From Jason Turner

[dcl.fct.def.default]

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  1. tmp/tmpr19r2x00/{from.md → to.md} +19 -12
tmp/tmpr19r2x00/{from.md → to.md} RENAMED
@@ -2,24 +2,24 @@
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  A function definition whose *function-body* is of the form `= default ;`
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  is called an *explicitly-defaulted* definition. A function that is
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  explicitly defaulted shall
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- - be a special member function or a comparison operator function
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- [[over.binary]], and
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- - not have default arguments.
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  An explicitly defaulted special member function `F₁` is allowed to
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  differ from the corresponding special member function `F₂` that would
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  have been implicitly declared, as follows:
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  - `F₁` and `F₂` may have differing *ref-qualifier*s;
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  - if `F₂` has an implicit object parameter of type “reference to `C`”,
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  `F₁` may be an explicit object member function whose explicit object
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- parameter is of type “reference to `C`”, in which case the type of
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- `F₁` would differ from the type of `F₂` in that the type of `F₁` has
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- an additional parameter;
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  - `F₁` and `F₂` may have differing exception specifications; and
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  - if `F₂` has a non-object parameter of type `const C&`, the
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  corresponding non-object parameter of `F₁` may be of type `C&`.
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  If the type of `F₁` differs from the type of `F₂` in a way other than as
@@ -34,10 +34,13 @@ allowed by the preceding rules, then:
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  A function explicitly defaulted on its first declaration is implicitly
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  inline [[dcl.inline]], and is implicitly constexpr [[dcl.constexpr]] if
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  it is constexpr-suitable.
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  [*Example 1*:
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  ``` cpp
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  struct S {
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  S(int a = 0) = default; // error: default argument
@@ -75,21 +78,25 @@ neither a prospective destructor nor an eligible special member function
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  [[special]] is defined as deleted. A function is *user-provided* if it
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  is user-declared and not explicitly defaulted or deleted on its first
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  declaration. A user-provided explicitly-defaulted function (i.e.,
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  explicitly defaulted after its first declaration) is implicitly defined
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  at the point where it is explicitly defaulted; if such a function is
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- implicitly defined as deleted, the program is ill-formed. A
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- non-user-provided defaulted function (i.e., implicitly declared or
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- explicitly defaulted in the class) that is not defined as deleted is
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- implicitly defined when it is odr-used [[basic.def.odr]] or needed for
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- constant evaluation [[expr.const]].
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- [*Note 1*: Declaring a function as defaulted after its first
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  declaration can provide efficient execution and concise definition while
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  enabling a stable binary interface to an evolving code
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  base. — *end note*]
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  [*Example 2*:
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  ``` cpp
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  struct trivial {
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  trivial() = default;
 
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  A function definition whose *function-body* is of the form `= default ;`
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  is called an *explicitly-defaulted* definition. A function that is
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  explicitly defaulted shall
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+ - be a special member function [[special]] or a comparison operator
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+ function [[over.binary]], [[class.compare.default]], and
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+ - not have default arguments [[dcl.fct.default]].
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  An explicitly defaulted special member function `F₁` is allowed to
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  differ from the corresponding special member function `F₂` that would
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  have been implicitly declared, as follows:
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  - `F₁` and `F₂` may have differing *ref-qualifier*s;
16
  - if `F₂` has an implicit object parameter of type “reference to `C`”,
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  `F₁` may be an explicit object member function whose explicit object
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+ parameter is of (possibly different) type “reference to `C`”, in which
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+ case the type of `F₁` would differ from the type of `F₂` in that the
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+ type of `F₁` has an additional parameter;
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  - `F₁` and `F₂` may have differing exception specifications; and
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  - if `F₂` has a non-object parameter of type `const C&`, the
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  corresponding non-object parameter of `F₁` may be of type `C&`.
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  If the type of `F₁` differs from the type of `F₂` in a way other than as
 
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  A function explicitly defaulted on its first declaration is implicitly
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  inline [[dcl.inline]], and is implicitly constexpr [[dcl.constexpr]] if
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  it is constexpr-suitable.
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+ [*Note 1*: Other defaulted functions are not implicitly
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+ constexpr. — *end note*]
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+
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  [*Example 1*:
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  ``` cpp
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  struct S {
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  S(int a = 0) = default; // error: default argument
 
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  [[special]] is defined as deleted. A function is *user-provided* if it
79
  is user-declared and not explicitly defaulted or deleted on its first
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  declaration. A user-provided explicitly-defaulted function (i.e.,
81
  explicitly defaulted after its first declaration) is implicitly defined
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  at the point where it is explicitly defaulted; if such a function is
83
+ implicitly defined as deleted, the program is ill-formed.
 
 
 
 
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+ [*Note 2*: Declaring a function as defaulted after its first
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  declaration can provide efficient execution and concise definition while
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  enabling a stable binary interface to an evolving code
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  base. — *end note*]
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+ A non-user-provided defaulted function (i.e., implicitly declared or
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+ explicitly defaulted in the class) that is not defined as deleted is
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+ implicitly defined when it is odr-used [[basic.def.odr]] or needed for
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+ constant evaluation [[expr.const]].
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+
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+ [*Note 3*: The implicit definition of a non-user-provided defaulted
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+ function does not bind any names. — *end note*]
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+
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  [*Example 2*:
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  ``` cpp
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  struct trivial {
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  trivial() = default;