why implicit conversion is harmful in C++

Question

I understand that the keyword explicit can be used to prevent implicit conversion.

For example

Foo {

 public:
 explicit Foo(int i) {}
}
         


        

Answer 1

It introduces unexpected temporaries:

struct Bar
{
    Bar();      // default constructor
    Bar( int ); // value constructor with implicit conversion
};

void func( const Bar& );

Bar b;
b = 1; // expands to b.operator=( Bar( 1 ));
func( 10 ); // expands to func( Bar( 10 ));