HEAD^ as base, so I'm setting the parent patches now.

[steakhal]

Well, my first use of arc went a bit sideways, so I'm falling back to posting this NFC patch batch manually.
We will see how using arc works out next time.

[steakhal]

Until this point, the runtime and reports of the Clang Static Analyzer did not change on our testset; which confirms that the stack is indeed NFC.

[martong]

Is it documented with getRegion? Could we decorate that with returns-nonnull https://clang.llvm.org/docs/AttributeReference.html#returns-nonnull ?

[steakhal]

In D126123#3531112, @martong wrote:

Is it documented with getRegion? Could we decorate that with returns-nonnull https://clang.llvm.org/docs/AttributeReference.html#returns-nonnull ?

Ah, I thought one of my changes addressing this was already on review.
It turns out it was not the case. Now I uploaded it for review: D126198

[martong]

In D126123#3531150, @steakhal wrote:

In D126123#3531112, @martong wrote:

Is it documented with getRegion? Could we decorate that with returns-nonnull https://clang.llvm.org/docs/AttributeReference.html#returns-nonnull ?

Ah, I thought one of my changes addressing this was already on review.
It turns out it was not the case. Now I uploaded it for review: D126198

Ok, could you please change the title of this Differential Revision? Something is still not fitting.

clang/lib/StaticAnalyzer/Core/SVals.cpp

 } // end anonymous namespace
 
 QualType SVal::getType(const ASTContext &Context) const {
   TypeRetrievingVisitor TRV{Context};
   return TRV.Visit(*this);
 }
 
 const MemRegion *loc::MemRegionVal::stripCasts(bool StripBaseCasts) const {
-  const MemRegion *R = getRegion();
-  return R ?  R->StripCasts(StripBaseCasts) : nullptr;
+  return getRegion()->StripCasts(StripBaseCasts);
 }
 
 const void *nonloc::LazyCompoundVal::getStore() const {
   return static_cast<const LazyCompoundValData*>(Data)->getStore();
 }
 
 const TypedValueRegion *nonloc::LazyCompoundVal::getRegion() const {
   return static_cast<const LazyCompoundValData*>(Data)->getRegion();