depish/cppdraft_translate
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Init

Browse Source
This commit is contained in:
Leonov Artur (Depish)
2025-10-25 03:02:53 +03:00
commit 043225d523
3416 changed files with 681196 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
cppdraft/over/ics/ellipsis.md Normal file
View File

@@ -0,0 +1,19 @@
[over.ics.ellipsis]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.ellipsis)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.ellipsis)
#### 12.2.4.2 Implicit conversion sequences [[over.best.ics]](over.best.ics#over.ics.ellipsis)
#### 12.2.4.2.4 Ellipsis conversion sequences [over.ics.ellipsis]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2380)
An ellipsis conversion sequence occurs when an argument in a
function call is matched with the ellipsis parameter
specification of the function called (see [[expr.call]](expr.call "7.6.1.3 Function call"))[.](#1.sentence-1)

195
cppdraft/over/ics/list.md Normal file
View File

@@ -0,0 +1,195 @@
[over.ics.list]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.list)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.list)
#### 12.2.4.2 Implicit conversion sequences [[over.best.ics]](over.best.ics#over.ics.list)
#### 12.2.4.2.6 List-initialization sequence [over.ics.list]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2484)
When an argument is an initializer list ([[dcl.init.list]](dcl.init.list "9.5.5 List-initialization")), it is not an expression and special rules apply for converting it to a parameter type[.](#1.sentence-1)
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2488)
If the initializer list is a [*designated-initializer-list*](dcl.init.general#nt:designated-initializer-list "9.5.1 General [dcl.init.general]") and the parameter is not a reference,
a conversion is only possible if
the parameter has an aggregate type
that can be initialized from the initializer list
according to the rules for aggregate initialization ([[dcl.init.aggr]](dcl.init.aggr "9.5.2 Aggregates")),
in which case the implicit conversion sequence is
a user-defined conversion sequence
whose second standard conversion sequence
is an identity conversion[.](#2.sentence-1)
[*Note [1](#note-1)*:
Aggregate initialization does not require that
the members are declared in designation order[.](#2.sentence-2)
If, after overload resolution, the order does not match
for the selected overload,
the initialization of the parameter will be ill-formed ([[dcl.init.list]](dcl.init.list "9.5.5 List-initialization"))[.](#2.sentence-3)
[*Example [1](#example-1)*: struct A { int x, y; };struct B { int y, x; };void f(A a, int); // #1void f(B b, ...); // #2void g(A a); // #3void g(B b); // #4void h() { f({.x = 1, .y = 2}, 0); // OK; calls #1 f({.y = 2, .x = 1}, 0); // error: selects #1, initialization of a fails// due to non-matching member order ([[dcl.init.list]](dcl.init.list "9.5.5 List-initialization")) g({.x = 1, .y = 2}); // error: ambiguous between #3 and #4} — *end example*]
— *end note*]
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2523)
Otherwise,
if the parameter type is an aggregate class X and the initializer list has a
single element of type cv U, where U is X or a class derived from X, the implicit conversion sequence is the one
required to convert the element to the parameter type[.](#3.sentence-1)
[4](#4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2530)
Otherwise, if the parameter type is a character array[106](#footnote-106 "Since there are no parameters of array type, this will only occur as the referenced type of a reference parameter.") and the initializer list has a single element that is an appropriately-typed[*string-literal*](lex.string#nt:string-literal "5.13.5 String literals [lex.string]") ([[dcl.init.string]](dcl.init.string "9.5.3 Character arrays")), the implicit conversion
sequence is the identity conversion[.](#4.sentence-1)
[5](#5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2540)
Otherwise, if the parameter type is std​::​initializer_list<X> and all the elements
