diff --git a/quic/core/quic_connection_test.cc b/quic/core/quic_connection_test.cc
index 1a686d9..24faad8 100644
--- a/quic/core/quic_connection_test.cc
+++ b/quic/core/quic_connection_test.cc
@@ -4277,7 +4277,6 @@
   use_tagging_decrypter();
   connection_.SetEncrypter(ENCRYPTION_INITIAL,
                            std::make_unique<TaggingEncrypter>(0x01));
-  QuicPacketNumber packet_number;
   connection_.SendCryptoStreamData();
 
   // Simulate the retransmission alarm firing and the socket blocking.
diff --git a/quic/core/quic_packet_number.cc b/quic/core/quic_packet_number.cc
index b3009ce..6e6804b 100644
--- a/quic/core/quic_packet_number.cc
+++ b/quic/core/quic_packet_number.cc
@@ -8,15 +8,6 @@
 
 namespace quic {
 
-QuicPacketNumber::QuicPacketNumber()
-    : packet_number_(UninitializedPacketNumber()) {}
-
-QuicPacketNumber::QuicPacketNumber(uint64_t packet_number)
-    : packet_number_(packet_number) {
-  DCHECK_NE(UninitializedPacketNumber(), packet_number)
-      << "Use default constructor for uninitialized packet number";
-}
-
 void QuicPacketNumber::Clear() {
   packet_number_ = UninitializedPacketNumber();
 }
@@ -111,9 +102,4 @@
   return os;
 }
 
-// static
-uint64_t QuicPacketNumber::UninitializedPacketNumber() {
-  return std::numeric_limits<uint64_t>::max();
-}
-
 }  // namespace quic
diff --git a/quic/core/quic_packet_number.h b/quic/core/quic_packet_number.h
index 066d49c..8a75149 100644
--- a/quic/core/quic_packet_number.h
+++ b/quic/core/quic_packet_number.h
@@ -21,10 +21,15 @@
 class QUIC_EXPORT_PRIVATE QuicPacketNumber {
  public:
   // Construct an uninitialized packet number.
-  QuicPacketNumber();
+  constexpr QuicPacketNumber() : packet_number_(UninitializedPacketNumber()) {}
+
   // Construct a packet number from uint64_t. |packet_number| cannot equal the
   // sentinel value.
-  explicit QuicPacketNumber(uint64_t packet_number);
+  explicit constexpr QuicPacketNumber(uint64_t packet_number)
+      : packet_number_(packet_number) {
+    DCHECK_NE(UninitializedPacketNumber(), packet_number)
+        << "Use default constructor for uninitialized packet number";
+  }
 
   // Packet number becomes uninitialized after calling this function.
   void Clear();
@@ -80,7 +85,9 @@
   friend inline uint64_t operator-(QuicPacketNumber lhs, QuicPacketNumber rhs);
 
   // The sentinel value representing an uninitialized packet number.
-  static uint64_t UninitializedPacketNumber();
+  static constexpr uint64_t UninitializedPacketNumber() {
+    return std::numeric_limits<uint64_t>::max();
+  }
 
   uint64_t packet_number_;
 };
diff --git a/quic/core/quic_stream_send_buffer.h b/quic/core/quic_stream_send_buffer.h
index 1bccd0f..a1f7ac7 100644
--- a/quic/core/quic_stream_send_buffer.h
+++ b/quic/core/quic_stream_send_buffer.h
@@ -42,7 +42,8 @@
 };
 
 struct QUIC_EXPORT_PRIVATE StreamPendingRetransmission {
-  StreamPendingRetransmission(QuicStreamOffset offset, QuicByteCount length)
+  constexpr StreamPendingRetransmission(QuicStreamOffset offset,
+                                        QuicByteCount length)
       : offset(offset), length(length) {}
 
   // Starting offset of this pending retransmission.
diff --git a/quic/core/quic_types.cc b/quic/core/quic_types.cc
index c584714..6ebc4eb 100644
--- a/quic/core/quic_types.cc
+++ b/quic/core/quic_types.cc
@@ -11,9 +11,6 @@
 
 namespace quic {
 
-QuicConsumedData::QuicConsumedData(size_t bytes_consumed, bool fin_consumed)
-    : bytes_consumed(bytes_consumed), fin_consumed(fin_consumed) {}
-
 std::ostream& operator<<(std::ostream& os, const QuicConsumedData& s) {
   os << "bytes_consumed: " << s.bytes_consumed
      << " fin_consumed: " << s.fin_consumed;
@@ -61,11 +58,6 @@
   return "<invalid>";
 }
 
