[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 ([dcl.attr.grammar]):

Table 5 — Keywords

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

[ 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]