[Bug c++/55101] New: Invalid implicit conversion in initialization when source type is a template argument type

["cassio.neri at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55101

             Bug #: 55101
           Summary: Invalid implicit conversion in initialization when
                    source type is a template argument type
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: cassio.neri@gmail.com


Calling f(b) below implies an implicit call to an explicit conversion operator.
This is fine with for gcc 4.8.0 but illegal for clang 3.1 and 3.2 (trunk).
Notice that gcc complains (as it should) in other similar circumstances.

struct A { };

struct B {
  explicit operator int() const { return 1; }
  explicit operator A() const { return A(); }
};

template <typename T> void f(T b) { int x = b; }
template <typename T> void g(T b) {   A y = b; }

int main() {

  B b;

  //int x = b; // Error: cannot convert 'B' to 'int' in initialization
  f(b);        // OK for gcc 4.8.0, despite that 'int x = b;' occurs inside f
               // Error for clang 3.1 and 3.2.

  //A y = b;   // Error: conversion from 'B' to non-scalar type 'A' requested
  //g(b);      // Error: conversion from 'B' to non-scalar type 'A' requested
}