[clang][dataflow] Make `Value` and `StorageLocation` non-copyable

[sgatev]

Summary

This makes it harder to misuse APIs that return references by
accidentally copying the results which could happen when assigning the
them to variables declared as auto.

[ymandel]

Thanks!

clang/include/clang/Analysis/FlowSensitive/StorageLocation.h

 /// Each storage location holds a value. The mapping from storage locations to
 /// values is stored in the environment.
 class StorageLocation {
 public:
   enum class Kind { Scalar, Aggregate };
 
   StorageLocation(Kind LocKind, QualType Type) : LocKind(LocKind), Type(Type) {}
 
+  // Non-copyable because addresses of storage locations are used as their
+  // identities throughout framework and user code. The framework is responsible
+  // for construction and destruction of storage locations.
+  StorageLocation(const StorageLocation &) = delete;
+  StorageLocation &operator=(const StorageLocation &) = delete;
+
   virtual ~StorageLocation() = default;
 
   Kind getKind() const { return LocKind; }
 
   QualType getType() const { return Type; }
 
 private:
   Kind LocKind;

clang/include/clang/Analysis/FlowSensitive/Value.h

enum class Kind {
     AtomicBool,
     Conjunction,
     Disjunction,
     Negation
   };
 
   explicit Value(Kind ValKind) : ValKind(ValKind) {}
 
+  // Non-copyable because addresses of values are used as their identities
+  // throughout framework and user code. The framework is responsible for
+  // construction and destruction of values.
+  Value(const Value &) = delete;
+  Value &operator=(const Value &) = delete;
+
   virtual ~Value() = default;
 
   Kind getKind() const { return ValKind; }
 
   /// Returns the value of the synthetic property with the given `Name` or null
   /// if the property isn't assigned a value.
   Value *getProperty(llvm::StringRef Name) const {
     auto It = Properties.find(Name);