Cut various sites supporting MSVC <= 2015

Summary: [Folly] Cut various sites supporting MSVC <= 2015, which is insufficiently compatible.

Reviewed By: Orvid

Differential Revision: D13747631

fbshipit-source-id: 3d63d3a57258b5695b1236a81f3ddfe2f4af9cb4

folly/Expected.h

@@ -101,15 +101,8 @@ namespace expected_detail {
 template <typename Value, typename Error>
 struct PromiseReturn;
 
-#ifdef _MSC_VER
-// MSVC 2015 can't handle the StrictConjunction, so we have
-// to use std::conjunction instead.
-template <template <class...> class Trait, class... Ts>
-using StrictAllOf = std::conjunction<Trait<Ts>...>;
-#else
 template <template <class...> class Trait, class... Ts>
 using StrictAllOf = StrictConjunction<Trait<Ts>...>;
-#endif
 
 template <class T>
 using IsCopyable = StrictConjunction<
@@ -244,11 +237,6 @@ struct ExpectedStorage {
   Value&& value() && {
     return std::move(value_);
   }
-  // TODO (t17322426): remove when VS2015 support is deprecated
-  // VS2015 static analyzer incorrectly flags these as unreachable in certain
-  // circumstances. VS2017 does not have this problem on the same code.
-  FOLLY_PUSH_WARNING
-  FOLLY_MSVC_DISABLE_WARNING(4702) // unreachable code
   Error& error() & {
     return error_;
   }
@@ -258,7 +246,6 @@ struct ExpectedStorage {
   Error&& error() && {
     return std::move(error_);
   }
-  FOLLY_POP_WARNING
 };
 
 template <class Value, class Error>
@@ -545,11 +532,6 @@ struct ExpectedStorage<Value, Error, StorageType::ePODStruct> {
   Value&& value() && {
     return std::move(value_);
   }
-  // TODO (t17322426): remove when VS2015 support is deprecated
-  // VS2015 static analyzer incorrectly flags these as unreachable in certain
-  // circumstances. VS2017 does not have this problem on the same code.
-  FOLLY_PUSH_WARNING
-  FOLLY_MSVC_DISABLE_WARNING(4702) // unreachable code
   Error& error() & {
     return error_;
   }
@@ -559,7 +541,6 @@ struct ExpectedStorage<Value, Error, StorageType::ePODStruct> {
   Error&& error() && {
     return std::move(error_);
   }
-  FOLLY_POP_WARNING
 };
 
 namespace expected_detail_ExpectedHelper {

folly/FBString.h

@@ -1248,18 +1248,15 @@ class basic_fbstring {
   // otherwise MSVC 2017 will aggressively pre-resolve value_type to
   // traits_type::char_type, which won't compare as equal when determining
   // which overload the implementation is referring to.
-  // Also note that MSVC 2015 Update 3 requires us to explicitly specify the
-  // namespace in-which to search for basic_fbstring, otherwise it tries to
-  // look for basic_fbstring::basic_fbstring, which is just plain wrong.
   template <typename TP>
   typename std::enable_if<
       std::is_convertible<
           TP,
-          typename folly::basic_fbstring<E, T, A, Storage>::value_type>::
+          typename basic_fbstring<E, T, A, Storage>::value_type>::
               value &&
           !std::is_same<
               typename std::decay<TP>::type,
-              typename folly::basic_fbstring<E, T, A, Storage>::value_type>::
+              typename basic_fbstring<E, T, A, Storage>::value_type>::
               value,
       basic_fbstring<E, T, A, Storage>&>::type
   operator=(TP c) = delete;

folly/Fingerprint.h

@@ -72,7 +72,7 @@ template <int BITS>
 const poly_table<BITS> FingerprintTable<BITS>::table = {};
 
 #ifndef _MSC_VER
-// MSVC 2015 can't handle these extern specialization declarations,
+// MSVC as of 2017 can't handle these extern specialization declarations,
 // but they aren't needed for things to work right, so we just don't
 // declare them in the header for MSVC.
 

folly/Optional.h

@@ -412,17 +412,10 @@ class Optional {
     };
     bool hasValue;
 
-    FOLLY_PUSH_WARNING
-    // These are both informational warnings, but they trigger rare
-    // enough that we've left them enabled. Needed as long as MSVC
-    // 2015 is supported.
-    FOLLY_MSVC_DISABLE_WARNING(4587) // constructor of .value is not called
-    FOLLY_MSVC_DISABLE_WARNING(4588) // destructor of .value is not called
     StorageNonTriviallyDestructible() : hasValue{false} {}
     ~StorageNonTriviallyDestructible() {
       clear();
     }
-    FOLLY_POP_WARNING
 
     void clear() {
       if (hasValue) {

folly/Portability.h

@@ -462,7 +462,7 @@ constexpr auto kCpplibVer = 0;
 //    extern int const num;
 //    FOLLY_STORAGE_CONSTEXPR int const num = 3;
 //
-//  True for MSVC 2015 and MSVC 2017.
+//  True as of MSVC 2017.
 #if _MSC_VER
 #define FOLLY_STORAGE_CONSTEXPR
 #define FOLLY_STORAGE_CPP14_CONSTEXPR

folly/Traits.h

@@ -419,15 +419,15 @@ struct IsLessThanComparable
 
 namespace traits_detail_IsNothrowSwappable {
 #if defined(__cpp_lib_is_swappable) || (_CPPLIB_VER && _HAS_CXX17)
-// MSVC 2015+ already implements the C++17 P0185R1 proposal which
-// adds std::is_nothrow_swappable, so use it instead if C++17 mode
-// is enabled.
+// MSVC already implements the C++17 P0185R1 proposal which adds
+// std::is_nothrow_swappable, so use it instead if C++17 mode is
+// enabled.
 template <typename T>
 using IsNothrowSwappable = std::is_nothrow_swappable<T>;
 #elif _CPPLIB_VER
-// MSVC 2015+ defines the base even if C++17 is disabled, and
-// MSVC 2015 has issues with our fallback implementation due to
-// over-eager evaluation of noexcept.
+// MSVC defines the base even if C++17 is disabled, and MSVC has
+// issues with our fallback implementation due to over-eager
+// evaluation of noexcept.
 template <typename T>
 using IsNothrowSwappable = std::_Is_nothrow_swappable<T>;
 #else

folly/lang/UncaughtExceptions.h

@@ -27,14 +27,7 @@ struct __cxa_eh_globals;
 // declared in cxxabi.h from libstdc++-v3
 extern "C" __cxa_eh_globals* __cxa_get_globals() noexcept;
 } // namespace __cxxabiv1
-#elif defined(_MSC_VER) && (_MSC_VER >= 1400) && \
-    (_MSC_VER < 1900) // MSVC++ 8.0 or greater
-#define FOLLY_EXCEPTION_COUNT_USE_GETPTD
-// forward declaration (originally defined in mtdll.h from MSVCRT)
-struct _tiddata;
-extern "C" _tiddata* _getptd(); // declared in mtdll.h from MSVCRT
-#elif defined(FOLLY_FORCE_EXCEPTION_COUNT_USE_STD) || \
-    (defined(_MSC_VER) && (_MSC_VER >= 1900)) // MSVC++ 2015
+#elif defined(FOLLY_FORCE_EXCEPTION_COUNT_USE_STD) || defined(_MSC_VER)
 #define FOLLY_EXCEPTION_COUNT_USE_STD
 #else
 // Raise an error when trying to use this on unsupported platforms.