AK: Use direct-list-initialization for Vector::empend() (SerenityOS#4564

)

clang trunk with -std=c++20 doesn't seem to properly look for an
aggregate initializer here when the type being constructed is a simple
aggregate (e.g. `struct Thing { int a; int b; };`). This template fails
to compile in a usage added 12/16/2020 in `AK/Trie.h`.

Both forms of initialization are supposed to call the
aggregate-initializers but direct-list-initialization delegating to
aggregate initializers is a new addition in c++20 that might not be
implemented yet.

AK/Vector.h

@@ -398,7 +398,7 @@ class Vector {
  void empend(Args&&... args)
  {
  grow_capacity(m_size + 1);
- new (slot(m_size)) T(forward<Args>(args)...);
+ new (slot(m_size)) T { forward<Args>(args)... };
  ++m_size;
  }
 

Kernel/FileSystem/Ext2FileSystem.cpp

@@ -1433,8 +1433,8 @@ KResult Ext2FS::create_directory(InodeIdentifier parent_id, const String& name,
 #endif
 
  Vector<Ext2FSDirectoryEntry> entries;
- entries.empend(".", inode->identifier(), EXT2_FT_DIR);
- entries.empend("..", parent_id, EXT2_FT_DIR);
+ entries.empend(".", inode->identifier(), static_cast<u8>(EXT2_FT_DIR));
+ entries.empend("..", parent_id, static_cast<u8>(EXT2_FT_DIR));
 
  bool success = static_cast<Ext2FSInode&>(*inode).write_directory(entries);
  ASSERT(success);

Libraries/LibRegex/RegexByteCode.h

@@ -191,7 +191,7 @@ class ByteCode : public Vector<ByteCodeValueType> {
  ByteCode bytecode;
 
  bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::Compare));
- bytecode.empend(1); // number of arguments
+ bytecode.empend(static_cast<u64>(1)); // number of arguments
 
  ByteCode arguments;
 
@@ -209,7 +209,7 @@ class ByteCode : public Vector<ByteCodeValueType> {
  ByteCode bytecode;
 
  bytecode.empend(static_cast<ByteCodeValueType>(OpCodeId::Compare));
- bytecode.empend(1); // number of arguments
+ bytecode.empend(static_cast<u64>(1)); // number of arguments
 
  ByteCode arguments;
 

Services/LookupServer/DNSRequest.cpp

@@ -32,7 +32,7 @@
 #include <ctype.h>
 #include <stdlib.h>
 
-#define C_IN 1
+const u16 C_IN = 1;
 
 DNSRequest::DNSRequest()
  : m_id(arc4random_uniform(UINT16_MAX))