// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf
#define msg "p231.cpp(107) 8.6.4 List-initialization [dcl.init.list]"

#include <iostream>
#include <algorithm>
#include <map>
#define complex _Complex double

int a = {1};
std::complex<double> z{1,2};
new std::vector<std::string> {"once", "upon", "a", "time"}; // 4 string elements
f( {"Nicholas","Annemarie"} ); // pass list of two elements
return { "Norah" }; // return list of one element
int* e {}; // initialization to zero / null pointer
x = double{1}; // explicitly construct a double
std::map<std::string,int> anim = { {"bear",4}, {"cassowary",2}, {"tiger",7} };

double ad[] = { 1, 2.0 }; // OK
int ai[] = { 1, 2.0 }; // error: narrowing
struct S2 {
  int m1;
  double m2, m3;
};
S2 s21 = { 1, 2, 3.0 }; // OK
S2 s22 { 1.0, 2, 3 }; // error: narrowing
S2 s23 { }; // OK: default to 0,0,0

struct S {
  S(std::initializer_list<double>); // #1
  S(std::initializer_list<int>); // #2
  S(); // #3
// ...
};
S s1 = { 1.0, 2.0, 3.0 }; // invoke #1
S s2 = { 1, 2, 3 }; // invoke #2
S s3 = { }; // invoke #3

struct Map {
  Map(std::initializer_list<std::pair<std::string,int>>);
};
Map ship = {{"Sophie",14}, {"Surprise",28}};

struct S2 {
// no initializer-list constructors
  S2(int, double, double); // #1
  S2(); // #2
// ...

};
S2 s1b = { 1, 2, 3.0 }; // OK: invoke #1
S2 s2b { 1.0, 2, 3 }; // error: narrowing
S2 s3b { }; // OK: invoke #2

int x1 {2}; // OK
int x2 {2.0}; // error: narrowing

struct S3 {
  S3(std::initializer_list<double>); // #1
  S3(const std::string&); // #2
// ...
};
const S3& r1 = { 1, 2, 3.0 }; // OK: invoke #1
const S3& r2 { "Spinach" }; // OK: invoke #2
S3& r3 = { 1, 2, 3 }; // error: initializer is not an lvalue
const int& i1 = { 1 }; // OK
const int& i2 = { 1.1 }; // error: narrowing
const int (&iar)[2] = { 1, 2 }; // OK: iar is bound to temporary array

enum byte : unsigned char { };
byte b { 42 }; // OK
byte c = { 42 }; // error
byte d = byte{ 42 }; // OK; same value as b
byte e { -1 }; // error
struct A {
  byte b;
};
A a1 = { { 42 } }; // error
A a2 = { byte{ 42 } }; // OK

void f(byte);
f({ 42 }); // error
enum class Handle : uint32_t { Invalid = 0 };
Handle h { 42 }; // OK

int** pp {}; // initialized to null pointer

struct A2 {
  int i;
  int j;
};
A2 a1b { 1, 2 }; // aggregate initialization
A2 a2b { 1.2 }; // error: narrowing
struct B {
  B(std::initializer_list<int>);
};
B b1 { 1, 2 }; // creates initializer_list<int> and calls constructor
B b2 { 1, 2.0 }; // error: narrowing
struct C {
  C(int i, double j);
};
C c1 = { 1, 2.2 }; // calls constructor with arguments (1, 2.2)
C c2 = { 1.1, 2 }; // error: narrowing
int j { 1 }; // initialize to 1
int k { }; // initialize to 0

struct X {
  X(std::initializer_list<double> v);
};
X x{ 1,2,3 };

const double __a[3] = {double{1}, double{2}, double{3}};
X x(std::initializer_list<double>(__a, __a+3));

typedef std::complex<double> cmplx;
std::vector<cmplx> v1 = { 1, 2, 3 };
void f() {
  std::vector<cmplx> v2{ 1, 2, 3 };
  std::initializer_list<int> i3 = { 1, 2, 3 };
}
struct A2 {
  std::initializer_list<int> i4;
  A2() : i4{ 1, 2, 3 } {} // ill-formed, would create a dangling reference
};

int x2 = 999; // x is not a constant expression
const int y = 999;
const int z = 99;
char c1a = x2; // OK, though it might narrow (in this case, it does narrow)
char c2a{x2}; // error: might narrow
char c3{y}; // error: narrows (assuming char is 8 bits)
char c4{z}; // OK: no narrowing needed

unsigned char uc1 = {5}; // OK: no narrowing needed
unsigned char uc2 = {-1}; // error: narrows
unsigned int ui1 = {-1}; // error: narrows
signed int si1 =
{ (unsigned int)-1 }; // error: narrows
int ii = {2.0}; // error: narrows
float f1 { x }; // error: might narrow
float f2 { 7 }; // OK: 7 can be exactly represented as a float
int f(int);
int a[] =
{ 2, f(2), f(2.0) }; // OK: the double-to-int conversion is not at the top level

