Use more explicit type names in ElementProxy

Summary:
`T` here is defined in a `using` declaration in the class body, which is
in a different file.  MSVC doesn't recognize this.  Using the full type
here is more verbose, but also a bit clearer since `T` is defined elsewhere.

Reviewed By: passy

Differential Revision: D23820252

fbshipit-source-id: 60efaecc369c2497e4a68dece09c9350bd792324

first-party/fbjni/cxx/fbjni/detail/CoreClasses-inl.h

@@ -364,13 +364,13 @@ inline ElementProxy<Target>& ElementProxy<Target>::operator=(const T& o) {
 }
 
 template<typename Target>
-inline ElementProxy<Target>& ElementProxy<Target>::operator=(alias_ref<T>& o) {
+inline ElementProxy<Target>& ElementProxy<Target>::operator=(alias_ref<typename Target::javaentry>& o) {
   target_->setElement(idx_, o.get());
   return *this;
 }
 
 template<typename Target>
-inline ElementProxy<Target>& ElementProxy<Target>::operator=(alias_ref<T>&& o) {
+inline ElementProxy<Target>& ElementProxy<Target>::operator=(alias_ref<typename Target::javaentry>&& o) {
   target_->setElement(idx_, o.get());
   return *this;
 }
@@ -383,12 +383,12 @@ inline ElementProxy<Target>& ElementProxy<Target>::operator=(const ElementProxy<
 }
 
 template<typename Target>
-inline ElementProxy<Target>::ElementProxy::operator const local_ref<T> () const {
+inline ElementProxy<Target>::ElementProxy::operator const local_ref<typename Target::javaentry> () const {
   return target_->getElement(idx_);
 }
 
 template<typename Target>
-inline ElementProxy<Target>::ElementProxy::operator local_ref<T> () {
+inline ElementProxy<Target>::ElementProxy::operator local_ref<typename Target::javaentry> () {
   return target_->getElement(idx_);
 }
 }