of the initializer list can be implicitly converted to X, the implicit
conversion sequence is the worst conversion necessary to convert an element of
the list to X, or if the initializer list has no elements, the identity
conversion[.](#5.sentence-1)
This conversion can be a user-defined conversion even in
the context of a call to an initializer-list constructor[.](#5.sentence-2)
[*Example [2](#example-2)*: void f(std::initializer_list<int>);
f( {} ); // OK, f(initializer_list<int>) identity conversion f( {1,2,3} ); // OK, f(initializer_list<int>) identity conversion f( {'a','b'} ); // OK, f(initializer_list<int>) integral promotion f( {1.0} ); // error: narrowingstruct A { A(std::initializer_list<double>); // #1 A(std::initializer_list<std::complex<double>>); // #2 A(std::initializer_list<std::string>); // #3};
A a{ 1.0,2.0 }; // OK, uses #1void g(A);
g({ "foo", "bar" }); // OK, uses #3typedef int IA[3];void h(const IA&);
h({ 1, 2, 3 }); // OK, identity conversion — *end example*]
[6](#6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2572)
Otherwise, if the parameter type is “array of N X”
or “array of unknown bound of X”,
if there exists an implicit conversion sequence
from each element of the initializer list
(and from {} in the former case
if N exceeds the number of elements in the initializer list)
to X, the implicit conversion sequence is
the worst such implicit conversion sequence[.](#6.sentence-1)
[7](#7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2582)
Otherwise, if the parameter is a non-aggregate class X and overload
resolution per [[over.match.list]](over.match.list "12.2.2.8 Initialization by list-initialization") chooses a single best constructor C ofX to perform the initialization of an object of type X from the
argument initializer list:
- [(7.1)](#7.1)
If C is not an initializer-list constructor
and the initializer list has a single element of type cv U,
where U is X or a class derived from X,
the implicit conversion sequence has Exact Match rank if U is X,
or Conversion rank if U is derived from X[.](#7.1.sentence-1)
- [(7.2)](#7.2)
Otherwise, the implicit conversion sequence is a user-defined
conversion sequence whose second standard conversion sequence is an
identity conversion[.](#7.2.sentence-1)
If multiple constructors are viable but none is better than
the others, the implicit conversion sequence is the ambiguous conversion
sequence[.](#7.sentence-2)
User-defined conversions are allowed for conversion of the initializer
list elements to the constructor parameter types except as noted
in [[over.best.ics]](over.best.ics "12.2.4.2 Implicit conversion sequences")[.](#7.sentence-3)
[*Example [3](#example-3)*: struct A { A(std::initializer_list<int>);};void f(A);
f( {'a', 'b'} ); // OK, f(A(std​::​initializer_list<int>)) user-defined conversionstruct B { B(int, double);};void g(B);
g( {'a', 'b'} ); // OK, g(B(int, double)) user-defined conversion g( {1.0, 1.0} ); // error: narrowingvoid f(B);
f( {'a', 'b'} ); // error: ambiguous f(A) or f(B)struct C { C(std::string);};void h(C);
h({"foo"}); // OK, h(C(std​::​string("foo")))struct D { D(A, C);};void i(D);
i({ {1,2}, {"bar"} }); // OK, i(D(A(std​::​initializer_list<int>{1,2}), C(std​::​string("bar")))) — *end example*]
[8](#8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2636)
Otherwise, if the parameter has an aggregate type which can be initialized from
the initializer list according to the rules for aggregate
initialization ([[dcl.init.aggr]](dcl.init.aggr "9.5.2 Aggregates")), the implicit conversion sequence is a
user-defined conversion sequence whose second standard conversion
sequence is an identity conversion[.](#8.sentence-1)
[*Example [4](#example-4)*: struct A {int m1; double m2;};
void f(A);
f( {'a', 'b'} ); // OK, f(A(int,double)) user-defined conversion f( {1.0} ); // error: narrowing — *end example*]
[9](#9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2655)
Otherwise, if the parameter is a reference, see [[over.ics.ref]](over.ics.ref "12.2.4.2.5 Reference binding")[.](#9.sentence-1)
[*Note [2](#note-2)*:
