shared_ptr assignment notation implicit conversion

Question

considering following code , Why I can’t use the assignment notation here , Why that is considered to be an implicit conversion.

shared_ptr<string> pNico = new string("nico"); // ERROR implicit conversion
shared_ptr<string> pNico{new string("nico")};   // OK

Answer 1

The constructor is explicit to prevent somebody from doing something like this:

void foo(std::shared_ptr<std::string> s) { }

int main()
{
   std::string s;
   foo(&s);
}

If it was implicit, the shared_ptr could take ownership of a stack allocated variable and try to delete it..which wouldn't make sense.