Merge 2022-11 CWG Motion 10

P2706R0 Redundant specification for defaulted functions

Author: tkoeppe

source/classes.tex

@@ -1040,8 +1040,7 @@
 The implementation will implicitly declare these member functions for some class
 types when the program does not explicitly declare them.
 The implementation will implicitly define them
-if they are odr-used\iref{term.odr.use} or
-needed for constant evaluation\iref{expr.const}.
+as needed\iref{dcl.fct.def.default}.
 \end{note}
 An implicitly-declared special member function is declared at the closing
 \tcode{\}} of the \grammarterm{class-specifier}.
@@ -1303,15 +1302,7 @@
 \defnx{non-trivial}{constructor!default!non-trivial}.
 
 \pnum
-A default constructor
-that is defaulted and not defined as deleted
-is
-\defnx{implicitly defined}{constructor!implicitly defined}
-when it is odr-used\iref{term.odr.use}
-to initialize an object of its class type\iref{intro.object},
-when it is needed for constant evaluation\iref{expr.const}, or
-when it is explicitly defaulted after its first declaration.
-The implicitly-defined default constructor performs the set of
+An implicitly-defined\iref{dcl.fct.def.default} default constructor performs the set of
 initializations of the class that would be performed by a user-written default
 constructor for that class with no
 \grammarterm{ctor-initializer}\iref{class.base.init} and an empty
@@ -1602,20 +1593,11 @@
 \defnx{non-trivial}{constructor!copy!nontrivial}.
 
 \pnum
-\indextext{constructor!copy!implicitly defined}%
-\indextext{constructor!move!implicitly defined}%
-A copy/move constructor
-that is defaulted and not defined as deleted
-is
-\term{implicitly defined}
-when it is odr-used\iref{term.odr.use},
-when it is needed for constant evaluation\iref{expr.const}, or
-when it is explicitly defaulted after its first declaration.
 \begin{note}
 The copy/move constructor is implicitly defined even if the implementation elided
 its odr-use\iref{term.odr.use,class.temporary}.
 \end{note}
-If the implicitly-defined constructor would satisfy the requirements of a
+If an implicitly-defined\iref{dcl.fct.def.default} constructor would satisfy the requirements of a
 constexpr function\iref{dcl.constexpr}, the implicitly-defined
 constructor is \keyword{constexpr}.
 
@@ -1905,18 +1887,7 @@
 \defnx{non-trivial}{assignment operator!copy!non-trivial}.
 
 \pnum
-\indextext{assignment operator!copy!implicitly defined}%
-\indextext{assignment operator!move!implicitly defined}%
-A copy/move assignment operator for a class \tcode{X}
-that is defaulted and not defined as deleted
-is
-\term{implicitly defined}
-when it is odr-used\iref{term.odr.use}
-(e.g., when it is selected by overload resolution
-to assign to an object of its class type),
-when it is needed for constant evaluation\iref{expr.const}, or
-when it is explicitly defaulted after its first declaration.
-The implicitly-defined copy/move assignment operator is \keyword{constexpr}.
+An implicitly-defined\iref{dcl.fct.def.default} copy/move assignment operator is \keyword{constexpr}.
 
 \pnum
 Before the defaulted copy/move assignment operator for a class is
@@ -2126,14 +2097,6 @@
 A defaulted destructor is a constexpr destructor
 if it satisfies the requirements for a constexpr function\iref{dcl.constexpr}.
 
-\pnum
-A destructor
-that is defaulted and not defined as deleted
-is
-\defnx{implicitly defined}{destructor!implicitly defined}
-when it is odr-used\iref{term.odr.use}
-or when it is explicitly defaulted after its first declaration.
-
 \pnum
 Before a
 defaulted destructor for a class is implicitly defined, all the non-user-provided
@@ -6435,12 +6398,7 @@
 where the implicit object parameter (if any) is considered to be
 the first parameter.
 \end{itemize}
-A comparison operator function for class \tcode{C} that
-is defaulted on its first declaration and
-is not defined as deleted is
-\defnx{implicitly defined}{operator!comparison!implicitly defined}
-when it is odr-used or needed for constant evaluation.
-Name lookups in the defaulted definition
+Name lookups in the implicit definition\iref{dcl.fct.def.default}
 of a comparison operator function
 are performed from a context equivalent to
 its \grammarterm{function-body}.

source/declarations.tex

@@ -6275,7 +6275,7 @@
 Explicitly-defaulted functions and implicitly-declared functions are collectively
 called \defn{defaulted} functions, and the implementation
 shall provide implicit definitions
-for them\iref{class.ctor,class.dtor,class.copy.ctor,class.copy.assign},
+for them\iref{class.ctor,class.dtor,class.copy.ctor,class.copy.assign} as described below,
 including possibly defining them as deleted.
 A defaulted prospective destructor\iref{class.dtor}
 that is not a destructor is defined as deleted.
@@ -6287,8 +6287,12 @@
 \defn{user-provided} if it is user-declared and not explicitly
 defaulted or deleted on its first declaration. A user-provided explicitly-defaulted function
 (i.e., explicitly defaulted after its first declaration)
-is defined at the point where it is explicitly defaulted; if such a function is implicitly
+is implicitly defined at the point where it is explicitly defaulted; if such a function is implicitly
 defined as deleted, the program is ill-formed.
+A non-user-provided defaulted function
+(i.e. implicitly declared or explicitly defaulted in the class)
+that is not defined as deleted is implicitly defined when it is odr-used\iref{basic.def.odr}
+or needed for constant evaluation\iref{expr.const}.
 \begin{note}
 Declaring a function as defaulted after its first declaration can provide
 efficient execution and concise