The rules in this subclause will apply for initializing the underlying temporary
for the reference[.](#9.sentence-2)
— *end note*]
[*Example [5](#example-5)*: struct A {int m1; double m2;};
void f(const A&);
f( {'a', 'b'} ); // OK, f(A(int,double)) user-defined conversion f( {1.0} ); // error: narrowingvoid g(const double &);
g({1}); // same conversion as int to double — *end example*]
[10](#10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2677)
Otherwise, if the parameter type is not a class:
- [(10.1)](#10.1)
if the initializer list has one element that is not itself an initializer list,
the implicit conversion sequence is the one required to convert the element to
the parameter type;
[*Example [6](#example-6)*: void f(int);
f( {'a'} ); // OK, same conversion as char to int f( {1.0} ); // error: narrowing — *end example*]
- [(10.2)](#10.2)
if the initializer list has no elements, the implicit conversion sequence
is the identity conversion[.](#10.sentence-1)
[*Example [7](#example-7)*: void f(int);
f( { } ); // OK, identity conversion — *end example*]
[11](#11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2701)
In all cases other than those enumerated above, no conversion is possible[.](#11.sentence-1)
[106)](#footnote-106)[106)](#footnoteref-106)
Since there are no parameters of array type,
this will only occur as the referenced type of a reference parameter[.](#footnote-106.sentence-1)

245
cppdraft/over/ics/rank.md Normal file
View File

@@ -0,0 +1,245 @@
[over.ics.rank]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.rank)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.rank)
#### 12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2706)
This subclause defines a partial ordering of implicit conversion
sequences based on the relationships[*better conversion sequence*](#def:conversion_sequence,better "12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]") and[*better conversion*](#def:conversion,better "12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]")[.](#1.sentence-1)
If an implicit conversion sequence S1 is
defined by these rules to be a better conversion sequence than
S2, then it is also the case that S2 is a[*worse conversion sequence*](#def:conversion_sequence,worse "12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]") than S1[.](#1.sentence-2)
If conversion sequence S1 is neither better
than nor worse than conversion sequence S2, S1 and S2 are said to
be[*indistinguishable conversion sequences*](#def:conversion_sequence,indistinguishable "12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]")[.](#1.sentence-3)
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2722)
When comparing the basic forms of implicit conversion sequences
(as defined in [[over.best.ics]](over.best.ics "12.2.4.2 Implicit conversion sequences"))
- [(2.1)](#2.1)
a [standard conversion sequence](over.ics.scs "12.2.4.2.2 Standard conversion sequences [over.ics.scs]") is a better
conversion sequence than a user-defined conversion sequence
or an ellipsis conversion sequence, and
- [(2.2)](#2.2)
a [user-defined conversion sequence](over.ics.user "12.2.4.2.3 User-defined conversion sequences [over.ics.user]") is a
better conversion sequence than an [ellipsis conversion
sequence](over.ics.ellipsis "12.2.4.2.4 Ellipsis conversion sequences [over.ics.ellipsis]")[.](#2.sentence-1)
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2736)
Two implicit conversion sequences of the same form are
indistinguishable conversion sequences unless one of the
following rules applies:
- [(3.1)](#3.1)
List-initialization sequence L1 is a better conversion sequence than
list-initialization sequence L2 if
* [(3.1.1)](#3.1.1)
L1 converts to std​::​initializer_list<X> for some X andL2 does not, or, if not that,
* [(3.1.2)](#3.1.2)
L1 and L2 convert to arrays of the same element type, and
either the number of elements n1 initialized by L1 is less than the number of elements n2 initialized by L2, orn1=n2 andL2 converts to an array of unknown bound and L1 does not,
