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.

1 files changed, 3 insertions, 3 deletions

diff --git a/Kernel/FileSystem/Plan9FileSystem.cpp b/Kernel/FileSystem/Plan9FileSystem.cpp
index e466847524..52051bd253 100644
--- a/Kernel/FileSystem/Plan9FileSystem.cpp
+++ b/Kernel/FileSystem/Plan9FileSystem.cpp
@@ -531,7 +531,7 @@ KResult Plan9FS::post_message(Message& message, RefPtr<ReceiveCompletion> comple
     while (size > 0) {
         if (!description.can_write()) {
             auto unblock_flags = Thread::FileBlocker::BlockFlags::None;
-            if (Thread::current()->block<Thread::WriteBlocker>(nullptr, description, unblock_flags).was_interrupted())
+            if (Thread::current()->block<Thread::WriteBlocker>({}, description, unblock_flags).was_interrupted())
                 return KResult(-EINTR);
         }
         auto data_buffer = UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>(data));
@@ -552,7 +552,7 @@ KResult Plan9FS::do_read(u8* data, size_t size)
     while (size > 0) {
         if (!description.can_read()) {
             auto unblock_flags = Thread::FileBlocker::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);
         }
         auto data_buffer = UserOrKernelBuffer::for_kernel_buffer(data);
@@ -621,7 +621,7 @@ KResult Plan9FS::post_message_and_wait_for_a_reply(Message& message)
     auto result = post_message(message, completion);
     if (result.is_error())
         return result;
-    if (Thread::current()->block<Plan9FS::Blocker>(nullptr, *this, message, completion).was_interrupted())
+    if (Thread::current()->block<Plan9FS::Blocker>({}, *this, message, completion).was_interrupted())
         return KResult(-EINTR);
 
     if (completion->result.is_error()) {