[class.copy.ctor] - C++23 → Trunk

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tmp/tmp5kis0cy3/{from.md → to.md} +12 -14

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@@ -123,11 +123,11 @@ form
 X::X(const X&)
 ```
 if each potentially constructed subobject of a class type `M` (or array
 thereof) has a copy constructor whose first parameter is of type `const`
-`M&` or `const` `volatile` `M&`.[^3]
 Otherwise, the implicitly-declared copy constructor will have the form
 ``` cpp
 X::X(X&)
@@ -155,29 +155,28 @@ X::X(X&&)
 An implicitly-declared copy/move constructor is an inline public member
 of its class. A defaulted copy/move constructor for a class `X` is
 defined as deleted [[dcl.fct.def.delete]] if `X` has:
-- a potentially constructed subobject of type `M` (or array thereof)
- that cannot be copied/moved because overload resolution
   [[over.match]], as applied to find `M`’s corresponding constructor,
- results in an ambiguity or a function that is deleted or inaccessible
- from the defaulted constructor,
-- a variant member whose corresponding constructor as selected by
- overload resolution is non-trivial,
-- any potentially constructed subobject of a type with a destructor that
-  is deleted or inaccessible from the defaulted constructor, or,
 - for the copy constructor, a non-static data member of rvalue reference
   type.
 [*Note 4*: A defaulted move constructor that is defined as deleted is
 ignored by overload resolution [[over.match]], [[over.over]]. Such a
 constructor would otherwise interfere with initialization from an rvalue
 which can use the copy constructor instead. — *end note*]
 A copy/move constructor for class `X` is trivial if it is not
-user-provided and if:
 - class `X` has no virtual functions [[class.virtual]] and no virtual
   base classes [[class.mi]], and
 - the constructor selected to copy/move each direct base class subobject
   is trivial, and
@@ -189,13 +188,12 @@ otherwise the copy/move constructor is *non-trivial*.
 [*Note 5*: The copy/move constructor is implicitly defined even if the
 implementation elided its odr-use
 [[term.odr.use]], [[class.temporary]]. — *end note*]
-If an implicitly-defined [[dcl.fct.def.default]] constructor would be
-constexpr-suitable [[dcl.constexpr]], the implicitly-defined constructor
-is `constexpr`.
 Before the defaulted copy/move constructor for a class is implicitly
 defined, all non-user-provided copy/move constructors for its
 potentially constructed subobjects are implicitly defined.
@@ -204,11 +202,11 @@ exception specification [[except.spec]]. — *end note*]
 The implicitly-defined copy/move constructor for a non-union class `X`
 performs a memberwise copy/move of its bases and members.
 [*Note 7*: Default member initializers of non-static data members are
-ignored. See also the example in  [[class.base.init]]. — *end note*]
 The order of initialization is the same as the order of initialization
 of bases and members in a user-defined constructor (see
 [[class.base.init]]). Let `x` be either the parameter of the constructor
 or, for the move constructor, an xvalue referring to the parameter. Each

 X::X(const X&)
 ```
 if each potentially constructed subobject of a class type `M` (or array
 thereof) has a copy constructor whose first parameter is of type `const`
+`M&` or `const` `volatile` `M&`.[^2]
 Otherwise, the implicitly-declared copy constructor will have the form
 ``` cpp
 X::X(X&)
 An implicitly-declared copy/move constructor is an inline public member
 of its class. A defaulted copy/move constructor for a class `X` is
 defined as deleted [[dcl.fct.def.delete]] if `X` has:
+- a potentially constructed subobject of type `M` (or possibly
+ multidimensional array thereof) for which overload resolution
   [[over.match]], as applied to find `M`’s corresponding constructor,
+ either does not result in a usable candidate [[over.match.general]]
+ or, in the case of a variant member, selects a non-trivial function,
+- any potentially constructed subobject of class type `M` (or possibly
+ multidimensional array thereof) where `M` has a destructor that is
+  deleted or inaccessible from the defaulted constructor, or,
 - for the copy constructor, a non-static data member of rvalue reference
   type.
 [*Note 4*: A defaulted move constructor that is defined as deleted is
 ignored by overload resolution [[over.match]], [[over.over]]. Such a
 constructor would otherwise interfere with initialization from an rvalue
 which can use the copy constructor instead. — *end note*]
 A copy/move constructor for class `X` is trivial if it is not
+user-provided and if
 - class `X` has no virtual functions [[class.virtual]] and no virtual
   base classes [[class.mi]], and
 - the constructor selected to copy/move each direct base class subobject
   is trivial, and
 [*Note 5*: The copy/move constructor is implicitly defined even if the
 implementation elided its odr-use
 [[term.odr.use]], [[class.temporary]]. — *end note*]
+The implicitly-defined [[dcl.fct.def.default]] constructor is
+`constexpr`.
 Before the defaulted copy/move constructor for a class is implicitly
 defined, all non-user-provided copy/move constructors for its
 potentially constructed subobjects are implicitly defined.
 The implicitly-defined copy/move constructor for a non-union class `X`
 performs a memberwise copy/move of its bases and members.
 [*Note 7*: Default member initializers of non-static data members are
+ignored. — *end note*]
 The order of initialization is the same as the order of initialization
 of bases and members in a user-defined constructor (see
 [[class.base.init]]). Let `x` be either the parameter of the constructor
 or, for the move constructor, an xvalue referring to the parameter. Each

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