even if one of the other rules in this paragraph would otherwise apply[.](#3.1.sentence-1)
[*Example [1](#example-1)*: void f1(int); // #1void f1(std::initializer_list<long>); // #2void g1() { f1({42}); } // chooses #2void f2(std::pair<const char*, const char*>); // #3void f2(std::initializer_list<std::string>); // #4void g2() { f2({"foo","bar"}); } // chooses #4 — *end example*]
[*Example [2](#example-2)*: void f(int (&&)[] ); // #1void f(double (&&)[] ); // #2void f(int (&&)[2]); // #3 f( {1} ); // Calls #1: Better than #2 due to conversion, better than #3 due to bounds f( {1.0} ); // Calls #2: Identity conversion is better than floating-integral conversion f( {1.0, 2.0} ); // Calls #2: Identity conversion is better than floating-integral conversion f( {1, 2} ); // Calls #3: Converting to array of known bound is better than to unknown bound,// and an identity conversion is better than floating-integral conversion — *end example*]
- [(3.2)](#3.2)
Standard conversion sequenceS1 is a better conversion
sequence than standard conversion sequenceS2 if
* [(3.2.1)](#3.2.1)
S1 is a proper subsequence ofS2 (comparing the conversion sequences in the canonical form defined
by [[over.ics.scs]](over.ics.scs "12.2.4.2.2 Standard conversion sequences"), excluding any Lvalue Transformation;
the identity conversion sequence is considered to be a
subsequence of any non-identity conversion sequence)
or, if not that,
* [(3.2.2)](#3.2.2)
the rank ofS1 is better than the rank ofS2,
orS1 andS2 have the same rank and are distinguishable by the rules
in the paragraph below,
or, if not that,
* [(3.2.3)](#3.2.3)
S1 and S2 include reference bindings ([[dcl.init.ref]](dcl.init.ref "9.5.4 References")) and
neither refers to an implicit object parameter of a non-static member function
declared without a [*ref-qualifier*](dcl.decl.general#nt:ref-qualifier "9.3.1 General [dcl.decl.general]"),
and S1 binds an rvalue reference to an
rvalue and S2 binds an lvalue reference
[*Example [3](#example-3)*: int i;int f1();int&& f2();int g(const int&);int g(const int&&);int j = g(i); // calls g(const int&)int k = g(f1()); // calls g(const int&&)int l = g(f2()); // calls g(const int&&)struct A { A& operator<<(int); void p() &; void p() &&;};
A& operator<<(A&&, char);
A() << 1; // calls A​::​operator<<(int) A() << 'c'; // calls operator<<(A&&, char) A a;
a << 1; // calls A​::​operator<<(int) a << 'c'; // calls A​::​operator<<(int) A().p(); // calls A​::​p()&& a.p(); // calls A​::​p()& — *end example*]
or, if not that,
* [(3.2.4)](#3.2.4)
S1 and S2 include reference bindings ([[dcl.init.ref]](dcl.init.ref "9.5.4 References")) andS1 binds an lvalue reference to an lvalue of function type andS2 binds an rvalue reference to an lvalue of function type
[*Example [4](#example-4)*: int f(void(&)()); // #1int f(void(&&)()); // #2void g();int i1 = f(g); // calls #1 — *end example*]
or, if not that,
* [(3.2.5)](#3.2.5)
S1 and S2 differ only
in their qualification conversion ([[conv.qual]](conv.qual "7.3.6 Qualification conversions")) and
yield similar types T1 and T2, respectively
(where a standard conversion sequence that is a reference binding
is considered to yield the cv-unqualified referenced type),
where T1 and T2 are not the same type, andconst T2 is reference-compatible with T1 ([[dcl.init.ref]](dcl.init.ref "9.5.4 References"))
[*Example [5](#example-5)*: int f(const volatile int *);int f(const int *);int i;int j = f(&i); // calls f(const int*)int g(const int*);int g(const volatile int* const&);int* p;int k = g(p); // calls g(const int*) — *end example*]
or, if not that,
* [(3.2.6)](#3.2.6)
S1 andS2 bind “reference to T1” and “reference to T2”,
respectively ([[dcl.init.ref]](dcl.init.ref "9.5.4 References")),
where T1 and T2 are not the same type, andT2 is reference-compatible with T1
[*Example [6](#example-6)*: int f(const int &);int f(int &);int g(const int &);int g(int);
int i;int j = f(i); // calls f(int &)int k = g(i); // ambiguousstruct X {void f() const; void f();};void g(const X& a, X b) { a.f(); // calls X​::​f() const b.f(); // calls X​::​f()}int h(int (&)[]);int h(int (&)[1]);void g2() {int a[1];
