Why can't I capture this by-reference ('&this') in lambda?

Question

I understand the correct way to capture this (to modify object properties) in a lambda is as follows:

auto f = [this] () { /* ... */ };
<         


        

Answer 1

Because standard doesn't have &this in Captures lists:

N4713 8.4.5.2 Captures:

lambda-capture:
    capture-default
    capture-list
    capture-default, capture-list

capture-default:
    &
    =
capture-list:
    capture...opt
    capture-list, capture...opt
capture:
    simple-capture
    init-capture
simple-capture:
    identifier
    &identifier
    this
    * this
init-capture:
    identifier initializer
    &identifier initializer

7. For the purposes of lambda capture, an expression potentially references local entities as follows:

   7.3 A this expression potentially references *this.

So, standard guarantees this and *this is valid, and &this is invalid. Also, capturing this means capturing *this(which is a lvalue, the object itself) by reference, rather than capturing this pointer by value!