Suggested resolution:

Change in 7.7.2 [expr.const.core] bullet 2.1 as follows:

An expression E is a core constant expression unless the evaluation of E, following the rules of the abstract machine (6.10.1 [intro.execution]), would evaluate one of the following:

• this (7.5.3 [expr.prim.this]), except
  • in a constexpr function (9.2.6 [dcl.constexpr]) that is being evaluated as part of E, or
  • in a default member initializer for an object that is being initialized as part of E, or
  • when appearing as the postfix-expression of an implicit or explicit class member access expression (7.6.1.5 [expr.ref]);
• ...

(From submission #949.)

Consider:

  constexpr struct A {
    A* p = this;
  } a;

This use of this during constant evaluation is not, but ought to be, permitted by 7.7.2 [expr.const.core] paragraph 2.1.