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, 2 insertions, 2 deletions

diff --git a/Kernel/Thread.cpp b/Kernel/Thread.cpp
index 17849bd191..871187b45b 100644
--- a/Kernel/Thread.cpp
+++ b/Kernel/Thread.cpp
@@ -316,13 +316,13 @@ void Thread::relock_process(LockMode previous_locked, u32 lock_count_to_restore)
 auto Thread::sleep(clockid_t clock_id, const timespec& duration, timespec* remaining_time) -> BlockResult
 {
     ASSERT(state() == Thread::Running);
-    return Thread::current()->block<Thread::SleepBlocker>(nullptr, Thread::BlockTimeout(false, &duration, nullptr, clock_id), remaining_time);
+    return Thread::current()->block<Thread::SleepBlocker>({}, Thread::BlockTimeout(false, &duration, nullptr, clock_id), remaining_time);
 }
 
 auto Thread::sleep_until(clockid_t clock_id, const timespec& deadline) -> BlockResult
 {
     ASSERT(state() == Thread::Running);
-    return Thread::current()->block<Thread::SleepBlocker>(nullptr, Thread::BlockTimeout(true, &deadline, nullptr, clock_id));
+    return Thread::current()->block<Thread::SleepBlocker>({}, Thread::BlockTimeout(true, &deadline, nullptr, clock_id));
 }
 
 const char* Thread::state_string() const