fix duplicated symbols for dynamic::TypeInfo members

Summary:
while compiling on windows see duplicated symbols:
```
lld-link: error: duplicate symbol:
public: static char const *const folly::dynamic::TypeInfo<
class std::basic_string<char, struct std::char_traits<char>,
class std::allocator<char>>>::name
in buck-out\dev\gen\crypto\cat\cpp\tests\crypto_auth_token_util_test#compile-CryptoAuthTokenUtilTest.cpp.obj1f5bc0bc,windows-x86_64\out.obj
and in libdynamic.lib(out.obj)
```

Reviewed By: yfeldblum

Differential Revision: D20426321

fbshipit-source-id: 4e0346c624ad12561adb14f3a2e5f6e15bbbba26

folly/dynamic-inl.h

@@ -1003,21 +1003,21 @@ inline dynamic::dynamic(Array&& r) : type_(ARRAY) {
   new (&u_.array) Array(std::move(r));
 }
 
-#define FOLLY_DYNAMIC_DEC_TYPEINFO(T, str, val) \
-  template <>                                   \
-  struct dynamic::TypeInfo<T> {                 \
-    static constexpr const char* name = str;    \
-    static constexpr dynamic::Type type = val;  \
-  };                                            \
+#define FOLLY_DYNAMIC_DEC_TYPEINFO(T, val)     \
+  template <>                                  \
+  struct dynamic::TypeInfo<T> {                \
+    static const char* const name;             \
+    static constexpr dynamic::Type type = val; \
+  };                                           \
   //
 
-FOLLY_DYNAMIC_DEC_TYPEINFO(std::nullptr_t, "null", dynamic::NULLT)
-FOLLY_DYNAMIC_DEC_TYPEINFO(bool, "boolean", dynamic::BOOL)
-FOLLY_DYNAMIC_DEC_TYPEINFO(std::string, "string", dynamic::STRING)
-FOLLY_DYNAMIC_DEC_TYPEINFO(dynamic::Array, "array", dynamic::ARRAY)
-FOLLY_DYNAMIC_DEC_TYPEINFO(double, "double", dynamic::DOUBLE)
-FOLLY_DYNAMIC_DEC_TYPEINFO(int64_t, "int64", dynamic::INT64)
-FOLLY_DYNAMIC_DEC_TYPEINFO(dynamic::ObjectImpl, "object", dynamic::OBJECT)
+FOLLY_DYNAMIC_DEC_TYPEINFO(std::nullptr_t, dynamic::NULLT)
+FOLLY_DYNAMIC_DEC_TYPEINFO(bool, dynamic::BOOL)
+FOLLY_DYNAMIC_DEC_TYPEINFO(std::string, dynamic::STRING)
+FOLLY_DYNAMIC_DEC_TYPEINFO(dynamic::Array, dynamic::ARRAY)
+FOLLY_DYNAMIC_DEC_TYPEINFO(double, dynamic::DOUBLE)
+FOLLY_DYNAMIC_DEC_TYPEINFO(int64_t, dynamic::INT64)
+FOLLY_DYNAMIC_DEC_TYPEINFO(dynamic::ObjectImpl, dynamic::OBJECT)
 
 #undef FOLLY_DYNAMIC_DEC_TYPEINFO
 

folly/dynamic.cpp

@@ -30,18 +30,17 @@ namespace folly {
 
 //////////////////////////////////////////////////////////////////////
 
-#define FOLLY_DYNAMIC_DEF_TYPEINFO(T)                 \
-  constexpr const char* dynamic::TypeInfo<T>::name;   \
-  constexpr dynamic::Type dynamic::TypeInfo<T>::type; \
+#define FOLLY_DYNAMIC_DEF_TYPEINFO(T, str)            \
+  const char* const dynamic::TypeInfo<T>::name = str; \
   //
 
-FOLLY_DYNAMIC_DEF_TYPEINFO(std::nullptr_t)
-FOLLY_DYNAMIC_DEF_TYPEINFO(bool)
-FOLLY_DYNAMIC_DEF_TYPEINFO(std::string)
-FOLLY_DYNAMIC_DEF_TYPEINFO(dynamic::Array)
-FOLLY_DYNAMIC_DEF_TYPEINFO(double)
-FOLLY_DYNAMIC_DEF_TYPEINFO(int64_t)
-FOLLY_DYNAMIC_DEF_TYPEINFO(dynamic::ObjectImpl)
+FOLLY_DYNAMIC_DEF_TYPEINFO(std::nullptr_t, "null")
+FOLLY_DYNAMIC_DEF_TYPEINFO(bool, "boolean")
+FOLLY_DYNAMIC_DEF_TYPEINFO(std::string, "string")
+FOLLY_DYNAMIC_DEF_TYPEINFO(dynamic::Array, "array")
+FOLLY_DYNAMIC_DEF_TYPEINFO(double, "double")
+FOLLY_DYNAMIC_DEF_TYPEINFO(int64_t, "int64")
+FOLLY_DYNAMIC_DEF_TYPEINFO(dynamic::ObjectImpl, "object")
 
 #undef FOLLY_DYNAMIC_DEF_TYPEINFO