7 Expressions [expr]

7.5 Primary expressions [expr.prim]

7.5.2 This [expr.prim.this]

The keyword this names a pointer to the object for which a non-static member function ([class.mfct.non-static]) is invoked or a non-static data member's initializer ([class.mem]) is evaluated.
The current class at a program point is the class associated with the innermost class scope containing that point.
[Note 1:
A lambda-expression does not introduce a class scope.
— end note]
If a declaration declares a member function or member function template of a class X, the expression this is a prvalue of type “pointer to cv-qualifier-seq X” wherever X is the current class between the optional cv-qualifier-seq and the end of the function-definition, member-declarator, or declarator.
It shall not appear within the declaration of a static member function of the current class (although its type and value category are defined within a static member function as they are within a non-static member function).
[Note 2:
This is because declaration matching does not occur until the complete declarator is known.
— end note]
[Note 3:
In a trailing-return-type, the class being defined is not required to be complete for purposes of class member access.
Class members declared later are not visible.
[Example 1: struct A { char g(); template<class T> auto f(T t) -> decltype(t + g()) { return t + g(); } }; template auto A::f(int t) -> decltype(t + g()); — end example]
— end note]
Otherwise, if a member-declarator declares a non-static data member ([class.mem]) of a class X, the expression this is a prvalue of type “pointer to X” wherever X is the current class within the optional default member initializer ([class.mem]).
The expression this shall not appear in any other context.
[Example 2: class Outer { int a[sizeof(*this)]; // error: not inside a member function unsigned int sz = sizeof(*this); // OK: in default member initializer void f() { int b[sizeof(*this)]; // OK struct Inner { int c[sizeof(*this)]; // error: not inside a member function of Inner }; } }; — end example]