h(a); // calls h(int (&)[1])} — *end example*]
or, if not that,
* [(3.2.7)](#3.2.7)
S1 and S2 bind the same reference type “reference to T” and
have source types V1 and V2, respectively,
where the standard conversion sequence from V1* to T* is better than the standard conversion sequence from V2* to T*[.](#3.2.sentence-1)
[*Example [7](#example-7)*: struct Z {};
struct A {operator Z&(); operator const Z&(); // #1};
struct B {operator Z(); operator const Z&&(); // #2};
const Z& r1 = A(); // OK, uses #1const Z&& r2 = B(); // OK, uses #2 — *end example*]
- [(3.3)](#3.3)
User-defined conversion sequenceU1 is a better conversion sequence than another user-defined conversion
sequenceU2 if they contain the same user-defined conversion function or
constructor or they initialize the same class in an aggregate
initialization and in either case the second standard conversion
sequence ofU1 is better than
the second standard conversion sequence ofU2[.](#3.3.sentence-1)
[*Example [8](#example-8)*: struct A {operator short();} a;int f(int);int f(float);int i = f(a); // calls f(int), because short → int is// better than short → float. — *end example*]
[4](#4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2973)
Standard conversion sequences are ordered by their ranks: an Exact Match is a
better conversion than a Promotion, which is a better conversion than
a Conversion[.](#4.sentence-1)
Two conversion sequences with the same rank are indistinguishable unless
one of the following rules applies:
- [(4.1)](#4.1)
A conversion that does not convert a pointer or a pointer to member
tobool is better than one that does[.](#4.1.sentence-1)
- [(4.2)](#4.2)
A conversion that promotes an enumeration whose underlying type is fixed to its underlying
type is better than one that promotes to the promoted underlying type, if the two are
different[.](#4.2.sentence-1)
- [(4.3)](#4.3)
A conversion in either direction
between floating-point type FP1 and floating-point type FP2 is better than a conversion in the same direction
between FP1 and arithmetic type T3 if
* [(4.3.1)](#4.3.1)
the floating-point conversion rank ([[conv.rank]](conv.rank "6.9.6 Conversion ranks")) of FP1 is equal to the rank of FP2, and
* [(4.3.2)](#4.3.2)
T3 is not a floating-point type, orT3 is a floating-point type
whose rank is not equal to the rank of FP1, or
the floating-point conversion subrank ([[conv.rank]](conv.rank "6.9.6 Conversion ranks")) of FP2 is greater than the subrank of T3[.](#4.3.sentence-1)
[*Example [9](#example-9)*: int f(std::float32_t);int f(std::float64_t);int f(long long);float x;
std::float16_t y;int i = f(x); // calls f(std​::​float32_t) on implementations where// float and std​::​float32_t have equal conversion ranksint j = f(y); // error: ambiguous, no equal conversion rank — *end example*]
- [(4.4)](#4.4)
If classB is derived directly or indirectly from classA,
conversion ofB* toA* is better than conversion ofB* tovoid*,
and conversion ofA* tovoid* is better than conversion
ofB* tovoid*[.](#4.4.sentence-1)
- [(4.5)](#4.5)
If classB is derived directly or indirectly from classA and classC is derived directly or indirectly fromB,
* [(4.5.1)](#4.5.1)
conversion ofC* toB* is better than conversion ofC* toA*,
[*Example [10](#example-10)*: struct A {};struct B : public A {};struct C : public B {};
C* pc;int f(A*);int f(B*);int i = f(pc); // calls f(B*) — *end example*]
* [(4.5.2)](#4.5.2)
binding of an expression of typeC to a reference to typeB is better than binding an expression of typeC to a reference to typeA,
* [(4.5.3)](#4.5.3)
conversion ofA​::​* toB​::​* is better than conversion ofA​::​* toC​::​*,
* [(4.5.4)](#4.5.4)
conversion ofC toB is better than conversion ofC toA,
* [(4.5.5)](#4.5.5)
conversion ofB* toA* is better than conversion ofC* toA*,
* [(4.5.6)](#4.5.6)
binding of an expression of typeB to a reference to typeA is better than binding an expression of typeC to a
reference to typeA,
* [(4.5.7)](#4.5.7)
conversion ofB​::​* toC​::​* is better than conversion
ofA​::​* toC​::​*,