int main() {

  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p231bs2a
$ clang++ p231bs2a.cpp
p231bs2a.cpp:11:6: error: expected unqualified-id
std::complex<double> z{1,2};
     ^
p231bs2a.cpp:12:1: error: expected unqualified-id
new std::vector<std::string> {"once", "upon", "a", "time"}; // 4 string elements
^
p231bs2a.cpp:13:1: error: C++ requires a type specifier for all declarations
f( {"Nicholas","Annemarie"} ); // pass list of two elements
^
p231bs2a.cpp:14:1: error: expected unqualified-id
return { "Norah" }; // return list of one element
^
p231bs2a.cpp:16:1: error: C++ requires a type specifier for all declarations
x = double{1}; // explicitly construct a double
^
p231bs2a.cpp:20:17: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
int ai[] = { 1, 2.0 }; // error: narrowing
                ^~~
p231bs2a.cpp:20:17: note: insert an explicit cast to silence this issue
int ai[] = { 1, 2.0 }; // error: narrowing
                ^~~
                static_cast<int>( )
p231bs2a.cpp:26:10: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
S2 s22 { 1.0, 2, 3 }; // error: narrowing
         ^~~
p231bs2a.cpp:26:10: note: insert an explicit cast to silence this issue
S2 s22 { 1.0, 2, 3 }; // error: narrowing
         ^~~
         static_cast<int>( )
p231bs2a.cpp:44:8: error: redefinition of 'S2'
struct S2 {
       ^
p231bs2a.cpp:21:8: note: previous definition is here
struct S2 {
       ^
p231bs2a.cpp:52:10: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
S2 s2b { 1.0, 2, 3 }; // error: narrowing
         ^~~
p231bs2a.cpp:52:10: note: insert an explicit cast to silence this issue
S2 s2b { 1.0, 2, 3 }; // error: narrowing
         ^~~
         static_cast<int>( )
p231bs2a.cpp:56:9: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
int x2 {2.0}; // error: narrowing
        ^~~
p231bs2a.cpp:56:9: note: insert an explicit cast to silence this issue
int x2 {2.0}; // error: narrowing
        ^~~
        static_cast<int>( )
p231bs2a.cpp:65:5: error: non-const lvalue reference to type 'S3' cannot bind to an initializer list temporary
S3& r3 = { 1, 2, 3 }; // error: initializer is not an lvalue
    ^    ~~~~~~~~~~~
p231bs2a.cpp:67:19: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
const int& i2 = { 1.1 }; // error: narrowing
                  ^~~
p231bs2a.cpp:67:19: note: insert an explicit cast to silence this issue
const int& i2 = { 1.1 }; // error: narrowing
                  ^~~
                  static_cast<int>( )
p231bs2a.cpp:67:19: warning: implicit conversion from 'double' to 'int' changes value from 1.1 to 1 [-Wliteral-conversion]
const int& i2 = { 1.1 }; // error: narrowing
                ~ ^~~
p231bs2a.cpp:72:12: error: cannot initialize a variable of type 'byte' with an rvalue of type 'int'
byte c = { 42 }; // error
           ^~
p231bs2a.cpp:74:6: error: redefinition of 'e' with a different type: 'byte' vs 'int *'
byte e { -1 }; // error
     ^
p231bs2a.cpp:15:6: note: previous definition is here
int* e {}; // initialization to zero / null pointer
     ^
p231bs2a.cpp:78:12: error: cannot initialize a member subobject of type 'byte' with an rvalue of type 'int'
A a1 = { { 42 } }; // error
           ^~
p231bs2a.cpp:81:6: error: redefinition of 'f' as different kind of symbol
void f(byte);
     ^
p231bs2a.cpp:13:1: note: previous definition is here
f( {"Nicholas","Annemarie"} ); // pass list of two elements
^
p231bs2a.cpp:82:1: error: C++ requires a type specifier for all declarations
f({ 42 }); // error
^
p231bs2a.cpp:93:10: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
A2 a2b { 1.2 }; // error: narrowing
         ^~~
p231bs2a.cpp:93:10: note: insert an explicit cast to silence this issue
A2 a2b { 1.2 }; // error: narrowing
         ^~~
         static_cast<int>( )
p231bs2a.cpp:93:10: warning: implicit conversion from 'double' to 'int' changes value from 1.2 to 1 [-Wliteral-conversion]
A2 a2b { 1.2 }; // error: narrowing
       ~ ^~~
p231bs2a.cpp:98:11: error: type 'double' cannot be narrowed to 'int' in initializer list [-Wc++11-narrowing]
B b2 { 1, 2.0 }; // error: narrowing
          ^~~
p231bs2a.cpp:98:11: note: insert an explicit cast to silence this issue
B b2 { 1, 2.0 }; // error: narrowing
          ^~~
          static_cast<int>( )
fatal error: too many errors emitted, stopping now [-ferror-limit=]
2 warnings and 20 errors generated.

