prep for explicit types in Cursor::write

Summary:
Addresses problems like this:

```
void* buf = /*...*/;
uint16_t word = /*...*/;
cursor.write(word & 0xffff); // oops, 32-bit store due to implicit integer promotion
```

Reviewed By: dmm-fb

Differential Revision: D94252971

fbshipit-source-id: 22d05d2bfe6f173e40e4e5dcf81f0bccc74dd1b3

Author: yfeldblum

third-party/fizz/src/fizz/record/Types-inl.h

@@ -82,7 +82,7 @@ struct Writer {
           std::is_enum<T>::value && std::is_same<U, T>::value,
           T>::type& in,
       folly::io::Appender& appender) {
-    using UT = typename std::underlying_type<U>::type;
+    using UT = std::underlying_type_t<U>;
     static_assert(
         std::is_unsigned<UT>::value,
         "enums meant to be serialized should be unsigned");
@@ -233,9 +233,8 @@ inline Status write<Extension>(
     Error& err,
     const Extension& extension,
     folly::io::Appender& out) {
-  out.writeBE(
-      static_cast<typename std::underlying_type<ExtensionType>::type>(
-          extension.extension_type));
+  using UT = std::underlying_type_t<ExtensionType>;
+  out.writeBE(static_cast<UT>(extension.extension_type));
   FIZZ_RETURN_ON_ERROR(writeBuf<uint16_t>(err, extension.extension_data, out));
   return Status::Success;
 }

third-party/proxygen/src/proxygen/lib/http/codec/test/HQFramerTest.h

@@ -19,7 +19,7 @@ size_t writeFrameHeaderManual(folly::IOBufQueue& queue,
                               uint64_t decodedType,
                               uint64_t decodedLength) {
   folly::io::QueueAppender appender(&queue, proxygen::hq::kMaxFrameHeaderSize);
-  auto appenderOp = [&](auto val) { appender.writeBE(val); };
+  auto appenderOp = [&](auto val) { appender.writeBE<decltype(val)>(val); };
   auto typeRes = quic::encodeQuicInteger(decodedType, appenderOp);
   CHECK(typeRes.has_value());
   auto lengthRes = quic::encodeQuicInteger(decodedLength, appenderOp);
@@ -54,7 +54,7 @@ void writeValidFrame(folly::IOBufQueue& queue, proxygen::hq::FrameType type) {
                          ? maybeDataSize
                          : 0));
       folly::io::QueueAppender appender(&queue, *idSize);
-      auto appenderOp = [&](auto val) { appender.writeBE(val); };
+      auto appenderOp = [&](auto val) { appender.writeBE<decltype(val)>(val); };
       auto idResult = quic::encodeQuicInteger(id, appenderOp);
       CHECK(idResult.has_value());
       if (type == proxygen::hq::FrameType::PUSH_PROMISE) {
@@ -84,7 +84,7 @@ void writeValidFrame(folly::IOBufQueue& queue, proxygen::hq::FrameType type) {
           static_cast<uint64_t>(type),
           *prioritizedIdSize + data->computeChainDataLength());
       folly::io::QueueAppender appender(&queue, *prioritizedIdSize);
-      auto appenderOp = [&](auto val) { appender.writeBE(val); };
+      auto appenderOp = [&](auto val) { appender.writeBE<decltype(val)>(val); };
       auto prioritizedIdResult =
           quic::encodeQuicInteger(prioritizedId, appenderOp);
       CHECK(prioritizedIdResult.has_value());