Add "typedef T value_type;" to llvm::Optional<T>.

[jordan_rose]

Summary

For convenience. No functionality change.

[dblaikie]

I assume this is part of std::experimental::optional?

Looks good to me, especially if that's the case.

[jordan_rose]

That's correct. Committed as r218617.

include/llvm/ADT/Optional.h

 
 namespace llvm {
 
 template<typename T>
 class Optional {
   AlignedCharArrayUnion<T> storage;
   bool hasVal;
 public:
+  typedef T value_type;
+
   Optional(NoneType) : hasVal(false) {}
   explicit Optional() : hasVal(false) {}
   Optional(const T &y) : hasVal(true) {
     new (storage.buffer) T(y);
   }
   Optional(const Optional &O) : hasVal(O.hasVal) {
     if (hasVal)
       new (storage.buffer) T(*O);