c++14 - error: conversion from ‘char’ to non-scalar type ‘std::string {aka std::basic_string}’ in C++

Question

#include <iostream>
using namespace std;

int main() {
    string str;
    cin >> str;
    string str1 = str[0];        // statement1

    str1 = str[0];               // statement2
    cout << str1 << endl;
}

Statement1 shows an error while statement2 runs fine. Could anyone please explain why this happens?

Answer 1

Statement 1 is attempting to use a constructor of std::string to initialize str1 (even though you are using an = it still calls a constructor), however there is no constructor that makes a std::string from a single character. Statement 2 on the other hand is calling std::string::operator=() of which a suitable overload for a single character exists.