and
* [(4.5.8)](#4.5.8)
conversion ofB toA is better than conversion ofC toA[.](#4.5.sentence-1)
[*Note [1](#note-1)*:
Compared conversion sequences will have different source types only in the
context of comparing the second standard conversion sequence of an
initialization by user-defined conversion (see [[over.match.best]](over.match.best "12.2.4 Best viable function")); in
all other contexts, the source types will be the same and the target
types will be different[.](#4.5.sentence-2)
— *end note*]

112
cppdraft/over/ics/ref.md Normal file
View File

@@ -0,0 +1,112 @@
[over.ics.ref]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.ref)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.ref)
#### 12.2.4.2 Implicit conversion sequences [[over.best.ics]](over.best.ics#over.ics.ref)
#### 12.2.4.2.5 Reference binding [over.ics.ref]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2388)
When a parameter of type “reference to cv T”
binds directly ([[dcl.init.ref]](dcl.init.ref "9.5.4 References")) to an argument expression:
- [(1.1)](#1.1)
If the argument expression has a type that
is a derived class of the parameter type,
the implicit conversion sequence is a derived-to-base
conversion ([[over.best.ics]](over.best.ics "12.2.4.2 Implicit conversion sequences"))[.](#1.1.sentence-1)
- [(1.2)](#1.2)
Otherwise,
if the type of the argument is possibly cv-qualified T, or
if T is an array type of unknown bound with element type U and
the argument has an array type of known bound whose
element type is possibly cv-qualified U,
the implicit conversion sequence is the identity conversion[.](#1.2.sentence-1)
- [(1.3)](#1.3)
Otherwise,
if T is a function type,
the implicit conversion sequence is a function pointer conversion[.](#1.3.sentence-1)
- [(1.4)](#1.4)
Otherwise, the implicit conversion sequence is a qualification conversion[.](#1.4.sentence-1)
[*Example [1](#example-1)*: struct A {};struct B : public A {} b;int f(A&);int f(B&);int i = f(b); // calls f(B&), an exact match, rather than f(A&), a conversionvoid g() noexcept;int h(void (&)() noexcept); // #1int h(void (&)()); // #2int j = h(g); // calls #1, an exact match, rather than #2, a function pointer conversion — *end example*]
If the parameter binds directly to the result of
applying a conversion function to the argument expression, the implicit
conversion sequence is a user-defined conversion sequence ([[over.ics.user]](over.ics.user "12.2.4.2.3 User-defined conversion sequences"))
whose second standard conversion sequence is
determined by the above rules[.](#1.sentence-2)
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2435)
When a parameter of reference type is not bound directly to an argument
expression, the conversion sequence is the one required to convert the argument
expression to the referenced type according to [[over.best.ics]](over.best.ics "12.2.4.2 Implicit conversion sequences")[.](#2.sentence-1)
Conceptually, this conversion sequence corresponds to copy-initializing a
temporary of the referenced type with the argument expression[.](#2.sentence-2)
Any difference
in top-level cv-qualification is subsumed by the initialization itself and
does not constitute a conversion[.](#2.sentence-3)
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2445)
Except for an implicit object parameter, for which see [[over.match.funcs]](over.match.funcs "12.2.2 Candidate functions and argument lists"),
an implicit conversion sequence cannot be formed if it requires
binding an lvalue reference
other than a reference to a non-volatile const type
to an rvalue
or binding an rvalue reference to an lvalue of object type[.](#3.sentence-1)
[*Note [1](#note-1)*:
This means, for example, that a candidate function cannot be a viable
function if it has a non-const lvalue reference parameter (other than
the implicit object parameter) and the corresponding argument
would require a temporary to be created to initialize the lvalue
reference (see [[dcl.init.ref]](dcl.init.ref "9.5.4 References"))[.](#3.sentence-2)
— *end note*]
