AK: Simplify constructors and conversions from nullptr_t

Problem:
- Many constructors are defined as `{}` rather than using the ` =
  default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
  instead of requiring the caller to default construct. This violates
  the C++ Core Guidelines suggestion to declare single-argument
  constructors explicit
  (https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).

Solution:
- Change default constructors to use the compiler-provided default
  constructor.
- Remove implicit conversion operators from `nullptr_t` and change
  usage to enforce type consistency without conversion.

6 files changed, 8 insertions, 8 deletions

diff --git a/Kernel/Net/E1000NetworkAdapter.cpp b/Kernel/Net/E1000NetworkAdapter.cpp
index 431e31d3d1..c6b8644432 100644
--- a/Kernel/Net/E1000NetworkAdapter.cpp
+++ b/Kernel/Net/E1000NetworkAdapter.cpp
@@ -457,7 +457,7 @@ void E1000NetworkAdapter::send_raw(ReadonlyBytes payload)
             sti();
             break;
         }
-        m_wait_queue.wait_on(nullptr, "E1000NetworkAdapter");
+        m_wait_queue.wait_on({}, "E1000NetworkAdapter");
     }
 #ifdef E1000_DEBUG
     dbgln("E1000: Sent packet, status is now {:#02x}!", (u8)descriptor.status);
diff --git a/Kernel/Net/IPv4Socket.cpp b/Kernel/Net/IPv4Socket.cpp
index f8c6a3ac2b..2454a2f6df 100644
--- a/Kernel/Net/IPv4Socket.cpp
+++ b/Kernel/Net/IPv4Socket.cpp
@@ -255,7 +255,7 @@ KResultOr<size_t> IPv4Socket::receive_byte_buffered(FileDescription& description
 
         locker.unlock();
         auto unblocked_flags = Thread::FileDescriptionBlocker::BlockFlags::None;
-        auto res = Thread::current()->block<Thread::ReadBlocker>(nullptr, description, unblocked_flags);
+        auto res = Thread::current()->block<Thread::ReadBlocker>({}, description, unblocked_flags);
         locker.lock();
 
         if (!((u32)unblocked_flags & (u32)Thread::FileDescriptionBlocker::BlockFlags::Read)) {
@@ -306,7 +306,7 @@ KResultOr<size_t> IPv4Socket::receive_packet_buffered(FileDescription& descripti
 
         locker.unlock();
         auto unblocked_flags = Thread::FileDescriptionBlocker::BlockFlags::None;
-        auto res = Thread::current()->block<Thread::ReadBlocker>(nullptr, description, unblocked_flags);
+        auto res = Thread::current()->block<Thread::ReadBlocker>({}, description, unblocked_flags);
         locker.lock();
 
         if (!((u32)unblocked_flags & (u32)Thread::FileDescriptionBlocker::BlockFlags::Read)) {
diff --git a/Kernel/Net/LocalSocket.cpp b/Kernel/Net/LocalSocket.cpp
index bb15c43d4f..3ffc370877 100644
--- a/Kernel/Net/LocalSocket.cpp
+++ b/Kernel/Net/LocalSocket.cpp
@@ -192,7 +192,7 @@ KResult LocalSocket::connect(FileDescription& description, Userspace<const socka
     }
 
     auto unblock_flags = Thread::FileDescriptionBlocker::BlockFlags::None;
-    if (Thread::current()->block<Thread::ConnectBlocker>(nullptr, description, unblock_flags).was_interrupted()) {
+    if (Thread::current()->block<Thread::ConnectBlocker>({}, description, unblock_flags).was_interrupted()) {
         set_connect_side_role(Role::None);
         return KResult(-EINTR);
     }
@@ -329,7 +329,7 @@ KResultOr<size_t> LocalSocket::recvfrom(FileDescription& description, UserOrKern
         }
     } else if (!can_read(description, 0)) {
         auto unblock_flags = Thread::FileDescriptionBlocker::BlockFlags::None;
-        if (Thread::current()->block<Thread::ReadBlocker>(nullptr, description, unblock_flags).was_interrupted())
+        if (Thread::current()->block<Thread::ReadBlocker>({}, description, unblock_flags).was_interrupted())
             return KResult(-EINTR);
     }
     if (!has_attached_peer(description) && socket_buffer->is_empty())
diff --git a/Kernel/Net/NetworkTask.cpp b/Kernel/Net/NetworkTask.cpp
index 18318e90f9..0951f6d0c9 100644
--- a/Kernel/Net/NetworkTask.cpp
+++ b/Kernel/Net/NetworkTask.cpp
@@ -114,7 +114,7 @@ void NetworkTask_main(void*)
     for (;;) {
         size_t packet_size = dequeue_packet(buffer, buffer_size, packet_timestamp);
         if (!packet_size) {
-            packet_wait_queue.wait_on(nullptr, "NetworkTask");
+            packet_wait_queue.wait_on({}, "NetworkTask");
             continue;
         }
         if (packet_size < sizeof(EthernetFrameHeader)) {
diff --git a/Kernel/Net/Routing.cpp b/Kernel/Net/Routing.cpp
index 48330b6697..f9547b247f 100644
--- a/Kernel/Net/Routing.cpp
+++ b/Kernel/Net/Routing.cpp
@@ -230,7 +230,7 @@ RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source, c
     adapter->send({ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, request);
 
     Optional<MACAddress> addr;
-    if (!Thread::current()->block<ARPTableBlocker>(nullptr, next_hop_ip, addr).was_interrupted()) {
+    if (!Thread::current()->block<ARPTableBlocker>({}, next_hop_ip, addr).was_interrupted()) {
         if (addr.has_value()) {
 #ifdef ROUTING_DEBUG
             klog() << "Routing: Got ARP response using adapter " << adapter->name().characters() << " for " << next_hop_ip.to_string().characters() << " (" << addr.value().to_string().characters() << ")";
diff --git a/Kernel/Net/TCPSocket.cpp b/Kernel/Net/TCPSocket.cpp
index 5bb4aefaac..638602b8e6 100644
--- a/Kernel/Net/TCPSocket.cpp
+++ b/Kernel/Net/TCPSocket.cpp
@@ -400,7 +400,7 @@ KResult TCPSocket::protocol_connect(FileDescription& description, ShouldBlock sh
     if (should_block == ShouldBlock::Yes) {
         locker.unlock();
         auto unblock_flags = Thread::FileBlocker::BlockFlags::None;
-        if (Thread::current()->block<Thread::ConnectBlocker>(nullptr, description, unblock_flags).was_interrupted())
+        if (Thread::current()->block<Thread::ConnectBlocker>({}, description, unblock_flags).was_interrupted())
             return KResult(-EINTR);
         locker.lock();
         ASSERT(setup_state() == SetupState::Completed);