Except as described below, an expression is type-dependent if any subexpression is type-dependent.
this is type-dependent if the class type of the enclosing member function is dependent ([temp.dep.type]).
An id-expression is type-dependent if it contains
an identifier associated by name lookup with one or more declarations declared with a dependent type,
an identifier associated by name lookup with a non-type template-parameter declared with a type that contains a placeholder type,
an identifier associated by name lookup with one or more declarations of member functions of the current instantiation declared with a return type that contains a placeholder type,
an identifier associated by name lookup with a structured binding declaration whose brace-or-equal-initializer is type-dependent,
the identifier __func__, where any enclosing function is a template, a member of a class template, or a generic lambda,
a template-id that is dependent,
a conversion-function-id that specifies a dependent type, or
a nested-name-specifier or a qualified-id that names a member of an unknown specialization;
or if it names a dependent member of the current instantiation that is a static data member of type “array of unknown bound of T” for some T ([temp.static]). Expressions of the following forms are type-dependent only if the type specified by the type-id, simple-type-specifier or new-type-id is dependent, even if any subexpression is type-dependent:
simple-type-specifier ( expression-listopt ) ::opt new new-placementopt new-type-id new-initializeropt ::opt new new-placementopt ( type-id ) new-initializeropt dynamic_cast < type-id > ( expression ) static_cast < type-id > ( expression ) const_cast < type-id > ( expression ) reinterpret_cast < type-id > ( expression ) ( type-id ) cast-expression
Expressions of the following forms are never type-dependent (because the type of the expression cannot be dependent):
literal postfix-expression . pseudo-destructor-name postfix-expression -> pseudo-destructor-name sizeof unary-expression sizeof ( type-id ) sizeof ... ( identifier ) alignof ( type-id ) typeid ( expression ) typeid ( type-id ) ::opt delete cast-expression ::opt delete [ ] cast-expression throw assignment-expressionopt noexcept ( expression )
[ Note: For the standard library macro offsetof, see [support.types]. — end note ]
A class member access expression is type-dependent if the expression refers to a member of the current instantiation and the type of the referenced member is dependent, or the class member access expression refers to a member of an unknown specialization. [ Note: In an expression of the form x.y or xp->y the type of the expression is usually the type of the member y of the class of x (or the class pointed to by xp). However, if x or xp refers to a dependent type that is not the current instantiation, the type of y is always dependent. If x or xp refers to a non-dependent type or refers to the current instantiation, the type of y is the type of the class member access expression. — end note ]