error with no matching copy constructor

I am getting the following errors when compiling this using g++ 5.7 and when I remove the explicit deceleration it compiles with no warning. but I would like to know why.

compile error message:

move_semantics.cpp: In function ‘MyString hello_world_return_copy()’:
move_semantics.cpp:44:9: error: no matching function for call to ‘MyString::MyString(MyString&)’
  return s;
         ^
move_semantics.cpp: In function ‘MyString hello_world_return_move()’:
move_semantics.cpp:51:20: error: no matching function for call to ‘MyString::MyString(std::remove_reference<MyString&>::type)’
  return std::move(s);
                    ^
move_semantics.cpp: In function ‘MyString hello_world_return_statc()’:
move_semantics.cpp:57:33: error: no matching function for call to ‘MyString::MyString(MyString&)’
  return static_cast<MyString&>(s);
                                 ^
move_semantics.cpp: In function ‘int main()’:
move_semantics.cpp:67:42: error: no matching function for call to ‘MyString::MyString(MyString)’
  MyString temp = hello_world_return_copy();

source:

#include <string>
#include <iostream>

struct MyString {

    explicit MyString(const char* input) {
        std::cout << "Constructor called" << std::endl;
        _str = std::string(input);
    }

    explicit MyString(const MyString& other) {
        std::cout << "Copy constructor called" << std::endl;
        _str = other._str;
    }

    explicit MyString(MyString& other) {
        std::cout << "Copy constructor called" << std::endl;
        _str = other._str;
    }

    ~MyString() {
        std::cout << "destructor called" << std::endl;
    }   

private:
    std::string _str;
};

MyString hello_world_return_copy()
{
    MyString s("hello world!");
    return s;
}

MyString hello_world_return_move()
{
    MyString s("hello world!");
    // move takes an lvalue as argument and returns an rvalue
    return std::move(s);
}

int main() {
    MyString temp = hello_world_return_copy();
}

I am trying to experiment and learn more about move semantics, rvalues and etc. The weird thing is the compiler complains about not having a MyString::MyString(MyString&) function though I do have one.