[lex.key]

The identifiers shown in Table 5 are reserved for use as keywords (that is, they are unconditionally treated as keywords in phase 7) except in an attribute-token:

Table 5 — Keywords

alignas	const_cast	for	public	thread_local
alignof	continue	friend	register	throw
asm	decltype	goto	reinterpret_cast	true
auto	default	if	requires	try
bool	delete	inline	return	typedef
break	do	int	short	typeid
case	double	long	signed	typename
catch	dynamic_cast	mutable	sizeof	union
char	else	namespace	static	unsigned
char16_t	enum	new	static_assert	using
char32_t	explicit	noexcept	static_cast	virtual
class	export	nullptr	struct	void
concept	extern	operator	switch	volatile
const	false	private	template	wchar_t
constexpr	float	protected	this	while

[ Note

The export and register keywords are unused but are reserved for future use.

— end note

]

Furthermore, the alternative representations shown in Table 6 for certain operators and punctuators ([lex.digraph]) are reserved and shall not be used otherwise:

Table 6 — Alternative representations

and	and_eq	bitand	bitor	compl	not
not_eq	or	or_eq	xor	xor_eq

5 Lexical conventions [lex]

5.11 Keywords [lex.key]