$ g++-7 p231bs2a.cpp
p231bs2a.cpp:8:17: error: expected unqualified-id before '_Complex'
 #define complex _Complex double
                 ^
p231bs2a.cpp:11:6: note: in expansion of macro 'complex'
 std::complex<double> z{1,2};
      ^~~~~~~
p231bs2a.cpp:12:1: error: expected unqualified-id before 'new'
 new std::vector<std::string> {"once", "upon", "a", "time"}; // 4 string elements
 ^~~
p231bs2a.cpp:13:2: error: expected constructor, destructor, or type conversion before '(' token
 f( {"Nicholas","Annemarie"} ); // pass list of two elements
  ^
p231bs2a.cpp:13:29: error: expected unqualified-id before ')' token
 f( {"Nicholas","Annemarie"} ); // pass list of two elements
                             ^
p231bs2a.cpp:14:1: error: expected unqualified-id before 'return'
 return { "Norah" }; // return list of one element
 ^~~~~~
p231bs2a.cpp:16:1: error: 'x' does not name a type
 x = double{1}; // explicitly construct a double
 ^
p231bs2a.cpp:20:21: error: narrowing conversion of '2.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 int ai[] = { 1, 2.0 }; // error: narrowing
                     ^
p231bs2a.cpp:26:20: error: narrowing conversion of '1.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 S2 s22 { 1.0, 2, 3 }; // error: narrowing
                    ^
p231bs2a.cpp:44:8: error: redefinition of 'struct S2'
 struct S2 {
        ^~
p231bs2a.cpp:21:8: note: previous definition of 'struct S2'
 struct S2 {
        ^~
p231bs2a.cpp:52:20: error: narrowing conversion of '1.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 S2 s2b { 1.0, 2, 3 }; // error: narrowing
                    ^
p231bs2a.cpp:56:12: error: narrowing conversion of '2.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 int x2 {2.0}; // error: narrowing
            ^
p231bs2a.cpp:65:20: error: cannot bind non-const lvalue reference of type 'S3&' to an rvalue of type 'S3'
 S3& r3 = { 1, 2, 3 }; // error: initializer is not an lvalue
                    ^
p231bs2a.cpp:59:3: note:   after user-defined conversion: S3::S3(std::initializer_list<double>)
   S3(std::initializer_list<double>); // #1
   ^~
p231bs2a.cpp:67:23: error: narrowing conversion of '1.1000000000000001e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 const int& i2 = { 1.1 }; // error: narrowing
                       ^
p231bs2a.cpp:72:15: error: invalid conversion from 'int' to 'byte' [-fpermissive]
 byte c = { 42 }; // error
               ^
p231bs2a.cpp:74:6: error: conflicting declaration 'byte e'
 byte e { -1 }; // error
      ^
p231bs2a.cpp:15:6: note: previous declaration as 'int* e'
 int* e {}; // initialization to zero / null pointer
      ^
p231bs2a.cpp:78:17: error: braces around scalar initializer for type 'byte'
 A a1 = { { 42 } }; // error
                 ^
p231bs2a.cpp:82:2: error: expected constructor, destructor, or type conversion before '(' token
 f({ 42 }); // error
  ^
p231bs2a.cpp:82:9: error: expected unqualified-id before ')' token
 f({ 42 }); // error
         ^
p231bs2a.cpp:93:14: error: narrowing conversion of '1.2e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 A2 a2b { 1.2 }; // error: narrowing
              ^
p231bs2a.cpp:98:15: error: narrowing conversion of '2.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 B b2 { 1, 2.0 }; // error: narrowing
               ^
p231bs2a.cpp:103:17: error: narrowing conversion of '1.1000000000000001e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 C c2 = { 1.1, 2 }; // error: narrowing
                 ^
p231bs2a.cpp:113:35: error: redefinition of 'X x'
 X x(std::initializer_list<double>(__a, __a+3));
                                   ^~~
p231bs2a.cpp:110:3: note: 'X x' previously declared here
 X x{ 1,2,3 };
   ^
p231bs2a.cpp:113:43: error: invalid conversion from 'const double*' to 'std::initializer_list<double>::size_type {aka long unsigned int}' [-fpermissive]
 X x(std::initializer_list<double>(__a, __a+3));
                                        ~~~^~
In file included from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/range_access.h:36:0,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/string:51,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/locale_classes.h:40,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/ios_base.h:41,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ios:42,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ostream:38,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/iostream:39,
                 from p231bs2a.cpp:5:
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/initializer_list:62:17: note:   initializing argument 2 of 'constexpr std::initializer_list<_E>::initializer_list(std::initializer_list<_E>::const_iterator, std::initializer_list<_E>::size_type) [with _E = double; std::initializer_list<_E>::const_iterator = const double*; std::initializer_list<_E>::size_type = long unsigned int]'
       constexpr initializer_list(const_iterator __a, size_type __l)
                 ^~~~~~~~~~~~~~~~
p231bs2a.cpp:113:45: error: 'constexpr std::initializer_list<_E>::initializer_list(std::initializer_list<_E>::const_iterator, std::initializer_list<_E>::size_type) [with _E = double; std::initializer_list<_E>::const_iterator = const double*; std::initializer_list<_E>::size_type = long unsigned int]' is private within this context
 X x(std::initializer_list<double>(__a, __a+3));
                                             ^
In file included from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/range_access.h:36:0,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/string:51,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/locale_classes.h:40,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/ios_base.h:41,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ios:42,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/ostream:38,
                 from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/iostream:39,
                 from p231bs2a.cpp:5:
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/initializer_list:62:17: note: declared private here
       constexpr initializer_list(const_iterator __a, size_type __l)
                 ^~~~~~~~~~~~~~~~
p231bs2a.cpp:8:17: error: expected unqualified-id before '_Complex'
 #define complex _Complex double
                 ^
p231bs2a.cpp:115:14: note: in expansion of macro 'complex'
 typedef std::complex<double> cmplx;
              ^~~~~~~
p231bs2a.cpp:116:6: error: 'vector' in namespace 'std' does not name a template type
 std::vector<cmplx> v1 = { 1, 2, 3 };
      ^~~~~~
p231bs2a.cpp: In function 'void f()':
p231bs2a.cpp:118:8: error: 'vector' is not a member of 'std'
   std::vector<cmplx> v2{ 1, 2, 3 };
        ^~~~~~
p231bs2a.cpp:118:15: error: 'cmplx' was not declared in this scope
   std::vector<cmplx> v2{ 1, 2, 3 };
               ^~~~~
p231bs2a.cpp:118:15: note: suggested alternative: 'complex'
   std::vector<cmplx> v2{ 1, 2, 3 };
               ^~~~~
               complex
p231bs2a.cpp:118:22: error: 'v2' was not declared in this scope
   std::vector<cmplx> v2{ 1, 2, 3 };
                      ^~
p231bs2a.cpp:118:22: note: suggested alternative: 'c2'
   std::vector<cmplx> v2{ 1, 2, 3 };
                      ^~
                      c2
p231bs2a.cpp: At global scope:
p231bs2a.cpp:121:8: error: redefinition of 'struct A2'
 struct A2 {
        ^~
p231bs2a.cpp:88:8: note: previous definition of 'struct A2'
 struct A2 {
        ^~
p231bs2a.cpp:126:5: error: redefinition of 'int x2'
 int x2 = 999; // x is not a constant expression
     ^~
p231bs2a.cpp:56:5: note: 'int x2' previously defined here
 int x2 {2.0}; // error: narrowing
     ^~
p231bs2a.cpp:130:12: warning: narrowing conversion of 'x2' from 'int' to 'char' inside { } [-Wnarrowing]
 char c2a{x2}; // error: might narrow
            ^
p231bs2a.cpp:131:10: error: narrowing conversion of '999' from 'int' to 'char' inside { } [-Wnarrowing]
 char c3{y}; // error: narrows (assuming char is 8 bits)
          ^
p231bs2a.cpp:135:24: error: narrowing conversion of '-1' from 'int' to 'unsigned char' inside { } [-Wnarrowing]
 unsigned char uc2 = {-1}; // error: narrows
                        ^
p231bs2a.cpp:136:23: error: narrowing conversion of '-1' from 'int' to 'unsigned int' inside { } [-Wnarrowing]
 unsigned int ui1 = {-1}; // error: narrows
                       ^
p231bs2a.cpp:138:20: error: narrowing conversion of '4294967295' from 'unsigned int' to 'int' inside { } [-Wnarrowing]
 { (unsigned int)-1 }; // error: narrows
                    ^
p231bs2a.cpp:139:14: error: narrowing conversion of '2.0e+0' from 'double' to 'int' inside { } [-Wnarrowing]
 int ii = {2.0}; // error: narrows
              ^
p231bs2a.cpp:140:14: error: cannot convert 'X' to 'float' in initialization
 float f1 { x }; // error: might narrow
              ^
p231bs2a.cpp:143:7: error: conflicting declaration 'int a []'
 int a[] =
       ^
p231bs2a.cpp:10:5: note: previous declaration as 'int a'
 int a = {1};
     ^