-WriteResult::WriteResult() : status(WRITE_STATUS_ERROR), bytes_written(0) {}
-
-WriteResult::WriteResult(WriteStatus status, int bytes_written_or_error_code)
-    : status(status), bytes_written(bytes_written_or_error_code) {}
-
 std::ostream& operator<<(std::ostream& os, const WriteResult& s) {
   os << "{ status: " << s.status;
   if (s.status == WRITE_STATUS_OK) {
diff --git a/quic/core/quic_types.h b/quic/core/quic_types.h
index 0146851..f3299d0 100644
--- a/quic/core/quic_types.h
+++ b/quic/core/quic_types.h
@@ -55,7 +55,8 @@
 
 // A struct for functions which consume data payloads and fins.
 struct QUIC_EXPORT_PRIVATE QuicConsumedData {
-  QuicConsumedData(size_t bytes_consumed, bool fin_consumed);
+  constexpr QuicConsumedData(size_t bytes_consumed, bool fin_consumed)
+      : bytes_consumed(bytes_consumed), fin_consumed(fin_consumed) {}
 
   // By default, gtest prints the raw bytes of an object. The bool data
   // member causes this object to have padding bytes, which causes the
@@ -115,8 +116,10 @@
 // A struct used to return the result of write calls including either the number
 // of bytes written or the error code, depending upon the status.
 struct QUIC_EXPORT_PRIVATE WriteResult {
-  WriteResult(WriteStatus status, int bytes_written_or_error_code);
-  WriteResult();
+  constexpr WriteResult(WriteStatus status, int bytes_written_or_error_code)
+      : status(status), bytes_written(bytes_written_or_error_code) {}
+
+  constexpr WriteResult() : WriteResult(WRITE_STATUS_ERROR, 0) {}
 
   bool operator==(const WriteResult& other) const {
     if (status != other.status) {
@@ -478,9 +481,9 @@
 
 // Information about a newly acknowledged packet.
 struct QUIC_EXPORT_PRIVATE AckedPacket {
-  AckedPacket(QuicPacketNumber packet_number,
-              QuicPacketLength bytes_acked,
-              QuicTime receive_timestamp)
+  constexpr AckedPacket(QuicPacketNumber packet_number,
+                        QuicPacketLength bytes_acked,
+                        QuicTime receive_timestamp)
       : packet_number(packet_number),
         bytes_acked(bytes_acked),
         receive_timestamp(receive_timestamp) {}
diff --git a/quic/core/quic_versions.cc b/quic/core/quic_versions.cc
index 4ac7560..e565a99 100644
--- a/quic/core/quic_versions.cc
+++ b/quic/core/quic_versions.cc
@@ -44,11 +44,6 @@
 
 }  // namespace
 
-ParsedQuicVersion::ParsedQuicVersion(HandshakeProtocol handshake_protocol,
-                                     QuicTransportVersion transport_version)
-    : handshake_protocol(handshake_protocol),
-      transport_version(transport_version) {}
-
 bool ParsedQuicVersion::KnowsWhichDecrypterToUse() const {
   return transport_version > QUIC_VERSION_46 ||
          handshake_protocol == PROTOCOL_TLS1_3;
diff --git a/quic/core/quic_versions.h b/quic/core/quic_versions.h
index 3e34cce..8522c67 100644
--- a/quic/core/quic_versions.h
+++ b/quic/core/quic_versions.h
@@ -134,10 +134,12 @@
   HandshakeProtocol handshake_protocol;
   QuicTransportVersion transport_version;
 
-  ParsedQuicVersion(HandshakeProtocol handshake_protocol,
-                    QuicTransportVersion transport_version);
+  constexpr ParsedQuicVersion(HandshakeProtocol handshake_protocol,
+                              QuicTransportVersion transport_version)
+      : handshake_protocol(handshake_protocol),
+        transport_version(transport_version) {}
 
-  ParsedQuicVersion(const ParsedQuicVersion& other)
+  constexpr ParsedQuicVersion(const ParsedQuicVersion& other)
       : handshake_protocol(other.handshake_protocol),
         transport_version(other.transport_version) {}
 
diff --git a/quic/test_tools/simple_session_notifier.cc b/quic/test_tools/simple_session_notifier.cc
index 72a23d7..5ba12c6 100644
--- a/quic/test_tools/simple_session_notifier.cc
+++ b/quic/test_tools/simple_session_notifier.cc
@@ -46,7 +46,6 @@
   StreamState& stream_state = stream_map_.find(id)->second;
   const bool had_buffered_data =
       HasBufferedStreamData() || HasBufferedControlFrames();
-  QuicConsumedData total_consumed(0, false);
   QuicStreamOffset offset = stream_state.bytes_sent;
   QUIC_DVLOG(1) << "WriteOrBuffer stream_id: " << id << " [" << offset << ", "
                 << offset + data_length << "), fin: " << (state != NO_FIN);