Merge 2023-02 CWG Motion 10

P2797R0 Proposed resolution for CWG2692 Static and explicit object member functions with the same parameter-type-lists

Author: tkoeppe

source/classes.tex

@@ -944,9 +944,10 @@
 a member thereof, as described below.
 
 \pnum
-When an \grammarterm{id-expression}\iref{expr.prim.id} that is not part of a
-class member access syntax\iref{expr.ref} and not used to form a
-pointer to member\iref{expr.unary.op} is used
+When an \grammarterm{id-expression}\iref{expr.prim.id} that is
+neither part of a class member access syntax\iref{expr.ref}
+nor the unparenthesized operand of
+the unary \tcode{\&} operator\iref{expr.unary.op} is used
 where the current class is \tcode{X}\iref{expr.prim.this},
 if name
 lookup\iref{basic.lookup} resolves the name in the

source/expressions.tex

@@ -1341,7 +1341,7 @@
 
 \pnum
 An \grammarterm{id-expression} that denotes a non-static data member or
-non-static member function of a class can only be used:
+implicit object member function of a class can only be used:
 \begin{itemize}
 \item as part of a class member access\iref{expr.ref} in which the
 object expression
@@ -3171,21 +3171,6 @@
 conversion\iref{conv.func} is suppressed on the postfix expression),
 or have function pointer type.
 
-\pnum
-For a call to a non-static member function,
-the postfix expression shall be an
-implicit\iref{class.mfct.non.static,class.static} or explicit
-class member access\iref{expr.ref} whose \grammarterm{id-expression} is a
-function member name, or a pointer-to-member
-expression\iref{expr.mptr.oper} selecting a function member; the call is as a member of
-the class object referred to by the
-object expression. In the case of an implicit class
-member access, the implied object is the one pointed to by \keyword{this}.
-\begin{note}
-A member function call of the form \tcode{f()} is interpreted as
-\tcode{(*\keyword{this}).f()} (see~\ref{class.mfct.non.static}).
-\end{note}
-
 \pnum
 If the selected
 function is non-virtual, or if the \grammarterm{id-expression} in the class

source/overloading.tex

@@ -154,15 +154,17 @@
 \indextext{function!overload resolution and}%
 The set of candidate functions can contain both member and non-member
 functions to be resolved against the same argument list.
-So that argument and parameter lists are comparable within this
-heterogeneous set, a member function that does not have an explicit object parameter is considered to have an
-extra first parameter, called the
-\defn{implicit object parameter},
-which represents the object for which the member function has been
-called.
-For the purposes of overload resolution, both static and
-non-static member functions have an object parameter,
-but constructors do not.
+If a member function is
+\begin{itemize}
+\item
+an implicit object member function that is not a constructor, or
+\item
+a static member function and
+the argument list includes an implied object argument,
+\end{itemize}
+it is considered to have an extra first parameter,
+called the \defnadj{implicit}{object parameter},
+which represents the object for which the member function has been called.
 
 \pnum
 Similarly, when appropriate, the context can construct an
@@ -367,7 +369,11 @@
 \pnum
 If the \grammarterm{postfix-expression} is the address of an overload set,
 overload resolution is applied using that set as described above.
-If the function selected by overload resolution is a non-static member function,
+\begin{note}
+No implied object argument is added in this case.
+\end{note}
+If the function selected by overload resolution is
+an implicit object member function,
 the program is ill-formed.
 \begin{note}
 The resolution of the address of an
@@ -443,15 +449,16 @@
 The function declarations found by name lookup\iref{basic.lookup} constitute the
 set of candidate functions.
 Because of the rules for name lookup, the set of candidate functions
-consists (1) entirely of non-member functions or (2) entirely of
+consists either entirely of non-member functions or entirely of
 member functions of some class
 \tcode{T}.
-In case (1),
+In the former case or
+if the \grammarterm{primary-expression} is the address of an overload set,
 the argument list is
 the same as the
 \grammarterm{expression-list}
 in the call.
-In case (2), the argument list is the
+Otherwise, the argument list is the
 \grammarterm{expression-list}
 in the call augmented by the addition of an implied object
 argument as in a qualified function call.
@@ -485,6 +492,19 @@
     a();                // OK, \tcode{(*this).a()}
   }
 
+void c(this const C&);      // \#1
+void c()&;                  // \#2
+static void c(int = 0);     // \#3
+
+void d() {
+  c();                  // error: ambiguous between \#2 and \#3
+  (C::c)();             // error: as above
+  (&(C::c))();          // error: cannot resolve address of overloaded \tcode{this->C::c}\iref{over.over}
+  (&C::c)(C{});         // selects \#1
+  (&C::c)(*this);       // error: selects \#2, and is ill-formed\iref{over.match.call.general}
+  (&C::c)();            // selects \#3
+}
+
   void f(this const C&);
   void g() const {
     f();                // OK, \tcode{(*this).f()}