💬 ชาวเน็ตแห่แชร์: dcl.type.simple

The simple type specifiers are

simple-type-specifier:
nested-name-specifier

_{o p t}

type-name
nested-name-specifier template simple-template-id
computed-type-specifier
placeholder-type-specifier
nested-name-specifier

_{o p t}

simple-template-name
pack-index-template-name
char
char8_t
char16_t
char32_t
wchar_t
bool
short
int
long
signed
unsigned
float
double
void

type-name:
class-name
enum-name
typedef-name

computed-type-specifier:
decltype-specifier
pack-index-specifier
splice-type-specifier

2

#

The component names of a simple-type-specifier are those of its nested-name-specifier, type-name, simple-template-id, simple-template-name, and/or type-constraint (if it is a placeholder-type-specifier).

The component name of a type-name is the first name in it.

3

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A placeholder-type-specifier is a placeholder for a type to be deduced ([dcl.spec.auto]).

A type-specifier is a placeholder for a deduced class type ([dcl.type.class.deduct]) if

(3.1)
it is of the form typename $_{o p t}$ nested-name-specifier $_{o p t}$ simple-template-name, or
(3.2)
it is of the form typename $_{o p t}$ pack-index-template-name, or
(3.3)
it is of the form typename $_{o p t}$ splice-specifier and the splice-specifier designates a class template or alias template.

The nested-name-specifier or splice-specifier, if any, shall be non-dependent and the simple-template-name, pack-index-template-name, or splice-specifier shall designate a deducible template.

A deducible template is

(3.4)
a class template,
(3.5)
a type template template parameter, or
(3.6)
an alias template A whose defining-type-id is of the form
typename $_{o p t}$ nested-name-specifier $_{o p t}$ template $_{o p t}$ simple-template-id
where the nested-name-specifier (if any) is non-dependent and the template-name of the simple-template-id names a deducible template other than a type template template parameter of A.

[Note 1:

An injected-class-name is never interpreted as a template-name in contexts where class template argument deduction would be performed ([temp.local]).

— end note]

The other simple-type-specifiers specify either a previously-declared type, a type determined from an expression, or one of the fundamental types ([basic.fundamental]).

Table 17 summarizes the valid combinations of simple-type-specifiers and the types they specify.

Table 17 — simple-type-specifiers and the types they specify [tab:dcl.type.simple]

🔗 Specifier(s)	Type
🔗 type-name	the type named
🔗 simple-template-id	the type as defined in [temp.names]
🔗 decltype-specifier	the type as defined in [dcl.type.decltype]
🔗 pack-index-specifier	the type as defined in [dcl.type.pack.index]
🔗 placeholder-type-specifier	the type as defined in [dcl.spec.auto]
🔗 template-name	the type as defined in [dcl.type.class.deduct]
🔗 splice-type-specifier	the type as defined in [dcl.type.splice]
🔗 char	“char”
🔗 unsigned char	“unsigned char”
🔗 signed char	“signed char”
🔗 char8_t	“char8_t”
🔗 char16_t	“char16_t”
🔗 char32_t	“char32_t”
🔗 bool	“bool”
🔗 unsigned	“unsigned int”
🔗 unsigned int	“unsigned int”
🔗 signed	“int”
🔗 signed int	“int”
🔗 int	“int”
🔗 unsigned short int	“unsigned short int”
🔗 unsigned short	“unsigned short int”
🔗 unsigned long int	“unsigned long int”
🔗 unsigned long	“unsigned long int”
🔗 unsigned long long int	“unsigned long long int”
🔗 unsigned long long	“unsigned long long int”
🔗 signed long int	“long int”
🔗 signed long	“long int”
🔗 signed long long int	“long long int”
🔗 signed long long	“long long int”
🔗 long long int	“long long int”
🔗 long long	“long long int”
🔗 long int	“long int”
🔗 long	“long int”
🔗 signed short int	“short int”
🔗 signed short	“short int”
🔗 short int	“short int”
🔗 short	“short int”
🔗 wchar_t	“wchar_t”
🔗 float	“float”
🔗 double	“double”
🔗 long double	“long double”
🔗 void	“void”

4

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When multiple simple-type-specifiers are allowed, they can be freely intermixed with other decl-specifiers in any order.

[Note 2:

It is implementation-defined whether objects of char type are represented as signed or unsigned quantities.

The signed specifier forces char objects to be signed; it is redundant in other contexts.

— end note]

9 Declarations [dcl]

9.2 Specifiers [dcl.spec]

9.2.9 Type specifiers [dcl.type]

9.2.9.3 Simple type specifiers [dcl.type.simple]