[4](#4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2460)
Other restrictions on binding a reference to a particular argument
that are not based on the types of the reference and the argument
do not affect the formation of an implicit conversion
sequence, however[.](#4.sentence-1)
[*Example [2](#example-2)*:
A function with an “lvalue reference to int” parameter can
be a viable candidate even if the corresponding argument is anint bit-field[.](#4.sentence-2)
The formation of implicit conversion sequences
treats theint bit-field as anint lvalue and finds an exact
match with the parameter[.](#4.sentence-3)
If the function is selected by overload
resolution, the call will nonetheless be ill-formed because of
the prohibition on binding a non-const lvalue reference to a bit-field ([[dcl.init.ref]](dcl.init.ref "9.5.4 References"))[.](#4.sentence-4)
— *end example*]

86
cppdraft/over/ics/scs.md Normal file
View File

@@ -0,0 +1,86 @@
[over.ics.scs]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.scs)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.scs)
#### 12.2.4.2 Implicit conversion sequences [[over.best.ics]](over.best.ics#over.ics.scs)
#### 12.2.4.2.2 Standard conversion sequences [over.ics.scs]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2272)
Table [19](#tab:over.ics.scs "Table 19: Conversions") summarizes the conversions defined in [[conv]](conv "7.3 Standard conversions") and
partitions them into four disjoint categories: Lvalue Transformation,
Qualification Adjustment, Promotion, and Conversion[.](#1.sentence-1)
[*Note [1](#note-1)*:
These categories are orthogonal with respect to value category,
cv-qualification, and data representation: the Lvalue Transformations
do not change the cv-qualification or data
representation of the type; the Qualification Adjustments do not
change the value category or data representation of the type; and
the Promotions and Conversions do not change the
value category or cv-qualification of the type[.](#1.sentence-2)
— *end note*]
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2287)
[*Note [2](#note-2)*:
As described in [[conv]](conv "7.3 Standard conversions"),
a standard conversion sequence either is the Identity conversion
by itself (that is, no conversion) or consists of one to three
conversions from the other
four categories[.](#2.sentence-1)
If there are two or more conversions in the sequence, the
conversions are applied in the canonical order:**Lvalue Transformation**,**Promotion** or**Conversion**,**Qualification Adjustment**[.](#2.sentence-2)
— *end note*]
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2303)
Each conversion in Table [19](#tab:over.ics.scs "Table 19: Conversions") also has an associated rank (Exact
Match, Promotion, or Conversion)[.](#3.sentence-1)
These are used
to [rank standard conversion sequences](over.ics.rank "12.2.4.3 Ranking implicit conversion sequences [over.ics.rank]")[.](#3.sentence-2)
The rank of a conversion sequence is determined by considering the
rank of each conversion in the sequence and the rank of any [reference
binding](over.ics.ref "12.2.4.2.5 Reference binding [over.ics.ref]")[.](#3.sentence-3)
If any of those has Conversion rank, the
sequence has Conversion rank; otherwise, if any of those has Promotion rank,
the sequence has Promotion rank; otherwise, the sequence has Exact
Match rank[.](#3.sentence-4)
Table [19](#tab:over.ics.scs) — Conversions [[tab:over.ics.scs]](./tab:over.ics.scs)
| [🔗](#tab:over.ics.scs-row-1)<br>**Conversion** | **Category** | **Rank** | **Subclause** |
| --- | --- | --- | --- |
| [🔗](#tab:over.ics.scs-row-2)<br>No conversions required | Identity | | |
| [🔗](#tab:over.ics.scs-row-3)<br> Lvalue-to-rvalue conversion | | | [[conv.lval]](conv.lval "7.3.2 Lvalue-to-rvalue conversion") |
| [🔗](#tab:over.ics.scs-row-4)<br> Array-to-pointer conversion | Lvalue Transformation | | [[conv.array]](conv.array "7.3.3 Array-to-pointer conversion") |
| [🔗](#tab:over.ics.scs-row-5)<br> Function-to-pointer conversion | | Exact Match | [[conv.func]](conv.func "7.3.4 Function-to-pointer conversion") |
