E>А что, std::vector<const int> уже запрещён?..

#include <vector>
using namespace std;

vector<const int> v;

fay>>std::complex<double> clVar( 3.0, -1.0 );
I>

I>    std::complex<double> x(y);
I>

I>    std::complex<double> x = y;
I>

std::complex<double> x( 3.0, -1.0 );

std::complex<double> x = y;

fay>>Специально глянул в исходники — как пальцы стали, так и написал

fay>>std::wstring strSQL( L"select IDW,WNAME "
fay>>                     L"from WAREHOUSE "
fay>>                     L"where OWNER=[:owner]" );
fay>>std::wstring strOwner;
fay>>if( bla...bla )
fay>>   strOwner = L"admin";
fay>>else
fay>>   strOwner = L"user";
I>

std::wstring strOwner( ((bal..bla) ? L"admin" : L"user") );

fay>std::wstring strOwner( ((bal..bla) ? L"admin" : L"user") );

fay>Но мне эта запись глаза режет.

std::wstring strOwner = (bal..bla) ? L"admin" : L"user";

    string s = "abcd";

void f(char const* p)
{
    string s = p;
}

I>    string s = "abcd";
I>

I>void f(char const* p)
I>{
I>    string s = p;
I>}
I>

string s = string( x, y, z );

string s = string( x, y, z );

    string s = string( "abcd" );

I>для единообразия.

double x = double( 5 );

fay>>std::wstring strOwner( ((bal..bla) ? L"admin" : L"user") );
I>

fay>>Но мне эта запись глаза режет.

I>std::wstring strOwner = (bal..bla) ? L"admin" : L"user";
I>

int main( int argc, char **, char ** ) {
   std::wstring str1;
   if( argc )
      str1 = L"123";   
   else
      str1 = L"456";   

   std::wcout << str1 << std::endl;

   std::wstring str2 = (argc) ? L"678"
                              : L"012";   

   std::wcout << str2 << std::endl;

   return 0;
}

; 231  :    if( argc )
   mov   edi, DWORD PTR _argc$[esp+84]
   mov   DWORD PTR __$EHRec$[esp+96], ebx

; 232  :       str1 = L"123";   
   push  3
   lea   ecx, DWORD PTR _str1$[esp+92]
   cmp   edi, ebx
   je SHORT $LN2@main
   push  OFFSET $SG155640

; 233  :    else
   jmp   SHORT $LN160@main
$LN2@main:

; 234  :       str1 = L"456";   
   push  OFFSET $SG155642
$LN160@main:
   call  ?assign@?$basic_string@_WU?$char_traits@_W@std@@V?$allocator@_W@2@@std@@QAEAAV12@PB_WI@Z ; std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> >::assign

; 237  : 
; 238  :    std::wstring str2 = (argc) ? L"678"
; 239  :                               : L"012";   
   mov   edx, OFFSET $SG155682
   cmp   edi, ebx
   jne   SHORT $LN6@main
   mov   edx, OFFSET $SG155683
$LN6@main:
   xor   eax, eax
   mov   WORD PTR _str2$[esp+92], ax
   mov   eax, edx
   mov   DWORD PTR _str2$[esp+112], 7
   mov   DWORD PTR _str2$[esp+108], ebx
   lea   esi, DWORD PTR [eax+2]
$LL157@main:
   mov   cx, WORD PTR [eax]
   add   eax, 2
   cmp   cx, bx
   jne   SHORT $LL157@main
   sub   eax, esi
   sar   eax, 1
   push  eax
   push  edx
   lea   ecx, DWORD PTR _str2$[esp+96]
   call  ?assign@?$basic_string@_WU?$char_traits@_W@std@@V?$allocator@_W@2@@std@@QAEAAV12@PB_WI@Z ; std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> >::assign

    vector<int> a = 10;

#include <iostream>

struct X
{
    X(X const *)
        { std::cout << "X(X const *)" << std::endl; }
    X(X &)
        { std::cout << "X(X &)" << std::endl; }
    operator X const *() const
        { std::cout << "X::operator X const *()"; return this; }
    ~X()
        {}
};

int main()
{
    X x(X(0));
}

X x(X(0));

X x = 0;

However, when considering the argument of a user-defined conversion function that is a candidate by 13.3.1.3 when invoked for the copying of the temporary in the second step of a class copy-initialization, or by 13.3.1.4, 13.3.1.5, or 13.3.1.6 in all cases, only standard conversion sequences and ellipsis conversion sequences are allowed.