9.7 KiB
[temp.dep.constexpr]
13 Templates [temp]
13.8 Name resolution [temp.res]
13.8.3 Dependent names [temp.dep]
13.8.3.4 Value-dependent expressions [temp.dep.constexpr]
Except as described below, an expression used in a context where a constant expression is required is value-dependent if any subexpression is value-dependent.
Anid-expression is value-dependent if
it is a concept-id and its concept-name is dependent or any of its arguments are dependent ([temp.dep.temp]),
it is type-dependent,
it is the name of a constant template parameter,
it is a name introduced by the for-range-declaration of an expansion statement ([stmt.expand]),
it names a static data member that is a dependent member of the current instantiation and is not initialized in a member-declarator,
it names a static member function that is a dependent member of the current instantiation, or
it names a potentially-constant variable ([expr.const]) that is initialized with an expression that is value-dependent.
Expressions of the following form are value-dependent if theunary-expression or expression is type-dependent or thetype-id is dependent:
sizeof unary-expression
sizeof ( type-id )
typeid ( expression )
typeid ( type-id )
alignof ( type-id )
[Note 1:
For the standard library macro offsetof, see [support.types].
â end note]
Expressions of the following form are value-dependent if either thetype-id,simple-type-specifier, ortypename-specifier is dependent or theexpression orcast-expression is value-dependent or any expression in the expression-list is value-dependent or any assignment-expression in the braced-init-list is value-dependent:
simple-type-specifier ( expression-listopt )
typename-specifier ( expression-listopt )
simple-type-specifier braced-init-list
typename-specifier braced-init-list
static_cast < type-id > ( expression )
const_cast < type-id > ( expression )
reinterpret_cast < type-id > ( expression )
dynamic_cast < type-id > ( expression )
( type-id ) cast-expression
Expressions of the following form are value-dependent:
sizeof ... ( identifier )
fold-expression
unless the identifier is a structured binding pack whose initializer is not dependent.
A noexcept-expression ([expr.unary.noexcept]) is value-dependent if its expression involves a template parameter.
An expression of the form &qualified-id where thequalified-id names a dependent member of the current instantiation is value-dependent.
An expression of the form &cast-expression is also value-dependent if evaluating cast-expression as a core constant expression succeeds and the result of the evaluation refers to a templated entity that is an object with static or thread storage duration or a member function.
A reflect-expression is value-dependent if
it is of the form ^^reflection-name and the reflection-name
is a dependent qualified name,
is a dependent namespace-name,
is the name of a template parameter, or
names a dependent member of the current instantiation ([temp.dep.type]),
it is of the form ^^type-id and the type-id denotes a dependent type, or
it is of the form ^^id-expression and the id-expression is value-dependent.
A splice-expression is value-dependent if its splice-specifier orsplice-specialization-specifier is dependent ([temp.dep.splice]).