Simplify HasArgumentTypes in DynamicParser-inl.h (#1086)

Summary:
- `HasArgumentTypes` uses nested `boost::mpl::transform` calls to strip
  reference qualifiers from the function argument types and then another
  `mpl::transform` call to remove `const` qualifiers.
- Replace the nested `mpl::transform` calls to just one call by using
  `folly::remove_cvref`.
Pull Request resolved: https://github.com/facebook/folly/pull/1086

Reviewed By: Orvid

Differential Revision: D14638843

Pulled By: yfeldblum

fbshipit-source-id: 8c360e50ffaba0328aa8e4c86245ce25d45bc01b

folly/experimental/DynamicParser-inl.h

@@ -33,6 +33,7 @@
 #include <boost/mpl/vector.hpp>
 
 #include <folly/Conv.h>
+#include <folly/Traits.h>
 
 namespace folly {
 
@@ -79,17 +80,13 @@ using ArgumentTypes =
     typename ArgumentTypesByKind<IdentifyCallable::getKind<Fn>(), Fn>::type;
 
 // At present, works for lambdas or plain old functions, but can be
-// extended.  The comparison deliberately strips cv-qualifieers and
+// extended.  The comparison deliberately strips cv-qualifiers and
 // reference, leaving that choice up to the caller.
 template <typename Fn, typename... Args>
 struct HasArgumentTypes
     : boost::mpl::template equal<
-          typename boost::mpl::template transform<
-              typename boost::mpl::template transform<
-                  ArgumentTypes<Fn>,
-                  typename std::template remove_reference<boost::mpl::_1>>::
-                  type,
-              typename std::template remove_cv<boost::mpl::_1>>::type,
+          typename boost::mpl::
+              transform<ArgumentTypes<Fn>, remove_cvref<boost::mpl::_1>>::type,
           boost::mpl::vector<Args...>>::type {};
 template <typename... Args>
 using EnableForArgTypes =