| [🔗](#tab:over.ics.scs-row-6)<br> Qualification conversions | | | [[conv.qual]](conv.qual "7.3.6 Qualification conversions") |
| [🔗](#tab:over.ics.scs-row-7)<br> Function pointer conversion | Qualification Adjustment | | [[conv.fctptr]](conv.fctptr "7.3.14 Function pointer conversions") |
| [🔗](#tab:over.ics.scs-row-8)<br>Integral promotions | | | [[conv.prom]](conv.prom "7.3.7 Integral promotions") |
| [🔗](#tab:over.ics.scs-row-9)<br> Floating-point promotion | Promotion | Promotion | [[conv.fpprom]](conv.fpprom "7.3.8 Floating-point promotion") |
| [🔗](#tab:over.ics.scs-row-10)<br>Integral conversions | | | [[conv.integral]](conv.integral "7.3.9 Integral conversions") |
| [🔗](#tab:over.ics.scs-row-11)<br> Floating-point conversions | | | [[conv.double]](conv.double "7.3.10 Floating-point conversions") |
| [🔗](#tab:over.ics.scs-row-12)<br> Floating-integral conversions | | | [[conv.fpint]](conv.fpint "7.3.11 Floating-integral conversions") |
| [🔗](#tab:over.ics.scs-row-13)<br> Pointer conversions | Conversion | Conversion | [[conv.ptr]](conv.ptr "7.3.12 Pointer conversions") |
| [🔗](#tab:over.ics.scs-row-14)<br> Pointer-to-member conversions | | | [[conv.mem]](conv.mem "7.3.13 Pointer-to-member conversions") |
| [🔗](#tab:over.ics.scs-row-15)<br> Boolean conversions | | | [[conv.bool]](conv.bool "7.3.15 Boolean conversions") |

65
cppdraft/over/ics/user.md Normal file
View File

@@ -0,0 +1,65 @@
[over.ics.user]
# 12 Overloading [[over]](./#over)
## 12.2 Overload resolution [[over.match]](over.match#over.ics.user)
### 12.2.4 Best viable function [[over.match.best]](over.match.best#over.ics.user)
#### 12.2.4.2 Implicit conversion sequences [[over.best.ics]](over.best.ics#over.ics.user)
#### 12.2.4.2.3 User-defined conversion sequences [over.ics.user]
[1](#1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2339)
A [*user-defined conversion sequence*](#def:conversion_sequence,user-defined "12.2.4.2.3 User-defined conversion sequences [over.ics.user]") consists of an initial
standard conversion sequence followed by a user-defined
conversion ([[class.conv]](class.conv "11.4.8 Conversions")) followed by a second standard
conversion sequence[.](#1.sentence-1)
If the user-defined conversion is specified
by a constructor ([[class.conv.ctor]](class.conv.ctor "11.4.8.2 Conversion by constructor")), the initial standard
conversion sequence converts the source type to the type of the
first parameter of that constructor[.](#1.sentence-2)
If the user-defined
conversion is specified by a [conversion function](class.conv.fct "11.4.8.3 Conversion functions [class.conv.fct]"), the
initial standard conversion sequence
converts the source type to the type of the
object parameter of that conversion function[.](#1.sentence-3)
[2](#2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2354)
The second standard conversion sequence converts the result of
the user-defined conversion to the target type for the sequence;
any reference binding is included in the second standard
conversion sequence[.](#2.sentence-1)
Since an implicit conversion sequence is an initialization, the
special rules for initialization by user-defined conversion apply
when selecting the best user-defined conversion for a
user-defined conversion sequence (see [[over.match.best]](over.match.best "12.2.4 Best viable function") and [[over.best.ics]](over.best.ics "12.2.4.2 Implicit conversion sequences"))[.](#2.sentence-2)
[3](#3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2364)
If the user-defined conversion is specified by a
specialization of a conversion function template,
the second standard conversion sequence shall have Exact Match rank[.](#3.sentence-1)
[4](#4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L2369)
A conversion of an expression of class type
to the same class type is given Exact Match rank, and
a conversion of an expression of class type
to a base class of that type is given Conversion rank,
in spite of the
fact that a constructor (i.e., a user-defined conversion
function) is called for those cases[.](#4.sentence-1)